Polypropylen (PP), das 0,5 Gew.-% des 14C-markierten Antioxydans 1,3,5-Trimethyl-2,4,6-tris-(3,5-di-tert.-butyl-4-hydroxybenzyl-~~C)-benzol (I-14C) Polypropylene (PP) containing 0.5 wt.-yo of the W-labelled antioxydant 1,3,5-trimethyl-2,4,6-tris-(3,5-di-tert.-butyl-4-hydroxy-benzyl-~~C)benzene (I-14C) was kneaded for 50 min in the presence of air a t 200 "C and then exhaustingly extracted with chloroform. The loss of radioactivity of the PP during the thermal-oxidative treatment was found to amount to ca. 4% only; in contrast to this, we found a residual radioactivity of ca. 39% in the extracted PP; calculated on the radioactivity of the heat-treated PP this is 41 yo.