Uniaxial roll-drawing of isotactic polypropylene sheet

• Published in: Polymer engineering and science 1987-04, Vol.27 (7), p.518-523
• Main Authors: Burke, P. E., Weatherly, G. C., Woodhams, R. T.
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Forms of application and semi-finished materials; Polymer industry, paints, wood; Sheets and films; Technology of polymers
• ISSN: 0032-3888; 1548-2634
• DOI: 10.1002/pen.760270707

The process described as “roll‐drawing” has been applied to commercial extruded sheets of isotactic polypropylene (M̄n = 70,900). Preheated billets were drawn into thin, clear, transparent sheets in a single pass, producing uniaxial orientation of the polymer molecules in the draw direction. At the maximum draw ratio of 20, the ultimate tensile strength and Young's modulus in the draw direction were 0.5 GPa and 20 GPa respectively. The mechanical properties transverse to the draw direction were virtually unchanged. The theory of fiber reinforcement for unidirectional anisotropic plates was applied to interpret the orientation dependence of the stress‐strain behavior of the drawn sheets. From these results, it was estimated that the mechanical properties of biaxially laminated polypropylene sheets equaled the performance of aramid and carbon fiber composites, The roll‐drawing process appears to be economically attractive for the production of ultra‐high modulus crystalline thermoplastics in sheet form having excellent uniaxial or biaxial properties.