Hydrotalcite, the English name is Hydrotalcite, or HT for short. At first glance, it’s hard to imagine what it looks like when you hear this name. There are even many people who have never heard of this thing, let alone how it is related to our lives.
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Hydrotalcite was first found in natural ores Found in the natural state of hydrotalcite, commonly known as brucite, it has a structure similar to brucite Mg(OH)2. In Mg(OH)2, Mg is surrounded by octahedral ligands of oxygen atoms in the form of hydroxyl groups. The octahedrons share edges and are connected to each other, and are continuously tiled to form a layered structure.
The chemical composition of hydrotalcite can be expressed as:
Among them, M2+ and M3+ represent divalent and trivalent metal cations respectively, An- represents an interlayer anion with a valence of -n, and x is M3+ The number of moles, m is the number of hydration water. The size, shape and spatial orientation of guest molecules or ions can all affect the layered structure of hydrotalcite.
In brucite, part of Mg2+ It can be replaced by Al3+ with a similar radius to form a layered structure composed of Mg-Al hydroxyl compound octahedron. In order to ensure that the charge of the entire hydrotalcite structure is balanced, there are exchangeable anions, such as CO32- in natural hydrotalcite, and some water molecules, which are connected to the laminate through electrostatic attraction, hydrogen bonding and van der Waals forces.
There are many hydrotalcites Main applications
1. Hydrotalcite has a structure and composition similar to magnesium hydroxide and aluminum hydroxide. When it is thermally decomposed, it releases a large amount of water and carbon dioxide, and absorbs a large amount of heat. , can reduce the temperature of the combustion system; the algae vapor and carbon dioxide gas released by decomposition can dilute and block flammable gases; the magnesium aluminum oxide generated by thermal decomposition and the carbide formed when the polymer material is burned form a protective film on the surface of the material , thus blocking further intrusion of oxygen and also having a flame retardant effect.
2. The solid product after the decomposition of hydrotalcite particles has a large specific surface area and strong alkalinity, and can absorb materials in time The acidic gases and smoke released during thermal decomposition are converted into corresponding compounds, thereby suppressing and eliminating smoke. Therefore, hydrotalcite is a new type of smoke-eliminating non-toxic halogen-free flame retardant. Its flame retardant performance is significantly better than aluminum hydroxide and magnesium hydroxide, and it has the advantages of both.
3. Hydrotalcite is a non-toxic heat-stable material. It can be used as an efficient, non-toxic and cheap heat stabilizer for polyvinyl chloride. It can effectively absorb the HCI produced by the decomposition of PV calcium carbonate and magnesium C during processing and use, and improve the processing conditions and heat stabilizer of PVC. It can be used as a heat stabilizer together with organotin or lead-zinc, or with other additives to further improve the thermal stability of PVC.
4. Mixing hydrotalcite with other preparations can not only improve the heat resistance of polymer materials, but also improve their other properties. Such as mechanical strength, anti-aging temperature, product surface brightness, insulation performance, antistatic performance, anti-UV performance, etc. Hydrotalcite also has good thermal insulation properties, promotes the absorption of infrared rays by PVC agricultural films, and improves the thermal insulation of home films.
5. Heat stabilizer for PVC, UV absorber in agricultural PE, PVC, and EVA: acid acceptor, stabilizer for organohalogen flame retardant (auxiliary flame retardant): It has excellent thermal stability for PVC and has non-toxic raw materials – high transparency – high dispersibility – the salt will not detach at high temperatures, so it will not reduce the insulating packaging of PVC.
6. Used as a multifunctional filling improver for flame retardant, stable, insulating, coloring, UV resistant and other polymer materials such as plastics, rubber and chemical fibers.
7. Used as daily chemical raw materials for dyes, coatings, paints, inks, and cosmetics.
8. Used as fabric dyeing wastewater treatment agent, radioactive wastewater treatment agent, and pollution purification flocculant.
9. Used as chemical catalyst carrier and catalyst.
10. Used as improver and intermediate for various materials.
11. Due to its special chemical composition, it has a significant inhibitory effect on the growth of various microorganisms and fungi, so it has bactericidal and anti-mold properties.
Hydrotalcite has many functions and looks like a “universal stone”. Hydrotalcite plays a very important role in chemical production. It can be used as a chemical raw material and can also be used as a catalyst to catalyze autonomous catalytic effects. In the biological field, hydrotalcite can also be used to kill bacteria and inhibit the growth of many microorganisms. Researchers in both the chemical and biological fields are still studying and exploring the functions of hydrotalcite, hoping that more functions of hydrotalcite can be discovered.
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