Fine Aluminum Hydroxide (Fine 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 non-halogen flame retardant (NHFR) used in various end applications including cable compounds.
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 non-halogen flame-retardant (NHFR) wire and cable (W&C), one of ATH’s largest markets, fine precipitated ATH(Fine Aluminum Hydroxide) is used for sheathing and insulation.
The NHFR 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.
Polyvinyl chloride (PVC) is a low cost polymer material, and it is easy to process.
However, when it burns, it produces a lot of smoke, decomposes toxic and corrosive gases, suffocating, and is the main cause of death in fires. The application of fine aluminum hydroxide to PVC effectively overcomes the above shortcomings.
Fine aluminum hydroxide surface-treated with coupling agent can also significantly reduce the smoke density of plastics, and the mechanical properties of the material are just a little reduced. It is an excellent flame retardant and smoke suppressant.
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