The thermal degradation of waste poly(methyl methacrylate) (PMMA) in the presence of ferric sulfate, cupric sulfate, aluminum sulfate, magnesium sulfate, and barium sulfate was studied by using thermogravimetric analysis (TGA) in air atmosphere. The values of apparent activation energies (E-a) calculated by Flynn-Wall-Ozawa method were found to be in the order of PMMA+Fe-2(SO4)(3)< PMMA + Al-2(SO4)(3) < PMMA + MgSO4 < PMMA + CuSO4 < PMMA + BaSO4 < PMMA. The mechanism of catalytic degradation of PMMA in presence of the sulfates was discussed and the results showed that the catalytic effects of sulfates have a relationship with the acidity of their respective metal ions. (C) 2005 Elsevier B.V. All rights reserved.