Flame-retardant wood with bionic fireproof isolation belt structure and preparation method thereof

Abstract

The application discloses a kind of flame-retardant wood with bionic fireproof isolation belt structure and preparation method, specifically related to the technical field of wood flame-retardant, reinforcing and other material property improvement field.It includes wood matrix and the bionic fireproof isolation belt structure that is located inside wood matrix, from surface to inside continuous dense;The bionic fireproof isolation belt structure is by high-strength microwave processing in wood inside layered through multi-scale fluid channel, by impregnating water-based acrylic resin / di-sodium octaborate supermolecular network and carrying out heat compaction, so that the supermolecular network is in situ cured in the multi-scale fluid channel and is formed.The application constructs layered through multi-scale fluid channel in situ in wood by high-strength microwave processing, significantly improves wood permeability, breaks through the technical bottleneck that fast-growing wood flame retardant is difficult to penetrate deeply, realizes the uniform load of supermolecular network from surface to inside, and overcomes the defect that conventional impregnation method flame retardant is only enriched in surface layer.

Description

Technical Field

[0001] This invention relates to the field of wood property improvement technology, such as flame retardancy and reinforcement, and specifically to a flame-retardant wood with a biomimetic fireproof isolation strip structure and its preparation method. Background Technology

[0002] Fast-growing timber (such as paulownia and poplar) is widely used in construction and home furnishing as a natural, biodegradable polymer material, but its flammable nature poses a serious fire hazard. To improve the flame retardant properties of fast-growing timber, existing technologies mainly employ surface coating and chemical impregnation methods.

[0003] The surface coating method involves applying flame-retardant paint or flame-retardant finish to the wood surface. Although the process is simple, the coating only adheres to a very shallow surface of the wood. In daily use, it is easily worn, cracked, or peeled off due to physical effects such as friction, bumps, and alternating humidity and heat, resulting in a rapid loss of fire resistance and poor long-term durability.

[0004] Chemical impregnation involves immersing wood in a flame retardant solution, allowing the retardant to penetrate the wood. However, fast-growing timber (especially species with numerous closed pores like paulownia) exhibits anisotropy and structural barriers, making it difficult for flame retardants to penetrate deeply; they often accumulate only on the surface. In the event of a fire, once the surface carbonized layer is destroyed, the untreated wood inside is directly exposed to the fire source, failing to provide overall protection. To improve permeability, existing technologies employ chemical pretreatment methods such as delignification. While this increases the agent loading, it also causes significant chemical pollution, failing to meet green environmental protection requirements.

[0005] In recent years, microwave treatment has been used to improve the permeability of wood. For example, Chinese patent CN114474260A describes the pretreatment of veneer under ultrasonic-microwave conditions followed by impregnation with flame retardant, but the preparation process is complex and time-consuming. Patent CN118832690A describes the microwave pretreatment of bamboo and wood to obtain a porous structure to increase the impregnation depth, but it relies on pressure impregnation equipment and only uses microwave treatment as a means of improving permeability, without considering the synergistic effect between the structural changes formed by microwave treatment and the flame retardant.

[0006] Chinese patent CN104760103A first uses microwave pretreatment to create new fluid channels within the wood, improving its permeability. Then, a flame retardant precursor is introduced into the wood pores through pressure impregnation. Finally, ammonium polyphosphate / SiO2 composite aerogel is generated in situ within the pores, resulting in flame-retardant reinforced wood. However, the microwave-constructed fluid channels only serve as impregnation pathways and are not transformed into a continuous, dense, multi-layered fire-retardant barrier. In the event of a fire, the aerogel-filled pores may still be rapidly burned through, failing to achieve a multi-level flame-retardant effect similar to a "firebreak." This technology does not employ a hot-pressing densification process, preventing the impregnated material from solidifying in situ within the channels and forming a dense structure. The bonding strength between the flame-retardant network and the wood skeleton is limited, and its resistance to leakage and durability need improvement. This patent still follows the traditional approach of "microwave-improved permeability → impregnation → generation of functional materials," failing to upgrade microwave treatment from a simple permeability improvement method to a strategy of synergistic structural and functional modification.

[0007] Therefore, how to construct a continuous, dense flame-retardant structure inside fast-growing timber that combines excellent flame retardancy and weather resistance from the surface inwards is a technical challenge that has not yet been solved by existing technologies. Summary of the Invention

[0008] Therefore, the present invention provides a flame-retardant wood with a biomimetic fireproof isolation strip structure and a preparation method thereof to solve the above-mentioned problems.

[0009] To achieve the above objectives, the present invention provides the following technical solution: According to one aspect of the present invention, a flame-retardant wood with a biomimetic fire-resistant barrier structure includes a wood matrix and a continuous, dense biomimetic fire-resistant barrier structure located within the wood matrix, extending from the surface to the interior. The biomimetic fire-resistant barrier structure is formed by layered, interconnected multi-scale fluid channels constructed within the wood through high-intensity microwave treatment, which are then impregnated with a water-based acrylic resin / sodium octaborate tetrahydrate supramolecular network and subjected to hot-pressing densification treatment, thereby solidifying the supramolecular network in situ within the multi-scale fluid channels. The flame-retardant wood achieves a V-0 rating in the UL-94 vertical burning test.

[0010] The wood matrix is ​​fast-growing timber, preferably paulownia or poplar. The biomimetic fireproof barrier structure is layered, forming multiple fire-resistant barriers along the thickness of the wood.

[0011] In the biomimetic fireproof barrier structure, the in-situ solidified supramolecular network and the cell wall skeleton of the multi-scale fluid channels form a three-dimensional interpenetrating network structure, and the supramolecular network fills and seals the multi-scale fluid channels to form a dense barrier layer extending along the thickness direction of the wood.

[0012] After the multi-scale fluid channels are thermo-pressurized, the in-situ solidified supramolecular network completely fills the adjacent cell cavities, forming a continuous organic-inorganic hybrid barrier wall.

[0013] According to another aspect of the present invention, a method for preparing flame-retardant wood with a biomimetic fire-resistant barrier structure includes the following steps: (1) High-intensity microwave treatment: High-intensity microwave treatment is applied to the wood to construct multi-scale fluid channels that are layered and interconnected inside the wood. (2) Impregnation treatment: The wood treated in step (1) is impregnated in a modified liquid containing water-based acrylic resin and disodium tetraborate tetrahydrate, so that the supramolecular network is loaded in the multi-scale fluid channels. (3) Hot pressing densification treatment: The impregnated wood is subjected to hot pressing densification treatment to solidify the supramolecular network in situ and transform the multi-scale fluid channels into a biomimetic fireproof isolation strip structure.

[0014] Furthermore, in step (1), before the high-intensity microwave treatment, the moisture content of the wood is adjusted to 30%-40%, and the wood is sealed with epoxy resin and then left to stand.

[0015] Furthermore, in step (1), the power of the high-intensity microwave treatment is 5.4-9 kW, and the treatment time is 30-90 s.

[0016] Further, in step (2), the total mass concentration of the modified liquid is 10%-25%, and the mass ratio of waterborne acrylic resin to disodium tetraborate octaborate is (9:1)-(7:3).

[0017] Further, in step (2), the impregnation treatment adopts the vacuum / atmospheric pressure method: first, evacuate to -0.005--0.02MPa, maintain for 20-40 min, then release the pressure to atmospheric pressure, and maintain for 2-6 h.

[0018] Furthermore, in step (3), before the hot pressing densification treatment, the moisture content of the impregnated wood is adjusted to 25%-35%.

[0019] Furthermore, in step (3), the temperature of the hot pressing densification treatment is 150-180℃, the pressure is 2-6 MPa, the time is 0.5-2 h, and the compression rate is 20%-40%.

[0020] In this invention, the limiting oxygen index of the flame-retardant wood is ≥30%, and preferably, when the mass ratio of waterborne acrylic resin to disodium tetraborate tetrahydrate is 7:3, the limiting oxygen index is ≥42%.

[0021] The present invention has the following advantages: This invention constructs multi-scale fluid channels with layered interconnection in situ inside the wood through high-intensity microwave treatment, which significantly improves the permeability of the wood and breaks through the technical bottleneck that flame retardants for fast-growing wood cannot penetrate deeply. It achieves uniform loading of supramolecular network from the surface to the inside, and overcomes the defect of conventional impregnation method flame retardants that are only enriched on the surface.

[0022] This invention is the first to create a biomimetic fireproof isolation strip structure, which transforms the fluid channel constructed by microwaves into a multi-layer fire barrier that is continuously distributed along the thickness direction through hot pressing and compaction, forming a multi-level flame-retardant protection system. This effectively avoids the burn-through failure of traditional flame-retardant layers, and significantly improves flame-retardant stability and protection depth.

[0023] This invention utilizes hot-press in-situ curing to create a three-dimensional interpenetrating structure between a water-based acrylic resin / sodium tetraborate octaborate supramolecular network and the wood cell wall. This tightly fills and seals the fluid channels, forming a continuous organic-inorganic hybrid barrier wall. The flame retardant is not easily lost and has strong weather resistance, thus achieving long-lasting flame retardancy.

[0024] This invention employs a microwave physical modification + water-based environmentally friendly system, which has no formaldehyde release, low VOC, and low toxicity. It does not require pretreatment with chemical pollutants such as delignification, and the process is green and environmentally friendly, meeting the requirements for environmentally friendly production.

[0025] The process of this invention is simple and controllable, and can be completed in just three steps: microwave, impregnation, and hot pressing. It has strong parameter adaptability and can be mass-produced industrially. At the same time, it achieves the dual effects of wood densification and enhancement and efficient flame retardancy, with excellent comprehensive performance.

[0026] The flame-retardant wood obtained by this invention has a limiting oxygen index of ≥30%, which can reach more than 42% under the optimal ratio. It achieves a UL-94 vertical burning rating of V-0, significantly reduces the heat release rate and total heat release, greatly improves the residual carbon rate, and has a high fire safety level. Attached Figure Description

[0027] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0028] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0029] Figure 1 This is a schematic diagram illustrating the technological principle and structural evolution of a flame-retardant wood with a biomimetic fireproof isolation strip structure, as provided in Embodiment 1 of the present invention.

[0030] Figure 2 The images provided in Test Example 1 of this invention are SEM images of the multi-scale fluid channel microstructure of flame-retardant wood with a biomimetic fireproof isolation strip structure. Among them, (ad) are SEM images of the cross section, tangential section, pits and hot-pressed sections of Example 2 after microwave treatment; (eh) are SEM images of the cross section, tangential section, pits and hot-pressed sections of Comparative Example 1; (i) is an SEM image of the cross section of Comparative Example 2; and (j) is an SEM image of the cross section of Comparative Example 3.

[0031] Figure 3 The changes and weight gain of wood samples and wood under different treatments provided in Example 2 of the present invention are shown in Test Example 1; wherein, (a) impregnation time and liquid absorption rate; (b) axial impregnation depth and weight gain rate.

[0032] Figure 4 The biomimetic fireproof isolation strip structure and its physical and chemical properties provided in Test Example 1 of the present invention are shown in the following: (a) digital image of BFW-2; (b, c) cross-sectional SEM image and EDS energy spectrum of BFW-2, respectively; (d) schematic diagram of the biomimetic fireproof isolation strip structure; (e) sample density change; (f) XRD; (g) FTIR.

[0033] Figure 5 The UL-94 test results, limiting oxygen index, and thermogravimetric analysis chart of the biomimetic fireproof isolation strip provided in Test Example 1 of the present invention are shown. Among them, (ad) represents the vertical burning test of natural wood, MW, BFW-1, and BFW-2, respectively; (e) represents the limiting oxygen index; and (fg) represents the thermogravimetric test.

[0034] Figure 6 The image shows the cone calorimetry test results provided in Test Example 1 of the present invention, where (ab) are the HRR and THR based on the cone calorimetry test, respectively; and (ce) are the residual carbon images of the untreated log, Comparative Example 3, and Example 2, respectively.

[0035] In the diagram, NW: Untreated; MW: High-intensity microwave treatment; BFW-R: High-intensity microwave treatment - resin impregnation only - hot pressing; BFW-1: Resin / flame retardant 9:1; BFW-2: Resin / flame retardant 7:3. Detailed Implementation

[0036] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Example 1

[0038] A method for preparing flame-retardant wood with a biomimetic fire-resistant barrier structure, as shown in the schematic diagram. Figure 1 As shown: 1. Raw materials and pretreatment Paulownia tomentosa planks with straight grain, no knots, and no obvious defects were selected, with dimensions of 300 mm (length) × 100 mm (width) × 29 mm (thickness). The planks were placed in a constant temperature and humidity chamber, and the moisture content was adjusted to 35% at a temperature of 25℃ and a relative humidity of approximately 80%. Epoxy resin (type E-51, epoxy value 0.51 eq / 100g, curing agent: polyamide 650) was evenly coated onto the ends of the wood, and the end-sealing treatment was performed by allowing the wood to stand at room temperature for 24 hours to prevent moisture from escaping too quickly from the ends during subsequent microwave treatment.

[0039] 2. High-intensity microwave processing to construct multi-scale fluid channels The end-sealed wood was placed in a box-type microwave treatment device (MGX-G200-9 model, microwave frequency 2.45GHz, power adjustable from 0-9 kW) and subjected to high-intensity microwave expansion treatment at a microwave power of 9 kW and a treatment time of 60 s. Microwave treatment caused the internal moisture of the wood to vaporize instantaneously, generating enormous vapor pressure, which promoted localized cracking and tearing of the vessel pit membranes, constructing multi-scale fluid channels with layered interconnections within the wood. After treatment, the samples were dried in an oven at 103±2 ℃ until completely dry for later use.

[0040] 3. Preparation of modified solution The modified solution was prepared using deionized water with a total mass concentration of 18%. The mass ratio of waterborne acrylic resin (50% solids content, pH 3.5, viscosity range 900-2500 mPa·s) to disodium octaborate tetrahydrate (purity ≥99%, analytical grade) was 9:1. The solution was stirred at 300 rpm for 30 min at room temperature until completely dissolved, and then allowed to stand for 10 min to remove bubbles before use.

[0041] 4. Vacuum / atmospheric pressure impregnation treatment Microwave-treated wood was placed in an impregnation container, and the modified solution was added to completely submerge the wood. The container was then transferred to a vacuum drying oven, and a vacuum was drawn to -0.01 MPa and maintained for 30 minutes to allow sufficient air to escape from the wood. The pressure was then released to atmospheric pressure, and impregnation continued for 4 hours to allow the modified solution to fully penetrate the multi-scale fluid channels within the wood under capillary force and pressure difference. After impregnation, the wood was removed, and excess modified solution was gently wiped off the surface with qualitative filter paper.

[0042] 5. Hot pressing densification treatment The impregnated wood was placed in a constant temperature and humidity chamber, and its moisture content was adjusted to 30% at 25℃ and 65% relative humidity. Hot pressing was then performed using a flatbed hot press (XLB-D400×400 type, heating plate size 400 mm×400 mm): the wood was placed between two heating plates and hot-pressed at 165℃ and 4 MPa pressure for 1 hour, with the compression rate controlled at 30% using a thickness gauge (i.e., the thickness after hot pressing is 70% of the original thickness). During the hot pressing process, the water-based acrylic resin underwent a cross-linking and curing reaction, and disodium tetraborate tetrahydrate was uniformly anchored within the closed channels. The multi-scale fluid channels were compressed and closed, transforming in situ into a biomimetic fire-resistant insulating strip structure. After hot pressing, the wood was naturally cooled to room temperature before being removed.

[0043] Example 2

[0044] 1. Raw materials and pretreatment Same as Example 1.

[0045] 2. High-intensity microwave treatment Same as Example 1.

[0046] 3. Preparation of modified solution The difference from Example 1 is that the mass ratio of waterborne acrylic resin to disodium octaborate tetrahydrate is adjusted to 7:3, and the total mass concentration of the modified solution is maintained at 18%. The preparation method is the same as in Example 1.

[0047] 4. Vacuum / atmospheric pressure impregnation treatment Same as Example 1.

[0048] 5. Hot pressing densification treatment Same as Example 1.

[0049] Example 3

[0050] 1. Raw materials and pretreatment Select straight-grained, defect-free poplar (Populus tomentosa) boards with the same dimensions as in Example 1, adjust the moisture content to 35%, seal the ends with epoxy resin, and let stand for 24 hours.

[0051] 2. High-intensity microwave treatment The microwave power was adjusted to 7 kW, the processing time was adjusted to 45 s, and the rest was the same as in Example 1. After processing, the product was completely dried for later use.

[0052] 3. Preparation of modified solution The mass ratio of waterborne acrylic resin to disodium octaborate tetrahydrate is 8:2, and the total mass concentration of the modified solution is adjusted to 15%. The preparation method is the same as in Example 1.

[0053] 4. Vacuum / atmospheric pressure impregnation treatment Evacuate to -0.015 MPa and maintain for 25 min; then impregnate at normal pressure for 3 h, and the rest is the same as in Example 1.

[0054] 5. Hot pressing densification treatment After impregnation, the moisture content of the wood was adjusted to 28%, and it was hot-pressed at 160°C and 3 MPa for 1.2 h, with a compression rate of 25%. The rest was the same as in Example 1.

[0055] Comparative Example 1 Compared with Example 2, step (2) high-intensity microwave treatment is omitted. That is, after the raw material is adjusted for moisture content and sealed, it is directly impregnated (the other parameters are the same as in Example 2), and then hot pressing densification treatment is performed (the parameters are the same as in Example 2).

[0056] Comparative Example 2 Compared with Example 2, in step (3), only deionized water was used for impregnation (without adding water-based acrylic resin and disodium tetraborate tetrahydrate), and the other microwave treatment and hot pressing parameters were exactly the same.

[0057] Comparative Example 3 Compared with Example 2, step (5) hot pressing densification treatment was omitted. The impregnated wood was directly placed in a ventilated environment at room temperature (25°C) to dry for 72 hours without heating or pressurizing.

[0058] Comparative Example 4 The traditional atmospheric pressure impregnation process was adopted: the raw materials were the same as those in Example 2 (Paulownia wood, moisture content 35%), without microwave treatment, and directly immersed in the same modified liquid (mass concentration 18%, resin:flame retardant = 7:3) as in Example 2, impregnated at atmospheric pressure and room temperature for 48 h, and then removed and air-dried at room temperature without hot pressing densification.

[0059] Comparative Example 5 1. Raw materials and pretreatment Same as Example 1 (Paulownia wood, size 300 mm × 100 mm × 29 mm, moisture content adjusted to 35%, epoxy resin end-capped, and left to stand for 24 h).

[0060] 2. High-intensity microwave treatment Same as Example 1 (microwave power 9 kW, processing time 60 s). After processing, the sample was placed in an oven at 103±2 ℃ and dried until completely dry.

[0061] 3. Follow-up processing It is not impregnated or hot-pressed for compaction. It is used directly for performance testing after drying.

[0062] Comparative Example 6 1. Raw materials and pretreatment Same as Example 1.

[0063] 2. High-intensity microwave treatment Same as Example 1 (9 kW, 60 s), then completely dry for later use.

[0064] 3. Preparation of modified solution Only water-based acrylic resin was used, without the addition of disodium octaborate tetrahydrate. The water-based acrylic resin was diluted with deionized water to a total mass concentration of 18% (consistent with the total concentration of the modified solution in Example 2), and stirred until homogeneous.

[0065] 4. Vacuum / atmospheric pressure impregnation treatment Same as Example 1 (vacuum degree -0.01 MPa maintained for 30 min, atmospheric pressure immersion for 4 h).

[0066] 5. Hot pressing densification treatment Same as Example 1 (moisture content adjusted to 30%, 165℃, 4 MPa, 1 h, compression rate 30%).

[0067] Test Example 1 Performance testing: The wood samples prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to performance tests according to the following standards and methods.

[0068] (1) Limiting Oxygen Index (LOI) Determination The test was conducted according to GB / T 2406.2-2009 "Determination of Combustion Behavior by Oxygen Index Method for Plastics - Part 2: Room Temperature Test". The sample size was 100 mm (length) × 10 mm (width) × 3 mm (thickness). Five parallel samples were tested for each group of samples, and the arithmetic mean was taken.

[0069] (2) Vertical flammability rating (UL-94) determination Vertical burning tests were conducted according to GB / T 2408-2008 "Determination of Burning Performance of Plastics - Horizontal and Vertical Methods". The sample dimensions were 125 mm (length) × 13 mm (width) × 3 mm (thickness), with five parallel samples tested per group. Evaluation indicators included: afterflame time (t1) after the first application of flame, afterflame time (t2) after the second application of flame, ignition time, and whether dripping ignited cotton.

[0070] (3) Cone Calorimeter The test was conducted according to ISO 5660-1:2015 "Reaction to fire tests - Heat release, smoke production and mass loss rate - Part 1: Heat release rate (cone calorimeter method)". The thermal radiation flux was 50 kW / m². 2 The sample size was 100 mm × 100 mm × 20 mm (thickness direction is the original thickness), and three parallel samples were tested in each group. Record the following parameters: Peak heat release rate (pHRR, kW / m³) 2 ); Total heat release (THR, MJ / m³) 2 ).

[0071] (4) Thermogravimetric analysis (TGA) Thermogravimetric analysis (TGA 550, TA Instruments, USA) was used for testing. Test conditions: nitrogen atmosphere, flow rate 50 mL / min, heating rate 10℃ / min, temperature range 30-800℃. The carbon residue at 800℃ was recorded.

[0072] (5) Scanning electron microscopy (SEM) observation The cross-sectional microstructure of the samples was observed using a field emission scanning electron microscope (ZEISS Gemini 300, Germany). The samples were sputter-coated with gold, accelerated at 5 kV, and observed at magnifications of 500-5000x to confirm the multi-scale fluid channels, biomimetic fire-resistant barrier structure, and supramolecular network filling state.

[0073] (6) Observation of penetration depth The samples of Comparative Example 1 and Comparative Example 4 were cut open along the thickness direction. The penetration depth of the modified liquid was visually observed by the staining method (0.1% methylene blue was added to the soaking solution), and photographs were taken and recorded using a stereomicroscope (Olympus SZX16).

[0074] The test results are shown in Table 1.

[0075] Table 1 Performance Test Results Note: The reduction rate / increase rate are calculated based on untreated logs; "-" indicates that the test was not performed or the data was not recorded.

[0076] In Examples 1-3, the modified liquid penetrated completely (uniformly distributed from the surface to the interior), and the cross-section of the samples was uniformly white / light yellow with no visible untreated areas. In Comparative Example 1, the modified liquid only penetrated to the surface layer (approximately 1-2 mm), and the core layer (depth > 2 mm) was the original wood color with no flame retardant loading. In Comparative Example 4, the modified liquid only adhered to the surface, with a penetration depth < 1 mm. The surface flame retardant layer was thin and easily detached after drying.

[0077] Microstructure observation (SEM) such as Figure 2 As shown, after microwave treatment in Example 2, multi-scale fluid channels with layered interconnections are visible, and interconnected pores appear at the cell wall rupture points; after hot pressing, the channels close, and the supramolecular network completely fills the gaps, forming a continuous and dense biomimetic fireproof isolation zone that is tightly bound to the cell wall without interface debonding. Figure 2 Comparative Example 1, without microwave treatment, showed intact cell walls but closed pits and no multi-scale fluid channels; although it underwent densification after hot pressing, it lacked network filling. Figure 2 eh). Comparative Example 2: Microwave treatment formed channels, but after hot pressing, there was no filling material inside the channels; only the cell walls were compacted, and there was no biomimetic isolation zone structure. Figure 2 i). In Comparative Example 3, after microwave treatment, the channels were open, and the internal filling with the modified liquid, after drying, formed a loose and porous aerogel-like substance. The channels were not closed, and there were a large number of micropores, without a continuous dense barrier layer. Figure 2 j).

[0078] Weight gain rate, such as Figure 3 As shown. Figure 3 a shows the change in liquid absorption rate of MW sample (Comparative Example 5) and untreated logs with impregnation time. It can be found that high-intensity microwave treatment can significantly increase the liquid absorption rate of wood specimens, with Comparative Example 5 showing an increase of 116.8% compared to untreated logs. In the axial impregnation profile ( Figure 3 In the analysis of b), the weight gain of untreated logs exhibited a typical characteristic of high at the ends and low in the center, indicating that natural anatomical barriers make it extremely difficult for fluids to penetrate deep into the wood along the grain. In stark contrast, Comparative Example 5 not only achieved a higher initial load at the ends, but also maintained a weight gain of up to 40% in the core area. This demonstrates that high-intensity microwave treatment can significantly improve the permeability of wood, overcoming the technical bottleneck of flame retardants' difficulty in deep penetration into fast-growing wood, and overcoming the defect of conventional impregnation methods where flame retardants only accumulate on the surface.

[0079] Depend onFigure 4 As shown in Table 1, the cross-sectional photographs of Example 2 ( Figure 4 a) The image shows a uniform light-colored filling band from the surface inwards, with no unprocessed areas visible to the naked eye, directly proving that the supramolecular network achieves uniform loading across the entire thickness. (SEM image) Figure 4 bc) shows that the channels were completely closed after hot pressing, and the filler adhered tightly to the cell wall, forming a continuous and dense isolation zone. Comparative Example 1 (no microwave, weight gain rate only 12.3%) and Comparative Example 3 (no hot pressing, isolation zone is loose) were compared. Figure 4 Together with Table 1, it is demonstrated that only through the synergy of "microwave + impregnation + hot pressing" can a continuous and dense fireproof isolation strip structure be formed.

[0080] Infrared spectroscopy display of Examples 1 and 2 at 1730 cm⁻¹ -1 (C=O, resin crosslinking) and 1300-1000 cm -1 A distinct characteristic peak was observed at (BO, borate), with an intensity higher than that of Comparative Example 6 (BFW-R), which only used resin, demonstrating the successful introduction and participation of disodium octaborate tetrahydrate in network construction. Energy dispersive spectroscopy (EDS) showed uniform distribution of C, O, B, and Na in the barrier walls, confirming the formation of an organic-inorganic hybrid structure. Combined with the data in Table 1: Example 2 achieved an LOI of 42.9% and a carbon residue of 32.7%, while Comparative Example 6 (resin only) had an LOI of only 26.5% and a carbon residue of 21.5%. Furthermore, Figure 4 No characteristics related to delignification chemical treatment (such as obvious changes in lignin characteristic peaks) were observed, confirming the green and environmentally friendly characteristics of this invention.

[0081] Depend on Figure 5 As shown in Tables ab and 1, the untreated logs and Comparative Example 5 could not self-extinguish after the first flame was applied, and therefore did not have flame-retardant capabilities. Figure 5 Example 1 shown in c exhibits rapid surface carbonization after flame application, successfully passing the UL-94 test and achieving a V-0 rating. Figure 5 As shown in d, in Example 2, the afterflame time was <2 s after both flame applications, and no molten droplets ignited the cotton, achieving a V-0 rating. In Table 1, only Examples 1-3 are V-0, while Comparative Examples 1-5 are NR (no rating), and Comparative Examples 3 and 6 are only V-2. This proves that only by simultaneously possessing the three elements of microwave pore formation, supramolecular network (containing flame retardant), and hot-press curing can a V-0 rating be achieved. Figure 5 e indicates that the LOI of untreated logs is 22.4%. Example 2 shows a surge in LOI to 42.9% (a 95% increase), compared to 31.5% for Example 1 and 34.7% for Example 3 (poplar). Comparative Example 6 (resin only) has only 23.2%, and Comparative Example 3 (no hot pressing) has only 28.3%. Figure 5The bar chart for e visually demonstrates the significant advantages of the biomimetic fire-retardant strip—its LOI value far exceeds that of conventional flame-retardant wood (typically 25-35%), and even surpasses that of many engineering plastics. Further data supports this: the synergistic flame-retardant effect of disodium tetraborate tetrahydrate (condensed phase charring + gas phase dilution) is key to the substantial increase in LOI. Figure 5 FG thermogravimetric analysis, TGA curve ( Figure 5 f) The initial decomposition temperature (T5%) of Example 2 is shown to be 278°C, higher than that of the log (245°C) and Comparative Example 6 (approximately 255°C); the maximum thermal weight loss temperature (T5%) is also shown to be higher. max The temperature was 405℃, 40℃ higher than that of the log. (DTG curve) Figure 5 The peak value of g) decreased significantly, indicating a slowdown in the pyrolysis rate. (800℃ residual carbon percentage bar chart) Figure 5 f) The result for Example 2 is 32.7%, a 94.6% increase compared to the original log (16.8%); compared to only 21.5% for Comparative Example 6 (an increase of 28.0%). These data demonstrate that the biomimetic fireproof barrier significantly enhances the thermal stability of the wood and promotes the formation of a dense char layer at high temperatures. This char layer acts as a physical barrier, inhibiting further pyrolysis of the wood interior.

[0082] Depend on Figure 6 As shown in Table 1, Figure 6 The HRR curve of untreated logs is steep, with a peak value of 316.2 kW / m³. 2 Example 2 shows a flat curve with a peak power of only 143.6 kW / m². 2 (Reduced by 54.6%). Comparative Example 6 (resin only) peak power: 385.4 kW / m³ 2 (An increase of 21.8%), the curve is relatively wide. The data in Table 1 corresponds exactly to this. Figure 6 In example b, the final THR in Example 2 was 25.07 MJ / m³. 2 Compared to logs (55.8 MJ / m³) 2 Example 1 showed a 55.1% reduction; Example 2 showed a 31.5% reduction; and Comparative Example 6 showed a 21.8% increase. A direct comparison is provided. Figure 6 Example 2 showed the lowest temperature among all samples, further validating the excellent heat release suppression effect of the biomimetic isolation strip. Figure 6 The images show the residual char of untreated logs, Comparative Example 3, and Example 2, respectively. In Example 2, the char layer is intact, dense, and crack-free, effectively isolating oxygen and heat radiation; the log char layer is loose and cracked, offering no protective effect. Comparative Example 3 (without hot pressing) also has a loose char layer, confirming the necessity of hot pressing for forming a dense insulating zone.

[0083] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A flame-retardant wood with a biomimetic fire-resistant barrier structure, characterized in that, It includes a wood matrix and a continuous and dense biomimetic fireproof isolation strip structure located inside the wood matrix from the surface to the inside; the biomimetic fireproof isolation strip structure is formed by layered and interconnected multi-scale fluid channels constructed inside the wood through high-intensity microwave treatment, which are then impregnated with a water-based acrylic resin / sodium tetraborate octaborate supramolecular network and subjected to hot-pressing densification treatment, so that the supramolecular network is solidified in situ within the multi-scale fluid channels.

2. A method for preparing flame-retardant wood with a biomimetic fire-resistant barrier structure, characterized in that, Includes the following steps: (1) Microwave treatment: High-intensity microwave treatment is applied to the wood to construct multi-scale fluid channels that are layered and interconnected inside the wood. (2) Impregnation treatment: The wood treated in step (1) is impregnated in a modified liquid containing water-based acrylic resin and disodium tetraborate tetrahydrate, so that the supramolecular network is loaded in the multi-scale fluid channels. (3) Hot pressing densification treatment: The impregnated wood is subjected to hot pressing densification treatment to solidify the supramolecular network in situ and transform the multi-scale fluid channels into a biomimetic fireproof isolation strip structure.

3. The preparation method according to claim 2, characterized in that, In step (1), before the high-intensity microwave treatment, the moisture content of the wood is adjusted to 30%-40%, and the wood is sealed with epoxy resin and then left to stand.

4. The preparation method according to claim 3, characterized in that, In step (1), the power of the high-intensity microwave treatment is 5.4-9 kW, and the processing time is 30-90 s.

5. The preparation method according to claim 3, characterized in that, In step (2), the total mass concentration of the modified liquid is 10%-25%, and the mass ratio of waterborne acrylic resin to disodium tetraborate tetrahydrate is (9:1)-(7:3).

6. The preparation method according to claim 3, characterized in that, In step (2), the impregnation treatment adopts the vacuum / atmospheric pressure method: first, evacuate to -0.005--0.02 MPa, maintain for 20-40 min, then release the pressure to atmospheric pressure, and maintain for 2-6 h.

7. The preparation method according to claim 3, characterized in that, In step (3), before the hot pressing densification treatment, the moisture content of the impregnated wood is adjusted to 25%-35%.

8. The preparation method according to claim 3, characterized in that, In step (3), the temperature of the hot pressing densification treatment is 150-180℃, the pressure is 2-6 MPa, the time is 0.5-2 h, and the compression rate is 20%-40%.

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