纳米纤维素晶须的表面改性及其在环氧树脂中的应用

Surface Modification of Cellulose Nanowhiskers and Application in Epoxy Resin

以棉纤维素为原料,采用硫酸水解法制备了纳米纤维素晶须.以N,N-二甲基甲酰胺(DMF)为分散介质,二甲基氨基吡啶(DMAP)为催化剂,十二烯基琥珀酸酐为酯化剂对纳米纤维素晶须进行化学改性,得到了一系列取代程度不同的改性产物(记为DCNW).采用红外光谱(FTIR)、X射线衍射(XRD)、透射电子显微镜(TEM)和X射线光电子能谱(XPS)等手段对DCNW的结构和性能进行了分析和表征.选择表面取代度为0.3的改性产物作为复合材料的增强相.该改性产物能在丙酮中均匀分散和稳定悬浮,并且保持了改性前纳米纤维素晶须的棒状形态和高结晶度.将其分散于环氧单体中,通过浇铸法制备了纳米复合材料,考察了改性纳米纤维素晶须添加量对纳米复合材料拉伸性能、动态力学性能及耐湿热性的影响规律.结果表明,与空白环氧树脂相比,添加了改性纳米纤维素晶须的纳米复合材料的拉伸强度、杨氏模量和断裂伸长率都得到了提高.玻璃化转变温度、耐湿热性也得到了显著改善.其中,当改性纳米纤维素晶须的添加量为3.5%时,拉伸强度从纯环氧的39.85 MPa提高到72.33 MPa,增加了82%;杨氏模量增大了21%;断裂伸长率从纯环氧树脂的2.45%提高到7.29%,增加了198%;Tg值从纯环氧的103.4℃,提高到134.1℃;吸水率从1.9%下降到1.4%.

Cellulose nanowhiskers（ CNWs） were prepared through a sulfuric acid hydrolysis process with cotton linter as the raw material. Then CNWs were chemically modified with dodecenyl succinic anhydride（ DDSA） to obtain hydrophobic CNWs called DCNWs. The modification condition was optimized by varying the mass ratio of DDSA to CNW. The modification results were characterized by infrared spectroscopy（ FTIR）,Xray diffraction（ XRD）,transmission electron microscopy（ TEM） and X-ray photoelectron spectroscopy（ XPS）. The DCNWs with surface substitution degree of 0. 3 were chosen as fillers in the nanocomposites.Nanocomposites were prepared by incorporating different amounts of DCNW,pre-dispersed in a small amount of acetone,into an epoxy matrix. A strong interaction was observed between the DCNWs and epoxy matrix,as results of which the nanocomposites exhibited an obvious increase in Tgby about 30 K,simultaneous increases in tensile strength,Young＇s modulu and strain at break; and an improvement in hydrothermal properties. For example,compared with the neat epoxy,the nanocomposite containing 3. 5 wt% of DCNWs exhibited an increase in tensile strength by 82%,Young＇s modulus by 21%,and in strain at break by 198%. The Tgvalue increased from 103. 4 ℃ of neat epoxy to 134. 1 ℃,and the water uptake decreased from 1. 9% to1. 4%.