【摘要】 通过碱解醇沉法从玉米芯中提取半纤维素,进而采用溶液共混流延法制备出不同比例的聚乙烯醇(PVA)/半纤维素共混膜,在此基础上加入通过硫酸水解脱脂棉制备的纤维素纳米晶(NCC),制备了NCC增强的复合膜.DSC、TGA、FTIR、SEM和薄膜拉伸等研究表明,复合膜的各组分间形成了氢键作用,相容性良好.在PVA/半纤维素共混膜中,半纤维素的加入大幅度提高了复合膜的断裂伸长率:当PVA与半纤维素质量比为3∶1时,复合膜的断裂伸长率高达380%,比纯PVA的140%增加了1.7倍,而拉伸强度仍能保持在较高的水平;纤维素纳米晶的加入,还可改善复合膜的韧性;半纤维素对PVA组分的结晶性能产生了影响,而刚性结构的NCC则对PVA的结晶起抑制作用.此外半纤维素和NCC的引入也提高了复合膜的热性能,使第二阶段分解速率峰的温度提高了约50℃.更多还原

【Abstract】 In order to extend the application of environmentally-friendly hemicelluloses as potential packing material,this article focuses on the preparation of high-performance polymeric films which is strong enough to protect contained product and to withstand mechanical stress during its application,transportation,and storage. Composite films based on polyvinyl alcohol( PVA) and hemicelluloses,extracted from corncob by alkaline hydrolysis and alcohol precipitation,were prepared using convenient and feasible solution casting.Furthermore,various amounts of nanocrystalline cellulose( NCC) prepared from cotton by using sulphuric acid hydrolysis were added to form enhanced composite films. Tensile test, differential scanning calorimetry( DSC),thermogravimetric analysis( TGA),infrared spectroscopy( IR) and scanning electron microscopy( SEM) were used to characterize the composite films. IR results showed that hydrogen bonding formed in blending components,which indicated good compatibility between them. DSC analysis showed that addition of hemicellulose within a certain range created a boost to the crystallinity of PVA,and addition of the rigid NCC showed an inhabiting effect to the crystallinity of the PVA component in the blend films. TGA results revealed that additions of hemicellulose and NCC also resulted in a 50 ℃ increase for the peak of the second-stage thermal decomposition,indicating a significant improvement for thermal resistance. Mechanical measurements showed that elongation at break of the PVA / hemicellulose composite films was increased to 380% at PVA /hemicellulose mass ratio of 3∶ 1,while the tensile strength was maintained at a reasonably high level( 50- 60MPa). It is thus obvious that there exists an increasement of toughness to the composite films. Moreover,low mass fraction of NCC( 0. 5%) has been found to improve the tensile strength of the PVA / hemicellulose blend film( PH1),while high mass fraction of NCC( 1%,3%,5%) contributed to improve elongation at break.更多还原