Reprocessable flame retardant amino-ester thermoset

Abstract

Polymeric materials are vital in modern life due to their versatility and cost-effectiveness. Thermosets are highly valued for their exceptional durability, chemical resistance, and mechanical strength. Despite these advantages, challenges such as enhancing fire safety and recyclability persist. Covalent Adaptable Networks (CANs) offer a promising solution, providing a sustainable platform for materials with self-healing and recyclable properties. This study addresses these challenges by developing innovative CANs through Aza-Michael addition and retro-addition chemistry. Amino-ester networks (AE) composed of m-Xylenediamine, and pentaerythritol triacrylate were manufactured while simultaneously incorporating phosphorus-based flame retardant (FR) additives synthesized in situ. A systematic characterization of physical, thermal, flame-retardant, and reprocessability properties was performed for the novel AE. Ten thermomechanical recycling cycles were performed for the AE to demonstrate the robustness of the new material, showing no degradation or changes in its physical, thermal, and flame-retardant properties. The chemistry involved in the recyclability was characterized via Raman Spectroscopy. The thermoset containing 0.7 wt% phosphorus (P) exhibits self-extinguishing behavior, achieving a V-0 rating. Compared to the material without flame retardant additives, the presence of the new in-situ FR (3.6 wt% P) allows for a significant reduction in total heat release (43%) and total smoke release (46%). The new FR molecule was also compared with a similar, previously reported molecule (EDA-bis-TEPT) and showed significantly better flame-retardant properties. Furthermore, the potential of these innovative thermosets was explored for applications such as fire-safe carbon fiber-reinforced composites, indicating a promising direction for developing sustainable and high-performance polymer materials.