Abstract
Long-chain polyamide covalent adaptable networks with high strength and short relaxation times were prepared based on a renewable ethylene brassylate and disulfide exchange.
Highlights
Unlike thermoplastics that can be recycled and/or reprocessed when they reach their end-of-life, the development of circular thermosets is more challenging
Seeking for a simpler and more sustainable alternative towards longchain PA Covalent adaptable networks (CANs), we focused on disulfides as an intrinsically reactive bond,[31,32] that can be activated under mild conditions.[33]
When the same reaction conditions were applied to the EB/ Cys/TAEA mixtures with varying the Cys : TAEA molar ratio (20 : 80 to 80 : 20), networks with lower than expected gel content (89–81%) were obtained and the Fourier transform infrared spectroscopy (FTIR) spectra showed some unreacted EB monomer left, Fig. S1.† Higher gel content values could not be achieved by increasing the temperature to 120 °C or by extending the reaction time (48 h) at 100 °C
Summary
Unlike thermoplastics that can be recycled and/or reprocessed when they reach their end-of-life, the development of circular thermosets is more challenging. Thermosets reach their endof-use once they are damaged, as the permanently crosslinked network does not allow reprocessing by conventional techniques, and incineration, landfill or use as lower value additives commonly follow. Associative CANs are thermally reprocessable and chemical recycling of the pristine synthons is possible in certain cases. Their principle is the activation of exchange reactions between dynamic bonds that overall keep the crosslink density of the network constant, but allow it to flow and rearrange its topology at high temperature. CANs meld the features of classical thermosets such as chemical resistance and dimensional stability with reprocessability, and in some cases self-healing ability and chemical recycling,[2,3,4,5,6,7] all highly attractive features for many applications.[8]
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