FIBER STRUCTURE DEVELOPMENT IN HIGH-SPEED MELT-SPINNING OF COPOLYESTERS - POLY(ETHYLENE TEREPHTHALATE-CO-1,4-CYCLOHEXYLENE DIMETHYLENE TEREPHTHALATE)

High-speed melt spinning of poly(ethylene terephthalate) (PET), poly(1,4-cyclohexylene dimethylene terephthalate) (PCT) and ET/CT copolyesters were performed and the structure and properties of as-spun fibers were investigated. Molecular orientation increased with an increase in the take-up velocity, and orientation-induced crystallization of PET and PCT started at similar to 4.5 and 3.5 km/min. With the addition of CT component to PET, and ET to PCT, the onset of crystallization shifted to higher velocities. In as-spun fibers of the copolymer of ET/CT = 66/34 mol%, which is known as an amorphous copolyester, the crystallization was not observed even at the attained highest take-up velocity, 6 km/min. On the other hand, crystallization of these fibers occurred on annealing suggesting that although the incorporation of copolymer component suppresses the crystallization, the molecular orientation enhances the crystallization of copolymer systems as in the cases of homopolymers.