Effect of high pressure treatment on thermal properties of polylactides

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 °C. 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 (Tg) 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 (ΔHm) and crystallization enthalpy (ΔHc). Fourier transform infrared (FTIR) spectroscopy 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.