1. Introduction to plastic materials

Polymeric materials, also known as "plastics", are materials made up of macromolecules formulated in the presence of various additives. The entanglement of long, sometimes branched polymer chains, their level of organization and the presence of intermolecular interactions ensure the material's cohesion and condensed state. Chains may be amorphous (amorphous polymer) or semi-crystalline (semi-crystalline polymer), and may also develop a preferred orientation (oriented polymer) depending on the polymer's ability to crystallize and its thermomechanical history (figure 1 ).