Introduction Thermosets refer to the set of materials formed by polymers joined by chemical bonds acquiring a highly cross-linked final structure. The highly cross-linked structure of thermoset materials is directly responsible for the high mechanical and physical resistance (stresses or loads, temperature…) of these materials compared to thermoplastics and elastomers. On the …
Globally, 165,000 tons of silicone products are used in the transportation sector annually, which includes automotive, marine, aviation, and aerospace industries. Silicone rubber, resin elastomers, sealants, lubricants, and plastic additives are used extensively in spacecraft, automotive, aviation, and marine vessels, due to their strength, adhesion, and durability. Silicones contribute immensely to the safety of modern vehicles, from enabling airbags in cars to preserving the cabin pressure in airplanes.
Due to the special properties of silicone, this material is increasingly relevant for the automotive industry, both for new and existing applications. Silicones are high-performance polymers that exhibit properties of both inorganic and organic compounds. Silicones have a multitude of characteristics including heat resistance, cold resistance, weatherability, water repellency, defoaming properties, adhesiveness, releasability and dielectric properties. Silicone products are used in numerous ways to improve safety and reliability, and to make automobiles smaller, lighter and more eco-friendly, for example the United States Environmental Protection Agency estimates that for every 10% reduction in vehicle weight, fuel economy improves by between 5-7%.
Silicones are critical to the evolution of automotive technology, and manufacturers are taking notice. The diagram shows a properties comparison between silicone and other rubbers:
Comparison between silicone and others rubbers
Silicones improve aerodynamics by reducing surface wind-drag and the related silanes reduce rolling resistance in tires, further improving fuel efficiency.
The excellent UV and ozone resistance guarantee a long-lasting use without large optical aging characteristics. In contrast to other elastomers, silicone can be colored in all possible color variants, and thus offers a variety of possible applications in the automotive sector in addition to its pleasant haptics.
In our cars we find massive amounts of silicones in the form of heat-resistant engine seals, rubber hoses, electronics and cable insulation. However, silicones are also present in smaller quantities as they streamline processes by acting as release agents for steering wheels, dashboards, bumpers and a variety of plastic body parts. Even the creation of motor blocks, gear boxes, alternators, water pumps and other mechanical parts require silicones in the production process.
Silicone products commonly used in automobiles
Global Automotive Silicone Market is segmented by Application (Electrical Systems, Engines, Suspension Systems, Interior & Exterior, Others), by Type (Fluids, Resins, Gels, Elastomers, Others), and by Region (North America, Latin America, Europe, Asia Pacific, Middle East, and Africa).
By application, the Automotive Silicone market is segmented into electrical systems, engines, suspension systems, interior & exterior and others.
By geography, Automotive Silicone Market is segmented into North America, Asia-Pacific (APAC), Europe, South America, and the Middle East and Africa (MEA).
Silicone Fluids and Secondary Products for Automotive Applications
In recent years, automakers have taken efforts to make safer vehicles that are more comfortable and eco-friendly by adding car navigation systems, sensors and other features, while making vehicles lighter and more fuel-efficient. In this article, we Will discuss some of the places where silicone fluids and their secondary products (emulsions, oil blends) are used.
Automotive applications of silicone fluids and their secondary products
1. In-vehicle materials
- Sensor fill materials, damper materials
- Power transmission components
- Modifier for synthetic leather seat materials
- Weather strip coating agent
- Modifier for tires and rubbers
- Plastic & rubber modifiers
- Automotive chemicals, other applications
- Glass water repellents
- Car waxes and car wash detergents
- Tire & hose mold release agents, aluminum die-casting release agents
Automobiles are complex machines manufactured using advanced plastics and fabrics, and sophisticated mechanical, electric and electronic components. These parts have to last ten years or more. Without question, specially designed silicones will continue to be used in places with unique requirements.
Silicone Elastomers for Automotive Applications
As automobiles have become higher performance products, the use of electronic components has also increased. In some models today there are over 70 Electronic Control Units (ECU); silicone elastomers are used as sealing materials, adhesives and potting agents for these ECUs. Silicone elastomers provide exceptional durability and stable performance over a wide temperatura range.
In this section, we will discuss products designed for the protection of automotive components, including conformal coatings, potting materials and sealing materials, plus products designed to prevent sulfurization, which are attracting interest throughout the industry today.
Conformal coatings are dielectric materials applied to electric and electronic components to protect from moisture, condensation and dust.
Like conformal coatings, potting materials protect electronic components arranged on circuit boards from moisture, condensation and dust. Potting also helps reduce mechanical stress on electronic components caused by extreme temperatures and vibration. Regular silicone is called dimethyl silicone, and it features methyl groups attached to the side chains of the polymer. This type of silicone cannot be used in places where it will be directly exposed to gasolina or oils, but this weak point can be overcome by introducing trifluoropropyl groups into the side chains of the base polymer
Case Seal Materials
Case seal materials are used for waterproofing, to protect the electronic components inside ECUs from damage. These silicones will be exposed to the outdoor elements for years, and thus must provide high bonding durability
2.- Thermal Interface Materials
The transistors and ICs on circuit boards generate considerable heat. Silicones with high thermal conductivity are used to effectively radiate this heat. Because these silicones are applied directly to electric and electronic components, they have been designed with minimal amounts of low-molecular-weight siloxane, since this substance can cause faulty conduction at electrical contacts.
Automotive applications of silicone elastomers for automotive
3.-Fastening of parts
Many adhesives are used for the fastening of electronic parts and structural bonding. Some usage locations stay continually hot, while others are exposed to gasoline and other substances.
Thermal Interface Materials for Automotive Applications
At the same time that the automobile grows more and more sophisticated in performance, extremely rapid progress is also being made in the electronification of automotive parts. And as electronic devices become more compact and more tightly integrated, the volumes of heat generated from them have risen dramatically. In consequence, materials that provide outstanding thermal performance have come into strong demand. Automobiles are used in extreme environments ranging from deserts to arctic regions, and are exposed to vibrations. It is imperative, therefore, that thermal interface materials show durability against heat, cold and vibrations. As a material that can satisfy these requirements, silicone is ideal, and silicone thermal interface materials have proven to be highly reliable in automotive applications.
- A thermal interface material (shortened to TIM) is any material that is inserted between two components in order to enhance the thermal coupling between them. A common use is heat dissipation, in which the TIM is inserted between a heat-producing device (e.g. an integrated circuit) and a heat-dissipating device (e.g. a heat sink).
Principles of Thermal Interface Materials
- Thermal paste: Mostly used in the electronics industry, it provides a very thin bond line and therefore a very small thermal resistance. It has no mechanical strength (other than the surface tension of the paste and the resulting adhesive effect) and will need an external mechanical fixation mechanism. Because it does not cure, it is used only where the material can be contained or in thin application where the viscosity of the paste will allow it to stay in position during use.
- Thermal adhesive: As with the thermal paste, it provides a very thin bond line, but provides some additional mechanical strength to the bond after curing. Thermal glue allows thicker bond line than the thermal paste, as it cures.
- Thermal gap filler: It could be described as “curing thermal paste” or “non-adhesive thermal glue”. It provides thicker bond lines than the thermal paste as it cures while still allowing an easy disassembly thanks to limited adhesiveness.
- Thermally conductive pad: As opposed to previous TIM, a thermal pad does not come in liquid or paste form, but in a solid state (albeit often soft). Mostly made of silicone or silicone-like material, it has the advantage to be easy to apply. It provides thicker bond lines, but will usually need higher force to press the heat sink on the heat source so that the thermal pad conforms to the bonded surfaces.
- Thermal tape: It adheres to surface, requires no curing time and is easy to apply. It is essentially a thermal pad with adhesive properties.
- Phase-change materials (PCM): Naturally sticky materials, used in place of thermal pastes. Its application is similar to solid pads. After achieving a melting point of – 55-60 degrees, it changes to a half liquid status and fills all gaps between the heat source and the heat sink.
LIMS Materials for Automobiles
Silicone elastomers are used in various automotive parts because they are advantageous in terms of heat resistance, low-temperature characteristics and electrical characteristics. Meanwhile, thanks to technological innovations in molding machines, metal molds and materials, conventional millable or high consistency rubber is being replaced with liquid-type LIMS (Liquid Injection Molding System) materials, which facilitate rationalization of molding. The physical properties of cured substances obtained by LIMS molding are in no way inferior to those of millable rubber, and LIMS molding facilitates injection molding at low pressure. Moreover, with advances made in molding machines and metal molds, molding cycles have been shortened. Still another advantage is that products are flashless and runnerless, so waste produced during molding has declined.
The name “LIMS” describes a molding system in which liquid silicone rubber is used in high-precision injection molding machines. All steps are automated, from mixing to molding. This system saves labor and time, and makes it easy to produce high-quality molded items
PhD. Chemical Engineer
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