The flow of molten polymers in molds is described by -the conservation of mass, momentum, and energy. Several simplijications have been proposed in the lust 40 years. The early models were essentiaUy unidirectional approximations. More recently, the Hele-Shaw flow approximation has been used together with the appropriate analytical or numerical methods. Current developments include commercially available computer software based on network models for flow simulation in complex molds and modern sophisticated finite element solution of the complete conservation equations that give insight to fountain flow and small scale phenomena.
*Financial assistance from the Natural Sciences and Engineering Research
Council of Canada is gratefully acknowledged. H. Mavridis was also the recipient of a Shell Canada Graduate Research Fellowship.
(ii) packing stage: after the mold is filled, high pressure is maintained, and additional melt flows into the cavity to compensate for density changes (shrinkage) during cooling; and (iii) cooling stage: the melt is cooled, and the shaped article is ejected. Further information on the overall injection molding process is provided in Refs. 1-4.
During the filling-packing-cooling cycle the polymer properties, mold design, and molding conditions interact to produce the thermomechanical history experienced by the polymer melt which in turn deter-