Study On On Modified Polyoxymethylene Composites By Wear-resistance And Toughing Method

Polyformaldehyde(POM),as one of the five engineering plastics,is a common thermoplastic engineering plastics,which has good physical and mechanical properties and excellent processing properties.Its mechanical properties,wear resistance and self-lubrication are excellent,and its specific strength and stiffness are similar to those of metals.It has been widely used in electronic and electrical appliances,machinery manufacturing,automotive industry and other industries,replacing traditional steel,iron,copper,aluminum and other metal materials.With the development of science and technology and the continuous expansion of POM applications,new modification technology of POM also has been required.In this paper,the friction properties and wear mechanism of POM were studied systematically.The high wear resistance and toughened POM composites were prepared by blending POM resin with other resin/inorganic materials.The main research contents are as follows:(1)Wear-resistant POM materials were prepared by adding PTFE fibers,basalt fibers or carbon fibers respectively.The effects of different proportion of fibers on the friction and mechanical properties of POM composites were investigated.The results show that PTFE fibers can effectively improve the friction properties of POM,but the mechanical prop.erties are not ideal.When the content of PTFE fibers is 8%,the friction coefficient of modified POM is 0.181,and the wear scar width is 3.94 mm.Basalt fibers can not improve the friction and wear properties of POM,but it can improve the mechanical properties of POM obviously.The friction and mechanical properties of carbon fibers modified POM were both improved,and the mechanical properties of POM increased significantly.Thermodynamic properties of various fiber modified POM were investigated.-The addition of each three kinds of fibers can increase the initial decomposition temperature and termination decomposition temperature of POM,and improve the thermal stability of POM.(2)The toughening effect of thermoplastic polyurethane elastomer on POM was studied,and the mechanical properties of the modified POM were investigated.The effect of different proportion of polyurethane elastomer on the mechanical properties of POM was studied mainly.When the content of TPU is 30%,the elongation at break of the toughen POM is 235.3%,and the notch impact strength is 20.3 kJ/m2,which is 178%higher than that of pure POM.The spherulite morphology of the PoM/TPU composites was observed by polarizing microscope.It is proved that the nucleation and compatibilization of polyethylene oxide(PEO)could promote the distribution of TPU in POM matrix and cause the formation of an effective toughening network structure,thus leading to a more remarkable toughening effect.(3)According to the friction and wear mechanism of POM and the structural characteristics of POM molecular chain,a wear resistant and toughened POM system was developed.The friction and mechanical properties of POM can be optimized simultaneously by adding PTFE fiber and PEO into POM matrix.When adding 10%PTFE fiber and 15%PEO into POM matrix,the friction coefficient of the composites decreases to 0.15,and the notch impact strength reaches 13.2 kJ/m2.The friction properties and wear mechanism of the wear resistant and toughened POM were further explored.The self-lubrication of PTFE fiber and the compatibility of PEO can reduce the friction coefficient and friction loss of POM,and the notched impact strength of POM can be improved by adding PTFE.