Preparation and characterization of crosslinked starch films pretreated with sodium hydroxide/amide/water solvent system

Abstract

Potato starch (PS) was pretreated with a sodium hydroxide (NaOH)/amide/water solvent system, epichlorohydrin (ECH) was then added to the solution to form a crosslinked molecular network, and a crosslinked starch-polyvinyl alcohol film (SPF) was successfully fabricated after the incorporation of polyvinyl alcohol (PVA). SPF prepared from different solvent systems was characterized via scanning electron microscopy (SEM), infrared spectroscopy (IR), X-ray diffraction (XRD), thermogravimetry (TG) and differential scanning calorimetry (DSC). SPF from the NaOH/urea/formamide solvent system (SPF-UF) exhibited the most homogeneous cross-section with high crystalline intensity and thermal stability. The highest transmittance (75.16 %) and contact angle (83.5°) of SPF-UF also claimed the prominent compatibility between the crosslinked starch and PVA, partly proving the existence of the synergistic effect within the NaOH/urea/formamide solvent system, which had caused dramatic destruction of the internal hydrogen bonds of PS. In this work, the NaOH/urea/formamide solvent system as a novel system was applied to dissolve PS, to achieve the preparation of SPF with high compatibility and excellent properties, which would be more conducive for the application of this film in packaging and many other aspects.