芳纶纤维的热氧化处理及对环氧树脂界面黏结的影响

The Effect of Thermal Oxidation Treatment of Aramid Fiber on Interfacial Adhesion of Epoxy Fiber

采用红外光谱(FTIR)、热重(TG)、差示扫描量热(DSC)对芳纶纤维在N2和空气气氛下的热行为进行了研究,并以透射电镜(TEM)、界面剪切强度(IFSS)研究了芳纶纤维的空气热氧化处理及对其环氧树脂界面黏结的影响。结果表明:芳纶纤维在空气条件下,150~200℃温度范围内,仅仅是纤维表层上浆剂的挥发。250℃以上会出现分子链的氧化,同时纤维表层分子链能够重排使得氢键增强。高温过程中芳纶纤维的分子链苯环C—H被氧化成—C—OH、—COOH,从而使纤维表面极性增强。极性的结构有利于与环氧树脂的界面反应,使纤维与环氧树脂间形成40~50 nm的界面层。热处理后,芳纶纤维与环氧树脂微滴间界面剪切强度值增至18.05 MPa,与原丝相比增加了11.9%。同时,高温氧化后的芳纶纤维/环氧树脂界面黏合增强,复合材料的层间剪切强度为76.2 MPa,与原丝相比提高16.16%。

The thermal behavior of aramid fiber in N2 and air were studied by Fourier infrared spectroscopy(FTIR),thermogravimetry(TG) and differential scanning calorimetry(DSC), the thermal oxidation treatment of aramid fiber and its effect on the interfacial adhesion of aramid fiber and epoxy resin was investigated by transmission electron microscopy(TEM) and interfacial shear strength(IFSS). The results show that the volatilization of sizing agent on the surface of the aramid fiber is completed in the temperature range of 150~200℃ under air condition. At above 250℃, the oxidation of molecular chains occurs, and the rearrangement of molecular chains in the surface layer of fibers leads to the enhancement of hydrogen bonding. In the process of high temperature, the molecular chain benzene ring C—H of aramid fiber is oxidized into—CO—、—COOH, which enhanced the surface polarity of the fiber. The polar structure is conducive to the interface reaction with the epoxy resin, so that a 40~50 nm interface layer is formed between the aramid fiber and the epoxy resin. After heat treatment, the interfacial shear strength between the aramid fiber and the epoxy resin droplets increased to 18.05 MPa, which was an increase of 11.9% compared with the original fiber. At the same time, the interface adhesion of the aramid fiber/epoxy resin after high temperature oxidation is enhanced, and the interlaminar shear strength of the composites is 76.2 MPa, which is 16.16% higher than that of the original fiber.