Surface Modification Of Ultra High Molecular Weight Polyethylene Fibers And Properties Of Their Composites

With the rapid development of high-performance composite materials,ultra-high molecular weight polyethylene(UHMWPE)fiber-reinforced polymer composites have been used in many fields.Although UHMWPE fiber possesses outstanding properties like high strength and stiffness,chemical resistance,lightness and also good mechanical properties in cryogenic temperature,it has an inert surface and therefore produces poor adhesion toward polar polymeric matrices,such as epoxy resin,limiting its application.Therefore,in this paper,a combination of dopamine deposition and second function was proposed,aiming at improving the interfacial adhesion properties of UHMWPE fibers.Firstly,the oxidative self-polymerization of dopamine was used to surface modification of UHMWPE fibers.The results show that the surface of modified fiber coated with a uniform poly(dopamine)(PDA)layer and the surface roughness increases.Ultrasonic processing of the modified fibers shows that the PDA layer has strong adhesive force on the fiber.The results of monofilament breaking strength test show that the mechanical property of the fibers has no change after modified.When the concentration of dopamine was 2 mg/mL and the reaction time was 24 h,the interface shear strength of UHMEPE fiber and epoxy resin was maximum value(0.920 MPa),increasing by 28.31%compared with unmodified fiber.The dopamine modified UHMWPE fibers were put into the solution of second functionalization monomers of hexamethylene diamine(HMDA)and polyethylene imine(PEI)for further grafting,respectively.The results of FTIR and XPS show that HMDA and PEI were successfully grafted on the PDA layer of UHMWPE fibers,and the reactive functional groups were introduced in the same time.SEM figures show that the surface roughness of second functionalization modified fibers increased significantly.When the concentration of HMDA was 10mg/mL and the reaction time was 9h,the interface shear strength of UHMEPE fiber and epoxy resin was maximum value(1.310 MPa),increasing by 82.71%compared with unmodified fiber.Besides,when the concentration of PEI was 5 mg/mL and the reaction time was 24 h,the interface shear strength of UHMEPE fiber and epoxy resin was maximum value(1.185 MPa),increasing by 65.27%compared with unmodified fiber.Compared with the unmodified UHMWPE fibers reinforced epoxy resin composite materials,the tensile breaking strength of dopamine modified fibers reinforced epoxy resin composite materials has increased,.and after the secondary functional modified has further improved.The fracture of the composite cross section shows that the interface performance between the fiber and resin has improved,and stripping phenomenon seldom happens between fiber and resin.