ThermoplasticFrom Wikipedia, the free encyclopedia

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A thermoplastic, or thermosoftening plastic, is a plastic material, polymer, that becomes pliable or moldable above a specific temperature and solidifies upon cooling.[1][2]

Most thermoplastics have a high molecular weight. The polymer chains associate through intermolecular forces, which weaken rapidly with increased temperature, yielding a viscous liquid. Thus, thermoplastics may be reshaped by heating and are typically used to produce parts by various polymer processing techniques such as injection molding, compression molding, calendering, and extrusion.[3] [4] Thermoplastics differ from thermosetting polymers, which form irreversible chemical bonds during the curing process. Thermosets do not melt, but decompose and do not reform upon cooling.

Stress strain graph of thermoplastic material

Above its glass transition temperature, Tg, and below its melting point, Tm, the physical properties of a thermoplastic change drastically without an associated phase change.

Some thermoplastics do not fully crystallize below the glass transition temperature Tg, retaining some or all of their amorphous characteristics. Amorphous and semi-amorphous plastics are used when high optical clarity is necessary, as light is scattered strongly by crystallites larger than its wavelength. Amorphous and semi-amorphous plastics are less resistant to chemical attack and environmental stress cracking because they lack a crystalline structure.

Brittleness can be decreased with the addition of plasticizers, which increases the mobility of amorphous chain segments to effectively lower Tg. Modification of the polymer through copolymerization or through the addition of non-reactive side chains to monomers before polymerization can also lower Tg. Before these techniques were employed, plastic automobileparts would often crack when exposed to cold temperatures.

Contents

1 Acrylic

2 ABS

3 Nylon

4 PLA

5 Polybenzimidazole

6 Polycarbonate

7 Polyether sulfone

8 Polyetherether ketone

9 Polyetherimide

10 Polyethylene

11 Polyphenylene oxide

12 Polyphenylene sulfide

13 Polypropylene

14 Polystyrene

15 Polyvinyl chloride

16 Teflon

17 References

Acrylic

Acrylic, a polymer called poly(methyl methacrylat)

ABS

Acrylonitrile butadiene styrene (ABS) is a terpolymer synthesized from styrene and acrylonitrile in the presence of polybutadiene. ABS is a light-weight material that exhibits high impact resistance and mechanical toughness. It poses few risks to human health under normal handling. It is used in many consumer products, such as toys, appliances, and telephones.

Nylon

Nylon belongs to a class of polymers called polyamides. It has served as a substitute for silk in products such as parachutes, flak vests and women's stockings. Nylon fibers are useful in making fabrics, rope, carpets and musical strings, whereas in bulk form, nylon is used for mechanical parts including machine screws, gear wheels and power tool casings. In addition, nylon is used in the manufacture of heat-resistant composite materials.

PLA

Polylactic acid (polylactide) is a biodegradable thermoplastic aliphatic polyester derived fromrenewable resources, such as corn starch (in the United States), tapioca roots, chips or starch (mostly in Asia), or sugarcane. It is one of the materials used for 3D printing with fused deposition modeling (FDM) techniques.

Polybenzimidazole

Polybenzimidazole(PBI,short for Poly-[2,2’-(m-phenylen)-5,5’-bisbenzimidazole]) fiber is a synthetic fiber with a very high melting point. It has exceptional thermal and chemical stability and does not readily ignite. It was first discovered by American polymer chemist Carl Shipp Marvel in the pursuit of new materials with superior stability, retention of stiffness, toughness at elevated temperature. Due to its high stability, Polybenzimidazole is used to fabricate high-performance protective apparel such as firefighter’s gear, astronaut space suits, high temperature protective gloves, welders’ apparel and aircraft wall fabrics. In recent years, polybenzimidazole found its application as membrane in fuel cells.

Polycarbonate

Polycarbonate (PC) thermoplastics are known under trademarks such as Lexan, Makrolon, Makroclear, and arcoPlus. They are easily worked, molded, and thermoformed for many applications, such as electronic components, construction materials, data storage devices, automotive and aircraft parts, and security glazing. Polycarbonates do not have a unique resinidentification code. Items made from polycarbonate can contain the precursor monomer bisphenol A (BPA).

Polyether sulfone

Polyether sulfone (PES) is a class of specially engineered thermoplastics[5] with high thermal,oxidative, and hydrolytic stability, and good resistance to aqueous mineral acids, alkalis, salt solutions, oils and greases.

Polyetherether ketone

Poly ether ether ketone (PEEK) has attractive properties like good abrasion resistance, low flammability and emission of smoke and toxic gases, resistance to radiation and high temperature steam, and low water absorption.

Polyetherimide

Polyetherimide (PEI), produced by a novel nitro displacement reaction involving bisphenol A, 4, 4’-methylenedianiline and 3-nitrophthalic anhydride, has high heat distortion temperature, tensile strength and modulus. They are generally used in high performance electrical and electronic parts, microwave appliances, and under-the-hood automotive parts.

Polyethylene

Polyethylene (polyethene, polythene, PE) is a family of similar materials categorized according to their density and molecular structure. For example:

Ultra-high molecular weight polyethylene (UHMWPE) is tough and resistant to chemicals. It is used to manufacture moving machine parts, bearings, gears, artificial joints and some bulletproof vests.

High-density polyethylene (HDPE), recyclable plastic no. 2, is commonly used as milk jugs, liquid laundry detergent bottles, outdoor furniture, margarine tubs, portable gasoline cans, water drainage pipes, and grocery bags.

Medium-density polyethylene (MDPE) is used for packaging film, sacks and gas pipes and fittings.

Low-density polyethylene (LDPE) is flexible and is used in the manufacture of squeeze bottles, milk jug caps, retail store bags and linear low-density polyethylene (LLDPE) as stretch wrap in transporting and handling boxes of durable goods, and as the common household food covering.

XLPE or "PEX" (cross-linked polyethylene) is a semi-rigid, flexible material which has gained wide use in cold or hot water building heating and cooling applications (hydronic heating and cooling) due to its exceptional resistance to breakdown from wide temperature variations.

Polyphenylene oxide

Polyphenylene oxide (PPO), which is obtained from the free-radical, step-growth oxidative coupling polymerization of 2,6-xylenol, has many attractive properties such as high heat distortion and impact strength, chemical stability to mineral and organic acids, and low water absorption. PPO is difficult to process, and hence the commercial resin (Noryl) is made by blending PPO with high-impact polystyrene (HIPS) which serves to reduce the processing temperature.

Polyphenylene sulfide

Polyphenylene sulfide (PPS) obtained by the condensation polymerization of p-dichlorobenzene and sodium sulfide, has outstanding chemical resistance, good electrical properties, excellent flame retardance, low coefficient of friction and high transparency to microwave radiation. PPS is principally used in coating applications. This is done by spraying an aqueous slurry of PPS particles and heating to temperatures above 370°C. Particular grades of PPS can be used in injection and compression molding at temperatures

(300 to 370°C) at which PPS particles soften and undergo apparent crosslinking. Principal applications of injection and compression molded PPS include cookware, bearings, and pumpparts for service in various corrosive environments.

Polypropylene

Polypropylene (PP) is useful for such diverse products as reusable plastic food containers, microwave- and dishwasher-safe plastic containers, diaper lining, sanitary pad lining and casing, ropes, carpets, plastic moldings, piping systems, car batteries, insulation for electrical cables and filters for gases and liquids. In medicine, it is used in hernia treatment and to makeheat-resistant medical equipment. Polypropylene sheets are used for stationery folders and packaging and clear storage bins. Polypropylene is defined by the recyclable plastic number 5. Although relatively inert, it is vulnerable to ultraviolet radiation and can degrade considerably in direct sunlight. Polypropylene is not as impact-resistant as the polyethylenes (HDPE, LDPE). It is also somewhat permeable to highly volatile gases and liquids.

Polystyrene

Polystyrene is manufactured in various forms that have different applications. Extruded polystyrene (PS) is used in the manufacture of disposable cutlery, CD and DVD cases, plasticmodels of cars and boats, and smoke detector housings. Expanded polystyrene foam (EPS) is used in making insulation and packaging materials, such as the "peanuts" and molded foam used to cushion fragile products. Extruded polystyrene foam (XPS), known by the trade nameStyrofoam, is used to make architectural models and drinking cups for heated beverages. Polystyrene copolymers are used in the manufacture of toys and product casings.

Polyvinyl chloride

Polyvinyl chloride (PVC) is a tough, lightweight material that is resistant to acids and bases. Much of it is used by the construction industry, such as for vinyl siding, drainpipes, gutters and roofing sheets. It is also converted to flexible forms with the addition of plasticizers, thereby making it useful for items such as hoses, tubing, electrical insulation, coats, jackets and upholstery. Flexible PVC is also used in inflatable products, such as water beds and pool toys.

Teflon

Teflon is a brand name of DuPont for a variety of the polymer polytetrafluoroethylene (PTFE), which belongs to a class of thermoplastics known as fluoropolymers. It is known as a coating for non-stick cookware. Being chemically inert, it is used in making containers and pipes that come in contact with reactive compounds. It is also used as a lubricant to reduce wear from friction between sliding parts, such as gears, bearings, and bushings.

References

1.

http://www.lgschemistry.org.uk/PDF/Thermosoftening_and_thermosetting_plastics.pdf Baeurle SA, Hotta A, Gusev AA (2006). "On the glassy state of multiphase and pure

polymer materials". Polymer 47: 6243–6253. doi:10.1016/j.polymer.2006.05.076. A. V. Shenoy and D. R. Saini (1996), Thermoplastic Melt Rheology and Processing ,

Marcel Dekker Inc., New York. Charles P. MacDermott and Aroon V. Shenoy (1997), Selecting Thermoplastics for

Engineering Applications , Marcel Dekker Inc., New York.

1. D. R. Saini and A. V. Shenoy (1985), Melt rheology of some specialty polymers , J. Elastomers Plastics, Vol. 17, pp. 189-217.

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PolypropyleneFrom Wikipedia, the free encyclopedia

Polypropylene

Names

IUPAC name poly(propene)

Other names Polypropylene; Polypropene;Polipropene 25 [USAN];Propene polymers;Propylene polymers; 1-Propene

Identifiers

CAS Registry Number

9003-07-0

ChemSpider

Properties

Chemical formula (C3H6)n

Density

0.855 g/cm3, amorphous

0.946 g/cm3, crystalline

Melting point130 to 171 °C (266 to 340 °F; 403 to 444 K)

Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

verify (what is: / ?)Infobox references

Polypropylene (PP), also known as polypropene, is a thermoplastic polymer used in a wide variety of applications including packaging and labeling, textiles (e.g., ropes, thermal underwear and carpets), stationery, plastic parts and reusable containers of various types, laboratory equipment, loudspeakers, automotive components, and polymer banknotes. An addition polymer made from the monomer propylene, it is rugged and unusually resistant to many chemical solvents, bases and acids.

In 2013, the global market for polypropylene was about 55 million metric tons.[1]

Contents

1 Chemical and physical properties

o 1.1 Degradation

2 History

3 Synthesis

4 Industrial processes

5 Manufacturing

6 Biaxially oriented polypropylene (BOPP)

7 Development trends

8 Applications

o 8.1 Clothing

o 8.2 Medical

o 8.3 EPP model aircraft

9 Recycling

10 Repairing

11 Health concerns

12 References

13 External links

Chemical and physical properties

Micrograph of polypropylene

Most commercial polypropylene is isotactic and has an intermediate level of crystallinity between that of low-density polyethylene (LDPE) and high-density polyethylene (HDPE). Polypropylene is normally tough and flexible, especially when copolymerized with ethylene. This allows polypropylene to be used as an engineering plastic, competing with materials

such as acrylonitrile butadiene styrene (ABS). Polypropylene is reasonably economical, and can be made translucent when uncolored but is not as readily made transparent as polystyrene, acrylic, or certain other plastics. It is often opaque or colored using pigments. Polypropylene has good resistance to fatigue. The melting point of polypropylene occurs at a range, so a melting point is determined by finding the highest temperature of a differential scanning calorimetry chart. Perfectly isotactic PP has a melting point of 171 °C (340 °F). Commercial isotactic PP has a melting point that ranges from 160 to 166 °C (320 to 331 °F), depending on atactic material and crystallinity. Syndiotactic PP with a crystallinity of 30% has a melting point of 130 °C (266 °F).[2] The melt flow rate (MFR) or melt flow index (MFI)is a measure of molecular weight of polypropylene. The measure helps to determine how easily the molten raw material will flow during processing. Polypropylene with higher MFR will fill the plastic mold more easily during the injection or blow-molding production process. As the melt flow increases, however, some physical properties, like impact strength, will decrease. There are three general types of polypropylene: homopolymer, random copolymer, and block copolymer. The comonomer is typically used with ethylene. Ethylene-propylene rubber or EPDM added to polypropylene homopolymer increases its low temperature impact strength. Randomly polymerized ethylene monomer added to polypropylene homopolymer decreases the polymer crystallinity, lowers the melting point and makes the polymer more transparent.

Degradation

Polypropylene is liable to chain degradation from exposure to heat and UV radiation such as that present in sunlight. Oxidation usually occurs at the tertiary carbon atom present in every repeat unit. A free radical is formed here, and then reacts further with oxygen, followed by chain scission to yield aldehydes and carboxylic acids. In external applications, it shows up asa network of fine cracks and crazes that become deeper and more severe with time of exposure. For external applications, UV-absorbing additives must be used. Carbon black also provides some protection from UV attack. The polymer can also be oxidized at high temperatures, a common problem during molding operations. Anti-oxidants are normally added to prevent polymer degradation. Microbial communities isolated from soil samples mixed with starch have been shown to be capable of degrading polypropylene.[3]

History

Phillips Petroleum chemists J. Paul Hogan and Robert L. Banks first polymerized propylene in 1951.[4] Propylene was first polymerized to a crystalline isotactic polymer by Giulio Natta as well as by the German chemist Karl Rehn in March 1954.[5] This pioneering discovery led to large-scale commercial production of isotactic polypropylene by the Italian firm Montecatini from 1957 onwards.[6] Syndiotactic polypropylene was also first synthesized by Natta and his coworkers.

Polypropylene is the second most important plastic with revenues expected to exceed US$145 billion by 2019. The sales of this material are forecast to grow at a rate of 5.8% per year until 2021.[1]

Synthesis

This section provides insufficient context for those unfamiliar with the subject. Please help improve the article with a good introductory style. (June 2012)

Short segments of polypropylene, showing examples of isotactic (above) and syndiotactic (below) tacticity.

An important concept in understanding the link between the structure of polypropylene and its properties is tacticity. The relative orientation of each methyl group (CH3 in the figure) relative to the methyl groups in neighboring monomer units has a strong effecton the polymer's ability to form crystals.

A Ziegler-Natta catalyst is able to restrict linking of monomer molecules to a specific regular orientation, either isotactic, when all methyl groups are positioned at the same side with respect to the backbone of the polymer chain, or syndiotactic, when the positions of the methyl groups alternate. Commercially available isotactic polypropylene is made with two types of Ziegler-Natta catalysts. The first group of the catalysts encompasses solid (mostly supported) catalysts and certain types of soluble metallocene catalysts. Such isotactic macromolecules coil into a helical shape; these helices then line up next to one another to form the crystals that give commercial isotactic polypropylene many of its desirable properties.

A ball-and-stick model of syndiotactic polypropylene.

Another type of metallocene catalysts produce syndiotactic polypropylene. These macromolecules also coil into helices (of a different type) and form crystalline materials.

When the methyl groups in a polypropylene chain exhibit no preferred orientation, the polymers are called atactic. Atactic polypropylene is an amorphous rubbery material. It can be produced commercially either with a special type of supported Ziegler-Natta catalyst or with some metallocene catalysts.

Modern supported Ziegler-Natta catalysts developed for the polymerization of propylene and other 1-alkenes to isotactic polymers usually use TiCl4 as an active ingredient and MgCl2 as a support.[7][8][9] The catalysts also contain organic modifiers, either aromatic acid esters and diesters or ethers. These catalysts are activated with special cocatalysts containing an organoaluminum compound such as Al(C2H5)3 and the second type of a modifier. The catalysts are differentiated depending on the procedure used for fashioning catalyst particles from MgCl2 and depending on the type of organic modifiers employed during catalyst preparation and use in polymerization reactions. Two most important technological characteristics of all the supported catalysts are high productivity and a high fraction of the crystalline isotactic polymer they produce at 70–80 °C under standard polymerization conditions. Commercial synthesis of isotactic polypropylene is usually carried out either in the medium of liquid propylene or in gas-phase reactors.

Commercial synthesis of syndiotactic polypropylene is carried out with the use of a special class of metallocene catalysts. They employ bridged bis-metallocene complexes of the type bridge-(Cp1)(Cp2)ZrCl2 where the first Cp ligand is the cyclopentadienyl group, the second Cp ligand is the fluorenyl group, and the bridge between the two Cp ligands is -CH2-CH2-, >SiMe2, or >SiPh2.[10] These complexes are converted to polymerization catalysts by activating them with a special organoaluminum cocatalyst, methylaluminoxane (MAO).[11]

Industrial processes

Traditionally, three manufacturing processes are the most representative ways to produce polypropylene.[12]

Hydrocarbon slurry or suspension: Uses a liquid inert hydrocarbon diluent in the reactor to facilitate transfer of propylene to the catalyst, the removal of heat from the system, the deactivation/removal of the catalyst as well as dissolving the atactic polymer. The range of grades that could be produced was very limited. (The technology has fallen into disuse).

Bulk (or bulk slurry): Uses liquid propylene instead of liquid inert hydrocarbon diluent. The polymer does not dissolve into a diluent, but rather rides on the liquid propylene. The formed polymer is withdrawn and any unreacted monomer is flashed off.

Gas phase: Uses gaseous propylene in contact with the solid catalyst, resulting in a fluidized-bed medium.

Manufacturing

Melt processing of polypropylene can be achieved via extrusion and molding. Common extrusion methods include production of melt-blown and spun-bond fibers to form long rolls for future conversion into a wide range of useful products, such as face masks, filters, diapersand wipes.

The most common shaping technique is injection molding, which is used for parts such as cups, cutlery, vials, caps, containers, housewares, and automotive parts such as batteries. The related techniques of blow molding and injection-stretch blow molding are also used, which involve both extrusion and molding.

The large number of end-use applications for polypropylene are often possible because of the ability to tailor grades with specific molecular properties and additives during its manufacture. For example, antistatic additives can be added to help polypropylene surfaces resist dust and dirt. Many physical finishing techniques can also be used on polypropylene, such as machining. Surface treatments can be applied to polypropylene parts in order to promote adhesion of printing ink and paints.

Biaxially oriented polypropylene (BOPP)

When polypropylene film is extruded and stretched in both the machine direction and across machine direction it is called biaxially oriented polypropylene. Biaxial orientation increases strength and clarity.[13] BOPP is widely used as a packaging material for packaging products such as snack foods, fresh produce and confectionery. It is easy to coat, print and laminate to give the required appearance and properties for use as a packaging material. This process is normally called converting. It is normally produced in large rolls which are slit on slitting machines into smaller rolls for use on packaging machines.

Development trends

With the increase in the level of performance required for polypropylene quality in recent years, a variety of ideas and contrivances have been integrated into the production process forpolypropylene.[14]

There are roughly two directions for the specific methods. One is improvement of uniformity of the polymer particles produced using a circulation type reactor, and the other is improvement in the uniformity among polymer particles produced by using a reactor with a narrow retention time distribution.

Applications

Polypropylene lid of a Tic Tacs box, with a living hinge and the resin identification code under its flap

As polypropylene is resistant to fatigue, most plastic living hinges, such as those on flip-top bottles, are made from this material. However, it is important to ensure that chain molecules are oriented across the hinge to maximise strength.

Very thin sheets (~2-20 µm) of polypropylene are used as a dielectric within certain high-performance pulse and low-loss RF capacitors.

Polypropylene is used in the manufacturing piping systems; both ones concerned with high-purity and ones designed for strength and rigidity (e.g. those intended for use in potable plumbing, hydronic heating and cooling, and reclaimed water).[15] This material is often chosen for its resistance to corrosion and chemical leaching, its resilience against most forms of physical damage, including impact and freezing, its environmental benefits, and its ability to be joined by heat fusion rather than gluing.[16][17][18]

A polypropylene chair

Many plastic items for medical or laboratory use can be made from polypropylene because it can withstand the heat in an autoclave. Its heat resistance also enables it to be used as the manufacturing material of consumer-grade kettles[citation needed]. Food containers made from it will not melt in the dishwasher, and do not melt during industrial hot filling processes. For this reason, most plastic tubs for dairy products are polypropylene sealed with aluminum foil (both heat-resistant materials). After the product has cooled, the tubs are often given lids made of a less heat-resistant material, such as LDPE or polystyrene. Such containers provide a good hands-on example of the difference in modulus, since the rubbery (softer, more flexible) feeling of LDPE with respect to polypropylene of the same thickness is readily apparent. Rugged, translucent, reusable plastic containers made in a wide variety of shapes and sizes for consumers from various companies such as Rubbermaid and Sterilite are commonly made of polypropylene, although the lids are often made of somewhat more flexible LDPE so they can snap on to the container to close it. Polypropylene can also be made into disposable bottles to contain liquid, powdered, or similar consumer products, although HDPE and polyethylene terephthalate are commonly also used to make bottles. Plastic pails, car batteries, wastebaskets, pharmacy prescription bottles, cooler containers, dishes and pitchers are often made of polypropylene or HDPE, both of which commonly haverather similar appearance, feel, and properties at ambient temperature.

Polypropylene items for laboratory use, blue and orange closures are not made of polypropylene.

A common application for polypropylene is as biaxially oriented polypropylene (BOPP). These BOPP sheets are used to make a wide variety of materials including clear bags. When polypropylene is biaxially oriented, it becomes crystal clear and serves as an excellent packaging material for artistic and retail products.

Polypropylene, highly colorfast, is widely used in manufacturing carpets, rugs and mats to be used at home.[19]

Polypropylene is widely used in ropes, distinctive because they are light enough to float in water.[20] For equal mass and construction, polypropylene rope is similar in strength to polyester rope. Polypropylene costs less than most other synthetic fibers.

Polypropylene is also used as an alternative to polyvinyl chloride (PVC) as insulation for electrical cables for LSZH cable in low-ventilation environments, primarily tunnels. This is because it emits less smoke and no toxic halogens, which may lead to production of acid in high-temperature conditions.

Polypropylene is also used in particular roofing membranes as the waterproofing top layer of single-ply systems as opposed to modified-bit systems.

Polypropylene is most commonly used for plastic moldings, wherein it is injected into a moldwhile molten, forming complex shapes at relatively low cost and high volume; examples include bottle tops, bottles, and fittings.

It can also be produced in sheet form, widely used for the production of stationery folders, packaging, and storage boxes. The wide color range, durability, low cost, and resistance to dirt make it ideal as a protective cover for papers and other materials. It is used in Rubik's Cube stickers because of these characteristics.

The availability of sheet polypropylene has provided an opportunity for the use of the material by designers. The light-weight, durable, and colorful plastic makes an ideal medium for the creation of light shades, and a number of designs have been developed using interlocking sections to create elaborate designs.

Polypropylene sheets are a popular choice for trading card collectors; these come with pockets (nine for standard-size cards) for the cards to be inserted and are used to protect their condition and are meant to be stored in a binder.

Expanded polypropylene (EPP) is a foam form of polypropylene. EPP has very good impact characteristics due to its low stiffness; this allows EPP to resume its shape after impacts. EPP is extensively used in model aircraft and other radio controlled vehicles by hobbyists. This is mainly due to its ability to absorb impacts, making this an ideal material for RC aircraft for beginners and amateurs.

Polypropylene is used in the manufacture of loudspeaker drive units. Its use was pioneered byengineers at the BBC and the patent rights subsequently purchased by Mission Electronics foruse in their Mission Freedom Loudspeaker and Mission 737 Renaissance loudspeaker.

Polypropylene fibres are used as a concrete additive to increase strength and reduce cracking and spalling.[21] In the areas susceptible to earthquake, i.e., California, PP fibers are added with soils to improve the soils strength and damping when constructing the foundation of structures such as buildings, bridges, etc.[22]

Polypropylene is used in polypropylene drums.

Clothing

Polypropylene is a major polymer used in nonwovens, with over 50% used[citation needed] for diapers or sanitary products where it is treated to absorb water (hydrophilic) rather than naturally repelling water (hydrophobic). Other interesting non-woven uses include filters for air, gas, and liquids in which the fibers can be formed into sheets or webs that can be pleated to form cartridges or layers that filter in various efficiencies in the 0.5 to 30 micrometre range. Such applications could be seen in the house as water filters or air-conditioning-type filters. The high surface area and naturally oleophilic polypropylene nonwovens are ideal absorbers of oil spills with the familiar floating barriers near oil spills on rivers.

Polypropylene, or 'polypro', has been used for the fabrication of cold-weather base layers, such as long-sleeve shirts or long underwear. Polypropylene is also used in warm-weather clothing, which transports sweat away from the skin. More recently, polyester has replaced polypropylene in these applications in the U.S. military, such as in the ECWCS.[23] Although polypropylene clothes are not easily flammable, they can melt, which may result in severe burns if the wearer is involved in an explosion or fire of any kind.[24] Polypropylene undergarments are known for retaining body odors which are then difficult to remove. The current generation of polyester does not have this disadvantage.[25]

The material has recently been introduced into the fashion industry through the work of designers such as Anoush Waddington, who have developed specialized techniques to create jewelry and wearable items from polypropylene.

Medical

Its most common medical use is in the synthetic, nonabsorbable suture Prolene, manufacturedby Ethicon Inc.

Polypropylene has been used in hernia and pelvic organ prolapse repair operations to protect the body from new hernias in the same location. A small patch of the material is placed over the spot of the hernia, below the skin, and is painless and rarely, if ever, rejected by the body. However, a polypropylene mesh will erode the tissue surrounding it over the uncertain period

from days to years. Therefore, the FDA has issued several warnings on the use of polypropylene mesh medical kits for certain applications in pelvic organ prolapse, specifically when introduced in close proximity to the vaginal wall due to a continued increase in number of mesh-driven tissue erosions reported by patients over the past few years.[26] Most recently, on 3 January 2012, the FDA ordered 35 manufacturers of these mesh products to study the side effects of these devices.

EPP model aircraft

Since 2001, expanded polypropylene (EPP) foams have been gaining in popularity and in application as a structural material in hobbyist radio control model aircraft. Unlike expanded polystyrene foam (EPS) which is friable and breaks easily on impact, EPP foam is able to absorb kinetic impacts very well without breaking, retains its original shape, and exhibits memory form characteristics which allow it to return to its original shape in a short amount oftime.[27] In consequence, a radio-control model whose wings and fuselage are constructed from EPP foam is extremely resilient, and able to absorb impacts that would result in complete destruction of models made from lighter traditional materials, such as balsa or even EPS foams. EPP models, when covered with inexpensive fibreglass impregnated self-adhesive tapes, often exhibit much increased mechanical strength, in conjunction with a lightness and surface finish that rival those of models of the aforementioned types. EPP is also chemically highly inert, permitting the use of a wide variety of different adhesives. EPP can be heat molded, and surfaces can be easily finished with the use of cutting tools and abrasive papers. The principal areas of model making in which EPP has found great acceptance are the fields of:

Wind-driven slope soarers

Indoor electric powered profile electric models

Hand launched gliders for small children

In the field of slope soaring, EPP has found greatest favour and use, as it permits the construction of radio-controlled model gliders of great strength and maneuverability. In consequence, the disciplines of slope combat (the active process of friendly competitors attempting to knock each other's planes out of the air by direct contact) and slope pylon racing have become commonplace, in direct consequence of the strength characteristics of thematerial EPP.

Recycling

Polypropylene is recyclable and has the number "5" as its resin identification code:[28]

Repairing

Many objects are made with polypropylene precisely because it is resilient and resistant to most solvents and glues. Also, there are very few glues available specifically for gluing PP. However, solid PP objects not subject to undue flexing can be satisfactorily joined with a two

part epoxy glue or using hot-glue guns. Preparation is important and it is often helpful to roughen the surface with a file, emery paper or other abrasive material to provide better anchorage for the glue. Also it is recommended to clean with mineral spirits or similar alcohol prior to gluing to remove any oils or other contamination. Some experimentation maybe required. There are also some industrial glues available for PP, but these can be difficult to find, especially in a retail store.[citation needed]

PP can be melted using a speed welding technique. With speed welding, the plastic welder, similar to a soldering iron in appearance and wattage, is fitted with a feed tube for the plastic weld rod. The speed tip heats the rod and the substrate, while at the same time it presses the molten weld rod into position. A bead of softened plastic is laid into the joint, and the parts and weld rod fuse. With polypropylene, the melted welding rod must be "mixed" with the semi-melted base material being fabricated or repaired. A speed tip "gun" is essentially a soldering iron with a broad, flat tip that can be used to melt the weld joint and filler material to create a bond.

Health concerns

In 2008, researchers in Canada asserted that quaternary ammonium biocides and oleamide were leaking out of certain polypropylene labware, affecting experimental results.[29] As polypropylene is used in a wide number of food containers such as those for yogurt, Health Canada media spokesman Paul Duchesne said the department will be reviewing the findings to determine whether steps are needed to protect consumers.[30]

The Environmental Working Group classifies PP as of low to moderate hazard.[31] PP is dope-dyed, no water is used in its dyeing, in contrast with cotton.[32]

References

1.

"Market Study: Polypropylene (3rd edition)". Ceresana. Maier, Clive; Calafut, Teresa (1998). Polypropylene: the definitive user's guide and

databook. William Andrew. p. 14. ISBN 978-1-884207-58-7. Cacciari, I.; Quatrini, P.; Zirletta, G.; Mincione, E.; Vinciguerra, V.; Lupattelli, P.;

Giovannozzi Sermanni, G. (1993). "Isotactic polypropylene biodegradation by a microbial community: Physicochemical characterization of metabolites produced". Applied and environmental microbiology 59 (11): 3695–3700. PMC 182519. PMID 8285678. edit

Stinson, Stephen (9 March 1987). "Discoverers of Polypropylene Share Prize". Chemical & Engineering News (Volume 65, Number 10) (American Chemical Society). p. 30. doi:10.1021/cen-v065n010.p030.

Morris, Peter J. T. (2005). Polymer Pioneers: A Popular History of the Science and Technology of Large Molecules. Chemical Heritage Foundation. p. 76. ISBN 0-941901-03-3.

This week 50 years ago in New Scientist 28 April 2007, p. 15 Kissin, Y. V. (2008). Alkene Polymerization Reactions with Transition Metal

Catalysts. Elsevier. pp. 207–. ISBN 978-0-444-53215-2. Hoff, Ray and Mathers, Robert T. (2010). Handbook of Transition Metal

Polymerization Catalysts. John Wiley & Sons. pp. 158–. ISBN 978-0-470-13798-7.

Moore, E. P. (1996) Polypropylene Handbook. Polymerization, Characterization, Properties, Processing, Applications, Hanser Publishers: New York, ISBN 1569902089

Benedikt, G. M. and Goodall, B. L. (eds.) (1998) Metallocene Catalyzed Polymers, ChemTech Publishing: Toronto. ISBN 978-1-884207-59-4.

Sinn, H.; Kaminsky, W. and Höker, H. (eds.) (1995) Alumoxanes, Macromol. Symp. 97, Huttig & Wepf: Heidelberg.

"Polypropylene Production via Gas Phase Process, Technology Economics Program". by Intratec, ISBN 978-0-615-66694-5, Q3 2012.

Biaxially Oriented Polypropylene Films. Granwell. Retrieved: 2012-05-31. Sato, Hideki and Ogawa, Hiroyuki (2009) Review on Development of Polypropylene

Manufacturing Process, Sumitomo Kagaku. ASTM Standard F2389, 2007, "Standard Specification for Pressure-rated

Polypropylene (PP) Piping Systems", ASTM International, West Conshohocken, PA, 2007, doi:10.1520/F2389-07E01, www.astm.org.

Green pipe helps miners remove the black Contractor Magazine, 10 January 2010 Contractor Retrofits His Business. the News/ 2 November 2009. What to do when the piping replacement needs a replacement? Engineered Systems. 1

November 2009. Rug fibers. Fibersource.com. Retrieved on 2012-05-31. Braided Polypropylene Rope is Inexpensive and it Floats. contractorrope.com.

Retrieved on 2013-02-28. Bayasi, Ziad and Zeng, Jack (1993). "Properties of Polypropylene Fiber Reinforced".

Materials Journal 90 (6): 605–610. doi:10.14359/4439. Amir-Faryar, Behzad and Aggour, M. Sherif (2015). "Effect of fibre inclusion on

dynamic properties of clay". Geomechanics and Geoengineering: An International Journal: 1–10. doi:10.1080/17486025.2015.1029013.

Generation III Extended Cold Weather Clothing System (ECWCS). PM Soldier Equipment. October 2008

USAF Flying Magazine. Safety. Nov. 2002. access.gpo.gov Ellis, David. Get Real: The true story of performance next to skin fabrics.

outdoorsnz.org.nz FDA Public Health Notification: Serious Complications Associated with Transvaginal

Placement of Surgical Mesh in Repair of Pelvic Organ Prolapse and Stress Urinary Incontinence, FDA, 20 October 2008

Sadighi, Mojtaba; Salami, Sattar Jedari (2012). "An investigation on low-velocity impact response of elastomeric & crushable foams". Central European Journal of Engineering 2 (4): 627–637. Bibcode:2012OEng....2..627S. doi:10.2478/s13531-012-0026-0.

Plastics recycling information sheet, Waste Online Plastic additives leach into medical experiments, research shows, Physorg.com, 10

November 2008 Scientific tests skewed by leaching plastics, November 6, 2008. POLYPROPYLENE || Skin Deep® Cosmetics Database | Environmental Working

Group. Cosmeticdatabase.com. Retrieved on 2012-05-31.

1. Chapagain, A.K. et al. (September 2005) The water footprint of cotton consumption. UNESCO-IHE Delft. Value of Water Research Report Series No. 18. waterfootprint.org

External links

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Poly(p-phenylene oxide)From Wikipedia, the free encyclopedia (Redirected from Polyphenylene oxide)

Poly(p-phenylene oxide) or poly(p-phenylene ether) (PPE) is a high-temperature thermoplastic. It is rarely used in its pure form due to difficulties in processing. It is mainly used as blend with polystyrene, high impact styrene-butadiene copolymer or polyamide. PPO™ is a registered trademark of SABIC Innovative Plastics IP B.V. under which various polyphenylene ether resins are sold.

Contents

1 History

2 Properties

3 Applications

4 Production from natural products

5 References

6 External links

History

Polyphenylene ether was discovered in 1956 by Allan Hay, and was commercialized by General Electric in 1960.

While it was one of the cheapest high-temperature resistant plastics, processing was difficult and the impact and heat resistance decreased with time. Mixing it with polystyrene in any ratio could compensate for the disadvantages. In the 1960s, modified PPE came into the market under the trademark Noryl.[1]

Properties

PPE is an amorphous high-performance plastic. The glass transition temperature is 215 °C, but it can be varied by mixing with polystyrene. Through modification and the incorporation of fillers such as glass fibers, the properties can be extensively modified.

Applications

A printer cartridge made of PPE and polystyrene; it is an example of a product which requiresgood dimensional stability and accuracy to fit

PPE blends are used for structural parts, electronics, household and automotive items that depend on high heat resistance, dimensional stability and accuracy. They are also used in medicine for sterilizable instruments made of plastic.[2]

This plastic is processed by injection molding or extrusion; depending on the type, the processing temperature is 260-300 °C. The surface can be printed, hot-stamped, painted or metallized. Welds are possible by means of heating element, friction or ultrasonic welding. It can be glued with halogenated solvents or various adhesives.

This plastic is also used to produce air separation membranes for generating nitrogen. The PPO is spun into a hollow fiber membrane with a porous support layer and a very thin outer skin. The permeation of oxygen occurs from inside to out across the thin outer skin with an extremely high flux. Due to the manufacturing process, the fiber has excellent dimensional stability and strength. Unlike hollow fiber membranes made from polysulfone, the aging process of the fiber is relatively quick so that air separation performance remains stable throughout the life of the membrane. PPO makes the air separation performance suitable for low temperature (35-70F)(2-21C) applications where polysulfone membranes require heated air to increase permeation.

Production from natural products

Natural phenols can be enzymatically polymerised. Laccase and peroxidase induced the polymerization of syringic acid to give a poly(1,4-phenylene oxide) bearing a carboxylic acidat one end and a phenolic hydroxyl group at the other.[3]

References

Translated from the article Polyphenylenether on the German Wikipedia.

1.

D. Alberti "Modifizierte aromatische Polyether" in Kunststoffe 10/87, S. 1001 A. Hohmann, W. Hielscher: Lexikon der Zahntechnik: Das grundlegende Werk:

12,000 Begriffe aus Zahntechnik und Zahnheilkunde in einem Band. Verlag Neuer Merkur, 1998, ISBN 978-3-929360-28-8 - they are used. [6] The PPE blends are characterized by hot water resistance with low water absorption, high impact strength, halogen-free fire protection and low density.

1. Uyama, Hiroshi; Ikeda, Ryohei; Yaguchi, Shigeru; Kobayashi, Shiro (2001). "Polymers from Renewable Resources". ACS Symposium Series 764. p. 113. doi:10.1021/bk-2000-0764.ch009. ISBN 0-8412-3646-1. |chapter= ignored (help)

External links

Douglas Robello. "Poly(phenylene oxide)". University of Rochester.

"USPTO registration of PPO".

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Nylon

From Wikipedia, the free encyclopedia

For other uses, see Nylon (disambiguation).

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced

material may be challenged and removed. (February 2014)

Nylon 6,6

Density 1.15 g/cm3

Electrical conductivity (σ)

10−12 S/m

Thermal conductivity

0.25 W/(m·K)

Melting point463–624 K190–350 °C374–663 °F

Nylon is a generic designation for a family of synthetic polymers, more specifically aliphatic or semi-aromatic polyamides. They can be melt processed into fibres, films or shapes.[1] The first example of nylon (nylon 66) was produced on February 28, 1935, by Wallace Carothers at DuPont's research facility at the DuPont Experimental Station.[2][3] Nylon polymers have found significant commercial applications in fibres (apparel, flooring and rubber reinforcement), in shapes (moulded parts for cars, electrical equipment, etc.), and in films (mostly for food packaging)[4]

Contents

1 Overview

2 Chemistry

o 2.1 Nomenclature

o 2.2 Monomers

2.2.1 Amino acids and lactams

2.2.2 Diacids

2.2.3 Diamines

o 2.3 Polymers

2.3.1 Homopolymers

2.3.2 Copolymers

2.3.3 Blends

3 Bulk properties

o 3.1 Characteristics

4 Uses

o 4.1 Fibres

o 4.2 Shapes

o 4.3 Food packaging

o 4.4 Filaments

o 4.5 Other forms

4.5.1 Extruded Profiles

4.5.2 Powder Coating

4.5.3 Instrument strings

5 Hydrolysis and degradation

6 Environmental impact, incineration and recycling

7 Current market and forecast

8 Etymology

9 See also

10 References

11 Further reading

12 External links

Overview

Wallace Carothers

Nylon stockings being inspected in Malmö, Sweden in 1954.

Nylon is a thermoplastic,[5] silky material, first used commercially in a nylon-bristled toothbrush (1938), followed more famously by women's stockings ("nylons"; 1940) after being introduced as a fabric at the 1939 New York World's Fair.[6] Nylon is made of repeating units linked by amide bonds and is a type of polyamide and is frequently referred to as such [7]

[8] Nylon was the first commercially successful synthetic thermoplastic polymer.[7] Commercially, nylon polymer is made by reacting monomers which are either lactams, acid/amines or stoichiometric mixtures of diamines (-NH2) and diacids (-COOH). Mixtures ofthese can be polymerized together to make copolymers. Nylon polymers can be mixed with a wide variety of additives to achieve many different property variations.

Nylon was intended to be a synthetic replacement for silk and substituted for it in many different products after silk became scarce during World War II. It replaced silk in military applications such as parachutes and flak vests, and was used in many types of vehicle tires.[6]

After initial commercialization of nylon as a fiber, applications in the form of shapes and films were also developed. The main market for nylon shapes now is in auto components, butthere are many others.

Chemistry

Nylons are condensation copolymers, formed by reacting difunctional monomers containing equal parts of amine and carboxylic acid, so that amides are formed at both ends of each monomer in a process analogous to polypeptide biopolymers. Most nylons are made from thereaction of a dicarboxylic acid with a diamine (e.g. PA66) or a lactam or amino acid with itself (e.g. PA6). In the first case, the structure is so-called ABAB similar to polyesters and polyurethanes: the "repeating unit" consists of one of each monomer, so that they alternate in the chain. Since each monomer in this copolymer has the same reactive group on both ends, the direction of the amide bond reverses between each monomer, unlike natural polyamide proteins, which have overall directionality: C terminal → N terminal. In the second case (so called AA), the repeating unit corresponds to the single monomer.

It is difficult to get the proportions exactly correct, and deviations can lead to chain termination at molecular weights less than a desirable 10,000 daltons (u). To overcome this problem, a crystalline, solid "nylon salt" can be formed at room temperature, using an exact 1:1 ratio of the acid and the base to neutralize each other. The salt is crystallized to purify it and obtain the desired precise stoichiometry. Heated to 285 °C (545 °F), the salt reacts to form nylon polymer with the production of water.

Wallace Carothers at DuPont patented[9] nylon 66, but overlooked the possibility to use lactams. That synthetic route was developed by Paul Schlack at IG Farben, leading to nylon 6, or polycaprolactam — formed by a ring-opening polymerization. The peptide bond within the caprolactam is broken with the exposed active groups on each side being incorporated into two new bonds as the monomer becomes part of the polymer backbone.

The 428 °F (220 °C) melting point of nylon 6 is lower than the 509 °F (265 °C) melting pointof nylon 66.[10]

Nylon 510, made from pentamethylene diamine and sebacic acid, was studied by Carothers even before nylon 66 and has superior properties, but is more expensive to make. In keeping with this naming convention, "nylon 6,12" or "PA 612" is a copolymer of a 6C diamine and a 12C diacid. Similarly for PA 510 PA 611; PA 1012, etc. Other nylons include copolymerized dicarboxylic acid/diamine products that are not based upon the monomers listed above. For example, some fully aromatic nylons (known as "aramids") are polymerized with the additionof diacids like terephthalic acid (→ Kevlar, Twaron) or isophthalic acid (→ Nomex), more commonly associated with polyesters. There are copolymers of PA 66/6; copolymers of PA 66/6/12; and others. In general linear polymers are the most useful, but it is possible to introduce branches in nylon by the condensation of dicarboxylic acids with polyamines having three or more amino groups.

The general reaction is:

Two molecules of water are given off and the nylon is formed. Its properties are determined by the R and R' groups in the monomers. In nylon 6,6, R = 4C and R' = 6C alkanes, but one also has to include the two carboxyl carbons in the diacid to get the number it donates to the chain. In Kevlar, both R and R' are benzene rings.

Industrial synthesis is usually done by heating the acids, amines or lactams to remove water, but in the laboratory, diacid chlorides can be reacted with diamines. For example a popular demonstration of interfacial polymerisation (the "nylon rope trick") is the synthesis of nylon 66 from adipoyl chloride and hexamethylene diamine

Nomenclature

The nomenclature used for nylon polymers was devised during the synthesis of the first simple aliphatic nylons and uses numbers to describe the number of carbons between acid and amine functions (including the carbon of the carboxylic acid). Subsequent use of cyclic and aromatic monomers required the use of letters or sets of letters. One number after "PA" for a homopolymer based on one monomer, and two numbers or sets of letters where there are two monomers. For copolymers the comonomers or pairs of comonomers are separated by slashes, as shown in the examples below.

homopolymers :

o PA 6 : [NH−(CH2)5−CO]n made from ε-Caprolactam ;

o PA 66 : [NH−(CH2)6−NH−CO−(CH2)4−CO]n made from hexamethylenediamine and adipic acid;

copolymers :

o PA 6/66 : [NH-(CH2)6−NH−CO−(CH2)4−CO]n−[NH−(CH2)5−CO]m made from caprolactam, hexamethylenediamine and adipic acid ;

o PA 66/610 : [NH−(CH2)6−NH−CO−(CH2)4−CO]n−[NH−(CH2)6−NH−CO−(CH2)8−CO]m made from hexamethylenediamine, adipic acid and sebacic acid.

In common usage, the prefix 'PA' or the name 'Nylon' are used interchangeably and are equivalent in meaning.

The term polyphthalamide (abbreviated to PPA) is used when 60% or more moles of the carboxylic acid portion of the repeating unit in the polymer chain is composed of a combination of terephthalic (TPA) and isophthalic (IPA) acids

Monomers

Nylon momomers are manufactured by a variety routes, starting in most cases from crude oil but sometimes from biomass. Those in current production are described below.

Amino acids and lactams

ε-Caprolactam: Crude oil → benzene → cyclohexane → cyclohexanone → cyclohexanone oxime → caprolactam

11-aminoundecanoic acid: Castor oil → ricinoleic acid → methylricinoleate → methyl-11-undecenoate → undecenoic acid → 11-undecenoic acid → 11-bromoundecanoic acid → 11-aminoundecanoic acid [11]

Laurolactam: Butadiene → cyclododecatriene → cyclododecane → cyclododecanone → cyclododecanone oxime → laurolactam

Diacids

Adipic acid: Crude oil → benzene → cyclohexane → cyclohexanone + cyclohexanol → adipic acid

Sebacic acid (decanedioic acid): Castor oil → ricinoleic acid → sebacic acid

Terephthalic acid: Crude oil → p-xylene → terephthalic acid

Isophthalic acid: Crude oil → m-xylene → isophthalic acid

Diamines

Tetramethylene diamine (putrescine) Crude oil → propylene → acrylonitrile → succinonitrile → tetramethylene diamine

Hexamethylene diamine (HMD): Crude oil → butadiene → adiponitrile → hexamethylene diamine

2-methyl pentamethylene diamine is a by product of HMD production

Trimethyl Hexamethylene diamine (TMD): Crude oil → propylene → acetone→ isophorone → TMD

m-xylylene diamine (MXD): Crude oil → m-xylene → isophthalic acid → isophthalonitrile → m-xylylene diamine [12]

With increasing interest in biobased materials other monomers are being investigated

1,5-pentanediamine (cadaverine) (PMD): starch (e.g. cassava) → glucose → lysine → PMD [13]

Polymers

Due to the large number of diamines, diacids and aminoacids that can be synthesized, many nylon polymers have been made experimentally and characterized to varying degrees. A smaller number have been scaled up and offered commercially, and these are detailed below.

HomopolymersHomopolymer nylons derived from one monomer

Monomer Polymer

caprolactam 6

11-aminoundecanoic acid 11

ω-aminolauric acid 12

Examples of these polymers that are or were commercially available

PA6 Lanxess Durethan B [14]

PA11 Arkema Rilsan [15]

PA12 Evonik Vestamid L [16]

Homopolymer polyamides derived from pairs of diamines and diacids (or diacid derivatives).Shown in the table below are polymers which are or have been offered commercially either ashomopolymers or as a part of a copolymer.

Putrescine

MPMD

HMD

MXD

Nonanediami

ne

Decanediami

ne

Dodecanediami

ne

bis(para-aminocyclohexyl)meth

ane

trimethylhexamethylenedia

mine

Adipic acid

46 D6 66MXD6

Sebacic acid

410610

1010

Dodecanedioicacid

612

1212 PACM12

Terephthalic

4T DT 6T 9T 10T 12T TMDT

acid

Isophthalic acid

DI 6I

Examples of these polymers that are or were commercially available

PA46 DSM Stanyl [17]

PA410 DSM Ecopaxx [18]

PA4T DSM Four Tii [19]

PA66 DuPont Zytel [20]

CopolymersIt is easy to make mixtures of the monomers or sets of monomers used to make nylons to obtain copolymers. This lowers crystallinity and can therefore lower the melting point.

Some copolymers that have been or are commercially available are listed below:

PA6/66 DuPont Zytel [21])

PA6/6T BASF Ultramid T [22])

PA6I/6T DuPont Selar PA [23]

PA66/6T DuPont Zytel HTN [24])

PA12/MACMI EMS Grilamid TR [25])

BlendsMost nylon polymers are miscible with each other allowing a range of blends to made. The two polymers can react with one another by transamidation to form random copolymers. [26]

According to their crystallinity, polyamides can be:

semi-crystalline:

o high crystallinity : PA46 and PA 66 ;

o low crystallinity : PA mXD6 made from m-xylylenediamine and adipic acid;

amorphous : PA 6I made from hexamethylenediamine and isophthalic acid.

According to this classification, PA66, for example, is an aliphatic semi-crystalline homopolyamide.

Bulk properties

Above their melting temperatures, Tm, thermoplastics like nylon are amorphous solids or viscous fluids in which the chains approximate random coils. Below Tm, amorphous regions alternate with regions which are lamellar crystals.[27] The amorphous regions contribute elasticity and the crystalline regions contribute strength and rigidity. The planar amide (-CO-NH-) groups are very polar, so nylon forms multiple hydrogen bonds among adjacent strands.Because the nylon backbone is so regular and symmetrical, especially if all the amide bonds are in the trans configuration, nylons often have high crystallinity and make excellent fibers. The amount of crystallinity depends on the details of formation, as well as on the kind of nylon. Apparently it can never be quenched from a melt as a completely amorphous solid.

Hydrogen bonding in Nylon 6,6 (in mauve).

Nylon 66 can have multiple parallel strands aligned with their neighboring peptide bonds at coordinated separations of exactly 6 and 4 carbons for considerable lengths, so the carbonyl oxygens and amide hydrogens can line up to form interchain hydrogen bonds repeatedly, without interruption (see the figure opposite). Nylon 510 can have coordinated runs of 5 and 8 carbons. Thus parallel (but not antiparallel) strands can participate in extended, unbroken, multi-chain β-pleated sheets, a strong and tough supermolecular structure similar to that found in natural silk fibroin and the β-keratins in feathers. (Proteins have only an amino acid α-carbon separating sequential -CO-NH- groups.) Nylon 6 will form uninterrupted H-bonded sheets with mixed directionalities, but the β-sheet wrinkling is somewhat different. The three-dimensional disposition of each alkane hydrocarbon chain depends on rotations about the 109.47° tetrahedral bonds of singly bonded carbon atoms.

When extruded into fibers through pores in an industrial spinneret, the individual polymer chains tend to align because of viscous flow. If subjected to cold drawing afterwards, the fibers align further, increasing their crystallinity, and the material acquires additional tensile strength. In practice, nylon fibers are most often drawn using heated rolls at high speeds.[28]

Block nylon tends to be less crystalline, except near the surfaces due to shearing stresses during formation. Nylon is clear and colorless, or milky, but is easily dyed. Multistranded nylon cord and rope is slippery and tends to unravel. The ends can be melted and fused with aheat source such as a flame or electrode to prevent this.

Nylons are hygroscopic, and will absorb or desorb moisture as a function of the ambient humidity. Variations in moisture content have several effects on the polymer. Firstly, the dimensions will change, but more importantly moisture acts as a plasticizer, lowering the glass transition temperature (Tg), and consequently the elastic modulus at temperatures below the Tg [29]

When dry, polyamide is a good electrical insulator. However, polyamide is hygroscopic. The absorption of water will change some of the material's properties such as its electrical resistance. Nylon is less absorbent than wool or cotton.

Characteristics

The characteristic features of nylon 66 include:

Pleats and creases can be heat-set at higher temperatures

More compact molecular structure

Better weathering properties; better sunlight resistance

Softer "Hand"

Higher melting point (256 °C/492.8 °F)

Superior colorfastness

Excellent abrasion resistance

On the other hand, nylon 6 is easy to dye, more readily fades; it has a higher impact resistance, a more rapid moisture absorption, greater elasticity and elastic recovery.

Variation of luster: nylon has the ability to be very lustrous, semilustrous or dull.

Durability: its high tenacity fibers are used for seatbelts, tire cords, ballisticcloth and other uses.

High elongation

Excellent abrasion resistance

Highly resilient (nylon fabrics are heat-set)

Paved the way for easy-care garments

High resistance to insects, fungi, animals, as well as molds, mildew, rot and many chemicals

Used in carpets and nylon stockings

Melts instead of burning

Used in many military applications

Good specific strength

Transparent to infrared light (−12 dB)[30][clarification needed]

Uses

Fibres

These worn out nylon stockings will be reprocessed and made into parachutes forarmy fliers c. 1942

Blue Nylon fabric ball gown by Emma Domb, Chemical Heritage Foundation

Bill Pittendreigh, DuPont, and other individuals and corporations worked diligently during the first few months of World War II to find a way to replace Asian silk and hemp with nylon in parachutes. It was also used to make tires, tents, ropes, ponchos, and other military supplies. It was even used in the production of a high-grade paper for U.S. currency. At the outset of the war, cotton accounted for more than 80% of all fibers used and manufactured, and wool fibers accounted for nearly all of the rest. By August 1945, manufactured fibers hadtaken a market share of 25%, at the expense of cotton. After the war, because of shortages of both silk and nylon, nylon parachute material was sometimes repurposed to make dresses.[31]

Nylon 6 and 66 fibres are used in carpet manufacture.

Nylon is one kind of fibre used in tire cord.

Shapes

Nylon resins are widely used in the automobile industry especially in the engine compartment.[32][33]

Solid nylon is used in hair combs and mechanical parts such as machine screws, gears and other low- to medium-stress components previously cast in metal.[34] Engineering-grade nylonis processed by extrusion, casting, and injection molding. Type 6,6 Nylon 101 is the most common commercial grade of nylon, and Nylon 6 is the most common commercial grade of molded nylon.[35] For use in tools such as spudgers, nylon is available in glass-filled variants which increase structural and impact strength and rigidity, and molybdenum sulfide-filled variants which increase lubricity. Its various properties also make it very useful as a material in additive manufacturing; specifically as a filament in consumer and professional grade fused deposition modeling 3D printers.[36] Nylon can be used as the matrix material in composite materials, with reinforcing fibers like glass or carbon fiber; such a composite has ahigher density than pure nylon.[37] Such thermoplastic composites (25% to 30% glass fiber) are frequently used in car components next to the engine, such as intake manifolds, where thegood heat resistance of such materials makes them feasible competitors to metals.[38]

Nylon was used to make the stock of the Remington Nylon 66 rifle.[39] The frame of the modern Glock pistol is made of a nylon composite.[40]

Food packaging

Nylon resins are used as a component of food packaging films where an oxygen barrier is needed.[4] Some of the terpolymers based upon nylon are used every day in packaging. Nylon has been used for meat wrappings and sausage sheaths.[41] The high temperature resistance of nylon makes it useful for oven bags[42]

Filaments

Nylon filaments are primarily used in brushes especially toothbrushes and 'strimmers'. They are also used as monofilaments in fishing line. Nylon 610 and 612 are the most used polymers for filaments.

Its various properties also make it very useful as a material in additive manufacturing; specifically as a filament in consumer and professional grade fused deposition modeling 3D printers.[36]

Other forms

Extruded ProfilesNylon resins can be extruded into rods, tubes and sheets.[43] [44]

Powder CoatingNylon powders are used to powder coat metals. Nylon 11 and nylon 12 are the most widely used.[45]

Instrument stringsIn the mid-1940s, classical guitarist Andrés Segovia mentioned the shortage of good guitar strings in the United States, particularly his favorite Pirastro catgut strings, to a number of foreign diplomats at a party, including General Lindeman of the British Embassy. A month later, the General presented Segovia with some nylon strings which he had obtained via somemembers of the DuPont family. Segovia found that although the strings produced a clear sound, they had a faint metallic timbre which he hoped could be eliminated.[46]

Nylon strings were first tried on stage by Olga Coelho in New York in January, 1944.[47]

In 1946, Segovia and string maker Albert Augustine were introduced by their mutual friend Vladimir Bobri, editor of Guitar Review. On the basis of Segovia's interest and Augustine's past experiments, they decided to pursue the development of nylon strings. DuPont, skeptical of the idea, agreed to supply the nylon if Augustine would endeavor to develop and produce the actual strings. After three years of development, Augustine demonstrated a nylon first string whose quality impressed guitarists, including Segovia, in addition to DuPont.[46]

Wound strings, however, were more problematic. Eventually, however, after experimenting with various types of metal and smoothing and polishing techniques, Augustine was also ableto produce high quality nylon wound strings.[46]

Hydrolysis and degradation

All nylons are susceptible to hydrolysis, especially by strong acids, a reaction essentially the reverse of the synthetic reaction shown above. The molecular weight of nylon products so attacked drops, and cracks form quickly at the affected zones. Lower members of the nylons (such as nylon 6) are affected more than higher members such as nylon 12. This means that nylon parts cannot be used in contact with sulfuric acid for example, such as the electrolyte used in lead–acid batteries.

When being molded, nylon must be dried to prevent hydrolysis in the molding machine barrelsince water at high temperatures can also degrade the polymer.[48] The reaction is of the type:

Environmental impact, incineration and recycling

Berners-Lee reckons the average greenhouse gas footprint of nylon in manufacturing carpets at 5.43 kg CO2 equivalent per kg, when produced in Europe. This gives it almost the same

carbon footprint as wool, but with greater durability and therefore a lower overall carbon footprint.[49]

Data published by PlasticsEurope indicates for nylon 66 a greenhouse gas footprint of 6.4 kg CO2 equivalent per kg, and a energy consumption of 138 kJ/kg.[50] When considering the environmental impact of nylon, it is important to consider the use phase. In particular when cars are lightweighted, significant savings in fuel consumption and CO2 emissions are reduced.

Various nylons break down in fire and form hazardous smoke, and toxic fumes or ash, typically containing hydrogen cyanide. Incinerating nylons to recover the high energy used tocreate them is usually expensive, so most nylons reach the garbage dumps, decaying very slowly.[51] Nylon is a robust polymer and lends itself well to recycling. Much nylon resin is recycled directly in a closed loop at the injection moulding machine, by grinding sprues and runners and mixing them with the virgin granules being consumed by the moulding machine.[52]

Current market and forecast

As one of the largest engineering polymer families, the global demand of nylon resins and compounds was valued at roughly US$20.5 billion in 2013. The market is expected to reach US$30 billion by 2020 by following an average annual growth of 5.5%.[53]

Etymology

In 1940, John W. Eckelberry of DuPont stated that the letters "nyl" were arbitrary and the "on" was copied from the suffixes of other fibers such as cotton and rayon. A later publicationby DuPont (Context, vol. 7, no. 2, 1978) explained that the name was originally intended to be "No-Run" ("run" meaning "unravel"), but was modified to avoid making such an unjustified claim. Since the products were not really run-proof, the vowels were swapped to produce "nuron", which was changed to "nilon" "to make it sound less like a nerve tonic". Forclarity in pronunciation, the "i" was changed to "y".[6][54]

An alternative but apocryphal explanation for the name is that it is a combination of New York and London: NY-Lon.

See also

Aramid

Forensic engineering

Polymers

Plastic

Nylon 6

Nylon 66

Ballistic nylon

Rip-stop nylon

Cordura

Qiana

Nylon riots

Step-growth polymerization

Nylon-eating bacteria

References

1.

Kohan, Melvin (1995). Nylon Plastics Handbook. Munich: Carl Hanser Verlag. p. 2. ISBN 1569901899.

American Chemical Society National Historic Chemical Landmarks. "Foundations of Polymer Science: Wallace Carothers and the Development of Nylon". ACS Chemistry for Life. Retrieved 27 January 2015.

"Wallace Hume Carothers". Chemical Heritage Foundation. Retrieved 27 January 2015.

"Materials/Polyamide". PAFA. Packaging and Film Association. Retrieved 19 April 2015.

Vogler, H (2013). "Wettstreit um die Polyamidfasern". Chemie in unserer Zeit 47: 62–63. doi:10.1002/ciuz.201390006.

Wolfe, Audra J. (2008). "Nylon: A Revolution in Textiles". Chemical HeritageMagazine 26 (3). Retrieved 27 January 2015.

"Science of Plastics". Conflicts in Chemistry: The Case of Plastics. ChemicalHeritage Foundation. Retrieved 27 January 2015.

Clark, Jim. "Polyamides". Chemguide. Retrieved 27 January 2015.

History of Nylon US Patent 2,130,523 'Linear polyamides suitable for spinning into strong pliable fibers', U.S. Patent 2,130,947 'Diamine dicarboxylic acid salt' and U.S. Patent 2,130,948 'Synthetic fibers', all issued September 20, 1938

Typical physical characteristics of nylon at "Basics of Design Engineering"

http://polymerinnovationblog.com/bio-polyamides-where-do-they-come-from/ Bio-Polyamides: Where Do They Come From?

US patent 2970170

"Ajinomoto and Toray to Conduct Joint Research on Biobased Nylon". Toray.3 Feb 2012. Retrieved 23 May 2015.

https://techcenter.lanxess.com/scp/americas/en/products/description/47/index.jsp?pid=47 PA 6

http://www.rilsan.com/en/rilsan-pa11/pa11-product-information/index.html PA11

http://www.vestamid.com/sites/dc/Downloadcenter/Evonik/Product/VESTAMID/en/brochures/VESTAMID%20L%20compounds%20characteristics.pdf PA12

http://www.dsm.com/markets/automotive/en_US/products-brands/stanyl.html PA46

http://www.dsm.com/products/ecopaxx/en_US/home.html PA410

http://www.dsm.com/products/stanylfortii/en_US/home.html PA4T

http://plastics.dupont.com/plastics/pdflit/europe/zytel/ZYTDGe.pdf PA66

http://catalog.ides.com/Datasheet.aspx?I=9837&U=0&E=92285 glass reinforced 6/66 copolymer

http://ultrapolymers.com/products/detail-9201/ 6/6T copolymer

http://www.dupont.ca/content/dam/dupont/products-and-services/packaging-materials-and-solutions/packaging-materials-and-solutions-landing/documents/selar_pa_2072.pdf 6I/6T copolymer

http://dupont.materialdatacenter.com/profiler/WjB4W/material/pdf/datasheet/ZytelHTN52G35HSLBK083 66/6T copolymer

http://www.emsgrivory.com/en/products-markets/products/product-overview/ 12/MACMI copolymer

Samperi, Filippo; Montaudo, Maurizio S.; Puglisi, Concetto; Di Giorgi, Sabrina; Montaudo, Giorgio (August 2004). "Structural Characterization of Copolyamides Synthesized via the Facile Blending of Polyamides". Macromolecules 37 (17): 6449–6459. doi:10.1021/ma049575x.

Valerie Menzer's Nylon 66 Webpage. Arizona University

Campbell, Ian M. (2000). Introduction to synthetic polymers. Oxford: Oxford Univ. Press. ISBN 0198564708.

http://www.tainstruments.co.jp/application/pdf/Thermal_Library/Applications_Briefs/TA133.PDF Measurement of Moisture Effects on the Mechanical Properties of 66Nylon - TA Intruments Thermal Analysis Application Brief TA-133

Bjarnason, J. E.; Chan, T. L. J.; Lee, A. W. M.; Celis, M. A.; Brown, E. R. (2004). "Millimeter-wave, terahertz, and mid-infrared transmission through common clothing". Applied Physics Letters 85 (4): 519. doi:10.1063/1.1771814.

Caruso, David (2009). "Saving the (Wedding) Day: Oral History Spotlight" (PDF). Transmutations Fall (5): 2. Retrieved 24 June 2013.

http://www.materialdatacenter.com/mb/main/pdf/application/16449 Nylon Oil Pan

Kohan, Melvin (1995). Nylon Plastics Handbook. Munich: Carl Hanser Verlag. p. 514. ISBN 1569901899.

Youssef, Helmi A.; El-Hofy,, Hassan A.; Ahmed, Mahmoud H. (2011). Manufacturing technology : materials, processes, and equipment. Boca Raton, FL: Taylor & Francis/CRC Press. p. 350. ISBN 9781439810859. Retrieved 27 January 2015.

"Nylon 6/6 – Commercial Grades and Properties". Emco Industrial Plastics, Inc. Retrieved November 17, 2014.

"Use of Nylon in 3D Printing". http://3dprintingforbeginners.com/. Retrieved 11 January 2015.

"Fiberglass and Composite Material Design Guide". Performance Composites Inc. Retrieved 27 January 2015.

Page, I. B. (2000). Polyamides as engineering thermoplastic materials. Shawbury, Shrewsbury: Rapra Technology Ltd. p. 115. ISBN 9781859572207.

"How do you take care of a nylon 66 or 77? You don't.". Field & Stream 75 (9). 1971. Retrieved 27 January 2015.

Sweeney, Patrick (2013). Glock deconstructed. Iola, Wis.: Krause. p. 92. ISBN 978-1440232787. Retrieved 27 January 2015.

Colbert, Judy (2013). It happened in Delaware : remarkable events that shaped history (First edition. ed.). Morris Book Publishing. ISBN 978-0-7627-6968-1. Retrieved 27 January 2015.

"Oven Bags". Cooks Info. Retrieved 19 April 2015.

Kohan, Melvin (1995). Nylon Plastics Handbook. Munich: Carl Hanser Verlag. p. 209. ISBN 1569901899.

"Extruded and Cast Nylons". www.quadrantplastics.com. Quadrant Plastics. Retrieved 19 April 2015.

D. S. Richart (1995). "9.1 Powder Coating". In Kohan, Melvin. Nylon PlasticsHandbook. Munich: Hanser. p. 253. ISBN 1569901899.

"The History of Classical guitar strings". Maestros of the Guitar. Retrieved 27 January 2015.

Bellow, Alexander (1970). The Illustrated History of the Guitar. New York: Belwin-Mills. p. 193.

"Adhesive for nylon & kevlar". Reltek. Retrieved 27 January 2015.

Mike Berners-Lee, How Bad are Bananas? The Carbon Footprint of Everything (London: Profile, 2010), p. 112 (table 6.1), http://books.google.is/books?id=zs13m5JquBwC&.

Eco-profiles and Environmental Product Declarations of the European Plastics Manufacturers: Polyamide 6.6. Brussels: PlasticsEurope AISBL. 2014.

Typically 80 to 100% is sent to landfill or garbage dumps, while less than 18% are incinerated while recovering the energy. See Francesco La Mantia (August 2002). Handbook of plastics recycling. iSmithers Rapra Publishing. pp. 19–. ISBN 978-1-85957-325-9. Retrieved 17 October 2011.

Boydell, P; Bradfield, C; von Falkenhausen, V; Prautzsch, G (1995). "Recycling of Waste from Glass-reinforced nylon resins". Engineering Design 2: 8–10.

"Market Report: Global Polyamide Market". Acmite Market Intelligence.

1. Algeo, John (2009). The Origins and Development of the English Language 6. Cengage. p. 224. ISBN 9781428231450.

Further reading

Textiles by Sara J. Kadolph, ISBN 0-13-118769-4

Kohan, Melvin I. (1995). Nylon Plastics Handbook. Hanser/Gardner Publications. ISBN 9781569901892

External links

For historical perspectives on nylon, see the Documents List of "The Stocking Story: You Be The Historian" at the Smithsonian website, by The Lemelson Center for the Study of Invention and Innovation, National Museum of American History, Smithsonian Institution.

Wikimedia Commons has media related to Nylon.

A chemical demonstration of the synthesis of nylon in Carleton University'sCHEM 1000 course. (Video)

Typical properties of Nylon / Polyamide

Polyamide material description

Discussion of nylon synthesis and properties

"How Nylon Yarn Is Made", January 1946, Popular Science from raw material to shipment article with drawings and illustrations

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Polybenzimidazole fiberFrom Wikipedia, the free encyclopedia (Redirected from Polybenzimidazole)

polybenzimidazole

Identifiers

CAS Registry Number

32075-68-6

ChemSpider

Properties

Chemical formula (C20H12N4)n

Molar mass Variable

Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Infobox references

Polybenzimidazole (PBI, short for poly[2,2’-(m-phenylen)-5,5’-bisbenzimidazole]) fiber isa synthetic fiber with a very high melting point. It has exceptional thermal and chemical stability and does not readily ignite.[citation needed] It was first discovered by American polymer chemist Carl Shipp Marvel in the pursuit of new materials with superior stability, retention of stiffness, toughness at elevated temperature. Due to its high stability, polybenzimidazole is used to fabricate high-performance protective apparel such as firefighter’s gear, astronaut space suits, high temperature protective gloves, welders’ apparel and aircraft wall fabrics. In recent years, polybenzimidazole found its application as a membrane in fuel cells.

Contents

1 History

o 1.1 Discovery

o 1.2 Development

2 Properties

o 2.1 General physical properties

o 2.2 Thermal stability

o 2.3 Flame resistance

o 2.4 Moisture regain

3 Synthesis

4 Applications

o 4.1 Protective apparel

o 4.2 PBI membranes

o 4.3 Molded PBI resin

o 4.4 Fuel cell electrolyte

o 4.5 Asbestos replacement

o 4.6 Flue gas filtration

5 References

6 Appendix of properties

o 6.1 PBI fiber characteristics

o 6.2 Chemical resistance

o 6.3 Electrical properties

o 6.4 Mechanical properties

o 6.5 Physical Properties

o 6.6 Thermal Properties

7 External links

History

Discovery

Brinker and Robinson invented the first aliphatic polybenzimidazoles in 1949.[1] However thediscovery of aromatic polybenzimidazole which show excellent physical and chemical properties was generally credited to Carl Shipp Marvel in the 1950s.[2] The materials Laboratory of Wright Patterson Air Force Base approached Marvel. They were looking for materials suitable for drogue parachutes which could tolerate short-time mechanical strength. However, the thermal resistance of all known filaments at that time was completely inadequate. The original search concentrated on aromatic condensation polymers but the amide linkage proved to be weak link for the aim of maximal thermal stability of the polymer, whereas Marvel’s research focused on condensation polymers with aromatic and heteroaromatic repeating units. This progressively led to the discovery of polybenzimidazole.

Development

Its development history can be summarized in the following list:[3]

In 1961, polybenzimidazole was developed by H. Vogel and C.S. Marvel with anticipation that the polymers would have exceptional thermal and oxidative stability.

Subsequently in 1963, NASA and the Air Force Materials Lab sponsored considerablework with polybenimidazole for aerospace and defense applications as a non-flammable and thermally stable textile fiber.

In 1969, the United States Air Force selected polybenzimidazole (PBI) for its superiorthermal protective performance after a 1967 fire aboard the Apollo 1 spacecraft killed three astronauts.

In the 1970s, NASA continued to use PBI as part of the astronauts’ clothing on Apollo, Skylab and numerous space shuttle flights.

When the Sky lab fell to the earth, the part that survived the re-entry was coated in PBI and thus did not burn up.

1980s – PBI was introduced to the fire service, and through Project Fires an outer shell for turnout gear was developed. PBI Gold® fabric was born, consisting of 40% PBI/60% para-aramid. Previous to this, combinations of Nomex, leather, and Kevlar materials were used in the US.

Leather and rubber fire gear left “vital” areas exposed.

PBI gear is a full suit and looks like a snow suit (suspender pants) with a winter coat.

1983 – A unique production plant goes on-line and PBI fibers become commercially available.

1990s Short-cut PBI fibers are introduced for use in automotive braking systems. PBI staple fiber enters the aircraft market for seat fire blocking layers.

1992 Lightweight PBI fabrics are developed for flame-resistant workwear for electric utility and petrochemical applications.

1994 PBI Gold fabric is engineered in black and was specified by FDNY.

2001 – After the terrorist attacks on September 11, many of the 343 fire fighters killedwere only identifiable by their PBI Turnout Gear.

2003 PBI Matrix® was commercialized and introduced as the next-generation PBI forfirefighter turnout gear.

Properties

General physical properties

For the physical properties, PBI are usually yellow to brown solid infusible up to 400 °C or higher.[4] The solubility of PBI is controversial. Because although most of the linear PBI are partly or entirely dissolved in strong protonic acids for instance, sulfuric acid or methanesulfonic acid, contradictory observations of solubities have been recorded among such weaker acids as formic acid, and in non-acidic media, such as the aprotic amide-type solvents and dimethyl sulfoxide. For example, one type pf PBI prepared in phosphoric acid was found by Iwakura et al.[5] to be partially soluble in formic acid, but completely soluble in dimethyl sulfoxide and dimethylacetamide, whereas Varma and Veena[6] reported the same polymer type to dissolve completely in formic acid, yet only partially in dimethyl sulfoxide or dimethylacetamide.

Thermal stability

Imidazole derivatives are known to be stable compounds. Many of them are resistant to the most drastic treatments with acids and bases and not easily oxidized. The high melting point and high stability at over 400 degree suggests a polymer with benzimidazole as repeating unitmay also show high heat stability. Polybenzimidazole and its aromatic derivatives can withstand temperatures in excess of about 500 degree without softening and degrading. The polymer synthesized from isophthalic acid and 3,3'-diaminobenzidine is not melted by exposure to a temperature of 770 degree and loses only 30% of its weight after exposure to high temperature up to 900 degree for several hours.[7] This proves a high thermal stability forPBI.

Flame resistance

A property of a material needed to be considered before putting it into application is flammability, which demonstrates how easily one material can ignite and combust under the realistic operating conditions. This may affect its application in vary areas, such as in construction, plant design, and interior decoration. The quantitative assessment of flammability is based on limiting oxygen index(LOI), i.e., the minimum oxygen concentration at which a given sample can be induced to burn permit a comparison of flammability. Data shows that PBI are highly flame resistant material compared to common polymers.[8]

Moisture regain

Another particular property of PBI, the remarkable moisture regain is useful in protective clothing which make the clothing quite comfortable to wear in sharp contrast to other synthetic polymers. The moisture regain ability of PBI compares favorably with cotton whichregains 13% of moisture with a 16% of cotton.[9]

Synthesis

The preparation of PBI(IV) can be achieved by condensation reaction of diphenyl isophthalate (I) and 3,3’,4,4’-tetraaminodiphenyl (II) (Figure 1). The spontaneous cyclization of the intermediately formed animo-amide (III) to PBI (IV) provided a much more stable amide linkage.This synthetic method was first used in the lab and later developed into a two step process. Ina typical condition, starting materials were heated at 270 degree for 1.5 h to form the PBI

prepolymer and later the prepolymer was heated at 360 degree for another 1 h to form the final commercial-grade product. The reason for the second step is due to the formation of the by-product phenol and water in the first step creating voluminous foam,[10] which leads to the volume expansion of several times of the original. This is the issue must be considered by theindustrial manufacturers. This foam can be reduced by conducting the polycondensation at a high temperature around 200 °C and under the pressure of 2.1-4.2 MPa.[11] The foam can also be controlled by adding high boiling point liquids such as diphenylether or cetane to the polycondesation. The boiling point can make the liquid stay in the first stage of polycondesation but evaporate in the second stage of solid condensation. The disadvantage ofthis method is there are still some liquid remain in PBI and it is hard to remove them completely.[12]

Figure1.The synthetic scheme for polybenzimidazole.

While changing the tetramine and acid, a number of different aromatic poly benzimidazoles have been synthesized. The following table (Table 1)[13] lists out some of the combination possibilities that have been synthesized in the literature. Some of the combination have actually been translated into fibers on a small scale. However, the only significant progress have been made to date is PBI.

Polybenzimidazole derivatives shown in the figure wherein R is an aromatic nucleus symmetrically tetra substituted with the nitrogen atoms of the formula being part of benzimdazole rings. R' being a member of an aromatic hydrocarbon ring.

Table 1.Other monomers which forms derivatives of polybenzimidazole

R(Teraamine) R'(acid))

Benzene Benzene

Diphenyl Diphenyl

Diphenylether Diphenylether

Diphenylsulfone Naphthalene

Naphthalene Pyridine

Pyridine Anthraquinone

Anthraquinone Ferrocene

Anthracene

The most common form of PBI used in industry is the fiber form. The fiber process followingpolymerization is shown in the figure. The polymer is made into solution using dimethylacetamide as solvent. The solution is filtered and converted into fiber using a high temperature dry-spinning process. The fiber is subsequently drawn at elevated temperature to get desired mechanical properties. It is then sulfonated and made into staple using conventional crimping and cutting techniques.

The PBI fiber is made in a serial of steps following polymerization to get PBI staple form for direct usage.

Applications

Before the 1980s, major applications of PBI are for fire-blocking, thermal protective apparel and reverse osmosis membranes. Its applications became various by the 1990s with the fact that the molded PBI parts and microporous membranes were developed.

Protective apparel

The properties such as thermal stability, flame resistant, and moisture regain of PBI and its conventional textile processing character enable it to be processed on conventional staple fiber textile equipment. These characters lead to one of the most important applications of PBI is for protective apparel. PBI filaments were fabricated into protective gears like firefighter’s gear, astronauts suits. PBI filaments are dry spun from dimethylacetamide containing lithium chloride. After washing and drying the resulting yarn is golden brown.

Now the fibers used in the protective gear is poly(2,2’-m-phenylene-5,5’-bibenzimidazole) which use tetraaminobipheny as monomer for a better thermo resistance property

PBI fiber is an excellent candidate for applications in severe environments due to its combination of thermal, chemical and textile properties. Flame and thermal resistance are the critical properties of protective apparel. This kind of apparel applications includes firefighter’s protective apparel, astronaut’s suits,[14] aluminized crash rescued gear, industrial worker’s apparel, and suits for racing car drivers.[15]

Nowadays most of the fire fighters' protective gears are made with PBI fiber

The problem of PBI protective apparel is that it keeps heat out but it also keeps the heat in, too. Thus, by the time the firefighters feel heat and pain, it is too late and they will get burnt or killed since it is hard for the heat to penetrate the suit and be released into the air. There arestill some major fire departments have not yet switched from old fire gear to PBI due to the fear of what PBI can cause. One example is the Chicago Fire Department, which still relies on the old type of rubber or leather coats.[16]

PBI membranes

PBI has been used as the membranes for various separation purposes. Traditionally, PBI was used semi-permeable membranes for electrodialysis, reverse osmosis or ultrafiltration.[17] Recently PBI is also used for gas separations.[18] due to its close chain packing since PBI has rigidity structure and strong hydrogen bonding. PBI membranes are dense, with very low gas permeability.To be proton conductive, PBI usually is doped with acid. The higher level of the acid doping, the more conductive PBI is. But one problem raised is the mechanical strength of PBI decreases The same time. The optimum doping level is thus a compromise between these two effects. Thus, multiple methods such as ionic cross-linking, covlant cross-linking and composite membranes[19] have been researched to optimize the doping level at which PBIhas an improved conductivity without sacrificing mechanical strength. Kerres et al.[20] recently have recently synthesized sulphonated partially fluorinated arylene main chain polymer. Their blend membranes with PBI demonstrate high level acid-doping levels with thermal and extended stability, high proton conductivities, less acid swelling, reasonable mechanical strength.

Fluorinated sulphonated polymers used for preparation of acid–base blend membranes with PB. The blend membranes with PBI have excellent thermal and extended stability

Molded PBI resin

This section contains content that is written like an advertisement. Please help improve it by removing promotional content and inappropriate external links, and by adding encyclopedic content written from a neutral point of view. (May 2014)

PBI resin is molded via a sintering process that was jointly developed by Hoechst Celanese (North Carolina, USA) and Alpha Precision Plastics, Inc. (Houston, Texas, USA).[21] Molded PBI resin is an excellent candidate for high strength, low weight material. Since it has the highest compressive strength, 58 ksi, of any available, unfilled resin and other mechanical properties such as a tensile strength of 23 ksi, a flexural strength of 32 ksi, a ductile compressive failure mode and the relatively low density of 1.3 g/cm3.[22] Moreover, its thermal and electrical properties also make it a well known thermoplastic resin. The PBI resincomprises a recurring structural unit represented by the following figure.

The recurring structural unit for PBI resin

According to the Composite Materials Research Group at the University of Wyoming, PBI resin parts maintain significant tensile properties and compressive strength to 700 °F (371 °C). PBI resin parts are also potential materials for the chemical process and oil recovery industries which have demands of thermal stability and chemical resistance. In theseareas, PBI resin has been successfully applied in demanding sealing, for instance, valve seats,stem seals, hydraulic seals and backup rings. In the aerospace industry, PBI resin has high strength and short term high temperature resistance advantages. In the industrial sector, PBI resin's high dimensional stability as well as retention of electrical properties at high temperature make it used as a thermal and electrical insulator.[23]

Fuel cell electrolyte

Polybenzimidazole is able to be complexed by strong acids because of its basic character. Complexation by phosphoric acid makes it a proton conductive material.[24] This renders the possible application to high temperature fuel cells. Cell performance test show a good stability in performance for 200 h runs at 150 degree. Application in direct methanol fuel cells may be also of interest because of a better selectivity water/methanol compared to existing membranes. Wainright, Wang et al. reported that PBI doped with phosphoric acid

was utilized as a high temperature fuel cell electrolyte.[25] The doped PBI high temperature fuel cell electrolyte has several advantages. The evevated temperature increases the kinetic rates of the fuel cell reactions. It also can reduce the problem of the catalyst poisoning by adsorbed carbon monoxide and it minimizes problems due to electrode flooding.[26] PBI/H3PO4 is conductive even in low relative humidity and it allows less crossover of the methanol at the same time.[27] These contribute PBI/H3PO4 to be superior to some traditional polymer electrolytes such as Nafion. Additionally, PBI/H3PO4 maintains good mechanical strength and toughness.[28] Its modulus is three order of magnitude greater than that of Nafion.[29] This means that the thinner films can be used, thus reducing ohmic loss.

In phosphoric acid doped PBI, the phosphoric acid groups are not directly bonded to the polymer backbone. Instead, the low charge density anion is immobilized and linked to the structure by a strong hydrogen-bond network.

Asbestos replacement

Previously, only asbestos can well perform in temperature gloves such as for foundries, aluminum extrusion, and metal treatment, while PBI trials have been developed and show adequately functions as asbestos. Moreover, a safety garment manufacturer reported that gloves containing PBI outlasted asbestos two to nine times with an effective cost.[30] Gloves containing PBI fibers are softer and more supple than those made of asbestos, offering,the worker greater mobility, and comfort even if the fabric becomes charred. Besides, PBI fiber avoids the chronic toxicity problems associated with asbestos because it processes on standard textile and glove fabricating equipment.[31] PBI also can also be a good substitute forasbestos in several areas of glass manufacturing.

Flue gas filtration

PBI’s chemical, thermal and physical properties demonstrate that it can be a promising material as a flue gas filter fabric for coal fired boilers. Few fabrics can survive in the acidic and high temperature environment encountered in coal fired boiler flue gas.[32] The filter bags also must be able to bear the abrasion from the periodic cleaning to remove accumulated dust.PBI fabric has a good abrasion resistance property. The acid and abrasion resistance and thermal stability properties make PBI a competitor for this application.

References

1.

"Patent on aliphatic polybenzimidazole". Retrieved 7 March 2014. Leonard, Nelson. "A Biographic Memoir of Carl Shipp Marvel" (PDF). National

Academy of Sciences. Retrieved 13 February 2014. "PBI History". Retrieved 14 February 2014. Synthesis and degradation, rheology and extrusion. Berlin u.a.: Springer. 1982.

ISBN 978-3-540-11774-2. |first1= missing |last1= in Authors list (help) Iwakura, Yoshio; Uno, Keikichi; Imai, Yoshio (June 1964).

"Polyphenylenebenzimidazoles". Journal of Polymer Science Part A: General Papers 2 (6): 2605–2615. doi:10.1002/pol.1964.100020611.

Varma, I. K.; Veena, (April 1976). "Effect of structure on properties of aromatic- aliphatic polybenzimidazoles". Journal of Polymer Science: Polymer Chemistry Edition 14 (4): 973–980. Bibcode:1976JPoSA..14..973V. doi:10.1002/pol.1976.170140417.

Vogel, Herward; Marvel, C. S. (April 1961). "Polybenzimidazoles, new thermally stable polymers". Journal of Polymer Science 50 (154): 511–539. Bibcode:1961JPoSc..50..511V. doi:10.1002/pol.1961.1205015419.

van Krevelen, Dirk W. (30 March 1972). Angewandte Makromolekulare Chemie 22 (1): 133–157. doi:10.1002/apmc.1972.050220107. Missing or empty |title= (help)

Demartino, R. N. (1 August 1984). "Comfort Properties of Polybenzimidazole Fiber". Textile Research Journal 54 (8): 516–521. doi:10.1177/004051758405400803.

Chung, Tai-Shung (1 May 1997). "A Critical Review of Polybenzimidazoles". Polymer Reviews 37 (2): 277–301. doi:10.1080/15321799708018367.

Kricheldorf, edited by Hans R. (1992). Handbook of polymer synthesis. (dernière ed.).New York: Marcel Dekker. ISBN 0-8247-8514-2.

Kricheldorf, edited by Hans R. (1992). Handbook of polymer synthesis. (dernière ed.).New York: Marcel Dekker. ISBN 0-8247-8514-2.

Belohlav, Leo R. (10 December 1974). Angewandte Makromolekulare Chemie 40 (1): 465–483. doi:10.1002/apmc.1974.050400122. Missing or empty |title= (help)

Kirshenbaum, edited by Raymond B. Seymour, Gerald S. (1987). High Performance Polymers: Their Origin and Development Proceedings of the Symposium on the History of High Performance Polymers at the American Chemical Society Meeting held in New York, April 15-18, 1986. Dordrecht: Springer Netherlands. ISBN 978-94-011-7075-8.

Sandor, R.B. (1990). "PBI (Polybenzimidazole): Synthesis, Properties and Applications". High Performance Polymers 2 (1): 25–37. doi:10.1177/152483999000200103 (inactive 2015-02-01).

Mager, David. "EVALUATING THE RESULTS OF A MODIFIED BUNKER GEAR POLICY" (PDF). Retrieved 9 March 2014.

Li, Qingfeng; Jensen, Jens Oluf; Savinell, Robert F.; Bjerrum, Niels J. (May 2009). "High temperature proton exchange membranes based on polybenzimidazoles for fuel cells". Progress in Polymer Science 34 (5): 449–477. doi:10.1016/j.progpolymsci.2008.12.003.

Kumbharkar, S.C.; Li, K. (October 2012). "Structurally modified polybenzimidazole hollow fibre membranes with enhanced gas permeation properties". Journal of Membrane Science. 415-416: 793–800. doi:10.1016/j.memsci.2012.05.071.

Li, Qingfeng; Jensen, Jens Oluf; Savinell, Robert F.; Bjerrum, Niels J. (May 2009). "High temperature proton exchange membranes based on polybenzimidazoles for fuel cells". Progress in Polymer Science 34 (5): 449–477. doi:10.1016/j.progpolymsci.2008.12.003.

Kerres, Jochen A.; Xing, Danmin; Schönberger, Frank (15 August 2006). "Comparative investigation of novel PBI blend ionomer membranes from nonfluorinated and partially fluorinated poly arylene ethers". Journal of Polymer Science Part B: Polymer Physics 44 (16): 2311–2326. Bibcode:2006JPoSB..44.2311K. doi:10.1002/polb.20862.

Ward, B.C (1987). "32nd SAMPE Int. Symp.," (32). p. 853.

Sandor, R.B. (1990). "PBI (Polybenzimidazole): Synthesis". High Performance Polymers 2 (1): 25–37. doi:10.1177/152483999000200103 (inactive 2015-02-01).

Sandor, R.B. (1990). "PBI (Polybenzimidazole): Synthesis, Properties and Applications". High Performance Polymers 2 (1): 25–37. doi:10.1177/152483999000200103 (inactive 2015-02-01).

Samms, S. R. (1996). "Thermal Stability of Proton Conducting Acid Doped Polybenzimidazole in Simulated Fuel Cell Environments". Journal of the Electrochemical Society 143 (4): 1225. doi:10.1149/1.1836621.

Wainright,, J.S.; Wang, J.-T., Weng, D., Savinell, R.F., Litt, M (July 1995). "Acid- doped polybenzimidazoles: A new polymer electrolyte". Journal of the Electrochemical Society 142 (7): L121–L123. doi:10.1149/1.2044337.

Samms, S. R. (1996). "Thermal Stability of Proton Conducting Acid Doped Polybenzimidazole in Simulated Fuel Cell Environments". Journal of the Electrochemical Society 143 (4): 1225. doi:10.1149/1.1836621.

Zhao, edited by T.S. (2009). Micro fuel cells : principles and applications. Burlington,MA: Academic Press. ISBN 9780123747136.

Zhao, edited by T.S. (2009). Micro fuel cells : principles and applications. Burlington,MA: Academic Press. ISBN 9780123747136.

Buckley, A (1988). Encyclopedia of Polymer Science And Engineering,. New York: John Wiley & Sons.

Coffin, D.R.; Serad, G.A.; Hicks, H.L.; Montgomery, R.T. (1 July 1982). "Properties and Applications of Celanese PBI--Polybenzimidazole Fiber". Textile Research Journal 52 (7): 466–472. doi:10.1177/004051758205200706.

Celanese. "PBI in High Temperature Protective Gloves" (PDF). Retrieved 9 March 2014.

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Appendix of properties

PBI fiber characteristics

The chemical formula of poly[2,2’-(m-phenylen)-5,5’ bibenzimidazol] (PBI) is believed to be: ([NH-C=CH-C=CH-CH=C-N=C-]2-[C=CH-C=CH-CH=CH-])n OR (C20N4H12)n of Molar mass 308.336 ± 0.018 g/mol.[citation needed]

Chemical resistance

Chemical Resistance GradeAcids - concentrated PoorAcids - dilute Fair-PoorAlcohols GoodAlkalis Good-PoorAromatic hydrocarbons GoodGreases and Oils GoodHalogenated Hydrocarbons GoodKetones Good

It is dyeable to dark shades with basic dyes following caustic pretreatment and resistant to most chemicals.

Electrical properties

Electrical PropertiesDielectric constant @ 1 MHz 3.2Dielectric strength 21 kV·mm−1

Volume resistivity 8x1014 Ω·cm

Features low electrical conductivity and low static electricity buildup.

Mechanical properties

Mechanical PropertiesCoefficient of friction 0.19-0.27Compressive modulus 6.2 GPaCompressive strength 400 MPaElongation at break 3%Hardness - Rockwell K115Izod impact strength 590 J·m−1 unnotchedPoisson's ratio 0.34Tensile modulus 5.9 GPaTensile strength 160 MPa

Features abrasion resistance.

Physical Properties

Physical PropertiesChar Yield (under pyrolysis) HighDensity 1.3 g/cm³Flammability Does not burnLimiting oxygen index 58%Radiation resistance GoodWater absorption - over 24 hours 0.4%

Additional features: will not ignite or smolder (burn slowly without flame), mildew- and age-resistant, resistant to sparks and welding spatter.

Thermal Properties

Thermal Properties GradeCoefficient of thermal expansion 23×10−6·K−1 LowHeat-deflection temperature - 0.45 MPa 435 °C (815 °F) HighThermal conductivity @ 23 °C (73 °F) 0.41 W·m−1·K−1 LowUpper working temperature 260–400 °C (500–752 °F) High

Other features: continuous temperature: 540 °C (1,004 °F), does not melt but degrades aroundthe temperature: 760 °C (1,400 °F) under pyrolysis, retains fiber integrity and suppleness up to 540 °C (1,004 °F).

External links

Polybenzimidazole (PBI) - Material Information

Summary of Polybenzimidazole

PBI Polymer Performance Study

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Organic polymers

Synthetic fibers

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