The effect of alcoholic solutions on the thermomechanical properties of immersed poly(lactic acid) films

Abstract

The effects of aqueous and deuterium oxide (D2O) solutions of alcohols (methanol, ethanol, 1-propanol, 2-propanol, and 1-butanol) on the thermomechanical properties of poly(lactic acid)—PLA—films were assessed by dynamic mechanical analysis. The glass transition temperature (Tg) of PLA films immersed in 25%, 50%, 75%, and 100% (v/v) alcoholic solutions were compared with the Tg of films immersed in 100% water and D2O. The Tg of PLA films immersed in methanol and ethanol aqueous solutions decreased as the concentration of the alcohol solutions increased. For methanol and ethanol, the Tg decreased by 8.6 and 7.6°C per 25% (v/v) increase in alcohol, respectively. When the PLA films were immersed in propanol aqueous solutions and butanol, the Tg reached the lowest value at 75% (v/v) and 100% (v/v), respectively. Tg of PLA films immersed in 1-propanol and 2-propanol decreased by 8.6 and 8.9°C for every 25% increase in propanol before reaching the minimum value, respectively. Aqueous and D2O solutions had similar effects on Tg. Selective studies of crystallinity evolution, ethanol sorption, degree of swelling, and Hansen solubility parameters of PLA were conducted. This work assists in developing PLA films intended for contact with aqueous-alcoholic solutions.