Talc Powder & Ground Calcium Carbonate

Talc Powder

Talc, in its pure form, is a hydrated magnesium silicate and has the chemical formula 3MgO.4SiO2·3H2O. The exact composition of talc depends on the location of mining, since talc from different mining locations may contain significantly different proportions of MgO, SiO2, and H2O. Talc has a layered platey structure consisting of a magnesium hydroxide layer sandwiched between two silica layers. These three layers are held together by weak chemical bonds of Van der Waals type and, therefore, they can slide past each other relatively easily when subjected to shearing action.

Talc is the softest mineral filler used in the plastics industry. It has high resistivity, low gas permeability, low abrasiveness, and high lubricity. All of these qualities are attributed to talc׳s platey structure. The aspect ratio of talc fillers is as high as 20:1. Talc with a high aspect ratio has shown reinforcement ability in high-density polyethylene, polypropylene, and other thermoplastics, especially when they are treated with coupling agents to promote better bonding with these polymers.

Ground Calcium Carbonate (GCC)

Ground Calcium Carbonate (CaCO3) is one of the most popular mineral fillers used in the plastics industry. It is widely available around the world, easy to grind or reduce to a specific particle size, compatible with a wide range of polymer resins and economical. As an additive in plastic compounds, CaCO3 helps decrease surface energy and provides opacity and surface gloss, which improves surface finish. In addition, when the particle size is carefully controlled, CaCO3 helps increase both impact strength and flexural modulus (stiffness).

Calcium carbonate may be used with a myriad of thermoplastic resins. Polypropylene compounds are often filled with calcium carbonate to increase rigidity, an important requirement for operations at high temperatures. In PVC, calcium carbonate is used with flexible compounds such as tubing, wire and cable insulation, latex gloves, trash bags and in rigid compounds such as extruded pipes, conduits and window profiles.