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. 2020 Dec 4;5(49):32084-32093.
doi: 10.1021/acsomega.0c05146. eCollection 2020 Dec 15.

Highly Efficient, Environmentally Friendly Lignin-Based Flame Retardant Used in Epoxy Resin

Peng Dai  1 , Mengke Liang  1 , Xiaofeng Ma  1   2 , Yanlong Luo  1   2 , Ming He  1   2 , Xiaoli Gu  3 , Qun Gu  4 , Imtiaz Hussain  1 , Zhenyang Luo  1   2
Affiliations

Highly Efficient, Environmentally Friendly Lignin-Based Flame Retardant Used in Epoxy Resin

Peng Dai et al. ACS Omega. .

Abstract

We prepared novel flame retardants with concurrent excellent smoke-suppression properties based on lignin biomass modified by functional groups containing N and P. Each lignin-based flame retardant (Lig) was quantitatively added to a fixed amount of epoxy resin (EP), to make a Lig/EP composite. The best flame retardancy was achieved by a Lig-F/EP composite with elevated P content, achieving a V-0 rating of the UL-94 test and exhibiting excellent smoke suppression, with substantial reduction of total heat release and smoke production (by 46.6 and 53%, respectively). In this work, we characterized the flame retardants and the retardant/EP composites, evaluated their performances, and proposed the mechanisms of flame retardancy and smoke suppression. The charring layer of the combustion residual was analyzed using SEM and Raman spectroscopy to support the proposed mechanisms. Our work provides a feasible method for lignin modification and applications of new lignin-based flame retardants.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
Infrared spectra of Lig-P, Lig-M, and Lig-F.
Figure 2
Figure 2
XPS spectra along with the elemental composition of Lig-P, Lig-M, and Lig-F.
Figure 3
Figure 3
TGA (A) and DTG (B) curves for Lig-P, Lig-M, and Lig-F under nitrogen.
Figure 4
Figure 4
(A) TGA and (B) DTG curves: (1) EP, 10%-Lig-P/EP, 10%-Lig-M/EP, and 10%-Lig-F/EP and (2) 2%-Lig-F/EP, 4%-Lig-F/EP, 6%-Lig-F/EP, 8%-Lig-F/EP, and 10%-Lig-F/EP composites under a N2 atmosphere at a heating rate of 20 °C/min.
Figure 5
Figure 5
(A) Heat release rate, (B) total heat release curves, (C) smoke production rate, (D) and total smoke production rate of typical EP, 10%-Lig-P/EP, 10%-Lig-M/EP, and 10%-Lig-F/EP composites (100 × 100 × 3 mm3) at a heat flux of 35 kW/m2.
Figure 6
Figure 6
Digital photos of composites for (A) EP, (B) 10%-Lig-P/EP, (C) 10%-Lig-M/EP, and (D) 10%-Lig-F/EP after UL-94 testing.
Figure 7
Figure 7
SEM images of the residue char: (A1, A2) for the EP composite; (B1, B2) for the 10%-Lig-P/EP composite; (C1, C2) for the 10%-Lig-M/EP composite; and (D1, D2) for 10%-Lig-F/EP composites.
Figure 8
Figure 8
Raman spectra of the carbon residue for (a) EP, (b) 10%-Lig-P/EP, (c) 10%-Lig-M/EP, and (d) 10%-Lig-F/EP composites.
Scheme 1
Scheme 1. Synthetic Route of Modified Lignin (Lig-M and Lig-F)
See this image and copyright information in PMC

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