Influence of stereoirregularities on the formation of the γ-phase in isotactic polypropene

• Published in: Polymer (Guilford) 2001, Vol.42 (10), p.4597-4603
• Main Authors: Thomann, R., Semke, H., Maier, R.-D., Thomann, Y., Scherble, J., Mülhaupt, R., Kressler, J.
• Format: Article
• Language: English
• Subjects: Applied sciences; Crystallisation; Crystallization; Exact sciences and technology; Gamma phase; Isotactic polypropene; Organic polymers; Physicochemistry of polymers; Properties and characterization
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/S0032-3861(00)00675-3

Medium to high molar mass isotactic polypropenes with different amounts of stereoirregularities were characterised with respect to their crystallisation behaviour and for comparison a random copolymer of ethene and propene with 5.8 wt% ethene is used. The influence of stereoregularity and crystallisation temperature on the γ-content of the crystallised samples is studied by means of wide angle X-ray scattering, atomic force microscopy and light microscopy. The paper deals also with the temperature rising elution fractionation of an i-PP with large amounts of stereoirregularities and the influence of a nucleation agent on the γ-content. It is shown that effects which render the chainfolding in lamellae more difficult, enhance the formation of the γ-modification. The necessity of chainfolding in isotactic polypropene is discussed in terms of a model that is based on the number of chains that emerge from the lamellae surfaces of the α- and the γ-modification, respectively.