Viscous-Elastic Effects in a PA 6 Melt – Cause of Unevennesses in Melt-Spun Yarns**

Abstract

Abstract The paper deals with dynamic investigations for qualitative and quantitative estimation of the transition behaviour of a PA 6 melt spin equipment in the velocity range of 2 500 to 4 000 m/min. On-line measured time functions of yarn tensile force, yarn fineness and yarn tension, which are caused by determined spinning pump revolution number changes, have been evaluated to estimate the length of disturbed yarn with changed properties. Between spinning pump disturbances and the resulting yarn quality disturbances the delay time constant could be estimated with a typical size of about 1 s. Some hundred meter of yarn are disturbed in their properties during such a transition process. The main cause for the delayed cause-effect-transition could be found in the compression modulus of the melt between the spinning pump and the spinneret. The described dynamic step investigations permit to use a spinning equipment as a measuring system to estimate the compression modulus of melt spinnable polymers.