sachin seminar

8/7/2019 sachin seminar

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TPO COATED PP FABRICS AND THEIR

APPLICATIONS

ABSTRACT:-

Olefin polymers are most chemical resistant inert materialavailable in their commercial category for industrial applications. The last eradominated uses of olefin polymer in commodity applications eliminatingtraditional metals and non metals. The future is poised for domination ofthermoplastic polyolefin (TPO) in engineering polymer applications. Among a fewconverters all over the world, Entremonde has commercialized and patentedTPO coating on polypropylene fabric (PP). The TPO coated PP fabrics havemany advantage over PVC, PU and rubber coated fabrics.

Use of coated fabrics inmanufacture of protective covers,storage systems, agriculture coverings andpond linings has a long history. The products mainly categorized as PVC coatedfabrics, PU coated fabrics, acrylic polymer coated fabric, wax coated fabrics(canvas) and rubber-coated fabrics. The common usage of coated fabrics are forexample (i) Tarpaulins (ii) Vehicle covers or truck tarpaulins (iii) Tents (iv)Agriculture coverings and fumigation sheets (v) Awnings (vi) Canopies, Tents,Covers etc. In all the types of coated fabrics, fabric component impart desiredmechanical property, i.e. Breaking strength, tearing strength, bursting strength,dimensional stability etc. There are number of types of yarns used formanufacturing a fabric, they are polyester, nylon (polyamide), cotton,regenerated cellulose etc. There are number of types of processes that are used

in manufacturing a fabric, they are weaving, knitting and random laying of fibersto make a non-woven. The mechanical properties desired in coated fabrics aredecided by various properties of fabric used viz. weight, type of yarn, structurewhether monofilament, multifilament or texturised, twists, polymer materialproperty like crystallinity, chemical and thermal resistance etc. One can choose afabric material from almost unlimited options available for the purpose of coatingas per the end usage requirement.

The coating formulations are based on mainpolymer categories viz. PVC (Polyvinyl Chloride), PE and other Poly olefins, PU(Polyurethane), Acrylics, Rubber (natural or synthetic) and waxes.Cotton fabric

coated with wax formulations are called canvas, is a most common and primitiveform of coated fabric. With the invention of new materials and their formulationsthe number of options available are plenty. The most common are PVC andrubber based formulation where a number of additives are used to prepare asuitable fluid to coat on a fabric. The categories of additives are fillers,pigments and dyes, solvents, plasticizers and functional additives are used inalmost all types of polymers to formulate a compound having desired property.


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The coatings impart or modify surface properties, barrier and aesthetics of acoated fabric for the required function or end use.

The biggest problem is, disposal ofwaste, generated after the use of coated fabrics. Recycling of coated fabrics is

not an easy or a common task. In almost all of the cases the family of thepolymer used in manufacturing a fiber and coating compound are heterogeneoushence their physical mixing to regenerate in the form of recyclable goods, is notpossible even by applying high temperature or pressure. The second option,though not environment friendly remain to dissolve, but again common solvent ormixture of solvents cannot dissolve entire coated fabric for recycling purpose.There are solvents available to partly dissolve a coating but it is not aneconomical and environmentally friendly process, because of volatility ofsolvents. The only option remains is to safely incinerate the waste, which haslong-term economic effects, if all the precautions are taken from environmentalpoint of view.

INTRODUCTION:-

There are two polyolefin polymers used to make synthetic fibres,polypropylene and polyethylene, with polypropylene being byfar the most important. The definition for polyethylene fibres is"fibre composed of linear macromolecules of unsubstitutedsaturated aliphatic hydrocarbons" and for polypropylene fibres"fibre composed of linear macromolecules made up ofsaturated aliphatic carbon units in which one carbon atom in

two carries a methyl side group...". Polyethylene was firstproduced in the UK in 1933 by polymerising ethylene underpressure. In 1938 in Germany polyethylene was made bypolymerising ethylene in an emulsion. Polypropylene wascommercialised in 1956 by polymerising propylene usingcatalysts. Both of these polyolefins are very important in plastic moulding and formaking plastic sheet but both are spun into synthetic fibres on a large scale.


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PRODUCTION:-

Polyolefin fibres are made by melt spinning.Usually polymer granules made by specialist producersrather than fibre companies are fed to an extruder which

melts the polymer which is then pumped through a spinneret.The filaments are cooled in an air stream before being woundon a package or collected in cans as a tow. Because thefibres are difficult to dye, coloured pigments are often addedto the polymer stream before extrusion

.An alternative process is to produce a film, cut the film into strips and thenfibrillate the individual strips before winding onto a package. Recently a newfamily of catalysts to make polypropylene has been developed calledmetallocene catalysts. It is claimed that the polymers made from these catalysts

can be spun to finer counts and drawn to give higher tenacities than existingpolymers.

PROPERTIRS:-

Both polyolefin fibres have a density less than 1.0 and therefore, ata given decitex, are thicker than other man-made fibres and give more cover.They do not absorb moisture, which is an advantage in many end-uses, butwithout modification, they cannot be dyed. Their melting points are around 130

C for polyethylene and 160 C for polypropylene. They have a high resistance tochemical attack and modern polypropylene fibres have a high resistance to UVdegradation


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What is coating ?

Coating is carried out to impart certain desired

characteristics and functionalities to woven, knitted or non-woven materials. Oneor two sided application of coating compounds is done on foam films to wovenfabric, knit goods, non woven fabrics and such application of coating compoundsis imparted by means of roller system, knife coating, hot-melt and transfercoating methods. Coated fabrics may be constructed using woven, knitted ornon-woven fabrics.

Coating and lamination is gaining ground worldwide as ameans for value addition and the factors that drive their usage are:

Surface engineering (coating & lamination) allows a base material to be chosenfor a particular set of attributes (weight, cost, corrosion resistance, thermal

capability) while the surface has a different set of properties (hardness, electricalresistance or conductivity, mating characteristics, thermal transfer or shielding).

Coatings have also facilitated the development of entirely new products andhave led to innovations in the area of "Smart" materials. Coating and laminationcuts across virtually every product group in the textile industry, includingcomposites, where the potential is especially broad.

Coatings enable significant cost savings when compared with solid materials oflike composition.

Coatings can be tailored to application specific requirements quite readily andusually at low cost.

Approximately 100 material types of various grades and strengths are used ascore materials (substrates) for coated fabrics: silk, cotton, polyamide, polyester,polyaramid, glass fabric, carbon fabric and metal.

Coated fabrics have wide applications in fields such as medical substrates,protective clothing, flexible membranes for civil structures, airbags, geo textiles,industrial fabrics, defense, transportation, healthcare, architecture, space, sports,environmental pollution control, and may other diverse end-product uses.Extensive research is being done on a global basis, and many new products,such as breathable fabrics, thermochromic fabrics, and charcoal fabrics, areentering the market.

The most frequently used method is coating by means of knife blade coating.An air knife is used to metre the coating compound above the freely spread fabricweb. This method is used for fine coatings and primer coatings at 5 to 50 g permetre (g/m). Air knives may be used over a roller to metre the coating compound


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DEFINATION OF TPO:-

Defining thermoplastic polyolefin (TPO) is difficult.Thermoplastic is a generic term in polymer science; it encompasses a class ofpolymers that, as mentioned above, soften when heated in a reversible process.The term olefin is even more generic being an old chemical name for anymolecule containing carbon-carbon double bonds (the modern name for thisfamily of molecules is alkenes). Any polymer formed by chemically linking upmany olefin molecules is termed polyolefin. According to the latest draft ASTMstandard for TPOs, the composition is very non-specific. The standard states thatTPOs must contain more than 95% by mass of TPO polymer. The polymer itselfis not defined within the standard, which states only that the sheet shall containthe appropriate polymers. Because of this loose definition, there is an endlesslist of chemicals that would fall under this standard (e.g. polyethylene,polypropylene, and isobutylene, as well as their derivatives). Ideally,manufacturers would specify the exact polymer in terms of marketing andlabeling. One point is clear, however: unlike plasticized thermoplastics, TPOs donot contain plasticizers. Therefore, the problem of plasticizer loss associated withsome plasticized polymers is eliminated.

The TPO and PP are basically inert towards chemical and microorganismattack. The finished products have good resistance towards oxygen and ozoneand are flexible at very low temperature i.e. -60C. The products are odourlessand do not give out toxic gases on burning.

The product are lighter than PU or PVC or rubber coated fabrics sincepolyolefin are lower in density than PU, PVC or rubbers formulations. The coatingas well as fabric are homologous polymers hence are melt recyclable, which isnot possible in the case of conventional polymer coated fabrics.

The coated fabrics are available in variety of colors. The dope dyed PP yarncan be produced in excellent uniform bright colors, which are UV stable. TPOcoating contains light stable pigments. The properties can be custom designedby altering thickness, strength, flexibility, colors and grain design. In few specialcases fire retardancy can also be archived.

The fabrics are available in both side as well as one side coated versions,weldable by thermo fusion welding machine. The fabrics are suitable in a numberof applications. To name a few there are:

Flexible storage tanks for liquids.High altitude Tents and light weight sport field covers.Roofing membranesGround sheets, agriculture covers and pond lines for algae farmingBiogas generator covers.Lightweight swimming pool covers.Awnings and canopies.


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Automobile interiors.

BENEFITS OF TPOs:-

In general, TPO membranes are being marketed as aproduct that combines the properties of EPDM and PVC, without the associateddrawbacks that the latter two materials have. In other words, they are supposedto be as UV-resistant and as heat-resistant as EPDM, and as heat-weldable asPVC.

The following benefits and characteristics have been reported for TPOs

environmentally friendly and recyclable

seams can be heat welded

available in many colours

resistant to heat and UV degradation

resistant to many chemicals

good cold-temperature flexibility

no external plasticizers added.

PERFORMANCE OF TPOs:-

TPO membranes are lighter in weight and easier tohandle than the other thermoplastic membranes. But, while flexible, they have arather rigid feel: they tend to hold their shape, and do not relax quickly.

Contractors appear to be adjusting slowly to them and some say they are not"contractor-friendly." Their comments about TPOs include the following:

Hot-air-welded seams are easy and clean;

Costs are lower than for other hot- airwelded membranes;

Mechanically fastened systems (as opposed to loose laid or fully adheredsystems) work well in recover applications without adding extra load;

Non-reinforced flashing membranes are easy to form for detailing;

Noticeable changes in colour and texture occur over time;

Membranes respond dramatically (expansion and contraction) to

temperature changes; Cold welds (i.e., welds at temperatures that are not hot enough) occur

frequently; the start and stop positions of the robotic welder are especiallycritical, as are the positions of t-seams;

Narrow welding window exists between cold welds and scorch/burn-through (i.e., welds at temperatures that are too hot);

Failure of substrate bonding adhesive is common (i.e., not sticking tomembrane);


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Membranes sometimes require solvent wipe (to clean or prime) beforewelding;

Re-welding membranes (in repair) is problematic after exposure to sun;

Black membranes are more difficult to weld than white ones.

PROCESSING:-

The methods of processing are common to processing ofcoated textiles. As it is understood that the Olefin polymers cannot be coated byconventional spreader knife technique, the extrusion calendering is the bestsuitable technique used in processing of these materials.

In principle it is basicallya continuous extrusion unit consisting of different arrangement of rollersadjustable to a fixed nip opening. The coated fabric is produced by in situpressure laminating the calendered sheet. In this process the care is taken toavoid thermal shocks to the sensitive materials to avoid deterioration ofmechanical properties. It is worth mentioning here that the whole system is olefinpolymer based and sensitive to the processing temperature. A PP fabric ifprocessed under warp tension at temperature above its Tm the tenacity is greatlyaffected. Calendering processes have advantage in terms of uniformity andflawlessness of coating however the initial investment cost is high. Following are

description ofcommon calendering process used for TPO coating.


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Inverted L calendar:

These calenders have additional rolls to resurface theTPO sheet before lamination. In this process four rolls provide three meteringstations (nips)


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Inclined Z calendar:

This is typical equipment is used in processing rubbers; anelastomeric TPO can easily be processed with this type of arrangement.

The calender equipments producing coated fabrics are further equipped withAuxiliary equipments which impart processing ease for further handling ofmaterial. The auxiliaries are very important for processing of TPO coated PP

fabrics.

The fabric pretreatments, formulation of TPO compound with functionaladditives both processability point of view as well as enhancement of finalproduct properties are few other important parameters considered for processingof these specialty fabrics.


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A typical calendar coating line is shown in the following figure.


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TYPICAL PROPERTIES OF TPO COATED PP FABRIC:-

APPLICATIONS OF TPO COATED PP FABRICS:-Following described are

some specific applications of the TPO coated PP fabrics

BIO GAS COVERS:-

The biogas generators have seen traditional covers madeout of MS to PVC coated fabric. The biogas is a combination of hydrocarbon fuelgases with some amount of by-product like oxides or sulphur and nitrogen. The

waste mass and fermented slurry also contain dissolved gases andmicroorganism, which are corrosive in nature. The corrosive environment ofthese generators phased out MS and replaced with PVC coated polyester fabric.The cover made out of PVC coated fabric also experienced short lifetime due toplasticizer migration and inherent poor, chemical and microorganism resistance.PVC coated fabric based products face problem of constant repairs andreplacement in a duration of 3 years maximum. The leakage losses are quitehigh and add negatively to the overall economics of running the generators.


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The PP coated TPO fabric is a single solution to all the above cited problems. Atypical example of product suitable for the above applications is 1.1mm thickdouble side TPO coated PP fabric with approximate strength of 135/110 Kg. Thecompound used for coating is a formulation based on reactor modified TPO

instead of traditional TPO blends. The benefit of reactor modified formulationover TPO blends are enormous; it is resistant to UV radiation as well as tocorrosive chemicals present in the waste of biogas reactor and the resulting gas,thermally stable i.e. withstanding capacity in the summer heat and wintertemperature shocks. The TPO coated PP fabric has been tested at 60C. Theoverall composite is made out of PP homologue hence question of non-compatibility like dissimilar polymers, polyester / Nylon and PVC or PU does notarise. The Specific Gravity remains 0.9 as against 1.3-1.5 of PU or PVC coatedFabric, which is a great handling and operational ease in biogas generatorcovers.

The outside color of fabric is light and the inside is made dark to avoid excessivesummer heat absorption that could kill anaerobic bacteria. The fabric has allpossibilities and flexibility of fabrication like other coated fabrics and also therequired maintenance possibilities. The choice of strength, weight and colorsremains with the end user requirement as Entremonde has earned expertise inthe custom designing of a product.

BULK BAGS AND CONTAINER LININGS:-

Use of olefin polymers in transport worthy packing is very common in consumeras well as in industrial sectors. Fibs (Flexible intermediate Bulk bags) and BLBs(Bulk Liner Bags) have gained popularity of transport worthy packing of solids. Avery common example is woven sack used in cement and food grain packaging.However FIBs and BLBs are produced using TPO coated PP fabrics, sewing orwelding them into large bags of required format. In FIBs one loop, tow loop, four


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loops etc. are commonly used formats. Welded joints are employed as per therequirement of storage of materials, normally wet resins, fine powders etc. Thesebags and containers can have valves for ease of filling and unloading. FIBs andBLBs offer a cost effective, efficient and environmental friendly way oftransporting bulk materials. Use of multiple loops made out of webbing with

monofilament PP yarn provides extra strength and thus the bags can be handledusing cranes. These can be manufactured and sealed very fast using ultrasonicor heat welding.

ROOFING MEMBRANES:-

In typical low slope roofing systems thermal insulation barrier and water proofingmembrane determines comfort of home. The traditional membranes consist ofPVC or EPDM coated polyester or polyamide fabric. But as discussed earlierPVC and EPDM materials have their own draw back. New concept of TPOcoated fabric came out with all possible solution to prevailing drawbacks ofconventional materials. Thanks to the developments in multifilament PP yarns, asufficiently high tensile strength textile can be manufactured for this application.The conventional welding equipment can be used for on the spot weldingoperations.


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FLEXIBLE LIQUID STORAGE TANKS:-

Flexi tanks are containers made out ofcoated fabrics in various shapes and sizes. The common shapes are pillow type,onion, orange etc. that ranges from 250 liters to 50,000 liters capacity. Thesetypes of tanks provide temporary as well as long term liquid storage facility. Theyare used in water, oil, fruit juice, milk products, chemical and fuel storage and / ortransportation. The flexi tanks are categorized into two types one time used bulkcontainers and permanent use containers. Traditionally rubber coated, PVCcoated or TPU coated fabrics are used in these application. TPO coated PPfabrics have many distinct advantages in terms of inertness of these fabrics tovarious solvents, these are relatively safe for food grade applications followingphotographs shows some tanks.


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AUTOMOTIVE INTERIORS:-

Thermoplastic olefins (TPO) are new generation compounds, which find

increasing application in automotive interiors. TPOs are materials of future andare finding their place due to properties over the existing materials.

At present, PVC is dominantly used in many of the auto interior applications fordoor panels, roofing upholstery etc. There are certain reasons why PVC is notthe preferred interior material abroad any more.

In European markets, there are strong environmental objections to use PVCbecause of lead and cadmium containing additives, Phthalate plasticisers andlack of recyclability. Besides this, PVC coated fabric suffers from migrationproperties of the plasticizers leading to fogging and poor ageing problems.

Against this, TPO coated on PP fabric, offers considerablefollowing advantages.

1. Since TPO is made out of polymeric materials and pigments, problemsassociated with plasticizer migration of PVC are totally eliminated as alsocracking problems due to ageing.

2. The light weightness of TPO coated fabric is remarkable. This is primarily dueto sp.gravity differences.


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3. There is absolutely no smell in the coated fabric unlike in the case of PVCCoated fabrics.

4. The feel is also dry. If offers good cleaning properties.

5. The oil and chemical resistance are superior to those of PVC Coated fabrics.

The interiors made of TPO coated fabrics have distinct advantage of recycling,as they are same family of materials used in structure and skins etc. Though nota major critical requirement for Indian market but under the globalization norms,this is an implied need of auto interiors.

SPORTING TENTS, LIGHT WEIGHT SPORT FIELD COVERS, AGRICULTURECOVERINGS AND TRUCK TARPAULINS:-

The use of polyolefin polymers especially polypropylene is common in sports andagriculture application4. The artificial grass polypropylene based apparels due towicking properties, pond lines green house covers are few examples. TPOcoated PP fabrics find application in all above-mentioned applications as per theirmaterial property benefits as discussed previously over conventional PVC coatedfabrics. The PVC coated fabric faces problem due to plasticizer migration andthey are not easy to clean. The material used in PVC based product are higher indensity, therefore they are quite heavy and difficult to handle. Followingphotographs illustrate these applications.

GROUND SHEET:-

Ground Sheet is an essential item used by all soldiers in ground forces. This isan item of their personal kit. The Ground Sheet are used as sleeping mat,temporary shelters, to collect water from stream in remote area or as ahammock. The conventional products are rubber, canvas or cotton based, andhave inherent problems since natural products are susceptible to degradation inmany ways. Cotton fabric being a natural fiber has many disadvantages, like


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rough use and daily use makes it very vulnerable to microbial attack, when it iswet it does not dry up as quickly as polypropylene. The rubber compounddegrades because of unsaturated sites available in its structure. The problem ofoozing is quite common in rubber-coated fabrics. Therefore in older version ofground sheets, which is a composite of rubber and cotton, there were many

problems, like weathering, UV resistance, and chemical and microbiologicalresistance and heaviness due to high-density of materials. EntremondePolyecoaters has invented patented1 technology to manufacture PP- TPOGround Sheet composite product to over come the above problem faced inconventional product. These Ground Sheets are successfully introduced in ourDefence forces.

CONCLUSION:-

The woven TPO coated products are finding diverse applicationin industry. The demanding application areas are building and constructionproducts where these fabrics find application as house wrap peel and stick windflashing, under slab vapor retarder. The new application in out door banners,posters, construction sheet, fabric architecture pond liner and geotextiles aredeveloping areas. In conclusion the possible applications of PP TPO compositeare limited by once own imagination.

RERERENCES:-

1.www.fibre2fashion.com

2.www.alcochemical.com

3.www.thomasnet.com4.m.khandwe, a.k. mody indian patent 211228

5.www.textileworld.com

6.www.omnova.com7.www.eatp.org

8.www.milliken.com

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