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BACKGROUND: Poor 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. RESULTS: The 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°. The SPF with diacetate glyceride exhibited the minimum water vapor permeability, which decreased by 39%. CONCLUSION: The 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. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

BACKGROUND: At present, most studies have focused on the preparation of modified starches by dry grinding. As an excellent starch plasticizer, water might enhance the action of grinding on the structure of starch granules, and water grinding might improve the gel properties of starch. Therefore, this article explored the influence mechanism of water grinding on the gel properties of corn starch based on the changes in its structure and properties. RESULTS: The results showed that water grinding could make water enter the starch granules and hydrate the starch molecules, and the starch gelatinized after water grinding for 20 min. Thus, water enhanced the action of grinding on the structure of the starch granules. Under the plasticization and grinding action of water grinding, the mechanochemical effect of the starch granules occurred. When the starch was in the aggregation stage (7.5–10 min), the crystallinity of the starch increased, and the starch molecules rearranged into a more stable structure, which increased apparent viscosity (η), elastic modulus (G′) and viscous modulus (G″) of the starch gels. CONCLUSION: Therefore, appropriate water grinding (10 min) contributed to increasing the viscoelasticity of starch gels. This study provided a theoretical foundation for research on improving the properties of starch by mechanical modification in future. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

The mechanism of the influence of organically modified montmorillonites (OMts) with different modification extents on starch/OMt nanocomposites was investigated. The nanostructures of OMts and their dispersion in starch films were analyzed using X-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. The modifier content in the OMts increased with an increase in the added amount and molecular weight of the modifiers. The highest d-spacing of 3.71 nm was achieved for the OMt modified with 30% dioctadecyl dimethyl ammonium chloride (DDAC). Intercalated nanostructures were formed between starch and the OMts modified with DDAC, whereas exfoliated nanostructures were formed between starch and the OMts modified with octadecyltrimethyl ammonium chloride (OAC) and octadecyl dimethyl benzyl ammonium chloride (ODBAC). The films with the OMt modified with 50% DDAC exhibited the highest tensile strength of 6.22 MPa. The water vapor permeability (WVP) of the film with the OMt modified with 30% DDAC exhibited a minimum value of 1.63 × 10−10 g · m/m2 · s · Pa. The amount and types of the modifiers in the OMts significantly influenced the structure and properties of the starch/clay nanocomposites. For a given polymer, the modification extent of Mt should be optimized to achieve high-performance nanocomposites. [ABSTRACT FROM AUTHOR]