Quantifying the Miscibility of Biobased Resins in Binary Polyisoprene Systems

The miscibility of polymer–resin systems is a key factor for processing behavior and performance of elastomer compounds, yet it is commonly assessed only indirectly. In this work, a quantitative approach for evaluating experimental characterization of the molecular interaction of amorphous polymer filler composites is introduced based on glass transition measurements by differential scanning calorimetry (DSC). Binary mixtures of isoprene rubber (IR) with three distinct biobased resins, a terpene resin, a rosin ester, and a maleic-modified rosin ester, were investigated over the entire composition range. The molecular interaction is expressed by an interaction parameter which reveals stronger repulsive interactions between IR and the rosin ester compared to the other resins of investigation. Mechanical investigation by torque measurements during mixing and transmission electron microscopy (TEM) indicates a correlation between the interaction parameter measured by DSC and the miscibility of the components of the composites.