Poly(Butyleneterephthalate-Co-Isophthalate)S - New Secondary Coating Materials For Optical Fibers

The shrinkage of copolyesters from terephthalic acid, isophthalic acid, and butanediol during injection molding and the after‐shrinkage during annealing exhibits a minimum at 20 mole‐% isophthalic acid. Polyesters of this composition have proved to be new outstanding materials for secondary coating of quartz glass optical fibres. They allow the production of optical fibre constructions without any increase in optical damping down to − 50°C.