Abstract: Polytetrafluoroethylene molding powder which comprises 0.01 to 1% by weight of a perfluoro(vinyl ether) unit and which has a heat of crystallization of 18.0 to 25.0 J/g. The molding powder provides a molded article which has a flex life of not less than 7 million cycles, a creep resistance (total deformation at 200.degree. C.) of not more than 20%, and a creep resistance (total deformation at 25.degree. C.) of not more than 15%. The polytetrafluoroethylene molding powder which is excellent in both creep resistance and flex fatigue resistance is provided as a molding material for parts which are repeatedly bent such as pump.

Abstract: A process for preparing a filled agglomerated polytetrafluoroethylene molding powder having a high flowability by agitating finely-divided polytetrafluoroethylene particles and a filler in an aqueous medium. While agitating a hydrophilic filler treated with an aminosilane compound in water in the presence of a higher fatty acid and/or an anionic surface active agent, the polytetrafluoroethylene particles and a water-immiscible organic liquid are added to water in that order, whereby most of the filler used can be uniformly incorporated into the agglomerated product without causing separation into the aqueous medium.