Out of that simple idea, Mil Spec was born. Short for “military specification,” it’s a standard defined by the military to which EVERYTHING must meet – from dimensions to materials to the way specific parts and other items are tested to everything in between. Any Mil Spec part or other item will ultimately need to be approved by a designated inspector from the United States government, so it’s safe to say that living up to these standards is of paramount importance.
So where, exactly, do phenolic plastics fall into this discussion? Let’s find out, together.
What Are Phenolic Plastics, Exactly?
But first, it’s important to get a better understanding of what the term “phenolic plastics” is describing to begin with. Also sometimes referred to as “micarta plastics,” phenolic plastics are a special type of laminated plastic created via the impregnation of layers of a substrate material with resin. At that point, the plastic material itself is then formed utilizing a very specific combination of heat and pressure.
Those resin binders are generally either phenolic, silicone, melamine or epoxies depending on the eventual application. The substrate materials can be paper, cotton, glass and more.
All of the machined plastics that you’re likely familiar with – including G10 FR4 – are not only also phenolics, but they also have Mil Spec numbers as well. In the case of G10 FR4, that’s also Mil-I-24768/27. Regular G10 material is Mil-I-24768/2, and so on and so forth.
Why Mil Spec Matters
The aforementioned G10 FR4 (Mil-I-24768/27) is known for its malleability and durability, which makes it an ideal candidate for use in things like screw terminal strips, switches that are a part of larger transformers, relays and more. The Mil Spec number goes a long way towards proving that any items made with this material will be able to stand up to whatever situation someone happens to find themselves in – even those that are naturally dangerous in what many consider to be the harshest environments on Earth.
GPO 1 (Mil-I-24768/4), on the other hand, brings together glass mat reinforcements and polyester resin binders to form an entirely different type of phenolic that is used in everything from steel framing components to area separation wall systems and more. When you think about how military bases are constructed – usually using many disparate parts as quickly as possible that need to be able to withstand incredible pressure indefinitely – you begin to get an idea of just how essential this really is.
XX (Mil-I-24768/11) falls into an entirely different category. It uses paper reinforcements and phenolic resin binders to form a very particular paper-based plastic that is a machining grade, but that also has fewer electrical properties than some other options. This is typically used for electrical insulation, as its specific properties make it ideal for applications in nearly any type of condition you can think of. From the driest of environments (think: a military base in the middle of the desert) to those with high levels of humidity (like a command panel on a naval vessel) and everything in between.
These are just a few examples of phenolic plastics and the ways that they’re used by members of the military on a daily basis. Rest assured that there are many, many more. But even though a lot of these materials couldn’t be more different from one another, they have one thing in common: that Mil Spec number lets people know beyond the shadow of a doubt that they’ve got a high quality material that they can depend on, no matter what.
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