N° 37. — Mesures calorimétriques des coefficients de dilatation et de compressibilités absolus

Determination of water intrusion heat in hydrophobic microporous materials by high pressure calorimetry

“…More generally, it is of interest to investigate phases transitions of liquids [7][8][9], as well as melting and crystallization behaviors of synthetic polymers [10] or medicines [11] as a function of the pressure. The application of high pressures in chemistry and physics allow to study condensed matter or inorganic solids under hydrostatic pressure, and to synthesize new materials [3].…”

“…Thus, it requires the design and the construction of a high-pressure unit coupled to a calorimetric measuring system. First self-designed high pressure calorimeters started in the 70s in order to characterize the thermodynamic properties of liquids under pressures up to 400 MPa [7,8]. Since, several other apparatus have been constructed by workers in this field, covering pressures from several tens to several hundreds MPa by means of high pressure pumps [10,[12][13][14][15].…”

“…Both methods provide accurate results [13]. However, the thickness and heaviness of the cell give it a high thermal mass, which therefore makes difficult a temperaturescan to achieve and explains why pressure-scans in isothermal conditions are preferred [7,12]. Second critical point is the fluid transmitting pressure.…”

“…Second critical point is the fluid transmitting pressure. It can be the intrusion liquid itself or it can be another liquid acting as pressuring fluid, such as mercury [7,13], pentane [13], or silicon oil [10]. Anyhow, the intrusion liquid is compressed in a measuring cell in order to achieve a thermal effect detection for a system of constant volume and variable pressure.…”

“…Third important consideration is the analytical method chosen, either static or dynamic. Both operating at constant temperature, in the first one, pressure is changed step-by-step, thus allowing true equilibrium measurements [7], whereas the second one imposes a pressure variation at a constant rate [12]. In this latter case, it supposes a slow enough scanning rate in pressure to ensure a quasi-equilibrium measurement.…”