Silane Coupling Agent (SI-69)
Chemical name: Bis[3-(triethoxysilyl)propyl]tetrasulfide
Other name: KH-si69
CAS: 40372-72-3
Origin: China
Use: Silane coupling agent
We are one of the leading professional manufacturers and bulk suppliers of silane coupling agents (Code: SI-69) in China. We hold valid national chemical production licenses and authoritative ISO9001 international quality certification.
Contact us
- No.420 Zhonghua Road,Qinghuai District, Nanjing,China 210001
- 008618005174481
- Mr.Sam
- sales@nanjingchem.com
Product Introduction
Silane Coupling Agent Si-69 | Bis[3-(triethoxysilyl)propyl] Tetrasulfide |CAS 40372-72-3
1. Product Introduction
Si-69, chemically named Bis[3-(triethoxysilyl)propyl] Tetrasulfide, is a high-efficiency sulfur-containing bifunctional silane coupling agent with CAS number 40372-72-3. It appears as a pale yellow transparent oily liquid at room temperature, featuring unique triethoxysilyl groups and active tetrasulfide bonds in its molecular structure. Unlike conventional vinyl and amino silanes, Si-69 integrates organic sulfur active groups and inorganic hydrolyzable groups, enabling perfect chemical bonding between rubber polymers and inorganic reinforcing fillers.
As the most widely used rubber-specific silane coupling agent in the global industry, Si-69 effectively solves the poor adhesion problem between silica, carbon black and rubber matrix. It significantly improves filler dispersion, enhances mechanical strength, wear resistance, aging resistance and dynamic fatigue performance of rubber products. Meanwhile, it reduces rubber compound viscosity, optimizes processing performance and lowers rolling resistance. Si-69 is a core essential modifier for tire manufacturing, rubber hose, sealing parts and high-performance rubber composite industries worldwide.
2. Product Specifications
| Test Item | Standard Specification | Test Condition / Method |
| Chemical Name | Bis[3-(triethoxysilyl)propyl] Tetrasulfide | – |
| CAS No. | 40372-72-3 | – |
| Molecular Formula | C₁₈H₄₂O₆S₄Si₂ | – |
| Appearance | Pale yellow transparent liquid | Visual Inspection |
| Purity | ≥98.0% | GC Test |
| Sulfur Content | 22.5%–24.0% | Titration Method |
| Refractive Index (nD25) | 1.4850–1.4950 | 25℃ |
| Density (g/cm³) | 1.060–1.100 | 25℃ |
| Boiling Point | ≈250℃ | Normal Pressure |
| Flash Point | ≥100℃ | Closed Cup |
| Moisture Content | ≤0.2% | Karl Fischer Method |
3. Product Features & Applications
Core Product Features
- Bifunctional sulfur-silicon molecular structure: Si-69 contains hydrolyzable ethoxy groups and active tetrasulfide bonds. It can react with hydroxyl groups on inorganic fillers and sulfur groups in rubber molecules simultaneously, forming stable chemical crosslinking bridges and thoroughly improving filler-rubber interfacial bonding.
- Excellent filler modification effect: Effectively solves the agglomeration problem of silica and carbon black fillers, significantly improving filler dispersion uniformity in rubber matrix, reducing material viscosity and optimizing rubber mixing and extrusion processing performance.
- Superior rubber comprehensive performance: Greatly enhances tensile strength, tear resistance, wear resistance and dynamic mechanical stability of rubber products. It effectively reduces rolling resistance and heat generation, improving aging resistance and service life of rubber materials.
- Wide formula compatibility: Perfectly compatible with natural rubber, styrene-butadiene rubber, butadiene rubber, EPDM and other synthetic rubbers, suitable for various sulfur-vulcanized rubber systems with strong universal applicability.
- Stable processing & cost-effective: Low dosage and high modification efficiency, no adverse impact on rubber vulcanization speed. It lowers production comprehensive cost and supports large-scale continuous industrial production.
Main Application Fields
- Tire Manufacturing (Core Application): Widely used in green silica-filled tire formulas. It reduces tire rolling resistance, improves wet-skid resistance and wear resistance, realizes energy-saving and environmental protection performance, and is the standard matching additive for high-performance car tires and truck tires.
- Industrial Rubber Products: Applied in rubber hoses, conveyor belts, rubber rollers, sealing gaskets and shock-absorbing rubber parts. It enhances product structural stability, wear resistance and anti-aging performance, adapting to long-term dynamic working conditions.
- Rubber & Plastic Composite Materials: Used for surface modification of silica, talc, clay and other inorganic fillers filled in rubber and plastic blends, improving interfacial compatibility and mechanical toughness of composite materials.
- Functional Adhesives & Coatings: Serves as adhesion promoter and crosslinking agent for rubber-based adhesives and anti-corrosion coatings, improving bonding strength between adhesive layer and metal/inorganic substrates.
- High-performance Polymer Modification: Suitable for modification of special rubber and thermoplastic elastomers, optimizing dynamic fatigue resistance and high-temperature stability of polymer materials.
4. Packaging, Storage & International Sea Shipping
Packaging Standard
Standard export package: 200kg iron drum. Customized small packages of 25kg drums and 1000kg IBC totes are available upon customer request. All packaging drums are tightly sealed with professional anti-leakage and anti-corrosion treatment, fully adapted to long-distance international sea transportation and cross-border logistics stacking.
Storage Requirements
Store Si-69 silane coupling agent in a cool, dry, ventilated and shaded warehouse. Keep away from high-temperature heat sources, open flames, strong oxidants, acids and direct sunlight to prevent hydrolysis, oxidation and performance deterioration. All packages must be completely sealed to avoid moisture absorption. The valid shelf life is 12 months under standard storage conditions. Re-test technical indicators before use for expired products; qualified products can be used normally.
International Shipping & Hazard Classification
Hazardous Goods Confirmation: Si-69 Silane Coupling Agent is non-dangerous goods for international sea, air and land transportation
UN Number: No UN number required
Hazard Grade: Non-hazardous general industrial chemical
Shipping Notes: Although classified as general chemical goods, avoid long-term high-temperature stacking, sunlight exposure and violent collision during transportation to prevent package leakage and material deterioration. We provide complete export documents including MSDS, COA, test reports and certificate of origin to support fast and smooth global customs clearance.
5. Company Introduction & Production Strength
Founded in 2001, our company is a professional high-tech manufacturer and reliable global exporter of silane coupling agents and fine chemical materials in China. We own a standardized modern chemical production base covering 100 acres, equipped with 5 full-automatic professional production lines dedicated to silane series products. With mature and stable production technology, strict quality control and sufficient daily output, we can flexibly support small trial orders and large-batch full-container orders to meet the diversified procurement needs of global industrial customers.
We attach great importance to independent technological R&D and innovation. Professional R&D engineers and senior laboratory testing technicians account for more than 20% of our total employees. Our R&D team focuses on core technical research and upgrading of Si-69, KH-172 and all series of silane coupling agents, including independent optimization of production processes, development of high-precision product detection and testing methods, formula upgrading of high-purity products, and full-process environmental protection treatment technology for industrial waste gas, wastewater and solid waste, ensuring stable product quality and full environmental compliance.
Our factory has obtained official ISO9001 International Quality Management System Certification and national chemical production license, with complete production qualifications and standardized quality control system. We implement strict raw material incoming inspection, in-process production monitoring and batch finished product testing for every shipment of Si-69, providing high-purity, low-impurity and stable-performance products. With more than 20 years of export experience, our products are exported to Southeast Asia, Middle East, Europe, North America and other global markets, winning long-term trust and recognition from overseas buyers.
6. FAQ
Q1: What is Silane Coupling Agent Si-69?
A1: Si-69 (Bis[3-(triethoxysilyl)propyl] Tetrasulfide) is a high-performance sulfur-containing silane coupling agent specially developed for rubber modification. With dual reactive ethoxy groups and tetrasulfide active bonds, it acts as an efficient interfacial bridge between inorganic fillers and rubber polymer matrix. It is widely used in tire manufacturing, industrial rubber products and rubber composite material industries, being the most mainstream filler coupling modifier for modern green rubber formulas.
Q2: What specifications of Si-69 can you supply?
A2: We mainly supply premium industrial-grade Si-69 silane coupling agent with a purity of ≥98%, stable sulfur content and low impurity content. Customized high-purity special grades and powder composite grades are available according to customers’ special formula requirements. For every batch of goods, we can provide complete official documents including MSDS, COA (Certificate of Analysis) and professional test reports to support global customs clearance and quality inspection.
Q3: What are your export trade advantages for global buyers?
A3: We provide buyer-friendly, low-risk and flexible export services for all global partners, with core advantages as follows:
- Multiple flexible payment methods: Support T/T, L/C at sight and other negotiable international payment terms to reduce customer cooperation risks.
- Free sample service: Provide free Si-69 test samples, customers only need to bear the international courier freight.
- Support trial order: Fully accept small-batch trial orders for new customers to test product quality and application effect before bulk cooperation.
- Complete document support: Provide standard English MSDS, batch COA, ISO certification, production license and full set of export clearance documents.
Q4: What is your company’s market positioning and qualification?
A4: We are one of the leading professional manufacturers and bulk suppliers of silane coupling agents in China. We hold valid national chemical production licenses and authoritative ISO9001 international quality certification. Integrating independent R&D, standardized large-scale production and global export sales, we focus on providing high-quality, cost-effective and stable silane coupling agent products for industrial purchasers worldwide.
Q5: Is Si-69 dangerous goods for international sea shipment?
A5: No. Si-69 silane coupling agent is classified as general non-dangerous chemical, with no hazard grade and no UN number required. The customs declaration and international transportation procedures are simple and efficient, supporting safe and fast global delivery.
