Particle-filled silicones for EMI shielding and environmental sealing: Page 3 of 3

June 01, 2015 //By Dominic Testo, Specialty Silicone Products
Particle-filled silicones are elastomeric compounds that combine the advantages of silicone with the electrical properties of metals. An inert, synthetic rubber, silicone offers thermal stability over a wide temperature range and resists ozone and ultraviolet (UV) light.
Size dimensions and lead times

Fabricators understand the importance of size dimensions, especially with regard to production times and cost. For example, compression molded sheets can take a long time to produce. Sheets with different thicknesses require different tooling, which also adds to costs. To produce sheets that are longer than the standard 15- to 20-inches mold size, bonding or joining are necessary. When evaluating particle-filled conductive silicones then, gasket fabricators may choose continuous rolls instead of compression molded sheet stock.

SSP produces both sheets and rolls at its Ballston Spa, NY facility, but continuous rolls offer several advantages. First, since these rolls are produced and cured continuously, SSP can manufacture 1000 feet per day, the equivalent of 600 standard 15- x 20-inch sheets, with short lead times. Fabricators should consider the roll's thickness and width, however, and also ask themselves an important question: how can we supply the greatest number of high-quality gaskets with the least amount of waste?

Material thickness

Some fabricators believe that all particle-filled conductive silicones are too thick, especially because so many consumer products now feature thinner profiles. Today, "smart technologies" such as cell phones, computer monitors, and interfaces feature slim and attractive screens with EMI/RFI shielding. The same is true of kiosks at amusement parks and shopping malls, where cell phone traffic can interfere with electronic displays. Factory kiosks also emit RF waves, and production workers require protection from daily exposure.

To meet the thickness requirements of these and other applications, SSP supplies conductive silicones as thin as 0.009-inches. By contrast, other suppliers offer compounds that are, at a minimum, between 0.015- and 0.020-inches thick. At the same time, and as this technical article explains, SSP's metal-filled elastomers are softer, less brittle, more resistant to tearing, and more-cost effective than other particle-filled silicones. SSP's nickel-coated graphite silicones offer the performance levels of silver-coated products, and the availability of continuous rolls means that fabricators can order and receive the quantities they need.

Conclusion

Gasket fabricators need to know that it's possible to source specialty silicones that aren't too hard, too brittle, too expensive, take too long to produce, or are too thick. In addition to aerospace, medical, military, automotive and consumer electronics, applications for these metal-filled elastomers include unmanned aerial vehicles (UAVs), shielded rooms and enclosures, and heavy equipment with global positioning systems (GPS). Now that you know more about the characteristics of particle-filled silicones, feel free to educate your contacts and partners in these industries.

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