| 摘要 |
Polytetrafluoroethylene resin granules having an average size wet-sieve (defined) within the range of 200 to 800 microns, a bulk density (defined) of at least 500 grams per litre, a flow time (defined) of less than 200 seconds, a required preform pressure (defined) not in excess of 2000 p.s.i., are obtained by subjecting ultra-fine polytetrafluoroethylene resin particles having an average particle size, wet-sieve of less than 100 microns, to agitation in an aqueous medium at a temperature above 40 DEG C. until agglomeration of the resin particles occurs to give granules, and separating the resulting resin granules from the aqueous medium. The granules can be sintered to produce a resin having a tensile strength (defined) of at least 3600 p.s.i., a dielectric strength (defined) of at least 1200 volts per mil., and a per cent elongation (defined) of at least 300. The ultra-fine resin particles may be obtained by reduction of coarse granular resin in an air-mill. |
