Performance And Interface Study Of Filled PTFE Composites

Polytetrafluoroethylene(PTFE)has been widely used as an engineering plastic.However,its poor mechanical,thermal expansion and wear properties has greatly limited its wider application in many special occasions such as high temperature and high pressure.Therefore,how to solve the problems encountered such as wear resistance at high temperature in modern industrial production and improve the comprehensive properties of PTFE material is a subject worthy of further study.In this paper,the effects of inorganic fillers with different size,morphology and surface properties on the properties of PTFE composites were studied.At the same time,the effects of different mass ratio,morphology and surface modification on the properties and interfacial interaction of composites were discussed.(1)The PTFE composite filled with glass fiber(GF)and halloysite(HNTs)were prepared by cold forming and sintering.The effects of the filler type,and its matching on the frictional performance,linear expansion coefficient and mechanical of PTFE matrix composites were investigated.The results indicate that the composite filled with HNTs suitably not only increases the wear property of GF/PTFE composites,but also causes the thermal expansion and friction and mechanical properties to increase.The wear rate of the ternary composite filled with 2wt%HNTs is reduced by 32.7%in comparison with GF/PTFE binary system.The linear expansion coefficient of this HNTs-GF/PTFE ternary composite is reduced by almost 2 orders of magnitude compared with that of PTFE.The elongation of HNTs-GF/PTFE at break,tensile strength and bend strength improved by 40.0%,2.3%and 7.1%respectively.(2)The use of GF,molybdenum disulfide(MoS2)and talc has been evaluated to reinforce PTFE.The orthogonal experiment results show that the optimal weight ratio of GF,MoS2,talc and PTFE is 2:3:3:92 for PTFE composite,resulting in better mechanical properties,low linear expansion and wear rate.The treatment of chemical coupling on the surface of glass fiber under high temperature greatly enhances the interface adhesion between PTFE matrix and the glass fiber revealed by atomic force microscopy(AFM)and SEM analysis.At the same time,the mechanical interlocking effect between filler and polymer matrix is also an important factor for the high performance of PTFE composites.(3)Graphene nanoplatelets(GNPs)separated by the spindle-like CaCO3(CGNPs)were used as fillers to produce CGNPs/PTFE nanocomposites.The effect of the CGNPs on the mechanical,electrical,and frictional properties of the nanocomposites were investigated and discussed.It is found that the tensile strength and elongation at break of the nanocomposites are improved by 44%,26%,respectively,at a percolation threshold of 1 wt%and the conductive network of the nanocomposites is basically formed when the filler loading up to 10wt%,at the same time,the frictional properties of the composites are excellent.The effects of CGNPs on the properties of the composites were investigated by means of DSC,Raman spectroscopy and micro morphology.The results show that CGNPs is uniformly dispersed in the polymer matrix,a small amount of CGNPs can play the role of heterogeneous nucleation,and improve the mechanical properties of composite materials;in addition,the unique three-dimensional structure of CGNPs and the mechanical interlocking effect between filler and polymer matrix is the main reason about the excellent electrical and tribological properties of PTFE composites.