Homogeneous nanocellular foams from styrenic-acrylic polymer blends

摘要

Nano-cellular foams were successfully produced from blends of styrenic and acrylic polymers by a two-step batch foaming process using carbon dioxide as the blowing agent. Addition of poly (ethyl methacrylate) or poly(methyl methacrylate-co-ethyl acrylate) to styrene-acrylonitrile copolymers, even at a low level, resulted in very homogeneous foams with smaller cell size and narrower cell size distribution than with the individual polymers. The best nanofoams produced from miscible blends have average cell sizes below 100 nm, cell densities up to 5 × 10~(15) cm~(-3) and medium-to-low relative densities (void fraction between 60 and 70%). Contrary to previous studies, it was found that blends with lower co_2 solubility gave higher cell density nanofoams. This suggests new mechanisms for the nucleation of foams from these blends at the nanoscale.