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Catalyzed synthesis and characterization of a novel lignin-based curing agent for the curing of high-performance epoxy resin

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Version 2 2024-06-06, 10:20
Version 1 2017-08-03, 11:30
journal contribution
posted on 2024-06-18, 03:01 authored by S Nikafshar, Omid ZabihiOmid Zabihi, Y Moradi, M Ahmadi, S Amiri, Minoo NaebeMinoo Naebe
In this study, lignin, an aromatic compound from the forestry industry, was used as a renewable material to synthesize a new aromatic amine curing agent for epoxy resin. Firstly, lignin was separated from black liquor and hydroxyl groups were converted to tosyl groups as leaving groups. Then, primary amination was conducted using an ammonia solution at high pressure and temperature, in the presence of a nano-alumina-based catalyst. The structure of the nanocatalyst was confirmed by FT-IR, ICP, SEM, and XPS analyses. According to the FT-IR spectra, a demethylation reaction, the substitution of hydroxyl groups with tosyl groups, and then an amination reaction were successfully performed on lignin, which was further confirmed by the 13 C NMR and CHNS analyses. The active hydrogen equivalent of aminated lignin was determined and three samples with 9.9 wt %, 12.9 wt %, and 15.9 wt % of aminated lignin, as curing agents, were prepared for curing the diglycidyl ether of bisphenol A (DGEBA). The thermal characteristics of the curing process of these epoxy samples were determined by DSC and TGA analyses. Moreover, the mechanical performance of the cured epoxy systems, e.g., the tensile strength and Izod impact strength, were measured, showing that in the presence of 12.9 wt % aminated lignin, the mechanical properties of the aminated lignin-epoxy system exhibited the best performance, which was competitive, compared to the epoxy systems cured by commercial aromatic curing agents.

History

Journal

Polymers

Volume

9

Article number

ARTN 266

Pagination

1 - 16

Location

Switzerland

Open access

  • Yes

ISSN

2073-4360

eISSN

2073-4360

Language

English

Publication classification

C1.1 Refereed article in a scholarly journal

Copyright notice

2017, by the authors

Issue

7

Publisher

MDPI