CeramicĬeramic microspheres are usually found being used in the paint and coatings industries. You can learn more about the manufacture of cenospheres in this YouTube video. This makes them very useful for any number of filler purposes for construction products, as well as in the manufacture of composites with “spray-up, hand lay-up, resin transfer molding and syntactic foam applications.” These alumina-silicate balls range in size from 5 to 500 µm and are usually hollow, giving them a very low-density. CenospheresĬenospheres are made from the pulverized fuel ash produced as a waste product from coal-fired power stations. One of the world’s leading manufacturers of microspheres, Expancel (which is part of the Akzo-Nobel group) explains more about the production and many applications of gas filled polymer microsphere in this YouTube video. This gives them a very large displacement to weight ratio, making them a popular resource in the manufacture of, amongst other things, spray-up fiber-reinforced thermosetting composites and extrusion applications. Hollow plastic microspheres have incredibly low densities, with some having specific gravities as low as 0.025. Once the heat dissipates, the spheres rebound.” This gives plastic moulding manufacturers greater control over thermal expansion. By incorporating plastic microspheres, as the part heats up, the resin is able to expand inward, causing the microspheres to compress. The same is true for microspheres used in heat manufactured composites, as Rosenbusch makes clear, saying, “The heat of exotherm during cure can be problematic in composite manufacture. However, once the material hits the mold and returns to ambient pressure, the microspheres will rebound to their spherical shape.” In a spray-up application, for instance, the microspheres will deform when the resin is pressurized prior to spraying. When the pressure is released, the microspheres tend to recover. This is largely because polymer microspheres are able to collapse (due to heat and/or pressure) and then bounce back into shape when conditions return to normal.Īs Chris Rosenbusch, marketing manager for microsphere manufacturer Expancel Inc., explains, “Excessive pressure will cause the plastic sphere to flatten but not burst. The result is a rigid, hollow sphere manufactured with an eye to increasing crush resistance (that is, the ability to withstand external pressure and avoid fracture of the bubbles) without sacrificing low density.” PlasticĪlong with glass, the other most common form of microsphere are those made from plastic. Continued heating activates the blowing agent, which releases minute amounts of sulfur gas that form bubbles within the molten glass droplets. The particles are run through a high-temperature heat transfer process, during which the viscosity of the glass drops and surface tension causes the particles to form perfect spheres. Trace amounts of a sulfur-containing compound, such as sodium sulfate, are then mixed with the glass powder. Glass is initially produced at high temperatures from soda-lime-borosilicate, after which it is milled to a fine particle size. They are made from a multi-step process, in a manner described by Karen Wood in the industry journal Composites World, as follows “In general, a multistep process is used to produce high-temperature glass microspheres. One of the best selling forms of microsphere are those made from glass. With this in mind, here are some facts about these powerful spheres. In the world of modern engineering, microspheres can be made from a variety of materials, for a vast range of uses, function in numerous industries, and are beginning to become an indispensible world commodity. Who would want to argue with Webster’s dictionary? But there is in fact much more to microspheres than this simple definition. Sometimes they are filled with a substance (such as a drug) for release as the shell is degraded.”Īll of which, is true. They have a very small diameter usually in the micron or nanometer range. Well, to quote Webster’s dictionary, they are, “spherical shells that are usually made of a plastic polymer or glass. Microspheres are big.īut what exactly are these tiny materials that are making such a large impression in so many markets? Microspheres have been known for years, but as demand for improved materials and increased functionality from everyday products grows, so too has demand for these strong yet intricate little balls.
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