A wood based on a self-assembled composite flame-retardant coating, and a preparation method and flame-retardant application thereof

Abstract

The application discloses a kind of based on self-assembly composite flame-retardant coating, with polyacetylimine PEI as positive flame-retardant raw material, APP / K10 prepared with ammonium polyphosphate APP and montmorillonite K10 as negative flame-retardant raw material, copper sulfate CuSO4 as positive electric protection raw material, sodium alginate SA as negative electric protection raw material, by the method for preparation of opposite charge polyelectrolyte by alternative immersion anion solution and cation solution.Its preparation method includes the following steps:1, the surface pretreatment of wood;2, the preparation of self-assembly solution;3, the construction of self-assembly composite flame-retardant coating;4, the protection of self-assembly composite flame-retardant coating.When the application as flame-retardant material, with flame-retardant property, pass UL-94V-0 level test;Limiting oxygen index is 40-60%;The temperature when decomposition mass is 5% is 120-140℃, the temperature when maximum decomposition rate is 280-320℃, the residual carbon amount at 800℃ is 30-40wt.%, after complete combustion, the residual carbon carbon layer is continuous and dense, without obvious crack and broken fiber structure, there is no hole.

Description

Technical Field

[0001] This invention relates to the field of flame-retardant coating technology, specifically to a type of wood based on a self-assembled composite flame-retardant coating, its preparation method, and its flame-retardant applications. Background Technology

[0002] Wood, as a natural and renewable biomass polymer material, has the advantages of being lightweight and high-strength, having a beautiful texture, being easy to process, and having adjustable humidity, and is widely used in furniture, interior and building decoration materials. However, wood has the disadvantages of poor fire resistance and being easily combustible, thus requiring flame-retardant treatment.

[0003] Currently, common flame retardant methods involve coating the wood surface with flame retardants or impregnating the wood with flame retardants. While surface coating is simple to operate and requires only a small amount of flame retardant, it is difficult to precisely control the coating thickness and dispersion, leading to wasted flame retardant and unstable flame retardant effects. However, impregnation with flame retardants can quickly and efficiently improve the flame retardant properties of wood, and this method easily yields coatings with high flame retardant capabilities.

[0004] Currently, common halogenated flame retardants are characterized by low cost, easy processing, and stable performance. However, these flame retardants pose a serious safety hazard by producing toxic or corrosive gases during combustion.

[0005] Among halogen-free flame retardants, ammonium polyphosphate (APP) molecules are not only non-toxic and halogen-free, but also contain a large amount of -PO4. 3- Furthermore, possessing the characteristics of anionic polyelectrolytes, it can be used as a raw material for flame retardants. For example, existing literature 1 (《A comparative study on effects of natural and synthesized nano-clays on the fire and mechanical properties of epoxy composites》[J]. Composites Part B: Engineering, 2019, 165(MAY15), 65-74.) used halloysite nanotubes (HNT) and layered double hydroxides (LDH) as two types of nanoclays to compare the fire resistance and mechanical properties of epoxy resin composites based on ammonium polyphosphate (APP) and the two types of nanoclays. The results showed that the incorporation of APP and nanoparticles significantly enhanced the flame retardancy and thermal stability of epoxy resin and epoxy / glass fiber systems, and the combination of APP and nanoclays significantly reduced the peak heat release rate of epoxy resin (approximately 87%). However, the limiting oxygen index of this technical solution is only 33.2±0.2%, which cannot meet the application requirements. In addition, this technical solution also has the technical problems of complex preparation process and long preparation time.

[0006] For example, existing literature 2 (《Study on flame retardancy of ammonium polyphosphate / montmorillonite nanocompound coated cellulose paper and its application assurface flame retarded treatment for polypropylene》[J]. Journal of Thermal Analysis and Calorimetry,2021,146(05):2015-2025.) uses ammonium polyphosphate / montmorillonite (APP / MMT) to prepare flame-retardant cellulose paper via a coating method. This study shows that compared with the original paper, the thermal stability and flame retardancy of the coated paper sample are significantly enhanced. However, due to the strong hydrophilicity of APP, the compatibility between APP and the substrate is poor, which leads to problems such as surface discoloration, poor hydrophobicity, and reduced mechanical strength in the prepared flame-retardant paper.

[0007] To address the complex technical challenges of the aforementioned preparation process, polyelectrolytes with opposite charges can be alternately deposited on the matrix based on strong or weak interactions between the solution and the substrate surface groups, such as electrostatic attraction, hydrogen bonding, coordination bonds, and van der Waals forces. This spontaneously forms a thin film with specific functions, thus achieving the self-assembly of the composite material. The self-assembly method is applicable to various substrates, and flame retardants prepared based on this method can effectively control the coating structure at the molecular and nanoscale levels, thereby improving flame retardant efficiency and saving costs. For example, existing literature 3 (《Effect of nitrogen and phosphorus co-doped carbon dots containing layer-by-layer self-assembled coating on UV resistance and thermal stability of cotton fabric》[J]. Cellulose,2024,31(3):1957-1966.) synthesized nitrogen and phosphorus co-doped carbon dots (N, P co-doped CDs) using a one-pot hydrothermal carbonization method. The resulting CDs were then combined with alginate and polyethyleneimine to prepare a multilayer coating on cotton fabric through a layer-by-layer self-assembly method. Although the cotton-1 fabric treated with CD coating showed more carbon residue in the TGA test at 700°C under nitrogen atmosphere, the final carbon residue of Cotton-1 / (PEI / ACD)6 at 700°C was only 18.3 wt.%, and the flame retardant performance still could not meet the application requirements.

[0008] Therefore, the existing technical problems, that is, the practical problems that need to be solved, are: to prepare green and environmentally friendly flame retardants, and to obtain flame retardants with high flame retardant performance at low cost and with simple preparation methods while ensuring flame retardant effect. Summary of the Invention

[0009] The purpose of this invention is to provide a wood based on a self-assembled composite flame-retardant coating, its preparation method, and its flame-retardant applications.

[0010] To address the technical problems existing in the prior art, the basic technical principle of this invention is as follows: first, positively charged flame retardant material PEI and negatively charged flame retardant material APP / K10 are used to form a polyelectrolyte flame retardant material with opposite charges; then, positively charged protective material CuSO4 and negatively charged protective material SA are cross-linked to form a flame retardant material protective layer; and finally, the flame retardant material is attached to the wood by a simple impregnation method to improve the flame retardant performance of the wood.

[0011] The purpose of the invention can be simply summarized as follows:

[0012] 1. Adding PEI, a positive resistance flame retardant, increases the temperature at which the mass loss rate is maximized, thereby improving thermal stability;

[0013] 2. Adding negative resistance flame retardant raw material APP / K10 increases the initial decomposition temperature of the material and improves its thermal stability;

[0014] 3. Adding SA-Cu protective material can effectively shorten the flaming combustion time and help improve flame retardant performance;

[0015] 4. By utilizing widely available and environmentally friendly halogen-free flame retardants and employing simple self-assembly technology, the flame retardant performance is improved, while simultaneously addressing the pollution and cost issues associated with adding curing agents in conventional flame retardant modification.

[0016] This refers to a method of forming a coating with highly efficient flame-retardant properties by alternately impregnating a wood substrate with electrolyte raw materials of opposite charges using self-assembly technology.

[0017] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0018] A self-assembled composite flame-retardant coating is obtained by using polyacetylimide (PEI), ammonium polyphosphate (APP), montmorillonite (K10), copper sulfate (CuSO4), and sodium alginate (SA) as raw materials, and depositing polyelectrolytes with opposite charges by alternately impregnating anionic and cationic solutions.

[0019] In the self-assembled composite flame-retardant coating, PEI is a positive flame-retardant material, APP / K10 is a negative flame-retardant material, CuSO4 is a positive protective material, and SA is a negative protective material.

[0020] The resulting self-assembled composite flame-retardant coating has high thermal stability, and the microstructure of the residual char layer after combustion is continuous and dense, without obvious broken fiber structure.

[0021] A method for preparing wood based on a self-assembled composite flame-retardant coating includes the following steps:

[0022] Step 1: Surface pretreatment of wood. Under certain conditions, the wood is immersed in sodium hydroxide solution for surface activation treatment. After the immersion activation treatment is completed, it is washed with deionized water and dried to obtain surface-activated wood, which is simply referred to as activated wood.

[0023] In step 1, the surface immersion activation treatment conditions are as follows: immersion activation temperature is 60-80℃, immersion activation time is 30-60min, and the concentration of sodium hydroxide solution is 0.5-1mol / L.

[0024] Step 2, preparation of self-assembly solutions: Polyethyleneimine (PEI), ammonium polyphosphate (APP), montmorillonite (K10), copper sulfate (CuSO4), and sodium alginate (SA) are prepared into PEI solution, APP / K10 solution, CuSO4 solution, and SA solution, respectively.

[0025] In step 2, PEI is a positive resistance flame ignition material, APP / K10 is a negative resistance flame ignition material, CuSO4 is a positive protection material, and SA is a negative protection material.

[0026] In step 2,

[0027] The molecular weight of PEI is 70,000, and the concentration of PEI solution is 1-2 g / L;

[0028] In the APP / K10 solution, the mass specification of APP is n≥1000, and the mass fraction of K10 is 282.2%.

[0029] The concentration of the CuSO4 solution is 0.5-1 mol / L;

[0030] The concentration of the SA solution is 3-5 g / L;

[0031] In step 2, the APP / K10 solution is prepared by placing APP and K10 in deionized water, stirring for 30-60 minutes, and then sonicating for 30-60 minutes to obtain the APP / K10 solution.

[0032] The mass ratio of the APP to K10 is 1:1;

[0033] Step 3, Construction of self-assembled composite flame retardant coating: The self-assembled composite flame retardant coating APP / K10-PEI-W-10, abbreviated as AKP-W, is constructed by sequentially impregnating PEI solution and APP / K10 solution.

[0034] Step 3 includes: Step 3.1, preparation of PEI-W; Step 3.2, preparation of APP / K10-PEI-W; Step 3.3, construction of the composite flame-retardant coating;

[0035] The specific steps of step 3 are as follows:

[0036] Step 3.1, Preparation of PEI-W: First, place the activated wood obtained in step 1 into the PEI solution obtained in step 2. After impregnation, wash and dry with deionized water to obtain PEI-W-1, abbreviated as PW-1.

[0037] Step 3.2, Preparation of APP / K10-PEI-W: Place the PW-1 obtained in step 3.1 into the APP / K10 solution obtained in step 2. After impregnation, wash and dry with deionized water to obtain APP / K10-PEI-W-1, abbreviated as AKP-W-1.

[0038] Step 3.3, Construction of the composite flame retardant coating: Repeat steps 3.1 and 3.2 to obtain the composite flame retardant coating APP / K10-PEI-W-10, abbreviated as AKP-W;

[0039] In steps 3.1 and 3.2, the soaking time is 5-30 minutes; in step 3.3, the number of repetitions is 1-10.

[0040] Step 4, protection of the self-assembled composite flame-retardant coating: A protective layer is constructed by sequentially impregnating the wood with CuSO4 solution and SA solution, namely, the wood SA-Cu-APP / K10-PEI-W based on the self-assembled composite flame-retardant coating, abbreviated as SCAKP-W. The specific steps are as follows:

[0041] Step 4 includes: Step 4.1, preparation of Cu-APP / K10-PEI-W; Step 4.2, preparation of SA-Cu-APP / K10-PEI-W.

[0042] The specific steps of step 4 are as follows:

[0043] Step 4.1, Preparation of Cu-APP / K10-PEI-W: Place the AKP-W obtained in step 3.2 into the CuSO4 solution obtained in step 2. After impregnation, wash and dry with deionized water to obtain Cu-APP / K10-PEI-W, abbreviated as CAKP-W.

[0044] Step 4.2, Preparation of SA-Cu-APP / K10-PEI-W: Place the CAKP-W obtained in step 3.3 into the SA solution obtained in step 2. After impregnation, wash with deionized water and dry to obtain SCAKP-W.

[0045] In step 4.1, the soaking time is 5-30 minutes; in step 4.2, the soaking time is 10-30 seconds.

[0046] A self-assembled composite flame-retardant coating, when used as a flame-retardant material, exhibits flame-retardant properties and passes the UL-94V-0 rating test in the UL-94 rating test.

[0047] In the limiting oxygen index test, the limiting oxygen index is 40-60%;

[0048] The temperature at which the decomposition mass is 5% is 120-140℃, the temperature at which the maximum decomposition rate is reached is 280-320℃, the char residue at 800℃ is 30-40wt.%, and the char residue layer after complete combustion is continuous and dense, without obvious cracks or broken fiber structure, and there are no pores.

[0049] The beneficial technical effects of the material obtained by this invention can be seen from the following tests:

[0050] TG testing results show that using SCAKP as a flame retardant can increase the initial decomposition temperature and the temperature at which the maximum decomposition rate is reached, thus improving thermal stability, and also significantly increasing char residue. However, adding each component individually did not achieve optimal flame retardant performance. Therefore, in SCAKP flame retardants prepared using the self-assembly method, the flame retardants work synergistically to jointly enhance flame retardant performance.

[0051] Further SEM testing of the char layer after complete combustion of wood impregnated with flame-retardant materials revealed that using SCAKP as a flame retardant can improve the quality of the char layer after combustion of wood coated with flame-retardant paint. During combustion, the flame retardant expands to form a dense layer, which enhances the wood's ability to isolate oxygen and heat from the char layer, thereby improving its flame-retardant performance.

[0052] Vertical burning tests showed that impregnation with flame-retardant materials can improve the UL-94 rating of wood. Using SCAKP as a flame-retardant material can improve the UL-94 rating of wood coated with flame-retardant paint.

[0053] Limiting oxygen index (LOI) tests show that impregnation with flame-retardant materials significantly increases the LIOI of wood. Using SCAKP as a flame-retardant material further improves the LIOI of wood coated with flame-retardant paint.

[0054] Compared with the prior art, the composite flame-retardant material of the present invention has the following advantages:

[0055] 1. The self-assembled composite flame-retardant coating prepared by this invention significantly improves the flame-retardant effect on wood, and the wood impregnated with the flame-retardant coating has excellent flame-retardant properties.

[0056] 2. This invention uses pollution-free, non-toxic, and environmentally friendly raw materials such as polyethyleneimine, ammonium polyphosphate, copper sulfate, and sodium alginate as electrolytes. The materials are widely available, inexpensive, non-toxic, and safe, eliminating the safety hazards caused by the combustion of halogen flame retardants and making it more environmentally friendly.

[0057] 3. The self-assembly technology used in this invention is simple and safe to operate, can control the coating thickness, and requires less reagent, which greatly saves costs. At the same time, this assembly technology is suitable for large-scale industrial application and has strong practicality. Attached image description:

[0058] Figure 1 The TG plots are for steps 3 and 4 of Example 1, and for Comparative Examples 2, 3, and 4.

[0059] Figure 2 This is a SEM image of the residual char layer after combustion in step 3 of Example 1;

[0060] Figure 3 Vertical combustion diagrams for steps 3 and 4 of Example 1, and Comparative Examples 1, 2, 3, and 4;

[0061] Figure 4 The FTIR plot of Example 1;

[0062] Figure 5 This is a SEM image of the char layer after combustion in Example 1;

[0063] Figure 6 This is a SEM image of the char residue layer after combustion in Comparative Example 1.

[0064] Figure 7 This is a SEM image of the char residue layer after combustion in Comparative Example 2.

[0065] Figure 8 This is a SEM image of the char residue layer after combustion in Comparative Example 3.

[0066] Figure 9 This is a SEM image of the char residue layer after combustion in Comparative Example 4. Detailed Implementation

[0067] The present invention will be further described in detail through embodiments and with reference to the accompanying drawings, but this is not intended to limit the scope of the invention.

[0068] Example 1

[0069] A method for preparing wood based on a self-assembled composite flame-retardant coating includes the following steps:

[0070] Step 1: Surface pretreatment of wood. Under the conditions of immersion activation temperature of 70℃ and immersion activation time of 60min, the wood is immersed in a sodium hydroxide solution with a concentration of 1mol / L for surface immersion activation treatment. After the immersion activation treatment is completed, the wood is washed with deionized water and dried to obtain surface activated wood, which is referred to as activated wood.

[0071] Step 2, preparation of self-assembly solutions: Polyethyleneimine (PEI), ammonium polyphosphate (APP), montmorillonite (K10), copper sulfate (CuSO4), and sodium alginate (SA) are prepared into PEI solution, APP / K10 solution, CuSO4 solution, and SA solution, respectively.

[0072] The molecular weight of the raw material PEI is 70,000, the concentration of the PEI solution is 2 g / L, and the PEI solution carries a positive charge, i.e., it is a positively charged anti-flame raw material.

[0073] In the APP / K10 solution, the mass specification of APP is n≥1000, the mass fraction of K10 is 282.2, and the APP / K10 solution carries a negative charge, i.e., it is a negatively charged anti-flame raw material.

[0074] The APP / K10 solution is prepared by placing 2.5g of APP and 2.5g of K10 in 250ml of deionized water, stirring for 30min, and then sonicating for 30min to obtain the APP / K10 solution.

[0075] The concentration of the CuSO4 solution is 0.5 mol / L, and the copper sulfate solution carries a positive charge, thus providing positive protection for the raw materials.

[0076] The concentration of the SA solution is 5 g / L. The sodium alginate solution carries a negative charge, which protects the raw material.

[0077] Step 3, Construction of the self-assembled composite flame-retardant coating: The self-assembled composite flame-retardant coating APP / K10-PEI-W-10, abbreviated as AKP-W, is constructed by sequentially impregnating PEI solution and APP / K10 solution. The specific steps are as follows:

[0078] Step 3.1, Preparation of PEI-W: First, with an impregnation time of 5 minutes, the activated wood obtained in step 1 is placed in the PEI solution obtained in step 2. After impregnation, it is washed with deionized water and dried to obtain PEI-W-1, abbreviated as PW-1.

[0079] Step 3.2, Preparation of APP / K10-PEI-W: With an impregnation time of 5 min, PW-1 obtained in step 3.1 is placed in the APP / K10 solution obtained in step 2. After impregnation, it is washed with deionized water and dried to obtain APP / K10-PEI-W-1, abbreviated as AKP-W-1.

[0080] Step 3.3, Construction of the composite flame retardant coating: Repeat steps 3.1 and 3.2 10 times to obtain the composite flame retardant coating APP / K10-PEI-W-10, abbreviated as AKP-W;

[0081] To demonstrate the thermal stability of AKP-W, a TG test was conducted. The test results are shown in Table 1 and... Figure 1 As shown, the temperature at which AKP-W decomposes to 5% by mass is 114.06℃, the temperature at which the maximum decomposition rate is reached is 350.12℃, and the char residue at 800℃ is 16.36 wt.%.

[0082] To demonstrate the flame-retardant properties of AKP-W, SEM testing was performed on the char layer remaining after complete combustion of AKP-W. The test results are as follows: Figure 2 As shown, Figure 2 a and Figure 2 b indicates that the AKP-W residual char layer is continuous and dense, without obvious broken fiber structure, but with microporous structure. Figure 2 c indicates that the residual carbon layer of AKP-W has a high degree of density.

[0083] To demonstrate the technical effectiveness of AKP-W as a flame-retardant coating for wood, vertical burning tests and limiting oxygen index tests were conducted on AKP-W.

[0084] The vertical combustion test results of AKP-W are shown in Table 2 and Figure 3 As shown, the average flaming time of each AKP-W sample after a single ignition and removal of the flame was 1.7 s. The total flaming time of the five samples after 10 ignitions and removals was 194.3 s. The longest flaming time of each sample after the second ignition and removal of the flame was 3 s. There was no flame spread to the fixture, and no burning material dripped, thus passing the UL-94V-1 rating test. After the vertical burning test, the AKP-W only showed partial burning marks. The burned part was intact and unbroken but slightly bent, and no obvious residual char fibers were observed.

[0085] The limiting oxygen index test results of AKP-W are shown in Table 2, and its limiting oxygen index is 46.3%.

[0086] Step 4, protection of the self-assembled composite flame-retardant coating: A protective layer is constructed by sequentially impregnating the wood with CuSO4 solution and SA solution, namely, the wood SA-Cu-APP / K10-PEI-W based on the self-assembled composite flame-retardant coating, abbreviated as SCAKP-W. The specific steps are as follows:

[0087] Step 4.1, Preparation of Cu-APP / K10-PEI-W: With an impregnation time of 5 min, the AKP-W obtained in step 3.2 is placed in the CuSO4 solution obtained in step 2. After impregnation, it is washed with deionized water and dried to obtain Cu-APP / K10-PEI-W, abbreviated as CAKP-W.

[0088] Step 4.2, Preparation of SA-Cu-APP / K10-PEI-W: With an impregnation time of 10s, the CAKP-W obtained in step 3.3 is placed in the SA solution obtained in step 2. After impregnation, it is washed with deionized water and dried to obtain SCAKP-W.

[0089] To demonstrate the successful preparation of SCAKP-W, FTIR testing was performed. The test results are as follows: Figure 4 As shown, SCAKP-W simultaneously contains characteristic peaks of APP, K10, SA-Cu, and PEI. The test results indicate that SCAKP was successfully prepared.

[0090] To demonstrate the thermal stability of SCAKP-W, TG testing was conducted. The test results are shown in Table 1 and... Figure 1 As shown, the decomposition temperature of SCAKP-W at 5% mass is 124.52℃, the temperature at which the maximum decomposition rate is reached is 298.09℃, and the char residue at 800℃ is 34.45 wt.%. Compared with AKP-W obtained in step 3.3, the decomposition temperature of SCAKP-W at 5% mass is 10.46℃ higher than that of AKP-W, and the char residue at 800℃ is 18.09 wt.% higher than that of AKP-W. The test results show that adding SA-Cu can increase the initial decomposition temperature and the char residue of the material, i.e., improve the thermal stability.

[0091] Table 1. Thermogravimetric test results

[0092]

[0093] To demonstrate the flame-retardant properties of SCAKP-W, SEM testing was performed on the char residue layer after complete combustion of SCAKP-W. The test results are as follows: Figure 5 As shown, where, Figure 5 a and Figure 5 b indicates that the residual carbon layer of SCAKP-W is continuous and dense, without obvious broken fiber structure. Figure 5c indicates that the char layer is dense and without obvious pores. Test results show that the composite flame-retardant coating prepared by the self-assembly method can obtain a char layer with high density, thereby improving flame-retardant performance. Compared with AKP-W obtained in step 3.3, it can be seen that adding SA-Cu can improve the quality of the char layer of SCAKP-W.

[0094] To demonstrate the technical effectiveness of SCAKP as a flame-retardant coating for wood, vertical burning tests and limiting oxygen index tests were conducted on SCAKP-W.

[0095] The results of the vertical combustion test are shown in Table 2 and Figure 3 As shown, the average flaming time of each SCAKP-W sample after a single ignition and removal of the flame was 1.4 s. The total flaming time of the five samples after ten ignitions and removals was 15.2 s. The longest flaming time after the second ignition and removal of the flame for each sample was 1.3 s. There was no flame spread to the fixture, and no burning material dripped, thus passing the UL-94 V-0 rating test. After the vertical burning test, SCAKP-W showed only a very small amount of burning marks, the burned part was intact without breakage, and no obvious residual char fibers were observed. Compared with the AKP-W obtained in step 3.3, it can be seen that the addition of SA-Cu gives SCAKP-W a protective layer, shortens the flaming time of the material, improves the UL-94 rating, and exhibits excellent flame retardant properties.

[0096] The limiting oxygen index (LOI) test results are shown in Table 2, with an LOI as high as 57.3%. Compared with AKP-W obtained in step 3.3, the LOI of SCAKP-W is 11% higher than that of AKP-W. The test results indicate that adding SA-Cu can improve the limiting oxygen index of the material.

[0097] Table 2 Results of Vertical Combustion Test and Oxygen Index Test

[0098]

[0099] To demonstrate the effect of self-assembled composite flame-retardant coatings on flame-retardant properties, Comparative Example 1 is provided, showing the performance of uncoated pure wood.

[0100] Comparative Example 1

[0101] A type of pure wood that is not coated with SCAKP, abbreviated as W.

[0102] To demonstrate the flame-retardant properties of W, SEM testing was performed on the char layer remaining after complete combustion of W. The test results are as follows: Figure 6 As shown, where, Figure 6 a and Figure 6 b indicates that the residual carbon layer of W is broken and contains many sparse fibrous structures. Figure 6 c indicates that the residual carbon layer has a large number of pores and cannot form a dense carbon layer.

[0103] Compared with Example 1, it can be seen that adding SCAKP can make the residual carbon layer continuous and dense with few and small pores, which can significantly improve the quality of the residual carbon layer.

[0104] To demonstrate the technical effectiveness of the wood flame-retardant coating, vertical burning tests and limiting oxygen index tests were conducted on W.

[0105] The vertical combustion test results of W are shown in Table 2 and Figure 3 As shown, the average flaming time of each sample W after a single ignition and removal of the flame was greater than 30 seconds. The total flaming time of the five samples after 10 ignitions and removals of the flame was greater than 250 seconds. The longest extinguished flame time of each sample after the second ignition and removal of the flame was greater than 60 seconds. Furthermore, the flame spread to the fixture, and burning material dripped down, failing the UL-94 rating test. After a vertical burning test, W was almost completely burned, the wood itself fractured, and obvious burn marks were observed, with visible residual char fibers. Compared with Example 1, it can be seen that SCAKP prepared using the self-assembly method can improve the UL-94 rating.

[0106] The limiting oxygen index test results of W are shown in Table 2, and its limiting oxygen index is 20.5%.

[0107] Compared with Example 1, it can be seen that SCAKP prepared by the self-assembly method can significantly increase the limiting oxygen index from 20.5% to 57.3%, an increase of 179.5%. Adding SCAKP can significantly improve the limiting oxygen index of the material.

[0108] A comparison of Comparative Example 1 and Example 1 demonstrates that SCAKP prepared by the self-assembly method can improve the UL-94 rating and limiting oxygen index, thus significantly enhancing the flame retardant properties of wood.

[0109] To demonstrate the influence of each component of the self-assembled composite flame-retardant coating on its flame-retardant properties, Comparative Examples 2, 3, and 4 were provided, in which wood was prepared based on a single coating of positive flame-retardant raw material PEI, a single coating of negative flame-retardant raw material APP / K10, and a single coating of SA-Cu protective layer, respectively.

[0110] Comparative Example 2

[0111] A flame-retardant wood based on a single coating of positive PEI flame-retardant material, without specific details, has the same steps as in Example 1, except that in step 3, only steps 3.1 and 3.3 are performed, and step 3.2 is not performed. At the same time, step 4 is not performed. That is, the PEI impregnation in step 3.1 is repeated 10 times to obtain flame-retardant wood based on PEI coating, abbreviated as PW.

[0112] To demonstrate the thermal stability of PW, TG tests were conducted, and the results are shown in Table 1 and... Figure 1 As shown, the temperature at which PW decomposes to 5% by mass is 131.34℃, the temperature at which the maximum decomposition rate is reached is 330.10℃, and the char residue at 800℃ is 22.26 wt.%.

[0113] Compared with Example 1, SCAKP-W has a char residue of 12.19 wt.% higher than PW at 800°C. The test results show that adding SCAKP flame retardant material can increase the char residue.

[0114] TG test results show that in SCAKP, the main function of PEI is to slightly increase the initial decomposition temperature of the material and significantly increase the temperature at which the mass loss rate is maximum, i.e., to improve thermal stability. However, coating the positive resistance flame ignition raw material PEI alone has no significant effect on improving the carbon residue of the material.

[0115] To demonstrate the flame-retardant properties of PW, SEM testing was performed on the char layer remaining after complete combustion of the PW. The test results are as follows: Figure 7 As shown, where, Figure 7 a and Figure 7 b indicates that the residual char layer contains a sparse and fragmented wood fiber structure. Figure 7 c indicates that the residual carbon layer of PW has a lamellar structure and a small number of micropores.

[0116] Compared with Comparative Example 1, it can be seen that adding PEI can reduce the number of pores in the charcoal layer. However, there are still many broken wood fibers. This problem directly means that adding PEI alone cannot increase the amount of charcoal.

[0117] Compared with Example 1, it can be seen that adding SCAKP can make the residual char layer form a continuous and dense structure, block some of the pores in the residual char layer, and significantly reduce broken fibers, thereby improving the quality of the residual char layer.

[0118] To demonstrate the technical effectiveness of wood flame-retardant coatings, vertical burning tests and limiting oxygen index tests were conducted on PW.

[0119] The vertical combustion test results of PW are shown in Table 2 and Figure 3 As shown, the average flaming time of each PW sample after a single ignition and removal of the flame was greater than 30 seconds. The total flaming time of the five samples after 10 ignitions and removals of the flame was greater than 250 seconds. The longest extinguished flame time of each sample after the second ignition and removal of the flame was greater than 60 seconds. There was dripping of burning material, but the flame did not spread to the fixture, and the PW failed the UL-94 rating test. After the vertical burning test, almost half of the PW was burned, and the burning marks were obvious. The substrate was not broken, but obvious residual char fibers were observed.

[0120] Compared with Comparative Example 1, it can be seen that adding PEI can effectively suppress the spread of flames to the clamp;

[0121] Compared with Example 1, it can be seen that the addition of SCAKP can effectively retard flame and greatly protect the substrate. SCAKP-W passed the UL-94V-0 level test.

[0122] The limiting oxygen index test results of PW are shown in Table 2, and its limiting oxygen index is 30.7%.

[0123] Compared with Comparative Example 1, it can be seen that adding PEI can increase the limiting oxygen index of the material from 20.5% to 30.7%, an increase of 49.76%.

[0124] Compared with Example 1, it can be seen that adding SCAKP can improve the limiting oxygen index of the material.

[0125] By comparing Comparative Example 2 with Comparative Example 1 and Example 1, the following conclusions can be drawn:

[0126] 1. Adding PEI positive resistance flame retardant material can slightly increase the initial decomposition temperature of the material and significantly increase the temperature at which the mass loss rate is maximum, thus improving thermal stability. It can also reduce the number of pores in the residual char layer, but it cannot increase the amount of residual char.

[0127] 2. Adding PEI positive flame retardant material can effectively suppress the spread of flame to the fixture, but it cannot improve the UL-94 rating;

[0128] 3. Adding PEI positive resistance flame retardant material can improve the limiting oxygen index.

[0129] Comparative Example 3

[0130] A flame-retardant wood based on a single coating of negative resistant flame-retardant raw material APP / K10, the steps of which are the same as those in Example 1 unless otherwise specified, are different in that: in step 3, only steps 3.2 and 3.3 are performed, and step 3.1 is not performed. At the same time, step 4 is not performed. That is, the APP / K10 impregnation in step 3.2 is repeated 10 times to obtain flame-retardant wood based on the APP / K10 coating, which is referred to as AK-W.

[0131] To demonstrate the thermal stability of AK-W, a TG test was conducted. The TG test results for AK-W are shown in Table 1 and... Figure 1 As shown, the temperature at which AK-W decomposes to 5% by mass is 169.63℃, the temperature at which the maximum decomposition rate is reached is 305.9℃, and the char residue at 800℃ is 34.32 wt.%.

[0132] Compared with Example 1, the char residue of SCAKP-W at 800°C was increased by 0.13 wt.%, and the test results show that adding SCAKP flame retardant material can increase the char residue.

[0133] TG test results show that in SCAKP, the main function of APP / K10 is to significantly increase the initial decomposition temperature of the material, slightly increase the temperature at which the mass loss rate is maximum, i.e., improve thermal stability, and also has a slight effect on improving the amount of carbon residue at 800℃.

[0134] To demonstrate the flame-retardant properties of AK-W, SEM testing was performed on the char layer remaining after complete combustion of AK-W. The test results are as follows: Figure 8 As shown, where, Figure 8 a and Figure 8 b indicates that the residual char layer is continuous and dense, but still exhibits a distinct fibrous structure. Figure 8 c indicates that the char layer of AK-W has no obvious pores and contains a large number of flat bubble layers.

[0135] Compared with Comparative Example 1, it can be seen that adding APP / K10 can reduce the broken fiber structure and produce a dense carbon layer, thus improving the quality of the residual carbon layer.

[0136] Compared with Example 1, it can be seen that adding SCAKP can enable the residual char layer to form a continuous and dense structure, reduce the broken fiber structure, generate a large number of bubbles to form a residual char protective layer, thus improving the quality of the residual char layer.

[0137] To demonstrate the technical effectiveness of the wood flame-retardant coating, vertical burning tests and limiting oxygen index tests were conducted on AK-W.

[0138] The vertical burning test results for AK-W are shown in Table 2 and Figure 3 As shown, the average flaming time of each AK-W sample after a single ignition and removal of the flame was greater than 30 seconds. The total flaming time of the five samples after 10 ignitions and removals of the flame was greater than 250 seconds. The longest extinguished flame time for each sample after the second ignition and removal of the flame was 3.9 seconds. The flame spread to the fixture, but no burning material dripped down, thus failing the UL-94 rating test. After the vertical burning test, the AK-W was completely burned, with obvious burning marks. The substrate broke, but no obvious residual char fibers were observed.

[0139] Compared with Comparative Example 1, it can be seen that adding APP / K10 can significantly shorten the longest flameless combustion time after the second ignition and removal of the flame for each sample;

[0140] Compared with Example 1, it can be seen that adding SCAKP can reduce the spread of flame, effectively retard flame, and greatly protect the substrate. SCAKP-W passed the UL-94V-0 level test.

[0141] The limiting oxygen index test results of AK-W are shown in Table 2, and its limiting oxygen index is 41.7%.

[0142] Compared with Comparative Example 1, it can be seen that adding APP / K10 can increase the limiting oxygen index of the material from 20.5% to 41.7%, an increase of 103.41%.

[0143] Compared with Example 1, it can be seen that adding SCAKP can greatly improve the limiting oxygen index of the material.

[0144] By comparing Comparative Example 3 with Comparative Example 1 and Example 1, the following conclusions can be drawn:

[0145] 1. Adding APP / K10 negative resistance flame retardant material can significantly increase the initial decomposition temperature of the material, slightly increase the temperature at which the mass loss rate is maximum, thus improving thermal stability, and also has a slight effect on the amount of residual carbon at 800℃.

[0146] 2. Adding APP / K10 negative resistance flame retardant material can improve the density of the residual char layer.

[0147] 3. Adding APP / K10 negative resistance flame retardant material can effectively shorten the flameless combustion time, but it cannot improve the UL-94 rating.

[0148] 4. Adding APP / K10 negative resistance flame retardant material can significantly improve the limiting oxygen index.

[0149] Comparative Example 4

[0150] A flame-retardant wood based on a separate SA-Cu protective layer is obtained by means of steps that are the same as those in Example 1 unless otherwise specified. The difference is that step 3 is omitted and step 4 is performed directly after step 2. That is, the wood is impregnated with CuSO4 solution and SA solution in sequence with one impregnation time to obtain flame-retardant wood based on SA-Cu coating, which is referred to as SC-W.

[0151] To demonstrate the thermal stability of SC-W, TG testing was conducted. The test results are shown in Table 1 and... Figure 1 As shown, the temperature at which SC-W decomposes to 5% by mass is 105.10℃, the temperature at which the maximum decomposition rate is reached is 289.27℃, and the char residue at 800℃ is 27.90 wt.%.

[0152] Compared with Example 1, the carbon residue of SCAKP-W at 800℃ is 6.55 wt.%. The test results show that adding SC-W can increase the carbon residue of the material, but has no significant effect on the initial decomposition temperature and the maximum decomposition rate temperature of the material.

[0153] TG test results show that in SCAKP, the main function of SA-Cu is to increase the carbon residue of the material, but coating SA-Cu alone has no significant effect on improving the initial decomposition temperature and the maximum decomposition rate temperature of the material.

[0154] To demonstrate the impact of char residue on the flame-retardant properties of SC-W, SEM testing was performed on the char layer after complete combustion of SC-W. The test results are as follows: Figure 9 As shown, the residual char layer does not have an obvious broken fibrous structure, but some pores still exist. Among them, Figure 9 a and Figure 9 b indicates that the residual char layer contains a sparse and fragmented wood fiber structure. Figure 9 c indicates that the residual carbon layer of SC-W has an irregular lamellar structure and a small number of micropores.

[0155] Compared with Comparative Example 1, it can be seen that adding SA-Cu can reduce broken fibers and improve the quality of residual carbon layer;

[0156] Compared with Example 1, it can be seen that adding SCAKP can make the residual char layer form a continuous and dense structure, block some of the pores in the residual char layer, effectively reduce broken fibers, and improve the quality of the residual char layer.

[0157] To demonstrate the technical effectiveness of the wood flame-retardant coating, vertical burning tests and limiting oxygen index tests were conducted on SC-W.

[0158] The vertical combustion test results for SC-W are shown in Table 2 and Figure 3 As shown, the average flaming time of each SC-W sample after a single ignition and removal of the flame was 6.8 s. The total flaming time of the five samples after 10 ignitions and removals was 106.5 s. The longest flaming time of each sample after the second ignition and removal of the flame was greater than 60 s. There was no flame spread to the fixture and no dripping of burning material, but it failed the UL-94 rating test. After the vertical burning test, the SC-W showed obvious burning marks, but the substrate did not break, and no obvious residual char fibers were observed.

[0159] Compared with Comparative Example 1, it can be seen that adding SA-Cu can significantly shorten the average flaming time after a single ignition and removal of the flame for each sample and the total flaming time after 10 ignitions and removals of the flame for 5 samples, which helps to improve the UL-94 rating.

[0160] Compared with Example 1, it can be seen that adding SCAKP can reduce the flaming and non-flaming burning time, with outstanding flame retardant effect and great protection of the substrate. SCAKP-W passed the UL-94V-0 level test.

[0161] The limiting oxygen index test results of SC-W are shown in Table 2, and its limiting oxygen index is 33.0%.

[0162] Compared with Comparative Example 1, it can be seen that adding SA-Cu can increase the limiting oxygen index of the material from 20.5% to 33.0%, an increase of 60.98%.

[0163] Compared with Example 1, it can be seen that adding SCAKP can significantly improve the limiting oxygen index of the material.

[0164] By comparing Comparative Example 4 with Comparative Example 1 and Example 1, the following conclusions can be drawn:

[0165] 1. Adding SA-Cu protective material can improve the quality of residual carbon layer.

[0166] 2. Adding SA-Cu protective material can effectively shorten the flaming combustion time.

[0167] 3. Adding SA-Cu protective material can slightly improve the limiting oxygen index.

[0168] By comparing the above test results with those of Example 1, the following conclusions can be drawn:

[0169] 1. Adding PEI positive resistance flame retardant material can slightly increase the initial decomposition temperature of the material and significantly increase the temperature at which the mass loss rate is maximum, but it cannot increase the amount of char residue; it can reduce the number of pores in the char residue layer, effectively suppressing flame spread; it can slightly increase the limiting oxygen index, but it cannot improve the UL-94 rating.

[0170] 2. Adding AK negative resistance flame retardant material can significantly increase the initial decomposition temperature of the material, slightly increase the temperature at which the mass loss rate is maximum, and increase the amount of char residue; it can reduce broken fibers in the char residue layer and reduce the number of pores, but it cannot suppress flame spread; it can effectively shorten the flameless combustion time and significantly increase the limiting oxygen index, but it cannot improve the UL-94 rating.

[0171] 3. Adding SA-Cu protective material can improve the quality of the char layer, effectively shorten the flaming combustion time, and slightly increase the limiting oxygen index, but it cannot improve the UL-94 rating.

[0172] 4. Adding AKP flame retardant material can significantly increase the temperature at which the mass loss rate is maximum, but it cannot increase the amount of char residue; it can reduce broken fibers in the char residue layer, reduce the number of pores, effectively inhibit flame spread, effectively shorten the flaming and non-flaming combustion time, significantly increase the limiting oxygen index, and improve the UL-94 rating.

[0173] After adding SCAKP flame retardant material, the residual char content of the material is significantly increased, the quality of the char layer is significantly improved, the limiting oxygen index is significantly improved, the UL-94 rating is improved to V-0 rating, and the flame retardant performance is greatly enhanced.

Claims

1. A method for the production of wood based on a self-assembled composite fire-retardant coating, characterized by: A self-assembled composite flame-retardant coating is prepared by alternately dipping an anion solution and a cation solution, and depositing polyelectrolytes with opposite charges, using polyacetylimine (PEI), ammonium polyphosphate (APP), montmorillonite K10, copper sulfate (CuSO4) and sodium alginate (SA) as raw materials; In the self-assembled composite flame-retardant coating, PEI is a positive electric flame-retardant raw material, APP / K10 is a negative electric flame-retardant raw material, CuSO4 is a positive electric protective raw material, and SA is a negative electric protective raw material. The self-assembled composite flame-retardant coating has high thermal stability, and the micro-morphology of the carbon layer obtained after combustion is continuous and dense without obvious broken fiber structure. The method comprises the following steps: Step 1: surface pretreatment of wood, under certain conditions, the wood is immersed in a sodium hydroxide solution for surface immersion activation treatment, after the immersion activation treatment, the surface-activated wood, referred to as activated wood, is obtained after washing with deionized water and drying; In step 1, the conditions for surface immersion activation treatment are as follows: the immersion activation temperature is 60-80 ℃, the immersion activation time is 30-60 min, and the concentration of the sodium hydroxide solution is 0.5-1 mol / L; Step 2: preparation of a self-assembled solution, raw materials including polyethyleneimine (PEI), ammonium polyphosphate (APP), montmorillonite K10, copper sulfate (CuSO4) and sodium alginate (SA) are prepared into PEI solution, APP / K10 solution, CuSO4 solution and SA solution, respectively; In step 2, PEI is a positive electric flame-retardant raw material, APP / K10 is a negative electric flame-retardant raw material, CuSO4 is a positive electric protective raw material, and SA is a negative electric protective raw material; In step 2, The molecular weight of PEI is 70,000, and the concentration of the PEI solution is 1-2 g / L; In the APP / K10 solution, the mass specification of APP is n≥1000, and the mass fraction of K10 is 282.2; The concentration of the CuSO4 solution is 0.5-1 mol / L; The concentration of the SA solution is 3-5 g / L; In step 2, the preparation method of the APP / K10 solution is as follows: APP and K10 are placed in deionized water, stirring is performed for 30-60 min, and then ultrasonic treatment is performed for 30-60 min, so that the APP / K10 solution is obtained; The mass ratio of APP to K10 is 1:1; Step 3: construction of a self-assembled composite flame-retardant coating, a self-assembled composite flame-retardant coating APP / K10-PEI-W-10, referred to as AKP-W, is constructed by sequentially immersing the PEI solution and the APP / K10 solution, Step 3 comprises the following steps: step 3.1: preparation of PEI-W; step 3.2: preparation of APP / K10-PEI-W; and step 3.3: construction of a composite flame-retardant coating; Step 4: protection of the self-assembled composite flame-retardant coating, a protection layer is constructed by sequentially immersing the CuSO4 solution and the SA solution, that is, wood based on the self-assembled composite flame-retardant coating SA-Cu-APP / K10-PEI-W, referred to as SCAKP-W, and the specific steps are as follows: The step 4 comprises: step 4.1, preparation of Cu-APP / K10-PEI-W; and step 4.2, preparation of SA-Cu-APP / K10-PEI-W.

2. The method of claim 1, wherein: The specific steps of the step 3 are: Step 3.1, preparation of PEI-W, first, the activated wood obtained in step 1 is placed in the PEI solution obtained in step 2, after impregnation, it is washed with deionized water and dried, and PEI-W-1, referred to as P-W-1, is obtained; Step 3.2, preparation of APP / K10-PEI-W, the P-W-1 obtained in step 3.1 is placed in the APP / K10 solution obtained in step 2, after impregnation, it is washed with deionized water and dried, and APP / K10-PEI-W-1, referred to as AKP-W-1, is obtained; Step 3.3, construction of the composite flame-retardant coating, steps 3.1 and 3.2 are repeated, and the composite flame-retardant coating APP / K10-PEI-W-10, referred to as AKP-W, is obtained; In the steps 3.1 and 3.2, the impregnation time is 5-30 min; in the step 3.3, the number of repetitions is 1-10.

3. The method of claim 1, wherein: The specific steps of the step 4 are: Step 4.1, preparation of Cu-APP / K10-PEI-W, the AKP-W obtained in step 3.2 is placed in the CuSO4 solution obtained in step 2, after impregnation, it is washed with deionized water and dried, and Cu-APP / K10-PEI-W, referred to as CAKP-W, is obtained; Step 4.2, preparation of SA-Cu-APP / K10-PEI-W, the CAKP-W obtained in step 3.3 is placed in the SA solution obtained in step 2, after impregnation, it is washed with deionized water and dried, and SCAKP-W is obtained; In the step 4.1, the impregnation time is 5-30 min; in the step 4.2, the impregnation time is 10-30 s.

4. The self-assembled composite flame retardant coating prepared by the method according to claim 1, characterized in that: When applied as a flame-retardant material, it has flame-retardant properties, and passes the UL-94 V-0 level test in the UL-94 level test; In the limiting oxygen index test, the limiting oxygen index is 40-60%; The temperature at which 5% of the mass is decomposed is 120-140 ℃, the temperature at which the maximum decomposition rate is reached is 280-320 ℃, the residual carbon content at 800 ℃ is 30-40 wt.%, the residual carbon layer after complete combustion is continuous and dense, without obvious cracks and broken fiber structure, and there are no holes.

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