Modelling And Simulation Of Morphological Evolution For Polymer Blends In Injection Molding

Numerical prediction of morphology in polymer blends is of vital importance in mastering of material structure and property optimization from both theoretical and industrial views. Existing injection molding analysis could not meet the accuracy of practical engineering, as it only deals with the macro moldability of products ignoring the effect of micro morphology. And current theoretical research of morphology in polymer blends focuses on discrete dispersion without considering the interaction of droplets, which could not be applied in the simulation of practical process.A systematical study was conducted on the morphological simulation in injection molding for polymer blends, including the mechanism study, model selection, process simulation and experimental validation.The principle and crucial factors in the evolution of dispersions (specifically the deformation, break and coalescence) were investigated. Simulation results of common models in simple flows were compared and evaluated. The affine deformation model was applied in describing transient large deformation under large strains, and the phenomenological model was chosen in small deformation and retraction of droplets. For the breaking process, the drop splitting model and thread break model were adopted, with the empirical and probability models for the coalescence description.Three dimensional transient processing and morphological evolution were modeled at macro and micro scales. A coupled numerical simulation of flows and morphology was proposed. The stabilized finite element formations were built with the PSPG (Pressure-Stabilizing/Petro-Galerkin) and SUPG(Steamline-Upwind/Petrov-Galerkin) method. The morphological changes under the integrated effects of different factors in real flows were reflected through the iteration of microstructure and macro flows.Morphology in polymer blends was investigated with both experimental and numerical methods. A systematical experimental process was completed to obtain the material parameters needed in the simulation and to study the morphologySimulations of macro flows and micro morphology were validated through the comparison of numerical simulation and experimental results. It shows that the proposed simulation method could represent the morphological changes of dispersion well and be adopted in the calculation and prediction of morphology in injection molding.Distribution of macro flows and micro morphology was simulated under different processing conditions in order to explore the internal relation betwwen external flows and morphlogy. It was found that the effects of processing parameters on the morphological changes were interactive, which requires an integrated analysis and evaluation.Phase separation and inversion were finally studied, and the relation between the static mechanical property and phase morphology was investigated by comparing the morphology and mechanical results.