Elucidation of segmental relaxations of silica‐filled cis‐polybutadiene rubber composites

Abstract

There has been a lot of interest in characterizing polymer chain dynamics of rubber compounds because it is thought to underpin the exceptional mechanical properties of composites. We studied the effect of precipitated silica on segmental mobility of cis-polybutadiene rubber by using differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). It was found that the calorimetric glass and melting transitions of silica-filled master batch materials were essentially identical to those of the gum rubber, showing no dependence of silica loading and silane treatment. And, we observed in calorimetric measurement a change in the melting transition step for the vulcanizates. The results were correlated to the change of chemical crosslinks caused by various factors filler agglomeration and adsorption effect that tended to decrease chemical crosslink density and silane modification increased it. The DMA results demonstrated that the second peak in loss modulus versus temperature curve for the quenched vulcanizates was assigned to melting peak, and this peak disappeared at a slow cooling rate, which coincided well with DSC results. Moreover, crystalline parts constrained amorphous regions such that the glass transition temperature was raised for the cooled vulcanizates with high chemical crosslinks.

Investigating the viscoelastic and hysteresis behavior of nano silica/carbon black hybrid reinforced styrene‐butadiene rubber vulcanizates via surface silanization

“…Moreover, the decrease in the rate of the vulcanization process and hence, CLD of the compounds with filler networks is also explained to be due to the encapsulation or entrapment of a fraction of the rubber chains within the filler networks. The chains are not able to contribute efficiently in the formation of the cross‐linking reactions 28,29 . Hosseini et al reported similar reports on the effectiveness of the modifier on the curing kinetics and the changes in CLD of the silica‐ filled SBR 30 .…”

“…The chains are not able to contribute efficiently in the formation of the cross-linking reactions. 28,29 Hosseini et al reported similar reports on the effectiveness of the modifier on the curing kinetics and the changes in CLD of the silicafilled SBR. 30 Zhang et al also concluded that the filler nature and its content directly impacts the CLD of the rubbers, chain enthalpy, and its relaxation.…”

“…As expected due to the higher extent of silica aggregation for the 35 phr silica loaded, evidenced SEM image presented in Figure 2. These behaviors are attributed to the poisoning effect of the silica silanol (SiOH) groups on the sulfur vulcanization, which reduces the efficiency, and the rate of cross‐linking process, even for the compounds filled with surface modified silica 28 . Moreover, the decrease in the rate of the vulcanization process and hence, CLD of the compounds with filler networks is also explained to be due to the encapsulation or entrapment of a fraction of the rubber chains within the filler networks.…”