Polytetrafluoroethylene filled with FeCo microparticles provides an ultralow wear, magnetic, multifunctional tribological material. For example, PTFE filled with an 5 wt. % of equiatomic, prealloyed FeCo powder resulted in steady state wear rates of 2.7×10.sup.−7 mm.sup.3/Nm, approaching that of PTFE-filled alumina. Comparable wear rates were not recovered for PTFE filled with just iron or cobalt microparticles.

Polytetrafluoroethylene filled with FeCo microparticles provides an ultralow wear, magnetic, multifunctional tribological material. For example, PTFE filled with an 5 wt. % of equiatomic, prealloyed FeCo powder resulted in steady state wear rates of 2.7×10.sup.−7 mm.sup.3/Nm, approaching that of PTFE-filled alumina. Comparable wear rates were not recovered for PTFE filled with just iron or cobalt microparticles.

A method for producing low-molecular-weight polytetrafluoroethylene which includes: (1) irradiating high-molecular-weight polytetrafluoroethylene with radiation to a dose of 250 kGy or higher substantially in the absence of oxygen to provide low-molecular-weight polytetrafluoroethylene having a melt viscosity at 380° C. of 1.0×10.sup.2 to 7.0×10.sup.5 Pa.Math.s. Also disclosed is a powder containing the low-molecular-weight polytetrafluoroethylene, the powder being substantially free from any of perfluorooctanoic acid and salts thereof.

A method for producing low-molecular-weight polytetrafluoroethylene which includes: (1) irradiating high-molecular-weight polytetrafluoroethylene with radiation to a dose of 250 kGy or higher substantially in the absence of oxygen to provide low-molecular-weight polytetrafluoroethylene having a melt viscosity at 380° C. of 1.0×10.sup.2 to 7.0×10.sup.5 Pa.Math.s. Also disclosed is a powder containing the low-molecular-weight polytetrafluoroethylene, the powder being substantially free from any of perfluorooctanoic acid and salts thereof.

A method for producing low-molecular-weight polytetrafluoroethylene which includes: (1) irradiating high-molecular-weight polytetrafluoroethylene with radiation to a dose of 250 kGy or higher substantially in the absence of oxygen to provide low-molecular-weight polytetrafluoroethylene having a melt viscosity at 380° C. of 1.0×10.sup.2 to 7.0×10.sup.5 Pa.Math.s. Also disclosed is a powder containing the low-molecular-weight polytetrafluoroethylene, the powder being substantially free from any of perfluorooctanoic acid and salts thereof.

A method for producing polytetrafluoroethylene includes a step of polymerizing tetrafluoroethylene in an aqueous medium in the presence of a hydrocarbon surfactant and a polymerization initiator to obtain polytetrafluoroethylene and a step of adding at least one selected from the group consisting of a radical scavenger and a decomposer of a polymerization initiator after the initiation of polymerization.

A method for producing polytetrafluoroethylene includes a step of polymerizing tetrafluoroethylene in an aqueous medium in the presence of a hydrocarbon surfactant and a polymerization initiator to obtain polytetrafluoroethylene and a step of adding at least one selected from the group consisting of a radical scavenger and a decomposer of a polymerization initiator after the initiation of polymerization.

A composition having a breaking strength of 10.0 N or more, containing a polytetrafluoroethylene, and substantially free from a compound represented by the following general formula (3):

(H—(CF.sub.2).sub.8—SO.sub.3).sub.qM.sup.2  General Formula (3): wherein M.sup.2 is H, a metal atom, NR.sup.5.sub.4, where each R.sup.5 may be the same or different and is H or an organic group having 1 to 10 carbon atoms, imidazolium optionally having a substituent, pyridinium optionally having a substituent, or phosphonium optionally having a substituent; and q is 1 or 2.

A composition having a breaking strength of 10.0 N or more, containing a polytetrafluoroethylene, and substantially free from a compound represented by the following general formula (3):

(H—(CF.sub.2).sub.8—SO.sub.3).sub.qM.sup.2  General Formula (3): wherein M.sup.2 is H, a metal atom, NR.sup.5.sub.4, where each R.sup.5 may be the same or different and is H or an organic group having 1 to 10 carbon atoms, imidazolium optionally having a substituent, pyridinium optionally having a substituent, or phosphonium optionally having a substituent; and q is 1 or 2.

A method for producing a fluoropolymer, which includes polymerizing a fluoromonomer in an aqueous medium in the presence of a polymer (1), the polymer (1) including a polymerized unit derived from a monomer CX.sub.2═CY(—CZ.sub.2—O—Rf-A), wherein X is the same or different and is —H or —F; Y is —H, —F, an alkyl group, or a fluorine-containing alkyl group; Z is the same or different and is —H, —F, an alkyl group, or a fluoroalkyl group; Rf is a C1-C40 fluorine-containing alkylene group or a C—C100 fluorine-containing alkylene group and having an ether bond; and A is —COOM, —SO.sub.3M, or —OSO.sub.3M, wherein M is —H, a metal atom, —NR.sup.7.sub.4, imidazolium optionally having a substituent, pyridinium optionally having a substituent, or phosphonium optionally having a substituent, wherein R.sup.7 is H or an organic group, providing that at least one of X, Y, and Z contains a fluorine atom.