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- PósterPhase inversion prediction during the bulk synthesis of high-impact polystyrene: a fluid-dynamic approach(2021-11)"High-Impact Polystyrene (HIPS) is a heterogeneous material constituted by a rubber (PB) particles dispersed in a vitreous polystyrene (PS) matrix. Two typical morphologies are usually identified: ‘salami’ (larger rubber particle with several PS occlusions) or ‘core-shell’ (smaller particle with one large occlusion). The industrial continuous bulk HIPS process involves four main stages: dissolution, pre-polymerization, finishing and evolatilization. During the pre-polymerization, the mixture consists of a continuous PB-rich phase where PS-rich droplets grow as the reaction proceeds. At a critical point, the dispersed vitreous phase reaches a volume such that it becomes the continuous phase, through a co-continuous transition. This is the phase inversion (PI) point, and the material morphology is essentially defined at this stage, characterized by a sudden drop in the mixture’s apparent viscosity."
- PósterFluid dynamics of the phase inversion process in the bulk polymerization of high impact polystyrene(2021)"In the synthesis of HIPS, phase inversion (PI) is the critical point at which a dispersed PS-rich phase becomes a continuous matrix, leaving behind a PB-rich phase as dispersed particles that may contain occluded PS-rich droplets inside (occlusions). The size and shape of these particles essentially determine the mechanical properties of the material, which makes PI a critical point during the reaction. In this work, the most popular mechanism for PI – an imbalance between coalescence and break-up of dispersed particles – is assessed through a population balance model, coupled with a heterogeneous polymerization model. Results are adjusted and discussed with experimental evidence gathered from TEM images."