Different facets of silicones
The next gen automotive will be governed by low weight, high strength materials and silicones fit the bill. More and more automotive manufacturers are exploring the opportunities that silicones have to offer and are increasingly replacing metal parts with silicones to make vehicles lighter, faster yet sturdier for the future.
The dynamics of the automotive industry is being driven by rising environmental concerns which demands for lightweight, fuel-efficient vehicles. Several global regulations are also becoming more stringent by the day to keep environment in check. Corporate Average Fuel Economy (CAFE) in the US requires manufacturers to improve the cars’ miles per gallon (MPG) from 25 MPG to 35.5 MPG. The European automotive industry is under pressure to achieve fuel economy requirement of 5 L/100 km and the trend among OEMs is to miniaturise their products or use lighter materials to bring down the overall weight of the automobiles. In this industry, every single ounce counts!!
With this, the automotive manufacturers are turning towards silicone which is not just lighter and sturdier than other materials but also has superior properties like high resistance to heat, chemicals, ultraviolet rays and corrosion.
While silicone is becoming an important replacement material in various sealing, gasketing, hosing and electrical & electronic applications in the automotive market, manufacturers are looking for more ways to incorporate this light weight material in other automotive parts.
“Silicones are increasingly being used in several sectors such as the automotive, health-care, lighting and electronics industries. There are two reasons for this: on the one hand, material requirements are rising steadily. On the other, standard materials are reaching their limits. In order to develop and produce innovative products, the industry needs high-performance materials such as silicones,” said Robert Gnann, head of Wacker's silicones business division. “Due to their unique physical and chemical properties which can be combined in several ways and their excellent process ability, silicones have become indispensable in many industries.”
According to a Frost & Sullivan report, the silicone market earned revenues of $2.59 billion in 2015 and estimates to reach $4.06 billion by 2021. Driving on the robust automotive production growth in China and India, Asia-Pacific presents a huge growth opportunity for silicone market in this region. However, the sluggish automotive growth in Europe and North America will also register limited growth of silicone market in the automotive sectors of this region. According to F&S report, while Europe’s automotive production CAGR is expected to increase from 1.7 percent in 2014 to 2.7 percent in 2021, North America is expected to register a CAGR of only 1.2 percent between 2011 to 2021.
While silicone is registering exponential usage in electronics, construction and healthcare sectors, the automotive industry has embraced silicone for its dynamic properties which are changing the science of automotive manufacturing altogether.
The need for lower carbon emissions and lightweight has made silicones right material to adhere the stringent regulations. Silicone, in various forms ie. elastomers, fluids, resins, gels, etc is being tried out extensively to be made into advantageous alternatives of various automotive parts. There has been a rising use of silicones in under-the-hood applications like replacement of metal bolts, rivets, etc.
Smithers Rapra Market Intelligence points out that the global market for silicone elastomers, which was about 391 thousand tonnes in 2015, is expected to increase at a CAGR of 6.1 percent, to 558 thousand tonnes in 2021.
Electronic applications in automotive are continuously becoming complex to meet the demand for increased performance and reliability. These applications have to perform under harsh environmental conditions and high temperatures under the bonnet. This induces stress and increases the possibilities of component failure. Mechanical stress from vibrations in engine and road conditions, chemical and oil attack in and around the engine compartment, water and humidity are some of the other constant threats. Hence, protection of electronic application is a growing concern.
Silicone gels in the form of a soft cured elastomer help provide extensive environmental protection and also absorb potentially damaging vibrations.
“Elastomers are often applied to seal or to protect something. So any permeation of aggressive chemical compounds - including water and oxygen - can’t be blocked. On the other hand ventilation is possible with silicone in contrast to other elastomers,” said Dr Dieter Wrobel, a corporate fellow at Momentive.
Hybrid silicone gels are also being used to incorporate a degree of thermal conductivity and dissipate heat from the component to a suitable heat sink. The other advantages of silicone gel is that it can be removed without damaging the PCB or electronics, is useful for reworking very expensive components and low viscosities, is simple to use mix ratios, and ensures fast, efficient and error free production.
These gels are widely being used for encapsulating and sealing sensors and electronic control units and LED encapsulation. Silicone Adhesive Sealants are also widely being used for sealing applications under the bonnet where the temperature is high. These sealants can effectively withstand high temperatures and be used to seal fuel flow control units, control vibration of large electronic components, dissipate heat and seal various electronic enclosures.
“Hard-soft composites are getting more and more important. The bonding of silicone towards metals or other high-temperature thermoplasts is quite challenging. As silicones are always used under extreme conditions that often bring the material to its limits, it is essential to understand both the physics and the chemistry of silicones to be able to further improve their already outstanding properties,” said Dr Martin Bortenschlager, technical manager, rubber solutions, Wacker Chemie.
LED lighting is a significant part of any automotive. Optically clear silicone gels are extensively being used in manufacturing LED modules to offer protection and improve light output and efficiency. Dow Corning recently launched Dow Corning 40-001 additive, which is used in LED lighting for consumer electronics, automotive headlamp lenses and exterior lighting. This advanced liquid siloxane additive has improved flame retardancy (FR) while retaining high clarity with minimal haze, and has no impact on tensile strength or modulus.
Silicone rubber: With increased performance of automobiles come increasing amount of heat generation. Silicone rubber provides strength, resistance and durability needed by automotive applications today. Silicone rubber can withstand high temperature ranging from 230°C to -60°C extending the life of automotive parts. It has also proved to have resistance to rain, wind, salt, abrasion, ultraviolet radiation and chemicals. All these properties have made silicone the material of choice among growing number of automotive manufacturers.
Silicone rubber is extensively being used in a wide range of applications like airbags, engine gaskets, headlamps, ignition cables, ht cables, grommets, radiator seals, performance hoses, vibration dampening, shock absorbers, spark plug boots, ventilation flaps etc.
Wacker introduced a new liquid silicone rubber, Elastosil® LR 3016/65, designed especially for automotive engineering use. It exhibits enhanced media resistance and can retain important material properties even when in contact with hot motor oil for long periods of time.
The new silicone grade can be made into O-rings and other seals quickly and easily by injection moulding. Silicone Pastes: can be used as lubricants and sealing aids for sealing parts and connections that can be disassembled. They have a noncuring, pasty consistency which is largely unaffected by temperature, permitting use over a broad temperature range.
These pastes are water resistant, water repellent, oxidation resistant, hence offering long-term resistance to atmospheric influences by forming a protective layer. They are odourless, low toxicity and radiation resistant. They also exhibit good lubricity and have longer shelf life. The potential of silicone is immense and researches across the world are still exploring the possibilities that silicone has to offer to make next generation automobiles lighter, faster, eco-efficient and safer.
