Hydrolytic stability of phenolic antioxidants and its effect on their performance in high-density polyethylene

Comparative experiments were carried out with two hindered phenolic antioxidants of different chemical structures to determine their hydrolytic stability and performance in the presence of extractive media. Hostanox O10(R) (HO10) and Hostanox O3(R) (HO3) were hydrolysed in solution and the reaction products were identified by HPLC-ESI-MS analysis. The efficiency of the two additives was checked by standard multiple extrusion test in HDPE. Samples were stored in water for a year to determine their hydrolytic stability under more practical conditions. The results proved that Hostanox O10 is a better processing stabilizer than HO3, while the latter performs much better under the effect of extractive media. Besides hydrolysis other reactions, mainly the splitting off one or more alkyl groups from the original molecule, may also take place during storage at 80 degreesC in water, which may also lead to a decrease in stabilizer efficiency. The results clearly prove that high efficiency in a short-term laboratory test is not the only criterion to rank a stabilizer. Under long term conditions such as storage in an extractive environment HO3 outperforms HO10. (C) 2003 Elsevier Ltd. All rights reserved.