The Covalent Linking of Organophosphorus Heterocycles to Date Palm Wood-Derived Lignin: Hunting for New Materials with Flame-Retardant Potential

Abstract

Environmentally acceptable and renewably sourced flame retardants are in demand. Recent studies have shown that the incorporation of the biopolymer lignin into a polymer can improve its ability to form a char layer upon heating to a high temperature. Char layer formation is a central component of flame-retardant activity. The covalent modification of lignin is an established technique that is being applied to the development of potential flame retardants. In this study, four novel modified lignins were prepared, and their char-forming abilities were assessed using thermogravimetric analysis. The lignin was obtained from date palm wood using a butanosolv pretreatment. The removal of the majority of the ester groups from this heavily acylated lignin was achieved via alkaline hydrolysis. The subsequent modification of the lignin involved the incorporation of an azide functional group and copper-catalysed azide–alkyne cycloaddition reactions. These reactions enabled novel organophosphorus heterocycles to be linked to the lignin. Our preliminary results suggest that the modified lignins had improved char-forming activity compared to the controls. 31P and HSQC NMR and small-molecule X-ray crystallography were used to analyse the prepared compounds and lignins.

Fragmentation Pathway of Organophosphorus Flame Retardants by Liquid Chromatography–Orbitrap-Based High-Resolution Mass Spectrometry

“…According to the relative abundance ratios of the isotope peaks in the MS 1 spectrum (Figure S5), the type and amount of halogens can be deduced, which facilitates the characterization of the compounds. The two halogenated OPFRs, TDCIPP and T23DBPP, both had distinctive isotope peaks in the MS 1 Isomers are difficult to distinguish in qualitative analysis due to their similar structures and same molecular weights but some isomers differ in the type or abundance of fragment ions, which can be used as tools for further identification. Among the alkyl OPFRs, TnBP and TiBP, TnPP and TiPP are two pairs of isomers (Figure 2b This may be because branched alkanes are more stable than straight-chain alkanes, and when used as substituents, the rearrangement reaction of branched OPFRs mainly occurs in the oxygen atoms connecting the substituent groups, while the energy of straight-chain compounds is dispersed during fragmentation, so the branched compounds are more prone to the formation of [M − 3R + 4H] + , and the proportion of the fragments produced is relatively higher.…”

“…Organophosphorus flame retardants (OPFRs) are common polymer additives employed for flame retardation and plasticization [1][2][3]. In recent years, OPFRs and related degradation products and analogues have been commonly found in water [4], dust [5], sludge [6], and various foods [7][8][9][10][11], and are distributed worldwide [12][13][14].…”

Non-Flammable Epoxy Composition Based on Epoxy Resin DER-331 and 4-(β-Carboxyethenyl)phenoxy-phenoxycyclotriphosphazenes with Increased Adhesion to Metals

“…Another approach is to replace halogen-containing flame retardants with silicon-, phosphorus-, and/or nitrogen-containing ones, as well as their hybrids. Among siliconcontaining flame retardants, silicone resins are used [15], and among phosphorus-and/or nitrogen-containing ones, a mixture of diammonium hydrogen phosphate and urea [16], derivatives of DOPO [17][18][19] and DOPS [20], the product of the reaction of phenyldichlorophosphate with N-hydroxyethyl acrylamide [21], a reaction product of melamine and 2-[(5oxo-6H-phosphanthridin-5-yl)methyl]butanedioic acid [22], etc. However, phosphoruscontaining flame retardants, in particular organophosphates, have neurotoxic and carcinogenic properties, which requires their monitoring in the environment [23].…”

Monitoring Ammonium Polyphosphate (APP) Biodegradation by Acinetobacter nosocomialis D-3 Using DAPI

“…Flame retardants, including halogenated flame retardants (HFRs) and halogen-free flame retardants (HFFRs), have been extensively utilized to mitigate the occurrence of fires and minimize property damage [ 1 ]. While HFRs present significant environmental and health hazards due to their release of toxic smoke and gaseous hydrogen halides during combustion, HFFRs have emerged as rapid alternatives, characterized by their efficiency, non-toxicity, and environmental compatibility [ 2 , 3 ]. Ammonium polyphosphate (APP), a pivotal component of HFFRs, has garnered substantial attention for its notable biological safety profile and cost-effectiveness [ 4 ].…”