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METHYL PERFLUOROBUTYL ETHER.

Insufficient Data CAS 163702-07-6 / SOLVENT, VISCOSITY CONTROLLING

Methyl Perfluorobutyl Ether is a volatile fluorinated ether solvent used to enhance product spreadability and deliver a pleasant, non-greasy feel. It aids in ingredient mixing and can generate micro-bubbles for deep cleansing when combined with specific detergents.

Solvent Viscosity controlling Softener Spreading agent Film former (subtle barrier) Emulsifier/mixer (oily and water-based components) Micro-bubble generator (with detergents)

Science

Acting as a mild solvent and softener, Methyl Perfluorobutyl Ether facilitates easy product application and imparts a silky, non-greasy sensation. It effectively blends immiscible oily and water-based components, contributing to product consistency and longevity. Additionally, it can form a subtle protective barrier on the skin that allows respiration. A notable mechanism involves its ability to produce micro-bubbles for deep-cleansing when formulated alongside a detergent.


Research

Medium confidence
Effective range 2–9%
Optimal

N/A


Transparency

Not commonly dusted

The Formula

Solubility
Oil
Optimal pH N/A
0 7 14

Stability

Methyl Perfluorobutyl Ether is volatile at ambient temperatures; therefore, accurate measurement and mixing should occur in a cool environment, ideally below 30°C and not exceeding 40°C, to prevent evaporation. It should be introduced as the final ingredient in the formulation process, blended gently at low speed without the use of a vacuum pot. To maintain product integrity and prevent evaporation, finished formulations containing this ingredient require vacuum-sealed packaging. Effective emulsification and a sufficiently viscous formula are crucial to prevent phase separation. While the material is considered stable, no specific cosmetic incompatibilities are currently identified.

Synergies

  • Detergents (to activate micro-bubble generation for deep cleansing)

Safety

CIR Status
Not reviewed
Pregnancy
Safe
Sensitization risk Moderate

Methyl Perfluorobutyl Ether is categorized as a PFAS variant, identified in 6.5% of PFAS-containing cosmetic products by the FDA's 2025 report. It has not undergone formal safety assessments by major scientific bodies such as the CIR or SCCS. While some sources indicate a low risk coefficient (1) and suggest it generally has no adverse impact on pregnant individuals, with no obvious toxicity observed in studies, the FDA report highlights significant data gaps. These gaps include limited data on use levels, absence of dermal/oral absorption data, lack of mechanistic information, and no dermal toxicity data. Although a 3M MSDS indicates no significant skin or eye irritation is expected, the EWG raises concerns regarding enhanced skin absorption, high use restrictions, moderate endocrine disruption, high persistence and bioaccumulation, and moderate non-reproductive organ system toxicity. ECHA C&L Inventory reports 'Harmful if inhaled' in 24.8% of cases, though 71.4% do not meet GHS hazard criteria. Due to potential individual sensitivities, a patch test is recommended prior to extensive use.


Your Skin

Yes Normal
Yes Dry
Yes Oily
No Sensitive
Irritancy Unknown
Comedogenicity Unknown

Our Assessment

Insufficient Data

Methyl Perfluorobutyl Ether offers notable functional benefits in formulations, including enhanced spreadability, a non-greasy skin feel, and a unique micro-bubble cleansing action, but its classification as a PFAS and the lack of comprehensive safety assessments by established regulatory bodies necessitate a cautious approach due to significant data gaps.


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