Preparation of novel biomass humate flame retardants and their flame retardancy in epoxy resin

Abstract

Humic acid (HA), a biomass material with plentiful oxygen‐containing functional groups, showed huge potential to be considered as a promising charring agent in flame retardancy. In this study, this HA was modified with four different metal ions like Fe2+, Mn2+, Al3+, and Cu2+ and finally, introduced into the epoxy resin (EP) to enhance the flame retardancy of the EP and the dispersion of these flame retardants into the EP matrix. When 10 wt% of HA‐Fe and HA‐Mn were incorporated into EP matrix, the limiting oxygen index (LOI) was increased from 21.2% for EP to 26.6 and 25.3% for the EP composites and the peak heat release rate (pHRR) was reduced by 36 and 35.5%, respectively. Such a significant improvement in flame retardancy was attributed to the catalytic charring of HA in the presence of metal ions, which ultimately increased the residual char formation and produced compact char layers during the combustion process to retard the transfer of heat and combustible gases between the EP composites and the flame zone. Finally, this kind of application provided a feasible way for the development of an environmentally friendly flame retardant with high efficiency, which improved the fire safety of EP matrix.

Detailed Thermal, Fire, and Mechanical Study of Silicon-Modified Epoxy Resin Containing Humic Acid and Other Additives

“…HA positively affects the thermal behavior of the epoxy systems, because of the generation of a stable aliphatic char under inert atmosphere at high temperatures, resulting in an increase of the residue as compared to E. , In fact, the addition of HA (i.e., EAP_HA and E_HA samples, respectively, Table S3) leads to a faster decomposition of the resin chains, due to the acidic features of HA, which favor the char formation during the pyrolysis process. , Notably, the aromatic nature of HA allows the production of a more stable char during the degradation of E in air atmosphere, preventing the full oxidation of the resin with the formation of low-molecular-weight molecules ,, (Table S3, Section ). In addition, the combined presence of HA and each of the other additives within the resin further improves the thermal behavior: in fact, the charring phenomenon is further supported by the presence of AP-modified DGEBA moieties containing siloxane groups that show a weak acidic character.…”

“…The interaction of hybrid moieties, phosphorus flame retardants, and nitrogen additives to form a stable char and resulting in an improved fire performance is well known for other polymeric systems, though, based on the best knowledge of the authors, this is the first time that a biowaste (i.e., HA) becomes a crucial component in the flame retardance of an epoxy-based system. ,,, …”

“…Liu et al chelated HAs with four different metal ions and incorporated them into a modified DGEBA resin to enhance its flame retardance. In particular, as a result of the incorporation of 10 wt % of HA-Fe and HA-Mn into the epoxy matrix, the limiting oxygen index (LOI) increased from 21.2% for pristine resin to 26.6 and 25.3%, respectively; meanwhile, the pHRR was reduced by 36 and 35.5%, respectively . Despite HAs being used as a charring agent following Liu et al, as far as we know, no self-extinguishing materials using HA have been developed so far.…”

Effect of Bio‐Based Cobalt Alginate on the Fire Safety and Mechanical Properties for Epoxy Resin

“…EP exhibits a smooth and flat surface ( Figure a), reflecting a surface of a typical thermosetting material. [ 54 ] On the other hand, EP/Cobalt Alginate composites show fractured and rough micromorphologies with the agglomeration phenomenon (Figure 9d′′). The phenomenon indicates that cobalt alginate exhibits a worse dispersion and compatibility in EP matrix with the more additive contents of cobalt alginate; therefore, the obvious reduction of tensile strength is caused by the addition of cobalt alginate.…”

A facile method for synthesis of novel phenyl phosphates flame retardants and their application in epoxy resin

“…Epoxy resin (EP) has become an extremely important thermosetting resin material due to its excellent mechanical and chemical properties and is applied as a highperformance material in biomedicine, aerospace, and engineering composite materials, etc. [1][2][3][4] However, EP suffers fatal drawbacks of its inherent high flammability and the release of lots of heat and dense smoke in the process of combustion, which requires suitable flame retardants to expand its commercial and industrial applications. 5,6 Traditionally, industrial products usually increase the flame retardancy of their materials by introducing a few halogenated flame retardants.…”