Synonym: Azobisisobutyronitrile 

CAS No.: 78-67-1 

UN No.: 3234 

Formula: C₈H₁₂N₄ 

Molecular Weight: 164.21

2,2'-Azobis(2-methylpropionitrile), commonly abbreviated as AIBN, is an oil-soluble azo-type free radical initiator, widely used in polymer industry and organic synthesis. It appears as white crystalline powder under normal conditions, melting at 102–104 °C. AIBN is insoluble in water, soluble in organic solvents such as toluene, ethanol, ether and acetone. 

When heated above its decomposition temperature, AIBN undergoes homolysis of the azo group (-N=N-), releasing nitrogen gas and forming isobutyronitrile free radicals to trigger radical polymerization. Its 10-hour half-life temperature is 65 °C in toluene. Compared with peroxide initiators, AIBN will not produce oxygen-containing by-products and causes less yellowing of polymers, which is a prominent advantage for acrylic products requiring good color stability.

Main applications:

• Initiator for bulk, solution, suspension polymerization of monomers like acrylate, methacrylate, styrene, vinyl chloride and acrylonitrile;
• Used in manufacturing PMMA cast sheets, acrylic fiber, adhesive, super absorbent polymer and flocculant;
• Can be applied as a foaming agent for plastics, and also used as radical source in fine chemical synthesis.

Hazard & Transport Note: AIBN is Class 4.1 self-reactive solid. It is heat-sensitive, may decompose violently under high temperature, friction or impact. It is harmful if swallowed or inhaled. Keep stored below 25 °C, away from heat, light, oxidants and fire sources during storage and transportation