Fillers are used in polymers for a variety of reasons that include cost reduction, improved processing, density control, optical effects, thermal conductivity, control of thermal expansion, electrical properties, magnetic properties, flame retardancy and improved mechanical properties such as hardness and tear resistance. Among polymers, PVC is still the plastic with the highest filler usage, followed by polyolefins, nylons and polyesters. Traditionally, fillers were considered as additives, which, due to their unfavorable geometrical features, surface area or surface chemical composition, could only moderately increase the modulus of the polymer, while strength (tensile, flexural) remained unchanged or even decreased. Minerals conventionally are used in polymers to reduce cost by replacing and thereby lowering usage of higher cost polymers. Other possible economic advantages were faster molding cycles as a result of increased thermal conductivity and fewer rejected parts due to warpage. Depending on the type of filler, other polymer properties could be affected; for example, melt viscosity could be significantly increased through the incorporation of fibrous materials. On the other hand, mold shrinkage and thermal expansion would be reduced, a common effect of most inorganic fillers. In the last two decades mineral producers have focused on increasing value and functionality by tailoring mineral properties through controlling particle size distribution and treating particle surfaces. Each filler type has different properties and these in turn are influenced by the particle size, shape and surface chemistry. When added to plastics, minerals generally increase density, stiffness and surface hardness; improve temperature resistance and reduce shrinkage by lowering the coefficient of linear thermal expansion. Primary end-use markets are building & construction and transportation, followed by appliances and consumer products; furniture, industrial/machinery, electrical & electronics and packaging comprise smaller market segments. Flexural modulus and heat resistance are the two critical properties of plastics that are enhanced by the inclusion of performance minerals. Automotive exterior parts, construction materials, outdoor furniture, and appliance components are examples of applications benefiting from enhanced flexural modulus. Automotive interior and under the hood parts, electrical connectors and microwaveable containers are examples of applications requiring high temperature resistance. Building industry also contributes to higher growth of minerals. Minerals such as talc can also increase lubricity and improve processing. Use of flame retardant minerals, including alumina trihydrate, antimony trioxide, magnesium hydroxide, borates and nanoclays, is growing faster because of the faster growth of non-halogenated flame-retardants. Surface treatments or coatings are primarily used to increase mineral dispersion by making it more compatible with the polymers. Fatty acids such as metallic stearates and stearic acid can improve mixing and dispersion, reduces polymer viscosity, and improves polymer stability by acting as an acid scavenger. Mineral fillers are growing faster than the overall plastics market for polymer addition segment. They grow between 5-10% depending on the type of mineral. Electronic industry which is growing at about 10% contributes to faster growth. Another high growth application for minerals is in wood-plastics composites (WPC), which is growing at a rate of more than 20% pa. Additional growth in the usage of functional fillers will stem from a) Identifying new applications for composites containing nanofillers b) Developing composites containing ultrafine particles (dimensions < 3 µm), the latter produced by special grinding methods c) The increased usage of natural fiber (flax, wood) composites, coupled with the expected significant growth in the use of nanoclay composites in the automotive industry Some exciting new application areas for composites containing nanoclays, nanosilicates, carbon nanotubes, ultrafine TiO2, talc, and synthetic hydroxyapatite are as : • Structural materials with improved mechanical properties, barrier properties, electrical conductivity, and flame retardancy • High performance materials with improved UV absorption and scratch resistance • Barrier packaging for reduced oxygen degradation • Bioactive materials for tissue engineering applications (Extracted from an article by Marino Xanthos)