63 Oleo-Furan Sulfonates
OFS surfactants provide a low carbon alternative petrochemical-based anionic surfactants
while also demonstrating improved properties compared to commercial plant-based
anionic surfactants such as SLS (Table I). CMC and surface tension are metrics commonly
used to determine the surfactant concentration required to achieve micelle formation and
the level of surfactant effect for use in consumer products. In comparison to the leading
petrochemical surfactants, OFS was found to have similar values for surface tension and
CMC, with a significantly lower CMC value compared to the plant-based commercial
surfactant, SLS. Foam generation, measured by both Ross-Miles and high shear test
methods, found exceptionally high levels of foam formed by OFS only exceeded by SLS,
with excellent foam stability.
Krafft point, the temperature above which ionic surfactants are readily solubilized and are
optimally functional for micelle creation, provides an indication of which anionic surfactants
are ideal for use at low temperatures. Depending on the climate where products are being
used and the product storage location, surfactants can be observed to precipitate out of the
product formulation if temperatures are sufficiently low or insufficient solubilizers were
incorporated. OFS surfactants and SLES have exceptional solubility at temperatures down
to 0°C, while both LAS and SLS experience solubility limitations at temperatures below
20°C and 15°C, respectively. To demonstrate surfactant solubility limits in hard water, 0.5
wt% surfactant solutions were titrated with a calcium chloride solution the concentration
at which a precipitate is formed is identified as the hard water tolerance in Figure 4A. Both
SLS (35 ppm Ca2+) and LAS (100 ppm Ca2+) were found to precipitate from solution at
calcium concentrations 500x lower than the 100,000 ppm test limit, while OFS and SLES
remained soluble at the highest calcium concentration tested.
Table I
Select Properties of The Oleo-Furan Sulfonate Surfactant Sodium Lauroyl Methylfuran Sulfonate With
Comparison to Commercial Anionic Surfactants
Surfactant CMC
(ppm)1
Surface
Tension
(mN/m)2
Ross Miles
Foam
Height
(mm)3
High Shear
Foam
Height
(mm)4
Wetting
Time
(sec)5
Krafft
Point
(°C)
Sulfate
Free
Dioxane
Free
Sodium Lauroyl
Methylfuran Sulfonate
799 34 170 /165 75 /75 8 0 ✓ ✓
Sodium Lauryl
Ether Sulfate
4496 326 160 /150 50 /48 15 0 X X
Sodium Dodecyl
Benzene Sulfonate
8367 35 145 /140 63 /62 5 20 ✓ ✓
Sodium Lauryl
Sulfate
23,657 31 180 /170 80 /78 6 15 X ✓
1 Critical micelle concentration of surfactant in deionized water at room temperature (25°C)
2 Surface tension at CMC
3 Height of foam after initial formation and after 5 minutes (20°C) for 0.1 wt% surfactant following ASTM
D1173
4 Height of foam after initial formation and after 5 minutes (20°C) for 0.1 wt% surfactant following ASTM
D3519
5 Wetting of cotton skein in a 0.25 wt% surfactant solution at 30°C according to ASTM D2281
6 Value reported by vendor (STEOL CS330)23
7 Values reported in literature for SDBS24 and SLS25

64 JOURNAL OF COSMETIC SCIENCE
A common in vitro assessment of dermal irritation known as a Zein test determines the
percentage of the water-insoluble corn protein Zein that is denatured when exposed to
irritants. Zein is representative of protein in the human epidermis, that can be denatured
and thus solubilized in an aqueous surfactant solution. The experience of having “squeaky
clean” skin after applying skin cleaning productions is typically the result of surfactants
penetrating and damaging the skin barrier (stratum corneum) by multiple mechanisms one
example is causing damage to the skin protein keratin.26 This can be particularly irritating
to more sensitive skin with a thinner epidermal layer, particularly in some areas of face such
as the scalp and eyelids.27 The OFS surfactant sodium dodecanoyl methylfuran sulfonate
was observed to dissolve significantly less Zein (1%) compared to all other surfactants
tested, indicating a milder effect consumers prefer in personal care products (Figure 4B).
In addition to providing a milder and more stable ingredient for personal care, OFS
surfactants have demonstrated broad ingredient compatibility, with viscosity building
agents, preservative systems, fragrances, moisturizers, and numerous other common
personal care formulation ingredients. For the results described herein, compatibility is
defined as the ability of the ingredients to be combined and fully dissolved all ingredients
must remain dissolved in solution, without formation of precipitate or phase separation,
for a minimum of one week at room temperature to be considered compatible. With the
guidance of expert formulation consultants, we have developed fully functional personal
care product prototypes featuring OFS surfactants.
Versatility in cosurfactant selection for viscosity building has remained a major focus in
formulation testing with OFS. While most surfactants in the OFS platform do not thicken
with salt alone, a range of rheological properties suitable for personal care products can
be accessed through the use of amide and amphoteric cosurfactants, and is further refined
with the addition of salt in the range of 1–3 wt%. In particular, cocoamidopropyl betaine,
lauroamphoacetate, dimethyl lauramide, glyceryl caprylate, cocamidopropyl hydroxysultaine,
and cocoamide MIPA were among the cosurfactants found to be compatible viscosity
building systems for OFS surfactants, with ingredient loadings in the range of 3–10 wt%.
Polymeric thickeners, including naturally derived hydroxypropyl starch, xanthan gum, and
hydroxyethyl cellulose are also compatible, with typical loadings of 3–6 wt% starch or 0.1–2
wt% gum/cellulose to thicken solutions containing 5–10 wt% OFS and 1–3 wt% salt.
While the accessible viscosity ranges varied with the selected cosurfactant or polymer,
formulations generally achieved consistencies consumers prefer for body wash and shampoo
Figure 4. Hard water stability (A) and Zein skin irritation test results (B) for 0.5 wt% anionic surfactant
solutions. Hard water stability is defined as the concentration of calcium salt that induces surfactant
precipitation. Higher percentages of remaining Zein protein indicate less dermal irritation.