An important factor influencing the stability of colloidal suspension is zeta potential (zeta-potential) on the surface of particles. In this work, zeta-potential of TiO2 particles in ethylene glycol (EG) with various additives for poly(ethyleneterephthalate) (PET) polymerization, such as metallic salts, phosphoric acid and alkyl phosphates, were investigated by electrophoretic mobility method. The dispersion stability of TiO2/EG suspension was influenced by decrease in the absolute value of the zeta-potential by the addition of metal acetates as well as phosphates. The addition of triethylamine (TEA) in the TiO2/EG suspension restrained the change of zeta-potential from negative to positive, which resulted from phosphoric acid. The molar ratio of phosphoric acid to an acetate was found to have an influence on the dispersion ability of TEA in TiO2/EG suspension. Effect of metallic salts, phosphoric acid and TEA on the stability of TiO2/EG suspension was studied in the actual polymerization of PET. It was proved that the addition of TEA is highly effective for the dispersion of TiO2 particles in PET, even in the presence of metallic salts, phosphoric acid and its alkyl phosphates. (C) Koninklijke Brill NV, Leiden, 2010