Study and analysis of the surfaces of the solid polymers Physicochemical properties

The surface properties of a material are always of great importance, both scientifically and in terms of practical applications. Thermodynamically speaking, the surface possesses excess free energy γ, which determines its surface chemical reactivity and the success of a bonding operation, for example. The aesthetic appearance of the finished product often influences its market value. The surface is the site of phenomena that produce major changes in the material and condition its lifespan: thermomechanical fatigue cracking, corrosion degradation, mechanical interactions with another solid material responsible for the formation of scratches, film delamination, friction and wear... The properties of a material are the result of its history (elaboration and shaping) and are very often significantly different in volume and at the extreme surface. Measuring extreme surface properties is therefore both an important and difficult problem, often requiring specific techniques. This is particularly true of polymers, which are not very dense and have relatively mobile molecules at room temperature, making them more sensitive to the environment (temperature, gas, humidity, liquid) than most common metal alloys. Polymer coatings are also increasingly used to enhance the aesthetic appearance of parts in the mechanical, automotive, optical and food industries....

This article complements [AM3279] on mechanical and tribological properties. The forming process naturally induces heterogeneity of molecular organization in the thickness of the parts. As a result, polymer surfaces have a specific organization that combines with the presence of a free surface. The dynamic aspect of polymer surfaces presents a different molecular mobility to that of the volume. Surface organization, which depends on the forming process, has consequences for optical properties as well as reactivity to aging, surface treatments and surface adhesion.