The high-temperature crystallization of the β-modification of polypropylene (β-IPP) induced by an active β-nucleating agent was studied by polarizing light microscopy. It was established that, in the early stage of crystallization of β-IPP, hedrites were formed as precursors of the spherulitic crystallization. Hedrites seen flat-on were characteristic hexagonal formations (hexagonites) with low birefringence. The central core of hexagonites had positive birefringence. Hedrites seen edge-on were rod-like formations with strong negative birefringence which would transform into a radially symmetric spherulitic form through sheaf-like then oval (ovalite) arrangements. Hedrites may reach considerable sizes (several hundred micrometers). At temperatures of isothermal crystallization higher than the critical (T(βα) = 140 -C), hedrites with mixed polymorphic structures of α- and β-modifications were formed.
|Number of pages||7|
|Journal||Magyar Kemiai Folyoirat, Kemiai Kozlemenyek|
|Publication status||Published - aug. 1 1997|
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