Preparation And Structure Of The Microporous Ptfe Cable Insulation Materials, The Performance Of Research

Microporous Polytetrafluoroethylene(PTFE) material was widely used as an insulation material in Radio Frequency coaxial cables due to its unique structure and outstanding properties,especially for its outstanding electrical properties.Now,a new solid-stretching Microporous PTFE material was made in overseas, which was used as an insulation material in microwave coaxial cables.The insulation material has very low dielectric constantεand tgδto reduce the cable's attenuation largely.But no document about the manufacture teclmology of the insulation material could be available.And no research about it had been started in China.So the research about it was very necessary,which was beneficial not only in theories but also in Radio Frequency coaxial cables to lift the level of the manufacture technology in China.The solid-stretching microporous PTFE material was made by "extrusion-stretch-sinter"one-step manufacture method,which is a continuous process included extruding the paste of PTFE dispersion resin through a die,stretching, sintering and cooling at the same time.The effects of preforming pressure,content of lubricant,extrusion die's structure size,extrusion pressure and temperature etc on the extrusion were studied.The microporous structure shaped mechanism in the insulation material were investigated. The microporous PTFE material's microstructure were analyzed through Scanning Electron Microscopy(SEM).The microporous material's porosity and pore size distribution were researched through mercury porosimetry.Crystallinity of the microporous PTFE material was characterized by DSC,and the degree of orientation was characterized by wide angle X-ray diffraction(WAXD).The effects of stretching processes on the microporous structure and pore property were studied.The results show that stretching ratio is the crucial factor affecting the structure and properties of the microporous PTFE material.The microstructure of the microporous PTFE material was characterized by the nodes like island and microfibrils that interconnected the nodes.By uniaxial stretching the nodes,the longer axis of nodes were oriented perpendicular to the stretching direction.The microfibrils were oriented parallel to the stretching direction. The pore was shaped between the microfibrils.The microporous PTFE material has small pore size(0.01～10.0μm),high porosity(40～80%),wide and uniform pore size distribution,low dielectric constantε(1.2～1.8).Two different specification cable specimens were made,and the properties of which were tested.