(167ad) Thermomechanical Characterization of Recyclable Diels-Alder Epoxies Loaded with TiN Nanoparticle

Typically, epoxies are strong but non-recyclable and difficult to remove. Recyclable epoxies were crosslinked by a Diels-Alder (DA) reaction between maleimide and furan functional group containing adducts, synthesized from polyetheramines and epoxide precursors. Different epoxy architectures (4-arms or 6-arms) and different stoichiometric ratios of furan to maleimide were studied. Titanium nitride (TiN) nanoparticles with significant visible light absorption were added for local, instant triggering of the rDA reaction by a high-intensity light source. Calorimetric and mechanical measurements of the glass transition were made. In addition to the low-temperature glassy phase, rheometric measurements detect a rubbery plateau at moderate temperature followed by a rapid decrease in modulus indicative of liquid behavior due to rDA reaction depolymerizing the network. Lowering the temperature regenerates the network due to the fDA reaction with a return of glassy and rubbery plateaus upon cooling. Changing the stoichiometric amounts of furan to maleimide can be used as an optimization parameter with 3D printing in mind. Maleimides typically homopolymerize near 150°C, so optimizing chemistry with these reversible DA systems requires additional attention.