How Thermal Insulation Solutions Protect Against Heat
Harsh and demanding applications often require heat shielding through thermal insulation materials that can resist high temperatures. With a wide range of insulation materials available, manufacturers are able to meet the demands of any high temperature application while protecting their products from damage. Many of these materials provide ample thermal conductivity, high temperature resistance, internal strength, and other resistances and capabilities, allowing engineers familiar with the materials to design a thermal insulation solution that provides the protection you need, where you need it most.
Choosing the right insulation material can be the difference between superior performance and application failure. Excessive heat can lead to component damage, adhesive bond failure, fire hazards, and much more. How do insulation materials provide this high level of protection, and how can you choose the right material for your application?
What Applications Often Need Heat Shielding and Insulation?
Appliances
Automotive
Aerospace
Industial
Electronics
HVAC systems
How Materials Provide Insulation
In the most basic explanation, insulation slows the transfer of heat from its source to any other location. When insulating materials are placed by a heat source, they actively resist the flow of heat and minimize the transfer from passing through the material.
There are three types of heat transfer:
Convection: heat transfer through gases and liquids (e.g., boiling water or steam)
Radiation: heat transfer through electromagnetic waves (e.g., heat from the sun or from flames)
Conduction: heat transfer through solid materials by physical contact (e.g., touching a solid surface that is hot)
Regardless of the source of the heat and the method of transfer, insulation materials work by slowing the flow of convective and conductive heat, and by reducing radiant heat gain. These materials primarily stop heat transfer by:
Filling voids
Resisting compression
Blocking air movement
Resisting moisture
The best types of thermal insulators are made of up particles that have strong bonds, which hold the particles rigidly in place. When the particles of a material don’t move around easily, energy transfer to them is limited. These materials also can resist total compression well, as it’s essential for air pockets to remain in the material, which helps trap heat inside the material rather than allowing it to pass through.
Materials that do not insulate well are conductors (like metal). These types of materials are made up of particles with loose bonds, which allow for greater heat transfer.
The Difference Between R-values and K-values
Both R-values (thermal resistance) and K-values (thermal conductivity) measure the “insulation” provided by a material, just in different ways. Both are useful, and both should be used when deciding on the material to use for thermal insulation.
K-values measure the amount of heat transfer through a material. It will effectively tell you how well the material resists heat transfer in general without taking into consideration the material thickness. Higher k-values mean the material is a better insulator and can be used in higher temperature applications.
R-values deal with thermal resistance. They still measure how well the material prevents heat transfer, but this value is in relation to the material’s thickness. This will give you an idea as to how much “insulation” you are getting at the specific material thickness. This can help you determine how thick your material needs to be to provide the level of insulation you need.
The Difference Between Flame Resistance and Thermal Resistance
As already noted, thermal resistance is a material’s ability to withstand the flow of heat. It determines whether or not the material will serve as a good insulator. This differs greatly from flame resistance, which is a material’s ability to withstand catching fire and spreading flames. It’s important not to confuse the two because although a material may act as a good insulator, this doesn’t mean it is rated to operate in applications where it may be exposed to open flames.
Flame resistant materials are generally able to be exposed to open flames without catching fire. Some materials can be flame resistant (they are inherently nonflammable) or flame retardant (the material is chemically treated to be slow burning).
Thermal Insulation Material Options
Closed cell foam rubbers: ideal for lower temperature level insulation (below 225°F), these materials provide a basic level of insulation at a relatively low cost. Many types carry UL 94 ratings above specific thicknesses. They can also be used to block water and vapor, making them ideal for gasketing applications.
Silicone foams: ideal for mid temperature level insulation (up to 400° F), these foams are highly effective insulators, carry UL94 V-0 flame ratings, are highly resilient, and are highly resistant to oils, UV light, and mechanical fatigue. They are often used in high performance, high temperature sealing applications. Bisco HT800, HT 820 are some of the most common silicone foam products used.
Silicone Sponge: These closed cell sponges provide slightly higher heat resistance (up to 500° F), but do sacrifice some insulation effectiveness versus their foam cousins. These foams also carry UL94 V-0 flame ratings, are highly resilient, and are highly resistant to oils, UV light, and mechanical fatigue. They are often used in high performance, high temperature sealing applications. St. Gobain’s Norseal R10460 and R10570 M are some of the more common products in this category.
Thermal fiberglass paper: these glass fiber papers can withstand intermittent operating temperatures of 1200 °F while maintaining a high dimensional stability. These also meet UL-94 V-0 as well as low smoke and odor requirements. They are often used as gaskets in gaskets in stoves, boilers, or furnaces, or in aerospace and automotive applications. Maniglas 1200 is the standard bearer of the industry in this category, though the more cost effective Maniglas 2000 provides much of the high temperature insulation needs.
Alkaline silicate (AES) papers: these thin and flexible papers offer excellent thermal insulation at 2000°F and are immune to thermal shock. They are a low bio-persistent materials that are ideal for applications that need to comply with stringent European regulatory requirements, including directive 97/69/EC and EC/1272/2008. Insulfrax and Superwool are the most commonly used AES products
Ceramic fiber papers and felts: with operating temperatures as high as 2300°F, these materials offer some of the best thermal insulation solutions on the market. They are also highly resistant to chemicals, concentrated alkalis, and some acids. As a highly flexible material with great dielectric strength, they can be used as wraps or to cover irregular spaces. Lytherm 970L and 550L rival products like Fiberfrax and Kaowool in this category.
High temperature needled mats: available in multiple different material types, the most common being eglass, these low-cost mats offer a good replacement for ceramic fiber paper. They can withstand temperatures between 1500 °F and 2000 °F and meet various Military and Coast Guard Specifications. Capriton is a well-known brand that has now been replaced by lower cost alternatives
High temperature fabric tapes: generally made from either fiberglass, basalt, or ceramic fiber, these tapes are woven to be flexible, conformable, and durable across different applications with varying requirements. Their thickness and density make them great high temperature gaskets. They are often used in boiler pipe wraps, motorcycle exhaust wraps, and other applications that need flexible thermal insulation.
Customizing Thermal Insulation Materials for You
At Engineered Materials, we work with a variety of insulation material options to customize them for your specific application. We can combine many different types of rubber, foam, and other materials with thin aluminum foil, giving you a custom material that acts as a more effective heat shield. We can also combine most of our insulation materials with various types of pressure sensitive adhesives, creating a custom adhesive tape that is die cut to fit specifically within your application.