A primer (adhesion promoter) is a chemical substance used to improve adhesion between two different materials. As a rule, these are materials that do not normally bond well due to different chemical or physical properties.

A primer is used to create a strong and permanent bond between these materials. They are used in many different applications. Examples of this include the production of composite materials, the coating of surfaces, the bonding of plastics or the treatment of metals. It can help to improve the adhesion and therefore the strength of the connection between the materials.

There are many different types of primers, each designed for specific applications. Examples of this are silanes, which are used to bond glass fibers with synthetic resins, or epoxy resins, which are used to bond metals to plastics. Choosing the right primer depends on various factors, such as the type of materials to be bonded, the environment in which the bond will be used, or the desired strength of the bond.

Overall, a primer is an important part of many industrial processes as it helps create a strong and lasting bond between materials that do not normally bond well.