Preparation and Rheological Behaviors of Thermoplastic Poly(vinyl alcohol) Modified by Lactic Acid

A thermoplastic modified poly(vinyl alcohol) (PVA-g-LA) with improved melt processing property was prepared by melt polycondensation of PVA with lactic acid. Rheological behaviors of PVA-g-LA copolymers were investigated using a high-pressure capillary rheometer. The influences of the content of oligo-poly (lactic acid) graft chains and content of PVA-0588 on the theological properties of PVA-g-LA copolymers were researched. The rheological parameters including non-Newtonian index and the viscous flow activation energy were analyzed and evaluated. As predicted, the PVA-g-LA samples exhibited noticeable shear thinning behavior. The apparent viscosity, the viscous flow activation energy, and the non-Newtonian index of PVA-g-LA showed obvious correlation with the PLA grafting chain content and PVA-0588 content at a constant temperature and shear rate. Both the increase of the content of oligo-PLA graft chains and content of PVA-0588 with PVA-1799 can improve the melting flow processing of PVA-g-LA copolymer.