Overview
Among experts, mica is considered to give the best overall performance of all the minerals added to plastics, paints and coatings. To understand why that is, we need to talk about a property known as aspect ratio. Simply put, aspect ratio is the size of the largest particle dimension divided by the smallest particle dimension.
For spheres or cubes, the aspect ratio is one and such particles are found to be least beneficial to the mechanical and various other properties when added to plastics or coatings. Medium aspect ratio is associated with well-known minerals such as talc, kaolin clay or wollastonite. These are found to give somewhat improved strength and stiffness. However, true reinforcement is only achieved when using high aspect ratio particles including glass fiber, carbon fiber or mica.
Advantages include:
- Very high stiffness
- Very high strength
- Increased HDT/Vicat
- Low CTE / shrinkage
Glass fiber is the most prevalent reinforcement today, but mica rivals or surpasses the performance of glass fiber in many cases.
Here are the benefits of high aspect ratio mica over glass fiber:
- Mica reinforces in all directions, but glass fiber only reinforces in one direction (parallel to the fiber length) meaning that real-world results are superior with mica
- Mica greatly reduces CTE and warpage compared to glass fiber
- Mica acts as an excellent barrier to liquids and gasses due to the platy particles whereas glass fiber does not
- Glass fiber is notoriously abrasive requiring special hardened processing equipment to prevent excessive wear and maintenance whereas mica has low hardness
- Mica has been shown to impart substantial sound-damping
Looking at all of the positives, you may wonder if there anything to be aware of when using mica as a reinforcement. In fact, there is. As performance depends on the high aspect ratio, it is of paramount importance to preserve that aspect ratio during processing whether that be by extrusion, injection molding or any other processing step. Broken particles have lower aspect ratio, so just as with carbon or glass fiber, gentle handling and low shear give optimal results.
Why Choose Arctic Mica?
To make superior mica-based products, Arctic Minerals starts with the finest raw materials sourced globally. Typically, producers are bound to a mine they own and have to sell whatever it produces. Because Arctic can choose from multiple sources, you get the best products plus security of supply.
Arctic serves large global OEMs who need to know that they will receive material no matter what. In the USA, we have duplicate production facilities in separate states to comply with strict production redundancy requirements of automotive clients. Arctic can supply the same products all around the World for our global customers.
Arctic Minerals is focused on mica, so our staff has deep experience. To master a topic takes focus and we are proud to have decades devoted to this one high performance mineral. How does that help our customers? Here are some examples…
Arctic Minerals uses a special milling technology uniquely designed to delaminate the mica particles without breaking them. This ability to preserve aspect ratio leads to the exceptional property enhancements described earlier.
A wide range of tailor-made surface treatment options is also available for when customers need coupling, heat resistance, decoupling or dispersion. Accurate dosing ensures consistent surface treatment and in-house QC testing guarantees that every shipment meets specifications, so that you receive good product every time.
BriteFlex™ Muscovite or ThermaFlex™ Phlogopite Mica?
The two main commercial types of mica are generally similar. Muscovite products are light in color, so they are often selected in paint applications or in plastics where a specific appearance is sought. Phlogopite mica is tan in color but offers other distinct advantages. For example, ThermaFlex is specially purified and so contains no detectable crystalline silica. That gives regulatory benefits and offers very low abrasion, less machine wear and therefore reduced maintenance costs. Phlogopite also has extreme high temperature resistance and is used in cementitious fire-resistant coatings.
Typical Properties:
Surface treated grades are available with a wide range of organosilane coupling agents tailored to each customer’s requirements.
Although mica platelets are resistant to fracture, it is prudent to use mixing and processing conditions that are gentle enough to prevent breakage. For example, the use of high-flow resin and low shear and always dose the powder into liquid to avoid dry particles from grinding together.
Contact Arctic Minerals
If you would like to hear more about our mica product line, then feel free to contact us today. We have experts to help you select the best grade for your application and to supply samples for evaluations.