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A novel multifunctional phosphorus‐containing curing agent monomer (PPBMBA) was designed and prepared based on vanillin by the nucleophilic substitution reaction and Pinnick oxidation with phenylphosphonic dichloride (PPDCL). Then a series of epoxy resin (EP) impregnated reinforced wood samples were prepared by combining PPBMBA to improve the dimensional stability and flame retardancy of wood. Differential scanning calorimetry results showed that the curing ability of PPBMBA to EP formulations is equivalent to that of industrial amine curing agents, while simultaneously being flame retardant and environmentally friendly. Scanning electron microscopy (SEM) observation found that the cured EP composite was widely distributed in the wood. Besides, the water uptake rate and volumetric swelling (S) of the impregnated wood sample W‐EP‐0.10 were 59.8% and 67.8% lower than that of pure wood respectively, while the anti‐swelling efficiency (ASE) value was as high as 67.7%. The parallel‐to‐grain compression strength (CS) of the W‐EP‐0.10 was increased by up to 78.3% compared to that of pure wood, while the limiting oxygen index increased from 21.7% to 26.8%, and UL 94 reached V‐0 level. TGA‐FTIR and SEM analysis demonstrated that the thermal stability and flame retardancy of the impregnated wood samples were improved by generating non‐flammable gases and forming an insulating char layer synergistically. From a practical standpoint, this work has significant engineering application value for the development of value‐added wood products with high‐efficiency fire safety and dimensional stability from relatively low‐cost wood. [ABSTRACT FROM AUTHOR]

In this study, a novel halogen-free flame retarded form-stable phase change material (PCM) was designed and prepared, selecting paraffin as the thermal-energy storage material and epoxy resin (EP) as the supporting material; furthermore, a novel flame retardant curing agent PEPA-TMA (2,6,7-trioxa-1-phosphabicyclo-[2.2.2]-octane-4-methanol reacted with trimellitic anhydride) and melamine cyanurate were combined into the energy-storing material to obtain the flame retarded PCM. Thermal performances of the PCM were investigated through differential scanning calorimeter, the data suggested that the PCM had relatively high latent heat, and values normalized to the amount of paraffin were lower than the theoretical values. The thermogravimetric analysis displayed that the intumescent flame retardant (IFR) could improve the charring of the PCM, and the PCM had passed a UL 94 V-0 test when the IFR loading reached 24 wt%. The cone calorimeter results further proved that the PCM had better flame retardancy. The morphology of the composites was observed by scanning electron microscopy, and the images showed that the paraffin could be dispersed uniformly in the materials, which formed a three-dimensional network by EP. [ABSTRACT FROM AUTHOR]

Abstract: The thermal decomposition, fire retardancy and mechanical properties of wood-flour–polyvinyl chloride composites (WF–PVC) were investigated. Thermogravimetric analysis (TGA) tests showed that the addition of wood flour (WF) and zinc borate (ZB) significantly influenced the thermal degradation behavior of PVC and WF–PVC composite. WF reduced the initiation temperature (T initial) for thermal degradation of PVC, while ZB scarcely affected the initial temperature of WF–PVC. WF retarded the thermal decomposition of PVC in the early stage while ZB increased the rapidest decomposition temperature and reduced the decomposition rate of WF–PVC. The mechanism of thermal decomposition of the composite was analyzed by Fourier transform infrared (FTIR) spectroscopy using the attenuated total reflectance (ATR) method. The decrease of Cnd increase of Cndicated WF and ZB promote the crosslinking and charring reactions of PVC. According to the cone calorimetry (CONE) tests, WF had a positive effect on fire performance of PVC but had little effect on smoke suppression. In contrast, the incorporation of ZB had little effect on flame retardancy of WF–PVC but it was an effective smoke suppressant, decreasing the total smoke produced (TSP) by more than 50%. Mechanical results indicated that ZB had some negative effects on the strength properties of WF–PVC, however the modulus increased compared with the untreated composite. [Copyright &y& Elsevier]

Thermoplastic polyurethane (TPU)-based composites filled with carbon nanotubes (CNTs) and intumescent flame retardants (IFRs) were fabricated through melt compounding method. For comparison, TPU/IFR and TPU/CNT composites with different filling proportions were prepared, respectively. The results presented that the addition of 1 wt% CNTs and 10 wt% IFRs into TPU could achieve good flame retarding and electromagnetic interference (EMI) shielding properties simultaneously. With regard to flame retardancy, the compounding of CNTs and IFRs effectively suppressed the heat release rate and the UL-94 rating was upgraded to V-0 accompanied with prompt self-extinguishment and disappeared melt-dripping, which was equivalent to incorporate 20 wt% IFRs alone. However, the flame retardancy became deteriorated by loading more CNTs. It was revealed that the addition of CNTs could strengthen the carbonization effect of IFRs, but suppress their intumescent effect. Hence, a right amount of CNT loading was of critical importance to achieve synergistic effect with IFRs. Moreover, compared with the TPU/CNT system, the TPU/IFR/CNT system possessing the same CNT contents had a lower percolation threshold. When 1 wt% CNTs were introduced, the electrical conductivity was increased about two orders of magnitude and EMI shielding effectiveness was doubled in the presence of IFRs. The morphological observation and rheological analysis demonstrated that mixing with IFRs not only improved the dispersion of CNTs through particle collisions, but also benefited for establishing the continuous conductive pathways among the IFR particles. Accordingly, this work provided a promising and facile route to fabricate EMI shielding polymeric composites with excellent flame retardancy. [ABSTRACT FROM AUTHOR]

Fast-growing poplar with the dominant characteristic of short rotation plantation offers a potential solution to the growing market demand for wood. However, its practical applications are limited due to shortcomings such as high flammability and poor dimensional stability. To address these issues, this study introduced a facile impregnation process involving the in-situ polymerization of bio-based furfuryl alcohol (FA) and ammonium phytate (AMP) to enhance the flame retardancy and dimensional stability of poplar. The biomass content was higher than 95% for this impregnation solution. The thermal stability experiments revealed that the residual char mass of AMP/FA-wood at 800°C increased by 305% compared to unmodified poplar. Moreover, the AMP/FA-wood demonstrated superior flame retardancy, achieving UL-94 V-0 rating and a high limiting oxygen index of 36.3%. Additionally, it exhibited decreased heat release and total smoke production of 48.9% and 79.8%, respectively, in comparison to unmodified poplar wood. The impressive flame retardancy of AMP/FA-wood was ascribed to the incorporation of AMP through the nitrogen-phosphorus synergistic intumescent mechanism. Notably, the in-situ polymerization of FA during the modification process, the AMP/FA-wood displayed exceptional dimensional stability which was confirmed by the moisture content, anti-swelling efficiency, and water absorption tests. Hence, AMP/FA-wood with its excellent flame retardancy, thermal stability, and dimensional stability, holds promise as a reliable wood supply for various applications such as furniture, home decor, construction, and building. [Display omitted] • Phytic acid (PA) reacted with urea to synthesize the N/P flame retardant ammonium phytate (AMP). • AMP and furfuryl alcohol (FA) resins were utilized to modify fast-growing poplar wood by impregnation. • The impregnation solution had a high in biomass content and was environmentally friendly. • The AMP and FA modified wood significantly increased flame retardancy and dimensional stability. [ABSTRACT FROM AUTHOR]

Modification with 1,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU) can dimensionally stabilize wood and improve the durability, but does not change its flammability. In this study, fire retardant (methylolated guanylurea phosphate (MGUP) and boric acid (BA)) was incorporated in DMDHEU to treat Oak wood ( Quercus rubra L.). Thermogravimetry and cone calorimetry showed that combinative treatment with DMDHEU/MGUP/BA caused a considerable decrease in the pyrolysis temperature, heat release, and smoke production. A full-scale fire test indicated that DMDHEU/MGUP/BA modified wood can be classified as B fl -s1. Findings demonstrated that combinative treatments can substantially reduce the fire risk for DMDHEU-modified wood, making them especially useful for application in public settings. [ABSTRACT FROM AUTHOR]

The development of versatile wood-based biomaterials with integrated low density, high surface hardness, high strength, fire-resistance, anti-decay, and termite-resistance is highly desirable, yet challenging to skillfully fabricate. Inspired by the ubiquity of gradient biostructures in nature, we achieve biomimetic gradient densification structures by controlling the distribution of thermal-moisture fields within the wood, and combine this with in-situ curing of polyacrylic acid/borate supramolecular resins within the wood cells to transform bulk natural wood into lightweight, high strength, and multifunctional materials. The optimally gradient-densified hybrid wood, with a slight increase in density, demonstrates markedly improved mechanical properties (≈2.4 × increase in surface hardness, ≈52 % increase in flexural strength), excellent dimensional stability, and leaching resistance. In addition, the collaboration of the gradient-densified structure and the in-situ cured acrylic resin/borate supramolecular network provides the biomimetic wood hybrids with excellent fire resistance (V-0 rating in fire retardant grade, 74 % reduction in total smoke release, ≈2.5 × increase in fire performance index), decay and mildew resistance (mass loss of less than 10 %), as well as termite resistance (100 % protection efficiency and termite kill rate) properties. It is the first report to combine gradient densification with in-situ curing of supramolecular resins in the structural design and functionalization of wood-based composites. This new design principle provides guidance for fabricating advanced all-in-one wood materials with applications in lightweight, strong, fire-resistant, deterioration-resistant, and scalable building and furniture materials. [Display omitted] [ABSTRACT FROM AUTHOR]

A transparent intumescent flame retardant coating was prepared using melamine formaldehyde resin (MF) as the film-forming resin, phosphoric acid-pentaerythritol (H 3 PO 4 -PER) as the intumescent flame retardant system, and graphene oxide-ammonium borate (GO-ABT) as the flame retardant synergists, and applied to the surface of wood-plastic composite (WPC). The transparency, flame retardancy, and thermal stability of the flame retardant coatings were investigated and the flame retardant mechanisms of GO and ABT were analyzed. The results showed that the addition of 0.4 (wt%) GO and 4.0 (wt%) ABT coating had the best overall performance. After curing, the surface of the coating was smooth and flat, no whitening and cracking and other undesirable phenomena. Its overall light transmittance was greater than 80 %, and the surface pattern of the substrate was clearly visible. The addition of flame retardant synergists of GO and ABT significantly improve the flame retardant performance of the coating, with a maximum flame resistance time of 37 min. Meanwhile, the total heat release and total smoke release of the coating with 0.4 % GO and 4.0 % ABT decreased by 33.23 % and 39.43 % respectively compared with the control sample, and the carbon residue increased by 94.97 %, demonstrating good flame retardant and smoke suppression effects. • A water-borne transparent and flame retardant coating was prepared and applied on the surface of wood plastic composite. • The synergistic flame retardant mechanism of graphene oxide and ammonium biborate tetrahydrate was investigated. • Graphene oxide acts as a stress point, thereby improving the overall stability of the expanded carbon layer. • ABT promotes the formation of a "B-C" mixed carbon layer, increasing the density and mechanical strength of the carbon layer. [ABSTRACT FROM AUTHOR]

The synthesis of a novel flame retardant that can enhance fire-safety while maintaining or even improving the mechanical properties is crucial for the application of wood flour/polyvinyl chloride composites (WF/PVC). Here, the alginate-derived tactic was utilized to produce zinc oxide (ZnO) in situ on the surface of montmorillonite (MMT) nanosheet, and an original type of MMT@ZnO nanosheet was synthesized. Then, MMT@ZnO nanosheet was incorporated into the WF/PVC. The experimental results confirmed that the incorporation of MMT@ZnO nanosheet in WF/PVC simultaneously improves the flame retardancy and mechanical properties. Comparing with the WF/PVC, WF/PVC containing 6 wt% MMT@ZnO nanosheets (WF/PVCMZ-6) reduced the total heat release rate, and total smoke production by 30.1% and 32.2%, respectively. Encouragingly, the WF/PVCMZ-6 exhibited a significant increase of 24.6% in tensile strength and 36.8% in flexural strength. This work develops a biomass alginate-derived strategy to combine ZnO and two-dimensional MMT nanosheets that simultaneously enhance the mechanical performance and flame retardancy of WF/PVC for the construction field. [Display omitted] • The MMT@ZnO nanohybrid was fabricated by a simple alginate-derived strategy. • The MMT@ZnO can enhance the mechanical and flame-retardant properties of WF/PVC. • The MMT@ZnO changed the pyrolysis pathway of WF/PVC with a reduction of the aromatic compounds. • The MMT@ZnO catalyzed WF/PVC into a dense and continuous char residues. [ABSTRACT FROM AUTHOR]

Loading metal guests within porous aromatic frameworks (PAF-50) via secondary functional groups is a promising route for introducing or enhancing PAF performance in various applications. Herein, a quaternary pyridinium-type porous aromatic frameworks (PAF-50) and their composites (Zn-PAF-50), are successfully synthesized and incorporated into the wood matrix to effectively realize fire prevention and anticorrosion. More remarkable, PAF micro-nano additives are well dispersed in wood matrix by self-assembly strategy with in situ polymerization, and settled the problem of compatibility. Results show that the treated wood had a strong self-extinguishing ability and passed the UL-94 V-0 burning test. The char residue rate of the treated wood is significantly increased by 112.2%, and the activation energy calculated according to the FWO method has been reduced by 26.3% due to its high pyrolysis and char-forming reactivity. Meanwhile, instead of combustible gases such as methane, large amounts of CO 2 and H 2 O appeared in the degradation products of treated wood. Besides, a more stable and complete char layer is obtained in the treated wood after combustion, and a value of nO/nC is improved by 71.9%. The treated wood exhibited a mass loss rate of 0.5% compared to 32.3% for the untreated wood after the anti- brown-rot fungus tests. Further, this work provides a new direction for the application of PAF particles with expected structure in endowing material with versatility. Image 1 • PAF-50 and Zn-PAF-50 additives were successfully synthesized and incorporated into the wood matrix. • The treated wood had a strong self-extinguishing ability and passed the UL-94 V-0 burning test. • The treated wood exhibited a good anticorrosion and dimension stability. [ABSTRACT FROM AUTHOR]

• Castor oil-based flame retardant coatings are prepared via thiol-ene click reaction. • The released nonflammable gases can dilute oxygen concentration. • Si/P and S/P exert synergy flame retardance in condensed and gas phase, respectively. • Polyphosphoric acid catalyzes Si O and Si C bond into compact and stable char layer. In this paper, castor oil based UV-cured coatings are prepared via thiol-ene click reaction by varying molar content of a self-synthesized phosphorus-containing flame retardant (DA), a self-synthesized castor oil based-mercaptan (CO SH) and 1,3,5-triethylene-1,3,5-trimethylcyclotriazane (TTC), which is used for the study of synergistic effectivities for flame retardant component, photopolymerization kinetics, and thermal degradation. The results demonstrate the synergistic effectivities between DA and TTC via effective quantification of Lewin's parameter (E S). Under the molar ratio of DA, TTC and CO SH of 3:3:5, the thermal stability of coatings is significantly better than others and the char yield can reach 14.54% at 800 °C under air condition despite achieving better flame retardant properties, and the conversion of thiol and vinyl groups can reach 70% or more. Further, scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) tests show that polyphosphoric acid formed through the decomposition of DA can promote Si O and Si C bond into compact and stable char layer timely to protect wooden substrates and delay burning, which indicates the synergistic fire retardant property of P and Si in the condensed phase. Moreover, there are nonflammable gases (CO 2 and SO 2) released from the coatings to dilute oxygen concentration during thermal degradation by the analysis of thermogravimetry/infrared spectroscopy (TG-FTIR) tests, which also leads to the generation of porous char layer on the surface of wooden substrates. Besides, the oxygen can be also consumed by the phosphorus-containing compounds generated by DA simultaneously, which shows the synergistic fire retardant property of S and P in the gas phase. [ABSTRACT FROM AUTHOR]

Intumescent transparent coatings consisting of allyl-functionalized phosphonitrile (HABP), trimethylolpropane tris(3-mercaptopropionate) (TMMP) and 1H,1H,2H,2H-perfluorodecanethiol (PFDT) were prepared via photo-induced thiol-ene reactions without photoinitiator, and then fabricated onto wood surfaces to achieve both flame retardancy and hydrophobicity. The effects of PFDT content on the waterproof and fire prevention of the samples were investigated. The chemical structure of the HABP was characterized with FTIR, NMR and HRMS techniques. The surface compositions and transparency of the coatings were characterized by XPS and UV–Vis spectrophotometer. The sample could pass the UL-94 V-0 test and the double bond conversion (DC C=C) of the corresponding coating reached 93.3%. Results showed that the more the coating contained PFDT, the better the coated samples exhibited hydrophobicity and flame retardancy. From a broader perspective, thiol-ene reactions without initiators are showing significant potentialities for rapidly designing functional coatings on wood substrates, which will be develop more functional coatings for other application fields. • The UV-curable functional coatings were fabricated via thiol-ene click reaction without photoinitiator. • A polymerizable fire resistant monomer based on HCCP was successfully synthesized and applied. • The transparent coatings changed from hydrophilic to hydrophobic with the addition of PFDT. • Both gas-phase and condensed-phase flame retarding kinetic behavior of the coating were investigated. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A hexa-eugenol substituted phosphazene monomer (HEP) was synthesized and identified. • HEP-SH polymer networks are built by photo induced thiol-ene copolymerization between four multi-thiol monomers and HEP. • HEP-TEMPIC and HEP-PETMP networks exhibit outstanding intumescent flame retardancy. • HEP-TEMPIC and HEP-PETMP networks also possess high mechanical strength and transparency. Abstract Exploring renewable bio-based polymer materials with intrinsic flame retardancy and high mechanical strength will greatly increase the potential to meet fire safety and practicability requirements. In this study, a hexa-substituted cyclophosphazene monomer (HEP) is synthesized from abundant and renewable eugenol and then copolymerized with multi-thiol monomers to establish HEP-SH polymer networks by thiol-ene photopolymerization. Four HEP-SH polymer networks (HEP-TEGDT, HEP-TTMP, HEP-PETMP, HEP-TEMPIC) were prepared by varying the number of thiol groups or the backbone of thiol monomers. Among these polymer networks, HEP-PETMP and HEP-TEMPIC networks exhibit excellent flame retardancy (LOI > 27 vol.%, achieved UL 94 V-0 rating). The combustion parameters and flame retardant mechanism are further studied by cone calorimetry and combined scanning electron microscopy/energy-dispersive spectroscopy (SEM-EDS), which confirm the intumescent flame retardancy of HEP-SH networks is simultaneously affected by the contents of phosphorus and nitrogen element, as well as the structural features of the polymer network. In addition, the HEP-TEMPIC and HEP-PETMP networks also exhibit high mechanical strength and transparency. These eugenol-based thiol-ene polymer networks open a new pathway to develop sustainable high-performance flame retardant bio-based polymer materials for practical application. [ABSTRACT FROM AUTHOR]

Highlights • Castor oil-modified bio-mercaptan is used to prepare UV-cured flame-retardant coatings. • The pencil hardness of castor oil-based coating has improved to H grade. • P, S and Si in the coating have a synergistic flame retardant effect. • The coated wood of F4 remains the wood tracheid basic skeleton after combustion. • Bio-mercaptan can reduce the maximum degradation rate of the coatings. Abstract In this paper, a multifunctional castor oil based bio-mercaptan (abbrev. CO SH) was synthesized by esterification between castor oil (abbrev. CO) and 3-mercaptopropionic acid (MPA). In addition, [(6-Oxido-6H-dibenz [c,e][1,2] oxaphosphorin-6-yl) methyl] butanedioic acid (DDP) and allyl glycidyl ether (AGE) were used to synthesize the organic phosphorus flame retardant containing a double bond of allyl ether DDP-AGE (abbrev. DA) via a ring-opening reaction. The synergistic flame-retardant UV-cured coating containing phosphorus (P), silicon (Si) and sulfur (S) was prepared on wood surface with varying molar content of CO SH, DA and 2,4,6-trimethyl-2,4,6-trivinylcyclotrisilazane (TTC) via the thiol-ene click reaction. The results show that when the molar ratio of CO SH, DA and TTC is 5: 3: 3, the UV-cured coated wood samples pass the vertical UL-94 V-0 rating; the limiting oxygen index (LOI) value can reach 27.52%; the second peak of heat release rate (P2HRR) and the second smoke production rate peak (P2SPR) of the coated wood samples can be effectively suppressed, while the total heat release (THR) of 16.99 MJ/m2 is much lower than other samples and the total smoke production (TSP) is equivalent to that of uncoated wood sample; the final char residue rate can reach 14.41% during the cone calorimetry (CONE) tests. Moreover, the thermogravimetric analysis (TGA) demonstrates that CO SH promotes the degradation of films at a lower temperature, while it reduces the maximum degradation rate and delays the decomposition process simultaneously. Besides, the scanning electron microscope (SEM) shows that the coated wood internal tracheid basic skeleton remains basically intact and the char layer tends to exhibit a more compact morphology after the CONE tests if the wood is coated following the molar ratio of CO SH, DA and TTC of 5: 3: 3. Energy dispersive spectrometer (EDS) was used to compare the content of C, O, N, P, Si and S of the char layers formed by the coatings on the surface of coated wood samples after CONE tests, which addresses the synergistic flame retardance of P, S and P, Si. [ABSTRACT FROM AUTHOR]

Developing a strategy to improve the flame retardancy and water resistance of waterborne bio-based coatings on wood is an effective route to enhance safety and applicability of timbers. In this work, the waterborne itaconate-based unsaturated polyester (IAF) were synthesized from biomass-derived itaconic acid (IA) and flame retardants FRC-6 by melt polycondensation in one pot, which was investigated as an ideal waterborne resin for UV-curable coating applications. A series of UV-cured hybrid coatings on wood were prepared consisting of IAF, N-(Hydroxymethyl) acrylamide (NMA), and γ-methacryloxypropyltrimethoxysilane (MPS) in various proportions via UV-curing and sol-gel process. The incorporation of MPS enhanced the rigidity, cross-linkage, and water resistance of UV-cured hybrid coatings, but the excessive silicone gel limited the further improvement of coating performances due to the phase separation and reduced film-forming property. Moreover, the UV-cured hybrid coatings appeared exceptional charring properties and endowed wood with superior flame retardancy. It was noticed that P/N/Si synergistically promoted the formation of remarkable, dense, and stable char layer on wood as a barrier, retarding the spread of heat, oxygen, or flammable volatile and the further combustion of substrates. Besides, the free radical capture of phosphorus and the dilution effect of inert gas played an essential role in gas-phase flame retardancy. [Display omitted] • The waterborne itaconate-based unsaturated polyester was synthesized in one-pot. • The hybrid coatings were efficiently prepared by UV-curing and sol-gel process. • The silicone improved cross-linkage and water resistance of hybrid network. • The UV-cured hybrid coatings enhanced char formation and flame retardancy of wood. • P/N/Si played a synergistic role in the condensed and gas-phase flame retardancy. [ABSTRACT FROM AUTHOR]

• Surface densification & impregnation boosted the overall performance of wood. • Modified wood achieved a V-0 grade of fire resistance. • Surface hardness and wear resistance respectively improved by 132% and 22%. • Flexural and impact strength increased by 52% and 48%, respectively. • Modified wood with low density exhibited excellent dimensional stability. It is difficult to significantly improve the mechanical performance and fire-resistance of fast-growing wood without increasing its density. In this study, a modified poplar wood (USD-RA-W) with low-density, high dimensional stability, high mechanical strength, and fire resistance was successfully prepared by unilateral surface densification assisted with the impregnation of waterborne acrylic resin (WAR)/ammonium phytate (APA). The flexural and impact strength values of USD-RA-W increased by 52% and 48%, respectively, compared to the control samples (C-W). The surface hardness and wear resistance of USD-RA-W were also significantly improved, with a 132% increase in hardness and a 22% reduction in weight loss relative to C-W. The improvement in mechanical properties is attributed to the synergistic effects of surface densification and impregnation modification of APA-doped acrylic resin. The in-situ -cured resin network provides excellent dimensional stability by fixing the spring-back of the densified surface of the material. USD-RA-W shows significantly improved fire retardancy due to the introduction of bio-based APA. UL-94 analysis results show that the fire-retardant grade of the USD-RA-W passed V-0 and the limited oxygen index reached 50%. Cone calorimeter test results indicate that the total heat release rate and smoke release rate of the experimental group decreased by 32% and 77%, respectively, while the char residue reached 41%. A simple and green physic-chemical method for the preparation of high-performance USD-RA-W was established in this study. The proposed treated wood may be applicable in structural building materials and interior decoration fields. [ABSTRACT FROM AUTHOR]

Highlights • A novel flame-retardant coating on wood surface was prepared by thiol-ene UV-curing. • The coating has excellent flame retardant properties on wood surface. • No photoinitiator was added during the preparation. • N and P play an important role in gas phase and condensed phase flame retardance. Abstract A novel wood flame retardant coating has been obtained using acrylate oligomers and functional monomers containing elements phosphorus, nitrogen and sulfur as raw materials and applied on the wood surface based on thiol-ene click reaction. The UL-94, limiting oxygen index (LOI) test and thermal gravimetric analysis/infrared spectroscopy (TGA-FTIR) were used to examine the flammability and pyrolysis property of the coatings, respectively. The experimental data showed that the coating has better fire resistance on wood surface when the molar ratio of phosphorus and nitrogen monomer was 2: 4. The volatile products generated in the degradation processes of the coating were confirmed by TGA-FTIR, which are carboxylic acid, ammonia (NH 3), carbon dioxide (CO 2) and acid anhydride, with a temperature of maximum release rate corresponds to 99.80 °C, 170.96 °C, 346.75 °C and 358.80 °C, respectively. In addition, the coating released NH 3 and CO 2 as nonflammable gases during the degradation process, which diluted the oxygen concentration during combustion and was favorable to generate the intumescent char layer. The TGA curves of the coating showed three degradation, corresponding to the water loss and the C–S bond breaking of crosslinking networks, the degradation of phosphate and acrylates, the decomposition of unstable char layers, the main chain in poly N , N -dimethylacrylamide (PDMAA) and the formation of poly (phosphoricacid), respectively. The char yield of the coating reaches to 27.16% at 600 °C under nitrogen atmosphere, showing excellent flame retardant properties. [ABSTRACT FROM AUTHOR]

Various concentrations of guanylurea phosphate (GUP) were incorporated into an aqueous melamine-urea-formaldehyde (MUF) resin to synthesize a fire-retardant, translucent, and intumescent varnish. The effects of the GUP on the curing, light transmittance, and thermal stability of the resulting varnish, and combustion behavior of the varnish-coated plywood were determined by viscosimetry, Fourier-transform infrared (FT-IR) spectroscopy, ultraviolet-visible (UV–vis) spectroscopy, thermogravimetry (TG), and cone calorimetry, respectively. The results show that GUP decelerated the curing rate; the resulting varnish film was translucent and UV-absorbing. The calorimetry demonstrated that GUP did not change the thermal stability but significantly facilitated charcoal formation of the varnish. The presence of the GUP resulted in an increased intumescent thickness of the varnish and substantially suppressed and delayed the mass loss, smoke production, and heat release of the coated plywood. At 12% GUP concentration the resulting varnish film exhibited an optimal combination of translucency and fire retardancy. These findings demonstrate that the GUP can be incorporated into aqueous MUF resin for the synthesis of a clear intumescent varnish capable of fire retardancy. [ABSTRACT FROM AUTHOR]

Exploring facile synthesis and organic-solvent-free of renewable flame-retardant coatings in wood surface is in line with the environmental protection and safety. In this research, acrylated epoxidized soybean oil (AESO), flame retardant FRC-6, and itaconic anhydride (IAH) were used to prepare waterborne unsaturated resins (IAESO) and monomers (IAFRC) in one pot through esterification. The waterborne coatings consisting of IAESO and IAFRC appeared favorable dispersity, and applied to prepare flame-retardant UV-curable coatings in wood surface, which presented eligible physical properties including pencil hardness, adhesion, and solvent resistance. Meanwhile, IAESO-F20-W exhibited prominent flame retardancy with UL-94 V-0 rating and the highest LOI value of 28.9 %, which improved significantly comparing with pure wood. Further, IAFRC obviously enhanced the overall carbonization and produced the dense char layer covering on the substrate surface, which hindered the transfer of heat, smoke, and combustible volatiles, thereby effectively suppressed the further combustion and pyrolysis of substrate, demonstrating that the waterborne flame-retardant UV-curable coatings ameliorated wood flammability effectively. [Display omitted] • One-step modification from IAH availably improved the water-dispersibility of resins. • The whole preparation process was eco-friendly, simple, and efficient. • The UV-curable coatings evidently enhanced the flame retardancy of wood. • IAFRC played an important role in condensed and gas phases flame retardant effect. [ABSTRACT FROM AUTHOR]

• Wood flour-polyvinyl chloride(WF-PVC) composites with zinc compounds were prepared. • The charring ability of Zn on WF-PVC composites is higher than that of Sn. • The flame retarding mechanism of the element Zn and Sn was proposed and confirmed. Fire safety is an important issue for wood flour polyvinyl chloride (WF-PVC) composites. Here, three zinc salts are used in WF-PVC composites. Thermogravimetric analysis showed that zinc borate and zinc stannate did some negative effects on the thermal stability of WF-PVC composites at the first thermal decomposition stage, while zinc molybdate had little effects on thermal decomposition of the composites. However, zinc borate and zinc stannate promoted the formation of char. Based on the experiments and theoretical analysis, the charring ability of element zinc (Zn) was stronger than that of tin (Sn). According to the cone calorimetry, zinc stannate and zinc borate were effective flame and smoke retardants, which were mainly reflected in the longer ignition time and reduced heat and smoke release of flame retardant composites. From the char residue, zinc compounds played an important role in the condensed phase, the element tin mainly acted on the surface, while the element zinc worked in the whole phase. Finally, the flame retardants had unfavorable effects on the strength properties of WF-PVC. [ABSTRACT FROM AUTHOR]

Developing sustainable, high-performance, and flame-retardant wood coating is significantly important for effective utilization of wood. In this work, a bio-based flame-retardant curing agent of ammonium hydrogen phytate (AHP) was synthesized by controlling the reaction molar ratio of phytic acid and urea. This synthetic AHP displayed appropriate pH which is beneficial for curing melamine-urea-formaldehyde (MUF) resin aqueous solution, and the curing rate could be freely adjusted by changing the weight ratio of AHP to MUF, which was convenient for the operation of wood coating. Compared to the control sample of wood coating prepared by the commercial curing agent of ammonium chloride, except the greatly improved thermal stability and flame retardancy, the resultant wood coating (MP) exhibited comparable T g , hardness, adhesion, and water resistance, and its preparation process was facile, easy scale-up, and the solvent is eco-friendly water. Especially, the optimized MP-3 wood coating presented a high LOI value of 39.1% and UL-94 rating of V-0, and this LOI value was superior higher than that of previously reported flame-retardant coatings. The CONE tests and thermal imagery further confirmed this MP-3 coating could form tough intumescent char layer to effectively suppress the transmission of heat and oxygen and reduce the smoke production. And the outstanding flame retardancy of MP-3 wood coating was ascribed to N/P synergistic intumescent flame-retardant mechanism. Therefore, this research presents a sustainable, eco-friendly approach to construct high-performance, flame-retardant wood coating, which has great potential in the wood and furniture industries. [Display omitted] • A bio-based flame-retardant curing agent was synthesized based on phytic acid. • The curing rate could be freely adjusted by changing weight ratio of AHP and MUF. • This synthetic coating exhibited great thermal stability and flame retardancy. • The preparation process was easy scale-up, and the solvent is eco-friendly water. • The wood coating displayed excellent transparency and physical properties. [ABSTRACT FROM AUTHOR]

• The UV-curable multifunction bio-coating was fabricated based on mussel-inspired chemistry. • A novel flame retardant was successfully synthesized and applied. • A biological adhesive primer has been developed on wood for improved bonding properties. • The the priming mechanism was analyzed by quantum chemistry methods. Using the principles of green chemistry and its technology application, we proposed a robust strategy for fabricating a mussel-inspired transparent, halogen-free, flame retardant and good adhesive coating on the wood surface via a UV-assisted radical polymerization reaction. A novel phosphorus-containing flame retardant diallyl 4-phenylphosphonicbenzoic (DAPB) was successfully synthesized and applied to form the soy oil-based coating resin. The combination of the biocoating with the biological adhesive primer applied on wood offers a green and versatile strategy to replace the toxic and energy-intensive silane-based coupling agents currently in common use. The study shows that the coated wood had a strong self-extinguishing ability and could pass the UL-94 V-0 combustion test. The adhesional energy and the priming mechanism were systematically analyzed by quantum chemistry. From a broader perspective, the processing strategy of priming a surface provides a new platform for material surface UV-cured biocoating and has practical value in widely solving biointerface problems. Besides, the fabricated coating can also be applied to various flammable materials from fire, such as textile and filter paper, cotton surfaces, and extend their innovative applications. [ABSTRACT FROM AUTHOR]

• Double-layered WPPC filled with EG and APP was prepared. • The double-layered WPPC with EG in surface layer showed better fire retardant properties. • The char residue rate of double-layered WPPC with EG in surface layer was greatly increased. • The surface layer with EG of WPPC could protect the base layer from decomposition. • The flexural strength of double-layered WPPC with EG in surface layer was improved. Expandable graphite (EG) and ammonium polyphosphate (APP) distributed in different layer of wood fiber and polypropylene composites (WPPC) were prepared. The results of cone calorimetry showed that the layered distribution of EG and APP considerably improved the fire retardancy of the overall composites, and the char residue rate was 41.9%, which increased by 200% compared with that of single-layered WPPC. Moreover, a more firm and compact physical structure char in the base layer formed due to protection of EG in the surface layer. The flexural strength and modulus of double-layered WPPC also increased compared with these of the single-layered WPPC with EG. [ABSTRACT FROM AUTHOR]