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Nunez K.,Foundation for Research and Development in Transport and Energy CIDAUT | Gallego R.,Foundation for Research and Development in Transport and Energy CIDAUT | Pastor J.M.,Foundation for Research and Development in Transport and Energy CIDAUT | Pastor J.M.,University of Valladolid | And 2 more authors.
Applied Clay Science | Year: 2014

A study concerning the use of sepiolite (fibrillar clay) as support of the co-catalyst (methylaluminoxane, MAO) for a process of in situ polymerization was performed. The formation of an ether bond on the clay surface was necessary to achieve the heterogenization of MAO over sepiolite's surface. In this sense, the experimental variables used during the process of grafting of MAO onto sepiolite's surface were studied. Therefore, it was demonstrated that the structure of modified clay and the structure of grafted MAO were kept because they were able to form the active species for polymerization in presence of catalyst and monomer. The results show that the grafting process was the simplest one, i.e., it wasn't necessary for any pre-treatments, i.e., calcination or acidification, due to the special structure of sepiolite; an economic process of MAO heterogenization onto sepiolite's surface was established. Moreover, this procedure may be easily transferred to conventional polymerization processes for obtaining polymers in which the chains are synthesized onto the surface of the filler, maximizing the interaction of matrix-nanofiller and leading to (nano)composites with better performance than the ones obtained by melt intercalation. © 2014 Elsevier B.V. Source


Herrero M.,University of Valladolid | Nunez K.,Foundation for Research and Development in Transport and Energy CIDAUT | Gallego R.,Foundation for Research and Development in Transport and Energy CIDAUT | Merino J.C.,University of Valladolid | And 3 more authors.
European Polymer Journal | Year: 2016

In an effort to understand the influence of the shape and area of the nanoclay type used in the in situ polymerization process, two different types of clays (fibrillar and laminar) were employed to obtain nanocomposites. The preliminary results demonstrated that a needle-like shaped clay promotes higher molar mass and better mechanical properties compared with laminar clay. The ultra-high molecular weight of sepiolite/nanocomposites introduces significant problems with processability. Therefore, a new method of polymerization was designed to include two significant changes. The first change was related to the use of a non-isothermal temperature profile and the second to the addition of an additional amount of non-anchored co-catalyst leading to materials with higher fluidity. © 2015 Elsevier Ltd. All rights reserved. Source

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