Filler |
Primary Function |
Notes |
Aluminum |
Dimensional control, Reinforcement, Exotherm control, Corrosion resistance |
Excellent corrosion resistance.
|
Alumina |
Electrical insulation improvement, Abrasion resistance |
Good electrical insulator. |
Alumina trihydrate (aluminum hydroxide) |
Reduce cost, Flame and smoke suppression |
Decomposes at ~180 °C, absorbing heat and giving off water. Low absorption of UV suitable for UV cure systems. |
Aluminum oxides |
Reduce cost, Electrical insulation improvement |
Electrical insulator with high thermal conductivity, chemically inert and white. |
Antimony oxides |
Flame and smoke suppression |
Used with halogen containing polymers. |
Asphalt (bitumen) |
Reduce cost, Rheology control |
Plasticizer. |
Barium sulfate (barite) |
Electrical insulation improvement,Pigmentation |
High specific gravity (4.4), sound deadening, good chemical resistance. |
Beryllium oxide |
Electrical insulation improvement |
High thermal conductivity and electrical insulation. |
Boron nitride |
Electrical insulation improvement |
High thermal conductivity and electrical insulation. |
Calcium carbonate (limestone) - ground |
Reduce cost, Rheology control |
Most widely used filler / extender. Soft. |
Calcium carbonate - precipitated |
Reduce cost, Rheology control, Reinforcement |
Finer particle size than ground CaCO3. |
Calcium hydroxide (hydrated lime) |
Reduce cost, Rheology control, Reinforcement |
Same benefit as CaCO3 (but including functionality, lower abrasion, and lower density). |
Calcium metasilicate (wollastonite) |
Reinforcement, Electrical insulation improvement, Pigmentation |
High aspect ratio. |
Calcium sulfate (gypsum) |
Reduce cost, Reinforcement |
Hydrous and anhydrous forms available. |
Carbon black |
Electrical insulation improvement, Pigmentation, Shielding |
Many types-acetylene black best for electrical conductivity. Good UV barrier. |
Cellulosic derivatives (particles and fibers) |
Reduce cost, Rheology control, Reinforcement, Degradability |
Natural product from plants. |
Clays (kaolin, fuller’s earth, bentonite, etc.) |
Reduce cost, Rheology control |
Soft extender. Kaolin is 2nd most often used extender. |
Copper |
Conductivity |
Provides good electrical and thermal conductivity. |
Fibers (glass, aramid, cellulose, etc.) |
Rheology control, Reinforcement |
Large aspect ratio provides reinforcement. |
Gold |
Conductivity |
Provides good electrical and thermal conductivity. |
Metal oxides (e.g., iron, lead, zinc) |
Pigmentation, Cure and pot life control |
Pigment. Sometimes use as a catalyst. |
Magnesium hydroxide |
Flame and smoke suppression |
Has a higher decomposition temperature than aluminum trihydroxide. |
Mica (sheet and ground) |
Dimensional control, Electrical insulation improvement, Moisture and chemical resistance, Permeability control |
High aspect ratio, platelets provide impermeability, low coefficient of expansion, good electrical resistivity. |
Microspheres (ceramic or plastic) |
Specific gravity |
Very low specific gravity useful for syntactic foams. |
Nickel |
Electrical insulation improvement |
Provides good electrical and thermal conductivity. |
Potassium silicate and sodium silicate |
Reduce cost |
Water soluble extender for waterborne adhesives and sealants. |
Resin (natural and synthetic) |
Reduce cost, Rheology control, Specific gravity, Modification of surface properties |
Many types are available, generally in particle or solution form. |
Sand (ground silica) |
Reduce cost, Dimensional control, Rheology control , Reinforcement |
Inexpensive, chemically inert. |
Silica (precipitated and fumed) |
|
Hydroxyl groups and very high surface area provide hydrogen bonding and strong thixotropy properties. |
Silver |
Electrical insulation improvement |
Provides optimum electrical and good thermal conductivity. |
Talc (magnesium silicate) |
Reduce cost, Rheology control, Reinforcement, Modification of surface properties |
Soft inert filler, good electrical insulator. |
Titanium dioxide |
Pigmentation, Shielding, Optical properties |
White pigment. UV absorber. |
Wood flour |
Reduce cost, Rheology control, Reinforcement, Permeability control, Degradability |
Fibrous reinforcing agent. Porous nature increases permeability. |
Zeolite |
Cure and pot life control |
Moisture scavenging molecular sieve. |
Zinc sulfide |
Pigmentation, Optical properties |
Next highest refractive index to TiO2. |