Coextrusion of it‐polypropylene film

Abstract

Synopsisit-Polypropylene films were coextruded by using dies of varying extrusion draw ratio (EDR) from 2-10. Among the resulting films, the film coextruded at EDR 9 possesses the most attractive superstructure and the highest modulus. The dynamic modulus at room temperature was 7 GPa and an a, dispersion peak occurred at 100°C in E"-temperature curves, which is higher by about 2OoC than that of the multistep zone-drawn and zone-annealed fibers previously reported. Further, to prepare films with higher draw ratio and higher modulus, repetition of the coextrusion was attempted. Consequently, the draw ratio and the E' at room temperature reached 12 and 13 GPa, respectively. The present paper discusses changes in molecular orientation, crystallinity, uniformity of the superstructure, and dynamic viscoelasticity, with increasing of the used EDR and repeating the coextrusion with some combinations of EDR.

Mechanical properties and superstructure of isotactic polypropylene fibers prepared by continuous vibrating zone‐drawing

“…To date many studies have been carried out in the development of high-performance isotactic polypropylene (i-PP) with high modulus and tensile strength: Kunugi et al 1,2 reported that the zone-annealed i-PP fiber had a storage modulus (EЈ) of 21 GPa at room temperature, and that the film drawn at an extrusion draw ratio of 12 by coextrusion had EЈ ϭ 13 GPa at room temperature; Wills et al 3 studied the effect of molecular weight on the drawing behavior and structural characteristics of ultra high modulus products. They reported that the polymer with M w ϭ 181,000 had the highest modulus of 18 GPa; Taraiya et al 4 reported that the tensile modulus of a die-drawn i-PP increased with draw ratio and reached 16.4 GPa at a draw ratio of 19.5; Peguy and St. John Manley 5 showed that the films prepared by drawing dry gels of high molecular weight i-PP had a tensile modulus of 36 GPa and tensile strength of 1.03 GPa.…”

Drawing behavior and characteristics of laser‐drawn polypropylene fibers

“…As is commonly known, high modulus and high strength can be achieved by the aligning and straightening of polymer molecules in an axial direction. Based on this, various methods, such as zone‐drawing/zone‐annealing,5 coextrusion method,6 continuous vibrating zone‐drawing,7, and so forth, have been adopted till now to enhance the performance of PP fiber. In all the methods, at least two or multiple stages of drawing or annealing were required.…”