Study On The Resin Based Friction Material Reinforced With Ceramic Whisker

With the development of modern automotive industry and the enhancement of conscious on environment protection,friction material with higher properties is required.Reinforcing fibers are the framework of friction material,and they have played a crucial role to the strength of the friction pads.And,at the same time,they have significant influence to the other properties of the friction pads.Asbestos was once splendid reinforcing fiber and they had made a great contribution to the development of friction materials.However,asbestos is a cancer risk to humans that could not meet the environment-protection requirements.Domestic and international scholars have done lots of studies on the alternatives of asbestos materials and quite a lot good results have been achieved.Potassium titanate whiskers have excellent mechanical and physical properties and they become the ideal replacement of the asbestos in the field of friction material.This friction material used pure resin(No.2123)as agglomerant and NBR was used to modify its property.The reinforcing fibers contained potassium titanate whiskers, Kevlar pulp,steel fiber,copper fiber;the fillers contained graphite,Al₂O₃,Fe₂O₃, MgO,BaSO₄ etc.By means of orthogonal experiment and variance analysis,the influences of different main content to the frictional property were obtained,and the proper proportion of each mainly contents was confirmed.The mechanism of friction and wear was analyzed in this paper and the surface topography of the friction material at different temperatures was analyzed by Scanning Electron Microscope (SEM).The dry hot-pressing process had been chosen and the technical parameters were confirmed as below:the pressure was 15MPa,the temperature was 165±5℃,the insulation packing time was 25s/mm,and deflation last for 3s when suppress last for 8s and this step was repeated for 5 times.The technical parameters in the heat treatment stage were confirmed as below:the temperature was 230±10℃and the holding time last for 2 hours. By the research of the experiments,the best proportion of each contents of the friction material for the automotive is obtained as below:potassium titanate whiskers 20wt.%;Kevlar pulp 1wt.%;steel fiber 25wt.%;copper fiber 7wt.%;resin 9wt.%; graphite 9wt.%;others 29wt.%.The bench test results of the brake pad samples in accordance with the above composition showed:the performances of its running-in and friction were stable;the properties of anti-heat fading and recovery were fine;the samples after the test had a smooth surface,there were no cracks,no bubbles and such incidents.After analyzing the mechanism of the friction and wear and the micro-study of the friction surface,we concluded:the types of friction and wear of the friction material were mainly adhesive wear and abrasive wear;during the friction process,a relatively stable transfer film was formed on the friction material surface.And there were some obvious scratches along the running direction in the surface,and this was probably because of the falling off of the high hardness reinforcing fibers.They led to abrasive wear and made the scratches of the friction material.Experiment test results showed that the friction materials of this composition had proper coefficient,low wear ratio,low noise and good properties of heat fade resistance and recovery.They could meet the need of the break property of the automotive well.This kind of brake materials was suitable for the medium/minitype automotive.