As a filler and flame retardant in plastics, rubber and branches, aluminum hydroxide has a wide range of raw materials, low price, and no corrosive gas after thermal decomposition. It is the most environmentally friendly halogen-free flame retardant. The application of aluminum hydroxide to plastics not only improves the UV resistance, dielectric properties and arc resistance of the material, but also improves the controllability of the material shrinkage, etc., but the decomposition temperature of aluminum hydroxide is low (180). °C~200°C begins to decompose). It is easily decomposed by thermal decomposition during the mixing process with organic polymer materials to produce bubbles, which affects the mechanical properties and appearance of the product. Therefore, it is usually only used as a flame retardant at low processing temperatures. In the material, the application range of aluminum hydroxide is limited, and in addition, the low processing temperature affects the production efficiency of the extrusion equipment and the surface smoothness of the product.
In order to improve the processing properties between aluminum hydroxide flame retardants and organic polymer materials, many methods have been developed to improve the thermal stability of aluminum hydroxide, which can be mainly divided into coupling agent modification, hydrothermal phase inversion, surface Partial dehydration, high purification and ultra-fine refinement, and surface coating modification.
The surface of the aluminum hydroxide is modified by a silane or a titanate coupling agent. When the amount of the coupling agent is high, the thermal stability of the aluminum hydroxide can be improved, but the production cost of the process is expensive due to the high coupling agent. High, and the thermal stability of the modified product is not significantly increased.
Compared with gibbsite-type aluminum hydroxide, boehmite has a high decomposition temperature, so by hydrothermal treatment, the conversion of aluminum hydroxide to boehmite can greatly improve the alumina hydrate. Thermal stability. The prepared ultrafine aluminum hydroxide is chemically modified in a hydrothermal environment to convert most of the aluminum hydroxide into boehmite. The initial thermal decomposition temperature of the modified material can reach 340 ° C, but the hydrothermal reaction The equipment requirements are high, and the decomposition heat absorption value of boehmite is much smaller than the decomposition heat of gibbsite, thereby reducing the flame retardancy of aluminum hydroxide.