The influence of resin characteristics on the high speed melt spinning of isotactic polypropylene. II. On‐line studies of diameter, birefringence, and temperature profiles

Abstract

synopsisAn investigation was carried out of the high speed melt spinning of three polypropylene resins with melt flow indices of 12, 35, and 300. On-line measurements were made of +ameta, birefringence, and temperature as a function of distance from the sphneret for a range of spinning conditions for each polymer. A plateau (decrease of cooling rate) in the temperature profile was associated with the Occurrence of crystallization in the spinline. The position of this plateau correlated with a rapid rise in the birefringence profile and a rapid decrease in the rate of drawdown in the diameter profile. The temperature and birefringence profilea were used to determine the temperature and position on the spinline at which the onset of crystallization occurred. It was found that the position and temperature of crystallization onset varied considerably with changes in takeup velocity, extrusion temperature, and resin melt index (weight average molecular weight). The crystallization onset occurred nearer the spinneret and at higher temperatures with (1) an increase of take-up velocity, (2) a decrease of extrusion temperature, or (3) a decrease of reain melt flow index. An analysis was carried out to estimate the rate of stress development with distance along the spinline; the reaults were also used to estimate the stress at the onset of crystallization for each spinning condition. It was concluded that the observed behavior could be attributed to the role of spinline stress in producing molecular orientation and consequent increase of crystallization rate.

Crystallization study on absorbable poly(p‐dioxanone) polymers by differential scanning calorimetry

“…It is well documented in the literature [1][2][3][4][5] that the final physical properties and product performances of polymeric medical devices are controlled not only by chemistry, but also by the morphology of the macromolecular chains. A variety of experimental techniques such as dilatometry, 6 differential scanning calorimetry, 7 X-ray diffraction, 8 hotstage optical microscopy, 9 scanning electron microscopy, 10 dynamic mechanical analysis, 11 dielectric relaxation spectroscopy, 12 light scattering, 13 birefringence, 14 and Raman spectroscopy 15 have been already proven as valuable tools for assessing morphological changes during crystallization. The knowledge gained from these measurements could aid in the understanding of structure-process-property relationships in absorbable synthetic polymers, improve current products and process control, and open up the possibility of producing commercial devices in entirely new areas.…”

Melt spinning of metallocene catalyzed polypropylenes. I. On‐line measurements and their interpretation

“…The melt spinning of isotactic polypropylene (iPP) into fibers has been studied since the early 1960s and continues today. Much of the early work was reviewed in previous articles from our laboratory and in various review articles 1–6. The bulk of the earlier published research dealt with resins that were produced by Ziegler–Natta catalyst systems.…”

Crystallization study on absorbable poly(p-dioxanone) polymers by differential scanning calorimetry

“…It is well documented in the literature1–5 that the final physical properties and product performances of polymeric medical devices are controlled not only by chemistry, but also by the morphology of the macromolecular chains. A variety of experimental techniques such as dilatometry,6 differential scanning calorimetry,7 X‐ray diffraction,8 hot‐stage optical microscopy,9 scanning electron microscopy,10 dynamic mechanical analysis,11 dielectric relaxation spectroscopy,12 light scattering,13 birefringence,14 and Raman spectroscopy15 have been already proven as valuable tools for assessing morphological changes during crystallization. The knowledge gained from these measurements could aid in the understanding of structure–process–property relationships in absorbable synthetic polymers, improve current products and process control, and open up the possibility of producing commercial devices in entirely new areas.…”