Abstract
A set of polypropylene (PP) fractions with similar molecular masses and distributions but different isotacticities have been studied through wide-angle X-ray diffraction, small-angle X-ray scattering and differential scanning calorimetry measurements. The crystal unit-cell parameters, crystallinity, apparent crystal size and lamellar crystal thickness are found to be dependent on crystallization temperature and isotacticity. The equilibrium thermodynamic properties (melting temperature and heat of fusion) for these PP fractions were determined following two extrapolation methods. These fractions can be thought of as stereo-copolymers, with configurational defects along the chains. A uniform inclusion model proposed by Sanchez and Eby can be applied to describe the crystals formed in these fractions. Both equilibrium and non-equilibrium data are discussed.
Published Version
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