The essential answers to your questions regarding silicones
Our experts answered the most commonly asked question about silicone materials and their applications. Browse through your area of interest and learn everything you need to know about it:
Silicones are everywhere in our lives in an incredible number of products, from training shoes, insulation, protecting electrical circuits, etc. Here are some key facts about the essential characteristics of silicones.
What are silicones?
Silicones are inert synthetic compounds that are designed and formulated for an almost unlimited number of applications, from insulation to materials for molding everything from tires to fine arts, via medical devices and prostheses. To be efficient in these various applications, silicones come in a variety of forms (oils, rubbers, resins, elastomers, etc.). The basic building blocks of silicones are polyorganosiloxanes, where silicon atoms are linked to oxygen to create the «siloxane» bond. The remaining valences of silicon are linked to other chemicals, such as methyl groups (CH3 - phenyl, vinyl or hydrogen) or carbon. This enables silicones to be specifically produced for different applications. They can be purchased as raw materials or commodity products, known as chlorosilanes, to customers having the ability to transform them in the specific formulations and products they need. For customers looking for ready-to-use formulations, specialty silicones are available off-the-shelf or custom-made, to meet specific applications. Both these product families of silicone polymers, raw materials and formulations for inclusion in processing, are available in different technologies: RTV-1, RTV-2, HCR, LSR, Emulsions, Resins, Greases and Compounds. These enable manufacturers to produce and cure the products in ways that suits their processes and needs best.
For further information, please check out our introduction to silicone technologies
What are silicones used for and what are their main benefits?
Several types of silicones are used, as we have already mentioned above, in an almost endless number of applications and industries. This is because they are versatile, chemically stable, thermally resistant (both at hot and cold temperatures), durable, reliable and offer specific qualities like biocompatibility for use in medical devices or food processing. Here is a representative (but far from exhaustive) list of some major applications:
- In construction, they are particularly appreciated because they can bond almost all materials, including concrete, glass, granite, marble, aluminum, steel, plastics, etc. They are durable and resist deterioration caused by rough weather conditions, moisture, sunlight (including UV rays) and pollution.
- In cooking, both at home and in restaurants, silicones are very useful for making molds, for baking in particular, because they are flexible, shock-resistant and available in a wide range of shapes. Silicones are also bacteria-and-heat resistant and very durable, even at very hot temperatures.
- Silicone technologies are critical in electrical and electronic applications to ensure long-term stability and performance of increasingly miniaturized sensitive components in mobile and other sophisticated electronic devices, such as computers and tablets.
- In renewable energy production, silicone potting, sealing and insulating products for solar, wind and hydroelectric production have become essential because they are transparent (e.g. for solar panels), stable for all systems, resist extreme weather conditions, protect against UV damage and are neutral to aggression by corrosive by-products. They contribute to all energy sectors by generating significant cost reductions and, in the long run, to the Total Cost of Operations (TCO).
- In medical applications, biocompatible silicones are safe for humans, both when used on the skin or in the body. They facilitate healing, lessen scaring in bandages because they offer good adhesion and are easily removed, reduce patient discomfort and enable the making of healing and life-enhancing devices, such as prostheses.
- In hybrid and electrical vehicles, silicones encapsulate the entire battery pack to stabilize its conductivity and insulation, protect against vibration, heat dissipation, and ensure water and dust proofing.
- In all types of vehicles, silicones are used for the different layers of airbags to ensure sealing and fabric strength, thus contributing to increased safety and reducing serious or fatal road injuries by contributing to faster and accurate inflation at the right pressure point, while avoiding cracks or leaks.
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How is silicone made?
Let’s start by a simple distinction between silicon and silicone. In fact, silicon is a chemical element (SI on the periodic table) which occurs naturally in the form of silicates that are extracted as powders through an electrochemical process. Silicon is one of the most common elements in the earth’s crust, present in many types of geological materials. It is a hard and brittle blue-grey crystalline tetravalent metalloid solid and is a natural semiconductor. This is why it is used as a key component in making microchips and is the basis for the high-tech region we all know of in California as Silicon Valley.
So, how do you transform this hard and brittle metallic element to produce the supple and rubber-like materials (oils, gums, gels, elastomers) we call silicone polymers? The key is to create chlorosilanes, which are compounds prepared by combining silicon powder and methyl chloride gas through direct synthesis by means of an electrochemical process. The resulting methyl chlorosilanes (trimethyl, dimethyl and methyl chlorosilane) are the building blocks for various silicone substances.
This is achieved in large-scale reactors and produces a crude mixture of several liquid chlorosilanes which must then be separated by distillation. The chlorosilanes are then used to produce the various silicone substances: the central silicon atom is bonded to various numbers of chlorine atoms, each of which provide a potential reactive site for the hydrolysis reaction that enables the length and branching of the polymer molecular framework to be controlled and, ultimately the raw material or specialist formulation used in a great many applications and industries.
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Is silicone heat resistant?
Heat resistance, thermal stability and thermal conductivity are three of silicone’s essential features. This means silicone, in a wide range of formulations and formats, is ideal to ensure thermal management in many applications in complex assembly systems, such as engine housings or battery packs for electric vehicle where parts are subjected to high temperatures and wide variations. The heat resistant capacities of silicones are also useful in sensitive electronic parts or in harsh environments. Silicone provides reliable and durable performance because it remains unaltered over a very wide range of temperatures, from lows of -50°C to highs of 250°C, and over long periods of time. Designed to meet specifications, it improves both industrial processing and the final products produced by manufacturers.
Is silicone a good heat insulator?
Silicone is an excellent heat insulation material used in a wide variety of applications, from sealants in construction to domestic appliances, via the protection of electronic parts. It can be formulated to insulate and protect against in a wide temperature range, from -50°C to 250°C, over long periods of time. For industrial assembly and electronic protection, for example, silicone offers different formats and degrees of density, making it a highly flexible product that can be used simultaneously for heat insulation, bonding, and protection against all hazards. Silicone offers other features: excellent mechanical properties to withstand stress, easy installation and maintenance, water repellency and more resistance to UV and extreme temperature fluctuations than organic polymers. Therefore, silicone is a prime material for heat insulation, both in terms of performance and compliance with rigorous international standards and specifications.
Does silicone insulate?
Silicones offer excellent electrical insulation properties and can be formulated in various ways to meet different needs. Silicones offer several advantages to ensure electrical and electronic insulation in areas such as industrial assembly, both upstream in the manufacturing process and downstream in terms of the reliability and durability of finished products. Simply put, silicone-based products used in gasketing, bonding, potting and encapsulation of electronic components in industrial assembly get the job done because they can be formulated to meet very specific insulation requirements, such as the right balance between dielectric strength or electrical conductivity. Therefore, silicone elastomers are used in high-performance applications, especially in harsh environments, where other polymeric materials will fail. They ensure reliable and durable insulation over a wide range of temperatures (from -50°C to 250°C) and extreme environmental exposure (humidity, UV, ozone). Silicones also control the entire temperature management system of power systems by optimizing the trade-off between heat and power transfer, conduction and convection, thus reducing thermal runaway, while ensuring safety.