Poly(ethylene terephthalate)-poly(caprolactone) block copolymer. I. Synthesis, reactive extrusion, and fiber morphology

A novel poly(ethylene terephthalate)-poly(caprolactone) block copolymer (PE T-PCL) is synthesized in a reactive twin-screw extrusion process. In the pr esence of stannous octoate, ring-opening polymerization of epsilon-caprolac tone is initiated by the hydroxyl end groups of molten PET to form polycapr olactone blocks. A block copolymer with minimal transesterification is obta ined in a twin-screw extruder as a consequence of the fast distributive mix ing of epsilon-caprolactone into high melt viscosity PET and the short reac tion time. The PET-CL structure is characterized by IV, GPC, H-1-NMR, and D SC. Fully drawn and partially relaxed fibers spun from PET-PCL are characte rized by WAXD and SAXS. A substantial decrease in the oriented amorphous fr action appears to be the major structural change in the relaxed fiber that provides the fiber with the desired stress-strain characteristics. (C) 1999 John Wiley & Sons, Inc.