Papers by Author: S. Etienne

Abstract: The mechanical loss spectra obtained in metallic samples covered with various thin films of arachis oils containing different sulphur concentrations, different consistency, and different oil fractions are observed in the low-temperature range from 180 K to 300 K. The observed mechanical loss spectra are identified as the surface induced mechanical loss phenomena. It is demonstrated that mechanical loss spectra are induced by the presence of oil films on metallic substrates. It is shown that the shape, the peak location, and the generation of the constituent low-temperature peaks can be controlled by the state of the arachis oil films.

Abstract: Dynamic mechanical spectroscopy and differential scanning calorimetry measurements carried out on PVDF films are reported. Several mechanical relaxations are observed around - 100° C, -40° C, and 17° C at 1 Hz, respectively. It is shown that thermomechanical treatments induce variation of material morphology as revealed by calorimetry and low-frequency mechanical spectroscopy. The effect of long-term ageing at room temperature is attributed to reversible melting and formation of small crystallites. The molecular rearrangements involved in ageing at room temperature are characterized by a slow dynamics.

Abstract: Thermal and thermomechanical stability of a crosslinked diacryl photopolymer is examined by means of various experimental techniques. Aging is observed and it is explained by the polymerization which is not completely achieved or/and by liquid glass transition manifestations related to the thermomechanical history of the material.

Abstract: Different degrees of freedom exist in amorphous matter, and are at the origin of relaxation processes (e.g. structural, mechanical). The effect of physical aging of the glassy network on secondary and primary (and cooperative) relaxation is studied. It is shown that if the temperature of aging is below the liquid glass transition temperature and above that of the secondary relaxation, the strength of this last relaxation changes in a non monotonous complex way while the characteristic time of the primary relaxation increases. This feature is explained taking into account the heterogeneous nature of the glassy network. This concept is in agreement with recent inelastic light scattering observations showing that fluctuations of the elastic constants at the nanometric scale are characteristic of the glassy state.