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International audiencehe dynamic friction coefficients of several polymers have been investigated using a specific rotating device similar to an extruder. The increase in temperature during the measurements made it necessary to develop a theoretical approach in order to interpret the experimental data correctly. The rotation speed and particle shapes were found to have little influence on the friction coefficient. For HDPE and PVC, the friction coefficient decreased slightly with interfacial temperature, whereas it remained constant for PP. The order of magnitude of the friction coefficients was similar to what has already been published in the literature

International audienceLow-molecular weight liquid crystals (LC) have wide technological applications due to their self-assembly in the mesophase. An azomethine nematic monomer based on diglycidyl functionalized mesogenic core and without spacers has been cured with a diamine. The great affinity of LC epoxy to the formation of ordered structures introduces a spatial driving force into the process of curing. Thermal and LC behaviors were investigated by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The nature of the LC phases was confirmed by X-ray diffraction. Rheological experiments were conducted during crosslinking at different shear stresses. The viscosity of the mixture is strongly decreasing by three orders of magnitude when the solid epoxy is melting into a LC phase, and is increasing again due to the curing. Unexpected results were found. Applying a stress during curing had a profound influence on the ordering of the structure. The material becomes isotropic if a small shear stress is applied. Then, the higher the stress is, more ordered the final material is. For the highest stresses, the final material is in a highly ordered, quasi-crystalline, smectic structure