Carboxy-terminated hyperbranched polyester reinforced starch/chitosan composite film
In order to improve the mechanical and vapor barrier properties of starch/chitosan(SC)composite films,a series of starch/chitosan/HPC[SCH x,x%is HPC content(based on the mass of dried starch and chitosan,the same below]composite films were prepared by solution casting with carboxy-terminated hyperbranched polyester(HPC)as modifier,with the influence of HPC content on its properties analyzed.The SCH composite films obtained were then characterized by FTIR,XRD,SEM,DSC and TG,and further evaluated for their mechanical properties,thermal stability,water vapor permeability,hydrophobicity,vapor barrier properties,as well as antibacterial properties.The results indicated that,with HPC addition,the composite films showed generally an increase in the average thickness and density,improvement in tensile strength reduction in water vapor permeability,while no obvious change in elongation at break as well as the antibacterial property.SCH 2.50 exhibited the best mechanical properties,with the tensile strength increasing from 2.26 MPa to 3.58 MPa and the elongation at break decreasing from 151.04%to 146.40%.SCH displayed strong light absorption in the range of 280～320 nm,with the intensity increasing with the increment in HPC content.The water contact angle of SCH composite films ranged from 106.9° to 113.3°,showing overall strong hydrophobicity.Meanwhile,the water vapor permeability of SCH 2.50 decreased from 2.855×10-9 g·cm/(cm2·h·Pa)to 2.133×10-9 g·cm/(cm²·h·Pa).HPC and starch/chitosan formed a uniform and dense internal structure through hydrogen bonding and esterification,increased the surface roughness,and thus improved the mechanical properties and vapor barrier properties of SCH.
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