A method for producing a composition containing low molecular weight polytetrafluoroethylene, the method including: (I) irradiating a composition containing high molecular weight polytetrafluoroethylene with ionizing radiation to obtain a composition containing low molecular weight polytetrafluoroethylene having a melt viscosity at 380° C. in the range of 1.0×10.sup.2 to 7.0×10.sup.5 Pa.Math.s; and (II) decomposing a low molecular weight fluorine-containing compound contained in the composition containing low molecular weight polytetrafluoroethylene obtained above.

A fluorine-containing resin particle contains 0 or more and 30 or less carboxyl groups per 10.sup.6 carbon atoms and 0 ppm or more and 3 ppm or less of a basic compound.

A fluorine-containing resin particle contains 0 or more and 30 or less carboxyl groups per 10.sup.6 carbon atoms and 0 ppm or more and 3 ppm or less of a basic compound.

A dielectric waveguide including: a center dielectric A1; a dielectric layer A2 surrounding the center dielectric A1; and a dielectric layer A3 surrounding the dielectric layer A2, the center dielectric A1 including polytetrafluoroethylene, the center dielectric A1, the dielectric layer A2, and the dielectric layer A3 having relative permittivities at 25° C. and 6 GHz represented by ε.sub.A1, ε.sub.A2, and ε.sub.A3, respectively, ε.sub.A1, ε.sub.A2, and ε.sub.A3 satisfying the following: ε.sub.A1 is 2.20 or lower; ε.sub.A2 is 1.90 or lower; ε.sub.A3 is 1.55 or lower; and ε.sub.A1>ε.sub.A2>ε.sub.A3 is satisfied.

A dielectric waveguide including: a center dielectric A1; a dielectric layer A2 surrounding the center dielectric A1; and a dielectric layer A3 surrounding the dielectric layer A2, the center dielectric A1 including polytetrafluoroethylene, the center dielectric A1, the dielectric layer A2, and the dielectric layer A3 having relative permittivities at 25° C. and 6 GHz represented by ε.sub.A1, ε.sub.A2, and ε.sub.A3, respectively, ε.sub.A1, ε.sub.A2, and ε.sub.A3 satisfying the following: ε.sub.A1 is 2.20 or lower; ε.sub.A2 is 1.90 or lower; ε.sub.A3 is 1.55 or lower; and ε.sub.A1>ε.sub.A2>ε.sub.A3 is satisfied.

A fluorine-containing polymer has a fluorine content of 50% by mass or more, a degree of unsaturation of 0.1 mEq/g or more, and a glass transition temperature of −20° C. or higher, and the relationship between the maximum value E*1 of the complex elastic modulus in the range of from −50° C. to (glass transition temperature−10° C.) and the minimum value E*2 of the complex elastic modulus in the range of from (glass transition temperature+10° C.) to 250° C. satisfies the following inequality: E*2/E*1≤0.01.

A fluorine-containing polymer has a fluorine content of 50% by mass or more, a degree of unsaturation of 0.1 mEq/g or more, and a glass transition temperature of −20° C. or higher, and the relationship between the maximum value E*1 of the complex elastic modulus in the range of from −50° C. to (glass transition temperature−10° C.) and the minimum value E*2 of the complex elastic modulus in the range of from (glass transition temperature+10° C.) to 250° C. satisfies the following inequality: E*2/E*1≤0.01.

A method for producing a polytetrafluoroethylene powder, which includes applying an ultrasonic wave to a polytetrafluoroethylene aqueous dispersion containing polytetrafluoroethylene particles to coagulate the polytetrafluoroethylene particles.

A method for producing a polytetrafluoroethylene powder, which includes applying an ultrasonic wave to a polytetrafluoroethylene aqueous dispersion containing polytetrafluoroethylene particles to coagulate the polytetrafluoroethylene particles.

A method for producing a polytetrafluoroethylene powder, which includes applying an ultrasonic wave to a polytetrafluoroethylene aqueous dispersion containing polytetrafluoroethylene particles to coagulate the polytetrafluoroethylene particles.