Synthesis and Properties of Thermoplastic Poly(vinyl Alcohol)-<i>Graft</i>-Lactic Acid Copolymers

Abstract

Poly(vinyl alcohol)-graft-lactic acid (PVA-g-LA) was synthesized by melt polycondensation of PVA and lactic acid using stannous chloride as a catalyst. The molecular structure of the copolymer was characterized by 1H NMR. The thermal properties of PVA-g-LA were investigated by differential scanning calorimetry and thermogravimetric analysis. The results showed that the PVA-g-LA copolymer exhibited lower glass transition temperature (Tg) and melting temperature (Tm) and higher decomposition temperature (Td) than pure PVA, and a difference of 60−80 °C between Tm and Td could be obtained, suggesting that the introduction of the oligo-poly(lactic acid) grafted chains can give rise to the melting flow processing of PVA. PVA-g-LA films prepared by compression molding at 140−150 °C had good flexibility and elasticity as well as water resistance. The copolymers have a potential application in food packaging.