Abstract:Chitosan is a product of natural polysaccharide chitin with the partial acetyl group removed.Because of its unique physiological functions，it can meet many application requirements.However，because the water solubility of chitosan is not very high，the solubility is even lower when the physiological pH is less than 6.0.which limits its application in coating film preservation.In this study，chitosan was modified with chitosan quaternary ammonium salt，and its structure was characterized by Fourier transform infrared spectroscopy，1H-NMR spectroscopy，and X-ray diffraction.The mechanical properties of the coatings prepared by chitosan quaternary ammonium salt with different degrees of substitution were next investigated.Seven types of chitosan quaternary ammonium salt（HACC）/polyvinyl alcohol（PVA）composite membranes with different volume ratios were then prepared using a solution-blending method with chitosan as the raw material.The structure and performance of the composite coating were analyzed by Fourier infrared spectra，thermogravimetric analysis，scanning electron microscopy，water vapor transmittance analysis，and a mechanical property test.Finally，the best volume ratio of the composite membrane was obtained.Results revealed that the performance of the composite membrane was superior to those of the PVA and chitosan quaternary ammonium salt membranes.The tensile strength of the composite film was 16.52 MPa，the elongation at break was 56.55%，the crystallinity was 34.60%，the water vapor transmittance was 98.71 g/（m2·h），the maximum weight loss rate of the film was 83.20%，and the maximum weight loss rate temperature was 347.21℃.This study provides a theoretical reference for future research on chitosan modified membrane materials.