电化学处理程度对碳纤维结构及性能的影响

采用质量分数为5%NH4HCO3溶液对聚丙烯腈(PAN)基碳纤维进行不同程度的电化学处理。采用X射线光电子能谱(XPS)和拉曼光谱(Raman)表征电化学处理前后碳纤维表面化学成分和表面微观结构的变化规律。将碳纤维样品与环氧树脂制成复合材料,探究该复合材料的层间剪切强度(ILSS)。研究结果表明:经过3组电化学处理后,碳纤维表面含氧官能团增多、表面有序度下降、复合材料的ILSS提高1.94倍;继续经过3组电化学处理,碳纤维表面含氧官能团下降、表面有序度回升、复合材料的ILSS提高1.53倍;纤维表面含氧官能团含量越多,纤维的结构破坏程度越低,碳纤维/环氧树脂复合材料的ILSS越高。在大规模电化学处理碳纤维过程中,选择3组电化学处理碳纤维,既能大幅度改善碳纤维表面活性,又不会严重影响碳纤维的表面结构。

Effects of electrochemical treatment on the structures and performances of carbon fibers

Polyacrylonitrile (PAN)-based carbon fibers have been subjected to different degrees of electrochemical oxidation in ammonium bicarbonate aqueous solution (mass fraction of 5%) in order to optimize their properties for industrial production. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy were used to characterize the surface chemical composition and surface microstructure of the carbon fiber. Carbon fiber/epoxy resin composites were prepared and their interlaminar shear strengths (ILSS) were measured. The results revealed that after three cycles of electrochemical treatment, the concentration of oxygen functional groups on the carbon fiber surfaces increased, the degree of surface order slightly decreased, and the ILSS of the composites increased 1.94 times. After three further cycles of treatment, the content of oxygen functional groups decreased, the degree of surface order was restored, and the ILSS of the composites increased only 1.53 times. It was found that increasing the quantity of surface oxygen functional groups and lowering the degree of damage to the fiber structures resulted in higher ILSS values for the carbon fiber composites. Three cycles of electrochemical treatment converted the surface of the carbon fibers from inert to active without seriously destroying their surface structure, which makes them suitable for use in industrial production.