The application of silane coupling agent in tires and rubber products

Sulfur silane coupling agents (SCA-A69X and SCA-S75X) and mercapto silane coupling agents (SCA-S89M and SCA-S89E, etc.) have a very significant modification effect on white carbon black, which can significantly improve the compatibility and reinforcing effect between white carbon black and rubber. They can significantly reduce the Mooney viscosity, heat generation and rolling resistance and the processing property of the rubber compound, and significantly improve the wear resistance of the vulcanized rubber. The introduction of silane coupling agent makes the application of white carbon black in the rubber industry advance rapidly, especially in the "green" low rolling resistance tire filled with all-white carbon black, the role of silane coupling agent is even more powerful and indispensable.  In radial tires, silane coupling agents can also significantly improve the adhesion of the compound to the steel wire.

In addition to tires, silane coupling agents are also used in some other non-carbon black filled light-colored rubber products, such as sports shoe soles, rubber rollers, etc., which are also important for improving the wear resistance of the products. Other rubber products such as rubber hoses, tapes, rubber miscellaneous pieces, etc., especially some non-carbon black fillers filled rubber products(such as white carbon black, kaolin and others).

According to the rubber vulcanization system, the sulfur vulcanization system rubber generally uses sulfur silane coupling agent (SCA-A69X and SCA-S75X) and mercapto silane coupling agent (SCA-S89M and SCA-S89E, etc.); Vinyl silanes (SCA-V71E and SCA-V71C) are generally recommended for peroxide vulcanized rubbers such as silicone rubber and EPDM rubber.

The using methods of silane coupling agent currently mainly include a direct mixing method and a pretreatment method. In the direct mixing method, the silane coupling agent, the inorganic filler and the rubber are uniformly mixed (opening or kneading) in a certain ratio, and then other additives are added. So that it will not prevent the silane coupling agent from coating the surface of the filler. Usually the silane coupling agent is added to 1-2% of the compound. The advantage of this method is that the dosage can be adjusted, the process is simple, but the dispersion effect is not very satisfactory.

The pretreatment method is to first pretreat the surface of inorganic filler with a silane coupling agent by a high agitator, and then mix the surface modified filler with rubber and other auxiliary agents. Usually, the silane coupling agent is added to the filler amount. 1~2%. The advantage of the method is that the modification effect is relatively good, and the silane coupling agent coats the filler firstly, and the utilization efficiency is high; but it will need extra work and equipment.

The Application of Unsaturated Carboxylic Acid Metal Salt in Peroxide Vulcanized Rubber

UCS series Unsaturated Carboxylic Salt are mainly anhydrous metal salt of acrylic acid or  methacrylic acid (zinc salt or magnesium salt, etc.), and the main varieties are zinc acrylate ZDA and zinc methacrylate ZDMA, which are mainly used as a crosslinking agent for peroxide vulcanized rubber.

UCS series unsaturated carboxylic acid metal salts can form an "ionic" crosslinked structure in peroxide-vulcanized rubber. This "ion bond" has good heat resistance and can slide follow the direction of carbon hydrocarbon chain and restore. This makes the vulcanizing agent have the advantages of both the peroxide and the sulfur vulcanizing agent, and can impart high tensile strength and high tear strength to the rubber product, and can also significantly improve the heat aging property of the product.

Unsaturated carboxylic acid metal salt co-crosslinking agent Zinc acrylate ZDA and zinc methacrylate ZDMA are mainly used in some peroxide vulcanized rubbers, such as hydrogenated nitrile rubber (HNBR), butadiene rubber (BR), EPDM Rubber (EPDM), natural rubber (NR), styrene butadiene rubber (SBR), chlorinated polyethylene (CPE), silicone rubber and fluoro rubber.

They are especially suitable for peroxide-cured rubber products that require good heat resistance, oil resistance, ozone resistance, load carrying capacity, dynamic stability, abrasion resistance and wire bonding strength. Such as rubber rollers, timing belts, and V. Belts, seals, belts, hoses, engine mounts and other rubber parts under the hood.

Zinc acrylate ZDA and zinc methacrylate ZDMA can also be used in automotive sealants such as EPDM, natural rubber, butyl rubber, styrene butadiene rubber, etc., which can significantly improve the bonding of sealant to steel, glass, coating and even oily steel. They can also improve the heat resistance and modulus of sealant.

To ensure optimum dispersion and reduce sticking rolls, we recommend the following feeding sequence (either with a two-roll mill or an internal mixer):

1. Add the rubber compound and mix the rubber for about 30 seconds. You can add other additives and materials in the formula without the need of a complete roll. The high viscosity of the gel at the beginning of the rubber can help the dispersion of the additive.

2, add UCS, the mixing time is when the colloid just "eats" the vulcanizing agent. This helps to reduce the stick roller and adverse reactions with other auxiliaries.

3. Add fillers and other processing aids.

4. Add a peroxide vulcanizing agent.

5. Mix the rubber to an appropriate level and use normal mixing time and temperature.

 The amount of UCS co-vulcanizing agent varies depending on the formulation and performance requirements. It is 2-20 parts of the compound, generally less than 10 parts, and the optimum dosage is determined by experiment.