The average SPF efficiency (SPF/1% sunscreen used) of a day-wear photo-protecting product sold in the U.S. is only around 1.8, while that of a beach product is 2.5. A good SPF booster can significantly increase this SPF efficiency depending on the base formulation and types of sunscreens used. SPF boosters are ingredients that can significantly increase in vivo SPF but don’t alone contribute meaningfully to SPF.
Many SPF boosters can also significantly improve the wash/wear resistance of formulations and reduce sunscreen skin penetration. The normal use level in formulations is 1-3% on an active basis and most work primarily by increasing UV absorption by maintaining the sunscreen film thickness on skin over time. Other mechanisms include increasing UV scattering ability of sunscreens, increasing the UVA coverage by extending the critical wavelength, improving the UV stability of sunscreens and reducing skin erythema.
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The various types of SPF boosters include oil soluble and hydrophilic polymer solutions/dispersions/powders (polyurethanes or polyacrylates), emollients, waxes, and anti-inflammatory agents. Oil soluble and hydrophilic polymers function mainly by film formation causing an increase in UV absorption by maintaining a thicker sunscreen film on skin over time. Polymeric and non-polymeric waxes can also form solid sunscreen-containing particles in oil-in-water emulsions that can increase UV absorption and scatter. Emollients are mainly used to help dissolve crystalline sunscreen like Avobenzone or Benzophenone 3, extend UVA coverage by increasing the critical wavelength, and improve Avobenzone photostability.
- Combine SPF boosters that work by different mechanisms.
- Hydrophilic polymers combined with oil soluble polymers.
- Emollients combined with oil soluble or hydrophilic polymers.
- UV scattering agents combined with oil soluble or hydrophilic polymers.
- Use multifunctional technologies that can provide additional benefits.
- Emollients can boost SPF, can solubilize, and photo stabilize Avobenzone.
- Many polymers can also improve the wear or wash resistance of formulations.
- Develop efficient systems that work at <2% solids in order to maintain good skin feel (emollients may be needed at a higher concentration if used to solubilize Avobenzone)
Recommended Oil-Soluble Polymers
- Antaron/Ganex V220F (VP Eicosene Copolymer) by Ashland - A key benchmark.
- Antaron/Ganex WP 660 (Tricontanyl/PVP) by Ashland.
- OleoCraft HP-31, OleoCraft MP-30, OleoCraft MP-31 (Polyamide 3) by Croda
- Performalene 400 (Polyethylene) by New Phase Technologies
- Performa V1608 (C30-38 Olefin Isopropyl Maleate/MA Copolymer) by New Phase Technologies
- Syncrowax ORM (Sorbitol/Sebacic Acid Copolymer Behenate) by Croda
Recommended Hydrophilic Polymers
- SunSpheres (Styrene/Acrylates copolymer, 90% active powder) by Dow Chemical is a 350 nm hollow particle that scatters UV. It is one of the best SPF boosters on the market and good with metal oxides.
- Syntran PC 5227 (Polyacrylate 15 and 17, 30% Latex solids) by Interpolymer
- Baycusan C1000 (Polyurethane 34, 40% latex solids) by Bayer Material Science
- SolaStay S1 (Ethylhexyl Methoxycrylene-Hallstar Company)-can dissolve ~32% Avobenzone and is an excellent photo stabilizer.
- Corapan TQ (Diethylhexyl 2,6-Naphthalate) by Symrise can dissolve ~18% Avobenzone and is a good photostabilizer.
- Pelemol BIP (Butylphthalimide/Isopropylphthalimide) by Phoenix Chemical can dissolve ~40% Avobenzone.
- X-Tend 226 (Phenylethyl Benzoate) by Ashland can dissolve ~24% Avobenzone.
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