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Orientation development in amorphous polymer melts being vitrified in an injection molding process is described. Predictions of orientation development are based on the argument that the stress‐optical laws are valid in the molten stare and birefringence values appropriate to the stress levels at the time of vitrification remain. This theory is compared to birefringence distributions determined in injection molded parts.

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The various mold filling phenomena influencing the charactcristics of fabricated parts are surveyed. The phenomena leading to jetting in injection mold filling are considered. These are associated with the magnitude of swell b y the melt as it exits the gate into the mold. Special attention is given to the influence of non-isothermal runner flow,. A theory of extrudate swell of pol: mer melts with temperature profiles is developed using Tanner's unconstrained recovery theory. In the absence ofjetting, mold filling by a simple advancing front takes place. The hydrodyiianiics of the advancing front and the stress fields in the flowing melt are determined. Analysis and modeling are presented based on the use ofhydrodynamic lubrication theory involving a solid la!,er along the mold wall and a hot isothermal melt core. This theory is compared with experimental measurements ofpressure losses in mold filling. The development of birefringence in injection molding processes is anal>,zecl. Birefringence distributions are due to frozen-in flow birefringence. A new experimental study is presented and its results compared with theoretical predictions. The problem of thermal stresses in injection molded parts is considered.