Bis(2,4-di-tert-butylphenyl) pentaerythritol diphosphite is an organophosphite used as a polymer stabilizer in plastics. Like other phosphite antioxidants it primarily acts to remove hydroperoxides and is typically used in combination with hindered phenolic antioxidants such as pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamate).
It is formed by a reaction between phosphorus trichloride, pentaerythritol and 2,4-di-tert-butylphenol. The poor solubility of pentererythritol can be an issue and non-nuncleophilic amines are often used to promote the reaction.
Compared to tris(2,4-di-tert-butylphenyl)phosphite (a common phosphite antioxidant) it has higher activity but lower stability against hydrolysis. Trace levels of amine bases are often added to commercial material to slow hydrolysis and increase storage life. Its crystal structure has been determined. It is comparable with a wide range of plastics including polyolefins, engineering plastics and polyurethane fibers. It is an approved food contact material in the US.