**2.2 Development of combined experimental procedures**

644 Thermodynamics – Interaction Studies – Solids, Liquids and Gases

engineering parts for automotive or medicine needs) (Devisme et al., 2007; Haudin et al., 2008), deal with polymer formulation and transformation. The viscous polymer melt partially crystallizes after undergoing a complex flow history or during flow, under temperature gradients and imposed pressure (Watanabe et al., 2003; Elmoumni & Winter, 2006) resulting into a non homogeneous final macrometric structure throughout the thickness of the processed part. The final morphologies are various sizes and shapes of more or less deformed spherulites resulting from several origins: *i)* isotropic spherulites by static crystallization (Ferreiro et al., 2002a; Nowacki et al., 2004), *ii)* highly anisotropic morphologies as oriented and row-nucleated structures (*i.e.*, shish-kebabs) by specific shear stress (Janeschitz-Kriegl, 2006; Ogino et al., 2006), *iii)* transcrystalline layer (as columnar pattern in metallurgy) by surface nucleation and/or temperature gradient, and *iv)* teardrop- -shaped spherulites or "comets" (spherulites with a quasi-parabolic outline) by temperature

Together with the deformation path (*e.g.*, tension, compression), the morphology strongly influences the behaviour of polymers. Some models have attempted to predict the properties of spherulites through a simulation of random distributions of flat ellipsoids (crystalline lamellae) embedded in an amorphous phase described by a finite extensible rubber network (Ahzi et al., 1991; Dahoun et al., 1991; Arruda & Boyce, 1993; Bedoui et al.,

Moreover by considering the high-pressure technology, the use of specific fluids plays a non negligible role in pattern control. The thermodynamic phase diagrams of fluids implies the three coordinates (pressure-volume-temperature, *PVT*, variables) representation where the fluids can be in the solid, gaseous, liquid and even supercritical state. The so-called "signature of life" water (H2O) (Glasser, 2004) and the so-called "green solvent" in fact "clean safe" carbon dioxide (CO2) (Glasser, 2002) can be cited. The use of H2O is encountered in injection moulding assisted with water. CO2 is known as a valuable agent in polymer processing thanks to its aptitude to solubilize, to plasticize (Boyer & Grolier, 2005), to reduce viscosity, to favour polymer blending or to polymerize (Varma-Nair et al., 2003; Nalawade et al., 2006). In polymer foaming, elevated temperatures and pressures are involved as well as the addition of chemicals, mostly penetrating agents that act as blowing

In the transport of fluids, in particular in the petroleum industry taken as an example, flexible hosepipes are used which engineering structures contain extruded thermoplastic or rubber sheaths together with reinforcing metallic armour layers. Transported fluids contain important amounts of dissolved species, which on operating temperature and pressure may influence the resistance of the engineering structures depending on the thermodynamic *T*, *P*-conditions and various phenomena as sorption/diffusion, chemical interactions (reactive fluids, *i.e.*, oxidation), mechanical (confinement) changes. The polymer damage occurs when rupture of the thermodynamic equilibrium (*i.e.*, after a sharp pressure drop) activates the blistering phenomenon, usually termed as 'explosive decompression failure' (XDF) process (Dewimille et al., 1993; Rambert et al., 2006; Boyer et al., 2007; Baudet et al., 2009). Damage is a direct result of specific interactions between semi-crystalline patterns and solvent with a preferential interaction (but not exclusive) in the amorphous phase (Klopffer & Flaconnèche,

gradients (Ratajski & Janeschitz-Kriegl, 1996; Pawlak et al., 2002).

agents (Tomasko et al., 2003; Lee et al., 2005).

**Damage of polymer structure in on-duty conditions** 

2006).

2001).

The coupling of thermodynamic and kinetic effects (*i.e.*, confinement, shear flow, thermal gradient) with diffusion (*i.e.*, pressurizing sorption,) and chemical environment *(i.e.*, polar effect, oxidation), and the consideration of the nature of the polymers *(i.e.*, homopolymers, copolymers, etc.) require a broad range of indispensable *in-situ* investigations. They aim at providing well-documented thermodynamic properties and phase transitions profiles of polymers under various, coupled and extreme conditions.
