Antifriction Modification And Application Research Of Polyurethane Sealing Washer

Polyurethane has been widely used in sealing materials on account of its excellent abrasion resistance and elasticity, Much frictiona heat will be produced because of its weak self-lubrication and high friction coefficient when it is applied to arge-scale sealing installations, then seals are worn down. In the arge-scale sealing installations with high speed operation, the seals will be squeezed out due to its high friction coefficient, then the accident may occur. This study would prepare millable polyurethane with low friction coefficient by using low friction coefficient of ultra-high molecular weight polyethylene(UHMWPE), but their polarity are different, so the compatibility between MPU and UHMWPE is poor. In order to solve the problem of the compatibility, the study would start from two respects: adding compatilizer and modifying UHMWPE.The paper prepared maleic anhydride grafted onto low density polyethylene(LDPE-g-MAH) and acrylic acid grafted onto low density polyethylene(LDPE-g-AA) by introducing maleic anhydride(MAH) and acrylic acid(AA) into low density polyethylene, by means of solution grafting, and used them as compatibilizer into the MPU/UHMWPE blend system. The Fourier transform infrared spectrometer(FTIR), the tension meter have been applied to character the grafting results, the coefficient of friction/stripping tester and wear tester and so on have been applied to test the tribological properties and the mechanical properties of the blend. The results show that when the w(MPU):w(UHMWPE):w(PE-g-MAH):w(DCP)=100: 15: 8: 0.05, now the friction coefficient of modified polyurethane reduced by 43%, the wear rate reduced by 87%, the tensile strength increased by 28%.The paper also prepared polyurethane grafted onto low density polyethylene(LDPE-g-PU) with MAH and AA as intermediates by introducing isocyanate(NCO)terminated polyurethane into LDPE-g-MAH and LDPE-g-AA by means of sequential grafting polymerization, and used them as compatibilizer into the MPU/UHMWPE blend system. The changes of tribological properties, mechanical properties, melt and crystalline behavior of the blend with different kinds of LDPE grafted products as compatibilizer were assessed. The results show that LDPE-g-PU as compatibilizer could further improve the compatibility of blend system than LDPE-g-MAH and LDPE-g-AA, now the friction coefficient of modified polyurethane reduced by 46%, the wear rate reduced by 91%, the tensile strength increased by 34%.Then the paper prepared maleic anhydride grafted onto ultra high molecular weight polyethylene(UHMWPE-g-MAH) by means of ultraviolet radiation grafting, and added it into the MPU. The changes of tribological properties, mechanical properties of the blend with UHMWPE grafted products as compatibilizer were assessed. The results show that the tribological properties, mechanical properties of UHMWPE grafted and MPU blend were better than MPU/UHMWPE blend. The friction coefficient of UHMWPE grafted and MPU blend reduced by 33%, the wear rate reduced by 76%, the tensile strength increased by 9%.