Enhancement of rubber-carbon black interaction by amine-based modifiers and their effect on viscoelastic and mechanical properties

Abstract

Improvement in rubber-filler interaction is desirable for rubber technologists due to its influence on numerous properties of rubber compounds and vulcanizates. In practice, there are coupling agents commercially available for the improvement of silica-rubber interaction. Surprisingly, only a limited number of works have been focused on interaction enhancement between carbon black (CB) and rubber. Thus, in the research presented in this article, attempts to improve interaction between ethylene-propylene rubber (EPM) and carbon black (CB) have been made by the use of either p-phenylene diamine (p-PDA) or N-tert-butyl-2-benzothiazole sulfenamide (TBBS) as an interaction modifier. Bound rubber content (BRC), used as an indicator for rubber-filler interaction and viscoelastic behavior of CB masterbatches and CB-filled EPM compounds were investigated and correlated. Results from the measurement of BRC in the CB masterbatches revealed that p-PDA was more effective in the enhancement of rubber-CB interaction than TBBS. Such improved interaction led to a decrease in magnitude of CB percolation (Payne effect). In respect of viscoelastic behavior, the interaction modifiers affected G' only in the small strain region ( < 1% strain) by slightly raising the value of G'. However, as strain was increased (≥1%), G' for all compounds was coincident implying a disruption of weak interaction between CB and rubber. In the case of EPM vulcanizates, p-PDA yielded greater enhancement in mechanical properties than TBBS. The results of BRC, viscoelastic behavior, and mechanical properties were apparently in good agreement. © 2012 Wiley Periodicals, Inc.