Influence of plasticizers on thermal properties and crystallization behaviour of poly(lactic acid) films obtained by compression moulding

Abstract

Neat and plasticized poly(lactic acid) (PLA) films were obtained by compression moulding. Three different plasticizers, at concentrations of 5 and 10%, were used: poly(ethylene glycol) (PEG) of 1000 and 4000 g mol−1 molecular weights and a commercial plasticizer, Palamoll®638. Crystallization behaviour and glass transition of PLA films were analysed using differential scanning calorimetry and X-ray diffraction. Films were also characterised in terms of structural, tensile, barrier and optical properties. The addition of the three plasticizers reduced the glass transition temperature (Tg) while promoting the crystallization of PLA in the compression-moulded films, depending on their type and concentration. PEG 4000 enhanced the crystallization more than PEG 1000 and Palamoll®638, the latter being that which induced the lowest degree of crystallization. The Tg value of the PLA amorphous phase was reduced by the addition of plasticizers, proportionally to their concentration. Nevertheless, all of the plasticized films exhibited similar elastic modulus and were less resistant to break and less extensible due to the greater induced crystallinity. PEG 4000 markedly reduced the film stretchability whereas this effect was less marked when Palamoll®638 was used. © 2016 Society of Chemical Industry.