**3.1 Thermodynamics as a means to understand and prevent macro-scale changes and damages resulting from molten or solid polymer/solvent interactions**

Thermodynamics is a useful and powerful means to understand and prevent polymer macro-scale changes and damages resulting from molten or solid material/solvent interactions. Two engineering examples are illustrative: foaming processes with hydrochlorofluorocarbons (HCFCs) as blowing agents in extrusion processes with a concern on safeguarding the ozone layer and the global climate system, Montreal Protocol (Dixon, 2011), and transport of petroleum fluids with in-service pipelines made of structural semicrystalline polymers which are then exposed to explosive fluctuating fluid pressure (Dewimille et al., 1993).
