【作者】 刘晓辉；

【导师】 具本植； 鄢冬茂；

【作者基本信息】 大连理工大学 ， 化学工程（专业学位）， 2022， 硕士

【摘要】 纤维素作为一种自然界中最为丰富的天然有机高分子材料,具有取之不尽用之不竭的优点。通过将纤维素中的非结晶区去除保留结晶区可以制备纳米纤维素,纳米纤维素具有优异的特性,如可再生性、生物降解性、生物相容性,在人们的日常生活中具有巨大的应用潜力。本文通过乙二醇醇解法分别从滤纸和天然花生壳中成功制备出了纤维素纳米晶和纤维素纳米纤维,并将两种纳米纤维素进行改性添加到聚乳酸中制备纳米复合材料以增强聚乳酸的力学性能。本文首先以滤纸为原料,用对甲基苯磺酸作催化剂,乙二醇作溶剂,在一定条件下去除非结晶区保留结晶区制备出了纤维素纳米晶,去除的非结晶区与乙二醇反应生成了乙二醇葡萄糖苷,并对反应条件进行简单的优化,对产物进行了表征。通过与其他几种有机酸、无机酸对比,对甲基苯磺酸制备的纤维素纳米晶的产率和结晶度相对较高,分别为63.8%和71.2%,反应前后晶型结构未发生改变,仍为纤维素Ⅰ型。SEM显示所制备的纤维素纳米晶形貌较好,直径为30-60 nm,长径比大于10。通过FTIR、LC-MS对副产物乙二醇葡萄糖苷进行了确认。在上述研究基础上,研究以天然花生壳为原料、对甲基苯磺酸为催化剂,利用乙二醇可以在高温下抽提木质素的特性,直接制备纤维素纳米纤维,并对反应条件进行了优化,对产物进行了表征。实验结果表明,所制备的纤维素纳米纤维产率为25%,结晶度为64.1%,SEM和TEM分析表明尺寸宽约15-30 nm,长径比大于50,形貌较好。反应前后晶形结构并未发生改变,仍为纤维素Ⅰ型。设计了相关实验验证乙二醇在酸解花生壳制备纤维素纳米纤维的过程中发挥了关键作用,通过FTIR对乙二醇高温抽提物进行了表征。最后,将制备出的纤维素纳米晶和纤维素纳米纤维进行乙酰化改性,通过FTIR对其进行表征,并添加到聚乳酸中制备聚乳酸纳米复合材料,对其进行力学性能测试,探讨乙酰化纳米纤维素的取代度和添加量对复合材料力学性能的影响,并与未乙酰化改性的纳米纤维素/聚乳酸纳米复合材料进行对比。试验结果表明,乙酰化改性大大提高了纳米纤维素在聚乳酸中的分散性,加强了与聚乳酸的界面相容性,当乙酰化纤维素纳米晶和乙酰化纳米纤维的添加量分别为4%和2%,复合薄膜拉伸强度分别增加到39.1 MPa和37.1 MPa,较纯PLA薄膜分别提升38.1%和25.1%。更多还原

【Abstract】 As one of the most abundant natural organic polymer materials in nature,cellulose has the advantage of being inexhaustible.Nanocellulose can be prepared by removing the amorphous region of cellulose and preserving the crystalline region.Nanocellulose has excellent properties,such as reproducible,biodegradability and biocompatibility,and has great application potential in people’s daily life.In this paper,cellulose nanocrystalline and cellulose nanofibers were successfully prepared from filter paper and natural peanut shell by alcoholysis with ethylene glycol,respectively.Two kinds of nanocellulose were modified and added into polylactic acid to prepare nano-composites,which enhanced the mechanical properties of polylactic acid.In this paper,we first used filter paper as raw material,p-methylbenzenesulfonic acid as catalyst,glycol as solvent,removed the amorphous region and retained the crystalline region to prepare cellulose nanocrystals.The removed amorphous region was reacted with ethylene glycol to produce ethylene glycol glucoside.The reaction conditions were simply optimized and the product was characterized.Compared with other organic and inorganic acids,the yield and crystallinity of the cellulose nanocrystalline prepared with p-methylbenzenesulfonic acid were 63.8% and 71.2%,respectively.The crystalline structure of the cellulose nanocrystalline had not changed before and after the reaction,and was still cellulose type I.SEM showed that the morphology of cellulose nanocrystals was good,with a diameter of 30-60 nm and an aspect ratio of more than 10.The byproduct ethylene glycol glucoside was confirmed by FTIR and LC-MS.On the basis of the above research,the cellulose nanofibers were directly prepared by using natural peanut shell and ethylene glycol as raw materials and catalyst respectively,and the properties of ethylene glycol that could extract lignin at high temperature were utilized.The reaction conditions were optimized,and the products were characterized.The results showed that the yield and crystallinity of the prepared cellulose nanofibers were 25% and 64.1%.SEM and TEM analysis showed that the size was about 15～30 nm,the aspect ratio was more than 50,and the morphology was good.The crystal structure did not change before and after the reaction,and there was still cellulose type I.Experiments were designed to verify that ethylene glycol played a key role in the preparation of cellulose nanofibers from peanut shells by acid hydrolysis.The high temperature extract of ethylene glycol was characterized by FTIR.Finally,the cellulose nanocrystals and cellulose nanofibers were acetylated and characterized by FTIR.They were added to polylactic acid to prepare polylactic acid nanocomposites and their mechanical properties were tested.The effect of the degree of substitution and the amount of acetylation nanocellulose on the mechanical properties of the composites was investigated,and the comparison was made with the non-acetylation nanocellulose/polylactic acid nanocomposites.The results showed that acetylation improved the dispersibility of nanocellulose in polylactic acid and enhanced the interface compatibility with polylactic acid.When the amount of acetyl cellulose nanocrystals and acetyl cellulose nanofibers is 4% and 2%,the tensile strength of the composite film increased to 39.1 MPa and37.1 MPa,respectively,which was 38.1% and 25.1% higher than that of pure PLA film,respectively.更多还原