Characterization of Solid Surfaces by Free Energy Analysis

固体的表面自由能用张力法和反相气相色谱法测定。所用样品为玻璃纤维、碳纤维及其改性纤维，张力测定法是通过测量浸入液体中的纤维所受的张力，从而得到液体的接触角。利用双液体系，同时测定了纤维表面自由能的色散分量和纤维-液体间的非色散相互作用。后者与液体表面自由能的非色散分量的平方根呈线性关系，其斜率给出了纤维表面自由能的非色散分量.反相气相色谱法是基于测定几种探针分子在固定相（固体）上的保留体积，从而给出固体表面特性的信息.正构烷烃在玻璃纤维上的保留体积的对数与正构烷烃的C数或蒸汽压呈线性关系，由其斜率可导出表面自由能的色散分量。所获得的值与张力测定法测定的值相当。极性分子的保留体积往往偏离线性关系，这取决于它们与纤维的非分散相互作用的程度。碳纤维表面自由能的非色散分量在氧化过程中增加，在氢还原过程中减少，而色散分量几乎保持不变。碳纤维的极性（表面自由能的非色散分量/总表面自由能）与ESCA测得的表面[O]/[C]比呈线性关系。由表面自由能计算出的碳纤维与环氧树脂的粘接功与界面剪切强度之间存在较强的相关性。

The surface free energy of solids was determined by tensiometry and inverse gaschromatography. Samples used were glass fiber, carbon fiber and their modified ones.The tensiometry was based on the measurement of tension force worked on fibers immersed in liquids, which gives contact angle of liquids. By use of twoliquid system, dispersive component of surface free energy and nondispersive interaction of fiber-liquid were simultaneously determined. The latter was found to relate linearly with the square root of nondispersive component of surface free energy of liquids, and the slope gave the nondispersive component of surface free energy of fibers.The inverse gaschromatography was based on the measurement of retention volume of several probe molecules on the stationary phase (solid), which gives informations on surface characteristics of the solid. The logarithm of retention volumes of n-alkanes on the glass fiber changed linearly with the C number or vapor pressure of n-alkanes and the dispersive component of the surface free energy could be derived from its slope. The obtained values were comparable with those determined by tensiometry. Retention volumes of polar molecules tended to deviate from a linear relation depending on the degree of their nondispersive interaction with the fiber. The nondispersive interaction could be interpreted by acid-base interaction.The nondispersive component of the surface free energy of carbon fibers increased by oxidation and decreased by hydrogen reduction, while its dispersive component remained almost constant. The polarity (nondispersive component of the surface free energy / total surface free energy) of carbon fibers related linearly with the surface [O]/[C] ratio obtained by ESCA. There was a strong correlation between the work of adhesion of carbon fibers with epoxy resine calculated from obtained surface free energy and their interfacial shear strength.