【作者】 戴达松；

【导师】 黄彪； 范毜仔；

【作者基本信息】 福建农林大学 ， 木材科学与技术， 2011， 博士

【摘要】 环境意识的增加,垃圾处理以及全球气候暖化问题使得各国政府不得不通过立法来加以约束。另一方面,来自于农业或木材产品中的可再生资源已成为一种新的工业产品或能源资源。从这些物质中提取出来的天然纤维目前广泛应用于各领域,如纺织,制浆造纸工业以及塑料工业。同时,随着纳米技术的发展,人们开始关注从天然纤维中制备纳米纤维。在本项目(研究)中我们始终关注大麻纳米纤维素的提取及其应用。通过新的纳米纤维素的制备方法,利用RSM对大麻纳米纤维素的制备实验进行设计,结果显示:当时间4 h,温度65 oC,润胀剂用量4-4.18%,氧化剂用量为60-62.29%,可以获得得率超过50%的纳米纤维素。NTA的测定,AFM、FEG-SEM的表面形貌观测相继证实,采用超声波/氧化降解的方法,经过条件的优化可以较好制备出纳米纤维素颗粒。尽管在降解过程中部分纤维素上C2,C3和C6的羟基会被氧化,但这些氧化并未对纳米纤维素的结晶指数造成负面影响,XRD的测定显示了采用超声波/氧化降解所制得的纳米纤维素同样具有较高的结晶度。不过DSC测定的结果则显示纳米纤维素的热稳定性弱于大麻纱线。研究大麻纤维的纳米纤维素改性时,对纤维的位错系统展开了研究。力学测定结果显示,经DTAB-纳米纤维素改性后大麻纤维的弹性模量、拉伸应变以及拉伸应力这三种力学性能参数的增加值在90.74～176.54%波动。通过FEG-SEM观测,清晰的观察到纳米纤维素对纤维的改性结果:纳米纤维素通过两种途径对大麻纤维进行“修复”,即(1)填充于大麻纤维中纤丝之间,或在纤丝之间部分形成薄膜而“修复”纤维,(2)通过填充大麻纤维的沟状条纹而实现对大麻纤维的“修复”。通过XPS研究,我们进一步推测纳米纤维素对于纤维的“修复”还可能通过羟醛缩合反应的方式对纤维进行修复。XRD的测定结果显示:较高的结晶指数出现在pH值为11-12,DTAB添加量在0.1左右的区域。界面的XPS研究显示:DTAB-纳米纤维素改性纤维后,能较好的提高纤维与树脂间的界面相容性。采用ATR-FTIR差谱分析技术对界面的研究进一步显示:这种相容性的提高可能是纤维通过酯化反应的方式对聚酯进行作用。环氧树脂的纳米纤维素复合研究时,DETA作为纳米纤维素的改性剂,采用高温和冷冻干燥方式对纳米纤维素进行改性。以DETA高温处理纳米纤维素为增强剂,研究了固化温度与纳米纤维素添加量对环氧树脂力学性能的影响,结果显示:当固化温度为130 oC,纳米纤维素添加量为0.035%时,复合物的力学性能最佳。采用DETA冷冻干燥处理纳米纤维素时,当DETA相对用量为50%时,复合物的力学性能最佳。用差示扫描量热法(DSC)分别测定了不同纳米纤维素用量与环氧树脂组成的固化体系在不同升温速率下的DSC曲线。分别采用KAS、Friedman、Málek数学模型计算了环氧树脂/纳米纤维素复合物的固化动力学参数。更多还原

【Abstract】 The increasing environmental awareness, growing global waste problems, and the global warming motivated governments around the world to increase the legislative pressure.Renewable resources from agricultural or forestry products form a basis for new industrial products or alternative energy sources. Natural-based fibres are used in a wide range of products such as textiles and geotextiles, special pulps and papers, reinforcement for polymers. As the development of nanotechnology, researchers pay much more attention on the fabrication of nanomaterials from natural fibres and their applications.In this present project (work), we focus on the extraction of nanocellulose from hemp fibres and the application of hemp nanocellulose for natural fibre modification and nanocomposite. We develop a novel method with couple outstanding advantages for the fabrication of nanocellulose. A central composite design (CCD) is applied using Design-Expert software to optimize the conditions of fabrication.The results show that the yield maximum amounts to more than 50% under the following conditions: time 4 h; temperature: 65 oC, dosage of swelling agent 4-4.18%; dosage of oxidant 60-62.29%. According to NTA (Nanoparticle Tracking Analysis), the mean size of nanocellulose can get around 100 nm. Characterized with AFM and FEG-SEM showsthat the dimension of nanocellulose is 3-dimensional system. ATR-FTIR shows that parts of the hydroxyl in C2, C3 and C6 are oxidized. But the oxidative reaction seems did not give rise to the decrease of CI. DSC determination shows that the thermal stability of nanocellulose is less then raw fibres.Dislocation also been investigated systematically by using ATR-FTIR and EDX during the second stage of research for the hemp fibres modification. Tensile testing shows that DTAB-Nanocellulose modification can increase the mechanical properties of hemp fibres significantly. FEG-SEM morphologies observation shows clearly that nanocellulose can modify the fibres by (1) filling in the interfibrillar gap or form thin film between fibrils and (2) filling in the stria on the surface of hemp fibres. XPS determination shows that nanocellulose may modify the fibres by aldol condensation. A higher CI can be got, when the pH Value is 11-12 and the dosage of DTAB is around 0.1%. XPS and ATR-FTIR are used to investigate the interfacial agehesion of polyester on the fibre. The interface between fibre and resin can be increased by the DTAB-Nanocellulose modification, this may be due to the esterifiable reaction. DETA is used to modify nanocellulose, and the results show that epoxy/nanocellulose nanocomposite can get a maximum of mechanical properties at the following condition: cure temperature 130 oC, dosage of nanocellulose 0.035%. Isothermal cure kinetics of epoxy/nanocellulose has also been investigated in present work. Three kinds of model are used to analysis the cure behavior of nanocomposite,更多还原