表面改性对VGCF分散性质的影响

针对气相生长碳纤维极易团聚及与树脂基体界面结合能力较差的难题，采用双氧水-浓硝酸二步法对VGCF进行表面改性处理。利用X射线衍射仪、热重分析仪、傅立叶红外光谱仪、紫外可见分光光度计等测试分析了改性前后VGCF的表面结构和在溶剂中的分散性，并以形状记忆聚氨酯为基体，采用溶液混合法制备了气相生长碳纤维/形状记忆聚氨酯的复合材料，测试了复合材料的力学性能。经过改性后，VGCF的石墨晶型结构几乎没有改变，VGCF表面的含氧官能团浓度得到较大提高，且其在有机溶剂中的分散性及分散稳定性也得到很大提高；在气相生长碳纤维/形状记忆聚氨酯的复合材料截面中，扫描电镜观察表明表面改性使得VGCF在基体中的分散性及与基体的界面结合能力都得到一定程度的提高；经二步法改性处理后的气相生长碳纤维比未处理气相生长碳纤维对复合材料的力学性能的增强效果更为明显。

Effects of Surface Modification on the Dispersion Property of VGC

In view of the easy agglomeration issue of vapor grown carbon fiber (VGCF) and the poor interfacial adhesion between VGCF and matrix resin, two‐step surface modification with hydrogen peroxide and concentrated nitric acid was performed on VGCF. The surface structure and dispersion of VGCF before and after modification were tested and analyzed by XRD, TGA, FTIR, UV‐visible spectrum and SEM. Moreover, VGCF/SMPU composites were prepared via a solution mixing method taking shape memory polyurethane (SMPU) as matrix, and the mechanical properties of the composites were also tested. The graphite crystal structure of VGCF showed very little change after modification, the concentration of oxygen‐containing functional groups on the surface of VGCF was visibly increased, and the dispersion and dispersion stability of VGCF in organic solvent were also clearly improved. In the cross section of the VGCF/SMPU composites, the dispersion of VGCF in matrix and the VGCF‐matrix interfacial adhesion observed through SEM were both enhanced to a certain extent after surface modification. The two‐step surface modified VGCF had more obvious mechanical reinforcement effects on the composites than that of the pristine VGCF.