Instantaneous Phase Separation at the Contact Surface in Compression Molding of Immiscible Polymer Blend

Immiscible polymer blends with a co-continuous phase structure (CPS) can yield synergistic material properties. In this study, a 50/50 wt% PLA/PS blend with CPS was used as a model system to explore the influence of compression molding conditions (including compression rate, compression ratio, and mold surface characteristics) on the final phase structure of the molded part. The microscopic characterization clearly demonstrated the instantaneous formation of a PLA rich layer at the mold contact surface when a high compression ratio and fast compression rate were applied during molding. CFD simulations were performed to numerically study the effects of compression on phase structure evolution in binary blends. If harnessed appropriately, this phase separation process may be utilized for creating innovative material structures.