Preparation and gas barrier properties of chitosan/silica organic–inorganic hybrid gas barrier membranes with cross-linked structure

Chitosan/silica organic-inorganic hybrid gas barrier membranes were prepared by sol-gel method on plastic films using tetramethoxysilane, 3-glycidoxypropyltrimethoxysilane, chitosan, and cross-linked structures of chitosan were introduced by cross-linking reaction using citric acid (CA) and malic acid (MA).Water vapor transmission rate (WVTR) of the membranes was evaluated by dish method.Oxygen permeation through the membranes was also measured by a variable-pressure method.WVTR of the hybrid layers were lower than that of poly(vinylidene chloride) (PVDC) and oxygen permeability coefficients of the hybrid layer was small and about one-third to half of that of PVDC.These properties were thought to be due to well dispersion of inorganic segments (silica) and organic segments (chitosan) at molecular level and the formation of cross-linked structures in the hybrid.Pencil hardnesses (750g load) of the hybrid layers coated on polyethylene terephthalate (PET) films were HB.These values were higher than that of PET film (B).Light transmittance of the chitosan/silica organic-inorganic hybrid gas barrier membranes (CA100 and MA110) coated on PET film were higher than PET film.The hybrid gas barrier membranes are transparent, rigid, flexible and have excellent water vapor and oxygen barrier properties.