- ▸ Coupling agent: Bonds silica and mineral fillers to rubber and polymer matrices.
- ▸ Adhesion promoter: Improves filler-to-polymer coupling in compounds.
- ▸ Processing aid: Functions as a processing aid in rubber compounding.
- ▸ Binder: Links inorganic filler into the organic polymer network.
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.
Request SDS →Bis[3-(triethoxysilyl)propyl] tetrasulfide (CAS 40372-72-3) is a sulfur-functional organosilicon coupling agent. It is used as an adhesion/cohesion promoter and processing aid, and it acts as a binder linking inorganic fillers to organic polymer matrices. The tetrasulfide bridge and triethoxysilyl groups let it bond silica to rubber networks.
Regulatory & registration requirements
- TSCA (US):
- REACH (EU): Not determined from public registry
- EC number: 254-896-5
Source: EPA TSCA Inventory (July 2025 release) · ECHA CHEM — retrieved 2026-07-12
Solutions Using This Product
Process-solution guides on this site that specify this chemistry:
- Silane Adhesion Promoters for Rubber-to-Metal Bonding (Plastics & Polymers)
- Rubber & Elastomer Compounding Ingredients (Industrial Manufacturing)
- Sulfur Silanes for Silica Tire-Tread Coupling (Plastics & Polymers)
Frequently Asked Questions
What does "bis" mean in this silane's name?
In chemistry "bis" means two of the named group. Here it denotes two 3-(triethoxysilyl)propyl groups joined by a tetrasulfide bridge, the structure of CAS 40372-72-3 (C18H42O6S4Si2).
What is bis-(3-triethoxysilylpropyl) tetrasulfide (Si-69, TESPT) used for?
It is a sulfur-functional organosilicon coupling agent and binder. The triethoxysilyl groups bond to silica and mineral fillers while the tetrasulfide bridge links into the rubber network, so it serves as a coupling agent, adhesion promoter, and processing aid in rubber compounding.
How does Si-69 (tetrasulfide) differ from Si-75 (disulfide)?
Both couple silica to rubber; the sulfur rank differs. Si-69 is the tetrasulfide (four sulfur atoms, CAS 40372-72-3) and Si-75 is the disulfide (two sulfur atoms, CAS 56706-10-6). The higher sulfur content of Si-69 contributes more to crosslinking and changes scorch behavior.
What is the CAS number and HS code for TESPT?
Bis[3-(triethoxysilyl)propyl] tetrasulfide is CAS 40372-72-3, molecular formula C18H42O6S4Si2. It classifies under HS 2931.90 (organo-inorganic compounds, other); we confirm the destination-specific code on the quote.
How is Si-69 supplied in bulk and can you provide a CoA and SDS?
We supply TESPT/Si-69 in bulk industrial packaging for tire and rubber compounders, with packaging and MOQ confirmed per order. A Certificate of Analysis and Safety Data Sheet accompany shipment; request a bulk quote with your target volume.
What is the REACH and TSCA regulatory status of Bis Tetrasulfide (TESPT)?
Bis Tetrasulfide (TESPT) (CAS 40372-72-3) is listed as Active on the U.S. EPA TSCA Inventory; its REACH registration status is not determined from the public ECHA registry.