Curing prediction method of wood prepreg, preparation method of wood recombination material and wood recombination material

Abstract

The invention provides a curing prediction method of a wood prepreg, a preparation method of a wood recombination material and the wood recombination material. The method comprises the following steps: at different curing temperatures, measuring the curing degrees of a resin material at different curing times; obtaining a curing conversion rate curved surface; the method comprises the following steps: impregnating a wood unit by using a resin material, and drying to obtain a wood prepreg; on the basis of the curing conversion rate curved surface, curing time and curing temperature of the wood prepreg corresponding to different curing degrees are obtained, hot pressing treatment is conducted on the wood prepreg on the basis of the curing time and the curing temperature, and forming bodies with different curing degrees are obtained; measuring the physical and mechanical properties of each formed body; carrying out nonlinear relation fitting on the curing degree and the physical and mechanical properties of the molded body to obtain a relation curve; and providing a to-be-tested wood prepreg, obtaining a curing degree target value based on the physical and mechanical property target value, and obtaining optimized hot pressing process conditions of the to-be-tested wood prepreg based on the curing conversion rate curved surface.

Description

Technical Field

[0001] The present invention relates to a method for predicting the curing of a wood prepreg, a method for preparing a wood recombined material, and a wood recombined material, belonging to the field of wood material preparation. Background Art

[0002] Recombined materials mainly use biomass resources such as plantation wood, bamboo, and shrubs as raw materials, and use fiber orientation separation technology to prepare recombined units, which are high-performance materials obtained through resin impregnation, drying, and hot pressing. There are mainly two major series of products, recombined bamboo and recombined wood. At present, these material products have been widely used in many fields such as construction and transportation facilities. The breakthrough of recombined material production technology provides a key solution to issues such as ensuring the safe supply of China's wood resources and the efficient utilization of plantation wood and bamboo, and has great strategic value.

[0003] The preparation of recombined materials requires multiple heating processes such as drying of the unit before sizing, drying of the prepreg, and hot pressing. The process parameters have a great impact on the subsequent processes and properties of the materials. At present, in order to efficiently and energy-savingly control the hot pressing process parameters in the method for preparing recombined materials and thus obtain an optimized manufacturing process suitable for the target properties of the product, two technical difficulties need to be solved: First, as a reinforcing phase in the recombined technology, the resin forms a new prepreg system after impregnating with wood units. Its rheological properties, reaction properties, and curing properties still lack effective prediction and control technologies, and a relationship between the curing time and curing temperature and the curing degree of the prepreg and its corresponding prediction method need to be established; Second, the mutual relationship between the curing degree of the prepreg and the final physical and mechanical properties of the recombined material has not been established, and the curing reaction and target property prediction in the forming process of the recombined material are not accurate enough, resulting in limited improvement in the product performance and production efficiency of the recombined material.

[0004] Citation Document 1 discloses a method for predicting the curing reaction of a resin matrix composite material. Using the dynamic differential scanning calorimetry test data of the resin matrix composite prepreg, non-linear fitting is performed on the nth-order curing reaction kinetic model and the autocatalytic curing reaction kinetic model to obtain the resin matrix composite curing reaction kinetic model; then, the obtained resin matrix composite curing reaction kinetic model is used to predict the curing process of the resin matrix composite material. This method can simulate the curing process of the resin matrix composite material with high accuracy and can relatively accurately predict the curing process of the resin matrix composite material. However, this method mainly focuses on the composite material curing reaction system and does not combine the target properties of the composite material, and has certain limitations in establishing the mutual relationship and prediction method among the preparation process, reaction process, and product properties.

[0005] Therefore, the existing manufacturing technology of wood recombined materials urgently needs a systematic and accurate prediction method and preparation method to guide the actual production of high-performance products, high production efficiency, energy conservation, and consumption reduction.

[0006] Cited Reference 1: CN110197009A Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] In view of the technical problems existing in the prior art, such as: the lack of effective prediction and control technology for the curing kinetics model of prepreg, the inaccurate prediction of the curing reaction and target properties in the forming process of wood-based recombinant materials, the limited improvement of the product properties and production efficiency of recombinant materials, etc., the present invention first provides a method for predicting the curing of wood-based prepreg.

[0009] Furthermore, the present invention also provides a method for preparing wood-based recombinant materials. By establishing the relationship and prediction method among the hot pressing process, curing kinetics and physical and mechanical properties, the present invention obtains a method for preparing wood-based recombinant materials with an optimized hot pressing process according to the requirements of the physical and mechanical properties of the materials.

[0010] Furthermore, the present invention also provides a wood-based recombinant material.

[0011] Solutions for Solving the Problems

[0012] [1]. A method for predicting the curing of wood-based prepreg, which comprises the following steps:

[0013] Measure the degree of cure of the resin material at different curing times at different curing temperatures;

[0014] Perform surface fitting on the degree of cure, curing time and curing temperature of the resin material, establish a functional relationship between the degree of cure, curing time and curing temperature, and obtain a curing conversion rate surface;

[0015] Impregnate the wood units with the resin material and then dry to obtain wood-based prepreg;

[0016] Based on the curing conversion rate surface, obtain the curing time and curing temperature of the wood-based prepreg corresponding to different degrees of cure, and perform hot pressing treatment on the wood-based prepreg based on the curing time and curing temperature to obtain formed bodies with different degrees of cure;

[0017] Measure the physical and mechanical properties of each formed body;

[0018] Perform non-linear relationship fitting between the degree of cure and the physical and mechanical properties of the formed body, establish a functional relationship between the degree of cure and the physical and mechanical properties, and obtain a relationship curve;

[0019] Provide the wood prepreg to be tested. Based on the target values of the physical and mechanical properties of the wood prepreg to be tested, obtain the target value of the degree of cure using the relationship curve, and based on the cure conversion rate surface, obtain the optimized hot pressing process conditions for the wood prepreg to be tested.

[0020] [2], According to the cure prediction method described in [1] above, wherein the cure temperature of the resin material is 110 - 170 °C, and the temperature interval between two adjacent cure temperatures is 1 - 10 °C.

[0021] [3], According to the cure prediction method described in [1] or [2] above, wherein the resin material includes one or a combination of two or more of phenolic resin, epoxy resin, polyurethane resin, urea - formaldehyde resin, melamine - formaldehyde resin, and polyimide resin.

[0022] [4], According to the cure prediction method described in any one of [1] - [3] above, wherein the conductivity of the resin material is measured using a dielectric cure detector, and based on the relationship between conductivity and the degree of cure, obtain the degree of cure of the resin material.

[0023] [5], According to the cure prediction method described in any one of [1] - [4] above, wherein the relationship between the degree of cure of the resin material and conductivity is as shown in the following formula (1):

[0024]

[0025] Wherein, α represents the degree of cure of the resin;

[0026] σ min represents the minimum value of conductivity during the test;

[0027] σ represents the conductivity of the resin.

[0028] [6], According to the cure prediction method described in any one of [1] - [5] above, wherein based on the functional relationship between the degree of cure and cure time of the resin material at different cure temperatures, fit the functional relationship between the degree of cure and cure time and cure temperature of the resin material to obtain the cure conversion rate surface with cure time and cure temperature as variables.

[0029] [7], According to the cure prediction method described in any one of [1] - [6] above, wherein the fitting result of the relationship curve includes a 95% confidence band and a 95% prediction band, and wherein the relationship curve is represented by formula (2):

[0030] X n = g(α) (2)

[0031] Wherein, X n represents the physical and mechanical properties;

[0032] α represents the degree of curing.

[0033] [8] The curing prediction method according to any one of the above [1]-[7], wherein the physical and mechanical properties include flexural elastic modulus, static bending strength, water absorption width swelling rate or water absorption thickness swelling rate.

[0034] [9] A method for preparing a wood recombined material, which obtains optimized hot pressing process conditions according to the curing prediction method of the wood prepreg according to any one of the above [1]-[7], and prepares the wood recombined material based on the hot pressing process conditions.

[0035]

[10] A wood recombined material, characterized in that it is prepared according to the preparation method described in the above [9].

[0036] Effects of the invention

[0037] The curing prediction method of the wood prepreg of the present invention effectively predicts and regulates its rheological characteristics, reaction characteristics and curing characteristics by predicting the curing of the wood prepreg, and establishes a curing reaction kinetic model of the prepreg, providing data support for the hot pressing process in the preparation process of the recombined material.

[0038] Furthermore, the present invention establishes a direct feedback mechanism of hot pressing process parameters on product performance by fitting the functional relationship between the physical and mechanical properties of the wood recombined material and the degree of curing, providing accurate and reliable process parameters for the hot pressing forming technology of the recombined material, while improving the performance and production efficiency of the recombined product, and also achieving the effect of energy conservation and consumption reduction. Brief description of the drawings

[0039] Figure 1 Shows the relationship curves of the conductivity and the degree of curing of the water-soluble phenolic resin varying with the curing time under the isothermal curing conditions at different curing temperatures, wherein (a) is the relationship curve of the conductivity varying with the curing time, and (b) is the relationship curve of the degree of curing varying with the curing time;

[0040] Figure 2 Is a schematic diagram of the curing conversion rate surface of Example 1 of the present invention;

[0041] Figure 3 Is the relationship curve between the degree of curing and the water absorption thickness swelling rate of the wood prepreg of Example 1 of the present invention;

[0042] Figure 4 Is a schematic diagram of the curing conversion rate surface of Example 2 of the present invention;

[0043] Figure 5 Is the relationship curve between the degree of curing and the water absorption rate of the wood prepreg of Example 2 of the present invention;

[0044] Figure 6 Schematic diagram of the curing conversion rate surface for Embodiment 3 of the present invention;

[0045] Figure 7 Relationship curve between the curing degree and the bending strength of the wood prepreg for Embodiment 3 of the present invention. Detailed implementation manners

[0046] Various exemplary embodiments, features, and aspects of the present invention will be described in detail below. The special word "exemplary" here means "serving as an example, embodiment, or illustration". Any embodiment described as "exemplary" here does not have to be construed as superior to or better than other embodiments.

[0047] In addition, to better illustrate the present invention, numerous specific details are given in the following detailed implementation manners. Those skilled in the art should understand that the present invention can also be implemented without some specific details. In other instances, methods, means, equipment, and steps well-known to those skilled in the art are not described in detail to highlight the gist of the present invention.

[0048] Unless otherwise stated, the units used in this specification are all international standard units, and the numerical values and numerical ranges appearing in the present invention should be understood to include the inevitable systematic errors in industrial production.

[0049] In this specification, the meaning expressed by using "may" includes both the meaning of performing a certain process and the meaning of not performing a certain process.

[0050] In this specification, the so-called "some specific / preferred implementation manners", "other specific / preferred implementation manners", "implementation manners", etc. refer to the specific elements (for example, features, structures, properties, and / or characteristics) related to the implementation manner described are included in at least one of the implementation manners described here, and may exist in other implementation manners or may not exist in other implementation manners. In addition, it should be understood that the elements can be combined in various implementation manners in any suitable way.

[0051] In this specification, the numerical range represented by using "numerical value A to numerical value B" refers to the range including the endpoint numerical values A and B.

[0052] The present invention provides a method for predicting the curing of a wood prepreg, which includes the following steps:

[0053] Measure the curing degree of the resin material at different curing times at different curing temperatures;

[0054] Perform a surface fitting on the degree of cure, curing time, and curing temperature of the resin material, establish a functional relationship between the degree of cure, curing time, and curing temperature, and obtain a cure conversion rate surface;

[0055] Impregnate the wood units with the resin material and then dry them to obtain wood prepregs;

[0056] Based on the cure conversion rate surface, obtain the curing time and curing temperature of the wood prepregs corresponding to different degrees of cure, and perform hot pressing on the wood prepregs based on the curing time and curing temperature to obtain molded articles with different degrees of cure;

[0057] Measure the physical and mechanical properties of each of the molded articles;

[0058] Perform a non-linear relationship fitting between the degree of cure and the physical and mechanical properties of the molded articles, establish a functional relationship between the degree of cure and the physical and mechanical properties, and obtain a relationship curve;

[0059] Provide a wood prepreg to be tested. Based on the target value of the physical and mechanical properties of the wood prepreg to be tested, use the relationship curve to obtain the target value of the degree of cure, and based on the cure conversion rate surface, obtain the optimized hot pressing process conditions for the wood prepreg to be tested.

[0060] Generally, the curing temperature of the resin material is 110 - 170 °C. For example, the degree of cure of the resin material at different curing times can be measured at curing temperatures such as 115 °C, 120 °C, 125 °C, 130 °C, 135 °C, 140 °C, 145 °C, 150 °C, 155 °C, 160 °C, 165 °C, etc.; when measuring the degree of cure of the resin material at different curing times at different curing temperatures, the temperature interval between two adjacent curing temperatures is 1 - 10 °C, for example, 2 °C, 3, 4 °C, 5 °C, 6 °C, 7 °C, 8 °C, 9 °C, etc.

[0061] In some specific embodiments, the present invention preferably uses a dielectric curing detector to measure the conductivity of the resin, and based on the relationship between the conductivity and the degree of cure, obtain the degree of cure of the resin material.

[0062] Specifically, the dielectric curing detector can perform isothermal curing process detection under different curing temperature conditions, thereby deriving a curing reaction model. Specifically, the dielectric curing detector can obtain the complex relative permittivity based on the measured sinusoidal voltage V * , sinusoidal current I * , and angular frequency ω and according to Equation (1-a):

[0063]

[0064] where ε * represents the complex permittivity;

[0065] V * represents the sinusoidal alternating excitation voltage continuously applied by the sensor to the phenolic resin;

[0066] ω represents the angular frequency;

[0067] I * represents the measured output current signal;

[0068] A represents the contact area between the electrode and the material;

[0069] D represents the electrode spacing;

[0070] ε0 is the vacuum permittivity, which is 8.85×10 -12 F / m;

[0071] Then, according to Equation (1-b), the dielectric loss factor ε″ is obtained:

[0072] ε * = ε′ - iε″ (1-b)

[0073] ε′ represents the dielectric constant, from the dielectric energy storage (capacitance) part of the material;

[0074] ε″ represents the dielectric loss factor, from the dielectric loss part of the material;

[0075] i is the imaginary unit in complex numbers.

[0076] Then, based on ε″ obtained according to Equation (1-b), the conductivity σ can be calculated according to the following Equation (1-c):

[0077] σ = ε″·ε0·ω (1-c)

[0078] The above calculation processes are all carried out inside the dielectric curing detector, that is, using the dielectric curing detector, the conductivity of the resin material can be directly obtained.

[0079] Furthermore, at an appropriate frequency, this conductivity mainly reflects the number of ions in the resin material and its mobility changes with temperature and curing development. Since the resistivity is consistent with the viscosity change law of the resin material during the fluidization and crosslinking processes, the reciprocal of the conductivity, that is, the resistivity, can be used to characterize the dynamic curing process of the resin material. That is, the curing degree of the resin material is proportional to the reciprocal of the conductivity. Therefore, in the present invention, after conversion, the following relationship exists between the curing degree of the resin material and the conductivity:

[0080]

[0081] where α represents the curing degree of the resin;

[0082] σ minRepresents the minimum conductivity value during the test;

[0083] σ represents the conductivity of the resin.

[0084] After obtaining the conductivity of the resin material by using a dielectric curing detector, the curing degree of the resin material can be surface-fitted with the curing time and curing temperature, and the functional relationship between the curing degree and the curing time and curing temperature can be established to obtain the curing conversion rate surface. Specifically, based on the functional relationship f(t) between the curing degree α and the curing time t of the resin material at different curing temperatures, the functional relationship f(t,T) between the curing degree α and the curing time t and the curing temperature T of the resin material can be fitted, that is: α = f(t,T). And draw the 3D function graph of f(t,T) to obtain the curing conversion rate surface with the curing time t and the curing temperature T as variables.

[0085] It should be noted that for the same set of data, multiple fitting equations can be used to represent α = f(t,T). Therefore, even using the same data, different fitting equations can be obtained. Specifically, table curve software can be used for fitting.

[0086] Further, after obtaining the curing degree of the resin material, a wood prepreg is prepared. Specifically, the preparation method of the wood prepreg includes impregnating the wood units with the resin material and then drying to obtain the wood prepreg.

[0087] In some specific embodiments, the resin material includes one or a combination of two or more of phenolic resin, epoxy resin, polyurethane dendrimer, urea-formaldehyde resin, melamine-formaldehyde resin, and polyimide resin. Among them, the solid content of the resin material can be 30-60%, for example: 35%, 40%, 45%, 50%, 55%, etc.

[0088] Specifically, the veneer is impregnated in the resin material and then dried to obtain the wood prepreg. Specifically, the temperature of the drying treatment is 40-100°C, for example: 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, etc.; the time of the drying treatment is 0.5-5h, for example: 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, etc. After drying, a wood prepreg can be obtained. Among them, the moisture content of the wood prepreg can be 1-20%, for example: 2%, 5%, 8%, 10%, 12%, 15%, 18%, etc.

[0089] Further, based on the curing conversion rate surface, the curing time and curing temperature of the wood prepreg corresponding to different degrees of curing are obtained, and the wood prepreg is hot-pressed based on the curing time and curing temperature to obtain formed bodies with different degrees of curing. For a formed body with a specific degree of curing, the hot-pressing temperature is the curing temperature, and the hot-pressing time is the curing time.

[0090] In the present invention, in order to make the results more accurate, the number of wood prepregs can be more than 3, specifically 5 - 20, for example: 8, 10, 12, 15, 18, etc.

[0091] Further, the physical and mechanical properties of each formed body are measured; by establishing the relationship between the physical and mechanical properties and the degree of curing, the degree of curing of the formed body is determined, and further, the optimized hot-pressing process conditions are obtained through the curing conversion rate surface.

[0092] In some specific embodiments, the fitting result of the relationship curve includes a 95% confidence band and a 95% prediction band, wherein the relationship curve is expressed by Equation (2):

[0093] X n = g(α) (2)

[0094] wherein, X n represents the physical and mechanical properties;

[0095] α represents the degree of curing.

[0096] In some specific embodiments, the physical and mechanical properties include flexural modulus of elasticity, static bending strength, water absorption width swelling rate or water absorption thickness swelling rate. Based on the physical and mechanical properties, the optimized hot-pressing process conditions of the wood prepreg to be tested can be obtained by the method of the present invention.

[0097] Since different relationship curves may be obtained for different physical and mechanical properties, therefore, in the present invention, the specific equation of the relationship curve is not further limited and can be obtained according to the fitting result.

[0098] <Second aspect>

[0099] The second aspect of the present invention provides a method for preparing a wood recombined material, which obtains optimized hot-pressing process conditions according to the curing prediction method of the wood prepreg described in the first aspect of the present invention, and prepares the wood recombined material based on the hot-pressing process conditions.

[0100] Further, the present invention also provides a wood recombined material prepared according to the preparation method described in the present invention.

[0101] Examples

[0102] The embodiments of the present invention will be described in detail below in conjunction with examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. For those not specified in the examples, they are carried out under conventional conditions or conditions recommended by the manufacturer. For reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0103] Example 1

[0104] Using a dielectric curing detector, the conductivity σ of water-soluble phenolic resin (solid content 52.17%) was measured under different curing temperatures (110°C, 120°C, 130°C, 150°C, 170°C) and different curing times (0 - 70 min). And the relationship curve of the conductivity changing with the curing time under the isothermal curing conditions at different curing temperatures of the water-soluble phenolic resin was obtained, as specifically shown in Figure 1 Figure (a).

[0105] Through the following relational formula (1), the relationship curve α = f(t) of the curing degree of the water-soluble phenolic resin changing with the curing time can be obtained, and the result is shown in Figure 1 Figure (b).

[0106]

[0107] Among them, α represents the curing degree of the water-soluble phenolic resin;

[0108] σ min represents the minimum value of the conductivity during the test;

[0109] σ (t) represents the conductivity value of the water-soluble phenolic resin at different times.

[0110] Based on the functional relationship f(t) between the curing degree α and the curing time t of the water-soluble phenolic resin at different curing temperatures, the functional relationship f(t, T) between the curing degree α, the curing time t and the curing temperature T of the water-soluble phenolic resin was established using table curve software, as shown in the following formula (2). And a 3D function graph of f(t, T) was plotted to obtain a curing conversion rate surface with the curing time t and the curing temperature T as variables, as shown in Figure 2 Figure.

[0111] α = f(t, T) = 1.629 - 0.012t - 0.029T + 0.0002t 2 + 0.0002T 2 + 9.568tT +

[0112] 4.267t 3 - 5.036T 3 + 3.990tT2 -1.840t 2 T(2)

[0113] Impregnate the poplar veneer with water-soluble phenolic resin with a solid content of 52.17%, and then perform a drying treatment. The drying temperature is 65°C and the drying time is 2h to obtain a wood prepreg. The moisture content of the wood prepreg is 10%.

[0114] Take 11 wood prepregs, and according to the curing conversion rate surface of formula (2) and the curing temperature and curing time data in Table 1 below, perform hot pressing and re-forming on the 11 wood prepregs to obtain a formed body. Then, according to GB / T40247—2021, perform a 28h water absorption thickness swelling rate test on the 11 formed bodies, and the results are shown in Table 1 below.

[0115] Table 1 Hot pressing process and performance indicators corresponding to the recombinant materials at different curing degrees

[0116] Curing time / min Curing temperature / °C Degree of curing / % Water absorption thickness swelling rate / % 37.4 120 50 17.466 24.2 130 55 14.043 40.4 130 60 13.063 28.0 150 65 9.333 37.2 150 70 8.323 21.6 170 75 6.937 27.9 170 80 6.536 36.8 170 85 4.668 49.0 170 90 4.959 66.7 170 95 3.698 97.1 170 100 3.624

[0117] The functional relationship between the curing degree and the water absorption thickness swelling rate of the 11 wood prepregs is non-linearly fitted. The fitting results include a 95% confidence band and a 95% prediction band, as Figure 3 shown, and the fitting results are shown in the following formula (3):

[0118]

[0119] If a recombinant material with a water absorption thickness swelling rate of 3.698% is to be obtained, the corresponding curing degree can be calculated to be approximately 95% according to the fitting formula (3). Then, according to the isothermal curing curve α = f(t, T), the curing time t and the curing temperature T can be obtained, so as to obtain a hot pressing time of approximately 67.01min and a hot pressing temperature of approximately 170°C. Therefore, according to the target value of the water absorption thickness swelling rate of the recombinant material product, the hot pressing process can be used to re-form the dried prepreg, where the hot pressing time is 67.01min and the hot pressing temperature is set at 170°C to prepare the wood recombinant material product.

[0120] Prepare and verify the wood recombinant material through a hot pressing device, set the hot pressing time to 67.01min, the hot pressing temperature to 170°C, and the hot pressing pressure to 20MPa. And refer to GB / T40247—2021 to perform a 28h water absorption thickness swelling rate test. The comparison results between the fitting calculation results and the actual test results are shown in Table 2.

[0121] Table 2 Verification comparison of the performance indicators of the recombinant materials

[0122]

[0123] As can be seen from Table 2, the detection method of the present invention is accurate and reliable.

[0124] Example 2

[0125] Using a dielectric curing detector, the conductivity σ of water-soluble phenolic resin (solid content 52.17%) was tested under different curing temperatures (110°C, 120°C, 130°C, 150°C, 170°C) and different curing times (0 - 70 min), and the relationship curve of the conductivity changing with the curing time of the water-soluble phenolic resin under the isothermal curing conditions at different curing temperatures was obtained, as specifically shown in Figure 1 (a) of.

[0126] Through the following relational formula (1), the relationship curve α = f(t) of the curing degree of the water-soluble phenolic resin changing with the curing time can be obtained, and the result is as shown in Figure 1 (b).

[0127]

[0128] Among them, α represents the curing degree of the water-soluble phenolic resin;

[0129] σ min represents the minimum value of the conductivity during the test;

[0130] σ (t) represents the conductivity value of the water-soluble phenolic resin at different moments.

[0131] Through the functional relationship f(t) between the curing degree α and the curing time t of the water-soluble phenolic resin at different curing temperatures, the functional relationship f(t, T) between the curing degree α and the curing time t and the curing temperature T of the water-soluble phenolic resin was established using table curve software, as shown in the following formula (2). And a 3D function graph of f(t, T) was plotted to obtain a curing conversion rate surface with the curing time t and the curing temperature T as variables, as shown in Figure 4 .

[0132]

[0133] Eucalyptus wood defibrated veneers were impregnated with water-soluble phenolic resin with a solid content of 52.17%, and then dried. The drying temperature was 65°C and the drying time was 2 h to obtain wood pre-impregnated materials, among which the moisture content of the wood pre-impregnated materials was 10%.

[0134] Take 11 wood prepregs and perform hot-press recombination molding on the 11 wood prepregs according to the curing temperature and curing time data in Table 3 below based on the curing conversion rate surface of Equation (2) to obtain a molded body. Then, perform a 28-hour water absorption test on the 11 molded bodies according to GB / T40247—2021. The results are shown in Table 3 below and Table 1 below.

[0135] Table 3 Hot-press process and performance indicators corresponding to the recombination materials at different degrees of curing

[0136] Curing time / min Curing temperature / °C Degree of curing / % Water absorption rate / % 37.4 120 50 7.937 24.2 130 55 7.028 40.4 130 60 5.563 28.0 150 65 4.592 37.2 150 70 3.818 21.6 170 75 3.396 27.9 170 80 3.051 36.8 170 85 1.996 49.0 170 90 1.837 66.7 170 95 1.843 97.1 170 100 1.649

[0137] The functional relationship between the degree of curing and water absorption of the 11 wood prepregs was non-linearly fitted. The fitting results include a 95% confidence band and a 95% prediction band, as Figure 5 shown. The fitting results are shown in Equation (3) below:

[0138]

[0139] If a recombination material with a water absorption rate of 1.837% is to be obtained, the corresponding degree of curing can be calculated to be approximately 90% according to the fitting Equation (3). Then, the curing time t and temperature T can be obtained according to the isothermal curing curve α = f(t, T), so that the hot-press time is approximately 48.75 min and the hot-press temperature is approximately 170°C. Therefore, according to the target water absorption rate of the recombination material product, hot-press molding can be performed on the dried prepregs using a hot-press process, where the hot-press time is 48.75 min and the hot-press temperature is set at 170°C to prepare the wood recombination material product.

[0140] Prepare and verify the wood recombination material through a hot-press device, set the hot-press time to 49.04 min, the hot-press temperature to 170°C, and the hot-press pressure to 20 MPa. And perform a 28-hour water absorption test with reference to GB / T40247—2021. The comparison results between the fitting calculation results and the actual test results are shown in Table 4.

[0141] Table 4 Verification comparison of the performance indicators of the recombination materials

[0142]

[0143] As can be seen from Table 4, the detection method of the present invention is accurate and reliable.

[0144] Example 3

[0145] Using a dielectric curing detector, the conductivity σ of water-soluble phenolic resin (solid content: 52.17%) was measured under different curing temperatures (110°C, 120°C, 130°C, 150°C, 170°C) and different curing times (0 - 70 min). The relationship curve of the conductivity of the water-soluble phenolic resin changing with the curing time under the isothermal curing conditions at different curing temperatures was obtained, as shown specifically in Figure 1 Figure (a) of

[0146] Through the following relational formula (1), the relationship curve α = f(t) of the curing degree of the water-soluble phenolic resin changing with the curing time can be obtained, and the results are as follows Figure 1 Figure (b) of

[0147]

[0148] where α represents the curing degree of the water-soluble phenolic resin;

[0149] σ min represents the minimum value of the conductivity during the test;

[0150] σ (t) represents the conductivity value of the water-soluble phenolic resin at different times.

[0151] Based on the functional relationship f(t) between the curing degree α and the curing time t of the water-soluble phenolic resin at different curing temperatures, the functional relationship f(t, T) between the curing degree α, the curing time t, and the curing temperature T of the water-soluble phenolic resin was established using table curve software, as shown in the following formula (2). And the 3D function graph of f(t, T) was plotted to obtain the curing conversion rate surface with the curing time t and the curing temperature T as variables, as shown in Figure 6 Figure

[0152] α = f(t, T) = 0.378 - 0.003t - 0.002T - 4.573t 2 + 1.791T 2 + 7.812tT (2)

[0153] The Chinese fir defibrated veneer was impregnated with water-soluble phenolic resin with a solid content of 52.17%, and then dried. The drying temperature was 65°C and the drying time was 2 h to obtain a wood pre-impregnated material. The moisture content of the wood pre-impregnated material was 10%;

[0154] The wood pre-impregnated material was divided into 11 groups. According to the curing temperature and curing time data in Table 5 below and the curing conversion rate surface of formula (2), the 11 groups of wood pre-impregnated materials were hot-pressed and recombined into shaped bodies. Then, referring to GB / T 17657 - 2022, the flexural strength tests of the 11 shaped bodies were carried out, and the results are shown in Table 5 below.

[0155] Table 5 The hot pressing process and performance indicators corresponding to the recombinant materials at different degrees of curing

[0156] Curing time / min Curing temperature / °C Degree of curing / % Flexural strength / MPa 37.4 120 50 107.388 24.2 130 55 115.957 40.4 130 60 121.297 28.0 150 65 123.475 37.2 150 70 120.418 21.6 170 75 115.572 27.9 170 80 110.527 36.8 170 85 101.458 49.0 170 90 89.457 66.7 170 95 77.626 97.1 170 100 66.469

[0157] The functional relationship between the degree of curing and water absorption of 11 groups of wood prepregs was nonlinearly fitted. The fitting results include a 95% confidence band and a 95% prediction band, as Figure 7 shown. The fitting results are shown in the following formula (3):

[0158]

[0159] If a recombinant material with a bending strength of 123.475 MPa is to be obtained, the corresponding degree of curing can be calculated to be 65% according to the fitting formula (3). Then, the curing time t and temperature T can be obtained according to the isothermal curing curve α = f(t, T), so that the hot pressing time is about 26.53 min and the hot pressing temperature is about 150 °C. Therefore, according to the target value of the bending strength of the recombinant material product, the dry prepregs can be recombined and formed by the hot pressing process, where the hot pressing time is 26.53 min and the hot pressing temperature is set at 150 °C to prepare the wood recombinant material product.

[0160] The wood recombinant material was prepared and verified by a hot pressing device, with the hot pressing time set at 26.6 min, the hot pressing temperature at 150 °C, and the hot pressing pressure at 18 MPa. The bending strength test was carried out with reference to GB / T 17657-2022. The comparison results between the fitting calculation results and the actual test results are shown in Table 6.

[0161] Table 6 Verification and comparison of the performance indicators of the recombinant materials

[0162]

[0163] As can be seen from Table 6, the detection method of the present invention is accurate and reliable.

[0164] It should be noted that although the technical solutions of the present invention are introduced by specific examples, those skilled in the art can understand that the present invention should not be limited thereto.

[0165] The embodiments of the present invention have been described above. The above description is exemplary and not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations are obvious to those of ordinary skill in the art in the technical field without departing from the scope and spirit of the described embodiments. The choice of terms used herein is intended to best explain the principles of the embodiments, the practical application, or the improvement of the technology in the market, or to enable other ordinary skilled persons in the technical field to understand the embodiments disclosed herein.

Claims

1. A curing prediction method for wood prepreg, characterized in that, It includes the following steps: Measure the degree of cure of the resin material at different curing times under different curing temperatures; Perform a surface fitting on the degree of cure, curing time, and curing temperature of the resin material to establish a functional relationship between the degree of cure, curing time, and curing temperature, and obtain a curing conversion rate surface; Impregnate the wood units with the resin material and then dry to obtain wood prepregs; Based on the curing conversion rate surface, obtain the curing time and curing temperature of the wood prepregs corresponding to different degrees of cure, and perform hot pressing on the wood prepregs based on the curing time and curing temperature to obtain molded articles with different degrees of cure; Measure the physical and mechanical properties of each of the molded articles; Perform a non-linear relationship fitting between the degree of cure and the physical and mechanical properties of the molded articles to establish a functional relationship between the degree of cure and the physical and mechanical properties, and obtain a relationship curve; Provide a wood prepreg to be tested, based on the target value of the physical and mechanical properties of the wood prepreg to be tested, use the relationship curve to obtain the target value of the degree of cure, and based on the curing conversion rate surface, obtain the optimized hot pressing process conditions for the wood prepreg to be tested.

2. The curing prediction method according to claim 1, wherein The curing temperature of the resin material is 110 - 170 °C, and the temperature interval between two adjacent curing temperatures is 1 - 10 °C.

3. The curing prediction method according to claim 1 or 2, wherein The resin material includes one or a combination of two or more of phenolic resin, epoxy resin, polyurethane dendrimer, urea-formaldehyde resin, melamine-formaldehyde resin, and polyimide resin.

4. The curing prediction method according to any one of claims 1-3, characterized in that, Use a dielectric curing detector to test the conductivity of the resin material, and based on the relationship between the conductivity and the degree of cure, obtain the degree of cure of the resin material.

5. The curing prediction method according to claim 4, wherein The relationship between the degree of cure and the conductivity of the resin material is as shown in the following formula (1): Where α represents the degree of cure of the resin; σ min represents the minimum value of the conductivity during the test; σ represents the conductivity of the resin.

6. The curing prediction method according to any one of claims 1-5, characterized in that, Based on the functional relationship between the degree of cure and the curing time of the resin material at different curing temperatures, fit to obtain the functional relationship between the degree of cure, curing time, and curing temperature of the resin material, and obtain the curing conversion rate surface with curing time and curing temperature as variables.

7. The curing prediction method according to any one of claims 1-6, characterized in that The fitting result of the relationship curve includes a 95% confidence band and a 95% prediction band, where the relationship curve is represented by formula (2): X n = g(α) (2) Among them, X n represents the physical and mechanical properties; α represents the degree of cure.

8. The curing prediction method according to any one of claims 1-7, characterized in that, The physical and mechanical properties include flexural modulus of elasticity, static bending strength, water absorption width expansion rate, or water absorption thickness expansion rate.

9. A preparation method of a wood-based recombinant material, characterized in that, Obtain the optimized hot pressing process conditions according to the curing prediction method of the wood prepreg according to any one of claims 1 - 8, and prepare the wood recombined material based on the hot pressing process conditions.

10. A wood-based recombinant material, characterized in that, It is prepared according to the preparation method described in claim 9.

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