Abstract
Changes in the polymer properties of poly(lactic acid) (PLA) fibers during drawing and degradation processes were analyzed using solid-state NMR, with the goal of elucidating morphological changes that influence fiber tensile properties. Combination of X-ray diffraction (XRD) and differential scanning calorimeter (DSC) indicated that the drawn PLA fibers consisted of different proportions of α crystalline and amorphous forms. 13C CP-MAS NMR spectra showed amorphous-like broad singlet signals, of which the full width at half maximum (FWHM) decreased with increasing crystallinity and crystal orientation. The T1H value decreased by interaction with additives and increased with increasing crystal orientation. The interaction with additives also reduced T1C values, which increased with increasing crystallinity. Use of organic clay enhanced the crystallization of high draw-ratio PLA fibers due to nucleation, which increased tensile strength; this effect gradually decreased with time during accelerated weathering. In contrast, the plasticization due to the addition of flexible polymers increased fiber elongation, which rapidly dropped during the degradation. Changes of FWHM, T1H, and T1C values indicated that the degradation occurred at sites within the amorphous portions of the PLA fibers containing organic clay, while the flexible polymers were preferentially degraded if they were present in the PLA fibers.
Highlights
In order to put the post-petroleum society into practice, greater development of biomass-based materials is required
While 3 DR and 4 DR fibers were drawn in one step, the 6 DR fibers were drawn in two steps in order to prevent whitening
In order to extend application of solid-state NMR to support the manufacturing of biomass-based polymers, this study examined the effects of nucleating and plasticization additives on the fiber drawing and degradation processes of poly(lactic acid) fibers
Summary
In order to put the post-petroleum society into practice, greater development of biomass-based materials is required. A previous study examined several grades of PLA fiber obtained by high-speed melt spinning to characterize polymer crystallinity, orientation, and textile physical properties [15]. We have examined the effects of manufacturing processes on PLA composites using a reactive extrusion machine and nuclear magnetic relaxation time analysis; to date, we have investigated PLA nanocomposites with organic montmorillonites [31] and PLA/poly(ε-caprolactone). We focused on PLA fiber made by melt-spinning in order to further demonstrate the application of solid-state NMR to a product form. We examine the crystallinity and orientation of crystalline of the PLA fibers during the drawing by observing changes in 13 C CP-MAS NMR spectra and nuclear magnetic relaxation times, along with observations using the XRD and DSC. The difference between nucleating and plasticization additives at the molecular to nanometer levels, which is a significant factor for the manufacturing quality control, will reveal how PLA morphology influences the fiber tensile properties
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
