A. Generally this becomes a problem when you’re formulating high SPF products. Liquid sunscreens like homosalate (EU) (avobenzone-19% soluble) and octyl salicylate (EU) (avobenzone-21% soluble) are poor UVB sunscreens but are good solvents for avobenzone and oxybenzone. Octinoxate (octyl methoxycinnamate) (EU) can dissolve up to 26% avobenzone. Also, the presence of multivalent metals can chelate avobenzone and reduce the solubility (zinc and aluminum). A simple way to quickly screen formulations is to make only the oil phase of the formulation and test the samples at low temperatures for crystallization.
Several non-sunscreen emollients to try are:
Tegosoft XC (EU) – Evonik (EU)
C12-15 Alkyl Benzoate, Dipropylene Glycol Dibenzoate
Finsolv TPP (EU) – Innospec Performance Chemicals (EU)
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