Process Rheology:

Rheometry is the most widely used in-process measurement in polymer processing. This is because of the accessibility of the technique and because rheology is a sensitive indicator of material consistency. Process rheometry can incorporate simple MFI-type measurements or more sophisticated characterisations over a range of processing rates. In-process rheological measurements have been used to monitor batch to batch variation, additive levels, process stability and recycled polymers. Such measurements are useful not only for production monitoring but also to provide accurate process data for modelling packages. Although the bulk of process rheometry is related to extrusion, useful data can be extracted from the injection moulding process by taking an integral over part of the injection pressure curve. This simple measurement reflects melt consistency during filling and has been shown to be a sensitive indicator of part quality and stability. In-process rheometry is the closest technique to broader industrial usage (sometimes in a very limited form).

In Task 4 we will apply in-process rheometry to speicific areas of polymer processing:

1. Supercritical fluid extrusion - a novel process which has the potential to reduce energy, lower viscosity and aid mixing. The exact mechanism of interaction between supercritical fluid and melt is unclear, therefore it is important to measure rheology to gain a better understanding.
2. Processing of recycled polymers is demanding due to the varying nature of feedstock composition.
3. Develop simple in-process techniques such as a bleed-flow rheometer and
4. Develop injection moulding process integrals to encourage industrial take-up. This type of development builds upon previous NMS project recommendations to standardise in-process measurements in a similar manner to off-line techniques such as MFI and capillary rheometry.