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US 4,348,350 AGranted
Ultra-drawing crystalline polymers under high pressure
AssigneeMichigan Molecular Institute
InventorsDale J. Meier, Leszek Jarecki
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AssigneeMichigan Molecular Institute
InventorsDale J. Meier, Leszek Jarecki
Estimating the term…
A solid crystalline organic polymer is made into a filament, rod, or film by ultra-drawing it at a temperature within 70.degree. C. of but below its melting point at the operating pressure while subjecting the polymer during and immediately after drawing to a hydrostatic pressure of at least about 500 atmospheres applied by a fluid medium inert to the polymer. High-density polyethylene and isotactic propylene are preferred polymers. A draw ratio of at least 20:1, and as high as 60:1, may be used. Pressure may be up to 2500 atmospheres or more. The rate of drawing for polyethylene is above 500 percent per minute. The ultra-drawn products are transparent, essentially free of internal voids, and exhibit very high tensile moduli of elasticity, up to 65 to 70 Giga-Pascals in the case of polyethylene.
A process of making transparent high-modulus polymer filament, rod, or film which comprises ultra-drawing a crystalline organic polymer in the solid state at a temperature within 70.degree. C. of but below its melting point at the operating pressure while subjecting the polymer during and immediately after drawing to a hydrostatic pressure of at least about 500 atmospheres by a medium inert to the polymer, thereby to restrain void formation in the polymer during ultradrawing and render the product transparent.
In a process of making high-modulus polymer filament, rod, or film by subjecting a crystalline organic polymer to ultra-drawing by applying stretching force in the solid state at a temperature within 70.degree. C. of but below its melting point at the operating pressure, under conditions which at atmospheric pressure cause formation of voids in the drawn product and render it opaque, the improvement which comprises applying to the polymer during and immediately after drawing hydrostatic pressure by means of a medium inert to the polymer, such pressure being at least 500 atmospheres and sufficient to restrain void formation and render the product transparent.
Dependencies are inferred from the claim text.