端羧基超支化聚酯增强淀粉/壳聚糖复合膜

Starch/chitosan composite membrane reinforced by carboxy-terminated hyperbranched polyester

摘要:

为了提高淀粉/壳聚糖（SC）复合膜的机械性能和阻隔性能，采用端羧基超支化聚酯（HPC）为改性剂，通过溶液浇铸法制备了不同HPC含量（1.25%，2.50%，3.75%，5.00%, w/w, 以淀粉/壳聚糖干重计）的淀粉/壳聚糖/HPC复合膜（记为SCH），考察HPC加入对SC复合膜性能的影响。物理性能测试结果表明，HPC的加入整体上增加了复合膜厚度和密度，在明显提高复合膜膜拉伸强度同时可以很好的维持膜的断裂伸长率。其中，加入2.50%（g/g，以淀粉/壳聚糖干重计）的HPC，拉伸强度从对照组2.26 MPa增加到3.58 MPa，断裂伸长率没有明显降低（分别为151.04%和146.40%）。紫外-可见吸收结果显示，HPC的加入使得复合膜在280-320nm范围内产生强吸收，且吸收强度随着HPC加入量的增加而增加。通过FTIR、XRD、SEM、DSC和TG等综合分析发现，HPC与淀粉/壳聚糖之间通过氢键和酯化作用，形成了均匀致密的内部结构，增加了表面粗糙度和热稳定性；复合膜表面水接触角变化不大，整体呈现较强的疏水性（大于106°）。另外，HPC的加入降低了复合膜水蒸气透过率，2.50%HPC的加入使得蒸汽透过率从2.85降低到2.13 g·cm/cm2·h·Pa。

Abstract:

Aiming to improve the mechanical and barrier properties of starch/chitosan composite films, different content of carboxyl-terminated hyperbranched polyester (HPC) (1.25%, 2.50%, 3.75%, 5.00%, w/w, based on the dry weight of starch and chitosan) was introduced to prepare starch/chitosan/HPC composite films (labeled as SCH). Results from physical performance tests indicate that the inclusion of HPC increases the thickness and density of the composite films, notably enhancing tensile strength while maintaining fracture elongation of the films. Addition of 2.50% (based on the dry weight of starch/chitosan) HPC elevates the tensile strength from 2.26 MPa in the control group to 3.58 MPa, with no significant reduction in fracture elongation (measuring 151.04% and 146.40% respectively). UV-visible absorption outcomes reveal that the introduction of HPC induces strong absorption within the 280-320nm range, with absorption intensity increasing with higher amounts of added HPC. Through comprehensive analysis techniques including FTIR, XRD, SEM, DSC, and TG, it was revealed that strong intermolecular force forms between HPC and starch/chitosan through hydrogen bonding and esterification, resulting in a uniform and dense internal structure, increasing surface roughness and thermal stability. The change in water contact angle on the composite film"s surface is minimal, exhibiting an overall hydrophobic nature (greater than 106°). Additionally, the inclusion of HPC reduces the water vapor permeability of the composite film; the addition of 2.50% HPC decreases vapor permeability from 2.85 to 2.13 g·cm/cm2·h·Pa.