TA 99
Talc is a hydrous magnesium silicate mineral with a chemical composition of Mg3Si4O10 (OH)2. Although the composition of talc usually stays close to this generalized formula, some substitution occurs. Small amounts of Al or Ti can substitute for Si; small amounts of Fe, Mn, and Al can substitute for Mg; and, very small amounts of Ca can substitute for Mg.
When large amounts of Fe substitute for Mg, the mineral is known as minnesotaite. When large amounts of Al substitute for Mg, the mineral is known as pyrophyllite.
Talc is usually green, white, gray, brown, or colorless. It is a translucent mineral with a pearly luster. It is the softest known mineral and is assigned a hardness of 1 on the Mohs Hardness scale.
Talc is a monoclinic mineral with a sheet structure similar to the micas. Talc has perfect cleavage that follows planes between the weakly bonded sheets. These sheets are held together only by van der Waals bonds, which allows them to slip past one another easily. This characteristic is responsible for talc’s extreme softness, its greasy, soapy feel, and its value as a high-temperature lubricant.
Uses of Talc
Most people use products made from talc every day; however, they don’t realize that talc is in the product or the special role that it plays.
Talc in Plastics
It is mainly used as filler. The platy shape of talc particles can increase the stiffness of products such as polypropylene, vinyl, polyethylene, nylon, and polyester. It can also increase the heat resistance of these products and reduce shrinkage. Where the plastic is extruded in the manufacturing process, talc’s very low hardness produces less abrasion on equipment than harder mineral fillers.
Talc in Ceramics
Talc is used in the manufacturing of ceramics products such as bathroom fixtures, ceramic tile, pottery, and dinnerware. When used as filler in ceramics, talc can improve the firing characteristics of the greenware and the strength of the finished product.
Talc in Paint
Most paints are suspensions of mineral particles in a liquid. The liquid portion of the paint facilitates application , but after the liquid evaporates, the mineral particles remain on the wall. Talc is used as an extender and filler in paints. The platy shape of talc particles improves the suspension of solids in the can and helps the liquid paint adhere to a wall without sagging. Powdered talc is a very bright white colour. This makes talc excellent filler in paint because it simultaneously serves to whiten and brighten the paint. Talc’s low hardness is valued because it causes less abrasion damage on spray nozzles and other equipment when paint is applied.
Talc in Paper
Most papers are made from a pulp of organic fibers. This pulp is made from wood, rags, and other organic materials. Finely ground mineral matter is added to the pulp to serve as filler. When the pulp is rolled into thin sheets, the mineral matter fills spaces between the pulp fibers, resulting in a paper with a much smoother writing surface. Talc as a mineral filler can improve the opacity, brightness, and whiteness of the paper. Talc also can also improve the paper’s ability to absorb ink.
Talc in Cosmetics and Antiperspirants
Finely ground talc is used as the powder base of many cosmetic products. The tiny platelets of a talc powder readily adhere to the skin but can be washed off easily. Talc’s softness allows it to be applied and removed without causing skin abrasion.
Talc also has the ability to absorb oils and perspiration produced by human skin. The ability of talc to absorb moisture, absorb odor, adhere to the skin, serve as a lubricant, and produce an astringent effect in contact with human skin make it an important ingredient in many antiperspirants.
Talc as a Dimension Stone
Finely ground talc is used as the powder base of many cosmetic products. The tiny platelets of a talc powder readily adhere to the skin but can be washed off easily. Talc’s softness allows it to be applied and removed without causing skin abrasion.
Talc also has the ability to absorb oils and perspiration produced by human skin. The ability of talc to absorb moisture, absorb odor, adhere to the skin, serve as a lubricant, and produce an astringent effect in contact with human skin make it an important ingredient in many antiperspirants.
