Effects of co-plasticization of glycerol and small molecular esters on the physicochemical properties of extrusion-blown high-content starch/poly(butylene adipate-co-terephthalate) films

BACKGROUNDPoor mechanical and water barrier properties of starch-based films severely restrict their applications as packaging materials. In this study, glycerol was combined with various small molecular esters (SMEs) with different molecular structures to plasticize high-content starch/poly(butylene adipate-co-terephthalate) (80/20, w/w) films (SPFs) prepared by extrusion blowing. The effects of co-plasticization on the physicochemical properties and film-forming mechanism of SPFs were investigated. RESULTSThe addition of glycerides to SPFs reduced intermolecular interaction, increased molecular chain mobility, and decreased glass transition, melting temperatures, and crystallinity. Mechanical and water barrier properties of SPFs were improved significantly with the co-plasticization of glycerol and SMEs. The incorporation of triacetate glyceride increased tensile strength of SPFs by 54% and the water contact angle by up to 95 degrees. The SPF with diacetate glyceride exhibited the minimum water vapor permeability, which decreased by 39%. CONCLUSIONThe levels of hydrophilic/hydrophobic groups in SMEs and their molecular weights were essential for the plasticizing effects. Glycerides tended to infiltrate into starch for effective plasticization compared with citrates. The combination of glycerol and glycerides had better plasticizing effects on starch. (c) 2023 Society of Chemical Industry.