Surface Modification Of Ultra-high Molecular Weight Polyethylene Fiber And Properties Of Its Rubber Matrix Composites

Ultra-high molecular weight polyethylene(UHMWPE) fibers were modified by chromic acid and potassium permanganate and the effects of surface modification were evaluated. The preparation of the bamboo-shaped fibers was achieved by liquid phase oxidation of the fiber surface followed by solution crystal growth technology. The mechanical properties of as-received,modified and bamboo-shaped UHMWPE fibers reinforced natural rubber(NR) composites were determined.(1) The UHMWPE fibers were modified by chromic acid and potassium permanganate, and the effects of the modifiers and technological parameters have been explored. FTIR and XPS were employed to character the change of oxygen-containing groups on the surface of the fibers; SEM was employed to show the changes of the surface morphology; MTS was employed to analysis the mechanical properties of the fibers; Contact angle measurement was employed to determinate the wettability of the fibers. The results show that the optimum modification conditions are: the chromic acid solution is prepared by mixing potassium dichromate, distilled water, and sulfuric acid in a 7:12:150 mass ratio, and then the chromic acid solution filled with a certain quality fibers was put into an ultrasonic cleaner to oxidize for 5min at 35oC; the potassium permanganate solution is prepared by mixing potassium permanganate and nitric acid in a 1:30 mass ratio, and then the potassium permanganate solution filled with a certain quality fibers was put into an ultrasonic cleaner to oxidize for 1min at room temperature.(2) Bamboo-shaped UHMWPE fibers were prepared using solution crystal growth technology.SEM was used to observe the surface morphology, distribution, spacing and size of the crystals on the fiber surface. The results show that the optimum crystallization conditions are: the fibers were treated by chromic acid solution for 5min at 35 oC, then the modified fibers were immersed in the HDPE-p-xylene solution at 91 oC for 20 h.(3) The NR matrix composites were prepared by adding the as-received, chromic acid modified and bamboo-shaped UHMWPE fibers. The influences of the surface treatment and fiber content on the composites were discussed. SEM was employed to show the fractured surface morphology of the composites; DMA was employed to analysis the adhesion property of UHMWPE fiber with rubber surface; MTS was employed to character the tensile strength and the tensile strength of the composites. The results show that when the amount of UHMWPE fiber added into the NR is same, the tensile strength,tear strength and hardness of the chromic acidtreated UHMWPE fibers/NR composites are optimal; when the type of fibers added into the NR is same, with the increase of the fiber content, the hardness of the UHMWPE fibers/NR composites increase and the tear strength of the UHMWPE fibers/NR composites increase at first then decrease.