| Surfactants are widely used in the fields of both traditional and high-technology industry. In general, most investigations of surfactants are carried out in neutral aqueous solutions. However, surfactants are also extensively used in alkaline solutions, for instance, the process of pretreatment for cotton fabrics, mercerization, enhanced oil recovery, paperindustry, and wastepaper deinking are usually carried out in aqueous caustic solutions with varied concentration of NaOH. The penetrating agents are used in these procedures. Considering a fact that surfactants are also widely applied in alkaline solutions, in the present work, two types of sodium phosphate surfactants, sodium ethylhexyl phosphate (SEP), sodium ethylhexyl polyoxyethylene phosphate (SEPOP) and their mixtures(SEP-SEPOP) were employed as alkali resistant penetrating agents, and the surface activity, wetting permeability, foaming power and the aggregation of the surfactants aqueous caustic solutions were studied, the microstructure of fabric treated by the surfactant-aqueous caustic solutions were also measured.1. The alkaline resistance property of the surfactants were measured by GB/T 5556-2003 standard method. The results showed that they all showed good resistance to strong bases. SEP possessed the highest alkaline resistance ability and alkaline resistance ability in 0.5-6.0 mol/L and 6.5-7.0 mol/L NaOH solutions respectively. SEPOP and their mixtures also possessed the highest alkaline resistance ability and alkaline resistance ability in 0.5-4.0 mol/L and 4.5-7.0 mol/L NaOH solutions respectively.2. The surface tension of the surfactants were measured by surface tension meter(Kruss-DSA100,Germany). The results showed that the surfactants had outstanding surfactivities and can reduce theSurface tension of NaOH solutions to much lower values than of aqueous solutions. The cmc and the lowest surface tension of the three surfactant aqueous solutions were 2* 10-2 mol/L,1*10-2 mol/L, 1*10-2 mol/L and 33.2mN/m,34.0mN/m, 33.8mN/m,respectively. The cmc and the lowest surface tension of the three surfactant aqueous caustic solutions were 8*10-3 mol/L,8*10-3 mol/L and 5*10-3 mol/L and 27.8 mN/m,29.0 mN/m,28.2 mN/m, respectively.3. The wetting permeability of the surfactants were investigated by measuring immersion time, sinking time and capillary effects of cotton fabrics by GB/T5558-1999, HG/T 2575-1994 or DIN EN 1772-2000, FZ/T 01071-2008 or DIN 53924-1997. The results showed that all the three surfactants showed excellent wetting permeability in NaOH solutions much more than in surfactant aqueous solutions. And that, the complex surfactant exhibited better wetting permeability in NaOH solutions in comparison with corresponding single components employed.4. The aggregation behavior of the surfactant in NaOH solutions and aqueous solutions by employing dynamic light scattering (DLS) technique. The results showed that the micellization concentration of the surfactants aqueous alkali were lower than the surfactant aqueous solutions. The micellization concentration of the three surfactants aqueous solutions were 2*10-2mol/L, 1*10-2mol/L,1*10-2 mol/L,the corresponding aggregation size were 4.8nm,3.6nm,4.2nm。And that In aqueous alkali cases, particularly where the surfactant concentration were more than 8*10-3mol/L, the aggregation size changed from 0.6 nm to 13.5nm, It has been suggested that this indicates change in the micellar structure.5. The foaming power of the surfactants was measured by Modified Ross-Miles method. The results showed that the surfactants’ foaming power in NaOH solutions showed lower foaming power and that their foaming power were lower than in aqueous solutions.6. The effect of the surfactants-NaOH solutions on the surface microstructure of cotton fibers were investigated by scanning electron microscopy (SEM). The results showed that the cotton fabrics showed much more lubricous and full in surfactants-aqueous alkali than in surfactants-aqueous solutions. SEM images also indicate that the cotton fibers were quickly wetted by alkaline surfactant solutions without shrinking effect.7. Two kinds of textile auxiliaries were empoldered, which have been used in the factories. The results indicated that they showed good properties for practice. |
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