Span = sorbitane monooleate

The study of inverse adhesive emulsions has revealed the same features as direct emulsions [112,113]. Here again, it was shown that adhesion is favored when the surfactant becomes less soluble in the continuous phase [113]. This can be tested experimentally by using binary mixtures of oils, one in which the surfactant is soluble and another one in which the surfactant is insoluble. For example, water droplets can be stabilized in mineral oil by sorbitan monooleate (Span 80). This surfactant is soluble in dodecane whereas it is not in silicon oil. The affinity of the surfactant for the organic solvent can be tuned by mixing dodecane and silicon oil. As shown in Fig. 2.38, the energy of adhesion between water droplets strongly varies as the ratio of the mixture is changed. A sharp rise is noted as the surfactant... 

Figure 2.38. Energy of adhesion between water droplets stabilized with sorbitan monooleate (Span 80) in a silicon oil-dodecane mixture. The arrow indicates the insolubility threshold of the amphiphUe. (Adapted from [113].)...

Researchers at Unilever [128] discovered that the surfactant used to form the HIPEs must be of low HLB value (between 2 and 6), as would be expected for w/o emulsions. The optimum surfactant was sorbitan monooleate (Span 80), which has an HLB value of 4.3. However, the HLB number of the surfactant is not the only criterion for the preparation of stable HIPEs the chemical nature was also found to be of importance [105]. 

Water-in-oil concentrated emulsions have also been utilised in the preparation of polymer latexes, from hydrophilic, water-soluble monomers. Kim and Ruckenstein [178] reported the preparation of polyacrylamide particles from a HIPE of aqueous acrylamide solution in a non-polar organic solvent, such as decane, stabilised by sorbitan monooleate (Span 80). The stability of the emulsion decreased when the weight fraction of acrylamide in the aqueous phase exceeded 0.2, since acrylamide is more hydrophobic than water. Another point of note is that the molecular weights obtained were lower compared to solution polymerisation of acrylamide. This was probably due to a degree of termination by chain transfer from the tertiary hydroxyl groups on the surfactant head group. 

Let us first consider an inverted W/O emulsion made of 10% of 0.1 M NaCl large droplets dispersed in sorbitan monooleate (Span 80), a liquid surfactant which also acts as the dispersing continuous phase. At this low droplet volume fraction, the rheological properties of the premixed emulsion is essentially determined by the continuous medium. The rheological behavior of the oil phase can be described as follows it exhibits a Newtonian behavior with a viscosity of 1 Pa s up to 1000 s 1 and a pronounced shear thinning behavior above this threshold value. Between 1000 s 1 and 3000 s1, although the stress is approximately unchanged, the viscosity ratio is increased by a factor of 4. 

Fig. 8. W/O emulsions in pure Span 80 (sorbitan monooleate) a premixed emulsion, b emulsion sheared at 50 s c emulsion sheared at 1000 s 1, d emulsion sheared at 3000 s. Note that for images a and b, the bars represent 122 pm whereas for images c and d they represent 12.2 pm...

GLYCOMUL O lONET S-80 LIPOSORB O LIPOSORB 0-20 ML 33F ML 55F MONO-DEHYDROSORBITOL MONOOLEATE MONTAN 80 NIKKOL SO 10 NIKKOL SO-15 NTKKOL SO-30 NONION OP80R O 250 RADIASURI 7155 SORBESTER P 17 SORBITAN MONOOLEIC ACID ESTER SORBITAN O SORBITAN OLEATE SORGEN 40 SPAN 80... 

Fig. 9 The effect of shear stress on aggregate size and boundary fractal dimension, of 0.08% (w/w) lactose suspended in 1,1,2-trichlorotrifluoroethane in the presence of 0.03% (w/w) surfactant sorbitan monooleate (Span 80). (From Refill)...

Polysorbates are surfactants that are pegylated derivatives of sorbitan monoesters (i.e., monolaurate, monopalmitate, monostearate, monooleate, or monoisostearate) or sorbitan triesters (i.e., tristearate or trioleate) and are available in many grades. Poly-sorbate 80, also known as Tween 80, is a mixture of polyoxyethylene 20 sorbitan monooleates and is a yellow viscous liquid at room temperature. Sorbitan monooleate, also known as Span 80, is a yellow viscous... 

Austad J. Allergic contact dermatitis to sorbitan monooleate (Span 80). Contact Dermatitis 1982 8 426—427. 

Any pair of emulsifying agents that fall at opposite ends of the HLB scale - for example. Tween 80 (sorbitan monooleate with 20 mol EO, HLB = 15) and Span 80 (sorbitan monooleate, HLB = 5) - can be taken and used in various proportions to cover a wide range of HLB numbers. The emulsions should be prepared in the same fashion, with a few percent of the emulsifying blend. The stability of the emulsions can then be assessed at each HLB number, either from the rate of coalescence or qualitatively by measuring the rate of oil separation. In this way it should be possible to determine the optimum HLB number for a given oil. Subsequently, having found the most effective HLB value, various other surfactant pairs can be compared at this HLB value to identify the most effective pair. 

Typically, the oil phase contained 78% monomer/co-monomer, 8% divinyl benzene (cross-linking agent), and 14% non-ionic surfactant Span 80 (Sorbitan monooleate), while the aqueous phase contained 1% potassium persulfate as the initiator. In most cases studied here, monomer is styrene and when elasticity of the polymer is required, 2-ethylhexyl acrylate (2EHA) was used (styrene/2EHA ratio is 1 4). Whenever additives/fillers are placed in the aqueous phase their amounts are stated as weight percent while the phase volume of the aqueous phase remains constant. In some cases, the aqueous phase contains 0.5% hydroxyapatite and 15% phosphoric acid which is used to dissolve the hydroxyapatite, or alternatively, the aqueous phase may contain varying amounts of water-soluble polymer, such as polyethylene glycol or polyethylene oxide. If the styrene-based PHP is to be sulfonated to obtain ionic-hydrophilic foam, the pre-dispersion of sulfuric acid within the pores is useful, if not essential, and in that case, acids (typically 10%) can be used as the internal phaseP . ... 

The liquid gelators, Span 80-Tween 80 also forms emulsion organogels and emulsion hydrogels by fluid-filled fiber mechanism. It has been reported that Span 80 (sorbitan monooleate) and Tween 80 (polyoxyethylene sorbitan monooleate) mixed in the ratio of 1 2 w/w forms organogel with better firmness and architecture as compared to the other surfactant mixture ratios.When water is added dropwise into the homogenous surfactant mixture and oil, it forms spherical reverse-micellar droplets. These droplets/fibers self-assemble to form three-dimensional architecture to immobilize apolar solvent. " Similarly, in case of hydrogels micellar structures are formed, which entraps the external liquid phase to flow and form hydrogel. 

Acconon MC-8 PEG-8 glyceryl caprylate/caprate 14 Span 80 Sorbitan monooleate 4.3... 

The oil phase consisted of 36 g of kerosene with 530 wt% of surfactant. The surfactant was sorbitan monooleate (Span 80 ) and sorbitan monostearate (Span 60 ) with a weight ratio of Span 80 /Span 60 = 3 1. The water phase consisted of TTIP, diethanolamine, methanol and water. DEA was used as a stabilizer to control the hydrolysis rate of TTIP, and methanol was used to increase the compatibility between water and TTIP. The molar ratio of... 

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