Mineral fillers

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Mineral Fillers ©2009 Dr B C Paul Credit is given to the following sources, SME Industrial Minerals, Mindat.org, USGS Minerals Information, Geology.com, mii.org, Webmineral.com, Geology.com What and Why of Mineral Fillers • Mineral filler is ground up rock added to a mix – The mineral filler is an additive and modifier, not the main product • Mineral fillers enhance and alter the product • Mineral fillers help control product costs by displacing more expensive ingredients and taking up space in a product matrix Factors Typically Considered in Filler Selection • • • • • • Cost Hardness Particle Size and Shape Color Refractive index properties Chemical properties The Paper Market • Paper uses fibers to provide strength, but the smoothness, and reflective properties come from filler – Kaolin dominates and provides the brightness to the surface • Need nice white grades of clay • Needs to thin down nice so you can get smooth thin coatings (rheology) – Calcium Carbonate is gaining ground • Not making paper with acid chemistry as much so calcium carbonate reactivity not a problem • Can get from natural grind • Or precipitation from solution – Talc • Helps prevent clumping of wood fibers – Amorphous silicates • Adsorb and prevent ink strike through – Alumina Tri-hydrate • Releases a lot of water at low temperature and makes paper more fire retardent Talc Mg 3Si 4O 10(OH)2 Hardness (softest mineral) S.G 2.58 - 2.83 Color Colourless, white, pale green , bright emrald-green to dark green , brown, gray Greasy feel Paint and Ceramics • Many filler characteristics similar to paper – Titanium Dioxide provides great whiteness but it is more expensive – Pyrophyllite also used • Pyrophyllite is an important ceramic filler – Talc also used – Wollastonite plays similar roles • It provides permanent expansion on heating (great if something else is shrinking) – Of course cheapies like calcium carbonate and lesser talc are also valuable UV Absorbance • Titanium Dioxide minerals add UV resistance to plastics • Also used in Sun Screen for same reason – Zinc oxide competes in this application Rutile TiO2 Hardness - 6½ S.G 4.23 Color Blood red, bluish, brownish yellow, brown-red, yellow, grayish-black, black, brown, or violet (Rutile means red) Anatase TiO2 One of the three common Forms of titanium dioxide S.G 3.79 - 3.97 Hardness 5½ - Color Brown, yellowish or reddish brown, indigo blue, black; greenish, pale lilac, grey, rarely almost colorless Brookite TiO2 One of common forms of Titanium dioxide S.G 4.08 - 4.18 Hardness 5½ - Color Brown, yellowish brown, reddish brown; dar brown to iron-black; yellowish brown to dark brown in transmitted light Relative Cost of Mineral Fillers Production Reserves of both are large Enough to be a non-issue Density Modifiers • Lightweight Applications – Use rocks that start at normal density but have a tendency to Pop or expand (a lot) when heated – Perlite • • • • Good insulator with low thermal conductivty Sound adsorbing Relatively chemically inert Fire retardant – Perlite is used • • • • • In lightweight and lightweight precast concrete Acoustic ceiling tiles Loosefill insulation As a soil conditioner (from regulatory standpoint need to check for silica content) More Lightweight Applications • Mica alters and stores lots of water • Rapid water expansion pops the mica like worms • Vermiculite has more chemically active surfaces than perlite – – – – Is used as a carrier in insecticide sprays Soaking up and containing oil Used as a soil conditioner Also found in lightweight gypsum plasters • Fire resistant plaster boards – Can be used as a loose insulator Barite and the Heavies • Barite is used in drilling mud – Its heavy, non-abrasive, and inert • It is used in heavy concretes – Concretes needing to weight down pipes in marshy areas – Good neutron adsorber so barite based concrete can reduce lead shielding at nuclear facilities • Ground form is a filler and extender – Oil based paints because it does not adsorb oil – Can be used as a tire filler to add weight Perlite Perlite is a water bearing natural glass That contains Silica, Alumina, Iron, Titanium, Calcium, Magnesium, Sodium and potasium Oxides Vermiculite (Mg,Fe,Al) 3(Al,Si) 4O 10(OH) 2·4H 2O Hardness 1½ - S.G 2.3 - 2.7 Color Brown, bronze-yellow Barite BaSO4 S.G 4.5 Hardness - 3½ Color Colourless, white, yellow, brown, grey, blue, etc.; colourless in transmitted light (also tinted yellow, brown, green, blue, etc.) Uses of Perlite Uses of Vermiculite Processing Vermiculite Separating Vermiculite from gangue Minerals is done by a variety of methods The interesting twist is Launching down a wind Tunnel The largest plates settle Out first Vermiculite Expansion Drop the flakes right through gas burners (it does not burn) 1000 to 1500 F Water in the weathered mica flashes to steam popping the flakes like pop-corn What are They Worth? Vermiculite about $50/ton Barite about $50 to $60/ton Perlite about $140 to $150/ton Production and Reserves of Vermiculite Production and Reserves of Perlite [...]... characteristics • Drilling mud uses barite for density control • Kaolin and diatomite prevent caking of ANFO • Coal mine rock dust is limestone Talc and Pyrophyllite Uses Wollastinite Uses Relative Cost of Mineral Fillers Production Reserves of both are large Enough to be a non-issue Density Modifiers • Lightweight Applications – Use rocks that start at normal density but have a tendency to Pop or expand (a... yellow, brown, grey, blue, etc.; colourless in transmitted light (also tinted yellow, brown, green, blue, etc.) Uses of Perlite Uses of Vermiculite Processing Vermiculite Separating Vermiculite from gangue Minerals is done by a variety of methods The interesting twist is Launching down a wind Tunnel The largest plates settle Out first Vermiculite Expansion Drop the flakes right through gas burners (it does
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