Synthesis and evaluation of hyperbranched phenolic antioxidants of three different generations

Antioxidant-modified Boltorn(R) of 2nd, 3rd and 4th generation were synthesised. 3-(3,5-Di-tert-butyl-4-hydroxy-phenyl)-propionic acid was the active group attached to the three different hyperbranched polyesters. The syntheses were successful with high degrees of substitution. The antioxidants were evaluated in squalane and in polypropylene (PP) films using differential scanning calorimetry (DSC) to determine the oxidation induction time (OIT). They were compared to the commercial antioxidant Irganox 1010, which was added in an amount of 0.1 wt.%. All the synthesised antioxidants were superior to Irganox 1010 in squalane but did not contribute much to the stability of PP. The conclusion was drawn that the low antioxidative performance in PP is due to low mobility in combination with low solubility of the hyperbranched antioxidants. (C) 2002 Elsevier Science Ltd. All rights reserved.