56 SUN CARE
Nonporous aqueous gels provide additional SPF boost Silica gels that are nonporous cannot scatter light, which means they do not provide any SPF boost when used alone with an active ingredient in an inorganic sunscreen formulation. However, when they are added along with porous silica gels, they boost SPF even more because they improve the dispersion (physical spacing) of sunscreen actives when the product is applied to the skin. The sunscreens apply better, going on both
thicker and more consistently with reduced greasiness. For example, adding 2% aqueous nonporous gels with a mean particle size of 10,000 nm and specific surface area of 50 m2
/g
to an inorganic sunscreen system will boost SPF another 75%. Combining nonporous silica gels along
with porous silica gels also makes it easier for formulations to pass the freeze/thaw test. Formulations that contain both porous and nonporous silica gels are more stable, especially at low temperatures.
Processing advantages of silica gels When it comes to manufacturing a skincare formulation, using silica gels to increase SPF is much more appealing than using waxes. Waxes require both phases to be heated and require high-shear mixing through the temperature that the waxes recrystallize. Formulations using silica gels can be
processed at room temperature, and silica gels can be added after the emulsion is formed. In fact, this is the preferred method for achieving the highest SPF-boosting efficiency.
Test formulations demonstrate results ACT Solutions Corp has developed test formulations that demonstrate the effects of adding porous and nonporous silica gels.
ACTS 23095 Coconut Care SPF + ■ High-SPF sunscreen (in vitro 70+) UVA/UVB sun protection with moisturizing and skin- conditioning characteristics. ■ In vitro SPF 72, critical wavelength 372.4 nm ■ In vitro SPF without silica gels 19.9 ■ 18% zinc oxide ■ No whitening ■ Moisturizing but with no greasiness ■ Leaves skin with a “perfected” appearance ■ Ideal for face and body ■ W/O structure provides inherent water resistance ■ 2% porous silica gels, 2% nonporous silica gels
22514 Shade Perfect ■ A hydrating, nongreasy tinted moisturizer with a 50+ SPF. ■ Contains only 9% (UVA-attenuating) titanium dioxide plus 3.75% iron oxides ■ In vitro SPF >50 ■ Provides enhanced UVA protection (age, discoloration, cancer) with a critical wavelength of 386 nm ■ Hydrating, nongreasy formula ■ Designed for darker complexions ■ Lightly tinted, no whitening on skin ■ 2% porous silica gels, 2% nonporous silica gels
PERSONAL CARE October 2022 No SOLESPHERE™ ■ 2% H-33, 2% NP-100 ■ 2% H-53 ■ 2% H-53, 1% NP-100 ■
120 100 80 60 40 20 0
260%
210%
218%
63% 117%
(w/2% H-33, 2% NP-100)
15-18% ZnO cream
Organic blend cream (w/2% H-33)
(w/2% H-53, 1% NP-100)
Figure 3: Combining nonporous silica gels along with porous silica gels boosts SPF because they improve the dispersion of sunscreen actives when the product is applied to the skin
TABLE 1: TEST FORMULATIONS DEMONSTRATE IN VITRO SPF INCREASE AFTER ADDING POROUS AND NONPOROUS SILICA GELS
Formulation Example 1 Example 1 + H + NP Example 2 Example 2 + H Example 2 + H + NP Example 3 Example 3 + H Example 3 (simulated) Example 3 + H Example 4 Example 4 + H Example 4 + H + NP
In Vitro SPF
20 72 10 24 31 11 35 21.5* 35 12 16 26
Increase Over
Control – 260% – 140% 210% – 218% – 63% – 33% 117%
* Expected SPF based on simulation for organic blend ** 10% homosalate, 7% octocrylene, 5% octisalate 2% avobenzone
W/O products using mineral actives will
always be difficult to produce, but you can achieve competitive product advantages and consumer acceptance if you improve aesthetics and stability. Porous and nonporous silica gels make it possible to produce W/O formulations that are more easily processed than traditional wax-containing formulations.
PC
Reference 1. Gripp A, Paraszczuk N, Brito J. Best Practices for Formulating Sunscreen with ZnO. BASF Care Creations North America. 1 June 2020.
https://www.happi.com/ issues/2020-06-01/view_features/best- practices-for-formulating-sunscreen- with-zno
www.personalcaremagazine.com
Sunscreen Active
ZnO (18%) ZnO (18%) ZnO (15%) ZnO (15%) ZnO (15%)
Organic blend**
Organic blend**
Organic blend**
Organic blend**
Organic blend**
ZnO (16%) ZnO (16%) Solesphere
H-Grade Porous Spherical Silica
– 2% (H-33) – 2% (H-33) 2% (H-33) – 2% (H-53) – 2% (H-53) – 2% (H-53) 2% (H-53) Solesphere NP-
Grade Nonporous Spherical Silica
– 2% (NP-100) – – 2% (NP-100) – – – – – – 1% (NP-100)
16 ZnO cream
In Vitro SPF
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