Effect of high pressure treatment on thermal properties of polylactides

摘要

Effect of high pressure treatment on thermal properties of amorphous and semi-crystalline polylactides (PLA) was studied. Three different PLA isomers (D, L and DL) with molar mass in the range of 3800-6200 were pressurized (350, 450 and 650 MPa) for a holding time of 15 min and the process temperature was maintained in the range of 22-26 ℃. Thermal properties (glass transition temperature, melting behavior and crystallinity) of post-process samples were analyzed by a differential scanning calorimetery (DSC) and compared with untreated sample. The glass transition temperature (T_g) was found to decrease as pressure was applied to lactides. During pressure treatment, it was observed that both melting and crystallization peak of L-isomer were significantly reduced at 650 MPa and the observation was quantified by decrease in fusion (△H_m) and crystallization enthalpy (△H_c). Fourier transform infrared (FTIR) spectros-copy could not detect the change in the crystalline band (1300-1150 cm~(-1)) of pressure treated L-isomer. This study suggests that PLA could be further experimented for development of food packaging material under high pressure treatment either individually or in combination with other materials.