Effect of nano–particles geometry on the recovery of polymer nano–composites in the melt stateکنفرانس بین المللی فرآورش پلیمرها
The effect of nano–particle geometry on the recovery of nano–composites based on ethylene vinyl acetate (EVA) copolymer is investigated. The main objective of the work is to discuss how the presence of a filler network, which is formed by inter–particle interactions, influence the structural recovery of polymers in the melt state. Different nano–particles like calcium carbonate (CaCO3) and clays were used at different concentrations between 2.5 and 15% by weight. First, by using a complete set of rheological analysis, three different phenomena were studied: the appearance of a solid–like behavior in the linear domain, the limit of linear viscoelasticity and non–linear behaviour. Then, in order to examine the structure recovery after a rest time, the same set of behavior was studied on pre–sheared samples. The experiments revealed that the effect of nano–particles is much more profound for anisometric particles. The differences can be attributed to the ability of anisometric particles to form a fractal structure which dominates the rheological properties, while spherical particles are not able to create such a network structure. On the other hand, recovery experiments revealed that while nano–composites containing spherical particles show relatively the same behavior in subsequent tests, the nano effect for anisometric particles decreased significantly after the first test. The recovery results are also in accordance with the filler–network mechanism and the reduction of nano effect for anisometric particles was related to the breakdown of the filler network. Our interpretations regarding the percolated network were validated by structural analysis like TEM and SEM<\div>
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