Polytetrafluoroethylene molding powder

Details Polytetrafluoroethylene molding powder Polytetrafluoroethylene molding powder

1974-06-17

1976-09-21

Wong, Jr., Harry

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

526254, C08F11426, C08F21426

Patent

active

039818527

ABSTRACT:
Finely divided polytetrafluoroethylene molding powder is disclosed having a remarkable combination of high apparent density and high moldability, the latter being reflected as a small difference in specific gravity (.DELTA.SG) of standard moldings molded at high and low preform pressures. For example, molding powders having an average particle diameter (d.sub.50) of no greater than 60, a .DELTA.SG.sub.5.sub.-1 of no greater than 30 and apparent density of at least 600 g/l are disclosed. These molding powders are obtained from unique process steps involving either the fine powder type of polytetrafluoroethylene or the granular type of polytetrafluoroethylene as the starting material. The fine powder type is compacted to a high degree, followed by partially decompacting the resultant compacted fine powder to the molding powder particle size desired. When the granular type is the starting material, this is comminuted to the molding powder particle size desired, followed by separating the molding powder into hard and soft material fractions, followed by re-grinding the relatively coarse, hard fraction by itself to an average particle size of at least as small as the original combined fractions. The resultant molding powder is useful in the manner of previous polytetrafluoroethylene molding powders with the advantage of requiring reduced mold height and molding pressure to achieve equivalent quality moldings.

REFERENCES:
patent: 2573639 (1951-10-01), Coler
patent: 3087921 (1963-04-01), Matthews et al.
patent: 3674762 (1972-04-01), Izumo et al.
patent: 3690569 (1972-09-01), Leverett

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