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Solvent absorption has been followed in compressionmolded rubber vulcanizates for toluene in natural rubber (gum), calcium carbonate (CC)-filled natural rubber composites, and polymer-encapsulated calcium carbonate (PCC)-filled natural rubber composites. The surface resistance is found to affect the absorption process of the composites. Diffusion from the sample sides is considered for thickness and the diffusion coefficients corrected accordingly. Aspects of the effect of PMMA on the equilibrium toluene take up, Fickian mode of transport; transport coefficients; activation parameters; and crosslink density are studied. The sorption results have been interpreted in terms of first-order kinetic model. The crosslink densities calculated from equilibrium sorption successfully to explain the transport coefficient values of the composites. POLYM. ENG. SCI., 53:2487-2497, 2013. ª 2013 Society of Plastics Engineers Process for Encapsulation of Filler Particles by DispersionPolymerization. A mixture of whiting powder and appropriate amount of deionized water was stirred in presence of a small quantity of polyacrylic acid (dispersing agent) in a three-necked flask with high-speed stirrer for 10 hr to get aqueous suspension of whiting [14]. The completely dispersed material was washed several times with deionized water. The dry product was heated at 3008C for 2 hr and crushed into fine powder with a high-speed labora-

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