Reinforcement of Styrene Butadiene Rubber Employing Poly(isobornyl methacrylate) (PIBOMA) as High Tg Thermoplastic Polymer

A set of poly(isobornyl methacrylate)s (PIBOMA) having molar mass in the range of 26,000-283,000 g mol(-1) was prepared either via RAFT process or using free radical polymerization. These linear polymers demonstrated high glass transition temperatures (T-g up to 201 degrees C) and thermal stability (T-onset up to 230 degrees C). They were further applied as reinforcing agents in the preparation of the vulcanized rubber compositions based on poly(styrene butadiene rubber) (SBR). The influence of the PIBOMA content and molar mass on the cure characteristics, rheological and mechanical properties of rubber compounds were studied in detail. Moving die rheometry revealed that all rubber compounds filled with PIBOMA demonstrated higher torque increase values Delta S in comparison with rubber compositions without filler, independent of PIBOMA content or molar mass, thus confirming its reinforcing effect. Reinforcement via PIBOMA addition was also observed for vulcanized rubbers in the viscoelastic region and the rubbery plateau, i.e. from -20 to 180 degrees C, by dynamic mechanical thermal analysis. Notably, while at temperatures above similar to 125 degrees C, ultra-high-molecular-weight polyethylene (UHMWPE) rapidly loses its ability to provide reinforcement due to softening/melting, all PIBOMA resins maintained their ability to reinforce rubber matrix up to 180 degrees C. For rubber compositions containing 20 phr of PIBOMA, both tensile strength and elongation at break decreased with increasing PIBOMA molecular weight. In summary, PIBOMA, with its outstanding high T-g among known poly(methacrylates), may be used in the preparation of advanced high-stiffness rubber compositions, where it provides reinforcement above 120 degrees C and gives properties appropriate for a range of applications.

Automated summary

The study focused on the reinforcement effect of PIBOMA on rubber compounds, showing that PIBOMA can increase the torque increase values and maintain its reinforcing effect up to 180 degrees C. For rubber compositions containing 20 phr of PIBOMA, both tensile strength and elongation at break decreased with increasing PIBOMA molecular weight.