Preparation And Properties Of LLDPE/Chitosan Electret Blend Films For Packaging

Chitins exist widely in shells of creatures and the cell walls of fungi. Chitosan is N-deacetylation product which comes from chitin. In recent years, many applications of chitosan have attracted wide attention, including biodegradability, biocompatibility, antibacterial activity and preservative capacity. Because of the good mechanical properties of linear low density polyethylene and the easy polarization and wide antimicrobial properties of chitosan, LLDPE/chitosan blend packaging films were prepared. The main contents are as follows:(1) Chitosan was dissolved in acetic acid aqueous solution, making chitosan precipitated with sodium sulfate. LLDPE-g-AA was treated as compatibilizer. Then tensile properties, crystallizations and rheological properties of LLDPE/LLDPE-g-AA/chitosan blends were studied respectively. As the chitosan content increased, the tensile properties of the blends deteriorate. Although chitosan has little influence on the melting temperature and crystallization temperature of the blends, crystallinity was reduced. Rheological tests show that the blends accord with "shear thinning" law of the non-Newtonian fluid.(2) Chitosan was cross-linked by glutaraldehyde (as a cross-linking reagent). And chitosan was modified with five kinds of monomers (octanal, nonanal, decanal, cinnamic aldehyde and p-dimethylaminobenzaldehyde) to form Shiff base. The chemical structures of chitosan derivatives were characterized by FTIR and 1H-NMR. LLDPE/chitosan derivative blends were prepared.(3) The water vapor permeabilities of LLDPE/LLDPE-g-AA/chitosan blends and LLDPE/chitosan derivatives were investigated. Due to hydrophilicity of chitosan, the permeability coefficients of blends films were higher than LLDPE film. When the content of chitosan and its derivatives is 15%, the water vapor permeability is highest.(4) The effects of different groups of chitosan derivatives on dielectric properties and the surface potential were investigated. With the increasing of chitosan and its derivatives, the dielectric constants and loss tangents of the blends increase. But chitosan derivative content reached at 20%, the dielectric constant decreased slightly. The surface potential was measured. The charge content on the surface of blend films decayed rapidly in a short time, and then stabilized. The longer films were charged, the higher the values of surface potential are.(5) Samples acted on E.coli respectively, then the bacteriostasis of the samples were observed. The LLDPE/LLDPE-g-AA/chitosan blends have no significant bacteriostatic effect toward E.coli. Among LLDPE/chitosan derivatives blend films, the bacteriostatic effect of LLDPE/cinnamic aldehyde-chitosan schiff base blends is best. When the content of cinnamic aldehyde-chitosan schiff base is 20%, the blend has the highest bacteriostatic rate toward E.coli, reaching 60.88%, and the difference between the blend and LLDPE is 35.54%.