The use of chemically modified fillers and reinforcements for plastics in developed regions of North America has grown dramatically over the past decade, reaching almost 1.25 million tons in 2005. As more performance fillers and reinforcements find use in thermoplastics, the demand for products treated with coupling agents and dispersion aids has experienced growth of over 9% pa over the past decade. Reinforcements, specifically fiberglass, have found application in plastics for a long time, but in recent years the use of natural fibers, including wood flour and agricultural fibers have grown 20% pa in composite building products and automotive components.

Chemicals have been used to modify mineral fillers and fiber reinforcements for plastics for decades, for two main functions, namely, to reduce agglomeration of fine particle size fillers and improve dispersion in plastic compounds and to couple the filler or fiber to the polymer, thus allowing increased loading and improved performance.

Dispersion properties have become more important in recent years as mineral filler producers continue to develop finer particle size products. Generally speaking, the need for dispersion treatments increases exponentially when filler particle size falls below 3 microns. Calcium carbonate is the major filler employing dispersion aid treatments, but numerous other fillers are now available in sub-micron size including:

		Nanoclays
		Talc
		Wollastonite
		Silica

When compounding, there is also adhesion problems between non-polar polymers and fillers/fibers, so wetting by the polymer is critical. The size and geometry of the filler/fiber particle influence the ease with which it can be compounded and the bond strength to the polymer. Adhesion between the surface of the inorganic filler/fiber and the organic polymer can be improved by creating multiple hydrogen bonds on the inorganic surface through the use of coupling agent chemicals. Fillers and reinforcements, besides being used for dispersion and coupling, are surface treated for several additional reasons, including:

In 2005, an estimated 0.7 million tonnes of surface-modified minerals and 0.65 million tonnes of treated reinforcements were consumed in plastics applications in North America . Leading treated fillers include alumina hydrate, calcium carbonate, kaolin, mica, talc, and wollastonite. Fiberglass dominates in reinforcements, but natural fibers including wood flour, flax, kenaf, are rapidly growing in use.
Silanes and maleated polyolefins are the major coupling agent chemicals used to treat fillers and reinforcements. Stearates are the dominate dispersion treatment chemical. In 2005, the combined use of these chemicals with minerals and reinforcements in plastics exceeded US$70 million in value.
Leading applications for treated minerals and reinforcements include such plastic building products as pipe, wire and cable, decking, siding, and window and door profiles. Automotive plastics that incorporate calcium carbonate, talc, kaolin, wollastonite, or fiberglass are another major market. Appliances use significant amounts of treated fillers and reinforcements, especially in parts made from polypropylene. Plastics packaging is a growth market for treated fillers, mostly in films, but more recently in rigid packaging.

Several driving forces are driving the demand for surface-treated minerals and fibers in plastics, such as

The future use of chemically modified fillers and reinforcements in plastics is expected to grow to almost 2 million tonnes in 2010. The rate of growth during this period will be 1% to 2% faster than the expected growth in demand for plastics, illustrating the increasing use of these products. The most rapidly growing treated mineral will be talc, followed by wollastonite.

The demand for chemical treatments for minerals and reinforcements will grow both from increasing use on pre-treated fillers/fibers as well as from increased in-situ addition by compounders. Maleated polyolefin additives will grow the most rapidly due to the strong growth expected in polypropylene applications. Overall, the demand for chemical treatments will increase by almost 50% by 2010.