COADSORPTION OF CATIONIC-NONIONIC SURFACTANT MIXTURES ON POLYTETRA FLUOROETHYLENE (PTFE) SURFACE

Adsorption from aqueous solutions of mixtures of surfactants of cetyl trimethyl ammonium bromide (CTAB) and nonyl phenyl ethoxylates (NP - n ) (n = 13, 20, 30) on PTFE was studied in a wide concentration range. The adsorption of CTAB was enhanced by the presence of nonionic surfac tants and vice versa in the pre-CMC region due to chain-chain interact ions. The decrease in adsorption level of CTAB with an increase in mol e fraction of nonionic surfactants in the region above the CMC has bee n attributed to the decrease in monomer concentration due to mixed mic ellization with nonionic surfactants. In the case of adsorption of non ionic surfactants from the mixtures, adsorption increases in the prese nce of CTAB. It was also observed that among the various binary system s, maximum adsorption was observed with CTAB and NP-13 system, This wa s attributed to the formation of the most compact arrangement of surfa ctants in the clusters formed at the solid/liquid interface, Zeta pote ntial studies carried out on these systems compliment the adsorption r esults. (C) 1996 Academic Press, Inc.