APYRAL® products have a very high chemical purity of at least 99.5 %. The remaining constituents consist mainly of sodium oxide, which is part of the crystal lattice and partly adhering to the APYRAL® surface in hydrated form, as well as traces of iron and silicon compounds.
Aluminium hydroxide is non-soluble in water with amphoteric characteristics. Due to the sodium oxide components, a watery APYRAL® suspension has a pH value of 8-9. This must be taken into consideration in watery or other alkali-sensitive solvents or dispersions – particularly where other additives are used, which are restricted in use to a certain pH range. In case of doubt, tests must be made for possible interactions.
In many applications APYRAL® is not only used as flame retardant, but does also fulfil a function as white pigment. Due to its whiteness, APYRAL® behaves neutral to the colouring of polymers.
The Mohs hardness of 2.5 - 3 causes no problems even in highly filled molten masses. The relatively high heat capacity cp of 1.65 J/gK at 400°K (127°C) has a beneficial effect on the dimensional stability under heat for APYRAL® filled polymers. This even has priority in some applications.
With a specific density of 2.4 g/cm3, APYRAL® is a medium-density mineral filler. As a result of the required filling levels, the density of the flame-retarded plastics is increased compared with the unfilled polymer. In total, however, APYRAL® is one of the most attractive flame retardants, even on the basis of a volume-specific cost balance.