Structure and morphology of poly(propylenes): a molecular analysis

The effect of molecular mass on the polymorphism and crystalline structure of isotactic polypropylene

“…Semicrystalline iPP is a polymorphic material, with several crystalline modifications including the monoclinic (α), the trigonal (β), and the orthorhombic (γ) forms [1][2][3][4]. iPP crystallizes essentially into α-modification under traditional processing conditions.…”

“…Moreover, the γ-crystallization tendency of 1-pentene copolymers was even higher than that of samples containing ethylene or butylene comonomer units. The structural features of γ-iPP was studied by Lotz and his co-workers [2]. They found that γ-modification forms within the α-phase on the lateral surface of α-iPP crystallites (α-γ lamellar branching).…”

Crystallization of Polypropylene: Application of Differential Scanning Calorimetry Part Ii. Crystal Forms and Nucleation

“…Normally, the melting point of the β-form lamellae is near 152 to 164 o C, while the melting of the α-form lamellae occurs above 164 o C. Moreover, the α-form lamellae can still grow in the temperature range from 152 to 164 o C. Suppose now that α-crystals grow from the melt of a newly melted adjacent β-crystal. The α-crystal requires an equal mixed of right-and left-handed helices, while the newly created melt of the β-crystal will have only one of these types [42][43][44].…”

Controlled Crystallization of Isotactic Polypropylene Based on α/β Compounded Nucleating Agents: From Theory to Practice

“…Moreover, iPP exhibits a very interesting polymorphic behavior (Awaya, 1988;Busse et al, 2000;Lotz et al, 1996;Vagar, 1992). At least five modifications: monoclinic form, trigonal form, orthorhombic form, and smectic phase have been reported.…”