A preparation process of pultruded flat plate with high fiber content

Abstract

The present invention relates to the field of composite pultruded sheet preparation, and specifically to a preparation process for a pultruded flat sheet with a high fiber content. The technical points are as follows: the fiber volume content of the high fiber content pultruded flat sheet is ≥72%; the preparation process includes: threading, fiber heating treatment, dipping, preforming, precuring, curing, post-curing, traction and cutting; wherein the fiber heating pretreatment adopts infrared preheating treatment to make the fiber temperature between 35 and 45°C. According to the preparation method of this patent, compared with the traditional preparation process, the porosity and impregnation defect problems of the composite sheet are greatly reduced, the interface bonding ability between the fiber and the sheet is improved, and the internal stress accumulation caused by the rapid curing of the pultruded resin is reduced. At the same time, it ensures that the internal stress generated is effectively released in the post-curing stage, thereby reducing the fatigue performance degradation caused by stress concentration.

Description

Technical Field

[0001] The invention relates to the field of composite pultruded plate preparation, and in particular to a preparation process of a pultruded plate with high fiber content. Background Art

[0002] In the composite pultruded flat panel industry, the fiber volume content of the panels currently used in batches is less than 72%, mainly because when the fiber volume content exceeds 72%, the fatigue strength of the composite pultruded panel drops sharply (the residual fatigue strength after one million cycles is far less than 300MPa) and fluctuates abnormally, and its strain and strength show a nonlinear relationship. As the price of wind turbine blades continues to decrease, the demand for unit performance cost of materials is increasing, and the performance requirements of panels are rising sharply. At present, the market mostly uses increasing the volume content of reinforcing fibers to achieve an increase in the modulus of the panel, but due to the fatigue performance of the panel, the fiber content has been kept below 72% and cannot be further increased. Summary of the invention

[0003] The purpose of the present invention is to develop a preparation process for a pultruded flat plate with a high fiber content. By means of fiber pretreatment, preheating treatment and control of plate defects, the porosity and defects of the composite plate can be reduced, the interface bonding performance between the fiber and the resin can be improved, the fatigue strength performance of the reinforced fiber can be greatly improved, and the residual fatigue strength of the composite plate with a fiber content of more than 72% can be increased to more than 300 MPa after one million cycles.

[0004] The above technical objectives of the present invention are achieved through the following technical solutions:

[0005] The present invention provides a preparation process of a high-fiber-content pultruded flat plate, wherein the fiber volume content of the high-fiber-content pultruded flat plate is ≥72%; the preparation process comprises: threading, fiber heating treatment, dipping, preforming, precuring, curing, post-curing, pulling and cutting;

[0006] The fiber heating pretreatment adopts infrared preheating treatment to make the temperature of the fiber be between 35 and 45°C.

[0007] When the fiber volume content is increased to more than 72%, the amount of resin used is reduced, which greatly reduces the interfacial bonding performance between the fiber and the resin, resulting in a sharp decrease in the fatigue strength of the board. In the present invention, the fiber is pretreated by infrared heating to increase the proportion of activated molecules in the impregnant and increase the Gibbs free energy of the substrate molecules in the impregnant. On the one hand, the bonding force between the impregnant and the fiber is improved, and the wettability of the fiber is improved. On the other hand, the activity of the impregnant is improved, which is beneficial to the improvement of the interfacial performance between the fiber and the resin, thereby solving the problem of decreased fatigue strength of the board caused by excessive fiber content.

[0008] At the same time, in the preparation process provided by the present invention, the fibers are uniformly distributed in the board by threading to improve the overall strength and toughness. Reasonable fiber arrangement is crucial to the performance of the material. The fiber heating pretreatment adopts infrared preheating treatment, which increases the fiber temperature to 35-45°C to increase the fiber surface activity, which helps to increase the interaction between the sizing agent and the fiber, thereby improving the wettability. The use of a water-soluble emulsion with a solid content of 5-10% ensures the uniform distribution of the sizing agent between the fibers. The selection of the emulsion takes into account its environmental friendliness and easy operation characteristics.

[0009] Preforming is carried out at a temperature of 60-90°C to give the material the desired shape at the beginning of its formation. This helps with subsequent processes and ensures that the product's geometry meets the requirements. Pre-curing, curing and post-curing are then used. Temperature control helps control the curing speed of the resin at different stages, ultimately obtaining a sheet with excellent performance.

[0010] Furthermore, in the infrared heating pretreatment, the infrared wavelength is 6 to 20 μm, and the treatment time is 30 to 120 seconds. In the technical solution provided by the present invention, the infrared radiation has energy that matches the molecular vibration frequency. When the fiber is subjected to infrared radiation, the molecules begin to vibrate, which causes the bonds inside the wetting agent molecules to break and rearrange, which helps to increase the activity of the wetting agent molecules. At the same time, infrared heating can quickly increase the temperature of the fiber, causing the molecules to become active at higher temperatures. This thermal effect may lead to enhanced interactions between wetting agent molecules, which is beneficial to improving the wettability and permeability of the wetting agent. In addition, infrared radiation heating can cause the surface activity of the wetting agent molecules to increase, thereby changing the Gibbs free energy of the wetting agent, which helps to increase the mutual attraction between the wetting agent molecules and the fibers, and enhance the adsorption and penetration of the wetting agent into the fibers.

[0011] In addition, infrared radiation heating increases the number of active groups in the sizing agent molecules. These active groups can more easily react chemically with the fiber surface to form stronger chemical bonds, thereby improving the bonding force between the sizing agent and the fiber.

[0012] However, if the infrared wavelength is too long, the radiation energy will be insufficient and cannot be effectively absorbed by the material, which will reduce the temperature rise rate of the fiber and fail to achieve the expected fiber pretreatment effect. It will also weaken the effect of improving the activity of the wetting agent molecules and fail to stimulate certain required chemical reactions in the material, affecting the activity improvement of the wetting agent molecules.

[0013] If the infrared wavelength is too short, the material will absorb excessive energy and cause heat loss, which may lead to local overheating rather than uniform heating. In addition, excessive absorption may also cause thermal damage to the fiber, reducing its performance, and a wavelength that is too short may lead to inappropriate molecular vibration modes, unable to effectively promote the activity of the sizing agent molecules and interface adsorption, affecting the interaction between the sizing agent and the fiber.

[0014] Furthermore, the preforming temperature is 60-90°C.

[0015] Furthermore, the pre-curing temperature is 140-170° C. In the present invention, the fiber impregnated with resin is first passed through a pre-curing device before entering the mold for curing and molding. The viscosity of the resin is reduced in this stage, which promotes impregnation and is more conducive to the discharge of bubbles after volume thermal expansion. At the same time, the resin passes through the pre-curing stage, which reduces the reaction stress concentration of the composite material and is conducive to improving fatigue performance.

[0016] Furthermore, the curing temperature is 170-195°C.

[0017] Furthermore, the post-curing temperature is 180-190°C.

[0018] Furthermore, the pulling speed is 0.5-1 m / min.

[0019] Furthermore, the wetting agent used in the dipping of the present invention is a water-soluble emulsion with a solid content of 5 to 10%.

[0020] Furthermore, the wetting agent includes: a binder, a coupling agent, an antistatic agent, a lubricant, a humectant and a conditioning agent.

[0021] Furthermore, calculated by weight, the wetting agent includes: 40-50 parts of a binder, 0.2-0.5 parts of an antistatic agent, 0.5-1 parts of a lubricant, 0.2-0.5 parts of a moisturizer, 2.5-4 parts of an auxiliary agent, and 50-80 parts of deionized water.

[0022] Furthermore, in the infrared heating pretreatment, the infrared wavelength is 6 to 20 μm, and the specific selection method is as follows:

[0023] When the ratio A of the binder to water in the wetting agent is 0.5≤A<0.67, and the preforming temperature T is 60℃≤T<75℃, the infrared wavelength W is selected as 15μm≤W≤20μm; when the ratio A of the binder to water in the wetting agent is 0.5≤A<0.67, and the preforming temperature T is 75℃≤T≤90℃, the infrared wavelength W is selected as 10μm≤W<15μm; when the ratio A of the binder to water in the wetting agent is 0.67≤A≤1, and the preforming temperature T is 60℃≤T<75℃, the infrared wavelength W is selected as 10μm≤W<15μm; when the ratio A of the binder to water in the wetting agent is 0.67≤A≤1, and the preforming temperature T is 75℃≤T≤90℃, the infrared wavelength W is selected as 6μm≤W<10μm.

[0024] The present invention comprehensively considers the ratio of binder to water in the impregnant and the change of preheating temperature. When the ratio of binder to water is large or the preheating temperature is high, selecting a higher energy infrared wavelength (for example, 15μm≤W≤20μm or 10μm≤W<15μm) helps to meet higher energy requirements and ensure sufficient heating effect. At the same time, for the case of a large ratio or a high preheating temperature, selecting a higher energy infrared wavelength helps to avoid overheating and possible thermal damage. By accurately matching the energy with the absorption characteristics of the material, unnecessary thermal damage to the material can be minimized, ensuring the accuracy and quality of the processing. In addition, selecting a higher energy infrared wavelength when the ratio is large or the temperature is high helps to improve the heating efficiency and ensure that the energy penetrates deeper into the material, thereby improving the penetration depth and uniformity.

[0025] Furthermore, the binder is 3,4-epoxy-6-methylcyclohexanecarboxylic acid-3,4-epoxy-6-methylcyclohexane methyl ester epoxy.

[0026] Furthermore, the antistatic agent is amide phosphate.

[0027] Furthermore, the lubricant is a block copolymer of ethylene oxide and propylene oxide.

[0028] Furthermore, the moisturizing agent is hexylene glycol.

[0029] Furthermore, the auxiliary agent is isopropanol.

[0030] In summary, the present invention has the following beneficial effects:

[0031] (1) The preparation method of the present invention can establish a stronger interaction force between the sizing agent and the fiber through the steps of infrared preheating treatment, which helps to reduce the porosity and impregnation defects of the composite board and improve the density and uniformity of the board.

[0032] (2) The present invention optimizes the active molecule ratio of the sizing agent by infrared preheating treatment, and improves the bonding force between the sizing agent and the fiber. This further enhances the interfacial bonding ability between the fiber and the board, and helps to ensure that the material has better stability and reliability during use.

[0033] (3) The present invention adopts preforming, precuring and other steps to effectively control the curing process of the resin. The low temperature operation in the precuring stage helps to reduce the internal stress accumulation caused by the rapid curing of the pultruded resin. This helps to slow down the curing rate, reduce internal stress, and improve the stability of the board.

[0034] (4) The present invention ensures that the internal stress can be effectively released during the entire production process by setting the post-curing stage. This measure helps to reduce stress concentration and improve the fatigue performance of the material, thereby slowing down the degradation of fatigue performance caused by stress concentration.

[0035] (5) The present invention reduces the risk of stress concentration by finely controlling the plate preparation process, which helps to ensure that the plate can better resist external impact, vibration and other stresses during use, thereby avoiding performance degradation caused by stress concentration. DETAILED DESCRIPTION

[0036] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, a preparation process of a high-fiber content pultruded flat plate proposed by the present invention, its specific implementation method, characteristics and effects are described in detail as follows.

[0037] The present specific embodiment provides a preparation process of a high-fiber content pultruded flat plate, wherein the fiber volume content of the high-fiber content pultruded flat plate is ≥72%; the preparation process includes: threading, fiber heating treatment, resin dipping, preforming, precuring, curing, post-curing, traction and cutting; wherein the fiber heating pretreatment adopts infrared preheating treatment to make the temperature of the fiber at 35-45°C. When the fiber volume content is increased to more than 72%, the interface bonding performance between the fiber and the resin is greatly reduced due to the reduction in the amount of resin, resulting in a sharp decrease in the fatigue strength of the plate; in the present invention, by performing infrared heating pretreatment on the fiber, the proportion of activated molecules of the sizing agent is increased, and the Gibbs free energy of the substrate molecules in the sizing agent is increased, which, on the one hand, improves the binding force between the sizing agent and the fiber and improves the wettability of the fiber, and on the other hand, improves the activity of the sizing agent, which is beneficial to the improvement of the interface performance between the fiber and the resin, thereby solving the problem of decreased fatigue strength of the plate caused by excessive fiber content.

[0038] Among them, in the infrared heating pretreatment, the infrared wavelength is 6-20μm, the processing time is 30-120s; the preforming temperature is 60-90℃; the precuring temperature is 140-170℃; the curing temperature is 170-195℃; the post-curing temperature is 180-190℃; the pulling speed is 0.5-1m / min.

[0039] Among them, the wetting agent used for dipping is a water-soluble emulsion with a solid content of 5-10%, calculated by weight, specifically including: 40-50 parts of adhesive, 0.2-0.5 parts of antistatic agent, 0.5-1 parts of lubricant, 0.2-0.5 parts of moisturizer, 2.5-4 parts of auxiliary agent and 50-80 parts of deionized water.

[0040] In some preferred embodiments, the specific method for selecting the infrared wavelength is as follows:

[0041] When the ratio A of the binder to water in the wetting agent is 0.5≤A<0.67, and the preforming temperature T is 60℃≤T<75℃, the infrared wavelength W is selected as 15μm≤W≤20μm; when the ratio A of the binder to water in the wetting agent is 0.5≤A<0.67, and the preforming temperature T is 75℃≤T≤90℃, the infrared wavelength W is selected as 10μm≤W<15μm; when the ratio A of the binder to water in the wetting agent is 0.67≤A≤1, and the preforming temperature T is 60℃≤T<75℃, the infrared wavelength W is selected as 10μm≤W<15μm; when the ratio A of the binder to water in the wetting agent is 0.67≤A≤1, and the preforming temperature T is 75℃≤T≤90℃, the infrared wavelength W is selected as 6μm≤W<10μm.

[0042] Example 1: A process for preparing a high fiber content pultruded flat plate

[0043] In this embodiment, the fiber volume content of the high fiber content pultruded flat plate used is 72.5%; the preparation process includes: yarn threading, fiber heating treatment, dipping, preforming, precuring, curing, post-curing, traction and cutting; wherein the fiber heating pretreatment adopts infrared preheating treatment to make the fiber temperature at 40°C.

[0044] Among them, in the infrared heating pretreatment, the treatment time is 100s; the preforming temperature is 78°C; the precuring temperature is 160°C; the curing temperature is 185°C; the post-curing temperature is 185°C; and the pulling speed is 1m / min.

[0045] Among them, calculated by weight, the wetting agent used for dipping includes the following components: 50 parts of 3,4-epoxy-6-methylcyclohexanecarboxylic acid-3,4-epoxy-6-methylcyclohexane methyl ester epoxy, 0.5 parts of amide phosphate, 1 part of ethylene oxide and propylene oxide block copolymer, 0.5 parts of hexanediol, 4 parts of isopropanol, and 80 parts of deionized water.

[0046] The ratio of binder to water is A=0.625, and the preforming temperature T is 78°C. In the infrared heating pretreatment, the infrared wavelength has a value range of 10μm≤W<15μm. In this embodiment, the infrared wavelength is 12μm.

[0047] Example 2: A process for preparing a high fiber content pultruded flat plate

[0048] In this embodiment, the fiber volume content of the high fiber content pultruded flat plate used is 72.5%; the preparation process includes: yarn threading, fiber heating treatment, dipping, preforming, precuring, curing, post-curing, traction and cutting; wherein the fiber heating pretreatment adopts infrared preheating treatment to make the fiber temperature at 40°C.

[0049] Among them, in the infrared heating pretreatment, the treatment time is 110s; the preforming temperature is 65°C; the precuring temperature is 160°C; the curing temperature is 180°C; the post-curing temperature is 180°C; and the pulling speed is 0.5 / min.

[0050] Among them, calculated by weight, the wetting agent used for dipping includes the following components: 40 parts of 3,4-epoxy-6-methylcyclohexanecarboxylic acid-3,4-epoxy-6-methylcyclohexane methyl ester, 0.4 parts of amide phosphate, 1 part of ethylene oxide and propylene oxide block copolymer, 0.2 parts of hexanediol, 2.5 parts of isopropanol, and 80 parts of deionized water.

[0051] The ratio of binder to water is A=0.5, and the preforming temperature T is 65° C. Then, in the infrared heating pretreatment, the infrared wavelength has a value range of 15 μm≤W≤20 μm. In this embodiment, the infrared wavelength is 18 μm.

[0052] Comparative Example 1: Preparation process of a high fiber content pultruded flat plate

[0053] In this embodiment, the fiber volume content of the high-fiber-content pultruded flat plate used is 72.5%; the preparation process includes: threading, dipping, preforming, precuring, curing, post-curing, pulling and cutting.

[0054] Among them, the preforming temperature is 78°C; the precuring temperature is 160°C; the curing temperature is 185°C; the post-curing temperature is 185°C; and the pulling speed is 1m / min.

[0055] Among them, calculated by weight, the wetting agent used for dipping includes the following components: 50 parts of 3,4-epoxy-6-methylcyclohexanecarboxylic acid-3,4-epoxy-6-methylcyclohexane methyl ester epoxy, 0.5 parts of amide phosphate, 1 part of ethylene oxide and propylene oxide block copolymer, 0.5 parts of hexanediol, 4 parts of isopropanol, and 80 parts of deionized water.

[0056] Comparative Example 2: Preparation process of a high fiber content pultruded flat plate

[0057] In this embodiment, the fiber volume content of the high fiber content pultruded flat plate used is 72.5%; the preparation process includes: yarn threading, fiber heating treatment, dipping, preforming, precuring, curing, post-curing, traction and cutting; wherein the fiber heating pretreatment adopts infrared preheating treatment to make the fiber temperature at 40°C.

[0058] Among them, in the infrared heating pretreatment, the treatment time is 100s; the preforming temperature is 78°C; the precuring temperature is 160°C; the curing temperature is 185°C; the post-curing temperature is 185°C; and the pulling speed is 1m / min.

[0059] Among them, calculated by weight, the wetting agent used for dipping includes the following components: 50 parts of 3,4-epoxy-6-methylcyclohexanecarboxylic acid-3,4-epoxy-6-methylcyclohexane methyl ester epoxy, 0.5 parts of amide phosphate, 1 part of ethylene oxide and propylene oxide block copolymer, 0.5 parts of hexanediol, 4 parts of isopropanol, and 80 parts of deionized water.

[0060] The ratio of binder to water is A=0.625, and the preforming temperature T is 78° C. In the infrared heating pretreatment, the infrared wavelength is selected as 8 μm in this embodiment.

[0061] Comparative Example 3: Preparation process of a high fiber content pultruded flat plate

[0062] In this embodiment, the fiber volume content of the high fiber content pultruded flat plate used is 72.5%; the preparation process includes: yarn threading, fiber heating treatment, dipping, preforming, precuring, curing, post-curing, traction and cutting; wherein the fiber heating pretreatment adopts infrared preheating treatment to make the fiber temperature at 40°C.

[0063] Among them, in the infrared heating pretreatment, the treatment time is 100s; the preforming temperature is 78°C; the precuring temperature is 160°C; the curing temperature is 185°C; the post-curing temperature is 185°C; and the pulling speed is 1m / min.

[0064] Among them, calculated by weight, the wetting agent used for dipping includes the following components: 50 parts of 3,4-epoxy-6-methylcyclohexanecarboxylic acid-3,4-epoxy-6-methylcyclohexane methyl ester epoxy, 0.5 parts of amide phosphate, 1 part of ethylene oxide and propylene oxide block copolymer, 0.5 parts of hexanediol, 4 parts of isopropanol, and 80 parts of deionized water.

[0065] The ratio of binder to water is A=0.625, and the preforming temperature T is 78° C. In the infrared heating pretreatment, the infrared wavelength of 18 μm is selected in this embodiment.

[0066] Performance Test Results

[0067] The fatigue strength of the composite plates provided in Examples 1 to 2 and Comparative Example was tested using the following test method: Determination of fatigue properties of fiber reinforced plastics under cyclic loading conditions according to ISO 13003. The test results are shown in the table below.

[0068] Table 1. Performance test results

[0069]

[0070] From the above test results, it can be clearly seen that after adopting the infrared pretreatment method provided by the present invention, the fatigue strength of the composite plate is significantly improved. Specifically:

[0071] After adopting the infrared pretreatment method provided by the present invention, the fatigue strength of the composite plate after one million cycles is greatly improved.

[0072] In particular, in the preparation of high-fiber-content pultruded flat plates with a fiber content of up to or exceeding 72%, a tensile fatigue strength of one million times (R=0.1) was achieved, which proves the improvement effect of the preparation process of the present invention on the performance of high-content fiber materials and provides an effective way to prepare high-performance engineering materials.

[0073] From the comparison between Example 1 and Comparative Examples 2 to 3, it can be seen that when the infrared wavelength is too large, the infrared pretreatment is insufficient and the technical effect of improving fatigue resistance cannot be achieved. When the infrared wavelength is too small, overheating occurs, which in turn leads to a decrease in fatigue resistance.

[0074] In the present invention, improving the molecular activity of the wetting agent is a major goal of infrared pretreatment, and the significant improvement in the test results shows that infrared pretreatment has achieved obvious results in enhancing the interaction between the wetting agent and the fiber and improving the interface bonding performance, which helps to solve the problem of decreased fatigue performance of the plate caused by high fiber content. The infrared pretreatment method not only achieves advantages in the interface performance of the material, but also performs well in the control of internal stress. By reducing the accumulation of internal stress caused by rapid curing and effectively releasing the internal stress in the post-curing stage, the negative impact of stress concentration on material properties is effectively reduced.

[0075] The above description is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been presented as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with the profession can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A process for preparing a high fiber content pultruded flat plate, characterized in that: The fiber volume content of the high-fiber content pultruded flat plate is ≥72%; the preparation process includes: threading, fiber heating treatment, dipping, preforming, precuring, curing, post-curing, pulling and cutting; The fiber heating pretreatment adopts infrared preheating treatment to make the fiber temperature at 35-45°C; In the infrared heating pretreatment, the infrared wavelength is selected as follows: When the ratio A of the binder to water in the sizing agent is 0.5≤A<0.67, and the preforming temperature T is 60℃≤T<75℃, the infrared wavelength W is selected to be 15μm≤W≤20μm; When the ratio A of the binder to water in the sizing agent is 0.5≤A<0.67, and the preforming temperature T is 75℃≤T≤90℃, the infrared wavelength W is selected to be 10μm≤W<15μm; When the ratio A of the binder to water in the sizing agent is 0.67≤A≤1, and the preforming temperature T is 60℃≤T<75℃, the infrared wavelength W is selected to be 10μm≤W<15μm; When the ratio A of the binder to water in the sizing agent is 0.67≤A≤1, and the preforming temperature T is 75℃≤T≤90℃, the infrared wavelength W is selected to be 6μm≤W<10μm; The dipping agent used is a water-soluble emulsion with a solid content of 5-10%; Calculated by weight, the wetting agent includes: 40-50 parts of a binder, 0.2-0.5 parts of an antistatic agent, 0.5-1 parts of a lubricant, 0.2-0.5 parts of a moisturizer, 2.5-4 parts of an auxiliary agent, and 50-80 parts of deionized water.

2. The process for preparing a high fiber content pultruded flat plate according to claim 1, characterized in that: In the infrared heating pretreatment, the infrared wavelength is 6-20 μm and the treatment time is 30-120 s.

3. The process for preparing a high fiber content pultruded flat plate according to claim 1, characterized in that: The preforming temperature is 60-90°C.

4. The process for preparing a high fiber content pultruded flat plate according to claim 1, characterized in that: The pre-curing temperature is 140-170°C.

5. The process for preparing a high fiber content pultruded flat plate according to claim 1, characterized in that: The curing temperature is 170-195°C.

6. The process for preparing a high fiber content pultruded flat plate according to claim 1, characterized in that: The post-curing temperature is 180-190°C.

7. The process for preparing a high fiber content pultruded flat plate according to claim 1, characterized in that: The traction speed is 0.5-1 m / min.

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