Abstract:Summary
In this study, 5‐hydroxymethyl‐2‐furfural (HMF) was used as a renewable resource for preparing an epoxy curing agent (furan‐based flame retardant, FBF), and a phosphorus‐containing functional group was also incorporated to enhance the flame retardancy of FBF. FBF was easily synthesized, and the total yield was 83%. 2‐Methyl imidazole was chosen as an accelerant to reduce the activation energy for the reaction of FBF with diglycidyl ether of bisphenol A (DGEBA). The DGEBA cured with FBF showed a low gla… Show more
“…By employing 5-hydoxymethyl-2-furfural (HMF) obtained from renewable resources, furan-based FRs constitute a harmless alternative to organophosphorus. Moreover, furan-based flame retardant (FBF) has a significant char yield and a high LOI [ 147 ].…”
Biocomposites reinforced with natural fibers represent an eco-friendly and inexpensive alternative to conventional petroleum-based materials and have been increasingly utilized in a wide variety of industrial applications due to their numerous advantages, such as their good mechanical properties, low production costs, renewability, and biodegradability. However, these engineered composite materials have inherent downsides, such as their increased flammability when subjected to heat flux or flame initiators, which can limit their range of applications. As a result, certain attempts are still being made to reduce the flammability of biocomposites. The combustion of biobased composites can potentially create life-threatening conditions in buildings, resulting in substantial human and material losses. Additives known as flame-retardants (FRs) have been commonly used to improve the fire protection of wood and biocomposite materials, textiles, and other fields for the purpose of widening their application areas. At present, this practice is very common in the construction sector due to stringent fire safety regulations on residential and public buildings. The aim of this study was to present and discuss recent advances in the development of fire-resistant biocomposites. The flammability of wood and natural fibers as material resources to produce biocomposites was researched to build a holistic picture. Furthermore, the potential of lignin as an eco-friendly and low-cost FR additive to produce high-performance biocomposites with improved technological and fire properties was also discussed in detail. The development of sustainable FR systems, based on renewable raw materials, represents a viable and promising approach to manufacturing biocomposites with improved fire resistance, lower environmental footprint, and enhanced health and safety performance.
“…By employing 5-hydoxymethyl-2-furfural (HMF) obtained from renewable resources, furan-based FRs constitute a harmless alternative to organophosphorus. Moreover, furan-based flame retardant (FBF) has a significant char yield and a high LOI [ 147 ].…”
Biocomposites reinforced with natural fibers represent an eco-friendly and inexpensive alternative to conventional petroleum-based materials and have been increasingly utilized in a wide variety of industrial applications due to their numerous advantages, such as their good mechanical properties, low production costs, renewability, and biodegradability. However, these engineered composite materials have inherent downsides, such as their increased flammability when subjected to heat flux or flame initiators, which can limit their range of applications. As a result, certain attempts are still being made to reduce the flammability of biocomposites. The combustion of biobased composites can potentially create life-threatening conditions in buildings, resulting in substantial human and material losses. Additives known as flame-retardants (FRs) have been commonly used to improve the fire protection of wood and biocomposite materials, textiles, and other fields for the purpose of widening their application areas. At present, this practice is very common in the construction sector due to stringent fire safety regulations on residential and public buildings. The aim of this study was to present and discuss recent advances in the development of fire-resistant biocomposites. The flammability of wood and natural fibers as material resources to produce biocomposites was researched to build a holistic picture. Furthermore, the potential of lignin as an eco-friendly and low-cost FR additive to produce high-performance biocomposites with improved technological and fire properties was also discussed in detail. The development of sustainable FR systems, based on renewable raw materials, represents a viable and promising approach to manufacturing biocomposites with improved fire resistance, lower environmental footprint, and enhanced health and safety performance.
“…During the last steps of the carbonization and gas-phase combustion processes of a DGEBA resin, several phenyl-based compounds (e.g., benzene, naphthalene, anthracene, among a few to mention) are produced at high temperatures (800-1000 • C) [41]. Furan-based epoxy polymers are reported to produce a lower amount of high molecular weight compounds, despite an increased residual char, because of the furan structure that reduces the possible cyclization reactions [23,42,43]. Therefore, the combustion of BOMF/MNA and BOMF/MNA_2Si leads to a lower number of products constituting the black soot composition, with respect to DGEBA/MNA and DGEBA/MNA_2Si counterparts.…”
Thermosetting polymers have been widely used in many industrial applications as adhesives, coatings and laminated materials, among others. Recently, bisphenol A (BPA) has been banned as raw material for polymeric products, due to its harmful impact on human health. On the other hand, the use of aromatic amines as curing agents confers excellent thermal, mechanical and flame retardant properties to the final product, although they are toxic and subject to governmental restrictions. In this context, sugar-derived diepoxy monomers and anhydrides represent a sustainable greener alternative to BPA and aromatic amines. Herein, we report an “in-situ” sol–gel synthesis, using as precursors tetraethylorthosilicate (TEOS) and aminopropyl triethoxysilane (APTS) to obtain bio-based epoxy/silica composites; in a first step, the APTS was left to react with 2,5-bis[(oxyran-2-ylmethoxy)methyl]furan (BOMF) or diglycidyl ether of bisphenol A (DGEBA)monomers, and silica particles were generated in the epoxy in a second step; both systems were cured with methyl nadic anhydride (MNA). Morphological investigation of the composites through transmission electron microscopy (TEM) demonstrated that the hybrid strategy allows a very fine distribution of silica nanoparticles (at nanometric level) to be achieved within a hybrid network structure for both the diepoxy monomers. Concerning the fire behavior, as assessed in vertical flame spread tests, the use of anhydride curing agent prevented melt dripping phenomena and provided high char-forming character to the bio-based epoxy systems and their phenyl analog. In addition, forced combustion tests showed that the use of anhydride hardener instead of aliphatic polyamine results in a remarkable decrease of heat release rate. An overall decrease of the smoke parameters, which is highly desirable in a context of greater fire safety was observed in the case of BOMF/MNA system. The experimental results suggest that the effect of silica nanoparticles on fire behavior appears to be related to their dispersion degree.
“…Tannic acid is also in the spotlight concerning its use in the preparation of renewable-based curing agents, alone or combined with other renewable sources [58,87–89]. There are several other biobased curing agents with direct application for ERs industry, such as furan [90,91], gallic acid [92] and itaconic acid [93], isosorbide [94,95], lignin-based curing agents [96], which ultimately will result in the enhancement of the biocharacter of the final ERs, along with some of their properties. A schematic summary of the previously described vegetable oils, as well as other natural sources used to enhance the biocharacter of the curing agent of ER systems, is presented in Figure 5. Figure 5. Renewable sources used in the development of greener curing agents for ERs, based on A.…”
Section: Green-based Epoxy Resins – Sustainable Alternatives To Dgebamentioning
The urgent need to replace fossil resource-based products is considerably increasing in the past few years, resulting in the search for more sustainable materials, with the aim of reducing the wastes from polymer pollution, solving economic and environmental issues. This is even more relevant in industrial fields, where toxic compounds are the basis of their polymeric formulations. Herein is reported the most relevant advances of epoxy resins (ERs) in the past decade, with great emphasis on the replacement of bisphenol A (BPA), leading to the production of renewable-based ERs with good properties. The synthesis of ERs based on renewable sources, such as vegetable oils, phenolic compounds, sugars and the outcome in the material's structure is explored within this review. Emphasis is also given to the use of new biobased curing agents and biofillers to enhance the biocharacter of the ERs.
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