Polymer processing includes unit operations such as compression, injection and blow moulding and extrusion through a variety of dies. Specifically for the polymer industries, materials characterisation is of critical importance (including fluid related issues like sedimentation, time related structural decay or build-up and post-cure issues like strength of compression or extension) for prediction and management of sharkskin, melt fracture, calendering, die swell, melt homogeneity and short- and long-term dimensional stability of extrudates or moulded parts. These processes depend on fluid rheological parameters such as viscosity, visco-elasticity, creep and recovery, and solid material properties such as behaviour under various compressive and extensional loading conditions. Extensional flow properties dominate processes where stranding occurs and influences time, quality and energy requirements.
The Rheology Solutions applications laboratory has state of the art equipment, capable of measuring all of the above parameters, and of providing interpretation of the results where necessary. Laboratory equipment includes highly sensitive, specialised, modern instrumentation and sensor systems, for measuring complex or difficult fluids such as those with very low viscosity, or those with a highly settling solid phase, or liquids with significant extensional or visco-elastic properties. Solid material properties according to various international standards can also be monitored. Information such as shear viscosity curves, thixotropic behaviour and flow curves may be obtained for interested clients. Additionally, of importance to the industry, when scientifically assessing changes in flow behaviour due to temporal or ingredient issues, viscoelastic moduli as a function of temperature (up to 250ºC) shear rate or strain can be assessed. Structural changes under very low shear (like in the case of storage, gravity settling, compression moulding etc) or very high shear (pumping, extrusion, mixing, injection moulding etc) are possible using the advanced equipment and sensors available at the laboratory of Rheology Solutions. These measurements may be obtained as a function of temperature, solids density, or to monitor the effects of changes in additive/ingredient species or concentration.
With this information the scientist or engineer may change the process, or design new unit operations or products to maximise the potential benefits to be obtained from the physical properties of the processed fluid.
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