Talc filler surface characteristics

Commercial talc is composed primarily of the mineral talc, a sheet sihcate, but may contain related sheet silicates such as chlorite and serpentine, plus prismatic tremolite, anthophyllite, and carbonates such as magnesite, dolomite, and calcite. Talc particles are characteristically platy in morphology and are oleophihc/hydrophobic they are wetted by oil instead of water. Talc s reinforcing and pigmenting properties, together with good color, make it desirable as a functional filler in both aqueous and nonaqueous appHcations. For nonaqueous uses its naturally good matrix compatibility can be further enhanced by surface treatment. 

If we exclude the case of the Italian talc, all the other distribution functions are bimodal and present a main peak at low energy around 17 kj/mole characteristic for the basal surface and a very weak peak at the highest energy at 27 kj/mole corresponding to lateral surfaces. It demonstrates that industrial talcs having low specific surface area exhibit mainly basal surfaces and that the difference in behaviour, as a specific filler for polyolefines origin certainly from other more macroscopic factors such as shape and size of... 

Particulate-filled thermoplastic polyolefins are used in vehicle applications. Talc, calcium carbonate, and kaolin are typical fillers. Fillers do not change the transition characteristics of the plastic. Fillers increase the temperature-dependent elastic moduli of the plastics, increasing the forces required to form the plastics in the plateau-temperature regions. Matched-mold thermoforming is necessary if the product cannot be formed using a conventional pressme box over a single-surface mold. 

Molybdenum compounds are regarded as the standard for low-smoke formulations, especially ammonium octamolybdates (AOM) for vinyl applications. Many studies claim that molybdates work in the solid phase, as most of the molybdenum is found in the char residue. Molybdates are said to reduce smoke by catalyzing the formation of trans polymer fragments so that it cannot form aromatic species, characteristic of soot. One producer uses an inert filler (talc) as the core support media onto which a zinc molybdate layer is precipitated on the surface. This coated core stmcture effectively provides smoke suppression at a lower manufacturing cost than neat molybdates. 

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