Polylactic Acid (PLA)-CO_2 Foams at Sub-critical Conditions

摘要

Solubility and diffusion coefficients of Carbon Dioxide (CO_2) in polylactic acid (PLA) (poly-L-lactic acid (PLLA) and poly-DL-lactic acid (PDLLA) copolymer) have been measured at room temperature and pressures up to 5.8 MPa. Based upon x-ray diffraction analysis it was found that CO_2 induced crystallinty in the samples. The results indicated that the crystallinty increased with processing pressure with the largest increases noted at pressures between 2.1 and 2.8 MPa under room temperature conditions. These findings were used to investigate the effect of different saturation conditions on the cellular structures of foams produced using various processing temperatures. Samples saturated at 2.8 MPa and room temperature for two days, followed by foaming at 100℃ gave a uniform cellular structure with a cell diameter in order of 30-40 μm and a cell density of 7.93 x 10~7 cell/cm~3.