Development of small moulded silicone tubing for the medical sector

The Institute of Plastics Processing (IKV) in Industry and the Skilled Crafts at RWTH Aachen University is investigating the development of a process for the production of micro-sized hollow articles made of silicone with integrated functional elements.

In the medical and pharmaceutical segments, media-carrying capillary moulded tubing is used for a variety of applications in diagnostics and in the administration of medication. Liquid silicone rubbers (LSR) are especially suitable for use in medical technology because they open up a wide field of application thanks to their biocompatibility, sterilisability, and mechanical and chemical resistance.

In this new approach, IKV is combining the gas and projectile injection technology (GIT and PIT) with the micro-injection moulding of silicone rubbers. The use of GIT/PIT should allow such hollow articles to be produced by a free-falling method in a single-step process. Apart from that, the IKV research team expects the development of the micro-GIT/PIT technology to create a more efficient process with the possibility of producing more complex geometries and additional integrated functional elements.

To investigate the processing of LSR with the projectile injection technology in the micrometer range (LSR-µPIT), the research team built a variable test mould for an ultra-small injection moulding machine. Through the use of various inserts, the variable mould technology ensures that outer diameters of 1 - 4 mm can be tested. The injector technology integrated into the standard mould unit with a closable and switchable injector also allows the use of both GIT and PIT with projectile diameters of 0.5 - 3mm in one system complex of the mould.

In this project, which is funded as Joint Industrial Research (IGF) via the Confederation of Industrial Research Associations (AiF) by the German Federal Ministry for Economic Affairs and Energy, the future work will look at the influence of various process parameters, process variations of the fluid injection technology and different projectile materials with regard to their suitability for the micro-injection moulding of silicone. The new approach may be an alternative to the production of highly integrated hollow articles that are nowadays usually made of thermoplastics. Although thermoplastics are, because of their simple functional integration by welding and the widespread knowledge of the process, broadly used on the global market, they offer fewer advantages in medical applications.