Abstract
AbstractThe flow of polypropylene, nylon 6,6, and 33‐percent glass‐fiber‐filled nylon 6,6 into a tensile bar mold was investigated. Pressures needed to fill the cavity and runner system were measured as a function of fill time and melt temperature. The experimental results were compared to pressures predicted using the Moldflow flow‐analysis programs. Correlation between experimental and predicted pressures was good provided that accurate input data to the computer programs were used. The choice of runner diameter in the approximation of the irregular shaped runner of this tensile bar mold was found to be important, since the runner length was approximately 40 percent of the total flow length. Material properties of particular importance were thermal conductivity, viscosity, and no‐flow temperature (the temperature at which the resin will no longer flow). Viscosity/shear rate/temperature data are needed for the computer programs and two methods of obtaining the data were examined: an Instron capillary rheometer and a capillary nozzle on an injection‐molding machine. Good agreement between the two methods was found for polypropylene over a shear rate range of 100 to 10,000 s−1. Only the injection‐molding capillary nozzle could be used for the nylon‐ and glass‐filled nylon due to the thermal degradation that occurred in the Instron rheometer.
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