Polymer Clay Nano Composites

8/3/2019 Polymer Clay Nano Composites

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POLYMER CLAY

NAONCOMPOSITES

By:- Bakulesh Singh(09107017)

Supervised By:-Mrs. Prem Lata


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What is Nano?

The word nano is derived from the Greek word fordwarf. In a nutshell, nanoscience is the study of theextremely small. Nanoscience is concerned with thestudy of the unique properties of matter at its nano level

and exploits them to create novel structures, devicesand systems for a variety of different uses. Particleshaving sizes less than 100 nm are generally callednanoparticles. These have strikingly different properties

due to their small size and thus are found useful inmany applications. The ability to measure andmanipulate matter on the nanometer level is makingpossible a new generation of materials with enhancedmechanical, optical, transport and magnetic properties.


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NANOCOMPOSITES

A nanocomposite can be taken as a multiphase solid materialwhere one of the phases has one, two or three dimensions ofless than 100 nanometers (nm), or structures having nano-scalerepeat distances between the different phases that make up the

material. In the broadest sense this definition can includeporous media, colloids, gels and copolymers, but is moreusually taken to mean the solid combination of a bulk matrix andnano-dimensional phase(s) differing in properties due todissimilarities in structure and chemistry. The mechanical,

electrical, thermal, optical, electrochemical, catalytic propertiesof the nanocomposite will differ markedly from that of thecomponent materials.


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Size limits for these effects have been proposed,


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This large amount of reinforcement surface area meansthat a relatively small amount of nanoscalereinforcement can have an observable effect on the

macroscale properties of the composite. For example,adding carbon nanotubes improves the electrical andthermal conductivity. Other kinds of nanoparticulatesmay result in enhanced optical properties, dielectricproperties, heat resistance or mechanical propertiessuch as stiffness, strength and resistance to wear anddamage. In general, the nano reinforcement is dispersedinto the matrix during processing. The percentage byweight (called mass fraction) of the nanoparticulates

introduced can remain very low (on the order of 0.5% to5%).


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POLYMER NANOCOMPOSITES Polymer nanocomposites (PNC) is a polymer or

copolymer having dispersed in its nanoparticles. Thesemay be of different shape (e.g., platelets, fibers,spheroids), but at least one dimension must be in therange of 1 to 50 nm. These PNC's belong to the

category of multi-phase systems (MPS, viz. blends,composites, and foams) that consume nearly 95% ofplastics production. These systems require controlledmixing/compounding, stabilization of the achieveddispersion, orientation of the dispersed phase, and the

compounding strategies for all MPS, including PNC, aresimilar.


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A Little Introspection..

The devices that utilize the properties of low dimensionalobjects such as nanoparticles are promising due to thepossibility of tailoring a number of electrophysical, opticaland magnetic properties by changing the size of

nanoparticles, which can be controlled during thesynthesis. In the case of polymer nanocomposites wecan utilize the properties of disordered systems. Thoughthere is much utilization in this field, there are many

limitations also. For example in the release of drugsusing nanofibres, cannot be controlled independentlyand a burst release is usually the case, whereas a morelinear release is required. Let us now consider futureaspects in this field.


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There is a possibility of building ordered arrays ofnanoparticles in the polymer matrix. An even moreattractive method exists to utilize polymer

nanocomposites for neural networks applications.Another promising area of development isoptoelectronics and optical computing. The singledomain nature and super paramagnetic behavior ofnanoparticles containing ferromagnetic metals could bepossibly utilized for magneto-optical storage mediamanufacturing.


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NANOCLAY Nanoclay is the most widely investigated nanoparticle in

a variety of different polymer matrices for a spectrum ofapplications.

The origin of bentonite (natural clay) is most commonlyby the in-situ alteration of volcanic ash, as shown in Fig..Another, less common, origin is the hydrothermalalteration of volcanic rocks. Bentonite containsmontmorillonite but also can contain glass, mixedlayer

clays, illite, kaolinite, quartz, zeolite, and carbonates.Clay soil has particle size of less than 2m. The

expanding clays are phyllosilicates, smectite, andmontmorillonite, and the nonexpanding clays are talc,kaolin, and mica.


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STRUCTURE Silica is the dominant constituent of the montmorillonite

clays, with alumina being essential. The chemical structure ofmontmorillonite clays is illustrated in Fig., showing its sheet structureconsisting of layers containing the tetrahedral silicate layer and theoctahedral alumina layer. The tetrahedral silicate layer consists ofSiC4 groups linked together to form a hexagonal network of the

repeating units of composition. The alumina layer consists of twosheets of closely packed oxygens or hydroxyls, between whichoctahedrally coordinated aluminum atoms are imbedded in such aposition that they are equidistant from six oxygens or hydroxyls. Thetwo tetrahedral layers sandwich the octahedral layer, sharing theirapex oxygens with the latter. These three layers form one clay sheet

that has a thickness of 0.96 nm. The chemical formula of themontmorillonite clay is Na^1/3(Al5/3Mg1/3)Si4010(OH)2. In itsnatural state Na+ cation resides on the MMT clay surface.


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Why is organic treatment so important?Because layered silicates are hydrophilic materials, they must be madeorganophilic (hydrophobic) to become compatible with most host polymersthat are hydrophobic polymers. Without organic treatment, layer silicates willonly disperse and phase separate in the presence of very polar polymers.Organic treatment is typically accomplished via ion exchange betweeninorganic alkali cations on the clay surface with the desired organic cation.The organic treatment, at the interface between inorganic silicate and

organic polymer, is a vital part of the polymer nanocomposite, andtherefore, it must be tailored to synthetic conditions. Synthetic methods forpolymer nanocomposite preparation include solvent mixing, in-situpolymerization, and melt compounding. One of the most "industryfriendlymethods of making polymer nanocomposites is the use of meltcompounding. The polymer and organically treated clay are heated to the

melting point of the polymer, and the two are mixed together usingcompounding equipment. There are several types of clay surfacetreatments, which are listed below:-

Quaternary ammonium salts (current) based on textile antistatic agents

Alkyl imidazoles which provides improved thermal stability

Coupling and tethering agents, reactive diluents and can be functionalamino compounds (Others consist of cation types containing phosphorous


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Dispersing the nanoclay.

Achieving exfoliation of organomontmorillonite in variouspolymer continuous phases is a function of the surfacetreatment of the MMT clays and the mixing efficiency ofthe dispersing apparatus or equipment. Three types of

mixing equipment are recommended to dispersehydrophobic nanoclays into different resin systems. Therecommended equipment is as follows: high-shear mixeror 3 roll mill for liquid resins, Brabender mixer for viscous

resins, or twin-screw extruder for solid resins. Thepreparation of polymer-clay nanocomposites is clearlyillustrated In the Fig..


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Depending on the physical state of the polymer, one canincorporate the clay into the polymer by solution blending,melt blending, or in-situ polymerization processes to form

polymer-clay nanocomposites Polymer-clay nanocompositescan be classified morphologically into (a) unmixed, (b)intercalated, and (c) exfoliated (delaminated) states, asshown in Fig. 2.5. The most desirable morphological state forthe polymer-clay nanocomposites is exfoliation, followed by

intercalation. The processing challenge of nanoclay is todisperse the 8-m particles into > 1 million platelets using theproper processing technique and conditions. The dispersionmechanism can be: (a) via a chemistry route, as with in-situ

polymerization; (6) via a processing route, as in extrusion; or(c) by combining the chemistry and the processing routes(the optimal way), as is summarized in Fig. 2.7.


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Structural PropertiesThe first successful and significant development of polymer-

clay nanocomposites (PCNs) was pioneered by Toyota'sresearchers19"23 for high performance reinforced plasticsapplications in automobiles. The earliest successes in theautomotive industry are credited to the sonication processdeveloped by Ford Corporation to better disperse the claywithin the polymer. Related to these early disclosures,General Motors Corporation (GMC) developed a step-assistcomponent for 2002 GMC Safari and Chevrolet Astro vans,which is made of thermoplastic polyolefin-clay

nanocomposite. This material is lighter and stiffer, morerobust at low temperatures and easily recyclable. GMC alsoused these PCNs in the lateral protection wire of the 2004Chevrolet Impala since the PCNs are 7 percent lighter in

weight and present a better surface appearance.


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New applications of hybrid PCNs are envisaged by the automotiveindustry for commercialization: PP-clay for bodywork with anti-scratchproperties (Dow Plastics/Magma); acetal-clay for ceiling lights (Show aDenko); PP-clay for panes of doors, consoles and interiors decoration

(Ford, Volvo) due to aesthetics, recyclability and weight saving properties;nylon-clay for bumpers with enhanced mechanical and weight savingproperties (Toyota); nylon-clay for fuel reservoir with air tight properties(Ube America).

Beside the above properties characteristics, the weight advantage

provides a significant impact on the environment. It has been reported thatwidespread use of PCNs by U.S. automotive industry could save 1.5billion liters of gasoline in one year of automotive production and reducerelated carbon dioxide emissions by more than 10 billion pounds. Forenvironmental applications, nanoclays are used as effective reinforcingagents in "green nanocomposites." These renewable resource- basedbiodegradable nanocomposites consist of cellulose plastics (plasticsmade from wood); polyactic acid (corn-derived plastic) orpolyhydroxyalkanate (bacterial polyester). They are attractive materials assubstitutes for petroleum feedstock in making the manufacture ofbiodegradeable plastic for the commercial market.


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Gas Barrier PropertiesThrough the incorporation of nanoclays in polymer matrices,it is possible to create a labyrinth within the structure, whichphysically delays the passage of gas molecules. Theexcellent barrier properties of gas and vapor transmissionhave resulted in applications for food and beveragepackaging as well as barrier liners in storage tanks and fuel

lines for cryogenic fuels in aerospace systems. BayerPolymers have developed a hybrid material combiningsilicate nanoparticles with the features of polyamide 6 (PAG)and ethylene vinyl alcohol (EVOH); it is inexpensive with

good barrier properties. The silicate modified PAG is not asattractive a barrier as EVOH but is significantly better thanneat PAG.


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Nanocor and Mitsubishi Gas Chemical Company developedthe MXD6 high barrier semi-aromatic nylon nanocomposites.Mitsubishi marketed this PCN under the Imperm trade name.

The new material features oxygen and carbon dioxide barrierproperties that were previously unachievable. Imperm'sbarrier properties are superior to EVOH and its processingcharacteristics are ideal for multilayer films, bottles, andthermoformed containers.


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Honeywell has developed a polyamide-clay nanocompositewith specific active and passive oxygen barrier properties.The passive barriers are the nanoclays, which render it more

difficult for oxygen transmission inside the composite, butalso conduct the oxygen molecules to specific oxygen-captors. The clay incorporation limits the oxygen transmissionup to 1520 percent of the value for the pure polymer. TritonSystems and the U.S. Army collaborated on the development

of PCNs as non-refrigerated packaging materials, whichconserves food freshness for three years.

InMat Inc. has developed several applications for theirnanocomposite coatings. The nanocomposite coating of the

Wilson tennis balls maintains the internal pressure for anextended period of time. The figure shows the Wilson tennisballs containing a double core.


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The core is coated by a polymer-clay (vermiculite)nanocomposite that acts as a gas barrier, doubling its shelflife. It is anticipated this technology can be extended to the

rubber industry and be incorporated into soccer balls or inautomobile or bicycle tires.

The barrier properties of PCNs have also been extended toliquids (solvents) or molecules such as water, since theseliquids are responsible in some instances in polymerdeterioration. De Bievre and Nakamura of Ube Industrieshave reported a significant reduction in fuel diffusion throughpolyamide-6/66 polymers by incorporation of nanoclay,resulting in reduced fuel emissions for fuel tank and fuel line

components. InMat Inc. is collaborating with the U.S. Armywith regard to the concept of liquid/hydrocarbon barriers.Some envisaged applications are protective gloves andcoatings for combustibles and fuel tanks.


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Flame Retardant Properties Thermal stability and fire retardancy have facilitated the

investigation of nanoclay as an FR additive for commoditypolymers as reported byOilman et al. Gitto (polymermanufacturer) and Nanocor (nanoclay manufacturer) aredeveloping fire retardant polyolefin-clay nanocomposites,since this polymer has a wide range of industrialapplications. The heat distortion temperature (HDT) of PCNscan be increased to 100C and extend their usage to highertemperature applications such as automotive under-the-hoodparts.


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Some Other Properties In some cases, the value of PCNs technology relates to

value-added performance of mechanical barrier or fireretardant properties not present in the neat polymer but occurvia the low volume introduction of these organically modifiedlayered silicates (OLS). For example, in contrast to

conventional filled polymers that are opaque and exhibitcompromised mechanical properties. The introduction of alow volume fraction of OLS that is of nanoscopic dimensionsand uniformly dispersed within the polymer results in PCNwith optimum transparency and clarity similar to the neat

polymer. Further these PCNs exhibit multifunctionalitybehavior that is unavailable in neat polymer.

Polymer Clay Nano Composites

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