Pressure and temperature behavior of thermoplastic polymer melts during high‐pressure expansion injection molding

Abstract

The development of expansion injection molding as new technology for producing thin plastic parts has raised questions about polymer melt behavior in the process of rapid high pressure compression and expansion. To investigate those phenomena, the new in-line injection molding machine mounted measurement system has been developed. Measuring nozzle equipped with hydraulically driven closing bolts and contact fast response pressure and infrared temperature sensors enabled us to measure the compression and expansion of polymer melts at different starting conditions. Results presented for high impact polystyrene and polyamide show that polymer melt temperature rise is linearly dependent on compression pressure as well as it is dependent on compression speed. Comparable effect of temperature fall has been recorded during the polymer expansion, resulting in no noticeable loss of dissipation energy during this reversible process. Measurements have been compared with modified 2-domain Tait equation of state. Curve fitting analysis to manufacturer's material data show that measurements fit well with the model, even at very high compression speeds.

Injection molding simulation with variothermal mold temperature control of highly filled polyphenylene sulfide

“…Therefore, the pvT-measurements have been adjusted to the DSC measurement using selected data points as an indicator. Afterwards the extrapolated measurement data were fitted via the 2-domain-modified Tait model [7,8,9] also considering pressure dependencies during measuring. …”

The Influence of Processing Conditions on the Polypropylene Apparent Viscosity Measured Directly in the Mold Cavity

“…This solution resembled the action of a capillary rheometer powered by the plasticizing system of the injection molding machine. Similar tools were used by other researchers . Differences were in geometry and dimensions of flow channels and sensors placement.…”

“…Similar tools were used by other researchers. [16][17][18][19] Differences were in geometry and dimensions of flow channels and sensors placement.…”

Development of a pressure–volume–temperature measurement method for thermoplastic materials based on compression injection molding

“…After blocking the nozzle, the melt was compressed using the screw. Rogelj and Krajnc built a special nozzle that could be attached to an injection molding machine, which enabled them to examine the pvT properties of polymer melts in close to adiabatic conditions. Wang et al built a special injection mold for their measurements and used the clamping force of the machine to create a pressure necessary for measuring.…”