Modification Of Poly(Lactic Acid) On Crystallization And Toughening

In this thesis, firstly, PLLA/TMC-210 blends were fabricated by using twin-screw melt extrusion technology. The results showed that pure PLLA had no crystallization peak upon cooling at 10℃/min. However, by loading 0.2 wt% TMC-210, the crystallization peak could be observed and the crystallization peak shifted to a higher temperature with increasing TMC-210 content on PLLA cooling DSC curves. Besides, the addition of TMC-210 led to the nucleation density of PLLA increasing, the spherulite size decreasing, a shorter crystallization time and a faster crystallization rate. PLLA crystal structure had no been influenced with the addition of TMC-210.The thermal stability, tensile strength and flexural strength of PLLA decreased, but notched impact strength increased with increasing of TMC-210 content. The impact strength of PLLA containing 0.2 wt% TMC-210 increased by 3.3 times. Therefore, adding nucleating agent TMC-210 is an effective approach to promote crystallization rate and toughness of PLLA.Secondly, the crystallization behavior and properties of PLLA with the addition of TMC-306 were investigated by FTIR、WAXD, DSC and POM et al. The results showed that PLLA/TMC-306 blends displayed an obvious crystallization peak in the cooling process. The Avrami equation was appropriate to analysis the isothermal crystallization kinetics of PLLA/TMC-306 blends. The addition of TMC-306 also led to a shorter crystallization time and a faster crystallization rate of PLLA, and the crystallization rate increased with crystallization temperature rising. In addition, the nucleation density of PLLA increased and the spherulite size decreased with the incorporation of TMC-306, the crystal structure and crystal form of PLLA was not affected by the addition of TMC-306. At the same time, the heat resistance and notched impact strength of PLLA enhanced with the introduction of TMC-306, but the tensile strength and flexural strength decreased. When TMC-306 content reached 0.4wt%, the impact strength of PLLA increased by 3.7 times. Therefore, TMC-306 could not only promote the crystallization of PLLA but also improve its toughness.Finally, ternary composites PLLA/PBSA/TDP (DHP, BPS) were prepared through solution method and melting method, respectively. And the effects of TDP, DHP and BPS on the compatibility, crystal form, thermal and mechanical properties of PBSA and TDP were studied. The results showed that the compatibility of PLLA and PBSA could be improved by the addition of TDP, DHP or BPS, and TDP showed the most obvious effect. In ternary blends, PLLA and PBSA crystal form had no change. The thermal stability of ternary blends declined due to the addition of TDP. The tensile strength and flexural strength of PLLA/PBSA/TDP (DHP, BPS) ternary blends decreased, and the elongation at break increased with the increasing content of TDP. Moreover, the impact strength increased constantly. When the TDP content reached 5wt%, the impact toughness of blended PLLA increased 9.1 times compared with pure PLLA and the elongation at break reached maximum. Among them, TDP showed the most significant toughness effect on PLLA.