Studies on the flow behavior of plasticized thermoplastic molding compounds in injection molding through narrow nozzles
In the transformation from the melt chamber plasticizing unit into a forming mold plastic melts must often pass through very narrow channels. In narrow channels, they are usually subjected to high shear stresses. These depend on the pressure, temperature and geometry of the de flowing through channels to off. Measurements were made in molds with small-sized sprues and in numerous performed separately fabricated channels. In an experimental tool, the back pressure could be varied during the filling to set the superimposed static pressure when filling in a reproducible way can. In numerous experiments, the shear heating of compounds and the temperature rise in several narrow flow channels were recorded. It could be shown that lubricants in plastics and the addition of regrind that iA suffered a loss of additives that influence the pressure drop in the flow channel and the shear heating.
The amount of shear heating can be relatively accurately described by a formula, the pressure loss in flow channels, the specific heat and the work conditions considered in the specific volume. A part of the investigation was aimed at the changes in the intrinsic viscosity, the entropy elasticity, the normal stress (Weißenberg ) to investigate effect. Also it was observed that the thixotropy can occur similar flow behavior. Numerous test results seem to show that the Bagley correction of nozzle length for very short channel lengths, a correction needs.
Solved with the pseudoplastic fluid model of polyvinylpyrrolidone in water could be made at the inlet of channel narrowing occurring circulating vortex visible. For some plastics have been given instructions to optimize the geometry of pin gates.Lesen Sie die deutsche Zusammenfassung auf Kunststoffe.de
Melt-flowbehavior, narrow canals, shear heating, small prues, lubricants, pressureloss, shear thinning, Weißenberg-Effect, thixotropy
Institute / chair: Fakultät für Maschinenwesen der Rheinisch-Westfälischen Technischen Hochschule
Technical consultant for expert services: Prof. Dr.-Ing. G. Menges (Betreuer), Prof. Dr.-Ing. A. H. Hennig, Prof. Dr.-Ing. K. Krekeler
Publication year: 1968
Provider: Wissenschaftlicher Arbeitskreis Kunststofftechnik (WAK) / Kunststoffe.de
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