Studies of blends of topologically distinct samples of the polymer of intrinsic microporosity PIM-1 provide, for the CO2/N2 gas pair, insight into the optimum loop topology required for high selectivity and permeance of thin film composite (TFC) membranes.

Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. AbstractThis paper describes the theoretical prediction, finite element simulation and experimental studies of extrudate swell in monodisperse and bidisperse polystyrenes. We present a molecular approach to understanding extrudate swell using the tube-model-based Rolie-Poly constitutive equation within a Lagrangian finite element solver. This yields theoretical predictions of swelling which show a close universality: the molecular weight dependence of the swelling can be removed when the flow speed is scaled by the Rouse Weissenberg number. The roles that both chain orientation and stretch play in determining extrudate swell are clearly identifiable from plots of swelling ratio against each Weissenberg number. We also present isothermal extrusion experiments on the same polymers and can obtain good predictions well into the strong chain stretching regime. The predictions for swelling ratios match those from experiments up to Rouse Weissenberg numbers of ~7, above which swelling is over-predicted by the Rolie-Poly equation.

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A method for predicting the optimal conditions for polymer extrusion, which relies only on gramscale laboratory experiments for two commercial polystyrene samples with two molecular weights is demonstrated by oscillatory rheology. These enable a shear viscosity map vs. temperature and shear rate to be constructed, together with the positions for the major molecular timescales. Alternative methods for characterising rheology, including melt flow index and capillary rheology measurements were also employed, but these do not give the same level of understanding of flow behaviour. The capillary tests generates die swell and this complex behaviour can be seen to collapse onto a single line regardless of temperature when plotted using the Rouse-Weissenberg number. The full shear viscosity map, together with the polymer timescales serves as a design tool to predict processing behaviour for melt processors. The work represents and builds on major academic-industry collaborative research programmes.