Seyed Tohid Ghaznavi - Department of Chemical Engineering, Amirkabir University of Technology, Tehran, Iran
Seyed Reza Ghaffarian - Department of Chemical Engineering, Amirkabir University of Technology, Tehran, Iran
Seifollah Jamalpour - Department of Chemical Engineering, Amirkabir University of Technology, Tehran, Iran

Polypropylene (PP) is characterized by four different crystalline phases that which include monoclinic (α), hexagonal (β), orthorhombic (γ), and mesomorphic (smectic). The nucleation ofthese different polymorphs depends on the crystallization conditions. The commonly observed crystalline phase ofpolypropylene is -phase ( -PP). The -phase ( -PP) nucleates in the presence of -nucleating agent or under specific conditionsof temperature gradient and strain. The γ-phase of iPP is usuallyobserved as a co-crystallized component with and within the α- phase spherulites. It could be largely produced by crystallizationat elevated pressures. However, some specific conditions, such as very low molecular weight (Mw < 6000 g/mol), or a relativelylarge number of stereo- and regio-irregularities in the chain, or small amounts (3-10%) of random comonomers (ethylene, 1- butene) could induce crystallization of γ-iPP [1-2]. In this paper, we investigate the effects of temperature variation as processing condition in formation of the γ-phase