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In this work, apigenin was chosen as a raw material to synthesize a novel epoxy monomer (DGEA), while the bio-based epoxy resin was further obtained after curing with 4,4′-diaminodiphenylmethane (DDM). The control samples were prepared by curing diglycidyl ether of bisphenol A (DGEBA) with DDM. The non-isothermal differential scanning calorimeter (DSC) method was utilized to further investigate the curing behavior and curing kinetics of the DGEA/DDM system. Despite no flame retardant active elements, the DGEA/DDM thermoset still exhibited exceptional anti-flammability. Specifically, the DGEA/DDM thermoset reached a V-0 rating in the UL-94 test and owned a high limiting oxygen index (LOI) value of 37.0%, while DGEBA/DDM resins were consumed completely in the vertical combustion test with a low LOI of 23.0%. Furthermore, the microscale combustion calorimetry (MCC) results manifested that compared with DGEBA/DDM resins, both PHRR and THR values of the DGEA/DDM resins were dropped by 84.0% and 57.6%, respectively. Additionally, the DGEA/DDM resin also presented higher storage modulus and tensile strength compared with DGEBA/DDM one. Particularly, in contrast with that of the cured DGEBA/DDM one (156 °C), the DGEA/DDM thermoset displayed an extremely high glass transition temperature (232 °C). This study breaks new ground on how to produce bio-based monomers with aromatic structures and achieve high-performance thermosetting polymers. [ABSTRACT FROM AUTHOR]

Wildfires have been recognized as a natural incident in some forests, however, fire season is now more severe and extensive, even in tropical rainforests in which fire could have damaging impacts. A hydrogel is a 3-D polymeric structure encompassing cross-linked and hydrophilic macromolecules. In comparison with water, hydrogels have shown some superiorities in terms of water-binding, cooling, and sealing, which make them be applied in forest fire prevention programs for improving fire-extinguishing performance. In this study, an environmentally friendly phosphorus-modified methylcellulose/silica hybrid hydrogel was prepared based on the modified methylcellulose by 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide–itaconic acid (DOPO-ITA) and silica nanoparticles. In the fire prevention experiments, the grass treated with the methylcellulose@DOPO-ITA@silica hybrid hydrogel shows self-extinguishing behavior, whereas those treated with ordinary water or methylcellulose hydrogel can be easily ignited after one week. In the firefighting experiments, the methylcellulose@DOPO-ITA@silica hybrid hydrogel displays a much shorter extinguishing time and lower consumption volume than ordinary water and the methylcellulose@DOPO-ITA hydrogel. This work presents an environmentally friendly, non-toxic, and biodegradable cellulose-based hybrid hydrogel for the fire prevention and firefighting of wildfires. [ABSTRACT FROM AUTHOR]

Fabrics with high flame-retardancy have been extensively applied for numerous applications including textile, garments, automobile industries, pants, shirts, suits bed sheets, and indoor decorations. Coatings consisting of ammonium hexametaphosphate (NH4-HMP), laponite (LAP), and hexadecyltrimethoxysilane were synthesized through sol–gel method; they were then employed on the cotton fabrics to enhance their hydrophobicity and flame retardancy. The influences of LAP concentration on fire-retardancy of the samples were evaluated. The combustion behavior, morphological structures, thermal stability, and hydrophobic properties of the cotton fabrics were studied. Results indicated the excellent flame retardant property of the treated cotton fabrics as they immediately extinguished upon removal of the flame source. The limiting oxygen index of the treated cotton was enhanced to 29% in comparison to that of the pure one (19.5%). The findings also indicated that a higher concentration of LAP is useful for improving flame retardancy of the coated substrate. In addition, the hydrophobicity of the fabric surface was measured by a water contact angle of 138°, while its superoleophilicity was assessed by an oil contact angle of 0°. To separate water–oil mixtures, the as-prepared cotton sample was utilized as operative substances. Overall, in this study a facile technique is provided for preparing cotton fabrics with considerably enhanced flame retardancy and superior self-cleaning features toward different fluids making them suitable as a promising candidate for water–oil separation. [ABSTRACT FROM AUTHOR]

In the current study, Zeolitic Imidazole Framework-8 (ZIF-8) was in situ grown on the surface of cellulose fibers and the ZIF-8@cellulose composite aerogels were fabricated by a freeze-drying method. The flame-retardant, thermal and mechanical characteristics of the cellulose-based aerogels were investigated. SEM images indicated that ZIF-8 was evenly deposited on the surface of the cellulose fibers in the aerogel owing to formation of hydrogen bonding with cellulose molecules. The addition of ZIF-8 enhanced thermal stability and flame retardancy of the host cellulose aerogel. The peak of heat release rate of the ZIF-8@cellulose-3 composite aerogel exhibited a drastic decline from 128 W g−1 to 63 W g−1 and the total heat release from 25.9 kJ g−1 to 14.8 kJ g−1. In the UL-94 vertical burning test, the samples showed self-extinguishing behavior. Additionally, ZIF-8 induced a dramatic enhancement in the mechanical properties of the host cellulose. Specifically, the compressive stress of the ZIF-8@cellulose composite aerogel showed a significant increase from 0.45 to 34.80 MPa. Moreover, the ZIF-8@cellulose composite aerogel can selectively remove the organic pollutants from water and adsorb a wide range of liquid oils with considerable capacities. The current study presented a feasible approach to synthesis of strong and flame-retardant cellulose-based aerogels for waste water purification. [ABSTRACT FROM AUTHOR]

• A syringaldehyde derived epoxy resin monomer (SA-TAG-EP) was developed. • The bio-based epoxy system showed a record T g of 224 °C, high strength and modulus. • The bio-based epoxy system showed satisfactory intrinsic flame retardancy. Due to increasing environmental concerns, global warming, and the decline of oil reservoirs, the use of bio-epoxy resins derived from sustainable resources is recommended. The development of bio-based epoxy resins with considerable thermal stability, mechanical strength, and appropriate intrinsic flame retardant potential is highly demanded. In this study, a new Schiff-based epoxy monomer, triglycidyl ether of syringaldehyde (SA-TAG-EP), was synthesized from renewable syringaldehyde. After the 4,4′-diaminodiphenylmethane (DDM)-based curing process, an intrinsically flame-retardant resin (SA-TAG-EP/DDM) with C, H, N, and O elements was achieved. SA-TAG-EP/DDM showed higher glass transition temperature (224.9°C) and greater mechanical strength, including a tensile strength of 66.8 MPa and an elongation at break of 3.91%, compared to petroleum-based bisphenol A epoxy thermoset. It also passed the V-0 flammability rating in the UL-94 test and exhibited a 38.5% limiting oxygen index, 48.9% char yield under N 2 , and a lower peak heat release rate than that of petroleum-based bisphenol A epoxy thermoset. We proposed a simple and sustainable route for the synthesis of Schiff base epoxy compounds from biomass-derived resources, which demonstrates significant mechanical properties and increased flame retardant potential. [ABSTRACT FROM AUTHOR]

A fully bio-based epoxy thermosetting network was prepared by curing a renewable luteolin-derived epoxy resin (DGELU) with a furan-derived hardener, 5, 5′-methylenedifurfurylamine (DFA). For comparison, a control sample was prepared by curing the petroleum-based commercial epoxy diglycidyl ether of bisphenol A (DGEBA) with a petroleum-based hardener, 4, 4′-diaminodiphenylmethane (DDM). The glass transition temperature (T g) was found to be 216 °C for the cured DGELU/DFA, which was 67 °C higher than that of the cured DGEBA/DDM. The storage modulus at 30 °C and the tensile strength of the cured DGELU/DFA were 82.5 % and 23.2 % higher than those of the cured DGEBA/DDM. The benzopyrone unit of the luteolin structure was conducive to exceptional charring, and the char yield for thermal decomposition in the nitrogen of the cured DGELU/DFA was 3.2-fold higher than that for the cured DGEBA/DDM. As expected, the cured DGELU/DFA displays a relatively high limiting oxygen index (LOI) of 38.0 % and a UL-94 V-0 classification, whereas the petroleum-based counterpart exhibited a much lower LOI of 24.0 % and no classification in the UL-94 test. An in-vitro cytotoxicity study indicated that the cured DGELU/DFA showed no cytotoxic effect against normal fibroblast cells after 24 and 72 h. Because of these fascinating features, the DGELU/DFA thermosetting network was deposited onto wood surfaces for evaluation as a flame-retardant coating. Compared with the wood treated using the cured DGEBA/DDM coating, wood coated with the cured DGELU/DFA showed a super fire-safe property that could lead to a 55.8 %, 12.4 %, and 11.5 % decrease in peak heat release rate (PHRR), total heat release (THR), and total smoke production (TSP), respectively. An anti-flammable, high strength and non-toxic bio-derived epoxy thermosetting network for highly safe epoxy coating applications has been developed. • A fully bio-based epoxy thermoset (DGELU/DFA) has been prepared from luteolin. • DGELU/DFA showed higher Tg and tensile strength than its petroleum-based counterpart. • DGELU/DFA displayed anti-flammability with a high LOI of 38.0 % and a UL-94 V-0 grade. • DGELU/DFA showed no cytotoxic effect against normal fibroblast cells. • DGELU/DFA is suitable as a flame-retardant and eco-friendly coating for wood. [ABSTRACT FROM AUTHOR]

• A vanillin-derived cyclotriphosphazene-cored triazole compound (HHCTP) was synthesized. • The HHCTP-modified epoxy achieved a UL-94 V-0 classification and an LOI of 31.5%. • The addition of HHCTP preserved the thermo-mechanical properties of epoxy resins. A vanillin-derived cyclotriphosphazene-cored triazole compound (HHCTP) was successfully synthesized as a flame retardant for epoxy thermosets with high efficiency while preserving their thermomechanical properties. 1H- and 31P nuclear magnetic resonance (NMR), as well as Fourier Transform infrared (FT-IR), were applied to confirm the molecular structure of HHCTP. The dynamic mechanical analysis (DMA) measurements demonstrated that the introduction of HHCTP improved the storage modulus of the epoxy composites but decreased the glass transition temperature. The epoxy thermoset containing 7.5 wt% HHCTP (EP/HHCTP-7.5) achieved a UL-94 V-0 classification and an LOI of 31.5%, manifesting its outstanding flame-retardant efficiency. In addition, the cone calorimeter results showed that the total heat release (THR) and the peak value of the heat release rate (PHRR) of EP/HHCTP-7.5 were decreased by 35.6% and 50.0%, respectively, in comparison with those of the unmodified epoxy. To further study the flame retardant mechanism of HHCTP, pyrolytic gas species were detected utilizing thermogravimetric-infrared spectroscopy (TG-FTIR). In addition, the microstructure of the char residues was analyzed via X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM) techniques. The phosphazene groups in HHTCP clearly stimulated the production of an intumescent, compact, and strong char layer, which improved the flame retardancy of the DGEBA matrix during burning, according to the SEM data. As a result, the underlying components were protected from further degradation and combustion, resulting in effective flame retardancy of the DGEBA thermoset. [ABSTRACT FROM AUTHOR]

Organic-inorganic hybrid flame retardant technology integrates independent ingredients into a whole, thus showing advantage of simultaneous improvement in flame retardant, smoke suppressant and mechanical properties of polymers over traditional flame retardants. In this work, a novel organic-inorganic hybrid flame retardant denoted as IR-MOF-3-Mel was synthesized by covalent hybridization of isoreticular metal-organic framework-3 (IR-MOF-3) with melamine. A relatively low amount of IR-MOF-3-Mel nanoparticles dramatically decreased the fire risk of epoxy resin (EP). Specifically, the EP with only 2.0 wt% of IR-MOF-3-Mel achieved a limiting oxygen index (LOI) of 30.5% as well as a UL-94 V-0 classification, whereas its counterpart with 2.0 wt% of IR-MOF-3 showed a LOI of 25.0% and no classification in UL-94 test. Furthermore, the peak heat release rate, total heat release and smoke production rate of the EP with 2.0 wt% of IR-MOF-3-Mel was declined by 74.0%, 71.4% and 35.6%, respectively, compared to neat EP. Additionally, the glass transition temperature, the tensile strength, and the young's modulus were 11 °C, 38%, and 27% higher than those of neat EP, respectively. The flame retardant mechanism analysis clarified that IR-MOF-3-Mel contributed to formation of a char layer with a high level of thermal resistance and graphitization which accounted for significantly reduced fire risks. Image 1 • With only 1.5 wt% of IR-MOF-3-Mel, the EP composite achieved a UL-94 V-0 rating. • 2.0 wt% of IR-MOF-3-Mel leads to an unprecedented reduction in both PHRR (−74.0%) and THR (−71.4%) of epoxy composites. • IR-MOF-3-Mel hybrid also shows good smoke suppression effect. • 2.0 wt% of IR-MOF-3-Mel improves the tensile strength by 38% compared to neat EP. [ABSTRACT FROM AUTHOR]

A coating comprising graphene oxide (GO) and oleic acid (OA)-modified zeolitic imidazolate frameworks-8 (ZIF-8) was deposited to cotton fabrics with the aim of obtaining a flame-retardant, self-cleaning and superhydrophobic features. SEM images showed a rough surface with hierarchical structure for GO-cotton/ZIF-8. Existence of the coating on the surface of cotton fabrics was proved by XPS spectra and FT-IR characterization. Surface of the GO-cotton/ZIF-8 fabrics achieved a remarkable degree of thermal and mechanical stability and superhydrophobicity. The results from a flame test demonstrated a protective effect of the coating on the cotton fabrics against fire. Additionally, the GO-cotton/ZIF-8 cotton showed superior self-cleaning ability and oil/water separation performance due to its superhydrophobic surface. Thus, it has a wide range of potential applications in military equipment and outdoor clothing. • Flame-retardant and superhydrophobic coating was deposited on cotton fabric. • The coated cotton fabric exhibited outstanding flame retardancy. • The PHRR and the THR of the coated cotton fabric were reduced by 30% and 53%. • The coated cotton fabric showed oil/water separation efficiency higher than 92%. [ABSTRACT FROM AUTHOR]

Cotton fabrics are prone to ignite fire accidents as well as breed bacteria and fungi, which have hampered their applications in the field of packaging and home decorations. Guanazole complexes with silver and zinc ions were deposited to cotton fabrics through self-assembly to prepare the flame-retardant and antibacterial cotton fabrics. The effect of the guanazole-metal complexes on the morphological structure, flammability and thermal degradation of cotton fabrics was studied by field emission scanning electron microscopy, limiting oxygen index (LOI), UL-94 vertical burning test, and thermogravimetric analysis. The antibacterial and antifungal activities of the coated fabrics were evaluated as well. The guanazole-zinc and guanazole-silver treated cotton fabrics showed a high LOI of 29.5% and 27.5%, respectively. In the vertical burning test, both the guanazole-zinc and guanazole-silver treated cotton fabrics self-extinguished when removing the ignition source, displaying a UL-94 V-0 classification, while the untreated one and the guanazole-treated one burned out. Thermogravimetric analysis results confirmed that the guanazole-metal complexes promoted the thermal decomposition of cotton and thus improved the char yield significantly. Micro-scale combustion calorimeter measurements clarified that the guanazole-zinc and guanazole-silver treated cotton displayed dramatically decreased peak heat release rate (64.4% and 59.1%, respectively) and total heat release (26.4% and 14.8%, respectively) in comparison to the untreated one. The significantly improved flame retardancy of guanazole-metal complexes treated cotton fabrics could be attributed to their enhanced charring capability that blocked flammable volatiles into flame zone. The treated cotton fabrics with guanazole-metal complexes exhibited better antibacterial capacity against Staphylococcus aureus and Escherichia coli than the untreated and guanazole-treated ones. Furthermore, the guanazole-silver treated cotton fabrics also showed good antifungal activity against Penicillium, Fusarium chlamydosporum and Aspergillus niger. Image 1 • Guanazole-metal complex was used to simultaneously improve flame retardant and antibacterial property of cotton fabrics. • Limiting oxygen index increases to 27.5% for guanazole-silver treated cotton from 19.5% for untreated one. • The peak heat release rate of guanazole-silver treated cotton was reduced by 59% compared to untreated one. • The guanazole-silver treated cotton showed self-extinguishing behaviors owing to promotion of char formation. • The guanazole-silver treated cotton showed good antibacterial and antifungal ability. [ABSTRACT FROM AUTHOR]

Flexible polyurethane (FPU) foam as a primary softening material is utilized in soft furnishings of upholstered mattresses and furniture. High flammability of this soft furnishing material usually leads to residential fires, causing severe fatalities. In the present study, we proposed a bio-based and environmentally-friendly flame retardant multilayered coating consisted of laponite (LAP), branched polyethyleneimine (BPEI), sodium alginate (SA) and chitosan (CH) that was deposited onto FPU foams to enhance their fire safety property. Based on the thermogravimetric analysis results, it was indicated that after the deposition of LAP, the thermal stability of the coated FPU foams increased sharply. Foam treated with 9 quad layers (QL) of BPEI/SA/CH/LAP multilayered coating showed self-extinguishing behavior in an open flame burning test. Furthermore, the values of peak heat release rate (PHRR), total heat release (THR) and smoke release rate (SPR) of the coated FPU foams reduced considerably in comparison to those of the pure FPU foam. Specifically, 9 QLs of BPEI/SA/CH/LAP declined the PHRR and the THR by 74% and 42.6%, respectively. The coated FPU foam also showed self-extinguishing and anti-dripping features in an open flame testing. Therefore, it can be stated that LAP-based coating has incredible benefits in decreasing fire risk of FPU foams. Moreover, the flame retardant mechanism of this LAP-based multilayered coating was proposed. The LAP-based coating functioned as a physical insulating barrier that successfully retarded the permeation of the flammable volatiles, heat and oxygen. Hence, the significant decrease in PHRR with the self-extinguishing behavior was achieved, implying promising potential of this LAP-based multilayered coating to enhance the fire safety of FPU foams. • Laponite-based inorganic-organic hybrid coating is deposited on FPU foams. • The coated FPU foam shows a 74% lower peak heat release rate than the uncoated one. • The coated FPU foam exhibits a 62% lower smoke production rate than the uncoated one. • Laponite strengthens the barrier effect that accounts for reduced fire hazards. [ABSTRACT FROM AUTHOR]

This work was intended to clarify if the dyeing treatment could modify the functional properties of white substrate as well as the surface finishing would alter the initial color of dyed textiles. Thus, in this work, a kind of surface coating was applied to modify the flame retardant and hydrophilic properties of both the undyed (white) and dyed polyamide 6.6 (PA6.6) textiles using some novel compounds like chitosan (CS), montmorillonite (MMT), sodium alginate (ALG) and phytic acid (PA) in a quadralayer (QL) or a hexalayer (HL) fashion. The obtained results revealed that the dyed fabric samples exhibited better flame retardancy and hydrophilicity compared to the undyed one; indicating the dyeing treatment contributed in improving the functional properties. For example, the 5HL-deposited dyed fabric sample (i.e., PA6.6-D-5HL) showed a maximum reduction in the peak heat release rate (pHRR) by 32% and the 7.5QL-deposited dyed fabric sample (i.e., PA6.6-D-7.5QL) brought a water contact angle (WCA) value of 0°. However, this kind of surface finishing caused a slight loss in depth of color for the dyed fabric samples. [Display omitted] • A kind of surface coating was developed onto the undyed and dyed PA6.6 textiles. • Dyed fabrics showed better flame retardant properties compared to the undyed one. • Dyed fabric with a 5HL deposition obtained a maximum reduction in pHRR by 32%. • A super-hydrophilic surface was realized, especially for the dyed fabrics. • The applied finishing slightly altered the depth of color of dyed fabrics. [ABSTRACT FROM AUTHOR]

• A hybrid coating was prepared from chitosan, melamine, urea, phytic acid and GO. • Improved flame retardancy and hydrophilicity of PA6.6 fabrics were realized. • Hybrid coating raised LOI value up to 25 % and stopped the melt dripping completely. • A maximum reduction in pHRR by 56 % was achieved with 5 BLs depositions. • Hybrid coatings could withstand against 10 home laundering cycles. The layer by layer (LBL) deposition of chitosan/melamine/urea (CS/ME/UREA) and phytic acid (PA) onto the acrylic acid (AA) grafted Polyamide 6.6 (PA6.6) fabrics including a pad-dry-cure treatment with chitosan/graphene oxide (CS/GO) nanocomposites were considered to improve the hydrophilicity and durable flame retardancy. Obtained results indicated that these hybrid coatings could significantly improve the flame retardancy as the limiting oxygen index (LOI) value reached up to 25 % from 18.5 % and could completely stop the melt dripping where the fabric sample with two bilayers deposition and simultaneously treated with CS/GO nanocomposite (PA6.6-g-AA-2BL-CS/GO) achieved a V-1 rating. A 2BLs deposited hybrid coating (i.e., PA6.6-g-AA-2BL-CS/GO) could decrease the peak heat release rate (pHRR) by 47.1 %; whereas a maximum reduction of pHRR by about 56 % was achieved for 5BLs deposition. Moreover, a considerable improvement in thermal stability and char yield% were also realized in the thermogravimetric analysis (TGA) test. Furthermore, the as-prepared hybrid coatings imparted better hydrophilicity as a 2BLs deposition along with pad-dry-cure treatment by CS/GO could boost up the hydrophilicity of the treated fabrics further compared to the only 2BLs deposited fabric sample. In addition, the application of CS/GO nanocomposite could improve the stability of this coating and able to stop the dripping tendency even after 10 laundering cycles as well. [ABSTRACT FROM AUTHOR]

• Microwave assisted grafting of AA onto the PA6.6 fabric surfaces was done. • Layer by layer deposition and HP cross-linking were followed. • A maximum reduction in pHRR by ca. 50% was achieved. • Super-hydrophilic surfaces were obtained. • Such coating could retain anti-dripping properties even after 10 launderings. Microwave-assisted surface modification of polyamide 6.6 (PA6.6) fabrics was carried out in a grafting polymerization technique in the presence of acrylic acid (AA) monomer with an aim to enhance the extent of surface functional groups onto the PA6.6 fabric surfaces. In the next step, the surface modified fabric substrate was gone through a layer by layer (LbL) deposition process in the presence of some hybrid (organic/inorganic) polyelectrolytes in imparting hydrophylic and flame retardant properties and finally, the as prepared coating was subjected to a cross-linking treatment aided by hypo-phosphorus acid (HP) in enhancing the stability of the same. From the obtained results, it was revealed that the simultaneous microwave assisted grafting, LbL deposition and HP cross-linking left positive impacts in improving the flame retardant performance and hydrophilicity of PA6.6 fabrics along with the enhancement of coating stability in laundering. For example, acrylic acid grafted PA6.6 fabric sample with a 5-BL deposition and cross-linked with HP (i.e., PA6.6-g-AA-5BL-HP) attained a limiting oxygen index (LOI) value up to 23.5%, while exhibiting a significant level of reduction in the peak heat release rate (pHRR) by ca. 50 %. In line, a super-hydrophilic surface was obtained for this fabric sample as the water contact angle value declined to 0º. Furthermore, such kind of surface modification displayed a considerable level of coating stability during laundering as the anti-dripping properties still exist even after 10 home launderings. [Display omitted] [ABSTRACT FROM AUTHOR]