The Research Of Rheology Property And Barrier Property Of Chitosan Based Nanocomposite Coatings

In recent years, countries around the world pay more and more attention to environmental protection. The concept of “green packaging” was put forward and become a hot topic in the worldwide. “Green packaging” Can be understood in the way that it do no harm to natural environment and human beings, can be recycled and promoting sustainable development. It puts forward new requirements on energy saving, reducing packaging waste, recycling and biodegradability. Chitosan can be applied to coating on paper-based packaging materials because its non-toxic, antimicrobial properties, film forming and biodegradability. The new food packaging materials can be produced by combination with chitosan and layered silicate.In this paper, chitosan and layered silicate were the main research objects. The effects of chitosan/layered silicate nanometer composites on barrier performance and rheological properties of chitosan and chitosan/layered silicate nanocomposites were researched. Difference of rheological properties between two nano composites were compared and the effects of different DD of chitosan on the blocking performance were researched. The results showed that:(1)chitosan solution is a shear thinning fluid. The viscosity of chitosan solution increased with the increase of concentration and flow index was less than 1, classified as non-newtonian fake plastic type. The viscosity of chitosan solution reduced and flow index increase with the increase of concentration of acetic acid and performance of Newton was more obvious.(2)Chitosan/montmorillonite nanocomposite was also a shear thinning fluid. Its viscosity was lowest when dosage of montmorillonite was 12%. The viscosity of chitosan/montmorillonite nanocomposite decreased with the increase of stirring speed of MMT. But the viscosity of chitosan/clay nanocomposite increased with the increase of clay content. The viscosity of chitosan/clay nanocomposite was higher than that of chitosan/montmorillonite nanocomposite under the same addition of layered silicate. The viscosity of chitosan/clay nanocomposite increased with the increase of stirring speed of clay, appearing the phenomenon of “shear thickening”, contrary to the situation of montmorillonite. The rheological property of chitosan/montmorillonite nanocomposite was better than that of chitosan/clay nanocomposite under the same preparation conditions. Rheological property determined the smoothness of the coating and uniform distribution.AFM showed that the smoothness and the uniformity of chitosan/montmorillonite nanocomposite were superior to that of chitosan/clay nanocomposite so that the blocking performance of chitosan/montmorillonite nanocomposite was better than that of chitosan/China clay nanocomposite.(3)Chitosan applied in coating, SEM showed that a film on the surface of the base paper formed and covered the small pores, so that the smoothness was markedly improved. The smoothness and oxygen barrier performance of coated paper improved while WVTR changed little. The wet resistance and oxygen resistance performances of chitosan/montmorillonite nanocomposite coated paper significantly enhanced. The wet resistance of chitosan/clay nanocomposite coated paper had a small change range, but oxygen resistance performance had improved obviously, the effect was poor to chitosan/montmorillonite nanocomposite coated paper.(4)The d-space of chitosan/montmorillonite nanocomposite was larger than that of MMT. The d-space changed little but the surface area increased with the increase of DD of chitosan. WVTR of chitosan/montmorillonite nanocomposite coated paper decreased while OTR increased with the increase of DD of chitosan.