Crystallinity enhancement of extruded polypropylene containing poly(vinyl alcohol) fibers prepared in situ

The present paper describes a novel method for reinforcing isotactic polypropylene (PP) by adding poly(vinyl alcohol) (PVA) fibers prepared by melt-stretching. Low-viscosity PVA droplets were deformed into fibers in the molten PP by melt-stretching them beyond the melting point of PVA. When the obtained composite was extruded below the melting point of PVA, the fibers became oriented toward the flow direction. The PVA demonstrated marked nucleating activity with regard to PP crystallization, which was further promoted by enlargement of the surface area by fibrillization. As a result, there was virtually no orientation relaxation of the PP chains with an increase in crystallinity, which explains the improvement in rigidity of the reinforced composite.

Automated summary

This paper presents a novel method for reinforcing isotactic polypropylene (PP) by adding poly(vinyl alcohol) (PVA) fibers prepared by melt-stretching. The PVA fibers were formed by deforming low-viscosity PVA droplets in the molten PP beyond the melting point of PVA. The composite obtained showed increased rigidity due to the orientation of the fibers and the nucleating activity of PVA in PP crystallization.