The configuration and conformational states of the polypropylene chain affect the
crystallization and crystal form of the polymer. The atactic polymer is not
crystallizable as the chain structure lacks regularity. The crystal lattice of the
syndiotactic polypropylene is orthorhombic and the chains in the crystal lattice take
either the (T2G2)2 or a planar zigzag conformation. The isotactic polypropylene can
crystallize into three different crystal forms depending on the temperature, pressure
and mechanical stress state: monoclinic α-, orthorhombic γ- and hexagonal β-forms
6
,9. There also exists a liquid crystalline sc. smectic form which recrystallizes to α-
form during heating. The α-form is the most common. β-crystals are found is
systems crystallizing under shear. The γ-crystals are formed only under high
pressure in high molar mass homopolymer polypropylene. Polypropylene samples