Im. Elanwar et Sa. Elhenawii, PHYSICAL AND DIELECTRIC-PROPERTIES OF SOME NONIONIC SURFACTANTS, JOURNAL OF MATERIALS SCIENCE & TECHNOLOGY, 14(4), 1998, pp. 361-367
Citations number
25
Categorie Soggetti
Material Science","Metallurgy & Metallurigical Engineering
Fatty acid esters have been prepared by reacting the acid C-18 with po
lyethylene glycols having varying numbers of oxyethylene units (4 simi
lar to 88 units) by the direct esterification reaction method. Surface
and interfacial tensions are studied at various experimental conditio
ns, including, concentration, temperature, and chemical constitution o
f the surfactants. Critical micelle concentrations (CMC), surface exce
ss Gamma and residual area occupied by each surface active agent molec
ule A have been calculated using Gibb's equation. CMC values range fro
m 10 to 55x10(-5) mole/L for all studied agents, while the residual ar
ea occupied by each molecule varies from 0.6 to 1.5 nm(2) Variation of
CMC of some of these agents with temperature have been also examined
and data obtained are used to calculate the heat of micellization Delt
a H-m and the entropy change during micellization Delta S-m. Values of
Delta H-m varies from 14.63 kJ/mole to 2.717 kJ/mole depending on the
chemical constitution of the agent under consideration. The apparent
dipole moments mu of three surfactants were measured following the Hea
dstrand's method. Values of mu are 3.24, 3.14 and 3.02 D for stearates
, oleates, and linoleates adducts with polyethylene glycol (1000).