Surfactant level, effect

Carboxjiates with a fiuorinated alkyl chain ate marketed by the 3M/Industrial Chemical Products Company under the trade name Fluotad surfactants. They also include other functional derivatives of fiuorinated and perfluorinated alkyl chains. Replacement of hydrogens on the hydrophobe by fluorine atoms leads to surfactant molecules of unusually low surface tension. This property imparts excellent leveling effectiveness. 

Williams [129] discovered that the surfactant level had a profound effect on the cellular structure of PolyHIPE materials. Below about 5% surfactant, the... 

Surfactants have been, reprotedly, used to prevent extensive puffing of extruded cereal products. It was found in these studies that surfactants could effectively inhibit gelatinization of cereal starch. However, effect of surfactants on protein texturization has not been reported. Two types of surfactants, sodium stearoyl-2-lactylate and calcium stearoyl-2-lactylate (at levels of 0.2 and 0.4% based on the weight of the flour), were mixed with soy flour prior to extrusion. A yeast protein (Torutein, manufactured by Amoco Inc.), claimed to be an extrusion helper although its function is not known, was added. 

Effect of surfactant level. Much of the earlier work on this reaction system was carried out using sodium dodecylbenzene-sulphonate as the surfactant. In the course of experiments which were Intended to investigate the effect upon polymerisation rate of varying the surfactant level, it was discovered that purified sodium dodecylbenzenesulphonates are apparently able to act as initiators of free-radical emulsion polymerisation in the absence of other added Initiating substances. Furthermore, as the results summarised in Figure 5 show, the rate of polymerisation in the absence of added initiator is directly proportional to the concentration of sodium dodecylbenzenesulphonate In the aqueous phase. 

Effect of initiator level. The effect of increasing amounts of cobalt(III) acetylacetonate upon the rate of polymerisation is complex. Whilst the rate always appears to increase as the initiator level increases (in contrast to the behaviour observed when the surfactant level is increased), the order of reaction with respect to initiator depends upon the concentration of surfactant in the aqueous phase. The results summarised in Figure 9 show that the order is approximately the Smlth-Ewart value of 0.4 at high surfactant concentrations, whereas it falls markedly as the surfactant level in the reaction system is lowered. Figure 10 illustrates the rather surprising observation that the order of reaction with respect to initiator appears to vary linearly with the logarithm of the surfactant concentration. 

Laha and Luthy (33) concluded from soil-slurry studies with three nonionic surfactants at sub-CMC (or sub-CAC) surfactant levels in the aqueous phase that the mineralization of phenanthrene in the absence of surfactant proceeded at least as fast as mineralization in the presence of surfactant. Low (sub-CMC) levels of surfactant were not significantly inhibitory, but neither did they enhance mineralization. At nonionic surfactant doses in excess of the aqueous-phase CMC, these surfactants exhibited an inhibitory effect on phenanthrene mineralization. Subsequent work by Laha and Luthy (52), summarized here in part, was performed to... 

In the first nonphosphate version of a commercial product, phosphate was replaced by NTA (trisodium nitrilotriacetate), a powerful builder, comparable to condensed phosphate in its efficacy in sequestering calcium ions in the washing solution. Because of reports of adverse teratogenic effects in laboratory experiments, this builder was withdrawn from the market toward the end of 1971. It was replaced by sodium citrate, an environmentally more acceptable but inherently less powerful calcium sequestering agent. At the same time surfactant levels were increased by a factor of about three. What had happened in practice (if not in theory) was that higher levels of surfactants had been introduced to compensate for the loss in the builder contribution to washing efficacy provided previously by phosphate. 

Nonionic Surfactants. Gelman (10) studied the effect of a nonionic surfactant (Triton X-100, an ethoxylated octylphenol surfactant containing 67.5 wt % ethylene oxide) on the viscosity of two CieHMHECs. The results are shown in Figure 13. The Brookfield viscosity of these polymers along with that of the unmodified HEC is included for comparison. In the presence of 0.5% surfactant, there was a dramatic drop in viscosity. In fact, at this surfactant level, the HMHEC viscosity profile was very similar to that of the control HEC. The following explanation has been offered to account for these findings. 

The mechanism by which surfactants increase enzyme secretion is not known. It seems likely that the leakiness of cell membranes may vary from one organism to another and thus account for the variability between strains in the amount of enzyme normally secreted. Surfactants may be expected to accumulate at the cell membrane and thereby further increase (or modify) leakiness. As the amount of cell-bound enzyme appears to remain constant (feed-back control), increased secretion leads to increased enzyme production as the cell attempts to maintain the cell-bound level. In the case of surfactant-stimulated production of a-amylase by A. oryzae, the higher enzyme production may be accompanied by a lower mycelial weight. At some critical level of surfactant, the effect on the cell wall becomes so great that the cells lyse, and growth as well as enzyme production cease. 

The parameters discussed above have direct effects on extraction rates. In addition, several variables exist which, since they influence membrane stability, have secondary effects on rates. Unstable membranes which liberate some of their internal phase to the external phase, either by "leakage or rapture, show a significantly lower "apparent extraction rate. The most importam of these parameters are the viscosity of the emulsion, the amount and type of surfactam used in enmlsiott preparation, the size of the internal micro-subdroplets, and the operating conditions of the mixer. "- - Membranes of very low viscosity or with inadequate surfactant levels are unstable. Hochhauser and Cussler observed that a 50% increase... 

HSAS, with its surface activity and solubility, is weight effective and can be used by the formulator to deliver superior cleaning performance versus traditional surfactants. HSAS can also be used to optimize surfactant level in laundry detergent products. P G partnered with Shell to develop HSAS. 

A recent thesis by Adams deals with the unusual subject of the acid-catalysed emulsion polymerization of silicone monomers. Some interesting effects are reported and tentative interpretations given. Thus the rate of polymerization per unit volume of aqueous phase is found to depend markedly upon the ratio of aqueous phase to monomer phase. Furthermore, the effect of increasing the surfactant level in the reaction system is unusual in two respects (a) the rate of polymerization passes through a maximum, and (h) the order of reaction with respect to surfactant over the range of surfactant level for which the rate increases is approximately 0.4. 

Another way of comparing distributions is to compare the variation of their statistical characteristics (mean, standard deviation, skewness, etc.). Gerrens (4) has provided tables of experimental particle size distribution statistics to show the effect of changes in initiator levels, surfactant levels, monomer/water... 

Amphoteric Surfactants Surfactants that have both positively and negatively charged hydrophilic groups within the molecule are referred to as amphoteric surfactants. The detergency of these surfactants varies with pH, and they show bacteriostatic activity at appropriate pH Amphoteric surfactants are effective leveling agents and aid in controlled diffusion of dyes and finishes onto the fiber. 

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