Aluminum Hydroxide, also known as Aluminum Trihydrate (ATH) is an inorganic white fine crystal, non-hygroscopic powder. Its solubility in water and organic solvents is very low. By volume, ATH is the largest flame retardant (FR) used in various end applications.
The working principle is based on the thermal decomposition of aluminum hydroxide into aluminum oxide and water (vapor). This endothermic reaction starts at about 200°C and consumes energy from the ignition source. The generated water vapor cools the polymer surface and dilutes the concentration of combustible gases in the surrounding environment.
The remaining metal oxide residue has a relatively high inner surface, in which soot particles (respectively polycyclic aromatic hydrocarbons) are adsorbed so that ATH is also a smoke suppressant. The oxide layer serves as a barrier layer to protect the polymer from further decomposition.
The median particle size (D50) of ATH commercially available is 0.5 – 80 µm. In the halogen-free flame-retardant (HFFR) wire and cable (W&C), one of ATH’s largest markets, finely precipitated ATH is used for sheathing and insulation.
The HFFR compound is based on a mixture of EVA (poly(ethylene-vinyl acetate)) and LLDPE (linear low-density polyethylene). In plasticized PVC, finely precipitated ATH is used as a flame retardant and smoke suppressant. Low-smoke flame-retardant (LSFR) cable.
Another very important end application is insulation foam made from PVC/NBR blends. These elastomers must also meet strict fire protection requirements, especially when used for thermal insulation and plumbing in multi-story storage buildings. Other applications are PVC-based flooring.
The Coarser ATH type produced by grinding is widely used in thermosetting applications. Cast resin and glass fiber reinforced products such as BMC (bulk molding compound) and SMC (sheet molding compound) are processed in electrical and electronic equipment and construction applications.
Introduction of Zibo Pengfeng fine Aluminum Hydroxide: