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Summary: An improved gas phase reactor system has been designed and tested in order to study heat transfer in gas phase olefin polymerisation on supported catalysts. It is shown that temperature rise in a fixed bed configuration is highly dependent on the flow rate of gas, with higher outlet gas temperatures being observed at higher flow rates. In addition it is shown that the shape of the rate curve is dependent on the initial conditions of the reaction, suggesting that the mechanism of particle fragmentation depends to a certain extent on the start-up of the reaction.

International audienceThe dispersion of Mg(OH)2 agglomerates at low concentration in a polymer melt was investigated in a transparent counter-rotating shear cell. The influence of the viscosity of the matrix, the initial agglomerate size and the infiltration of the matrix was evaluated. Mg(OH)2 agglomerates have a low cohesion and a fractal structure. Two dispersive mechanisms already mentioned in the literature were identified: erosion and rupture. Critical conditions for rupture were measured and particle size analysis was performed in order to determine the kinetics of erosion. The infiltration of the matrix, which depends on the viscosity, was found to play a key role on dispersion mechanisms. In contrast to previous works, infiltration is more important with the high viscosity matrix. In infiltrated matrix, rupture was found to occur firstly through plastic deformation of the infiltrated agglomerate, and then the agglomerates split into small fragments. In the low viscosity matrix, fragments produced either by rupture or erosion are small aggregate