Process for forming an expanded porous tetrafluoroethylene polymer
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United States of America Patent
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Mar 24, 1992
Issued Date -
N/A
app pub date -
Dec 17, 1990
filing date -
Mar 14, 1989
priority date (Note) -
Expired
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Abstract
A process for preparing an improved expanded porous polytetrafluorethylene product having a higher density and improved cold flow properties and prepared from a paste formed from a polytetrafluoroethylene resin and a lubricant. The method includes extruding the paste through an extrusion die at a reduction ratio of less than 100, calendering the extrudate, removing the lubricant, and heating the extrudate to a temperature greater than the crystalline melting point of polytetrafluoroethylene but generally below the temperature at which thermal decomposition becomes appreciable while concurrently expanding the extrudate to at least twice its original length.
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