Measuring the Compatibility of Petroleum-Based Hydrocarbon Resins in Elastomers

Hydrocarbon resins are typically defined as low molecular weight polymers with high softening points produced from various petroleum fractions. They are commonly employed in rubber formulations to improve processing, influence surface tack, or otherwise modify the viscoelastic properties or the compound. In each of these cases, a degree of compatibility between the hydrocarbon resin and the other polymeric ingredients in the formulation is required.

A series of hydrocarbon resins possessing similar glass transition temperatures and molecular weights but varying composition are mechanically blended with a set of elastomers in order to elucidate what structural parameters lead to compatibility. The hydrocarbon resins are based on pure and blended C5 and C9 feedstocks, and a styrenic monomer grade. Compatibility is measured by thermal analysis and dynamic mechanical testing of the binary blends, quantifying the influence of resin addition on the glass transition temperature and viscoelastic properties compared to that of the neat polymers. Solubility parameters are calculated for the polymers and resins and compared to experimental data in order to determine if they can be used to accurately predict the degree of compatibility.