The Preparation,Properties And Structure Of Polylactide Fiber

With the increasing concern of energy shortage and environment deterioration, the bio-based fibers are drawing increasing attention in both academic and industrial areas. As typical polymers which have sustainability and degradability, poly(lactic acid)(PLA) has been commercialized and expected to find applications in the fiber and textile industries. However, on one hand, the poor heat resistance, uncomfortable in hand feel should be improved.In this article, PLA fibers were prepared by melt spinning. Foucing on the molecular weight and optical purity, we explored the rheological properties, spinnability, process degradation, tenacity, modulus, elongation at break, boiling water shrinkage, crystallization, orientation and conformation properties of PLA fibers. Specific conclusions are as follows:1. PLA exhibited the typical shear-thinning pseudoplastic fluid behavior. At the same shear rate, the lager molecular weight of PLA, the higher shear viscosity is. Compared with high optical purity PLA, the shear viscosity of PLA with low optical purity changes greater with increasing temperature. By adjusting the spinning conditions, all PLAs could show good spinnability.2. High molecular weight PLA degraded severely during the spinning process because of the higher shear stress and melting temperature. The intrinsic viscosity of high molecular weight PLA reduced by 16.5%. However, the optical isomers of all PLAs were hardly affected during the spinning process and their optical purity remained unchanging.3. In most cases, PLA fibers with high molecular weight and high optical purity exhibited the most excellent tensile properties and the lowest boiling water shrinkage. Due to the drawing treatment, all PLA fiber’s mechanical strength and elongation are significantly improved to better meet the needs of textile. Interestingly, the boiling water shrinkage of high optical purity PLA falled to below 10% while the boiling water shrinkage of low optical purity PLA fibers was still higher than 75% after drawing.4. Amorphous PLA spun fibers turned to be crystalline by drawing. Compared with the low optical purity PLA drawed fiber, the high optical purity PLA drawed fiber had greater degree of crystallinity. According 2D-WAXD, DSC, Infrared dichroism and velocity method, the crystallinity and orientation results were mostly consistent with PLA fiber’s tensile properties, but can not explain the change of boiling water shrinkage well.5. According to XRD and FTIR study, improving the optical purity of PLA could help the crystal and conformational stability. High optical purity PLA preferentially formed stable α crystal during the crystallization process and included the most lowenergy gt conformations, morever it exhibited excellent thermal stability.