substituted ethylene diamine. They are notable as having negligible irritancy and as being corrosion inhibitors (see Table 2). Almost always, combinations of two or more surfactants perform better than one, both in cleaning ability and foam stability. For example, anionics clean polyester fabrics rather poorly. Non-ionics do a better job; but the combination of anionic and non-ionic surfactants works better still and most products now use this blend. Sodium lauryl sulfate (SLS) has relatively poor wetting and detergent abilities, although it foams well, even in hard water. Pairing it up with sodium lauryl sulfosuccinate enhances wetting, detergency and foam generation. SLS can produce mild eye irritation when used in shampoos, but adding an equal amount of Beta-lauryl aminopropionate (amphoteric) produces a blend that can be poured directly into an open eye without irritation and only a slight temporary sensation of fullness. The emulsion durability and foam stabilization of SLS can be improved by the inclusion of salt (as NaCl), amphoterics (over pH = 3.8), thickeners, N-polar substituted amides and several other co-products. While some believe that the separation of typical oil-in-water (o/w) emulsions can be permanently stopped by adding thickeners, this is not the case, short of creating a gel. The thickeners merely retard the particle coalescence and phase separation. In connection with the advantageous use of two or more surfactants, we can cite the generally better emulsions and larger, more stable foams produced by sodium coco sulfate (SCS) when compared with those of the individual sodium alkyl sulfates that comprise it. The surfactants produced from coconuts contain over ten longchain alkyl groups (see Table 3). The advantage of refined sodium coco sulfate (SCS) can be illustrated by the foam heights obtained by shaking a 0.25% dispersion of various sodium alkyl sulfates in both distilled water and “hard” water containing 300ppm of calcium (see Table 4). June 2017 Spray 35 Table 3. ALKYL GROUPS IN COCONUT OIL (AVERAGE)* NAME NUMBER OF CARBON ATOMS PER CENT Capric 9 Lauric 11 53 Myristic 13 21 Palmitic 15 11 Stearic 1 4 Oleic 17 6 Arachidic, Behenic, Elaidic 17-21 3 * Ratios can vary widely according to palm tree growing conditions. Table 4. FOAM HEIGHTS BY SHAKING SODIUM ALKYL SULFATES IN WATER (0.25% Sodium Lauryl Sulfate, normalized to 100.) SURFACTANT HEIGHT (Initial) HEIGHT (5 Min.) HEIGHT (300ppm Calcium) Sodium Lauryl Sulfate 100 (Control) 80 109 Sodium Myristyl Sulfate 105 83 113 Sodium Palmityl* Sulfate 111 109 81 Sodium Stearyl Sulfate 103 103 68 Sodium Arachidyl Sulfate 94 92 61 Sodium Oleyl Sulfate 112 112 108 SODIUM COCO SULFATE 116 114 113 *Usually called Sodium Cetyl Sulfate. Sources: Weil, J.K. J. Oil Chemistry Society; 43, 157 (1966), et al. Smooth Track Shave Cream for Women from Chase is available in Raspberry and Sensitive Skin formulas and comes in a can from DS Containers with spout and dust cap, valve and tip from Summit.
Spray June 2017
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