Aggregation structure development and mechanical properties of biodegradable poly(butylene succinate-co-terephthalate) fibers

Biodegradable poly(butylene succinate-co-terephthalate)(PBST) copolyester, with 70 mol % butylene terephthalate (BT), was melt-spun into fibers at various take-up velocities ranging from 2.0 to 4.0 km/min. The structure development and mechanical properties of the as-spun PBST fibers were intensively investigated via birefringence, wide angle X-ray diffraction (WAXD) measurement, tensile test, and cyclic stretch test. With increasing the take-up velocity, the initial tensile modulus and breaking strength of PBST fibers increased, while elongation at break decreased. These were attributed to the increasing degree of orientation and crystallinity, which were resulted from the elevating tension of spinning line at higher take-up velocity. To elucidate the effects of soft butylene succinate (BS) unit on the tensile and elastic properties of PBST fibers, poly(butylene terephthalate) (PBT) fibers were adopted as a comparison sample. The results showed that the combination of soft BS unit and hard BT unit for PBST fibers made contribution to the lower initial modulus, higher elongation at break and better elastic recovery than those of PBT fibers. Moreover, PBST fibers were found to undergo PBT-like crystal form transition from α-form to β-form crystal structure under tension load through the measurement of WAXD. A relatively wider strain region for the crystal transition of PBST fibers also endowed them with higher elastic recoverability than PBT fibers. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012