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HEXYLTRIMETHOXYSILANE.

Questionable CAS 3069-19-0 / SKIN CONDITIONING

Hexyltrimethoxysilane is a silane derivative designed to impart hydrophobicity to surfaces, creating a water-repellent yet vapor-permeable barrier. It functions as a coupling agent, enabling stable bonds between organic and inorganic components in a formulation.

Hydrophobicity modifier Coupling agent Skin-conditioning agent Emollient

Science

This ingredient leverages its molecular structure, featuring a hexyl organic chain and three hydrolyzable methoxy groups, to form stable bonds between organic polymers and inorganic surfaces. On skin, it creates a non-polar, water-repellent barrier that effectively repels moisture while maintaining high permeability to water vapor, allowing the skin to 'breathe' and preventing moisture entrapment.


Research

Low confidence
Effective range N/A
Optimal

N/A


Transparency

Not commonly dusted

The Formula

Solubility
Both
Optimal pH 3 – 5
0 7 14

Stability

Hexyltrimethoxysilane is stable in sealed containers. However, it reacts slowly with ambient moisture or water, leading to the liberation of methanol. Hydrolysis and condensation rates are significantly influenced by pH; an acidic range of 3-5 is optimal for fast hydrolysis and slow condensation, essential for forming stable functionalized nanoparticles.

Conflicts

  • Moisture
  • Water
  • Heat
  • Open flames
  • Sparks

Safety

CIR Status
Safe with restrictions
Sensitization risk Moderate

While the CIR Expert Panel issued a tentative report considering Alkoxyl Alkyl Silanes (including Hexyltrimethoxysilane) safe for cosmetic use under present practices, GHS classification indicates it causes skin irritation (H315) and serious eye irritation (H319). It also slowly liberates methanol upon exposure to moisture, which is associated with chronic central nervous system effects. Individual FDA approval is not in place; its use is typically as a component within products covered by broader group standards.


Your Skin

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

Our Assessment

Questionable

Despite its potential as a hydrophobicity modifier and coupling agent for cosmetic formulations, the classification as a skin and eye irritant and the liberation of methanol raise significant safety concerns for precision skincare applications.


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