a series of composites was prepared using chatter-machined al and cu fillers, and various matrix polymers (nylon 12, ppo, pc, ps, abs and hdpe) to provide shielding materials for electromagnetic interference (emi). the thermal stability of the shielding function was examined by the changes in electrical conductivity and shielding effectiveness to emi of the composites during thermal treatment at 80 $degree$ c in air. the results obtained were as follows. the shielding function was generated at 15 vol filler concentration for both al and cu series, but at 5 vol it was observed only in cu series. the thermal stability of the function of the composites was strongly affected by the matrix polymers and its order was found to be as follows: nylon 12 $greater than$ ppo $greater than$ ps $greater than$ abs $greater than$ pc $greater than$ hdpe some surface treatment of the fillers greatly improved the thermal stability of the function. on the basis of the results obtained and the physical properties of each component, the effects of the matrix polymers and surface treatment of the fillers on the thermal stability of the function of the composites are discussed. (author abstract) 18 refs