What are adhesion promoters?

Adhesion promoters are chemical substances or systems that enable a permanent bond between rubber and another material, e.g. metal, plastic or fabric. They play a central role in the manufacture of rubber composite parts by Adhesion between dissimilar materials and prevent detachment under load.

 

Function of adhesion promoters

By nature, rubber adheres poorly to smooth, non-polar materials such as steel, Aluminium or Polyamide. Adhesion promoter (also known as bonding agents) act as a chemical bridge between the rubber and the substrate:

  • They cross-link with the rubber during Vulcanisation process
  • At the same time, they adhere to the substrate, e.g. through chemical bonding or microscopic anchoring
  • Depending on the system, they consist of a Primerlayer and a top layer, which are applied one after the other, or single-layer systems, so-called „self-priming adhesives“
  • Due to diffusion processes during the Vulcanisation results in a continuous gradient of the modulus of elasticity in the transition from substrate to rubber, which prevents localised increases in stress

 

Typical adhesion promoter systems are based on resorcinol-formaldehyde latex (RFL), phenolic resins, epoxies, organic Silanes or Polyurethanes - each matched to the material pairing. These are mixtures of substances that provide functional groups for bonding with both the substrate and the rubber. The surface preparation (e.g. Degreasing, roughening) and the correct processing temperature.

 

Application of adhesion promoters

Adhesion promoters are used in the manufacture of the following components: