Towards fire-safe, smoke-suppression and recyclable epoxy composite from bio-derived flame retardant

• Published in: Polymer degradation and stability Vol. 227; p. 110894
• Main Authors: Luo, Fubin, Yang, Shuguang, Shi, Zhehang, Zou, Yingbing, Li, Hongzhou
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.09.2024
• Subjects: Bio-based; Epoxy vitrimer; Flame retardancy; Recyclable; Epoxy vitrimer; Flame retardancy; Bio-based; Recyclable
• ISSN: 0141-3910
• DOI: 10.1016/j.polymdegradstab.2024.110894

•Synthesized novel bio-derived flame retardants: CPP-Zn and DDP.•Epoxy vitrimers had a 73.1 % reduction in pHRR and a 41.4 % reduction in THR.•Epoxy vitrimers attained V-0 UL-94, self-extinguishing in 1 s after both ignitions.•The remolded tensile strength can still maintain 72.2 %. Epoxy-based vitrimers appear as a promising alternative to common epoxy materials. Nevertheless, the possibility of epoxy vitrimers in practical applications is limited by their high flammability. In this study, a novel bio-based casein phosphopeptide chelating zinc (CPP-Zn) is purposely developed, specifically designed to serve as a flame retardant and smoke suppressant for epoxy vitrimer, operating through a condensed phase mechanism. To further enhance the fire safety of epoxy resins, DOPO derivative (DDP) is synthesized through grafting with bio-based itaconate and subsequently used as a synergistic flame retardant in combination with CPP-Zn. DDP exhibits gas phase flame retardant mechanism through the release of free radical scavangers generated during combustion. As a result of the combination of condensed and gas phase effect, the composite achieves self-extinguishing within 1 second, attains a V-0 rating in UL-94 testing, and boasts an LOI of 32.3 %. Additional, it shows a remarkable 73.7 % reduction in heat release rate (HRR) and 27.2 % in total smoke production (TSP) compared with neat epoxy vitrimer. The experimental results also evidence that the characteristic features of vitrimers, self-healing and recyclability, have been retained in the prepared flame-retarded composites. The remolded 50D/EST-25Cz is still able to maintain 72.2 % of its tensile strength. This opens promising avenues for the development of highly fire-safe and eco-friendly epoxy resins.