The Cool Future of UV Curable Silicone Extrusion

Reduced set-up time. It has been well established that set-up operations account for a significant portion of the manufacturing costs associated with producing medical tubing. During the setup, technicians choose and assemble the appropriate die and mandrel combination to produce the required geometry. Short extrusion test runs are then performed so that tubing dimensions can be measured using optical comparators or other advanced vision systems.

The set-up process is greatly slowed by the fact that the tubing must be allowed to cool prior to inspection. The cooling period assures worker safety and allows the tubing to reach dimensional equilibrium. After cooling, the tubing is cut and fixtured for dimensional analysis or performance testing. Based on this analysis, adjustments are made to the tooling and barrel speed so that key parameters of tubing geometry will meet specifications. These set-up adjustments are repeated until the tubing geometry is optimized within all specifications. Unlike the thermal HAV vulcanization, tubing exiting the UV light chamber is close to room temperature. This greatly reduces the feedback loop needed for technicians to receive vital dimensional analysis and perform the necessary adjustments.

Lower energy consumption. Most extrudable silicones require significant heat for vulcanization — which, in turn, requires that HAVs be fitted with powerful resistance style heaters, which consume considerable energy. Energy costs required for the UV curing process are estimated to be 30% of those for a thermal curing process.

Future Potential Applications for Silicones in Drug Delivery

Compared to thermal extrusion processes, the UV process has demonstrated its potential to reduce manufacturing costs. However, just as importantly, SSF believes the low-temperature UV extrusion process will dramatically expand the utility of silicones in the drug delivery sector. Revenue from the drug-device combination product market is expanding at over 14% per year, outpacing growth of both the medical device and pharmaceutical industries. Until now, the number of active pharmaceutical ingredients (API) that could be delivered from a silicone matrix has been limited due to the temperature sensitivity of most drugs and the high heat requirement of the silicone vulcanization process. SSF feels that low-temperature UV vulcanization will greatly increase the candidate pool of API that many OEMs may consider for drug delivery through a silicone matrix.

On May 18, 2011, Momentive Performance Materials and Specialty Silicone Fabricators announced a collaborative initiative to pursue opportunities regarding the development of UV cure products that may be appropriate for consideration in silicone-based drug-device technology. It is expected that these platforms, once fully developed, could provide strategic advantages to both the pharmaceutical and medical device sector.

This article was written by Mel Toub and Stacey Guilford of Momentive Performance Materials Inc., Albany, NY; and Mark Paulsen, Steve Garelli, and Frank East of Specialty Silicone Fabricators, Paso Robles, CA. For more information about Momentive, visit http://info.hotims.com/34456-162; and for more information about SSF, visit http://info.hotims.com/34456-194.

References

• Addisil is a trademark of Momentive Performance Materials Inc.
• Geo-Trans is a registered trademark of Specialty Silicone Fabricators and is subject matter in US patents 5,511,965 and 5,549,579.