The applications of a polymer can be limited by its behaviour versus some environmental parameters from chemical or friction nature for example. The improvement of properties is generally obtained by a suitable compounding with specific additives but there is another route consisting to encapsulate the polymer with a coating making a barrier between the polymer and the environment. Polymer coatings are often technical and economical means to enhance the performance of a polymer by completing its properties with those of another one. For example, natural rubber is very elastic but isn't resistant to ozone.
Coating is a complementary technique of compounding allowing to obtain surface properties completely different from those of the core and vice versa.
One of the problems inherent to coatings is the permanent cohesion between the treated part and the coating, which depends on the adhesion between the two polymers and also on the compatibility of the coefficients of thermal expansion, elongations at break and other physical properties.