Mechanical rubber goods 

Long-lasting adhesion, even under high stresses 

From golf club grips, through toothed belts or transport belts, all the way up to washing machine gaskets, bicycle tires and hoses: Mechanical rubber goods are used in a wide range of different applications. Likewise, a multitude of polymers or rubber types are also used for these products. To manufacture elastomeric plastics from the rubber, the rubber is mixed with different components and vulcanized. Silica and silanes play a decisive role here. 

Reinforcing filler materials such as industrial carbon black or silica are a key component of the rubber mixture. They are added to the formulation to improve the performance of the products. For instance, they can significantly increase tensile strength, elongation at break and abrasion or tear resistance. The rolling resistance of special tires, such as bicycle tires, can also be reduced considerably.  

Evonik offers silanes and silica from a single source 

Under the brand names ULTRASIL® and AEROSIL®, Evonik offers precipitated and fumed silicas as fillers that vastly improve the performance of rubber in many applications. However, these polar silicas are not compatible with non-polar rubber without the use of further additives. If silica is combined with functional organosilanes, however, the different functional groups of the silanes chemically crosslink the two materials when mixing and vulcanizing the formulation. 

By doing so, this silica/silane combination allows the reinforcing properties of silicas to be leveraged optimally in rubber mixtures, while the formulation is also much easier to process. Even when used in polar rubbers such as nitrile rubber (NBR) or polyacrylic rubber (ACM), which are compatible with polar silicas, the system makes the mix stronger and more durable.

Silanes from the COUPSIL® and Dynasylan® portfolio 

Alongside silicas, Evonik also offers a broad range of sulfur, amino, vinyl and other specialty silanes under the COUPSIL® and Dynasylan® brand names, which are specially tailored to customers’ application areas and requirements. Among other things, the choice of silane (and the matching silicas) depends on the type of rubber and the desired crosslinking system, i.e., sulfur or peroxide crosslinking. The emissions generated during vulcanization must also be taken into consideration. VOC-free silanes offer unique benefits in this case. Moreover, Evonik also offers pre-reacted products from the COUPSIL® portfolio – these are silicas that have already been reacted with silanes. 

Ethylene propylene diene monomer rubber (EP(D)M) is the most commonly used rubber that is crosslinked using peroxides. Because it is highly temperature-resistant and withstands many chemicals as well as UV radiation and ozone, it is primarily used for outdoor applications. EPM is used in mechanical rubber goods requiring a high level of thermal stability, such as seals, O-rings or profiles. Here, even small silane quantities have a major impact on reinforcement properties, while compressive deformation is also significantly improved. 

To identify the ideal solution for their customers, Evonik’s silane experts offer worldwide technical support when testing and selecting silica/silane combinations and work with their customers to develop the optimum solution. 

The benefits at a glance: 

  • Lower mixture viscosity 
  • Higher yield stress values 
  • Improved abrasion resistance 
  • Lower compressive deformation 
  • Improved dynamic properties 
  • Reduced rolling resistance