Curing of Styrene-Free Unsaturated Polyester Alkyd and Development of Novel Related Clay Nanocomposites |
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Authors: | I. Mironi-Harpaz M. Narkis A. Siegmann |
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Affiliation: | 1. Department of Chemical Engineering, Technion – IIT, Haifa 32000, Israel;2. Department of Materials Engineering, Technion – IIT, Haifa 32000, Israel |
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Abstract: | Thermoset unsaturated polyesters (UP) are usually obtained by crosslinking of alkyd chains dissolved in an unsaturated reactive monomeric diluent, usually styrene. Recently we found that UP-alkyd chains (without styrene) are intrinsically cured into a crosslinked matrix in the presence of peroxide. The thermal, mechanical, dynamic mechanical and chemorheological properties and the network molecular structure of the crosslinked UP-alkyd are a function of the peroxide content used. All properties change considerably upon the addition of small amounts of peroxide (between 1 and 2%wt.) and change to a lesser extent upon employing higher peroxide concentrations (up to 6%wt.). Due to co-occurrence of crosslinking and scission events, the crosslinked system contains both gel and sol fractions. The sol fraction demonstrates a plasticizing effect on the crosslinked network, affecting the thermal and mechanical properties of the crosslinked polymer. The new materials developed in this work are interesting for utilization in innovative styrene-free UP-alkyd/organo-clay nanocomposites. It was found that inducing high shear levels for prolonged durations promotes the intercalation and exfoliation of the silicate layers, resulting in a better dispersion of clay particles. Crosslinking of the UP-alkyd/organo-clay nanocomposites alters their nanostructure, particularly affected by the peroxide content used. Thus, depending on the content employed, either an exfoliated or a combined intercalated/exfoliated structure may be realized. |
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Keywords: | crosslinking nanocomposite peroxide styrene-free unsaturated polyester alkyd |
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