Novel irradiated polyethylene filaments tapes and films and process therefor
AssigneeStamicarbon B.V.
InventorPieter J. Lemstra
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Abstract
Novel gel-spun, irradiated and drawn ultra high strength high molecular weight and at least partially cross-linked and/or branched polyethylene filaments, tapes and films, exhibiting a combination of substantially lower creep rates, very high heat shrink characteristics and high abrasion resistance properties than corresponding but non-irradiated articles, and with a process for making the same.
Claims25
A gel-spun, irradiated and drawn, and at least partially cross-linked branched ultra high strength polyethylene article in the form of a film, tape or fiber possessing high shrink properties and exhibiting the following characteristics in combination
- (1) a tensile strength of at least (2.3-1.3.times.10 .sup.-2 D) GPa where D is the thickness or diameter of uniaxially oriented tapes and filaments, in .mu.m, or a tensile strength of at least 0.5 GPa in case of biaxially drawn films;
- (2) a modulus of at least 30 GPa;
- (3) a xylene insoluble content of at least 25%;
- (4) an at least 20% retained peak area under the DSC main melting point curve, upon second heating after an initial heating about 170.degree. C.;
- (5) a retention of a retractive force plateau after reaching thermal equilibrium upon heating the fiber to a temperature above about 170.degree. C.;
- and
- (6) retention, after heating and reaching thermal equilibrium above 170 .degree. C. under restraint, of an X-ray diffraction pattern substantially corresponding to the oriented, crystallized polyethylene.
A process for the production of novel irradiated ultra high strength polyethylene filaments, tapes and films which essentially consists in
- (a) forming a solution of a high molecular weight polyethylene
- (b) spinning or extruding said solution through an orifice
- (c) quenching the extrudate from step (b) to a temperature below the gel point of said solution to form a gel-state article in the form of filament, tape or film
- (d) irradiating said gel-state article while in the gel-state
- (e) and drawing or stretching said gel-state article either during or after said irradiation to form a drawn or stretched article composed of at least partially cross-linked or long-chain branched polyethylene molecules having the combination of properties
- (1) a tensile strength of at least (2.3-1.3.times.10.sup.-2 D) GPa where D is the thickness or diameter of uniaxially oriented tapes and filaments, in .mu.m, or a tensile strength of at least 0.5 GPa in case of biaxially drawn films;
- (2) a modulus of at least 30 GPa;
- (3) a xylene insoluble content of at least 25%;
- (4) an at least 20% retained peak area under the DSC main melting point curve, upon second heating after an initial heating about 170.degree. C.;
- (5) a retention of a retractive force plateau after reaching thermal equilibrium upon heating the fiber to a temperature above about 170.degree. C.;
- and
- (6) retention, after heating and reaching thermal equilibrium above 170.degree. C. under restraint, of an X-ray diffraction pattern substantially corresponding to the oriented, crystallized polyethylene.
Dependencies are inferred from the claim text.