Silanes & Organosilanes Available — Bulk Only

Methyltrimethoxysilane (MTMS)

CAS 1185-55-3 · Formula C4H12O3Si · MW 136.22 g/mol

A trifunctional methoxysilane for water repellency, hard-coats, and resin coupling. It is used as a coupling agent in thermoplastic and thermosetting resins, a crosslinker in silicone sealants, a water-repellent component, and in silicone hard-coats for plastics.

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UN Number
UN 1993
Hazard Class
Class 3
HS Code
2931.90
At a Glance
Material Family
Silanes & Organosilanes
Record Type
Pure compound
Primary Role
Coupling / Adhesion Promotion · Crosslinking / Curing
Functional Roles
METHYLTRIMETHOXYSILANE
FILM FORMING
Applications & Use Cases
  • Coupling agent: Couples thermoplastic and thermosetting resins to mineral fillers.
  • Silicone crosslinker: Crosslinks silicone sealant systems.
  • Water repellency: Acts as a water-repellent treatment component for surfaces and substrates.
  • Hard-coats: Used in silicone hard-coat coatings for plastics.
  • Surface modifier and intermediate: Functionalizes surfaces and serves as a silane intermediate.
Physical Properties
Physical Description
Liquid; Liquid; Other Solid; CBI
Boiling Point
103.5 °C @760 [mm Hg]
Density
0.949 @ 20°C
Safety & Handling
Full SDS available on request

A grade-specific Safety Data Sheet (SDS) — with the complete hazard classification, handling precautions, and transport information — is supplied with every shipment and available on request. Confirm all safety and regulatory details against the SDS for your specific grade.

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DOT / UN Transport Classification
DOT hazard class 3 placard
UN / DOT NumberUN 1993
Hazard Class / DivisionClass 3
Proper Shipping NameFlammable liquids, n.o.s.

Transport classification per the UN Model Regulations / 49 CFR 172.101 Hazardous Materials Table. Confirm against the grade-specific SDS (Section 14) before shipping.

HS / Tariff Classification
Harmonized System (HS) Code — 6-digit international heading
2931 . 90
Chapter 29
Organic chemicals
Heading 29.31
Internationally harmonized (WCO HS)
Subheading 2931.90
6-digit international code — national tariff line adds further digits
Chemical Identity
CAS Number
1185-55-3
Molecular Formula
C4H12O3Si
Molecular Weight
136.22 g/mol
IUPAC Name
trimethoxy(methyl)silane
INCI Name
METHYLTRIMETHOXYSILANE
PubChem CID
InChI Key
BFXIKLCIZHOAAZ-UHFFFAOYSA-N
Synonyms & Trade Names
Methyltrimethoxysilane Trimethoxy(methyl)silane Trimethoxymethylsilane Silane, trimethoxymethyl- GLASCA B SILQUEST A 1630 SILANE, METHYLTRIMETHOXY- C4H12O3Si methyl trimethoxysilane DOW CORNING 7-5300 FILM-IN-PLACE COATING DOW CORNING (R) 7-5310 FILM-IN-PLACE BASE Union carbide A-163 methyl-trimethoxysilane
Full Description

Methyltrimethoxysilane (MTMS, CAS 1185-55-3) is a trifunctional methoxysilane that hydrolyzes and condenses into methylsiloxane networks. It is used as a coupling agent in thermoplastic and thermosetting resins, a crosslinker in silicone sealants, a water-repellent component, and in silicone hard-coats for plastics. It also serves as a surface modifier and intermediate.

Frequently Asked Questions

What is methyltrimethoxysilane?

Methyltrimethoxysilane (MTMS, CAS 1185-55-3, C4H12O3Si) is a trifunctional methoxysilane that hydrolyzes and condenses into methylsiloxane networks. It is supplied as a coupling agent, silicone crosslinker, water-repellent component, and silane intermediate.

What is the use of methyltrimethoxysilane?

It functions as a coupling agent linking thermoplastic and thermosetting resins to mineral fillers, as a crosslinker in silicone sealant systems, as a water-repellent treatment component for surfaces and substrates, and in silicone hard-coat coatings for plastics. It also serves as a surface modifier and intermediate.

What is methyltrichlorosilane used for, and how does it differ from MTMS?

Methyltrichlorosilane is a chlorosilane that releases hydrogen chloride on hydrolysis, whereas MTMS releases methanol, making MTMS easier to handle in coupling and crosslinking applications. Both build methylsiloxane networks, but MTMS is the methoxy-functional, non-chlorine-evolving route favored in coatings and sealant formulation.

What is the cost of bulk methyltrimethoxysilane?

Bulk MTMS pricing depends on grade, volume, and packaging (drums vs. totes/IBCs) and market silicon-intermediate costs, so RawSource quotes against your specification rather than a fixed catalog price. Submit a bulk RFQ with target volume and packaging to receive current pricing, MOQ, and lead time.

What is the HS code and CAS number for methyltrimethoxysilane?

MTMS is CAS 1185-55-3 and classified under HS heading 2931.90 (other organo-inorganic compounds). RawSource provides a CoA and SDS with each shipment; confirm the country-specific tariff subheading with your broker.

Disclaimer. Information on this page — including properties, identifiers, hazard, transport (DOT/UN) and tariff (HS) classifications, and applications — is provided for general reference and is compiled from authoritative public sources (e.g. PubChem/ECHA, 49 CFR 172.101, the Harmonized Tariff Schedule). Values are typical and are not a guaranteed specification; the Certificate of Analysis (CoA) for the lot purchased governs. Products are sold for industrial and professional use only. Nothing here is a medical, health, or efficacy claim or advice. Always consult the current Safety Data Sheet (SDS) before handling, storage, transport or disposal, and confirm regulatory status, classification and suitability for your application and jurisdiction. Hazard, transport and tariff classifications must be verified for your specific shipment. RawSource makes no warranty, express or implied, and assumes no liability for use of this information. Trademarks. Third-party trademarks and brand names are the property of their respective owners; any reference is nominative — used only to identify a comparable product — and does not imply affiliation with, sponsorship by, or endorsement by the trademark owner.