Abstract: An improved process is provided for the formation of a high performance polyester (at least 85 mol percent polyethylene terephthalate) multifilament yarn. The product possesses a high strength (at least 7.5 grams per denier) and an unusually stable internal structure which renders it particularly suited for use in industrial applications at elevated temperatures. The filaments are melt spun and uniformly quenched under relatively high stress conditions (as described) to yield an as-spun filamentary material of relatively high birefringence (+9.times.10.sup.-3 to +70.times.10.sup.-3) which is passed in-line from the quench zone to a first draw zone where it is drawn at a draw ratio of 1.01:1 to 3.0:1, and subsequently is drawn (as described) to achieve at least 85 percent of the maximum draw ratio of the as-spun filamentary material. The resulting filamentary material exhibits unusually low shrinkage and hysteresis characteristics (i.e. work loss characteristics) as well as the high strength chatracteristics.

Abstract: An improved polyester filament (i.e., a principally polyethylene terephthalate filament) suitable for use in commercial applications is provided having a unique internal structure. The filament possesses an interconnected highly oriented crystalline microstructure coextensive with its length coexisting with an interdispersed substantially disoriented non-crystalline phase. The filament microstructure imparts inter alia a propensity for the filament to undergo a low degree of shrinkage under a high degree of force at an elevated temperature as evidenced by a modulus ratio (as defined) of at least 0.1. The filament exhibits a relatively high initial modulus, coupled with a relatively high crystalline orientation function, and a relatively low amorphous orientation function.

Abstract: An improved high performance polyester (at least 85 mol percent polyethylene terephthalate) multifilament yarn possessing a novel internal structure is provided. The multifilament yarn of the present invention possesses a high strength (at least 7.5 grams per denier) and an unusually stable internal structure which renders it particularly suited for use in industrial applications at elevated temperatures. As described in detail hereafter the subject multifilamentary material exhibits unusually low shrinkage and hysteresis characteristics (i.e. work loss characteristics) coupled with the high strength characteristics normally associated with polyester industrial yarns. Accordingly, when utilized in the formation of a tire cord and embedded in a rubber matrix, a highly stable tire may be formed which exhibits a significantly lesser heat generation uon flexing.