The ongoing quest for a D5 replacement
As the regulatory pressure continues on the use of cyclomethicone compounds, it is looking increasingly that silicone will continue to be needed to achieve the combination of properties needed to make a truly functional product. The set of requirements for a functional product appear to be mostly physical (surface tension, spreading, wetting and volatility) rather than chemical.
The regulations that are imposed on the use of D5 continue to grow. These are outlined in Table 1.
This increased regulation will put more pressures on to find suitable replacements, what originally sounded like a reasonable task has proven to be a difficult undertaking.
What gives D5 its feel? This turns out to be a rather complex question, related to both physical chemistry and structure.
Cyclomethicone compounds possess a cyclic structure rather than the chain structure of linear dimethyl silicones (dimethicone). Likewise, D5 has a low heat of vaporization and low vapor pressure has led their use as cosmetic vehicles. Volatility has some impact on the feel. It is quite interesting that D4 is appreciably more volatile than D5.
Volatility is but one aspect of the complex phenomenon that contributes to a dry feel in a solvent used in cosmetics. Other considerations that impact upon selection of a D replacem ...