聚乙二醇对纤维素纳米晶体/聚羟基丁酸戊酸酯复合材料性能的影响

Effects of polyethylene glycol on the properties of cellulose nanocrystals/PHBV composites

为了探讨聚乙二醇(PEG)对纤维素纳米晶体(CNCs)/聚羟基丁酸戊酸酯(PHBV)复合材料性能的影响规律,采用熔融共混法制备了PEG-CNCs/PHBV复合材料。采用环境扫描电镜(ESEM)、DSC、偏光显微镜(POM)、TG、力学试验机表征了复合材料的界面形貌、结晶性能、力学性能。结果表明,PEG的加入使CNCs/PHBV复合材料的断面由光滑变得粗糙,断口凹凸不平;PEG-CNCs/PHBV复合材料球晶尺寸减小,球晶结构产生缺陷,熔融过程转变成两个熔融峰,熔融温度T_m从167.8℃下降到165.1℃,此外,PEG的加入增加了复合材料分子链的移动性,结晶变得困难,结晶度X_c从54.3%下降到50.2%,熔融结晶温度T_(mc)从99.8℃下降到73.5℃;PEG的加入提高了CNCs/PHBV复合材料的冲击强度和拉伸断裂伸长率,25wt%PEG添加量时,较纯PHBV最大增幅分别为56.4%和96.3%,但杨氏弹性模量和拉伸强度不断下降;PEG的加入使复合材料热解过程由一步热解转化成两步,25wt%PEG添加量时,第一步热解中的最快分解温度(T_(max1))从281.5℃上升到285.3℃;第二步热解中的最快分解温度(T_(max2))从371.5℃上升到394.3℃。因此,PEG的加入可以改善CNCs与PHBV界面相容性和结晶性能,从而提高CNCs/PHBV复合材料韧性、塑性和热稳定性。

In order to investigate the effects of polyethylene glycol（PEG）on the properties of cellulose nanocrystals（CNCs）/poly 3-hydroxybutyrate-co-3-hydroxyvalerate（PHBV）composites,polyethylene glycol（PEG）-CNCs/PHBV composites were prepared by the melt compounding method.The facture structure,crystalline properties,thermal stability,and mechanical properties of PEG-CNCs/PHBV composites were charactered by ESEM,DSC,POM,TG and material-testing machine,respectively.The results show that the cross section of CNCs/PHBV composites with the addition of PEG becomes rough and fracture suface becomes uneven.The addition of PEG make the spherulite sizes of PEG-CNCs/PHBV composites decrease,new spherulite structure defects emerge,and melting process transform into two melting peaks.The melt temperature Tm decreases from 167.8 ℃to 165.1 ℃.In addition,the addition of PEG enhances the mobility of PHBV molecular chain,thus the crystallization of PHBV becomes more difficult.The melt crystalline temperature Tmcof composites decreases from99.8 ℃to 73.5 ℃ and the crystallinity Xcdecreases from 54.3% to 50.2%.Compared with PHBV,the impact strength and tensile elongation at break of PEG-CNCs/PHBV composites keep increasing with the increase of PEGcontent,whose maximal promotion with 25wt% PEG are 56.4% and 96.3%,respectively,but the Young＇s modulus and tensile strength of PEG-CNCs/PHBV composites keep decreasing.Meanwhile the application of PEG improves the thermal stability of composite materials.The pyrolysis process of PEG-CNCs/PHBV composites transforms into two steps,and the fastest decomposition temperature（T（max1））in the first and second step increases from 281.5 ℃to 285.3 ℃,and from 371.5 ℃ to 394.3 ℃,respectively.The addition of PEG can improve the compatibilization and crystallinity between CNCs and PHBV,accordingly enhance toughness,plasticity and thermal stabilities of CNCs/PHBV composites.