Self-extinguishing and transparent epoxy resin modified by a phosphine oxide-containing bio-based derivative

Abstract

A phosphine oxide-containing bio-based curing agent was synthesized by addition reaction between furan derivatives and diphenylphosphine oxide. The molecular structure of the as-prepared bio-based curing agent was confirmed by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. Dynamic mechanical analysis results indicated that with the increase of bio-based curing agent content, the glass transition temperature of epoxy/bio-based curing agent composites decreased, which was related to the steric effect of diphenylphosphine oxide species that possibly hinder the curing reaction as well as the reduction in the cross-linking density by mono-functional N-H. By the addition of 7.5 wt-% bio-based curing agent, the resulting epoxy composite achieved UL-94 V-0 rating, in addition to limiting oxygen index of 32.0 vol-%. With the increase of content for the bio-based curing agent, the peak of heat release rate and total heat release of the composites gradually decreased. The bio-based curing agent promoted the carbonization of the epoxy matrix, leading to higher char yield with good thermal resistance. The high-quality char layer served as an effective barrier to retard the diffusion of decomposition volatiles and oxygen between molten polymers and the flame. This study provides a renewable strategy for fabricating flame retardant and transparent epoxy thermoset.

Key words： epoxy resin; flame retardant; furan derivative; diphenylphosphine oxide

Acknowledgments

This research was supported by the National Natural Science Fundation of China (Grant Nos. 51978002 and 51403004), the Jiaxing Science and Technology Project (Grant No. 2020AD10020) and Postdoctoral Science Foundation of China (Grant No. 2017M610399).

Electronic Supplementary Material

Supplementary material is available in the online version of this article at https://doi.org/10.1007/s11705-021-2042-1 and is accessible for authorized users.

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