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  • Favorable formation of ster...
    Zhao, Zhongguo; Tang, Dahang; Jia, Shikui; Ai, Taotao

    Journal of materials science, 04/2021, Letnik: 56, Številka: 10
    Journal Article

    A feasible approach is proposed to promote the formation of the stereocomplex crystal (S.sub.c) in long-chain branched Poly(L-lactic acid)/Poly(D-lactic acid) (LCBPLA/PDLA) blends with hydrogen bond interactions. The synergistic effect of PDLA and long-chain branches significantly increases the crystalline ability of S.sub.c from 20.1 to 30.4% due to the improved intermolecular crystal nucleation/growth. The frequency-independent loss tangent appeared at a PDLA concentration of 5.0 wt%, indicating a transition from the liquid-like to solid-like viscoelastic and the formation of a network composed of long-chain branches and the reserved S.sub.c crystallites. Changing the processing temperatures from 190 to 230 °C seems to induce different melting behavior of S.sub.c with diverse topological conformations so as to act as a template to attract PLLA molecule chains to perform the crystallization behavior. In situ wide-angle X-ray diffraction analysis reveals that a higher cooling temperature (less than 220 °C) significantly contributes to the S.sub.c with more integrated structures and the H.sub.c-to-S.sub.c transition. The polarizing optical microscope results show that increasing the PDLA content and long-chain branched points significantly promote the spherulite growth and nuclei density of S.sub.c, increasing the S.sub.c size from 56.47 to 94.13 mum and nuclei density from 52.2 to 98.3%.