E.i. Dupont De Nemours and Company

Sibbley Paul Gauntt

Hua-Feng Huang

Ralph L Heard, Jr

Thomas J Csaky

A process is disclosed for heating never-dried para-aramid fibers containing 20 to 200 wt % water, based on dry polymer weight to form a fiber having a modulus of greater than 800 gpd while retaining a high tenacity. The fibers are heated in one or more microwave resonant cavity applicators to a temperature of 250.degree. C. to 425.degree. C. and preferably 270.degree. C. to 310.degree. C. while under a tension of 0.2 to 10 grams per denier. The preferred para-aramid is poly(p-phenylene terephthalamide). Fibers having a density of less than 1.43 g/cc can be made; and fibers having moduli greater than 1100 gpd can be made.

Process for making para-aramid fibers having high tenacity and modulus

The quality of a resin-bonded twisted string comprised of three flattened monofilaments in a side-by-side relationship is improved when the monofilaments are precoated with resin prior to twisting and then twisted in a zone wherein the excess lengths of the two outer monofilaments in the twisted configuration is compensated for during twisting by forwarding the two outer monofilaments at a positively controlled speed and allowing the speed of the middle monofilament to be controlled by being drawn into the twisting zone through a roller slot guide at a speed freely determined relative to the speed of the two other monofilaments entering the twisting zone.

Process for making integrated racket strings from monofilaments

Heavy denier, polyamide monofils are produced by the coupled steps of spinning, quenching, drawing and winding. Quenching involves passage of the filament through an air gap and a water bath. There are two stages of drawing. In the first stage, pressurized steam is used to deorient surface polymer and as a draw assist. The product is characterized by a surface layer of oriented polymer having reduced orientation relative to the orientation of the core polymer.

Monofilament of polyhexamethylene adipamide having a surface layer of

Heavy denier, polyamide monofils are produced by the coupled steps of spinning, quenching, drawing and winding. Quenching involves passage of the filament through an air gap and a water bath. There are two stages of drawing. In the first stage, pressurized steam is used to deorient surface polymer and as a draw assist.

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Bon Air, VA, United States of America

Sibbley Paul Gauntt