Compatibilizing immiscible blends with block copolymers and pulverization

While addition of block copolymer during melt mixing of immiscible polymer blends has yielded compatibilization in small-scale academic studies, it has not been commercially successful due to thermodynamic and kinetic limitations. We show that addition of a commercially available styrene/ethylene-butylene/styrene triblock copolymer to an immiscible polystyrenepolyethylene blend during solid-state shear pulverization (SSSP) can substantially reduce coarsening in subsequent melt processing. In comparison with blends made by melt mixing, blends mixed by SSSP led to coarsening of the dispersed phase during high temperature annealing that was reduced by more than an order of magnitude. We believe that mixing block copolymer with the blend by SSSP yields greater levels of block copolymer near the interfacial regions as compared to melt processing. By overcoming the thermodynamic limitation of block copolymer micelle formation during melt processing, block copolymer addition via SSSP offers a commercially viable strategy for blend compatibilization.