Rubber coupling Agent Si-69

Chemical name: bis-(γ- tristhoxysilylpropyl)-tetrasulfide
CAS No.: 40372-72-3
Chemical Structure:

Specification:

Item	Powder
Appearance	Yellow transparent liquid
Flash point °C ≥	100.0
Total sulfur content %	22.7±0.8
Chlorine content % ≤	0.40
Impurity % ≤	4.0
Density g/cm3	1.080-1.090

What is Si-69?

Si-69, chemically known as Bis(3-triethoxysilylpropyl) tetrasulfide (TESPT), is a widely used silane coupling agent in the rubber industry. It is primarily designed to improve the interaction between silica fillers and rubber polymers, significantly enhancing compound performance. Si-69 reduces filler–filler interaction, improves filler dispersion, and strengthens the rubber–silica bonding, making it a key additive in high-performance rubber formulations.

Properties: 

Si-69 appears as a yellow to light brown liquid with a slight characteristic odor. It is an organosilane compound that is insoluble in water but soluble in most common organic solvents. The material has good thermal stability and reacts chemically with silica during rubber mixing and with rubber polymers during vulcanization. It improves filler dispersion, reduces compound viscosity, and enhances both mechanical and dynamic properties of rubber compounds.

Application: 

Si-69 is mainly applied in silica-filled rubber compounds to enhance the bonding between silica fillers and rubber polymers. It is extensively used in tire tread compounds where it helps reduce rolling resistance while improving wet skid resistance and abrasion performance. Si-69 is also applied in passenger car tires, truck tires, footwear soles, and various industrial rubber products that require improved mechanical strength, durability, and dynamic performance.

Packing: 

In 25kgs bag.

Storage:

Store in a cool, dry, and well-ventilated place, in tightly sealed containers, away from moisture, heat, and strong oxidizing agents. The typical storage life is 1 year when stored in original, unopened packaging.