The indirect adhesion is commonly used in the rubber and plastic industry to pursue several goals:
* To produce composite parts with various functionalities, for example soft and hard components as engine mounts
* To produce complex or giant parts starting from simple ones, for example inflatable boats
* To repair damaged parts as bumpers or conveyor belts.
Apart from the simplest method, the direct one (see previous paper) using self-adhesive rubber compounds, untreated substrate and bonding during processing there are many other indirect possibilities according to the number of steps chosen among the panel.
# For each step the goal is to compatibilize the neighbouring materials and to ensure a tight cohesion. For example, the surface treatment of one substrate ensures the compatibility of the bulk material of the substrate and the primer layer.
# If there is a natural compatibility between this substrate and the adhesive, the surface treatment and the primer can be omitted.
# The heat and pressure treatment can be omitted or merged with other operations as vulcanization, curing of paint.