Abstract: 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.

Abstract: 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.