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Studies on melt spinning. VI. The effect of deformation history on elongational viscosity, spinnability, and thread instability
Author(s) -
Han Chang Dae,
Kim Young Woo
Publication year - 1976
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1976.070200613
Subject(s) - materials science , rheology , capillary action , extrusion , composite material , polypropylene , spinning , melt spinning , isothermal process , shear rate , instability , viscosity , capillary number , aspect ratio (aeronautics) , thermodynamics , mechanics , physics
The effect of deformation history on the elongational behavior and spinnability of polypropylene melt was investigated by carrying out isothermal melt‐spinning experiments. For the study, spinnerettes of different die geometries were used to investigate the effect, if any, of the entrance angle, the capillary length‐to‐diameter ( L / D ) ratio, and the reservoir‐to‐capillary diameter ( D R / D ) ratio on the elongational behavior of molten threadlines. An experimental study was also carried out to investigate the phenomenon of draw resonance in the extrusion of polypropylene melts through spinnerettes of different die geometries. Draw resonance is the phenomenon which gives rise to pulsations in the threadline diameter when the stretch ratio is increased above a certain critical value. The results of our study show that the critical stretch ratio at which the onset of draw resonance starts to occur decreases as the L / D ratio is decreased, as the entrance angle is increased, as the D R / D ratio is increased, as the melt temperature is decreased, and as the shear rate in the die is increased. Of particular interest is the observation that, at 180°C, the severity of fiber nonuniformity increases as the stretch ratio is increased, whereas at 200°C and 220°C, the severity of fiber nonuniformity first increases and then decreases as the stretch ratio is increased considerably above the critical value. A rheological interpretation of the observed onset of draw resonance is presented with the aid of the independently determined rheological data.