Microstructural Analyses of Biaxially Oriented Polylactide/Modified Thermoplastic Starch Film with Drastic Improvement in Toughness

Abstract This study presents microstructural regularization of biaxially oriented polylactide blended with a silane‐modified thermoplastic starch (BO‐PLA/mTPS) film, traced by X‐ray diffraction and scattering, and differential scanning calorimetry techniques. Interfacial adhesion improvement of mTPS favors PLA crystallization, and produces a large δ‐crystal (100–150 nm) with isotropic orientation when combining with BO stretching. High draw ratio (5 × 5), and BO stretching rate (75 mm s −1 ) lead to tight packing of PLA lamellae in both BO‐PLA/TPS and BO‐PLA/mTPS films, resulting in drastic toughness improvement (i.e., fivefold increases of Young's modulus and tensile strength, and threefold increase of elongation, as compared to those of the films without the BO process) with significantly decreased water absorption. However, the effect of reactive compatibility by mTPS on mechanical and water barrier properties is hindered by the BO process in which the V H ‐type patterns of TPS and mTPS are unclearly present, overlapped with (203) diffraction plane of PLA crystal, especially applying fast stretching.