Effect of poly(vinyl alcohol)-g-poly(lactic acid) on the oxygen barrier performance of poly(lactic acid)-based film

In order to improve the oxygen barrier performance of poly(lactic acid) (PLA), a simple and economical melt blending method was chosen and poly(vinyl alcohol) (PVOH) with excellent oxygen barrier was used as the reinforcing phase to meet high oxygen needs. To improve compatibility, PLA was grafted onto PVOH through L-LA ring opening polymerization to get poly(vinyl alcohol)-graft-poly(lactic acid) (PVOH-g-PLA). The films with high oxygen barrier performance were prepared by blending PLA with PVOH-g-PLA. The structure of PVOH-g-PLA were characterized by FTIR and ¹H NMR, where 58 % -OH of PVOH grafted PLA and the average polymerization degree of the grafts was 8. The compatibility, crystallization, mechanical properties, and oxygen barrier performance of the blend films were studied. The results indicate that, compared with PVOH, PVOH-g-PLA has better compatibility with PLA. The PVOH-g-PLA separation phase size is <3 μm, whereas the of PVOH separation phase size is 15-40 μm. The oxygen permeability coefficient (P_O2) of PLA/PVOH-g-PLA decreases with PVOH-g-PLA. When the amount of PVOH-g-PLA reaches 15 %, P_O2 decreases to 1.10 × 10^-14 cm³·cm/(cm²·s·Pa), 38 % improvement in oxygen barrier compared to 1.77 × 10^-14 cm³·cm/(cm²·s·Pa) of neat PLA. These blends exhibited potential as a novel barrier material for food packages.