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Silicone rubber has superior fatigue resistance under extreme temperatures
NEWS Major automotive applications for the new Viton FKM pre-compound include sensor hoses for positive crankcase ventilation, and for exhaust gas sensors and diesel particulate filters, air intake manifold gaskets, quick connector O-rings and seals, intercooler and exhaust gas recirculation cooler seals, and rubber sleeves for plastic air-ducts. New Vamac Ultra HT-OR AEM, also introduced at K 2013, is an example of recent collaboration with hose manufacturers and OEMs to provide a clear improvement in resistance to hot oil, acid blow-by and recirculated exhaust gases in high-temperature turbocharger hose applications. ‘As the automotive industry strives to reduce CO2 emissions, modern engine technologies create more severe environments for seals and hoses,’ explained Patrick Cazuc, Automotive Director, Europe, Middle East, Africa, DuPont Performance Polymers. ‘We have developed Vamac Ultra HT–OR and Vamac Ultra LS to respond to tougher requirements for higher standards of temperature and chemical resistance needed in the latest engines. These products push the performance envelope of the Vamac AEM elastomer portfolio still further, and complement an already versatile set of offerings.’ ‘Acid-resistant Viton FKM will provide the industry with an economic and much needed bisphenol alternative to peroxide-cured FKM, offering protection against the acid gases and condensates generated by modern engines.’ Contact: DuPont Performance Polymers Sa, 2 chemin du Pavillon, CH-1218 Le Grand-Saconnex, Geneva, Switzerland. Tel: +41 22 717 4042, Web: www.dupontelastomers.com
Silicone rubber has superior fatigue resistance under extreme temperatures
T
o help meet key challenges associated with fabricating more durable automotive components using engineered elastomers, US-based Dow Corning Corp now offers a high-consistency silicone rubber (HCR) that provides superior fatigue resistance under extremely high or low temperatures. Potential applications for Silastic HCM 60-1225-GRAY silicone rubber include constant velocity joint (CVJ) boots, steeringsystem boots, exhaust hangers, engine mounts and component mounts for NVH control.
‘Especially developed to outperform other elastomers and thermoplastic options in demanding applications, fatigue-resistant Silastic HCM 60-1225-GRAY can deliver excellent performance properties, along with processing efficiency,’ said Kevin King, the firm’s product developer for Silastic brand silicone rubber elastomers. ‘Significant improvements are achieved in extending fatigue life across a wide service temperature range to meet design specifications for higher operating temperatures and a more compact, lightweight design.’ For enhanced component durability the rubber exhibits high extensional and flexural fatigue life, high tensile and tear strength, high elongation, good heat-ageing stability with low compression set, and stable physical properties for reliable performance at temperatures of -40 to 200°C (-40 to 392°F). For process efficiency, it is a fully formulated, ready-to-use silicone rubber compound with a peroxide-curing system. It offers process stability, fast cure times at elevated temperatures, excellent mould release characteristics and higher throughput without requiring post-curing. Custom compounding is available for special properties or colours, says the firm. ‘For highly durable, heat-resistant boots for constant-velocity joints, new Silastic HCM 60-1225-GRAY can help eliminate the need for heat shields on drive-line inboard joints,’ explained Gabriel Knee, Account Manager, Dow Corning Automotive. ‘For other fabricated parts this new fatigueresistant HCR can withstand higher engine and exhaust operating temperatures, resist tearing and cracking with repeated stretching or flexing, and provide long-lasting vibration damping and isolation for NVH control.’ Contact: Dow Corning Corp, PO Box 994, Midland, MI 48686-0994, USA. Tel: +1 989 496 7881, Fax: +1 989 496 6731, Web: www.dowcorning.com, Web: www.xiameter.com
Saint-Gobain materials pass flammability tests
S
aint-Gobain Performance Plastics’ Seals Group reports that its Meldin 7001 (unfilled polyimide) thermoset material has passed the UL94 flammability tests. In addition, the firm’s Rulon J fluoropolymer material has been certified for mass transit applications, after performing according to ASTM flammability, smoke and toxicity (FST) standards.
BOB’S BIT
I
t occurs to me whilst looking through the news for this month just how much contribution sealing technology makes to many of the engineering efforts to reduce energy consumption, and with it CO2 emissions, plus industrial fugitive emissions in general. It is something that many of us involved in the industry are aware of, but when several news articles highlight individual contributions it helps to emphasise just how much contribution sealing makes to progress in this area. It would be easy to make a rather glib statement that sealing technology advances make the engineering developments possible. In reality many of the engineering developments would still be made, but would probably involve considerably more involved engineering and cost, thus making them much less attractive to the OEM, and eventual user. It is perhaps worth summarising some of the contributions that are in the news this month. Several contributions are mentioned on the front page. A lighter weight silicone sounds rather marginal, but there are some quite large seals on an airframe, and they are fairly numerous. Low-friction shaft seals were introduced to the automotive industry some time ago, so it is good to see them being usefully employed in aerospace. Finding seal materials that can keep pace with the requirements of increasing fluid temperatures, and new fluid and additive types, is also an important area. This theme is mentioned on the front page and continued inside with the details of developments in AEM and FKM materials. In the automotive world, the quest for higher efficiency and reduced emissions has led to increased fluid temperatures, the use of synthetic lubricants with aggressive additive packages, and requirements to work with high-temperature recirculation gases. Many of these demands have tested the limits of elastomers, leading to material developments such as those included this month. Solutions avoiding elastomers are, of course, possible, but would they be financially acceptable? An interesting example of lateral thinking is demonstrated by the automatically opening seal to allow controlled ventilation – a real problem as buildings become more energy efficient, but often very stuffy. To look at progress in combating industrial fugitive emissions the report of API testing on valve packing provides the sort of results that I still find quite amazing. This is enormous progress from the days of ‘so long as we cannot see leakage pouring out, it is OK’. Bob Flitney 3
November 2013
Sealing Technology
Silicone rubber has superior fatigue resistance under extreme temperatures
T
o help meet key challenges associated with fabricating more durable automotive components using engineered elastomers, US-based Dow Corning Corp now offers a high-consistency silicone rubber (HCR) that provides superior fatigue resistance under extremely high or low temperatures. Potential applications for Silastic HCM 60-1225-GRAY silicone rubber include constant velocity joint (CVJ) boots, steeringsystem boots, exhaust hangers, engine mounts and component mounts for NVH control.
‘Especially developed to outperform other elastomers and thermoplastic options in demanding applications, fatigue-resistant Silastic HCM 60-1225-GRAY can deliver excellent performance properties, along with processing efficiency,’ said Kevin King, the firm’s product developer for Silastic brand silicone rubber elastomers. ‘Significant improvements are achieved in extending fatigue life across a wide service temperature range to meet design specifications for higher operating temperatures and a more compact, lightweight design.’ For enhanced component durability the rubber exhibits high extensional and flexural fatigue life, high tensile and tear strength, high elongation, good heat-ageing stability with low compression set, and stable physical properties for reliable performance at temperatures of -40 to 200°C (-40 to 392°F). For process efficiency, it is a fully formulated, ready-to-use silicone rubber compound with a peroxide-curing system. It offers process stability, fast cure times at elevated temperatures, excellent mould release characteristics and higher throughput without requiring post-curing. Custom compounding is available for special properties or colours, says the firm. ‘For highly durable, heat-resistant boots for constant-velocity joints, new Silastic HCM 60-1225-GRAY can help eliminate the need for heat shields on drive-line inboard joints,’ explained Gabriel Knee, Account Manager, Dow Corning Automotive. ‘For other fabricated parts this new fatigueresistant HCR can withstand higher engine and exhaust operating temperatures, resist tearing and cracking with repeated stretching or flexing, and provide long-lasting vibration damping and isolation for NVH control.’ Contact: Dow Corning Corp, PO Box 994, Midland, MI 48686-0994, USA. Tel: +1 989 496 7881, Fax: +1 989 496 6731, Web: www.dowcorning.com, Web: www.xiameter.com
Saint-Gobain materials pass flammability tests
S
aint-Gobain Performance Plastics’ Seals Group reports that its Meldin 7001 (unfilled polyimide) thermoset material has passed the UL94 flammability tests. In addition, the firm’s Rulon J fluoropolymer material has been certified for mass transit applications, after performing according to ASTM flammability, smoke and toxicity (FST) standards.
BOB’S BIT
I
t occurs to me whilst looking through the news for this month just how much contribution sealing technology makes to many of the engineering efforts to reduce energy consumption, and with it CO2 emissions, plus industrial fugitive emissions in general. It is something that many of us involved in the industry are aware of, but when several news articles highlight individual contributions it helps to emphasise just how much contribution sealing makes to progress in this area. It would be easy to make a rather glib statement that sealing technology advances make the engineering developments possible. In reality many of the engineering developments would still be made, but would probably involve considerably more involved engineering and cost, thus making them much less attractive to the OEM, and eventual user. It is perhaps worth summarising some of the contributions that are in the news this month. Several contributions are mentioned on the front page. A lighter weight silicone sounds rather marginal, but there are some quite large seals on an airframe, and they are fairly numerous. Low-friction shaft seals were introduced to the automotive industry some time ago, so it is good to see them being usefully employed in aerospace. Finding seal materials that can keep pace with the requirements of increasing fluid temperatures, and new fluid and additive types, is also an important area. This theme is mentioned on the front page and continued inside with the details of developments in AEM and FKM materials. In the automotive world, the quest for higher efficiency and reduced emissions has led to increased fluid temperatures, the use of synthetic lubricants with aggressive additive packages, and requirements to work with high-temperature recirculation gases. Many of these demands have tested the limits of elastomers, leading to material developments such as those included this month. Solutions avoiding elastomers are, of course, possible, but would they be financially acceptable? An interesting example of lateral thinking is demonstrated by the automatically opening seal to allow controlled ventilation – a real problem as buildings become more energy efficient, but often very stuffy. To look at progress in combating industrial fugitive emissions the report of API testing on valve packing provides the sort of results that I still find quite amazing. This is enormous progress from the days of ‘so long as we cannot see leakage pouring out, it is OK’. Bob Flitney 3
November 2013
Sealing Technology