Rubber-clay nanocomposites

The term elastomer is used to describe vulcanized polymeric materials, whose glass transition is sub-ambient and, amongst other properties, has the ability to 

The tyre industry consumes almost 70% of the total SBR production, since SBR has suitable properties of very good abrasion resistance, ageing resistance and low temperature properties.  

Butyl mbber is a copolymer of isobutylene with a small amount of isoprene (2-3% by weight), which represent sites that allow crosslinking. HR has unusually low resilience for an elastomer with such a low Tg of about — 70°C. Since butyl mbber is largely a saturated elastomer with no double bonds, it has excellent resistance to ozone, oxygen, chemicals and heat. Another outstanding feature of this mbber is its low gas permeability and is thus widely used in iimer tubes and tyre liners. Other butyl mbber industrial applications are in cable insulations and jacketing, roof membranes and pharmaceutical stoppers.  

The tyre industry has been attracted by these outstanding properties and BR is often used in blends with SBR in the manufacture of car tyres, and with natural rubber in manufacturing truck tyres. It is the third most important and consumed (by volume) elastomer in the tyre industry after SBR and NR.  

Ethylene propylene copolymers (EPM) are made by Ziegler-Natta and metallocene polymerization and are the commercial mbbers with the lowest density. EPM cannot be vulcanized and thus is not reactive to peroxide curing. To introduce an unsaturated site suitable for crosslinking, a non-conjugated diene termonomer such as ethylidene norbomene, 1,4 hexaadiene or dicyclo-pentadiene, is employed to produce the mbber known as EPDM. Ethylene propylene diene mbber has small number of double bonds, external to the backbone, introduced in this way. In EPDM, the E stands for ethylene, the P for propylene, the D for diene and the M indicates that the mbber has saturated chain of the polymethylene type, properties of EPM and EPDM are  

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Rubber-clay nanocomposites are particularly attractive for potential applications where enhanced barrier properties are desired. Organoclays for rubber intercalation were prepared... 

The effect of polymer-filler interaction on solvent swelling and dynamic mechanical properties of the sol-gel-derived acrylic rubber (ACM)/silica, epoxi-dized natural rubber (ENR)/silica, and polyvinyl alcohol (PVA)/silica hybrid nanocomposites was described by Bandyopadhyay et al. [27]. Theoretical delineation of the reinforcing mechanism of polymer-layered silicate nanocomposites has been attempted by some authors while studying the micromechanics of the intercalated or exfoliated PNCs [28-31]. Wu et al. [32] verified the modulus reinforcement of rubber/clay nanocomposites using composite theories based on Guth, Halpin-Tsai, and the modified Halpin-Tsai equations. On introduction of a modulus reduction factor (MRF) for the platelet-like fillers, the predicted moduli were found to be closer to the experimental measurements. 

The X-ray diffraction peaks observed in the range of 3°-10° for the modified clays disappear in the rubber nanocomposites. photographs show predominantly exfoliation of the clays in the range of 12 4 nm in the BIMS. Consequently, excellent improvement in mechanical properties like tensile strength, elongation at break, and modulus is observed by the incorporation of the nanoclays in the BIMS. Maiti and Bhowmick have also studied the effect of solution concentration (5, 10, 15, 20, and 25 wt%) on the properties of fluorocarbon clay nanocomposites [64]. They noticed that optimum properties are achieved at 20 wt% solution. At the optimized solution concentration, they also prepared rubber/clay nanocomposites by a solution mixing process using fluoroelastomer and different nanoclays (namely NA, 10A, 20A, and 30B) and the effect of these nanoclays on the mechanical properties of the nanocomposites has been reported, as shown in Table 4 [93]. 

Rubber-Clay Nanocomposites Some Recent Results... 

Rubber-Clay Nanocomposites Some Recent Results Table 7 Recipes for the S-SBR vulcanizates... 

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