Relationship between the Stereocomplex Crystallization Behavior and Mechanical Properties of PLLA/PDLA Blends

Abstract

Poly (l-lactic acid) (PLLA) is a promising biomedical polymer material with a wide range of applications. The diverse enantiomeric forms of PLLA provide great opportunities for thermal and mechanical enhancement through stereocomplex formation. The addition of poly (d-lactic acid) (PDLA) as a nucleation agent and the formation of stereocomplex crystallization (SC) have been proven to be an effective method to improve the crystallization and mechanical properties of the PLLA. In this study, PLLA was blended with different amounts of PDLA through a melt blending process and their properties were calculated. The effect of the PDLA on the crystallization behavior, thermal, and mechanical properties of PLLA were investigated systematically by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), polarized optical microscopy (POM), dynamic mechanical analysis (DMA), and tensile test. Based on our findings, SC formed easily when PDLA content was increased, and acts as nucleation sites. Both SC and homo crystals (HC) were observed in the PLLA/PDLA blends. As the content of PDLA increased, the degree of crystallization increased, and the mechanical strength also increased.

Effects on the crystallization behavior and biocompatibility of poly(LLA-ran-PDO-ran-GA) with poly(d-lactide) as nucleating agents

“…The crystallization peaks at 15.0 , 16.9 , 19.2 and 22.5 were attributed to the a-form crystals of PLLA, which were corresponding to the (010), ( 200)/(110), ( 203) and (210) lattice planes, respectively. [38][39][40] Besides, three diffraction peaks at 11.9 , 20.9 and 24.0 could be assigned to (110), (300)/(030) and (220) planes of sc-PLA, respectively. 41 Importantly, the peak intensity of sc-PLA increased with the increase of PDLA content.…”

Enhancement in Crystallizability of Poly(L-Lactide) Using Stereocomplex-Polylactide Powder as a Nucleating Agent

“…XRD patterns were used to investigate the crystalline structures of the powders, as presented in Figure 3 . It can be seen that the LMW-PLLA powder exhibited diffraction peaks at 2θ = 14.8°, 16.9°, 19.1°, and 22.5° assigned to PLA homo-crystallites, whereas the scPLA powder showed diffraction peaks at 2θ = 12.0°, 20.8°, and 24.0° attributed to PLA stereocomplex-crystallites [ 17 , 28 , 29 ]. The XRD results confirmed that the LMW-PLLA and scPLA powders had complete homo- and stereocomplex crystallites, respectively, in agreement with the DSC results described above.…”

Effects of Amino Hyperbranched Polymer-Modified Carbon Nanotubes on the Crystallization Behavior of Poly (L-Lactic Acid) (PLLA)

“…The average molecular weight (M w ) of PLLA 4032D is 2 × 10 5 g/mol, and its melting index is 5.7 g/10 min [ 9 , 23 ], produced by Natureworks Co., Ltd., Minnetonka, MN, USA. The hyperbranched polyester N103 was purchased from Wuhan Hyperbranched resin Technology Co., LTD, China.…”

“…Therefore, the efficient regulation of PLLA’s crystallization rate has become a research hotspot. Great efforts had been made in this field and results have revealed that the crystallization rate of PLLA can be improved by copolymerization [ 8 ], blending modification [ 9 ] and the addition of a nucleating agent [ 10 ], among which the latter is the most convenient and economical method [ 11 ].…”