The project investigated the feasibility of a fully integrated polymer processing chain that eliminates the conventional intermediate granulation step. By combining a double‑screw extruder with a melt pump, the melt can be directed straight into a tube, thereby removing the need for cooling, granulation and a second extrusion or injection step. The study focused on medical‑grade polymers such as PVC, TPU and TPE, and on the production of demonstrator components for infusion devices, including tubing, drop‑chamber bases and syringe plungers.

A key technical achievement was the design and testing of three novel screw geometries – B31, E35 and E67 – that dramatically improved the dispersion of calcite masterbatch particles. Micro‑computed tomography revealed that the largest calcite agglomerate in the standard screw had a volume of 0.24 mm³, whereas the new geometries reduced the maximum particle volume to 0.025 mm³, 0.015 mm³ and 0.005 mm³, respectively – a reduction of 10‑ to 50‑fold. When the material was pre‑compounded in a double‑screw extruder, the maximum particle volume dropped to 0.0005 mm³, confirming the superior mixing performance of the new designs. The masterbatch composition (56.1 % SEBS, 4.0 % PP‑R, 3 % colour, 36.9 % calcite) was maintained at 30 % calcite in all test parts, and the resulting syringe plungers were delivered to B. Braun for functional testing.

Inline quality control was enabled by a terahertz (THz) melt‑characterisation system developed by Hübner. The THz probe, integrated into the melt channel, provided real‑time data on melt homogeneity and viscosity, allowing the process to be monitored without interrupting production. Correlation studies between THz spectra and micro‑tomography data established a predictive model for material quality, which was incorporated into the overall quality‑assurance concept.

The project also introduced a direct injection‑moulding variant that couples a conventional injection machine with a stop‑start single‑screw extruder. This configuration eliminates the need for a melt reservoir and refill valves, simplifying the process and reducing equipment costs. Demonstrator runs produced complex components such as the drop‑chamber base, and the resulting parts met the mechanical and dimensional specifications required for medical devices.

Collaboration involved several industry partners and research institutes. Pape GmbH supplied expertise in screw design and evaluated the new geometries. Zeppelin GmbH contributed experience in PVC and TPE processing and integrated the melt‑pump concept. Hübner GmbH provided the THz spectroscopy system and inline monitoring. The Institute for Materials Technology performed material and process analysis, including micro‑tomography and mechanical testing. KraussMaffei Technologies developed the direct injection‑moulding machine configuration, while B. Braun supplied the final product testing. The project ran from 2017 to 2018 and was funded by the German Federal Ministry of Education and Research under the National Competence Center for Biomedical Engineering (NKBF).

This integrated approach demonstrates that direct compound‑to‑product processing is feasible for medical‑grade polymers, offering significant cost savings, reduced cycle times and improved material quality. The findings provide a solid foundation for further research and industrial adoption of fully integrated polymer manufacturing lines.