Polylactic Acid Polymorphs Aging Affect The Behavior And Performance Of Its Physical

In this paper, Froutier transform infrared spectroscopy (FTIR)、Differential scanning calorimetry (DSC)、wide-angle X-ray diffraction (WAXD) and polarized light microscope (POM) were used to investigated the influences of polymorphs and crystalline on their mechanical properties and physical aging behaviors of poly(1-lactide acid)(PLA).A series of a and α’ crystal form samples with different crystallinity was prepared by the regulation of temperature for the spectra collection. Compared with the crystallinity calculated by DSC and WAXD, we established a method to quantitatively calculate the crystallinity of two crystal forms of PLA by FTIR. The influences of the crystallization temperature on the PLA polymorph were taken into consideration to establish this method, we amended previous computational formula of crystallinity PLA.Based on the establishment of the method to regulate the polymorph and crystalinity, we researched the mechanical properties of PLA with different crystal form. The result show that the tensile strength and bending strength increase with the increasement of crystalline. And the elongation at break of α’ crystal modification is always greater than a crystal modification and the samples with proper crystallinity shows maximum elongation at break, because of the loose structure of α’ crystal modification.The investigation of the relationship between PLA polymorph and physical aging show that the inter-spherulite amorphous phase is consistent with the bulk’s amorphous, and the amorphous phase within the spherulites shows the confined behaviors. And two different confined amorphous may exit in a’crystal spherulites.At last, we tried to prepare PLA film with highly oriented molecular chain by the method of friction transfer, FTIR and WAXD were used to investigate the structure.Preliminary research show that the highly oriented structure, and the structure order degree of the highly oriented PLA film is between the three-dimensional ordered crystal and amorphous phase,...