Most of the experiments were performed with a single polymer blend (polydimethylsiloxane-polybutene). This allows a full comparison between a large number of different experiments carried out by many different techniques in the three laboratories. We can draw conclusions on four different areas:
Methodologies: light scattering can be effectively used for morphology measurements (size distribution on droplet morphologies, use of transient morphologies to evaluate size and interfacial tension). High resolution optical microscopy/image analysis was developed and rheological tests can be used to measure morphology size.
Deformation of an existing morphology: drop deformation was monitored in shear by many different techniques (optical microscopy, light scattering, dichroism, shear stress, first normal stress difference, oscillatory rheology). Drop deformation was modelled and the results were successfully compared with experiments. An improved model of drop retraction was produced, giving a better estimate of interfacial tension. Stress predictions were obtained with an affine model and the Napoli model.
Change of morphology: the relative contributions of morphology breaking and coalescence were assessed and the direct evidence of these two mechanisms was shown in transient rheology and rheo-optics. There is a good understanding of break-up at rest and during flow at low concentrations. An extensive set of data on coalescence was generated.
Influence of a liquid crystalline phase: no measurable influence of the liquid crystalline character of one phase on interfacial tension or morphology was seen.
The aim of the present proposal is to replace the current empiricism for controlling the morphology of incompatible polymer blends by a scientifically based approach which implies a fundamental understanding of the evolution of the microstructure during processing. This goal will be achieved by designing the necessary experimental tools to quantitatively characterize the morphology in various types of flows. The obtained results will be used to develop models having these morphological parameters built in and to control the microstructure, the functionality and the properties of polymer blends. Moreover, this work will also contribute to a more effective development of new materials. In addition, innovative instruments will be developed to probe the flow-induced structures.
In order to achieve these goals, the following tasks will be performed :
- designing model compounds which reproduce the various morphologies found in industrial blends under conditions suitable for optical observations during flow and where the major governing parameters can be varied systematically.
- designing new rheo-optical devices specifically tailored for the investigation of multiphase polymers. - performing rheological and in-situ characterization (optical microscopy, small-angle light scattering, conservative dichroism...) of morphologies in various flow conditions (shear, elongation; complex 2D and 3D flows). - developing mathematical models to be used in industrial process optimization and materials design.
Funding SchemeCSC - Cost-sharing contracts