The effect of heat transfer coefficients and thermal conductivity on polymer processing simulation.

The effects of heat transfer parameters key to industrial processing have been identified via polymer injection moulding process simulation. Moldflow finite element analysis software has been used to simulate injection moulding of components to investigate the relationship between injection moulding processing conditions and the effects of material properties on the moulding process. The effects of core and cavity side heat transfer coefficients, thermal conductivity and component thickness upon the injection moulding cycle time have been examined. Time to freeze for a moulding decreased with increasing polymer thermal conductivity, this effect becoming less pronounced with decreasing moulding thickness. Maximum injection pressure for a moulding increased with increasing polymer thermal conductivity with this effect becoming less pronounced with increasing moulding thickness. For a component, time to freeze decreased with increasing average heat transfer coefficient, although an effective lower limit to time to freeze was reached when core and cavity heat transfer coefficients values were set at 10,000 W/(m2.K) or above. These values for core and cavity heat transfer coefficients also set an effective upper limit for the maximum injection pressure for a component. Setting both core and cavity heat transfer coefficient values at 500 W/(m2.K) gave the lowest times to freeze and the lowest maximum injection pressures for all thicknesses. Setting the heat transfer coefficient values to 4,000 W/(m2.K) and 6,000 W/(m2.K) for core and cavity or cavity and core sides, respectively, produced the shortest time to freeze and highest maximum injection pressures of all the cases where the heat transfer coefficients were set at different values. The study has helped to improve understanding of the heat transfer taking place during injection moulding.