When mineral fillers were first introduced to the composites industry it was as a means of reducing cost.
At that time, excessively high loadings were used and this resulted in a serious deterioration in the mechanical strength and chemical resistance of mouldings produced.
Today, the effects of fillers are better understood and they are used to enhance and improve certain properties of a resin. Filled resins exhibit lower exotherm and shrinkage characteristics than unfilled systems, and they tend to be stiffer, though more brittle. The level of cost reduction achievable by the use of fillers is no longer a significant factor.
The range of fillers available is now wide and varied and some of those most commonly used are
described overleaf.

Putty (Talc)

Magnesitic talcs are used to increase ‘bulk’ and reduce exotherm temperature, usually in casting applications.

Dolomite

Dolomite is an anhydrous carbonate mineral composed of calcium magnesium carbonate, Ideally CaMg. The term is also used for a sedimentary carbonate rock composed mostly of mineral Dolomite.

Aer-o-sil or Cab-O-Sil Powder

Thickening agent for resins and gel coat. Add Cab-o-sil - Aer-o-sil powder to make a paste. Stir or mix in. Quart size should thicken a quart of Gel Coat. Some resins absorb more, requiring more Fumed Silica powder.

• Easy to dispense Quart and Gallon packaging Aer o sil.
• Bulk packaged in Zip Lock bag for ease of use and storage.
• Cab o sil can shift color slightly lighter.
• Will shift acrylic and epoxy resins yellow.
• Will thicken silicone and other resins (trial required) into a higher viscosity.
• How to thicken Resin and Gel coat into a paste or putty with Cabosil Aerosil.