The condensed-state structure and evolution mechanism of Poly(butylene-succinate) (PBS) multi-filaments in the complex stress and thermal fields of the melt-spinning process

Poly(butylene-succinate) (PBS) is a well-recognized semicrystalline polyester, renowned for its remarkable heat - resistance, extremely rapid crystallization rate, and biodegradability. To date, the constitutive relationship between the condensed-state structure of PBS fibers and their properties has not been systematically explored. This relationship, if understood, could offer theoretical guidance for industrial production. In this study, the structural evolution mechanisms of three types of melt-spun PBS fibers, namely undrawn yarn (UDY), pre-oriented yarn (POY), and fully - drawn yarn (FDY), were investigated. This was accomplished by systematically uncovering the stress-induced orientation and crystallization processes specific to each type during the melt-spinning procedure. The results demonstrated that the fibers crystallized rapidly at lower spinning speeds. Moreover, as the spinning speed increased, stress-induced orientation and crystallization were significantly enhanced, leading to the formation of large - diameter lamellar crystals reaching up to 72.3 nm. However, a higher degree of lamellar crystal diameter imposes limitations on perfect crystallization during the subsequent post - thermal drawing process. Due to the relatively high drawing speed, the “one-step” drawing process (FDY), which combines spinning and drawing, exhibited a significantly weaker stress-inducing effect compared to the “two-step” drawing process. This disparity restricted the orientation and crystallization of FDY fibers during the drawing process. Specifically, after three-times thermal drawing, the degree of orientation and crystallization of FDY fibers were merely 89.3 % and 67.5 % respectively, whereas those of UDY fibers reached 92.4 % and 72.1 %. This difference can be ascribed to insufficient heating in FDY fibers at higher drawing speeds compared to UDY fibers.