Crystallization mechanism, microstructure and mechanical property of poly (L-lactic acid) modified by introduction of hydrogen bonding

• Published in: Journal of polymer research 2016-06, Vol.23 (6), p.1, Article 118
• Main Authors: Si, Pengfei, Luo, Faliang, Xue, Ping, Yan, Dongguang
• Format: Article
• Language: English
• Subjects: Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Industrial Chemistry/Chemical Engineering; Original Paper; Polymer Sciences
• ISSN: 1022-9760; 1572-8935
• DOI: 10.1007/s10965-016-1010-9

In this work, 4,4′-Thiobis Phenol (TDP) was incorporated into PLLA using melt blending method. Overall crystallization mechanism and chain folding parameters in crystallization process were analyzed based on Avrami eq. and Lauritzen-Hoffman kinetic theory. Avrami exponent n for all samples were between 2.87 and 3.23, which indicated three dimensional crystal growth with heterogeneous nucleation. Meanwhile, overall crystallization rate of PLLA was significantly reduced by incorporation of TDP. The fold surface free energy ( σ e ) and work of chain folding ( q ) increased with TDP addition, implying that crystallization of PLLA was retarded. Small angle X-ray scattering (SAXS) analysis demonstrated that long period of PLLA was increased by TDP introduction, meaning more amorphous component between adjacent lamellae. As a result, the tensile strength decreased with TDP addition, while the elongation at break of PLLA was improved by more than 40 %.