The present disclosure provides tunable fluoropolymers and methods for making them.

An ethylene/tetrafluoroethylene copolymer satisfying the following formula (1):

75≤tan δ(60)/tan δ(5)×100≤225  (1)

wherein peak intensities, determined by Fourier transform infrared spectroscopy, of vibrations derived from a —CF.sub.2H group, a —CF.sub.2CH.sub.2COF group, a —COF group, a —COOH group, a dimer of a —CF.sub.2COOH group and a monomer of a CF.sub.2CH.sub.2COOH group, a —COOCH.sub.3 group, a —CONH.sub.2 group, and a —CH.sub.2OH group satisfy the following formula (2):

PI.sub.A/(PI.sub.B+PI.sub.C+PI.sub.D+PI.sub.E+PI.sub.F+PI.sub.G+PI.sub.H)≥0.60  (2)

wherein the loss tangents (tanδ) and peak intensities (PI) are as defined herein.

An ethylene/tetrafluoroethylene copolymer satisfying the following formula (1):

75≤tan δ(60)/tan δ(5)×100≤225  (1)

wherein peak intensities, determined by Fourier transform infrared spectroscopy, of vibrations derived from a —CF.sub.2H group, a —CF.sub.2CH.sub.2COF group, a —COF group, a —COOH group, a dimer of a —CF.sub.2COOH group and a monomer of a CF.sub.2CH.sub.2COOH group, a —COOCH.sub.3 group, a —CONH.sub.2 group, and a —CH.sub.2OH group satisfy the following formula (2):

PI.sub.A/(PI.sub.B+PI.sub.C+PI.sub.D+PI.sub.E+PI.sub.F+PI.sub.G+PI.sub.H)≥0.60  (2)

wherein the loss tangents (tanδ) and peak intensities (PI) are as defined herein.

The present invention pertains to: a fluororesin that includes a residue unit represented by formula (1), and a terminal group represented by formula (2); and a fluororesin that includes a residue unit represented by formula (1) and has a transmittance of 50% or more measured at an optical path length of 10 mm and a wavelength of 275 nm when dissolved in perfluorohexane to produce a 10 wt % perfluorohexane solution.

##STR00001##

In formula (1): Rf.sub.1, Rf.sub.2, Rf.sub.3, and Rf.sub.4 each independently represent one selected from the group consisting of fluorine atoms, C1-7 linear perfluoroalkyl groups, C3-7 branched perfluoroalkyl groups, or C3-7 cyclic perfluoroalkyl groups; the perfluoroalkyl groups may have an etheric oxygen atom; Rf.sub.1, Rf.sub.2, Rf.sub.3, and Rf.sub.4 may bond to each other to form a ring having 4 to 8 carbon atoms; and the ring may include an etheric oxygen atom.

##STR00002##

In formula (2), i is an integer of 3-20. The present invention provides: a fluororesin that includes an oxolane ring, has suppressed yellowing after heating and melting, and especially has reduced discoloration, even in molding of thick products; and a method for producing said fluororesin.

The present invention provides a method for manufacturing an optical resin composition that is less colored and that has a sufficiently low water absorbability. The optical resin composition manufacturing method according to the present invention includes performing a heat treatment of a fluorine-containing polymer under an atmosphere having a water vapor concentration of 100 volppm or less, the fluorine-containing polymer being obtained by polymerization of a monomer group including a fluorine-containing compound having a carbon-carbon double bond using an organic peroxide. In the optical resin composition manufacturing method, for example, the heat treatment causes thermal decomposition of a terminal group of the fluorine-containing polymer and volatilization of a low-molecular compound generated by the thermal decomposition.

The invention provides novel latexes of particles of vinylidene fluoride/trifluoroethylene copolymers possessing a more ordered ferroelectric crystalline phase, and hence improved ferro-, pyro-, and piezo-electric properties, and a method for manufacturing the same by emulsion polymerization in the presence of certain cyclic fluorosurfactants.

An object of the present disclosure is to provide, for example, a fluoropolymer electret material with hardness. The present disclosure relates to an electret material comprising a fluoropolymer, wherein the fluoropolymer comprises, as a main component, a monomer unit represented by formula (1):

##STR00001##

wherein R.sup.1 to R.sup.4 are each independently a fluorine atom, a fluoroalkyl group, or a fluoroalkoxy group; and the fluoropolymer has a mass average molecular weight of 1 million or more and 5 million or less, or 5000 or more and less than 20000.

Provided in this patent disclosure are two types of novel fluoro-monomers that can be polymerized for the fabrication of ion-exchange fluoropolymers. In addition, new proton-conductive zirconium-perfluorophosphonic acid fluoropolymer membranes that can reduce metal crossovers in redox flow batteries are also provided.

Provided in this patent disclosure are two types of novel fluoro-monomers that can be polymerized for the fabrication of ion-exchange fluoropolymers. In addition, new proton-conductive zirconium-perfluorophosphonic acid fluoropolymer membranes that can reduce metal crossovers in redox flow batteries are also provided.

A fluororesin having a tensile strength retention ratio of 50% or more, the tensile strength retention ratio being calculated by the following formula from the tensile strength of the fluororesin after a heat treatment obtained by conducting a heat treatment at 130° C. for 40,000 hours, and the tensile strength of the fluororesin before the heat treatment. Tensile strength retention ratio (%)=(tensile strength of fluororesin after heat treatment (MPa))/(tensile strength of fluororesin before heat treatment (MPa))×100.