COMPOSITES BASICS: MATERIALS Calcium sulfate Kaolin Alumina trihydrate Fillers Calcium carbonate

Other Constituent Ingredients Fillers Use of inorganic fillers in composites is increasing. Fillers not only reduce the cost of composites, but also frequently impart performance improvements that might not otherwise be achieved by the reinforcement and resin ingredients alone. Fillers can improve mechanical properties including fire and smoke performance by reducing organic content in composite laminates. Also, filled resins shrink less than unfilled resins, thereby improving the dimensional control of molded parts. Important properties, including water resistance, weathering, surface smoothness, stiffness, dimensional stability and temperature resistance, can all be improved through the proper use of fillers. The thermosetting resin segment of the composite industry has taken advantage of the properties of fillers for many years. More recently, the thermoplastic industry has begun to make widespread use of inorganic fillers. Breakthroughs in chemical treatment of fillers that can provide higher filler loadings and improved laminate performance are accelerating this trend. Filler Types There are a number of inorganic filler materials that can be used with composites including: Calcium carbonate is the most widely used inorganic filler. It is available at low cost in a variety of particle sizes and treatments from well-established regional suppliers, especially for composite applications. Most common grades of calcium carbonate filler are derived from limestone or marble and very common in automobile parts. Kaolin (hydrous aluminum silicate) is the second most commonly used filler. It is known throughout the industry by its more common material name, clay. Mined clays are processed either by air flotation or by water washing to remove impurities and to classify the product for use in composites. A wide range of particle sizes is available. Alumina trihydrate is frequently used when improved fire/smoke performance is required. When exposed to high temperature, this filler gives off water (hydration), thereby reducing the flame spread and development of smoke. Composite plumbing fixture applications such as bathtubs, shower stalls and related building products often contain alumina trihydrate for this purpose. Calcium sulfate is a major flame/smoke retarding filler used by the tub/shower industry. It has fewer waters of hydration, and water is released at a lower temperature. This mineral filler offers a low cost flame/smoke retarding filler.