【作者】 张浩；

【导师】 蒲俊文；

【作者基本信息】 北京林业大学 ， 林产化学加工工程， 2014， 博士

【摘要】 本论文利用催化乙醇法分离获得高纯度木质纤维素,并与酸水解等手段结合制备纳米结晶纤维素(NCC),然后用硅烷偶联剂接枝改性NCC以提高其分散性并制备复合材料,通过对复合材料结构和性能的表征研究其改良机理。含有4-甲基-2-戊酮、二甲亚砜和甲酸的新型催化剂体系导致传统乙醇法的木质纤维素提取分离温度显著降低,可在130℃条件下分离获得高纯度、高结晶度的纤维素样品,在与酸水解法等配合使用后可初步实现以木片为原料的NCC连续生产工艺。利用FT-IR、XRD、TG、DSC(?)口TEM等对以催化乙醇法分离纤维素为原料制备的NCC进行表征后发现落叶松NCC的聚合度高、结晶结构致密而且失重温度比毛白杨NCC高5.1%,也表现出较均一的外观形态；利用硅烷偶联剂改性落叶松NCC以改善其疏水性能,并与脲醛树脂、丙烯酸酯涂料、聚氨酯水性木器漆和酚醛树脂制成复合材料,研究改性剂种类、NCC用量等因素对复合材料结构和性能的影响规律,结论如下：将经过3-氨丙基三乙氧基硅烷(APTES)和3-甲基丙烯酰氧基丙基三甲氧基硅烷(MPS)改性的NCC与脲醛树脂复配制成复合材料,APTES改性NCC与脲醛树脂基材间的接触角下降了26.4%,而MPS改性NCC与脲醛树脂基材间的接触角下降了24.1%。经过APTES改性处理的NCC具有较强的物理和化学吸附能力,导致胶合板的游离甲醛释放量下降53.2%,而MPS改性NCC的添加仅使游离甲醛释放量下降21.3%；添加改性NCC对纤维板游离甲醛释放量的改善效果不明显。通过形成稳定的交联网络结构,APTES改性NCC使胶合板的内结合强度提高了23.6%,而MPS改性NCC使胶合板的内结合强度仅提高7.0%;APTES和MPS改性NCC的添加使得纤维板的抗弯强度分别提高了46.1%和35.7%。利用3-(2,3-环氧丙氧)丙基三甲氧基硅烷(GPTMS)(?)口3-甲基丙烯酰氧基丙基三甲氧基硅烷(MPS)改性的NCC与丙烯酸酯涂料复配制成复合材料,两种改性剂分别导致NCC与丙烯酸酯基材间的接触角下降22.8%和19.6%。添加了GPTMS改性NCC的丙烯酸酯复合材料镜面光泽度提高了33.3%,明显高于MPS改性NCC；利用GPTMS改性NCC与丙烯酸酯制成的复合材料耐磨性提高59.4%,而经过MPS改性的NCC对复合材料耐磨性的改善效果为45.3%；NCC改性剂的不同种类对丙烯酸酯复合材料铅笔硬度的影响较小；改性NCC对复合材料水分吸收率的影响明显强于乙醇吸收率。分别以3-氨丙基三乙氧基硅烷(APTES)和3-(2,3-环氧丙氧)丙基三甲氧基硅烷(GPTMS)为改性剂处理NCC,并将改性NCC添加到聚氨酯水性木器漆中复配。相比GPTMS改性NCC,经过APTES改性的NCC表面疏水性基团的接枝率更高、其在木器漆基材中的分散状态也更加均匀,而且改性NCC的结晶结构相对稳定。分析APTES改性NCC/水性木器漆复合材料的性能可知表面改性NCC的添加导致复合材料的耐黄变性能比对照组提高超过50%,镜面光泽度的增强达到164.8%,复合材料的力学性能也得到明显改善。利用3-(2-氨乙基)-氨丙基甲基二甲氧基硅(MCPS)和3-甲基丙烯酰氧基丙基三甲氧基硅烷(MPS)改性NCC复配酚醛树脂。相比MPS,MCPS改性导致NCC疏水性能提高更加明显。通过NCC晶须与酚醛树脂分子链间形成的共价键或者氢键连接使基材的机械性能得到明显改善：MCPS改性NCC导致酚醛树脂复合材料的抗张强度和抗弯强度分别增强155.5%和23.8%,显著高于MPS改性NCC；但是NCC的表面改性剂种类对复合材料冲击强度的改善效果影响较小。更多还原

【Abstract】 The cellulose of wood was separated by the catalytic ethanol in this paper and the nano crystalline cellulose (NCC) was prepared by acid hydrolysis with the separated cellulose. The silane coupling agent was able to improve the hydrophobic property of NCC. The surface-modified NCC was used to synthesize composites and the mechanism was studied.The new catalyst system containing4-methyl-2-pentanone, dimethyl sulfoxide and formic acid was able to decrease the temperature of separation of cellulose. The maximum temperature of the separation process was130℃and the separation process combined with acid hydrolysis was able to produce the NCC with wood chips continuously. NCC produced with the separated cellulose was characterized by DP, FT-IR, XRD, TG, DSC and TEM, and the results showed that the NCC from larch was more steady and uniform than that from poplar. The NCC modified by silane coupling agent was used to synthesize composites with urea-formaldehyde resin, acrylic resin, waterborne polyurethane and phenolic resin. The improvements of the composites resulted from the silane coupling agents and the contents of NCC were studied and the results were summarized as follows:NCC modified by APTES and MPS was used to synthesize composites with the urea-formaldehyde resin. Compared with the control group, the contact angle between APTES-modified NCC and urea-formaldehyde resin was decreased by26.4%, while the contact angle of MPS-modified NCC was reduced by24.1%. The prominent physical adsorption and chemisorptions of NCC modified by APTES led to a53.2%reduction of the free formaldehyde in plywood, which was more than the reduction resulted from the MPS-modified NCC. The improvements resulted from modified NCC in fibreboard were inconspicuous. With the formation of crosslinked network, the bonding strength of plywood with APTES-modified NCC was improved by23.6%and the improvement led by NCC modified by MPS was7.0%. The bending strength of fibreboard was enhanced by46.1%and35.7%with the additions of APTES and MPS modified NCC, respectively.GPTMS-modified NCC and MPS-modified NCC were synthesized composites with acrylic resin, and the surface-modifcations resulted in the22.8%decrease and19.6%decrease of the contact angles of NCC particles, respectively. The specular gloss of composite with GPTMS-modified NCC was improved by33.3%, which was more obvious than that with NCC modified by MPS. The abrasive resistance of acrylic resin with GPTMS and MPS-modified NCC was enhanced by59.4%and45.3%. The pencil hardness of the composites was affected by the surface modifiers of NCC inconspicuously, and the water absorption rate of the composites was affected by the modified NCC more significantly than the ethanol absorption rate.APTES and GPTMS-modified NCC were used to prepare the composites with waterborne polyurethane. The grafting ratio of APTES-modified NCC was more than that of the NCC modified by GPTMS, and the crystal structure of well-dispersed APTES-modified NCC was destroyed. Taked the case of APTES-modified NCC/waterborne polyurethane composites, the anti-yellowing property of the composites were improved by more than50%and the specular gloss was enhanced by164.8%. Mechanical properties of the composites were improved by the APTES-modified NCC significantly.MCPS and MPS were treated as the modifiers of NCC, and the composites were synthesized with the two kinds of modified NCC and phenolic resin. Compared with MPS, MCPS led to the great improvement of the hydrophobicity of NCC. For the covalent bonds and hydrogen bonds between NCC and phenolic resin, the tensile and bending strengths of composites with MCPS-modified NCC were improved by155.5%and23.8%, which were more than the improvements of composites with NCC modified by MPS. The impact strength of the composites was affected by the modifiers inconspicuously.更多还原