Preparation and characterization of poly(vinyl alcohol)/poly(lactic acid) blends containing bio‐based plasticizers

The bio‐based plasticizers‐glycerol and lactic acid were used to plasticize and compatibilize PVA/PLA blends during melt blending process. It was confirmed that lactic acid significantly improved the compatibility between glycerol‐plasticized PVA and PLA. Compared with pure PVA, the melting and crystallization temperatures and crystallinities decreased but the crystal form of PVA in the blends was not changed. The thermal stabilities of PVA/glycerol (G)/lactic acid (L)/PLA blends were better than PVA/G/PLA blends. Compared to PVA/G/PLA blends, the tensile and tear strength of PVA/G/L/PLA blends were improved, however, elongation at break decreased. The water absorptions and water vapor permeances of the blends decreased with the addition of hydrophobic PLA, but they increased by incorporation of hygroscopic lactic acid. The surface resistivities of the blends augmented in combination with PLA but declined by adding lactic acid. The melt flow rates of PVA/G/PLA blends were better than PVA/G/L/PLA blends because lactic acid enhanced the interactions among the components. After the addition of lactic acid, the transmittances of the blends increased due to the refined dispersed phases by the compatibilization. The compatibility between the components was predicated by Hansen solubility parameters. These blends showed potential as a novel barrier material for food and medicine packages.

Highlights

PVA, glycerol, and PLA blends were compatibilized by lactic acid.