Effect of dissolved CO2 on the crystallization behavior of linear and branched PLA

In this study, the crystallization behavior of polylactide (PLA) was investigated in the presence of dissolved CO2 using high-pressure and regular differential scanning calorimeter. The isothermal and non-isothermal melt crystallization results showed that increasing the CO2 pressure decreased the crystallization half-time. During isothermal and low-cooling-rate non-isothermal crystallization, a very high crystallinity was achieved at 15 bar CO2 pressure by facilitating more perfect crystal formation with the plasticization effect of CO2 while limiting the crystal nucleation rate. At higher CO2 pressures, a larger number of less close-packed crystals were formed due to chain entanglement, and consequently, the final crystallinity was decreased. The non-isothermal results at high cooling rates showed the total crystallinity decreased for all CO2 contents, because of less time given for crystallization. Also the effects of the CO2 pressure and the cooling rate on Tc and Tg were investigated.