The thermal stability of vulcanizates of low-density polyethylene (LDPE), poly(dimethyl siloxane) (PDMS) rubber, and their blends was studied by nonisothermal thermogravimetry. Four ethylene copolymers [ethylene methyl acrylate (EMA), ethylene vinyl acetate, ethylene acrylic acid, and a zinc-salt-based ionomer (Lotek 4200)] were used as compatibilizers for the blend systems. The thermograms and derivatograms of the blends showed that thermal degradation took place in two stages, whereas those for the base polymers showed single-stage degradation. Kinetic studies of the blends and pure components showed that the degradation followed first-order reaction kinetics. The activation energy at 10% degradation was determined with the Freeman-Carroll method and was at a maximum (42.34 kcal/mol) for the 25:75 LDPE/PDMS rubber blend. The half-life at 200degreesC was evaluated by the Flynn-Wall method and was at a maximum (812.5 days) for the same blend. Out of four compatibilizers, EMA showed the maximum activation energy (34.25 kcal/mol) for degradation and a maximum half-life (695.3 days), indicating that EMA was the best compatibilizer for the blend system. (C) 2003 Wiley Periodicals, Inc.