Beyond R-Value: What Should You Look for in a Thermal Insulation Material?
When it comes to thermal insulation, R-value is often one of the leading metrics for assessing a material’s effectiveness. However, engineers and product designers must consider a broader range of factors to ensure that the insulation material chosen is the most suitable for their application. What are the critical considerations outside of R-value? There’s a lot that goes into choosing the right thermal insulation material for your specific needs.
K-Value vs R-Value
While R-value measures a material's resistance to heat flow (a higher R-value indicates better insulation), K-value, or thermal conductivity, measures how easily heat can pass through a material independent of thickness. It essentially indicates how well a material conducts heat, with lower K-values representing better insulating properties.
The relationship between K-value and R-value is direct: R-value is technically derived from K-value (where R = L/K) The “L” represents a material’s thickness and the K represents the material’s thermal conductivity. While R-value can be useful in determining a material’s insulation capabilities at a specific thickness, K-value is more useful when comparing materials to understand which allows for lower heat transfer, especially when the application involves variable thicknesses and temperatures. K-value will also change with temperature exposure, so consider the operating environment and the application’s temperature requirements (including potential fluctuations in temperature) when selecting your insulation material.
The Application’s Temperature Requirements
When evaluating potential thermal insulation materials, the operating temperature range of your application can affect the K-value of the insulation material. Assess the temperature extremes your product will face and determine the K-value needed at that particular temperature range. Remember that high-temperature environments may require materials with stable K-values at elevated temperatures. It may be necessary to include additional materials, such as aluminum foil layers, for enhanced shielding and thermal performance. For temperatures up to 1,100°F, thermal fiberglass papers and eglass needled mats are excellent alternatives. For applications where temperature extremes are commonplace up to 2000°F, ceramic fiber paper or alkaline earth silicates are excellent options.
It's also important to consider the materials:
Thermal Stability: the material's ability to maintain its thermal performance over the expected temperature range. Materials like silicone foams maintain stability in high-temperature environments, whereas others may degrade over time.
Thermal Conductivity: understand the thermal conductivity of the material in your specific application. Lower thermal conductivity is ideal for high-temperature insulation, as it slows down heat transfer.
Melting Point: ensure that the insulation material’s melting point exceeds the maximum operating temperature to prevent material failure. Also note whether the material will be exposed to open flames, as material flame retardancy will then become an additional consideration.
Material Loss on Ignition (LOI)
Loss on ignition (LOI) measures the amount of material that vaporizes and escapes when exposed to extreme temperatures. Materials with high LOI values may degrade quickly, losing both thermal and physical properties at temperature extremes. It is important to understand the values and ensure that application temperatures remain below those where LOI of a material begins to accelerate.
Material Dielectric Strength
Dielectric strength is essential when insulation materials are used in electrical or electronic applications. It measures the material's ability to resist electrical breakdown. If your product involves high voltages, the dielectric strength of the insulation must be sufficient to prevent electrical failures. This is particularly critical in industries like aerospace, automotive, and electronics, where insulation may be exposed to high voltages. If your application will be exposed to electrical currents, consider the additional of electrical shielding and insulation materials.
What Testing Standards Are You Required to Meet?
If compliance with industry standards is a concern, ensure that the insulation materials you choose meet the specific safety and performance requirements. Some key standards to consider include:
UL-94 V-0: this standard tests the flammability of plastic materials used in devices and appliances. A V-0 rating indicates that the material stops burning within 10 seconds on a vertical specimen and does not drip flaming particles.
MIL-I-16411 Type II: this military standard specifies the requirements for insulation felt, thermal, and glass fiber.
MIL-I-24244: this standard covers insulation materials with special corrosion, chloride, and fluoride requirements
Coast Guard Specification for Incombustible Materials #164.009: this standard is used for noncombustible materials used in marine applications, where fire resistance is critical.
What Compatibility Do You Need with Pressure Sensitive Adhesive (PSA) Tapes
Thermal insulation materials often need to be combined with PSA tapes for easier application and/or long-term bonding. Take into account:
Single-Sided vs. Double-Sided Tapes: Depending on your application, you may need single-sided PSA tapes like reflective mylars or foils or double-sided PSA tapes for bonding insulation materials to surfaces.
Bond Strength: temporary bonding solutions may require fast acting adhesive strength, while permanent applications will need strong, durable bonds that withstand temperature variations and other environmental conditions.
Temperature Resistance of the Adhesive: if the PSA tape is the primary permanent bonding method, ensure that it can resist the operating temperature of the application without losing adhesion. High-temperature adhesives like silicone are ideal for applications involving extreme heat, while rubber adhesives will not perform very well under high temperatures.
Is Chemical Resistance a Factor?
Where will your insulation materials be placed? Consider the environment, its hazards, and any other exposures. Ask if your insulation material needs:
Moisture Resistance: evaluate the material’s ability to resist water absorption and hydrolysis, which can degrade insulating properties.
UV Resistance: consider exposure to sunlight, as UV resistance will be necessary to prevent material degradation.
Chemical Resistance: consider the potential exposure to oils, solvents, or corrosive substances. Will there be any exposure to acids, alkalis, bleach, or any other substances?
Mechanical and Physical Properties
What kinds of mechanical stressors will your material be exposed to? Durability is critical in ensuring that the insulation material maintains its performance over time, so consider the material’s:
Abrasion Resistance: in applications involving mechanical stress, the insulation material must resist wear and tear.
Tear Strength and Tensile Strength: the material should resist tearing and breaking, especially when elongation forces are applied.
Dimensional Stability: does the material need to maintain its shape and size under stress and temperature variations? Its ability to maintain its initial shape and size will ensure consistent insulation.
Flexibility and Conformability: flexibility is important for insulation materials used in applications with irregular surfaces or tight spaces. Materials that conform easily to various shapes provide better insulation and are easier to install.
Weight and Space Specifications
Material weight and size can be important factors if your application has strict dimensions or restriction on total weight. When evaluating the weight and space requirements of your thermal insulation material consider the:
Material Thickness vs. K-Value: the thickness of your insulation material is directly tied to its thermal performance (R-value), but increasing thickness isn’t always an option, especially when space is limited. In these scenarios, selecting thin materials like insulation papers with a low K-value can provide high thermal resistance without taking up excessive space.
Space Optimization in Constrained Environments: Many applications involve tight or irregular spaces where bulky insulation materials are impractical. Flexible, conformable insulation options can be die-cut to fit within complex spaces without sacrificing thermal performance.
The Trade-Off Between Insulation Performance and Weight: While heavier, denser materials may offer superior thermal performance, they could be detrimental to applications where weight reduction is critical. Carefully balance the need for thermal protection with the design constraints of the final product. High-performance insulation materials can deliver strong K-values in thinner profiles.
Work with the Right Fabrication Partner
At Engineered Materials, we can help you customize your thermal insulation materials to ensure they fit perfectly into your product’s design, optimizing both thermal performance and assembly efficiency. We align with your product’s design specifications, allowing your insulation solution to be customized to highly specific shapes or sizes with tight tolerances.
Ready to create a custom thermal insulation solution? Get in touch with us today to talk about what’s possible.