The plasticizing mechanism and effect of calcium chloride on starch/poly(vinyl alcohol) films

Starch/poly(vinyl alcohol) (PVA) films were prepared with calcium chloride (CaCl2) as the plasticizer. The micro morphology of pure starch/PVA film and CaCl2 plasticized starch/PVA film was observed by scanning electron microscope. The interaction between CaCl2 and starch/PVA molecules was investigated by Fourier transform infrared spectroscopy. The influence of CaCl2 on the crystalline, thermal and mechanical properties of starch/PVA films was studied by X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, and tensile testing, respectively. The results indicated that CaCl2 could interact with starch and PVA molecules and then effectively destroy the crystals of starch and PVA. Starch/PVA films plasticized with CaCl2 became soft and ductile, with lower tensile strength and higher elongation at break compared with pure starch/PVA film. The water content of starch/PVA film would increase with the addition of CaCl2. This is an important cause of the plasticization of CaCl2 on starch/PVA film.