Diene rubbers carbon-black-filled

The Payne effect of carbon black reinforced rubbers has also been investigated intensively by a number of different researchers [36-39]. In most cases, standard diene rubbers widely used in the tire industry, bke SBR, NR, and BR, have been appbed, but also carbon black filled bromobutyl rubbers [40-42] or functional rubbers containing tin end-modified polymers [43] were used. The Payne effect was described in the framework of various experimental procedures, including pre-conditioning-, recovery- and dynamic stress-softening studies [44]. The typically almost reversible, non-linear response found for carbon black composites has also been observed for silica filled rubbers [44-46]. 

The barrier properties of 70/30 acrylonitrile-butadiene mbber/ethylene propylene diene monomer rubber (NBR/EPDM) vulcanizates, when loaded with carbon black fillers [e.g., I SAP (intermediate super-abrasion furnace), HAF (high-abrasion furnace) and SRF (semi-reinforcing furnace)] and using benzene, toluene and xylene as penetrants, have been examined with reference to the type of filler employed [66]. The filled samples were found to exhibit a better resistance to uptake of the three organic solvents when compared to the respective unfilled blends for any given blend ratio. With regards to the three types of carbon black used, solvent uptake was in the order SRF-> HAF-> ISAF-filled samples. The reason for this order was attributed to the better filler reinforcements and enhanced crosslink densities of the matrix as the size of the carbon black particles used was decreased. A similar behavior was also identified for NR/EVA composites [52]. 

Silicone rubber and, in general polar polymers, are by nature materials of choice for preparing silica filled systems however limited to niche applications, with respect to the range of properties that such specialty polymers may offer. In order to develop optimum reinforcing performance with more common diene elastomers, silica must be chemically treated as we will see below, because contrary to carbon blacks, silica particles do not develop spontaneous strong interactions with nonpolar polymers. It is nevertheless interesting to see that, even with comparable size and structure, pure silica does not affect the mechanical properties of vulcanized rubber compounds in the same manner as carbon black. 

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