Effects of moulding and environmental conditions on the mechanical and surface properties of injection moulded santoprene rubber

This project was carried out in co-operation with the company Sonion. Sonion specializes in manufacturing miniature components mainly for use in hearing aids or medical instruments. Recently Sonion has developed a hearing that calls for the need of a miniature sealing ring to protect the electronics inside from environmental hazards.

The sealing ring is injection moulded in Santoprene-a thermoplastic vulcanizate consisting of Polypropelene and highly vulcanized EPDM rubber. The scope of the project was therefore to investigate the properties of Santoprene and make an immediate evaluation of whether Santoprene is appropriate for use under the conditions, to which it will be subjected being part of a hearing aid used on daily basis.

The conditions tested are: sweat, acid corrosion, extreme temperatures. An evaluation of the maximum load before breakage in relation to manufacturing conditions has also been performed.