Relaxation of loose agglomerates of magnesium hydroxide in a polymer melt

International audienceThe study of agglomerates of magnesiumhydroxide badly dispersed in an olefinic polymer by means of oscillatory shear flow in the melt indicates that the agglomerates behave as a distinct phase. Optical and rheo-optical measurements carried out on these agglomerates also show that they are wetted by the melt and that they can be easily deformed under shear. However, the relaxation of shape in oscillatory shear is also the trace of the existence of an effective interfacial tension between the agglomerates containing high amounts of filler and the polymer matrix. The analogy with the behavior of polymer blends and the modeling by the Palierne model enables the calculation of such an interfacial tension. The surface free energy of magnesiumhydroxide that can be calculated from this result by a simple mixing law is 95 mN m−1. This value is compared with data from the literature on brucite and similar minerals

Kinetics of PE crystallization

A key issue in the understanding of the nascent polymerisation of ethylene, and on the development of the morphology of polyethylene (PE) particles is the competition between polymer growth and crystallization. In particular, in the case of production of PE in condensed mode cooling, the nascent polymer can be formed in conditions of extreme plastification – in other words, polymer can be formed under conditions where the nascent polymer is in a negligible concentration with respect to the alkanes present in the gas phase of the reactor. We have performed a series of thermal analyses to look at the rates of crystallization under isothermal conditions, and it has been observed that the time scale for the formation of crystals can actually be very long with respect to the times scale for the production of the individual polymer chains. This in turn can have a significant impact on mass transfer rates during the initial stages of polymerisation, as well as on the morphology of the particles as they are formed

Focus on some peculiar behaviors of polymers in the context of additive manufacturing processes

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Some Formulation Effects on Flow Induced Crystallization of Polymers

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Effet des contraintes de mise en oeuvre sur la cristallisation des polymères

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Orientation in self-assembled triblock-copolymers by controlled shearing

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Orientation in self-assembled triblock-copolymers by controlled shearing

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