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Recyclable Epoxy Resin via Simultaneous Dual Permanent/Reversible Crosslinking Based on Diels–Alder Chemistry
Author(s) -
Puyadena Maddalen,
Calafel Itxaso,
González de San Román Estíbaliz,
Martin Loli,
González Alba,
Irusta Lourdes
Publication year - 2021
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.202100146
Subject(s) - epoxy , curing (chemistry) , differential scanning calorimetry , polymer chemistry , diamine , amine gas treating , thermosetting polymer , materials science , fourier transform infrared spectroscopy , composite material , chemistry , organic chemistry , chemical engineering , physics , engineering , thermodynamics
Taking advantage of the reversible Diels–Alder (DA) reaction, a simple strategy to obtain recyclable epoxy resins is presented. For this purpose, blends of furan‐functionalized and nonfunctionalized epoxy resin are prepared. After the addition of diamine and bismaleimide, blends are heated at 150 °C for 5 min, where the permanent amine/epoxy reaction has taken place and upon cooling to room temperature the reversible DA reaction has happened, giving rise to a dual permanent/nonpermanent network. Both reactions are confirmed by Fourier‐transform infrared (FTIR) and 13 C‐crosspolarization, magic‐angle spinning (CP/MAS) nuclear magnetic resonance (NMR). Modulated differential scanning calorimetry (MDSC) shows that the epoxy/amine and bismaleimide/amine curing reaction take place, after the DA reaction, simultaneously with the retroDA reaction and before the bismaleimide homopolymerization. Therefore, under the appropriate curing conditions, the Michael's addition and the bismaleimide homopolymerization do not avoid the formation of a hybrid network, as stated in other reports. The reversibility of the DA reaction in three consecutive cycles is confirmed by DSC. Finally, the dual‐cured sample is reprocessed three times without significant loss of mechanical properties.