Studies on melt spinning. V. Elongational viscosity and spinnability of two‐phase systems

Isothermal melt spinning experiments were carried out to investigate the elongational flow behavior and spinnability of polymer blends and a calcium carbonate‐filled polypropylene. Blends chosen for study were mixtures of polystyrene (Dow Chemical, Styron 678) with high‐density polyethylene (Union Carbide, DMDJ 4309), and mixtures of polystyrene (Dow Chemical, Styron 686) with high‐density polyethylene (Union Carbide, DMDJ 4309). For the study, measurements were taken of the thread diameter by photographic techniques and of the thread tension by means of a Saxl tensiometer. These measurements were later used to determine the elongational viscosity of the material investigated. It was found that, in all the blends and filled systems investigated, the elongational viscosity decreases with elongation rate and that the relationship between the elongational viscosity and blending ratio is very complex. An attempt is made to offer explanations of the observed complicated relationship with the aid of microphotographs of fiber samples, which display the complexity of fiber morphology in two‐phase systems. It was also found that there exists some correlation between the elongational viscosity and the maximum stretch ratio which may be considered as representing fiber spinnability.