The chemical formula of the ideal component of talc is Mg 3 [Si 4 O 10 ](OH) 2 or 3MgO•4SiO 2 •H 2 O, MgO 31.72%, SiO 2  63.52%, H 2 O 4.76%. Talc is one of the softest varieties of known minerals and gives a sense of lubrication. The talc has a Mohs hardness of 1, and the calcite has a Mohs hardness of 3. The talc product supplied by the product is harder than pure talc because it contains mineral impurities such as calcite and tremolite.
Second, the physical properties of talc
There are many kinds of unprocessed talc, such as white, gray, yellow, blue, light green, pink, brown, and the like. After pulverization, various talc become a gray to white powder with different solid luster.
Due to the sheet-like nature of the special configuration of talc, after being uniformly distributed in the resin, the metal supporting material added to the cement article has excellent mechanical properties. It is considered to be a reinforcing material, which is different from other granular minerals.
Third, the main production area of ​​talc
At present, the proven talc powder in China is mainly distributed in Guilin, Guangxi, Qixia, Shandong, Jiaodong Peninsula, Laizhou, Haicheng, Liaoning. Due to different mineral sources, the performance structure of talc is different. After comparative application tests, Guangxi talc has good transparency and excellent processing performance. The talc powder of Shandong Jiaozhou Peninsula has a low content of SiO 2 and good whiteness, but poor transparency. The talcum powder in Haicheng, Liaoning Province is rich in mineral resources, moderate in price and variety. However, there are many varieties of talcum powder, different mineral sources, and different processing techniques. When selecting talc powder, it is necessary to select talc powder with different specifications and different indexes according to different uses. The SiO 2 content of the talc has an effect on the properties of the talc (see table below).
SiO 2 content | Price and performance |
40% or less | Low price, fairness, poor transparency and poor mechanical properties |
40% to 50% | Low price, good whiteness, poor transparency, general mechanical properties |
50% to 55% | Moderate price, good whiteness, good transparency and good mechanical properties |
55% to 60% | High price, good whiteness, good transparency and good mechanical properties |
More than 60% | High price, less mineral source, very good whiteness, good transparency and good mechanical properties |
Fourth, the role of talc in plastics
Talc powder is an important inorganic material for plastic filling and modification. It has been widely used in polypropylene modification at home and abroad. It is mainly used for the production of auto parts, front and rear bumpers, instrument panel panels, interior decorative panels, etc. Industry, such as washing machine parts, air conditioning parts, TV back shells, electric heater shells and various household appliances shells.
Talc is inexpensive and suitable for use as an extender, while the talc has a high sheet-like configuration or aspect ratio (the ratio of the average diameter of the particles to its thickness) which is suitable as a reinforcing agent (to improve the mechanical properties of the composite). Commercial talc for plastics is a finely comminuted product in a sheet configuration.
Talc is widely used in plastics and its characteristics are as follows:
1 Particle size and shape Most of the talc products used as fillers are very fine. The crystal shape of the talc may be in the form of a sheet (layer), a leaf (broadleaf), a needle or a block. Most of the talc particles produced in China have a sheet-like structure. The ratio of the average diameter of the flaky particles to their thickness is called the aspect ratio, which is an important indicator for measuring talc.
2 Surface properties Talc exhibits different surface properties depending on its source. Product fineness affects specific surface area and oil absorption. Other factors that affect these properties are surface roughness, particle shape, and pore volume. In general, talc has a large specific surface area due to the flaky configuration of talc.
3 Electrical and thermal properties Talc is an electrical non-conductor that can be used to produce high-frequency electrical insulation materials. The talc is heated to a high temperature of 900 ° C and is still stable. Talc has low thermal conductivity and high thermal shock resistance. Under heating conditions, the talc loses some of its structural water without changing its optical or crystalline properties. When the temperature exceeds 800 ° C, the talc loses its bound crystal water and decomposes into an enstatite by an endothermic reaction.
4 Optical Properties Pure talc has three refractive indices, X = 1.539, Y = 1.589, Z = 1.589, which have small and variable optical axis angles. Therefore, when talc is used in agricultural greenhouse film, the direction of sunlight can be changed, and direct light is converted into scattered light to improve the heat preservation effect of the film.
Introduction to Melt Composite Technology: Polymers filled with flaky talc exhibit higher stiffness and creep resistance than polymers filled with particulate fillers such as calcium carbonate, both at room temperature and at elevated temperatures. In order to maximize the above properties, a special melt compounding technique is actually applied to incorporate a large amount of filled talc into the polymer. The special compounding of fine talc particles requires the application of all special melt compounding (wiping, bending, stretching, painting, pressing, shearing) to fully wet the talc particles by the molten polymer and achieve high dispersion of talc particles. Thus forming a uniform composite. To this end, a batch or continuous melt mixing device must be used to produce a resin granule dispersed with filler. This filled premix can then be processed into an end product by injection, molding or extrusion equipment.
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