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Team Modus™ on 02/22/2022

MIL SPEC AA-59588 Class 3 Silicones

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    Silicone is a durable material that is perfect for an enormously diverse range of applications. But when you’re talking about military, defense and aerospace applications, not all silicones will do the trick. 

    In fact, only a handful of silicones will live up to strict requirements of military specifications (MIL SPEC). More specifically, there are only three classes of silicones that meet the standards of MIL SPEC AA-59588. In this blog post, we’re going to discuss MIL SPEC AA-59588 Class 3 silicones.

    Read on to learn about Class 3 silicones and see some examples of materials in this exclusive category.

    Experience with MIL SPEC materials is one thing, but when you’re designing a sensitive defense or aerospace part, you need access to vast manufacturing and materials knowledge. You get exactly that when you choose Modus Advanced as your manufacturing partner. Contact us to learn more about how we can help you.

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    Intro to MIL SPEC AA-59588

    The U.S. General Service Administration’s (GSA) MIL SPEC AA-59588 governs silicone materials for use in military and defense applications. The specification divides silicones that meet the general standard into six classes:

    • 1A
    • 1B
    • 2A
    • 2B
    • 3A
    • 3B

    Silicones fall into one class or the other based on their durometer (hardness) and resistance to hot or cold temperatures. Like all silicones, MIL SPEC AA-59588 silicones are chemically inert and resistant to ultraviolet light and ozone.

    About MIL SPEC AA-59588 Class 3 Silicones

    For the purposes of this article, we are discussing just two of the six classes we described above: the two subclasses of silicones in Class 3, 3A and 3B.

    Many Class 3 silicones under MIL SPEC AA-59588 share a few key characteristics. For one thing, their durometers are often in the middle range, somewhere between 50 and 70. But perhaps more importantly, Class 3A and 3B silicones meet strict flex-fatigue requirements.

    For silicones that meet MIL SPEC AA-59588 requirements, flex fatigue is tested with the DeMattia flex resistance test. Flex fatigue resistance is particularly important in aerospace and defense, and that is why Class 3 MIL SPEC AA-59588 silicones have specific requirements for flex fatigue testing and resistance capabilities.

    Some Examples of MIL SPEC AA-59588 Class 3 Silicones

    Dozens of silicone materials from various material manufacturers meet the requirements of MIL SPEC AA-59588 Class 3. With so many to choose from, it can be helpful to look at some examples of particularly high-quality options. That is why we have included several Class 3 silicones from Specialty Silicone Products (SSP) below.


    SSP-200-T is a durable and versatile Class 3B silicone from SSP that meets the flex fatigue requirements set under MIL SPEC AA-59588. With a durometer of 50, this heat-cured material sits right in the middle in terms of hardness, and it is rated to resist very cold temperatures.


    With a durometer of 70, SSP-2521-T is on the somewhat harder end of the Class 3 silicones. This is a heat-cured Class 3B silicone, which means it meets the strict flex fatigue resistance requirements of the class in the DeMattia flex resistance test.


    SSP-2523-T is a Class 3A silicone that is rated to resist even lower temperatures than SSP-2521-T or SSP-200-T. It has a durometer of 50 and is cured with heat. While this material is resistant to flex fatigue, it is not as sturdy under that kind of pressure as the other materials in this class that meet DeMattia flex resistance test requirements.


    Another Class 3B silicone, SSP-392-T is cured with heat and has a durometer of 60. This material meets the requirements for flex fatigue resistance set by Class 3B, and it is resistant to very low temperatures — although not as low as the temperatures SSP-2523-T is rated to resist.

    Choosing the Right Manufacturing Partner

    The materials described above are of extremely high quality and up to the incredibly high standards of the military. If these are the materials your project requires, you don’t want their quality to be wasted because someone else in the chain of production does not have high standards for quality.

    That is especially true for the manufacturing partner you select. When you’re working with MIL SPEC AA-59588 Class 3 Silicones, you need a partner who has not only AS9100 and ISO 9001 certifications, but demonstrable experience working with these materials. 

    Your Partner for MIL SPEC Manufacturing

    Whether you’re designing a satellite or a smartphone, if you need it to live up to MIL SPEC standards, you need the expertise of Modus Advanced. Our team of engineers and manufacturing experts can help you with every step, from ideation to material selection to production.

    In other words, MIL SPEC AA-59588 Class 3 silicones are just one part of the equation. We’re ready to help you solve the whole equation and dial back your stress. To learn more about how our team can help you with your design, give us a call at 925-960-8700 or contact us online today.


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