Derivative stress‐strain curves at constant strain rate for polyacrylonitrile copolymer fibers have been obtained by simple modification of conventional tensile testing apparatus. These derivative curves, considerably more complex and eventful than stress‐strain curves, have been interpreted as direct records of changes undergone by the apparent Young's modulus during experiments which extend from infinitesimal strain to failure. Analysis of the data shows that these changes in the apparent Young's modulus cannot be accounted for to any significant extent by viscoelastic time effects and must therefore be consequences of the deformation process itself. In the light of this analysis, it is concluded that polyacrylonitrile fibers “soften” considerably in the strain range 0.5–3% and that they exhibit moderate “hardening” in the strain range which extends from ca 3% to the breaking strain (10%).
The results of extensive research about draw texturing of polyester fiber are presented. Draw texturing was done on a rebuilt Barmag FK 4 production machine. The draw texturing process for which we used false twist spindles was carried out sequentially and simultaneously. The physics of both processes and the combined influence of drawing and texturing on the structural and textile properties of the yarns are discussed. Process parameters like spinning speed, draw ratio, hot-pin temperature, heater temperature, yarn twist, over-feed, and yam tension were included in the tests. By variation of these parameters yam properties were optimized. The physical and textile properties of the yams were tested, with special attention to the uniformity of the yam crimp. A new crimp tester was developed to measure the crimp contraction continuously and give information about the crimp uniformity within short length.The results achieved with simultaneous draw texturing are discussed in detail, especially the influence of the spinning speed (primary spinning) on yarn properties. The properties of sequentially and simultaneously textured yarns are compared with each other and with a conventionally textured yarn.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.