Preparation And Performance Of Nano-magnetic Polytetralfuoroethylene Sealing Packing

Polytetrafluoroethylene（PTFE） is a thermoplastic plastic, which has been widelyused as sealing material for excellent chemical stability, low frictional coefficient andgood thermal stability properties. However, the application of PTFE is limited due topoor mechanical properties, high linear expansion coefficient and low thermalconductivity. Usually, methods of filling modification, surface modification andmixing modification have been employed to improve PTFE Comprehensiveperformance. In this thesis, by experimentally and theoretically studied, themagnetic-PTFE sealing material were prepared by used Nano-Fe₃O₄as reinforcingcomponent. The Effects of composition ratio on the properties of PTFE compositeswere analyzed by experiment test.The PTFE test sample was made by compression sintering molding, the contentof nano-Fe₃O₄was5%¹5%. The property of PTFE has good manufacturability,degree of crystallinity is68%, molecular weight great than one million, when moldingpressure is55MPa, molding time is15min, sintering temperature is380℃, heatingrate is100℃/min.The effects of nano-Fe₃O₄content on the porosity, hardness, tensile property,linear expansibility and water absorption of the composites were investigated. Theresults show that with increasing of content of nano-Fe₃O₄, the porosity, hardness andwater absorption of composites augmented gradually and the tensile strength firstincreased slightly and decreased largely afterward. When the fillers content was lessthan8%, nano-Fe₃O₄had a better dispersion in the PTFE matrix, the performance ofPTFE sealing material has been improved. When the fillers content was greater than8%, the porosity has increased rapidly and tensile strength decreased,. At this time,nano-Fe₃O₄has poor compatible with the matrix; the pores, cracks began grow at theinterface between matrix and nano-Fe₃O₄fillers, materials integrated performance wasnot improved.Hence, the conclusion can be drawn by test and analysis that when nano-Fe₃O₄contents was5%⁸%, the magnetic-PTFE sealing materials has low porosity, hightensile strength and low linear expansion property, sealing stability and reliability hasimproved.