Exceptionally rigid and tough ultrahigh molecular weight linear

Details Exceptionally rigid and tough ultrahigh molecular weight linear Exceptionally rigid and tough ultrahigh molecular weight linear

1973-06-18

1976-03-16

Morris, Theodore

Chemistry of carbon compounds

Miscellaneous organic carbon compounds

260 949GD, 264331, 428364, 215 1C, C08F 1400, B29J 100, C08F 1002

Patent

active

039445364

ABSTRACT:
Linear ultrahigh molecular weight polyethylene exhibiting a unique combination of rigidity and toughness and the process for the preparation thereof comprising inducing crystallization of the molten polyethylene at temperatures in the range of about 150.degree. to about 270.degree.C. by rapidly increasing the pressure applied from an initial level of about 1 to about 1000 atmospheres or more depending on temperature to a second level of about 2000-7000 atmospheres and higher and then cooling rapidly while maintaining a pressure sufficient to maintain the linear polyethylene in the solid phase until the temperature is below the crystalline melting point of linear polyethylene at atmospheric pressure. The resulting rigid, tough linear ultrahigh molecular weight polyethylene having a crystalline melting point of 142.degree. to 148.degree.C. at atmospheric pressure, as measured by differential thermal analysis, and by the absence of detectable low-angle X-ray scattering peaks indicative of crystalline spacings in the range of 50 A to 2000 A and by the presence of a predominance of fold spacings of about 10,000 A as determined by electron microscopy, and further characterized by exhibiting at room temperature an elastic modulus in the range of 165,000 to 500,000 psi., a density of 0.95 to 0.98 gram/cc at 25.degree.C. and a tensile impact strength in the range of 125-600 ft.lb/in.sup.2.

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Kirk-Othmer, Encylopedia of Chemical Technology, 2nd Ed., Vol. 14 pp. 259-278 TP E68. C.
Crystallization of Polyethylene at Elevated Pressures, D. V. Rees et al., Journal of Polymer Science Vol. 9, pp. 385-406 (1971).
Extended-Chain Crystals, Davidson et al., Journal of Polymer Science Vol. 7, 2054-2059 (1969)

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