Polypropylene (PP) is the most widely used polymer for fine/nano filament producing applications such as a meltblown because of its processability, rapid crystallization and easy to drawing into fine fibers. The commercial polypropylene is mostly isotactic with moderate crystallinity. Crystalline polypropylene is in alpha, beta and gamma crystal forms along with in the smectic form in an amorphous state. The triclinic gamma form rarely forms under regular processing conditions. Isotactic PP generally crystallizes into a stable monoclinic alpha form under standard process conditions, sometimes with a very low content of the hexagonal beta form.
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