Synthesis and Properties of Thermoplastic Poly(vinyl Alcohol)-Graft-Lactic Acid Copolymers

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 H-1 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 (T-g) and melting temperature (T-m) and higher decomposition temperature (T-d) than pure PVA, and a difference of 60-80 degrees C between T-m and T-d 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 degrees C had good flexibility and elasticity as well as water resistance. The copolymers have a potential application in food packaging.