Published in: Macromolecules, 2007
Volume 41, Issue 3, Pages, 826-833
Authors: H. Zhu, B. Monrabal, C. C. Han, D. Wang.
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Systematic investigation on the compositional heterogeneity, phase structure the crystallization and subsequent melting behavior of two polypropylene in reactor alloys (EB-P, EP-P) were conducted. The composition of the alloys and the chain structure of each component were characterized by combinatorial using of preparative TREF and 13 C-NMR technique. The compositional heterogeneities of both samples were further studied by SSA technique, and possible thermal fractionation mechanisms were then inferred. Correlations between the mechanical properties and the molecular architecture and phase structures were discussed. The results show that the excellent balance between toughness and rigidity of sample EB-P primarily benefits from the crystalline polyethylene homopolymer (HPE) phase and the amorphous ethylene-olefin copolymer (EC) component, which is proved to be enriched in the interface between the dispersed phase polypropylene homopolymer (HPP) and the matrix and the matrix (HPE). As for EP-P sample, the very high amorphous EC content, and the homogeneous and interpenetrating co-continuous phase structure in the alloy are considered to be mainly responsible for the outstanding low-temperature impact toughness.