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Hexadecyltrimethoxysilane

  • Ceramic (SiO₂)
  • CAS 16415-12-6
  • IUPAC: Trimethoxy(hexadecyl)silane

Hexadecyltrimethoxysilane (CAS 16415-12-6) appears in 1 of the 1,812 car-care products CarCareTruth tracks (as of June 2026).

Classified Skin Irrit. 2 (H315), Eye Irrit. 2 (H319), and STOT SE 3 (H335 — may cause respiratory irritation). At 1–3% in a finished product the mixture-level classification of these codes is suppressed under CLP additivity rules; FlyBy Forte does not carry H315/H319/H335 at the mixture level. Methanol release on cure adds a low-volume acute inhalation note, dissipated readily in ventilated application.

Hexadecyltrimethoxysilane (CAS 16415-12-6) is a long-chain alkylsilane — a C16 (hexadecyl) tail tethered to a trimethoxysilyl head group. In windshield coatings it acts as the primary film-former: the trimethoxysilyl group hydrolyzes on the glass surface, releasing methanol and condensing into a Si–O–Si network bonded to the silica substrate, while the long alkyl tail orients outward to provide the hydrophobic surface character that beads water.

This is the non-PFAS alternative to fluoroalkylsilane chemistry — the same surface-bonding mechanism without the perfluorinated chain. The trade-off is surface energy: a C16 alkyl tail produces a hydrophobic contact angle, but not the very-low surface-energy oleophobic behavior of a perfluorinated chain. Hazard classifications are H315/H319/H335 at ingredient level, but the 1–3% concentration typical in finished products keeps the mixture-level classification below the CLP threshold for these codes. Methanol is released during cure, which is why SDS §7 sometimes carries a non-boilerplate ventilation note even when SDS §2 does not classify the mixture for inhalation hazard.

Health & environment profile

VOC
no
Prop 65 listed
no
Asthmagen
no
EPA Safer Choice
no
Aquatic toxicity
no
Biodegradable
no
Bioaccumulative
no
Persistent
no
Ozone depleting
no
Microplastic
no
PFAS
no
Env. score
5/5
Purpose: Long-chain alkylsilane primary film-former in windshield coatings. The trimethoxysilyl head hydrolyzes and condenses on the glass surface forming a Si–O–Si network; the C16 hexadecyl tail provides hydrophobic surface character without using fluorine chemistry.

Common questions about Hexadecyltrimethoxysilane

What is Hexadecyltrimethoxysilane used for in car care?
Long-chain alkylsilane primary film-former in windshield coatings. The trimethoxysilyl head hydrolyzes and condenses on the glass surface forming a Si–O–Si network; the C16 hexadecyl tail provides hydrophobic surface character without using fluorine chemistry.
Is Hexadecyltrimethoxysilane a VOC?
No. Hexadecyltrimethoxysilane is not classified as a volatile organic compound (VOC).
Is Hexadecyltrimethoxysilane on California's Proposition 65 list?
No. Hexadecyltrimethoxysilane is not on California's Proposition 65 list.

1 product contain this

Related

Health and environment notes translate the manufacturer Safety Data Sheet, the GHS classification, and authoritative regulatory listings (California Prop 65, EPA). Not medical advice. They describe the ingredient itself; whether a hazard applies to a finished product depends on its concentration and how it's used.