The Preparation Of Microcellular Foamed PC/PMMA Films With Supercritical CO₂ And Its Performance Study

In this paper, Firstly, PMMA microspheres were prepared by emulsifier-free emulsion polymerization, and the effects of the reaction parameters on the surface morphology and the particle size were systematically investigated. Secondly, PC/PMMA films at various ratios were prepared by solution casting using MC as a co-solvent, the compatibility of PC and PMMA was studied. Finally, the crystallinity of PC which induced by supercritical CO2 were studied, and the microcellular foamed blend films of PMMA microspheres and PC were prepared with supercritical fluid through the two-step process, using supercritical CO2 as physical foaming agent, and the effects of process conditions on the cell structure were studied.The results showed that PMMA microsphres had a good sphericity, the surface was smooth, and the particle size increased with the increment of the monomer concentration and the acetone dosage, but decreased with the increment of the initiator dosage. It was also found that the size of the PMMA microspheres was uniform while adding Cu2+at the beginning of the reaction, but with a uniform particle size about 285 nm while adding Cu2+after 2h of polymerization. The SEM images showed a co-continue morphology in the 10% PC/90% PMMA and 20% PC/80% PMMA blends, but showed a dispersed phase in matrix morphologies for 50% PC/50% PMMA,80% PC/20% PMMA and 90% PC/10% PMMA blends. The crystallinity of PC increased with the increment of the absorption time, saturation temperature and saturation pressure, but decreased with the increment of the PC content in the blends. What’s more, when the PC content was above 80%, there was no crystallization in the PC/PMMA blends. The mean cell diameter of microcellular foamed PC/PMMA films decreased with the increment of saturation temperature and saturation pressure, but increased with the increment of foaming time. In addition, with the increment of foaming temperature, the mean cell diameter decreased first, but then increased. The cell density increased with the increment of saturation temperature and saturation pressure, but decreased with the increment of foaming time. With the increment of foaming temperature, the cell density increased first, but then decreased.