VISCOUS-ELASTIC EFFECTS IN A PA-6 MELT - CAUSE OF UNEVENNESSES IN MELT-SPUN YARNS

The paper deals with dynamic investigations for qualitative and quanti tative estimation of the transition behaviour of a PA 6 melt spin equi pment 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 yam with cha nged properties. Between spinning pump disturbances and the resulting yam quality disturbances the delay time constant could be estimated wi th a typical size of about 1 s. Some hundred meter of yarn are disturb ed in their properties during such a transition process. The main caus e for the delayed cause-effect-transition could be found in the compre ssion modulus of the melt between the spinning pump and the spinneret. The described dynamic step investigations permit to use a spinning eq uipment as a measuring system to estimate the compression modulus of m elt spinnable polymers.