Fillers dispersion crosslink measurement

Non-linear mechanical properties were observed for rubber eomposites and referred to as the Payne effect. The Payne effeet was interpreted as due to filler agglomeration where the filler clusters formed eontained adsorbed rubber. The occluded rubber molecules within filler elusters eould not eontribute to overall elastic properties. The composites behaved similarly to rubber composites with higher filler loading. Uniform and stable filler dispersion is required for rubber composites to exhibit linear viscoelastic behaviour. Payne performed dielectric measurements on SBR vulcanizates containing silica or carbon black. The dielectric data were used to construct time-temperature superposition master curves. The reference temperature increased with crosslinking but not significantly with filler. Comparison of dynamic mechanical and dielectric results for the SBR blended with NR was made and interpreted. ... 

The potential use of palm oil fatty acid additive (POFA) as a new rubber ingredient in carbon black-filled NR compounds is examined. It is found that the cure time (t90) and scorch time decrease with increasing POFA concentration. The Mooney viscosity of the rubber compounds also decreases with increasing POFA concentration. The mechanical properties of the carbon black-filled NR compounds are enhanced by the addition of POFA, especially at a concentration of 2 phr. Results of the swelling measurement and scanning electron microscopy indicate that POFA has some effect on crosslink density and also improved filler dispersion. 9 refs. 

Apart from the depression of and the accompanying dispersion of the tan S peak, the main effect of oil on the dynamic properties is an overall reduction in the elastic modulus, when measured at constant filler loading and crosslink density. This is accompanied initially by a slight rise in the magnitude of the tan 8 peak followed, at higher oil levels, by a large fall. This latter fall is associated with the separation of the agglomerates by the interposed oil, which reduces the hysteresis effect. 

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