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Issue 41, 2020
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Highly efficient halogen-free flame retardants of thermally-oxidized polyacrylonitrile copolymers containing bio-derived caffeic acid derivatives

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Abstract

Polyacrylonitrile (PAN) is utilized as a precursor for the production of high-performance flame retarding fibers and is also widely used for clothing fibers. Herein, we report the flame retarding properties of catechol-containing PAN copolymers. The comonomer, dihydroxy styrene (DHS), was prepared from bio-derived caffeic acid (CA), which is a key intermediate in the biosynthesis of lignin. P(AN-co-DHS) and P(AN-co-CA) were synthesized by free radical polymerization. The effect of the comonomer structure on the stabilization of PAN copolymers was studied by differential scanning calorimetry, Fourier-transform infrared spectroscopy, and thermogravimetric analysis. The catechol and acid groups of P(AN-co-DHS) and P(AN-co-CA) are effective at lowering the activation energy (Ea) for cyclization of the AN through an ionic mechanism. In CA copolymers, the acid-protected poly(acrylonitrile-co-methyl caffeate) (P(AN-co-MCA)) was found to be the most efficient in terms of Ea, the extent of reaction, and char fraction. The microscale combustion calorimetric analysis after thermal treatment (300 °C, 3 min) showed that the limiting oxygen index and heat release capacity of the P(AN-co-MCA3) fiber were approximately 45% with V-0 of UL rating (superior to Nomex®) and 63 J g−1 K−1, respectively. This research demonstrates a simple, sustainable methodology for the production of environmentally friendly and high-performance flame retardants.

Graphical abstract: Highly efficient halogen-free flame retardants of thermally-oxidized polyacrylonitrile copolymers containing bio-derived caffeic acid derivatives

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Supplementary files

Article information


Submitted
15 Jun 2020
Accepted
23 Sep 2020
First published
24 Sep 2020

Polym. Chem., 2020,11, 6658-6669
Article type
Paper

Highly efficient halogen-free flame retardants of thermally-oxidized polyacrylonitrile copolymers containing bio-derived caffeic acid derivatives

J. Kim, N. You and B. Ku, Polym. Chem., 2020, 11, 6658
DOI: 10.1039/D0PY00854K

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