Advantages of cyclic structure
The diameter of the cyclic molecule of D5 (decamethylcyclopentasiloxane) is about 0.7nm, which is 30% smaller than that of linear silicone oil. This structure makes its evaporation enthalpy only 35kJ/mol, which can evaporate quickly at body temperature, leaving a silky touch without residue. In the oil-control primer, the instantaneous volatilization of D5 can take away 0.5℃ of heat from the skin surface, producing a cooling and astringent effect.


Synergistic effect of formula
When combined with spherical powder, cyclic siloxane can form a directional liquid crystal structure:


The refractive index is adjusted to 1.43 (close to the skin) to achieve a natural makeup effect


The powder is fixed to the depression of the skin texture through capillary action
A brand of air cushion foundation uses the D4/D6 compound system to extend the makeup holding time to 14 hours and reduce the friction decolorization rate by 67%.


Safety controversy and progress
In response to the doubts about environmental accumulation, the newly developed branched cyclic siloxane (C8 substitute) has a biodegradation half-life shortened to 7 days and a skin penetration rate reduced by 90%. The EU ECHA 2023 risk assessment confirmed its safety for use in cosmetics.