Hydrolysis and stabilization performance of bis(2,4-di-t-butylphenyl)pentaerythrityl diphosphite in polypropylene

The mechanism of hydrolysis under the conditions of long-term storage and the effect on stabilization efficiency of bis(2,4-di-t-butylphenyl)pentaerythrityl diphosphite (PA) was studied. Hydrolysis of P-1 under air in normal humidity begins by the cleavage of P---O_phenol bond, and both 2,4-di-t-butylphenols (DTBP) from one P-1 molecule are preferably released.

A series of samples hydrolyzed to different degrees was tested both alone and in blends with tetrakis (methylene 3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate) methane (AO-1) as processing and long-term antioxidants in polypropylene. P-1 was found to perform as an efficient processing antioxidant even in the absence of phenolics. Hydrolyzed P-1, characterized by the presence of 7% of free DTBP released, exhibited an improved performance. P-1 subjected to hydrolysis up to 48% was shown to retain good stabilization efficiency.