The latest generation of fluorosilicones and radical-cure silicone adhesive technology offer greater flexibility and other benefits to automotive designers, as well as manufacturers of components made from rubber compounds, according to the Dow Corning Corporation.
“Dow Corning anticipates a growing need for fluorosilicones. And, our two newest Silastic® F-LSRs can help OEMs improve component performance and reliability in key systems for fuel economy and emissions control, as well as help fabricators increase efficiency, reduce material waste and possibly gain significant process savings,” said Gabe Knee, Automotive Market Leader for Dow Corning in a media statement.
In 2014 the company introduced two new Silastic® brand F-LSRs, which combine the fuel, oil and solvent resistance of fluorosilicone rubber (FSR) with the processing benefits of liquid silicone rubber (LSR). “The Silastic F-LSR technology offers fabricators substantial process gains for producing newer seals, gaskets, connectors, flexible diaphragms, membranes and valves using standard injection molding equipment,” said Knee.
The first fluorosilicone rubber compounds were developed by Dow Corning more than 50 years ago for aerospace seals and gaskets that required high fuel and oil resistance. The value of FSR technology for automotive applications was quickly recognised. Dow Corning’s other automotive products include its Molykote® brand of specialty lubricants that are specifically formulated for brake-system applications.
A wide selection of Molykote® brand lubricants is available to meet specific performance requirements in brake system lubrication applications. Application-matched lubricant choices are available for pedal system pivots and bearings, hydraulic components, such as air compressors and master cylinders, brake booster and actuator diaphragms, seals and pistons, disc brake components, from needle bearings to caliper assembly parts, mechanical or electrical parking brakes and brake-by-wire actuators.
They enhance braking performance and reliability by resisting water washout, dust and dirt buildup, oxidation, and searing heat and numbing cold. Safety is improved by helping to maintain system seals without causing common elastomers, such as EPDM and neoprene, to soften, swell or lose sealing integrity.
Automotive Industries (AI) asked Craig Gross, Senior AETS Specialist, Silicone Elastomers what are some of the recent breakthroughs Dow Corning has made in automotive-targeted, silicon elastomers.
Gross: Dow Corning has developed two new and innovative fluorosilicone rubber (FSR) technologies. The first technology delivers improved heat resistance for FSRs and expands the upper temperature range in which FSR can be used. Previously limited in use to applications up to 200°C, we developed FSR technology to deliver good retention of physical properties when exposed to temperatures of 220°C with excursions up to 240°C. The second technology recently developed improves the compression set resistance of fluorosilicone elastomers and achieved single-digit compression set values when tested for 22 hours at 177°C. Both of these new technologies can be incorporated across a wide durometer range.
AI: How do the products helped automotive designers and manufacturers?
Gross: These new fluorosilicone technologies expand the toolbox of automotive designers by providing additional options for material selection and performance. As under-the-hood temperatures continue to increase, fluorosilicone elastomers are being asked to deliver performance in temperatures not previously required or encountered for such applications. This new high temperature FSR technology can now meet many of these evolving temperature requirements.
An improved compression set resistance fluorosilicone technology now enables better sealing and durability for applications requiring fuel and automotive fluid resistance. The lower compression set of a material can result in higher sealing force retention over the life of the application, ultimately resulting in better durability.
AI: What are some of the future trends in silicone elastomers that you think will majorly impact the auto industry?
Gross: The automotive market will continue to require higher temperatures in under-the-hood applications. Silicone and fluorosilicone elastomers are well suited to address this ongoing need, and the developments focused on improved temperature resistance will open up opportunities for broader applications and those requiring higher temperatures compared to today. Acid gas resistance is also becoming a critical need as more exhaust gas recirculation is being used to improve emissions and fuel economy.
Advances in FSR technology are providing improved resistance to these acids and providing automotive designers an option when designing seals for EGR systems.
Automotive Industries then asked Irina Bolsacova, Global Marketing Leader, Automotive Elastomers, what the response has been from OEMs to the release of Silastic® fluorosilicone rubber compounds.
Bolsacova: Our latest fluorosilicone elastomer technology created excitement with automotive customers. The combination of processing flexibility typical for silicone elastomers coupled with extended temperature resistance enables customers to extend their design options and improve total cost of ownership (TCO) helping better address auto industry challenges for weight reduction and fuel efficiency
AI: What are some of the reasons for their popularity?
Bolsacova: Extended temperature stability which is comparable with incumbent fluorocarbon solutions on the market, and advanced flexibility of processing and design with silicones
AI: What are some of the new products that are likely to be launched in the near future that will be aimed at the automotive industry?
Bolsacova: Dow Corning is committed to be an innovation partner for the automotive industry. We are working on expanding temperature and chemical stability of our elastomers, enabling customers to answer even more challenging regulation requirements for fuel consumption and support automotive customers in developing vehicles that are more energy efficient, cleaner, safer and offer higher comfort.
Kate Johnson, Electronics Technical Specialist for Dow Corning, was asked to expand on her presentation to the SAE World Congress & Exhibition 2015.
Johnson: The presentation was an introduction to a new technology platform. The target audience was designers and the discussion involved the design enablement capability of this new technology. These new adhesives will let designers significantly expand their toolbox and broaden the material set beyond the historical boundaries enabling them to optimize in substrate cost and enhance design selections. AI: Please tell us more about the technology.
Johnson: The new chemistry platform is called Thermal Radical Cure™. We want to be clear that this is a technology platform, not just a new product. In time there will likely be numerous products that are built on this new chemistry system that are designed and developed specifically for multiple markets. There are two key performance differentiators in this new technology. First is adhesion to a broader set of substrates than has been available with traditional chemistry compounds. These new adhesives will often adhere to polymer systems with complex additive packages – typically without any pre-treatments. This expands the choices designers have in substrate selection and can often eliminate one or more process steps. Additionally the mechanism of adhesion has very fast kinetics, even at low temperature, enabling faster process times at lower temperatures and in smaller ovens than traditional one part silicon addition cure chemistry sets. The technology has benefits that appeal to both designers and process/manufacturing engineers enabling creativity and cost saving potentials to both.
AI: How do you see the new product impacting the automotive industry?
Johnson: It offers flexibility in design as well as cost and process savings. Furthermore, this technology aligns to key industry trends such as light-weighting by adhering to alternate structural materials that can be challenging for traditional adhesives. The ability to adhere to a very broad set of substrates and provide durable structural adhesion to dissimilar substrates supports industry drivers in the transition of metal to plastic