Morphologies and Crystallization Behaviors in Melt-Miscible Crystalline/Crystalline Blends with Close Melting Temperatures but Different Crystallization Kinetics

作者：Lijun Ye, Cuicui Ye, Kangyuan Xie, Xianchun Shi, Jichun You, Yongjin Li · 发表于：Macromolecules · 年份：2015 · DOI：10.1021/acs.macromol.5b01904 · 被引用次数：33 · 研究领域：Material Dynamics and Properties、Polymer crystallization and properties、Crystallization and Solubility Studies

Poly( l -lactic acid) (PLLA) and poly(oxymethylene) (POM), with very close melting temperatures ( T m ), can crystallize simultaneously or separately in their blends depending on composition and crystallization temperature ( T c ), resulting in various types of morphology. It is mainly attributable to the greatly different crystallization kinetics of PLLA and POM. At a content of POM (φ POM ), 3 wt % < φ POM < 20 wt %, PLLA crystallization kinetics are comparable to POM, and therefore two type spherulites exhibit “side-by-side” simultaneous growth with the penetration of PLLA spherulites into POM crystals. Although crystal growth rate ( v c ) of POM is still a bit faster than that of PLLA, for φ POM = 3 wt %, the nucleation of POM is restrained and POM spherulites can only develop on the propagating PLLA growth fronts with the generation of novel “core–shell” blended spherulites. For 20 wt % ≤ φ POM < 80 wt %, interspherulitic growth of PLLA inside the pre-existing matrix of POM spherulites causes the formation of interpenetrated blended spherulites, owing to the large discrepancy in kinetics. At φ POM ≥ 80 wt %, PLLA molecular chains are redistributed into the interlamellar level regimes within the POM spherulites and can only crystallize into tiny crystals (owing to strong confinement). PLLA/POM blends provide a perfect example and new insights for understanding the crystallization of miscible crystalline/crystalline polymer blends (with very similar T m ’s), in which kinet...