Medicaldevice manufacturers have traditionally used thermoset silicone rubber to moldpump valve inserts. However, these inserts are often hampered by inefficientdesigns and a manufacturing process that is time-consuming and costly, as itinvolves several labor-intensive assembly steps.

Toaddress these issues, PolyOne developed the GLS thermoplastic elastomer (TPE)created in a two-shot molding process to eliminate assembly operations.

Thecustom-formulated grades PolyOne creates are based on Dynalloy OBC and VersaflexTPEs to facilitate two-shot molding. PolyOne conducts compatibility testing toconfirm that the new grades will bond chemically with the rigid engineering thermoplasticsubstrate required in these applications.

Thecustom grades are formulated with multi-functional capabilities, so that theycan replace several different hardness grades of silicone rubber. The TPEmaterials also provide better tension set, improved compression and enhancedpermeability compared to silicone rubber. In addition, the new TPE grades boastlower extractables because, unlike thermoset silicones, they require no cross-linking.These materials also offer quick set-up on standard two-shot molding equipment alongwith faster cycle times for higher productivity.

Eliminatinga multi-component process cuts the need for assembly operations, offering asmuch as $50,000 in savings to medical device OEMs annually. This savings isachieved because several assembly steps are removed because the TPE customformulations deliver multi-functional capabilities.

Secondly,the lower specific gravity of the TPEs cuts overall part weight by 15 to 20percent and reduces associated freight costs for further savings.

Inaddition, these custom materials result in major scrap rate reductions, providingsavings of up to $40,000 annually. The regrind also offers recycling benefitsthat are not available with thermoset silicone rubber.

Intotal, the use of custom TPE pump valve inserts can create more than $100,000in operational savings by reducing manufacturers' costs for assembly, freightand scrap.

Joe Kutka, is technology launch manager, PolyOne GLS ThermoplasticElastomers.