From Formica® to FormiCAN: One-Pot Synthesis of Melamine-based Covalent Adaptable Network Endowed With High Transition Temperature and Fast Stress Relaxation

Abstract

Melamine-based resins are benchmark materials in the field of laminates and composites, and this beyond the world-famous Formica® brand, but these thermosets are not reprocessable and hardly degradable. In relation with the growing field of covalent adaptable networks (CANs) as reprocessable alternatives to thermosets, this study describes a melamine-based CAN containing N,O-acetal exchangeable functions, obtained via a one-pot and solvent-free microwave-assisted process. This material shows good thermo-mechanical properties (T_g = 90 °C, E’_Young up to 1 GPa), a high hydrolytic stability at room temperature (no degradation at pH 1, 7, and 14) but an on-demand degradability (hydrolysis in HCl 1 m at 100 °C). Moreover, this melamine-based CAN exhibits short stress-relaxation times (τ = 30 s at 210 °C) and only very low creep (0.6% at 150 °C after 1 h). This CAN is also easily reprocessable (1.5 h, 170 °C, 10 bars), and no alterations of its properties are observed after 3 reprocessing cycles.