EFFECT OF VULCANIZATION TEMPERATURE AND DIFFERENT FILLERS ON THE PROPERTIES OF EFFICIENTLY VULCANIZED NATURAL-RUBBER

Results of an experimental study are presented in which the authors dealt with effect of vulcanizaton temperature on the polymer-filler interaction parameter, vulcanizate structure, and the technical properites of efficiently vulcanized natural rubber stocks in the presence of different fillers. They have used carbon blacks of four different particle sizes (ISAF, HAF, SRF, FT), reinforcing silica, and whiting. In the case of black fillers, as the particle size increases, reversion resistance increases. For all fillers, an increase of curing temperature from 150 to 180 degree C caused a reduction in strength, modulus, hardness, resilience; and an increase in elongation at break, compression set, and heat build-up. However, the flexing properties and abrasion loss showed improvement at higher curing temperature. Silica showed erratic behavior in that Kraus plots indicate nonreinforcement by the filler. Whiting also behaved abnormally with respect to Kraus plots; at lower filler loading, the system is nonadherent, becoming weakly adherent at higher concentrations. Westlinning and Wolff's alpha //F values were found to be independent of curing temperature and characteristic of fillers only (the larger the particle size, the lower is the alpha //F value). The increase in apparent crosslinking density in the case of reinforcing fillers is due to increasing upsilon //r arising out of increased polymer-filler interactions.