Wood adhesive and application thereof
By combining a wood adhesive composed of polyvinyl alcohol and wood flour with sodium acetate, the phase change properties of sodium acetate are utilized to form a self-healing mechanism, which solves the problem that existing wood adhesives cannot self-heal and improves the stability and shear strength of the wood bonding interface.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NORTHEAST FORESTRY UNIV
- Filing Date
- 2026-03-27
- Publication Date
- 2026-05-12
AI Technical Summary
Existing wood adhesives cannot self-repair at the bonding or repair interface after being impacted by external forces, leading to cracking, which increases the cost of replacing components or re-bonding, and is not conducive to sustainable recycling.
The method utilizes component A, composed of polyvinyl alcohol and wood flour, and component B, composed of sodium acetate, to form slender crystals in the cell cavities and micropores of wood cells by taking advantage of the phase change and salting-out properties of sodium acetate, thereby achieving self-repair.
After an external impact, sodium acetate crystals re-infiltrate the cell cavities and micropores of the wood cells, forming a strong interlocking structure upon cooling, thus achieving self-repair and improving the stability and shear strength of the bonding interface.
Smart Images
Figure CN122011972A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of wood processing technology, and in particular to a wood adhesive and its application. Background Technology
[0002] Wood adhesives are natural or synthetic polymer adhesives that enable wood to bond with each other, or with other dissimilar materials (such as metals, plastics, and inorganic boards), through interfacial wetting, diffusion, and curing. They are indispensable core auxiliary materials in the wood processing industry and wood product manufacturing. In practical industrial applications, wood adhesives are mainly used for bonding wood panels and repairing damaged wood panels.
[0003] There are many types of wood adhesives, including natural adhesives (such as starch-based adhesives and protein-based adhesives) and synthetic adhesives (such as urea-formaldehyde resin adhesives, phenolic resin adhesives (PF), or polyvinyl acetate emulsion adhesives). These adhesives are environmentally friendly and cure quickly, resulting in good shear strength in the wood panels after bonding and repair. However, these wood adhesives are all single-use adhesives; once cured, they are irreversible. If the bonded or repaired interface cracks due to external impact, it cannot self-repair, often requiring replacement of the component or re-bonding, increasing costs and hindering sustainable recycling. Summary of the Invention
[0004] The purpose of this invention is to provide a wood adhesive and its application. The wood adhesive provided by this invention can achieve self-healing when applied to the bonding interface formed after bonding or repairing wood boards.
[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a wood adhesive comprising separately packaged component A and component B: Component A comprises: polyvinyl alcohol, wood flour, and water; the wood flour accounts for 10-30% of the mass of polyvinyl alcohol; the polyvinyl alcohol accounts for 5-15% of the mass of water. Component B includes sodium acetate.
[0006] Preferably, the wood flour accounts for 13-28% of the mass of polyvinyl alcohol.
[0007] Preferably, the wood flour accounts for 20-25% of the mass of polyvinyl alcohol.
[0008] Preferably, the mass of the polyvinyl alcohol is 7.5 to 12.5% of the mass of water.
[0009] Preferably, the polyvinyl alcohol has a molecular weight of 25,000 to 300,000 and a degree of alcoholysis of 98 to 99%.
[0010] Preferably, the wood flour has a mesh size of 20 to 300 mesh.
[0011] Preferably, the wood flour has a mesh size of 100-300.
[0012] This invention also provides the application of the wood adhesive described above in wood panel processing or repair of damaged wood panels, characterized in that it includes: Component A is coated onto the surface of the wood board for bonding, and then immersed in molten component B before being removed and cooled. Alternatively, it may include: filling the damaged area of the damaged wood board with component A, then impregnating it with molten component B, and then removing and cooling it.
[0013] Preferably, the immersion temperature is 80~90℃, and the immersion time is 3~48h.
[0014] Preferably, the immersion temperature is 80~90℃, and the immersion time is 12~24h.
[0015] This invention provides a wood adhesive comprising separately packaged component A and component B: component A comprises polyvinyl alcohol, wood flour, and water; component B comprises sodium acetate trihydrate; the wood flour comprises 10-30% of the mass of polyvinyl alcohol; and the polyvinyl alcohol comprises 5-15% of the mass of water. This invention utilizes the phase change properties of sodium acetate. When applied to the processing or repair of damaged wood panels, at the impregnation temperature, some sodium acetate penetrates into the cell cavities and micropores of the wood cell wall. Upon cooling, it forms elongated crystals that create a strong interlocking structure with the wood panel surface, improving adhesion. The salting-out properties of sodium acetate also cause phase separation between polyvinyl alcohol (PVA) and water, leading to more hydrogen bonds between PVA particles, further enhancing adhesion. The sodium acetate crystals at the bonding or repair interface interact with the hydrogen bonds formed between wood flour and PVA. If the bonding or repair interface cracks due to external impact, the sodium acetate crystals at the bonding or repair interface can melt at the phase change temperature and re-penetrate into the cell cavities and micropores of the wood cell wall. Upon cooling, they form elongated crystals that reform a strong interlocking structure with the wood panel surface, achieving self-repair. Examples show that wood panels produced using the wood adhesive provided by this invention have an overlap bonding area of only 4 cm². 2 Under these conditions, the shear strength can reach 4.95 MPa, and after 10 repair cycles, the shear strength of the wood board remains at 4.749 MPa; the wood board obtained after repairing damaged wood boards has a transverse tensile strength of 25.0058 MPa and a longitudinal tensile strength of 47.6821 MPa. Attached Figure Description
[0016] Figure 1The XRD patterns of PVA / W, PVA / W / SAT, and PVA / SAT in Test Example 1 of this invention are shown below. Figure 2 The XRD patterns of PVA / W and PVA / W / SAT in Test Example 1 of this invention are shown below. Figure 3 The infrared spectra of PVA / W and PVA / W / SAT in Test Example 1 of this invention are shown below. Figure 4 Infrared spectra of PVA and PVA / SAT; Figure 5 This is a schematic diagram of the wood chip load-bearing test in Test Example 1 of the present invention; Figure 6 The graphs show the shear strength curves of the wood chips in Test Example 1 of this invention after shearing in the SAT molten state and crystalline state, respectively. Figure 7 Differential scanning calorimetry (DSC) curves of PVA / W and PVA / W / SAT in Test Example 1 of this invention; Figure 8 These are actual images of the wood chips before and after repair in Test Example 1 of this invention, after they have been cut. Figure 9 The graphs show the shear strength of the wood chips in Test Example 1 of this invention before and after repair. Figure 10 The differential scanning calorimetry (DSC) curves of PVA / W / SAT after the first and tenth shear self-healing of the wood chips in Test Example 1 of this invention are shown. Figure 11 The shear strength curves of the wood chips before shearing, after the 1st, 5th, and 10th shearing, and before and after repair are shown in Test Example 1 of the present invention. Figure 12 This is a schematic diagram of the load-bearing test of the wood chips after the 10th shearing repair in Test Example 1 of the present invention; Figure 13 This is a shear strength stability diagram of the wood chips after the 10th shear repair in Test Example 1 of the present invention; Figure 14 The shear strength curves of the wood chips in Test Examples 2-5 of this invention are shown. Figure 15 The shear strength curves of the wood chips in Test Examples 6-8 of this invention are shown. Figure 16 The three-dimensional surface plots of the shear strength of wood chips from test examples 9-12 and comparative test examples 1-16 of this invention are shown. Figure 17 These are actual images of the wood chips after being sheared in the SAT molten state in Test Examples 13-16 of this invention; Figure 18These are actual images of the wood chips after shearing in the SAT crystalline state in Test Examples 13-16 of this invention; Figure 19 The shear strength curves of wood chips in Test Examples 13-16 of this invention after shearing in the SAT molten state are shown. Figure 20 The shear strength curves of wood chips in test examples 13-16 of this invention after shearing in the SAT crystalline state are shown. Figure 21 These are stress distribution diagrams of wood chips in Test Examples 13-16 of this invention in the SAT molten state and SAT crystalline state, respectively; Figure 22 This is a three-dimensional surface plot of the shear strength of the wood chips in Test Examples 17-40 of this invention; Figure 23 These are photographs of sodium acetate trihydrate and sodium sulfate decahydrate in their molten and crystalline states in a bottle. Figure 24 These are photographs of sodium acetate trihydrate and sodium sulfate decahydrate in their molten and crystalline states after being removed from the bottle. Figure 25 SEM images of sodium acetate trihydrate and sodium sulfate decahydrate in their crystalline state; Figure 26 To compare the shear strength curves of the wood chips in Test Example 17; Figure 27 These are actual images of the damaged wood chips before and after repair in Test Example 41 of this invention; Figure 28 This is a SEM image of the damaged area of the damaged wood chip in Test Example 41 of this invention before repair. Figure 29 This is a SEM image of the damaged area after repair of the damaged wood chip in Test Example 41 of this invention. Figure 30 The tensile stress-strain curves in the longitudinal and transverse directions before and after the repair of the damaged wood chip in Test Example 41 of this invention are shown. Figure 31 These are actual images of the wood chips from Test Example 41 of this invention after being repaired and subjected to tensile forces in the longitudinal and transverse directions, respectively. Figure 32 These are before-and-after photos of the damaged wood chips in Test Example 42 of this invention before and after repair. Figure 33 The bar charts show the tensile and bending strength in the longitudinal and transverse directions of test examples 42-43 and comparative test examples 18-21 of this invention, after the damaged wood chips were repaired, the damaged wood chips, and the undamaged wood chips, respectively. Detailed Implementation
[0017] This invention provides a wood adhesive comprising separately packaged component A and component B: Component A comprises: polyvinyl alcohol, wood flour, and water; the wood flour accounts for 10-30% of the mass of polyvinyl alcohol; the polyvinyl alcohol accounts for 5-15% of the mass of water. Component B includes sodium acetate.
[0018] The wood adhesive provided by this invention includes component A, which comprises polyvinyl alcohol (PVA). This invention utilizes the fact that the PVA molecular chain is rich in hydroxyl groups (-OH), which can form hydrogen bonds with the hydroxyl groups in wood fibers, generating strong intermolecular forces, thereby achieving efficient adhesion to wood. As one embodiment of this invention, the molecular weight of the PVA can be from 25,000 to 300,000; the degree of hydrolysis of the PVA can be 98-99%. This invention further increases the number of hydrogen bonds by limiting the molecular weight and degree of hydrolysis of the PVA, thereby improving the adhesion performance to wood.
[0019] In this invention, component A comprises wood flour. This invention uses wood flour to increase the viscosity of the adhesive and reduce its flowability, thereby improving coating performance, preventing polyvinyl alcohol from permeating the adhesive, and enhancing the adhesive's gap-filling ability, allowing it to better fill tiny gaps and achieve a tighter interfacial bond. As one embodiment of this invention, the mesh size of the wood flour can be 20-300 mesh or 100-300 mesh. This invention, by limiting the mesh size of the wood flour, ensures good wood wettability and impact resistance, thus reducing adhesive layer cracking. This invention does not have a specific limitation on the source of the wood flour; it can be prepared from wood or waste wood known in the art, or purchased to obtain wood flour of the required mesh size.
[0020] In this invention, the mass of the wood flour is 10-30% of the mass of polyvinyl alcohol. As one embodiment of this invention, the mass of the wood flour can be 13-28% or 20-25% of the mass of polyvinyl alcohol. This invention ensures that a composite network is formed through the hydrogen bonds of polyvinyl alcohol and the physical entanglement of the wood flour, thereby improving the adhesive properties of the adhesive.
[0021] In this invention, component A further includes water. This invention uses water to fully dissolve polyvinyl alcohol and mix it with wood flour to form a slurry, which can be used to coat the surface of wood panels. In one embodiment of this invention, the mass of the polyvinyl alcohol can be 5-15% or 8-10% of the mass of water. This invention ensures that the polyvinyl alcohol is fully dissolved and forms a slurry with the wood flour by limiting the mass of the polyvinyl alcohol to a percentage of the mass of water.
[0022] As one embodiment of the present invention, the preparation of component A can be achieved by mixing polyvinyl alcohol, wood flour and water to obtain component A.
[0023] In one embodiment of the present invention, the mixing of polyvinyl alcohol, wood flour, and water can be performed by first mixing polyvinyl alcohol and water, and then adding wood flour for a second mixing. In another embodiment, the first mixing is carried out under heating conditions, the heating temperature can be 90-95°C, and the heating time can be 1-3 hours; the first and second mixing are carried out under stirring. The present invention does not have specific limitations on the specific stirring operation; any stirring method well known in the art can be used to mix polyvinyl alcohol, wood flour, and water evenly.
[0024] The adhesive provided by this invention includes a component B packaged separately from component A, wherein component B includes sodium acetate. This invention utilizes the phase change properties of sodium acetate in the processing or repair of wood panels. At the phase change temperature, sodium acetate can penetrate into the cell cavities and micropores of the cell walls of the wood, and upon cooling, it forms elongated crystals that create a strong interlocking structure with the wood surface, improving adhesion. The salting-out properties of sodium acetate also cause phase separation between polyvinyl alcohol and water, resulting in more hydrogen bonds between polyvinyl alcohol molecules, further enhancing adhesion. When the bonding or repair interface cracks due to external impact, the sodium acetate in the wood adhesive can re-penetrate into the cell cavities and micropores of the cell walls at the phase change temperature, and upon cooling, form elongated crystals that reform a strong interlocking structure with the wood surface, achieving self-repair. In one embodiment of this invention, the sodium acetate can be sodium acetate trihydrate.
[0025] The present invention does not have a special limitation on the amount of sodium acetate used; it can be adjusted according to the actual bonding size.
[0026] This invention also provides the application of the wood adhesive described above in wood panel processing or repair of damaged wood panels, including: Component A is coated onto the surface of the wood board for bonding, and then immersed in molten component B before being removed and cooled. Alternatively, it may include: filling the damaged area of the damaged wood board with component A, then impregnating it with molten component B, and then removing and cooling it.
[0027] In one embodiment of the present invention, component A is coated onto the surface of a wooden board for bonding, and then immersed in molten component B before being removed and cooled.
[0028] This invention does not impose any particular limitation on the type of wood used; any type of wood well-known in the art may be employed. As one embodiment of this invention, the wood can be bamboo, balsa wood, linden wood, pine, or bamboo.
[0029] The present invention does not have any particular limitation on the coating and bonding method. Component A can be coated and bonded to the surface of the wood board using a coating method well known in the art.
[0030] In one embodiment of the present invention, after the bonding is completed, the bonded wood board is immersed in molten component B and then removed and cooled. In another embodiment of the present invention, dovetail clips can be attached to the four corners of the bonded wood board before immersion to prevent warping. In another embodiment of the present invention, the immersion temperature can be 80-90°C, and the immersion time can be 3-48 hours, or 12-24 hours. The present invention limits the immersion temperature and time to ensure that sodium acetate can fully penetrate the wood cell cavities and cell wall micropores at the immersion temperature. In another embodiment of the present invention, the removal and cooling can be done by natural air drying.
[0031] In another technical solution of the present invention, component A is filled into the damaged part of the damaged wood board, and then it is immersed in molten component B and then taken out and cooled.
[0032] This invention does not impose any particular limitations on the type, location, or extent of damage to the damaged wood board; commonly used damaged wood boards in the art can be used. In one embodiment of this invention, the impregnation time can be 12-24 hours. In another embodiment of this invention, the preparation of component A is the same as that of component A in the wood board processing described above, and will not be repeated here. This invention does not impose any particular limitations on the filling method; any filling method well-known in the art can be used to fill the damaged area of the damaged wood board. The impregnation temperature and the cooling method are the same as those used in the wood board processing described above, and will not be repeated here.
[0033] The wood adhesive of this invention is applied to the bonding interface formed after bonding or repairing wood boards. After the bonding interface or repair interface cracks due to external impact, the sodium acetate crystals in the bonding interface or repair interface can remelt at the phase transition temperature and penetrate into the wood cell cavity and cell wall micropores. After cooling, they form slender crystals and re-form a strong interlocking structure with the wood board surface, thus achieving self-repair.
[0034] In this invention, the self-healing temperature is preferably 80~90℃; the time is preferably 10~30min, more preferably 12~20min.
[0035] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.
[0036] Example 1 A wood adhesive, comprising separately packaged component A and component B: Component A comprises: polyvinyl alcohol 1799 particles (purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.) with a degree of alcoholysis of 99% and a molecular weight of 75,000, 300-mesh poplar wood powder (Hongyao Mineral Products Processing Co., Ltd.), and water; the mass of the poplar wood powder is 25% of the mass of the polyvinyl alcohol; the mass of the polyvinyl alcohol is 10% of the mass of the water. Component B is sodium acetate trihydrate (Maclean Biochemical Technology Co., Ltd.).
[0037] The preparation method of component A is as follows: dissolve polyvinyl alcohol (PVA) in water at 95°C, stir in an oil bath at 95°C for 2 hours, mix with poplar wood powder and stir evenly to obtain a slurry, denoted as PVA / W.
[0038] Application Example 1 Component B of Example 1 was melted at 80°C to obtain molten sodium acetate, denoted as SAT; After coating the surface of poplar wood board with component A of Example 1 for bonding, the board was immersed in the molten sodium acetate for 24 hours, removed and air-dried to obtain poplar wood board. The adhesive obtained at the bonding interface was denoted as PVA / W / SAT.
[0039] Examples 2-5 The mesh size of the poplar powder in Example 1 was successively replaced with 20 mesh, 60 mesh, 100 mesh and 200 mesh to obtain Example 2, Example 3, Example 4 and Example 5 respectively.
[0040] Application Examples 2-5 The wood adhesive used in Example 1 was replaced sequentially with the wood adhesives used in Examples 2, 3, 4 and 5, respectively, to obtain Example 2, Example 3, Example 4 and Example 5.
[0041] Examples 6-8 The poplar powder purchased in Example 1 was successively replaced with 300-mesh poplar powder made from waste poplar wood fragments, 300-mesh poplar powder made from waste poplar wood shavings, and 300-mesh poplar powder made from waste poplar sawdust, resulting in Examples 6, 7, and 8, respectively.
[0042] Application Examples 6-8 The wood adhesive used in Example 1 was replaced sequentially with the wood adhesives used in Examples 6, 7 and 8 to obtain Example 6, Example 7 and Example 8, respectively.
[0043] Application Examples 9-12 By replacing the immersion time in Application Example 1 with 3h, 6h, 12h, and 48h respectively, we obtain Application Example 9, Application Example 10, Application Example 11, and Application Example 12.
[0044] Application Examples 13-16 By replacing the poplar planks in Application Example 1 with basa planks, linden planks, pine planks, and bamboo planks in sequence, we obtain Application Examples 13, 14, 15, and 16, respectively.
[0045] Examples 17-40 In Example 1, the mass of polyvinyl alcohol was 10% of the mass of water, which was successively replaced with 5%, 7.5%, 12.5% and 15%, respectively, to obtain Examples 17, 18, 19 and 20; In Example 1, the wood flour content was 25% of the polyvinyl alcohol content, which was 10% of the total polyvinyl alcohol content. The polyvinyl alcohol content was successively 5%, 7.5%, 10%, 12.5%, and 15% of the water content, resulting in Examples 21, 22, 23, 24, and 25, respectively. In Example 1, the wood flour was replaced with 15% of the polyvinyl alcohol mass instead of 25%; the polyvinyl alcohol mass was successively 5%, 7.5%, 10%, 12.5%, and 15% of the water mass, resulting in Examples 26, 27, 28, 29, and 30, respectively. In Example 1, the mass of poplar wood powder was replaced with 20% of the mass of polyvinyl alcohol; the mass of polyvinyl alcohol was successively 5%, 7.5%, 10%, 12.5% and 15% of the mass of water, resulting in Examples 31, 32, 33, 34 and 35, respectively. In Example 1, the mass of poplar wood powder was replaced by 25% of the mass of polyvinyl alcohol, which was 30%; the mass of polyvinyl alcohol was successively 5%, 7.5%, 10%, 12.5% and 15% of the mass of water, resulting in Examples 36, 37, 38, 39 and 40, respectively.
[0046] Application Examples 17-40 The wood adhesive used in Example 1 of Application Example 1 was replaced in turn with the wood adhesives used in Examples 17, 18, 19 and 20, respectively, to obtain Application Example 17, Application Example 18, Application Example 19 and Application Example 20; The wood adhesive used in Example 1 was replaced sequentially with the wood adhesives used in Examples 21, 22, 23, 24 and 25 to obtain Example 21, Example 22, Example 23, Example 24 and Example 25, respectively. The wood adhesive used in Example 1 was replaced sequentially with the wood adhesives used in Examples 26, 27, 28, 29 and 30, respectively, to obtain Example 26, Example 27, Example 28, Example 29 and Example 30; The wood adhesive used in Example 1 was replaced sequentially with the wood adhesives used in Examples 31, 32, 33, 34 and 35 to obtain Example 31, Example 32, Example 33, Example 34 and Example 35, respectively. The wood adhesive used in Example 1 was replaced sequentially with the wood adhesives used in Examples 36, 37, 38, 39 and 40, resulting in Example 36, Example 37, Example 38, Example 39 and Example 40, respectively.
[0047] According to GB / T 33333-2016, test examples 1-40 were set up to prepare wood chips to simulate the wood boards prepared in examples 1-40, and comparative test examples 1-17 were set up to compare the shear strength with the test examples. The test examples and comparative test examples are as follows: Test Examples 1-40 The wooden boards in Application Examples 1 to 40 were replaced in turn with wood chips of the corresponding material with a size of 20×20cm; and the coating area was 4×4cm, while the rest were the same as in Application Examples 1 to 40, thus obtaining Test Examples 1 to 40.
[0048] Comparative test cases 1-17 The molten sodium acetate trihydrate in Test Examples 9-12 was replaced with a 1 mol / L sodium acetate trihydrate aqueous solution. After 3 h, 6 h, 12 h, and 48 h, Comparative Test Example 1, Comparative Test Example 2, Comparative Test Example 3 and Comparative Test Example 4 were obtained, respectively. The molten sodium acetate trihydrate in test examples 9-12 was replaced with a 2 mol / L sodium acetate trihydrate aqueous solution. After 3 h, 6 h, 12 h, and 48 h, comparative test examples 5, 6, 7 and 8 were obtained, respectively. The molten sodium acetate trihydrate in test examples 9-12 was replaced with a 3 mol / L sodium acetate trihydrate aqueous solution. After 3 h, 6 h, 12 h, and 48 h, comparative test examples 9, 10, 11 and 12 were obtained, respectively. The molten sodium acetate trihydrate in test examples 9-12 was replaced with a 3 mol / L sodium acetate trihydrate aqueous solution. After 3 h, 6 h, 12 h, and 48 h, comparative test examples 13, 14, 15, and 16 were obtained, respectively. Replace the molten sodium acetate trihydrate in Test Example 1 with molten sodium sulfate decahydrate, keeping everything else the same, to obtain Comparative Test Example 17.
[0049] Test cases 41-43 and comparative test cases 18-21 were set up according to GB / T 228.1-2021 and GB / T 9341-2008 respectively to simulate the tensile and flexural strength of actual damaged wood boards for repair. The test cases and comparative test cases are shown below: Test Case 41 according to Figure 27 The poplar board in Application Example 1 was replaced with a 10×10cm poplar board, and a circular hole was made in the board to simulate a damaged board. The damaged area was filled with PVA / W slurry from Application Example 1, and then the board was immersed in molten sodium acetate trihydrate (Maclean Biochemical Technology Co., Ltd.) for 24 hours. After being removed and air-dried, the repaired poplar board was obtained.
[0050] Test Case 42 according to Figure 32 Prepare three poplar boards, each 10×10cm in size, with circular holes (6.5mm) to simulate damaged boards. First, fill the damaged area of the first poplar board with the PVA / W slurry from Application Example 1. Then, apply PVA / W slurry to the surface of the first poplar board after filling and bond it to the second poplar board. Then, fill the damaged area of the second poplar board with the PVA / W slurry from Application Example 1. Then, apply PVA / W slurry to the surface of the second poplar board after filling and bond it to the third poplar board. Then, fill the damaged area of the third poplar board with the PVA / W slurry from Application Example 1. Then, immerse the boards in molten sodium acetate trihydrate for 24 hours, remove them, and air dry them naturally to obtain a three-layer damaged repaired poplar board, denoted as PVA / W / SAT-LTL. The bonding texture of the three poplar boards is arranged in a longitudinal-transverse-longitudinal pattern.
[0051] Test Case 43 The difference between this test case and test case 42 is that the adhesive texture of the three poplar boards is arranged in a longitudinal-longitudinal-longitudinal pattern, resulting in a three-layer damaged poplar board, denoted as PVA / W / SAT LLL.
[0052] Compare test cases 18-21 The difference between this comparative test case and test case 42 is that the steps of adding poplar powder and impregnating with molten sodium acetate trihydrate are omitted, resulting in the poplar board with three-layer damage repair in comparative test case 18, denoted as PVA LTL. The difference between this comparative test case and test case 42 is that the steps of adding poplar powder and impregnating with molten sodium acetate trihydrate are omitted, resulting in the poplar board with three-layer damage repair in comparative test case 19, denoted as PVA LLL; The difference between this comparative test case and test case 42 is that the impregnation step with molten sodium acetate trihydrate was omitted, resulting in the poplar board with three-layer damage repair in comparative test case 20, denoted as PVA / W LTL. The difference between this comparative test case and test case 43 is that the impregnation step with molten sodium acetate trihydrate was omitted, resulting in the poplar board with three-layer damage repair in comparative test case 21, denoted as PVA / W LLL. Samples were taken from the PVA / W in Example 1, the PVA / W / SAT in Test Example 1, and the PVA / SAT (PVA / SAT was prepared by directly adding polyvinyl alcohol to molten sodium acetate trihydrate to form a gel layer). The phase composition was then characterized using X-ray diffraction. The results are as follows: Figures 1-2 As shown. Figure 1 The XRD comparison diagrams of PVA / W, PVA / W / SAT, and PVA / SAT are shown. As can be seen from the figure, PVA / W / SAT in Test Example 1 of the present invention contains characteristic peaks of PVA, W (poplar wood powder), and SAT (molten sodium acetate trihydrate), indicating that Test Example 1 of the present invention obtained PVA / W / SAT. Figure 2 Yes Figure 1 The magnified images of the peaks of PVA / W and PVA / W / SAT at around 20° show that the peak of PVA / W / SAT is higher than that of PVA / W, and the peak between 20° and 25° is not as obvious as the characteristic peak of PVA / W. This is because the characteristic peak of SAT at this point is a high sharp peak, which further shows that the test example 1 of this invention obtained PVA / W / SAT.
[0053] The molecular structures of PVA / W, PVA / W / SAT, PVA, and PVA / SAT in Test Example 1 were characterized using infrared spectroscopy. The results are as follows: Figures 3-4 As shown. Figure 3 The infrared spectra of PVA / W and PVA / W / SAT are shown in the figure. As can be seen from the figure, the absorption peak of PVA / W / SAT in Test Example 1 of the present invention contains the absorption peak of PVA / W, indicating that PVA / W / SAT in Test Example 1 of the present invention contains PVA and W. Figure 4 These are the infrared spectra of PVA and PVA / SAT. The absorption peak positions of SAT can be determined from these spectra. Figure 3 and Figure 4 The comparison reveals that PVA / W / SAT contains the absorption peak of SAT, further demonstrating that Test Example 1 of this invention yielded PVA / W / SAT.
[0054] The load-bearing capacity of the wood chips in Test Example 1 was tested using a person weighing 80kg, as shown in the schematic diagram. Figure 5 As shown in the figure. It can be seen from the figure that the overlapping bonding area of this invention is only 4cm². 2 Under certain conditions, the bonded wood chips can withstand shear forces exceeding 80 kg without being damaged.
[0055] The shear strength of the wood chips in Test Example 1 was tested using a universal testing machine after shearing in both the SAT molten state (wood chips heated to 80°C to obtain a molten state) and the crystalline state (the prepared wood chips). The results are as follows: Figure 6 As shown in the figure, the shear strength of the wood chips in Test Example 1 after shearing in the SAT molten state and crystalline state is 0.09 MPa and 4.95 MPa, respectively. It can be seen that the shear strength of Test Example 1 of the present invention is significantly improved in the crystalline state.
[0056] The changes in heat absorbed or released during heating or cooling of PVA / W and PVA / W / SAT in Test Example 1 were analyzed using differential scanning calorimetry. The results are as follows: Figure 7 As shown in the figure, the amount of heat absorbed or released by PVA / W during heating or cooling remains unchanged, while PVA / W / SAT absorbs heat during heating and releases heat during cooling, indicating that PVA / W / SAT has phase change properties.
[0057] The wood chips from Test Example 1 were cut, then heated to melt and cooled to crystallize for repair. Before and after photos of the repair were taken with a mobile phone, and the results are as follows. Figure 8 As shown, the shear strength before and after repair was then tested using a universal testing machine, and the results are as follows. Figure 9 As shown in the figure, the shear strengths before and after wood chip repair are 0.08 MPa and 4.84 MPa, respectively; thus, the wood adhesive of Example 1 of the present invention has a self-healing function.
[0058] Differential scanning calorimetry was used to study the changes in heat absorption or release of PVA / W / SAT during heating or cooling after the first and tenth shear self-healing events in test example 1. The results are as follows: Figure 10 As shown in the figure, the PVA / W / SAT in Test Example 1 still maintains good phase change properties after the first and tenth shear self-healing events.
[0059] The wood chips from Test Example 1 were sheared, then heated to melt and cooled to crystallize for repair. This operation was repeated 10 times. The shear strength before and after the 1st, 5th, and 10th repairs was tested using a universal testing machine. The results are as follows: Figure 11As shown in the figure, the shear strengths of the wood chips before and after the 1st, 5th, and 10th repairs were 0.0804 MPa and 4.8422 MPa, 0.07983 MPa and 4.75317 MPa, and 0.07693 MPa and 4.72107 MPa, respectively. Therefore, it can be seen that the wood adhesive of Example 1 of this invention still produces wood chips with good shear strength after multiple shear repairs.
[0060] The load-bearing capacity of the wood chips after the 15th shearing repair in Example 1 was tested using a 25kg bucket, as shown in the schematic diagram. Figure 12 As shown in the figure, the wood chip in Test Example 1 of this invention can still withstand a shear force of over 25 kg without being damaged after the 15th shear repair.
[0061] A dynamic shear load of 200 kPa to -100 kPa was applied to the wood chip after the 15th shear repair in Test Example 1 of this invention. The wood chip was then heated to melt and cooled to crystallize for repair. This operation was repeated 3000 times, and the results are as follows: Figure 13 As shown in the figure, the wood chips were not damaged after 3000 cycles of dynamic shearing at 200kPa to -100kPa, indicating that the wood chips prepared with the wood adhesive of Example 1 of this invention have good bonding stability.
[0062] The shear strength of the wood chips in Test Examples 2-5 after shearing was tested using a universal testing machine, and the results are as follows: Figure 14 As shown in the figure, the shear strength of the wood chips after shearing in Test Examples 2-5 is 1.44303 MPa, 1.6023 MPa, 1.8056 MPa and 2.11797 MPa, respectively. This shows that the wood adhesive of the present invention, using poplar powder of different mesh sizes, still produces wood chips with relatively high shear strength in the crystalline state.
[0063] The shear strength of the wood chips in Test Examples 6-8 after shearing was tested using a universal testing machine, and the results are as follows: Figure 15 As shown in the figure, the shear strengths of the wood chips after shearing in Test Examples 6-8 were 3.336 MPa, 3.360 MPa, and 3.592 MPa, respectively. This indicates that the wood chips obtained from poplar wood powder made from waste poplar wood raw materials in different forms, as used in the wood adhesive of this invention, still have relatively high shear strength in the crystalline state.
[0064] The shear strength of the wood chips in Test Examples 9-12 and Comparative Test Examples 1-16 was tested using a universal testing machine. The results are as follows: Figure 16 As shown in the figure, the shear strength of test examples 9-12 of the present invention is higher than that of the wood chips in comparative test examples 1-16, indicating that the adhesive prepared by molten SAT has better bonding performance for wood chips.
[0065] Images of the wood chips in Test Examples 13-16 before and after shearing in their SAT molten and crystalline states were taken using a mobile phone. The results are shown below. Figures 17-18 As shown, the shear strength of the wood chips in Test Examples 13-16 after shearing in the SAT molten and crystalline states was then tested using a universal testing machine. The shearing results are shown in the figures below. Figure 19 and 20 As shown. By Figure 19 and 20 As can be seen, the shear strengths of the wood chips in Test Examples 13-16 after shearing in the SAT molten and crystalline states were 30.2 kPa and 1.9855 MPa, 37.76667 kPa and 2.0423 MPa, 50.33333 kPa and 2.56583 MPa, and 66.7 kPa and 2.73867 MPa, respectively. This shows that the wood adhesive of the present invention has high shear strength in the crystalline state for different types of wood.
[0066] The adhesion properties of wood chips in Test Examples 13-16 in both the molten and crystalline states of SAT were tested and simulated using COMSOL Multiphysics software. The results are as follows: Figure 21 As shown in the figure, stress concentration easily occurs in the molten state of SAT during the shear test, leading to premature bond failure. Under high shear stress, the deformation of the crystalline state of SAT is negligible, while the deformation in the molten state is significant under the same load.
[0067] The shear strength of the wood chips in Test Examples 17-40 was tested using a universal testing machine, and the results are as follows: Figure 22 As shown in the figure, the shear strength of test examples 17-40 of the present invention is in the range of 1.17-3.57 MPa, indicating that the adhesives used in examples 17-40 have good bonding performance when used to bond wood chips.
[0068] Images of sodium acetate trihydrate and sodium sulfate decahydrate in their molten and crystalline states in the bottle were taken using a mobile phone. The results are as follows: Figure 23 As shown in the figure, SAT crystals form a hard, stable, and effective crystal structure, while SSD crystals collapse and deform, forming loose, flocculent crystals.
[0069] Images of sodium acetate trihydrate and sodium sulfate decahydrate in their molten and crystalline states after being removed from the bottle were taken using a mobile phone. The results are as follows: Figure 24 As shown in the figure, SAT crystals form a hard, stable, and effective crystal structure, while SSD crystals collapse and deform, forming loose, flocculent crystals.
[0070] The morphology of sodium acetate trihydrate and sodium sulfate decahydrate in the crystalline state was characterized using a mobile phone and a scanning electron microscope, respectively. The results are as follows: Figure 25 As shown in the figure, there are four smaller images. The top left and bottom left images are surface morphology images of sodium acetate trihydrate taken with a mobile phone and observed under a scanning electron microscope, respectively. It can be seen that sodium acetate trihydrate crystallizes into slender crystals. The top right and bottom right images are surface morphology images of sodium sulfate decahydrate taken with a mobile phone and observed under a scanning electron microscope, respectively. It can be seen that sodium sulfate decahydrate crystallizes into loose blocky crystals with uneven size distribution.
[0071] The shear strength of the wood chips in comparative test example 17 was tested using a universal testing machine, and the results are as follows: Figure 26 As shown in the figure, comparing the shear strength of wood with different added hydrated salts, it is clear that the shear strength of PVA / W / SAT is much stronger than that of PVA / W / SSD.
[0072] The images of the damaged wood chips in Test Example 41 before and after repair were taken using a mobile phone. The results are as follows: Figure 27 As shown, the morphology of the damaged areas of the damaged wood chip in Test Example 41 before and after repair was characterized using scanning electron microscopy. The results are shown in the figures below. Figure 28 , 29 As shown in the figure. From the figure, we can see that: Figure 28 Test Example 41: Before repair, the damaged area of the damaged wood chip was the fracture surface. Figure 29 In Test Example 41, the damaged area was filled after the damaged wood chip was repaired.
[0073] The longitudinal and transverse tensile tests were performed on the damaged wood chip of Test Example 41 before and after repair using a universal testing machine, and the results are as follows: Figure 30 As shown in the figure, the tensile stresses after longitudinal and transverse stretching before and after repair of the damaged wood chip in Test Example 41 were 12.7652 MPa, 47.6821 MPa, 6.6065 MPa, and 25.0058 MPa, respectively. This indicates that the wood adhesive of Example 1 of the present invention can be used for the repair of damaged wood.
[0074] The images of the repaired damaged wood chip from Test Example 41, after longitudinal and transverse stretching, were taken using a mobile phone. The results are as follows: Figure 31 As shown in the figure, after longitudinal and transverse tensioning, the fracture location of the wood chip repaired in Test Example 41 is not at the original damaged site. This indicates that the tensile stress at the damaged site after repair by the wood adhesive of Example 1 of the present invention is higher than that of the original wood chip.
[0075] Images of the damaged wood chips in Test Example 42 before and after repair were taken using a mobile phone. The results are as follows: Figure 32As shown in the figure. Then, a universal testing machine was used to test the longitudinal and transverse tensile and bending strengths of the damaged wood chips after repair, as well as the damaged and undamaged wood chips in test examples 42-43 and comparative test examples 18-21. The results are as follows. Figure 33 As shown in the figure, the tensile stresses after longitudinal and transverse tension of the damaged wood chips in test examples 42-43 and comparative test examples 18-21 are 85.3443 MPa and 84.09997 MPa, 38.77923 MPa and 20.7248 MPa, 25.44767 MPa and 24.35883 MPa, 17.6877 MPa and 7.24633 MPa, 32.78097 MPa and 32.1937 MPa, 19.7356 MPa and 11.83347 MPa, 11.4565 MPa and 6.12827 MPa, and 41.51183 MPa and 17.98867 MPa, respectively. The results show that the wood adhesive of Example 1 of the present invention, after repairing the damaged wood in Test Examples 42-43, exhibits higher tensile stress than the repaired damaged wood chips, damaged wood chips, and undamaged wood chips in Comparative Test Examples 18-21. The longitudinal and transverse bending strengths of Test Examples 42-43, the repaired damaged wood chips, the damaged wood chips, and the undamaged wood chips in Comparative Test Examples 18-21 are 65.37953 and 58.53174, 47.13392 and 25.64713, 19.4987 and 18.51333, 10.1785 and 4.12731, 36.00527 and 33.57402, 28.46377 and 12.70863, 4.15783 and 2.34003, and 43.26543 and 16.06875, respectively. This indicates that the wood adhesive of Example 1 of the present invention, when used to repair damaged wood in Test Examples 42-43, exhibits higher bending strength than the repaired damaged wood chips, damaged wood chips, and undamaged wood chips in Comparative Test Examples 18-21.
[0076] In summary, the wood adhesive provided by this invention can achieve self-healing when applied to the bonding or repair of wood boards, and the shear strength after repair is higher than that of the original wood board.
[0077] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A wood adhesive comprising separately packaged component A and component B: Component A includes: Polyvinyl alcohol, wood flour, and water; The wood flour comprises 10-30% of the mass of polyvinyl alcohol; the polyvinyl alcohol comprises 5-15% of the mass of water. Component B includes sodium acetate.
2. The wood adhesive according to claim 1, characterized in that, The mass of the wood flour is 13-28% of the mass of polyvinyl alcohol.
3. The wood adhesive according to claim 2, characterized in that, The mass of the wood flour is 20-25% of the mass of polyvinyl alcohol.
4. The wood adhesive according to claim 1, characterized in that, The mass of the polyvinyl alcohol is 7.5 to 12.5% of the mass of water.
5. The wood adhesive according to any one of claims 1 to 4, characterized in that, The polyvinyl alcohol has a molecular weight of 25,000 to 300,000 and a degree of alcoholysis of 98 to 99%.
6. The wood adhesive according to claim 1, characterized in that, The wood flour has a mesh size of 20-300 mesh.
7. The wood adhesive according to claim 6, characterized in that, The wood flour has a mesh size of 100-300 mesh.
8. The application of the wood adhesive according to any one of claims 1 to 7 in the processing of wood panels or the repair of damaged wood panels, characterized in that, include: Component A is coated onto the surface of the wood board for bonding, and then immersed in molten component B before being removed and cooled. Alternatively, it may include: filling the damaged area of the damaged wood board with component A, then impregnating it with molten component B, and then removing and cooling it.
9. The application according to claim 8, characterized in that, The immersion temperature is 80~90℃, and the immersion time is 3~48h.
10. The application according to claim 9, characterized in that, The immersion temperature is 80~90℃, and the immersion time is 12~24h.