The effects of heat treatment below the melting point of 3,9-bis{1,1-dimethyl-2[beta-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl}-2,4,8,10-tetraoxaspiro[5,5]-undecane (AO-80) on the thermal and dynamic mechanical properties and microstructure of chlorinated polyethylene (CPE) filled with vitrified AO-80 particles were investigated. The initial AO-80 was a complete crystal, whereas AO-80 obtained by cooling from its melting state was amorphous. The vitrified AO-80 particles could crystallize again in a CPE matrix by an annealing treatment, but this crystal was different from the initial AO-80 in the microstructure. In addition, the incorporation of CPE chains caused a dramatic increase in the modulus. As a result, the AO-80 crystal particles that contained some CPE chains acted as multifunctional crosslinks, and the CPE/AO-80 hybrid was found to be a new type of elastomer. (C) 2003 Wiley Periodicals, Inc.