【作者】 潘虹；

【导师】 孙刚； 赵涛；

【作者基本信息】 东华大学 ， 纺织化学与染整工程， 2014， 博士

【摘要】 木质素是地球上一种储量十分丰富的可再生资源,产量大,再生速度快,可生物降解。合理开发和利用木质素,将其作为化工原料来代替日渐枯竭的石油资源,对人类社会的可持续发展具有十分重要的意义。碱木质素中含有大量酚羟基、醇羟基和羧基等多种基团,具有一定反应活性,可以代替有机化工原料应用于高分子材料合成领域。近年来,利用碱木质素改性制备高分子材料已引起了人们的兴趣。本课题首先对碱木质素进行降解提纯以提高木质素的反应活性；并以愈创木酚作为模型化合物对木质素改性的可能性进行了实验与理论研究；在此基础上,对碱木质素进行了环氧后胺化改性；并将合成的胺化木质素应用于环氧树脂的固化,对胺化木质素交联后的环氧树脂与未加入木质素的环氧树脂性能进行了对比研究。其中,将碱木质素采用环氧-胺化两步法改性并将其应用于固化环氧树脂是本文的一大创新点,主要研究内容与结果如下：一、碱木质素改性前的降解提纯以及结构性质确定：采用FTIR、UV、GPC和TGA等手段对实验所用碱木质素的结构和性质进行测试；使用钙镁复合固体碱降解碱木质素,并讨论了降解条件对降解后碱木质素分子量的影响；采用析出沉淀法对降解后碱木质素进行精制提纯。结果显示,实验用碱木质素分子结构中含有大量的羟基,醇羟基含量高于酚羟基的含量；经过降解和提纯处理后的碱木质素纯度有较大提高,总木质素含量由83.98%提高到97.04%,相对分子质量降低至1000以下,主要活性官能团总羟基、酚羟基和醇羟基由原来的6.88%、3.061%和3.819%转变为9.62%,3.524%,6.096%,酚羟基含量提高；降解提纯后的碱木质素仍然具有良好的热降解稳定性。二、木质素模型化合物的胺化改性：以愈创木酚作为木质素模型化合物,采用环氧-胺化两步法制备了带有活泼胺基的愈创木酚衍生物。通过FTIR、GC-MS以及NMR等手段对木质素模型化合物改性前后的分子结构进行测试,确定了目标产物的生成。对环氧、胺化反应机理的研究归纳以及模型化合物的成功改性表明,通过环氧-胺化两步法在木质素分子中引入活泼胺基是可行的。三、木质素胺化改性产物的合成：采用环氧-胺化两步法制备了带有活泼胺基的木质素衍生物,并探讨了反应条件对结果的影响,这是本文创新点之一。在环氧化步骤中,综合考虑产物的环氧值与转化率,得出反应适宜条件为：木质素中的羟基与环氧氯丙烷物质的量比为1：1.1,碱剂浓度12%,反应温度50℃,反应时间8h。胺化反应适宜条件为：环氧木质素中的环氧基与二胺化合物物质的量比是1：8,反应温度80℃,反应时间4h。胺化木质素的胺基显色反应为蓝紫色,为正反应,说明胺化木质素中含有大量一级胺基；FTIR和XPS测试结果确定了胺化木质素的生成；木质素胺化前后的元素分析结果显示,胺化木质素中引入了含量较高的氮元素；另外,热重分析结果显示,胺化木质素的最大降解速率发生在300℃以后,具有良好的热降解稳定性。四、胺化木质素固化双酚A型环氧树脂：将合成的胺化木质素作为固化剂固化双酚A型环氧树脂,也为本文创新之处。优化了固化工艺条件,分析了胺化木质素固化双酚A型环氧树脂的固化反应动力学,并且研究了胺化木质素的引入对不同粘度的两类双酚A型环氧树脂热性能、机械性能以及耐水性的影响。红外光谱显示,环氧树脂的环氧峰随固化反应时间的延长而降低并最终消失,证实了含有活泼胺基的胺化木质素可以与环氧基团发生反应；采用DSC非等温法对胺化木质素固化环氧树脂的固化动力学进行了研究,结果显示胺化木质素固化双酚A型环氧树脂的反应为中温固化的复杂反应,并选择100℃,180min作为双酚A型环氧树脂的恒温固化工艺条件。DMA测试了环氧树脂的玻璃化温度(Tg)和热转变温度(Td),TGA测试了材料的热降解过程,结果都显示胺化木质素的加入增强了环氧树脂的耐热稳定性；材料的机械强度随刚性分子-胺化木质素的加入而逐渐增加；吸水性测试结果显示,完全由W93固化的环氧树脂E51在720h后的吸水率为1.561%(加入稀释剂后的GCC135为1.973%),而被含50%胺化木质素的混合固化剂固化的环氧树脂E51则达到2.740%(加入稀释剂后的GCC135为2.584%),说明胺化木质素的加入使得环氧树脂材料耐水性略有降低,但影响不大。五、胺化木质素固化双酚F型环氧树脂：分析了将合成的胺化木质素作为双酚F型环氧树脂的固化剂使用的可能性,优化了工艺条件,探讨了固化反应动力学,并且研究了胺化木质素的引入对环氧树脂热性能、机械性能以及耐水性的影响。FTIR结果显示,由胺化木质素固化后的环氧树脂在910cm-1处的环氧峰完全消失并且出现了C-N峰,证实了含有活泼胺基的胺化木质素可以与环氧基团发生反应；采用DSC非等温法研究了胺化木质素固化双酚F型环氧树脂的固化动力学,选定90℃,90min作为双酚F型环氧树脂的恒温固化工艺条件。在此工艺下形成的环氧树脂,当胺化木质素含量少于60%时为均一透明的薄膜,SEM测试结果也显示胺化木质素与环氧树脂有良好的相容性。DMA测试环氧树脂的玻璃化温度(Tg)和热转变温度(Td),结果显示当胺化木质素在混合固化剂中含量增加到50%时,双酚F型环氧树脂的玻璃化温度上升了26℃,热转变温度提高了20℃。TGA实验结果显示胺化木质素固化的环氧树脂在300℃以前的质量损失仅为3.57%,而由W93固化的双酚F型环氧树脂则达到7.79%。拉伸强度测试结果表明,含50%胺化木质素的混合固化剂固化的双酚F型环氧树脂拉伸强度比未加木质素的环氧树脂增加了65MPa；双酚F型环氧树脂的耐水性能受胺化木质素的影响不大,完全由W93固化的双酚F型环氧树脂在720h后的吸水率为0.996%,而由含50%胺化木质素的混合固化剂固化的为1.319%。更多还原

【Abstract】 Second to cellulose, lignin is one of the most abundant renewable resources produced by plants. The application of this environmentally friendly biodegradable lignin resource of being as substitutes of dwindling petroleum oil based materials is an important aspect of sustainable development. Numerous reactive hydroxyl groups including both phenolic and aliphatic hydroxyl groups and carboxyl groups exist in lignin molecular. These structural features make lignin a potential source of preparing network materials. Synthesis of various functional derivatives from lignin has attracted increased attentions from researchers in recent years. In this paper, aminated derivatives of lignin containing a great quantity of primary amine and secondary amine groups were synthesized by a new two-step method after degradation and purification of lignin and feasibility study of amination reaction with a lignin model compound.With the existence of amino groups in the modified lignin, it was served as a curing agent of epoxy resins instead of a filler of the polymer materials. The main contents and conclusions of this paper are listed as follows:1Degradation, purification and characterization of alkaline lignin:Solid base catalysts MgO/CaO were used to catalyze degradation of lignin. Molecular Weight (MW) of the degradation products were reduced to below1000. An acid-precipitation method was used to remove the residual cellulose, inorganic salt, sugar and other impurities in original lignin material. After degradation and purification of the lignin, the purity of the lignin improved from83.98%to97.04%, total hydroxyl, alcoholic hydroxyl groups and phenolic hydroxyl increased from6.88%,3.061%and3.819%to9.62%,3.524%,6.096%respectively. Thermogravimetric analysis (TGA) result showed good thermal stability of the purified lignin.2Amination modification of a lignin model compound:guaiacol (GGA) was served as the model of alkali lignin. Aminated derivative of GGA was prepared from guaiacol, epichlorohydrin and diamine by a two-step epoxidation-amination method. The chemical structure of guaiacol and its derivatives were characterized by FTIR, GC-MS, and NMR. The results indicated that the target product was synthesized successfully. The investigation of amination reaction kinetics of the epoxidation compound with amine compound confirmed that introducing amine group into lignin molecules by this two-step method is feasible.3Synthesis of aminated lignin derivative:the aminated lignin possessing primary amine and secondary amine groups was synthesized through a two-step process, and the effects of reaction conditions on the target product have been discussed. At the first stage, epoxidation reaction of lignin was significantly affected by the alkaline condition and the dropping speed of epichlorohydrin. The proper synthesis conditions of epoxy lignin were achieved at50℃,8h, and with a ratio of hydroxy group to epichlorohydrin at1:1.1and NaOH concentration at12%. At the amination step, the proper reaction conditions were:80℃,4h, and with a ratio of epoxy group to amine group at1:8. In the qualitative amine color test, aminated lignin samples with different content of amine groups showed blue and blue-purple colors, visually proved the introduction of primary amine groups. The results of FTIR, XPS and the element analysis also confirmed that amine groups have been introduced into the structure of lignin and the amount of the incorporated amino groups was significant. The TGA revealed good thermal-mechanical performance of the products.4Curing the bisphenol A epoxy resin with aminated lignin:the aminated lignin was used as a curing agent of bisphenol A epoxy resin with different viscosity, the crosslinking reaction kinetics of the aminated lignin reacted with epoxy resin were investigated by using a non-isothermal method. The thermal stability, mechanical properties and water absorption of the epoxy resins cured by the aminated lignin were researched. The FTIR results proved the reactivity of the aminated lignin with the epoxy resin. The result of crosslinking reaction kinetics showed that the curing reaction was a complex curing reaction. The proper curing conditions were:100℃,180min. Both appearance features and scanning electron microscopy (SEM) images indicated that the aminated lignin had good compatibility with epoxy resins. In addition, the glass transition temperature (Tg), thermal deformation temperature (Td) and the thermo gravimetric analysis (TGA) results revealed that the epoxy resin had better thermal stability compared with ones cured by a common hardener. The mechanical properties of the epoxy resin cured by the aminated lignin were improved with the increase of content of the lignin due to the introduction of rigid molecule. The water absorption of epoxy resin E51contained the aminated lignin was2.740%(GCC135:2.584%) comparing with1.561%(GCC135:1.973%) without lignin, indicating that the addition of lignin slightly reduced the water resistance of the epoxy resin..5Curing the bisphenol F epoxy resin with aminated lignin:the possibility of using the aminated lignin prepared in this laboratory as a crosslinker of epoxy resin was explored. FTIR spectra confirmed that the synthesized aminated lignin could react with epoxy groups and serve as a hardener. Transparent and homogeneous epoxy resin films could be formed with less than60% of the aminated lignin in the hardener mixture after the resins were cured at following procedures:90℃,90min. Tg and Td of the epoxy resin cured by the aminated lignn individually increased26℃,20℃compared with the one without lignin. The Tg value of the epoxy resin was improved with the increase of post-cured temperature, time and the addition of the aminated lignin. The aminated lignin had a positive effect at the initial degradation stage of the epoxy resin. The mass loss of the epoxy resin cured by the aminated lignin before300℃was small around only3.57%while that of the one without the aminated lignin in the hardener system was7.79%. The results revealed that the thermal behavior of the epoxy resins was improved because of the introduction of the aminated lignin. Similar to bisphenol A epoxy resin, the mechanical properties of the bisphenol F epoxy resin cured by the aminated lignin were also improved with the increase of content of the lignin. The water absorption of bisphenol F epoxy resin cured by the aminated lignin was1.319%comparing with0.996%without lignin.The results showed that the aminated lignin containing a great quantity of primary amine and secondary amine groups could serve as a curing agent of epoxy resins.更多还原