RESUMO
Poly(ethylene terephthalate) polyester represents the most common class of thermoplastic polymers widely used in the textile, bottling, and packaging industries. Terephthalic acid and ethylene glycol, both of petrochemical origin, are polymerized to yield the polyester. However, an earlier report suggests that polymerization of methoxyterephthalic acid with ethylene glycol provides a methoxy-polyester with similar properties. Currently, there are no established biobased synthetic routes toward the methoxyterephthalic acid monomer. Here, we show a viable route to the dicarboxylic acid from various tree species involving three catalytic steps. We demonstrate that sawdust can be converted to valuable aryl nitrile intermediates through hydrogenolysis, followed by an efficient fluorosulfation-catalytic cyanation sequence (>90%) and then converted to methoxyterephthalic acid by hydrolysis and oxidation. A preliminary polymerization result indicates a methoxy-polyester with acceptable thermal properties.
RESUMO
Recyclable composites are of industrial relevance and benefits the environment, which initiates research towards more sustainable solutions. In this study, a commercial epoxy thermoset, modified by a bio-based additive is used as an infusion resin making recyclable carbon fibre composites. The matrix fractionation process was investigated and optimized with respect to additive & solvent concentration, and temperature. Fully cured carbon reinforced composites were dismantled under the optimum condition and after drying, reinfused, and cured into a new composite, repeated three times on the same carbon fibre material. A decrease in fibre volume fraction and composite performance was found as a number of recyclings were performed. Finally, it was demonstrated that the recycled carbon fibre ply could be reshaped, infused, and cured and thus be applied in new components.
RESUMO
Epoxy-based thermosets are one of the most popular matrix materials in many industries, and significant environmental benefits can be obtained by developing a recyclable variant of this widely utilized material. Incorporation of a bio-based disulfide additive within a commercial epoxy system leads to a cross-linked material that can be fractionated under mild and environmentally benign conditions. The material has been analyzed by FTIR and solid-state NMR. Furthermore, modified epoxy matrices with low additive concentrations are demonstrated to have similar mechanical and thermal properties compared to commercially available benchmarks. Thus, additive formulation and fractionation based on green chemistry principles have been demonstrated, and a recyclable epoxy matrix has been developed.
