The crystallization of semi-crystalline polymers is often influenced by processing

and their crystallization may also influence the processing simultaneously.The present study is an attempt to simulate the two aspects of the injection moldings of semi-crystalline polymers.Firstly

by assuming that the effect of flow on crystallization is only in terms of increasing the crystallization rate constant

an approach based on the quiescent-state crystallization equation is proposed to develop the qualitative description of crystallization phenomena under non-isothermal flow occurring in injection molding processing.The energy of dissipation

the work of stress occurring in the injection molding operations

is regarded as the main parameter of the equation of the crystallization rate.Secondly

the proposed modeling of the flow-induced crystallization kinetics is directly applied to predict the development of the crystallinity during the injection moldings of two semi-crystalline polymers:fast-crystallizing polymer isotactic polypropylene (iPP) and slow-crystallizing polymer polyethylene terephthalate (PET).In the prediction

the kinetics of crystallization is considered in the simulateion of three stages:filling

packing and cooling of injection molding

and the parameter reflected the effect of crystallization is included in the equation of the relationship of stress and strain

along with the equations of continuity

momentum and energy conservation

the equation of state and other parameters of materials;the flow-induced effect is also considered and the energy of dissipation is regarded as the main parameter in computing the kinetics of crystallization.Finally

the conclusion can be drawn after the simulated data for the development of crystallinity and the distribution of temperature and pressure field in the moldings are compared and analyzed.Although the results show the kinetics of flow-induced crystallization has little influence during the process of computing the distribution of the pressure field

it is obvious that the processing can expedite crystallizing

and the crystallization also influences the processing of materials especially the temperature field distribution for the packing and cooling stages of injection molding of the iPP and PET.The result shows also that the proposed kinetics model has a minimum of unknown material constants and predicts the most prominent features of flow-induced crystallization.In addition

comparison is also made between PET and iPP

and it demonstrates that the mutual influence of flow and crystallization kinetics is different during the injection molding process for materials with different crystallization properties.For the fastcrystallizing polymer iPP

flow has little effect on the final crystallinity but relatively higher heat release and large influence of the distribution of the temperature field in the injection molded parts

and the situation for PET is opposite.