| Organic polymer materials are widely used in various fields of national production and life.Polypropylene is one of the important representative materials.Modification and optimization of its properties can not only save the cost of raw materials,reduce energy consumption,but also effectively avoid the potential safety hazards caused by the deterioration of material properties,so as to ensure the safety of people's production and life.Study the tribological properties of modified polypropylene materials,supplemented by the understanding of the aging mechanism,and grasp the objective laws of material structural performance changes,to take measures to extend its service life and promote the research and development of new materials and new methods.In this paper,the reciprocating friction and wear experiments of modified polypropylene were carried out by controlling the load and temperature variables,as well as the laboratory artificial simulation after accelerated ultraviolet aging,to learn the effects of different vertical loads under dry friction condition and different temperatures under water lubrication condition and aging cycles on the tribological properties of modified polypropylene;Analysis of the changes and formation mechanism of its microscopic features in metallographic and confocal microscopy.The research provides important theoretical and experimental basis for the expansion of applications of polypropylene with better properties.The conclusion of research is as follows:(1)The friction coefficient of the modified polypropylene material under dry friction and water lubrication conditions fluctuates with time and tends to be stable,and friction coefficient decreases with the increase of loads;while the temperature of the water is the opposite,increases with temperature;The wear rate is positively correlated with the increase of load and temperature;(2)The average coefficient of friction of the modified polypropylene under different loads is about 0.167,which is 40.3% lower than ordinary polypropylene,indicating that the friction coefficient is greatly reduced;on the contrary,it increases with temperature,and tends to be stable finally,and the average friction coefficient is 0.146,which is reduced by about 13%compared with dry friction conditions;(3)Under dry friction conditions,the material wear is mainly characterized by adhesive and abrasive wear,and the wear rate reaches the maximum under a load of 60N;the surface morphology showed fine corrugated wear marks and a light yellow area of thermal oxidative aging,and accompanied by a slight chalking phenomenon;Under the condition of water,the wear of the pp is abrasive wear,and the wear rate increases with temperature,and most significantly increases when the temperature is 20? to 40?,and the depth of the inner surface of the wear scar is slightly larger.Irregular furrows are accompanied by a certain amount of material peeling off;(4)Ultraviolet aging significantly reduces the material properties and affects the friction and wear properties of the material.The surface of the material becomes brittle and thinner,and the friction coefficient shows an increasing trend with different aging circle.Compared with that not aging before,the average increase of 52%,and the wear rate increased by nearly two times under the same load condition.The surface is very prone to cracks,and with aging days,the number of cracks increases and the expansion becomes wider,so as to the surface roughness increases.The color gradually changed from the initial milky white to light yellow with a slight pungent odor,and the local area of the edge of the wear scar appeared powdered.The longer the aging days,the more obvious the surface cracking of the sample are;(5)Under dry friction conditions,the coefficient of friction of modified polypropylene after aging is increased,the order of friction coefficient under the same load is: aging>nonirradiated>water lubrication;The order of the wear rate is: aging>non-irradiated>water lubrication. |
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