Tuesday, 4 November 2014

Itac uses Antimony

Elizabeth Henderson
Product Development Manager

This month we stay in Group 5 of the periodic table, skipping down from phosphorus over arsenic and landing on antimony. The first known application of antimony in the coatings industry was as make-up. Antimony’s naturally occurring compound black stibnite (Sb2S3) was used as eyeliner by the vain in ancient Egypt, but as antimony is poisonous its use has been discontinued. ‘Tartar emetic’ (antimony potassium tartrate) was formerly used as an anti-helminthic, which acted by poisoning intestinal worms. Antimony metal exists in only one crystal form viz trigonal crystals. Antimony is found as the metal in Finland, but most of the world’s current supply is mined as stibnite in China.
Itac uses antimony by incorporating antimony trioxide, Sb2O3, in the fire resistant coatings we make for textiles and films.  It acts in synergy with chlorine-containing organic compounds to form free radicals in the flames, which quench combustion. In addition to this, the antimony promotes the formation of a carbon-based char on the surface of the burning material, which prevents continuing vapourisation of the fuel. Antimony oxide can also be incorporated in plastics to improve their fire performance.
Antimony played a big part in the advance of printing. In common with cast iron and water, the liquid form is denser than the solid at temperatures immediately above the freezing point. This implies that when poured into a mould it will expand into the crevices as it sets, forming a perfect cast of the void. Gutenberg exploited this property of antimony and developed an alloy of tin, lead and antimony which had the ideal hardness, smoothness and sharpness of edge for making type for printing presses. A similar material was formerly used for making typewriter keys.
Because of its nature as a semiconductor, antimony has many more modern applications than in simple pesticides and letterpress. It can be used as a Hall Effect sensor for measuring electric current and magnetic fields. It is also used to strengthen lead electrodes in vehicle batteries – pure lead is very soft and would not withstand vibration in an engine cavity without help. A major source of antimony for industrial applications is recycled vehicle batteries. An alloy of antimony with germanium and tellurium (Ge2Sb2Te5) has recently been patented for use in a nanodimensional flexible screen which can display an image less than a tenth of a millimetre in diameter.