Surface and thermodynamic parameters of polymeric surfactants from recycled poly(ethylene terephthalate)

Poly(ethylene terephthalate) waste was recycled to oligomers in the presence of diethanolamine and manganese acetate as a catalyst. The oligomers produced were reacted with stearic acid and poly(ethylene glycol) with different number average molecular weights of 400, 1000 and 4000 g mol −1 to produce nonionic polymeric surfactants having different hydrophile–hydrophobe balances. The surface tension, critical micelle concentration and surface activities were determined at different temperatures. Surface parameters such as surface excess concentration (Γ max ), the area per molecule at interface ( A min ) and the effectiveness of surface tension reduction (Π CMC ) were determined from the adsorption isotherms of the prepared surfactants. Some thermodynamic data for the adsorption process were calculated and are discussed.