Abstract: A foaming composition includes a polymer having a melting temperature above 250° C., and an organic salt as chemical foaming agent having a decomposition temperature above the melting point of the polymer, where the organic salt is selected from the group of citrate derivatives and tartrate derivatives, or a mixture thereof.

Abstract: The invention provides a thermally-stable extrudable composition comprising fluropolymer and titanium dioxide, and further comprising an inorganic filler suitable for neutralizing the acid that forms during the step of extruding the composition, the filler having particles with a mean size of less than 100 nm, and preferably less than 60 nm.

Abstract: The present invention provides a photo-crosslinkable composition for fabricating a material for a step-index plastics optical fiber. The invention is remarkable in that the photo-crosslinkable composition comprises an acrylate derivative of a compound based on bisphenol, and a photoinitiator.

Abstract: A subject-matter of the invention is a copolymer comprising at least 3 units, P1, P2 and P3, with the following general formulae: with X1, X2 and X3, which are identical or different, taken from the group of atoms consisting of H, F, Cl and Br; with R1 taken from the group of atoms consisting of H, F, Cl and Br; with R2 a carbonaceous group comprising from 1 to 10 partially or completely fluorinated carbon atoms; with Y1 and Y2, which are identical or different, taken either from the group of atoms consisting of H, F, Cl and Br or from the family of the carbonaceous groups comprising from 1 to 10 carbon atoms; with Y3 a carbonyl group or a divalent carbonaceous group; the content of P2 unit in the copolymer being between 30 and 70 mol % for respectively a content of P1 and P3 units in the copolymer of between 70 and 30 mol % and the weight-average molar mass (Mw) of the said copolymer being between 103 and 106 g/mol. Preferably, the copolymer is of CTFE/VCA/HFP or TFE/VCA/HFP type.

Abstract: A method of fabricating a graded index plastics material optical fiber whose refractive index varies between its center and its periphery comprises the following process steps: preparing at least two liquid compositions with different refractive indices, each composition comprising at least one polymer, a substance to vary the refractive index being present in at least one composition and a cross-linking starter being present in at least one composition, filling a preform formation system with the compositions, producing a liquid preform in the system, the refractive index of said preform having a given gradient, and drawing the preform to obtain a graded index plastics material optical fiber. The production of the preform comprises a step with substantially no flow of the compositions along the system.