Effect of different inorganic filler over isothermal and non-isothermal crystallization of polypropylene homopolymer |
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Authors: | Vera Alejandra Alvarez Claudio Javier Pérez |
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Institution: | (1) Research Institute of Material Science and Technology (INTEMA), Engineering Faculty, National University of Mar del Plata (UNMdP), Av. Juan B. Justo 4302, 7600 Mar del Plata, Argentina; |
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Abstract: | In this study, the effect of several inorganic fillers: silicon oxide (SiO2), nanoclay (C20A), alumina (Al2O3), and calcium carbonate (CaCO3) on the crystallization behavior of polypropylene were analyzed for composites with fixed filler content (5 mass%) prepared
by intensive mixing following by compression molding. In addition, for calcium carbonate, which produces the highest increase
on toughness, PP grafted with maleic anhydride (PP-g-MA) was added to enhance the compatibility. In that case, different content
of particles was used (from 5 to 20 mass%) and the synergic effect of both incorporations was demonstrated. For this purpose,
isothermal and non-isothermal crystallization tests were carried out in the bulk (by differential scanning calorimetry). In
addition, the spherulitic growth was studied (by optical microscopy). Different models were used to predict the relative degree
of crystallinity and several parameters were analyzed. All results indicate that whereas alumina and calcium carbonate acted
as nucleating agents, silica and nanoclay displayed an opposite behavior. The full models that take into account the different
parameters during cooling under isothermal and non-isothermal conditions were used to construct continuous cooling transformation
and time temperature transformation diagrams. Both kind of diagrams provide a fundamental tool to understand the crystallization
behavior of studied composites and are useful to determine the processing conditions. |
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