Study On Surface Modification Of Ultra-high Molecular Weight Polyethylene Fiber By Liquid Reagent Oxidation With Ultrasonic Wave Treatment

Ultra-high molecular weight polyethylene (UHMWPE) fiber, which is a linear chain structure of high orientation, is the third generation of high-performance fibers appearing following carbon fibers, aramid fibers. It can have a prospect used extensively in the fields of national defense, construction, medical treatment, aviation and navigation, etc. because of very low density, high-strength, high-modulus, excellent impact resistance and corrosion-resistance and so on.However, UHMWPE fiber and its composite have not been extensively applied in reality. Because the fiber is of chemical inertion, low surface energy, lack of polar groups, and highly symmetric methylene structure, the fiber has a high degree of crystallinity and orientation. On the one hand, it ensures that it has a high mechanical strength. On the other hand, it makes that its surface introduces chemical inertion, all focusing on the performance of low interfacial binding force of resin-based composite. It is therefore of necessity to solve this problem.In this paper, the surface of UHMWPE fiber was treated by chromic acid under ultrasonic processing. The processing parameters of influencing treatment were analyzed according to orthogonal experiment, and some factors are discussed respectively. Following conclusions were got: the temperature was main factor in effect of treating fiber, followed by time, solution preparation and ultrasonic frequency. The surface of fiber was just etched when the temperature was lower than 60℃, but introduced some polar groups when the temperature was higher than 60℃, and the adhesion was improved. Processing time was not the longer the better, because increased range of fiber's bonding strength became smaller and smaller with time's extension, and it tended to a certain value.In order to test the effect of fiber treatment, using SEM, FTIR, thermal behavior analysis and contact angle analysis, after treating the fibers, through the change of bonding strength between fiber and epoxy resin bonding strength and tensile strength of unidirectional LDPEAJHMWPE composite in vertical, horizontal, 45°off-axis direction, the best processing parameters of treating fiber were: solution preparation was K₂CrO₇: H₂SO₄: H₂O = 1:25:2, time was 5 minutes, temperature was 70℃, and ultrasonic frequency was 25KHz.UHMWPE fiber's bonding properties could be greatly improved by modification that fiber treated by chromic acid under ultrasonic processing, and then it would obtain heavy use in reality in the field of composites.