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. 2021 Jun 2;13(11):1851.
doi: 10.3390/polym13111851.

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

Hye-Seon Park  1 , Chang-Kook Hong  1
Affiliations

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

Hye-Seon Park et al. Polymers (Basel). .

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.

Keywords: PDLA; PLLA; homo crystallization; mechanical properties; stereocomplex crystallization.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Structure scheme of (a) PLLA, (b) PDLA.
Figure 2
Figure 2
DSC curves of the PLLA/PDLA of different compositions. (x/y refers to the blending ratio between PLLA and PDLA).
Figure 3
Figure 3
Degree of crystallinity (Xc) of the PLLA/PDLA blends with different contents of PDLA.
Figure 4
Figure 4
TGA thermograms of the PLLA/PDLA blends with various compositions.
Figure 5
Figure 5
Polarized optical micrograph of PLLA/PDLA blends with different ratio (a) neat PLLA, (b) neat PDLA, (c) PLLA/PDLA (9/1), (d) PLLA/PDLA (8/2), (e) PLLA/PDLA (7/3), (f) PLLA/PDLA (6/4), (g) PLLA/PDLA (5/5).
Figure 6
Figure 6
XRD curves of the PLLA/PDLA blends with various compositions.
Figure 7
Figure 7
Storage modulus curves with different compositions of PLLA/PDLA dependence of temperature.
Figure 8
Figure 8
Loss factor tan δ curves with different compositions of PLLA/PDLA dependence of temperature.
Figure 9
Figure 9
Mechanical properties of the PLLA/PDLA blends with different compositions. (x/y refers to the blending ratio between PLLA and PDLA).
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