The plastics industry is a major player in the European economy, and has an important role to play in the ecological transition into an energy-efficient and waste-free society. In addition to a higher recycling rate, a better design of plastic products is critical to reach Europe’s sustainable development goals as well as to stay competitive.

The present project opens a new path towards improved product quality and reduced raw material waste in the plastic extrusion industry. Presently only simple geometries like pipes and sheets can be measured in a safe way with inline sensors. More complex geometries are either tested in a destructive way, which results in long feedback times for process control, or with unsafe radiations. Here, we propose a new sensing technology for inline quality control of extrusion profiles based on Computer Tomography (CT) using Terahertz (THz).

This system will allow to determine the full extrusion profile in a non-destructive way. This would be a big step forward compared to the state of the art of extrusion profile testing in general and THz-CT in particular, considering that the few examples in the literature so far focus on simpler sample geometries, or do not exhibit the necessary resolution or speed for this type of application. The advantages for the plastics industry are that, compared to other solutions currently in place, THz radiation is safe and allows for non-destructive and non-contact assessment of structural and physical characterisation of entire profiles.

The first objective of the present project is to lay the foundations for a future inline instrument by finding the best THz-CT approach to analyse the geometry of typical extrusion profiles using a laboratory setup, including developing reliable and fast algorithms for the reconstruction. The second objective is to optimise the resolution and bring it down to 0.3 mm, so as to match typical extrusion profile dimensions. Based on the results of this project and the current development on the THz technology market, a THz-CT apparatus suitable for inline quality control will be conceived in a follow-up project.