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: 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 fluorovinyl ether of the formula:R.sub.f --(OCF.sub.2 CF.sub.2 CF.sub.2).sub.n --OCF.dbd.CF.sub.2(I)wherein R.sub.f is a C.sub.1 -C.sub.5 perfluoroalkyl group, n is an integer of 1 to 4 provided that when n is 1 (one), R.sub.f is other than a trifluoromethyl group, a copolymer of which with an ethylenically unsaturated compound has a low glass transition temperature and improved low temperature properties.

Abstract: A fluorovinyl ether of the formula:R.sub.f --(OCF.sub.2 CF.sub.2 CF.sub.2).sub.n --OCF.dbd.CF.sub.2(I)wherein R.sub.f is a C.sub.1- -C.sub.5 perfluoroalkyl group, n is an integer of 1 to 4 provided that when n is 1 (one), R.sub.f is other than a trifluoromethyl group, a copolymer of which with an ethylenically unsaturated compound has a low glass transition temperature and improved low temperature properties.

Abstract: Modified PTFE fine powder which comprises colloidal particles of a copolymer comprising repeating units derived from tetrafluoroethylene and 0.02 to 0.3 % by weight, preferably 0.03 to 0.2% by weight of repeating units derived from at least one fluoroalkyl vinyl ether selected from compounds of the formula:X(CF.sub.2).sub.n OCF.dbd.CF.sub.2 (I)wherein X is a hydrogen, fluorine or chlorine atom and n is an integer of 1 to 6, andC.sub.3 F.sub.7 (OCF.sub.2 CF.sub.2 CF.sub.2).sub.m [OCF(CF.sub.3)CF.sub.2 ].sub.1 OCF.dbd.CF.sub.2 (II)wherein m and 1 are each an integer of 0 to 4 provided that at least one of them is not zero, which has a number average particle size of 0.05 to 0.6 .mu.m, wherein the copolymer has a specific melt viscosity of from 6.times.10.sup.10 to 30.times.10.sup.10 poise, preferably from 8.0.times.10.sup.10 to 25.times.10.sup.10 poise at 380.degree. C. and a standard specific gravity (SSG, hereinafter defined) of from 2.135 to 2.175, preferably from 2.140 to 2.

Abstract: Modified PTFE fine powder which comprises colloidal particles of a copolymer comprising repeating units derived from tetrafluoroethylene and 0.02 to 0.3% by weight, preferably 0.03 to 0.2% by weight of repeating units derived from at least one fluoroalkyl vinyl ether selected from compounds of the formula:X(CF.sub.2).sub.n OCF.dbd.CF.sub.2 (I)wherein X is a hydrogen, fluorine or chlorine atom and n is an integer of 1 to 6, andC.sub.3 F.sub.7 (OCF.sub.2 CF.sub.2 CF.sub.2).sub.m [OCF(CF.sub.3)CF.sub.2 ].sub.l OCF.dbd.CF.sub.2 (II)wherein m and l are each an integer of 0 to 4 provided that at least one of them is not zero, which has a number average particle size of 0.05 to 0.6 .mu.m, wherein the copolymer has a specific melt viscosity of from 6.times.10.sup.10 to 30.times.10.sup.10 poise, preferably from 8.0.times.10.sup.10 to 25.times.10.sup.10 poise at 380.degree. C. and a standard specific gravity (SSG, hereinafter defined) of from 2.135 to 2.175, preferably from 2.140 to 2.