Isothermal and Nonisothermal
Cold Crystallization Behaviors of Asymmetric Poly(l‑lactide)/Poly(d‑lactide) Blends
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Abstract
Isothermal and nonisothermal cold crystallization behaviors
of asymmetric poly(l-lactide) (PLLA)/poly(d-lactide)
(PDLA) blends at PDLA loadings of 0–20 wt % were investigated
in this work. Formation of the stereocomplex in the blends was confirmed
by differential scanning calorimetry and wide-angle X-ray diffraction.
For both neat PLLA and its blends, the overall isothermal cold crystallization
rates increase with increasing crystallization temperature; moreover,
the overall isothermal cold crystallization rates of PLLA are faster
in the blends than in neat PLLA, indicative of the nucleating agent
effect of the stereocomplex formed in the blends. Crystallization
mechanism and crystal structure of PLLA remain unchanged despite the
PDLA loading. For the nonisothermal cold crystallization, the crystallization
process of PLLA is accelerated by increasing both heating rate and
the PDLA loading up to 10 wt %. The Ozawa equation failed to fit the
crystallization process, while the Tobin equation could describe it
well in the relative degree of crystallization range of 0–75%