Method for preparing thermoplastic fabric prepreg with uniform resin content distribution

Abstract

The present invention belongs to the technical field of composite material preparation, and relates to a method for preparing thermoplastic fabric prepreg with uniform resin content distribution. After the resin powder is dispersed on the flattened fabric surface by a powder spreading machine, the resin powder is melted, cooled and rolled up. The powder spreading machine includes a needle roller, and the weight of the resin powder is ≥100g / m 2 , the particle size of the resin powder is 50-300 μm, and the median diameter is 80-180 μm; the spacing between any two adjacent needles on the surface of the needle roller is equal, and the value range is 3-8 mm, and the distribution of all needles on the surface of the needle roller satisfies: the overall pattern formed by connecting the roots of all two adjacent needles one by one is a diamond grid or a regular hexagonal grid. The present invention avoids the problem that the powder is easy to bounce and move on the fabric surface during the powdering process, while improving the powdering uniformity, and can still maintain good powdering uniformity when preparing prepregs with a large gram weight content.

Description

Technical Field

[0001] The invention belongs to the technical field of composite material preparation, and relates to a method for preparing a thermoplastic fabric prepreg with uniformly distributed resin content. Background Art

[0002] Thermoplastic fabric prepreg is a composite material composed of thermoplastic resin and fiber fabric. It is often used to prepare thermoplastic composite structural parts and carbon fiber reinforced thermoplastic sheets. Thermoplastic composite structural parts play a key role in aerospace, automobile, construction and other fields. Carbon fiber reinforced thermoplastic sheets, with their excellent mechanical properties and high strength characteristics, show unique advantages in lightweight design and enhanced structural strength.

[0003] However, the quality of both thermoplastic composite structural parts and carbon fiber reinforced thermoplastic sheets directly depends on the uniformity of the resin content in the thermoplastic fabric prepreg. If the resin content is unevenly distributed, it will lead to resin-rich areas or even dry spots on the surface of the sheet or structural parts, which will seriously affect its mechanical properties and overall quality.

[0004] Common preparation methods for thermoplastic fabric prepregs include powdering method, fluidized bed method, solution method, film method and laminating method. Among them, powdering method is widely used in industrial production due to its simple equipment structure and high efficiency. Powdering uniformity is crucial to ensure the uniformity of resin content in prepregs.

[0005] Patent application CN106476161A discloses a prepreg preparation device, which adopts a powder spreading method to prepare thermoplastic fabric prepreg, and has the advantages of simple structure and low cost.

[0006] Patent application CN116160588B discloses a low-gram-weight powder spreading device and a spreading control method thereof. The patent uses a sampling frame to simulate the fiber receiving and spreading powder during the production process, observes and measures the state of the sampled powder, adjusts the needle roller rotation speed and the sampling frame movement speed so that the sampling frame receives powder to meet production requirements, determines the needle roller rotation speed and the fiber conveying speed during the production process, and achieves the production requirements of low-gram-weight powder spreading and uniform powder spreading of the spreading device.

[0007] However, the powder spreading uniformity of the above two patents is relatively poor when processing prepreg with a large gram weight (>100g / m²).

[0008] In summary, the powdering methods in the prior art all have certain limitations. Summary of the invention

[0009] The purpose of the present invention is to solve the problems existing in the prior art and provide a method for preparing a thermoplastic fabric prepreg with uniform resin content distribution.

[0010] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0011] A method for preparing thermoplastic fabric prepreg with uniform resin content distribution, wherein the resin powder is dispersed on the flattened fabric surface by a powder spreading machine, and then the resin powder is melted, cooled and rolled up. The powder spreading machine includes a needle roller, and the weight of the resin powder is ≥100g / m 2 The particle size of the resin powder is 50-300μm, and the median diameter (D50, the corresponding particle size when the cumulative distribution accounts for 50% in the system) is 80-180μm. The resin powder can be PA, PP, HDPE, UHMWPE, PPS, PEEK, PAEK, PEI, PES, PSU, PTFE and other powders, or a mixture of two or more blended resin powders with similar melting points, or a resin powder with added inorganic particles (such as nano-magnesium oxide, nano-zirconium oxide, carbon nanotubes, glass fiber powder, carbon fiber powder, graphite powder, etc.); the spacing between any two adjacent needles on the surface of the needle roller is equal, and the value range is 3-8mm. The distribution of all needles on the surface of the needle roller satisfies: the overall pattern formed by connecting the roots of all adjacent two needles one by one is a diamond grid or a regular hexagonal grid. Compared with the regular hexagonal distribution, the diamond distribution is more conducive to saving the number of needles.

[0012] As the preferred technical solution:

[0013] As described above, in a method for preparing a thermoplastic fabric prepreg with a uniformly distributed resin content, the powder spreading machine also includes a hopper and a scraper located directly above the needle roller at the same time. The hopper uses a stirring device or a pressurizing device to unload the resin powder to the needle roller, so as to mix the blended resin powder evenly and also break up the resin powder that is easy to agglomerate. The scraper is arranged at the discharge port of the hopper.

[0014] In the method for preparing a thermoplastic fabric prepreg with uniform resin content distribution as described above, the powder spreading machine also includes an oscillating brush located below the scraper side and obliquely above the needle roller. The oscillating brush oscillates along the axial direction of the needle roller with an oscillation frequency of 2-5 Hz. The needle roller transfers the resin powder during rotation, and the oscillating brush brushes off the resin powder remaining in the needle gap.

[0015] In the method for preparing a thermoplastic fabric prepreg with uniformly distributed resin content as described above, the powder spreading machine also includes a vibrating screen located directly below the needle roller. The vibrating screen swings along the axial direction of the needle roller at the same frequency as the swing brush. The vibrating screen can further evenly disperse the resin powder leaving the needle roller on the fabric surface.

[0016] The method for preparing a thermoplastic fabric prepreg with uniform resin content distribution as described above, wherein the weight of the resin powder is 100-200 g / m 2 .

[0017] As described above, in the method for preparing a thermoplastic fabric prepreg with uniformly distributed resin content, the fabric is pretreated, and the pretreatment process is: heating the fabric while contacting the fabric with ozone, the heating temperature is 380-420°C, and the pretreatment time is 2-5 minutes. The pretreatment can remove the slurry on the surface of the fabric, so that the fabric generates a large number of active oxygen-containing functional groups, which is conducive to better bonding of the fibers in the subsequent fabric with the resin.

[0018] The method for preparing a thermoplastic fabric prepreg with uniform resin content distribution as described above, wherein the pretreatment equipment includes an infrared heating oven and an ozone generator connected to the infrared heating oven, wherein the volume of the infrared heating oven is 2.4-3.2m 3 The oxygen flow rate of the ozone generator is 0.15-0.30m 3 / h.

[0019] According to the method for preparing a thermoplastic fabric prepreg with uniform resin content distribution as described above, melting and cooling the resin powder means that the fabric is sequentially passed through a high temperature section in a melting furnace, a medium temperature section in a melting furnace, a low temperature section in a melting furnace, and a pair of cold rollers outside the melting furnace, the temperature of the high temperature section is 50-60°C higher than the melting point of the resin powder, the temperature of the medium temperature section is 20-40°C higher than the melting point of the resin powder, the temperature of the low temperature section is 5-15°C higher than the melting point of the resin powder, and the temperature of the cold roller is 30-40°C; when the resin powder is a mixture, the melting point of the component with the lowest melting point is taken as the melting point of the mixture, and the difference in the melting points of the components does not exceed 17°C.

[0020] According to the method for preparing a thermoplastic fabric prepreg with uniform resin content distribution, after the resin powder is dispersed on the flattened fabric surface by a powder spreading machine, the CV value of the resin powder mass in different areas of the fabric surface is <3%; the CV value of the resin content in different areas of the thermoplastic fabric prepreg is <3%; and the porosity of the board made of the thermoplastic fabric prepreg is <2%.

[0021] Principle of the invention:

[0022] The powder is blocked by the scraper and falls onto the needle roller. The surface of the needle roller is provided with quantitatively arranged needles. The distance between any two adjacent needles is 3-8mm. Any four adjacent needles form a diamond groove or any six adjacent needles form a regular hexagonal groove structure, which is similar to a "measuring cup". When unloading, the "measuring cup" carries a quantitative amount of powder, and the amount of powder in each "measuring cup" is the same.

[0023] For the preparation of uniform heavy-weight fabric prepreg, in order to ensure that the powder can be evenly dispersed on the fabric surface, on the one hand, it is required that the powder does not become blocked in the needle roller, because once the blockage occurs, it will hinder the subsequent powder from falling, thereby affecting the work of the swing brush, resulting in the powder not being effectively brushed off, and ultimately affecting the uniformity of powder spreading. On the other hand, it is required that the powder can fully fill the "measuring cup" when falling into the needle roller, so that the powder in the "measuring cup" remains stable and does not slide before passing through the swing brush. The present invention achieves these two requirements by adapting the powder particle size to the needle spacing.

[0024] When the powder particle size is too small (less than 50μm), the powder will stick to the wall during the powder spreading process. When the powder falls on the needle roller, the swing brush cannot peel off all the powder because the powder is too fine. The powder remaining in the needle roller will clog the "measuring cup" and hinder the powder falling, resulting in poor uniformity of the powder falling on the fabric. Even if the gap is increased, the powder with a particle size below 50μm will cover the surface of the fabric, and the prepreg will be hard after melting, which is not conducive to winding.

[0025] When the powder particle size is too large (greater than 300μm), the powder falls from the needle roller to the fabric surface by its own weight. Because the fabric is a dense structure woven from tows and has a soft texture, the powder will not move much on the fabric when the particle size is small (50-300μm), but the larger particle size (greater than 300μm) will move more on the fabric, resulting in poor uniformity of the powder falling on the fabric. By measuring the collision recovery coefficient of 50-300μm particle size powder and powder above 300μm with fabric, it can be found that the larger the particle size, the greater the collision recovery coefficient, showing that it is easier to move on the fabric surface. Powders with large particle sizes will bounce on the fabric surface, affecting the uniformity of distribution.

[0026] Particle size μm Collision restitution coefficient μ 50-200 0.256 100-300 0.315 300-400 0.610

[0027] Table 1 Collision recovery coefficient of different particle sizes

[0028] In the particle size range of 50-300μm, D50 of 80-180μm is appropriate. If D50 is too small, the average particle size will be small and there will be many smaller powders below 50μm, causing the powder to be blocked in the needle roller. If D50 is too large, the average particle size will be large, and the powder will bounce and move when it falls on the fabric surface, causing the powder to be unevenly distributed on the fabric.

[0029] When the needle spacing is too small (less than 3mm), the number of needles in the needle roller will increase sharply, the powder capacity will decrease, and the production efficiency will decrease;

[0030] When the distance between the needles is too large (greater than 8 mm), it is impossible to form a "measuring cup" for accommodating 50-300 μm powders, and the powders will slip out of the needle gap prematurely, resulting in uneven powder transfer.

[0031] Beneficial effects:

[0032] (1) The present invention avoids the problem of powder bouncing and moving on the fabric surface during the powder spreading process by reasonably selecting and adapting the particle size of the resin powder and the needle spacing on the needle roller, while improving the powder spreading uniformity. In addition, when preparing prepregs with a large gram weight content, good powder spreading uniformity can still be maintained.

[0033] (2) The present invention ensures that the powder will not be blocked during the powder spreading process, avoids the problem of powder sticking to the wall and residual needle roller blocking the "measuring cup" during the powder spreading process, and can fully fill the "measuring cup" to ensure the uniformity of powder spreading. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a schematic diagram of the distribution of all needles on the surface of the needle roller of the powder spreading machine of Example 1;

[0035] Figure 2 The differential distribution (referring to the proportion of each particle size in the particle size distribution diagram, that is, the ratio of the number of particles at each particle size to the total number of particles) and the cumulative distribution (referring to the ratio of the number of particles less than or equal to a certain particle size in the particle size distribution diagram to the total number of particles) of the particle size of the resin powder of Example 5;

[0036] Figure 3 The differential distribution and cumulative distribution of the particle size of the resin powder of Example 1;

[0037] Figure 4 The differential distribution and cumulative distribution of the particle size of the resin powder of Example 6;

[0038] Figure 5 The differential distribution and cumulative distribution of the particle size of the resin powder of Comparative Example 3;

[0039] Figure 6 The differential distribution and cumulative distribution of the particle size of the resin powder of Comparative Example 4;

[0040] Figure 7 Schematic diagram of the distribution of all needles on the surface of the needle roller of the powder spreading machine of Example 6. DETAILED DESCRIPTION

[0041] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0042] The following are the test methods for the relevant performance indicators in each embodiment and comparative example:

[0043] CV value of resin powder mass in different areas of the fabric surface: Before using the powder spreader to spread powder, place 5 rectangular sampling boxes (pre-weighed) with a size of 70×50×30mm (length×width×height) at a spacing of 10mm on the flattened fabric surface. Start timing when the powder spreader is started. After 30s, stop the powder spreader immediately and take out each rectangular sampling box from the fabric. Then, weigh the mass of resin powder collected in each rectangular sampling box, record the data, calculate the average and standard deviation of the mass of resin powder in all areas, and finally calculate the CV value of the mass of resin powder in different areas of the fabric surface by the following formula:

[0044] CV value of resin powder mass in different areas of fabric surface = (standard deviation / average value) × 100%.

[0045] CV value of resin content in different areas of thermoplastic fabric prepreg: The prepared prepreg is placed on a BK3C1713 cutting table. The cutting table uses a vibrating blade with a cutting speed of 200mm / s. A circle with a diameter of 20mm is cut every 50mm along the width direction of the prepreg. Then, the cut prepreg slices are weighed and the data is recorded to calculate the resin content of each prepreg slice:

[0046] Resin content = (prepreg mass - fiber surface density × 0.000314) / prepreg mass × 100%;

[0047] Finally, the average value and standard deviation of all slices were calculated, and the CV value of the resin content in different regions of the fabric prepreg was calculated by the following formula:

[0048] CV value of resin content in different areas of fabric prepreg = (standard deviation / average value) × 100%.

[0049] Porosity of the plate made of thermoplastic prepreg: The thermoplastic fabric prepreg is first prepared into a plate, and then the porosity of the plate is determined by optical microscopy using GB T 3365-2008 carbon fiber reinforced plastic pore content. The specific steps are as follows: first, three samples with a cross-section length of 20 mm, a width of 10 mm, and a height of 2 mm (sample thickness) are cut from the plate in a direction perpendicular to the fiber axis; then the samples are embedded with epoxy resin embedding material; then, on a grinding machine, the samples are wet-grinded under running water using coarse to fine water-abrasive sandpaper until the surface is relatively flat; then, on a polishing machine, the samples are polished using polishing cloth and polishing paste until the cross-sectional morphology is clearly visible under a microscope without scratches and blurred areas; then, under a microscope, the image is magnified to 200 times, and the photo is processed using ImageJ, and after the absolute area of ​​the pores on the cross section is counted and recorded, the porosity is calculated according to the following formula:

[0050] Porosity = total pore area on the cross section / cross-sectional area × 100%.

[0051] Example 1

[0052] A method for preparing a thermoplastic fabric prepreg with uniform resin content distribution, the specific steps are as follows:

[0053] (1) Preparation of raw materials;

[0054] Fabric: T300 five-satin carbon fiber fabric, surface density 281g / m 2 ;

[0055] Resin: PPS, melting point 280°C;

[0056] (2) After flattening the fabric, use a volume of 3.2m 3 , temperature is 420℃, and oxygen flow rate is 0.2m 3 The flattened fabric is heated for 3 minutes in an infrared heating oven connected to an ozone generator with a flow rate of / h;

[0057] (3) After the resin is crushed by a grinding mill, it is sieved by an ultrasonic sieving machine. First, a 50-mesh screen is used to sieve the powder below the 50-mesh screen, and then a 200-mesh screen is used to sieve the powder above the 200-mesh screen to obtain a resin powder with a particle size of 50-160 μm and a median diameter of 96 μm (the differential distribution and cumulative distribution of the particle size of the resin powder are shown in Figure 3 shown);

[0058] (4) Through a powder spreading machine at 100g / m 2 The resin powder is dispersed on the single side surface of the flattened fabric with a gram weight; wherein the powder spreading machine includes a needle roller, a hopper, a scraper, a swing brush, and a vibrating screen; the diameter of the needle roller is 200mm, and the rotation speed is 4.75r / min; the distance between any two adjacent needles on the surface of the needle roller is 3mm, and the diameter of all needles is 0.5mm; Figure 1 As shown, the distribution of all needles on the surface of the needle roller satisfies: the overall pattern formed by connecting the roots of all adjacent two needles one by one is a diamond grid (the holes of each grid are diamond-shaped and of the same size, and the maximum internal angle of the diamond is 135°); the hopper and the scraper are located directly above the needle roller at the same time; the hopper uses a stirring device or a pressurizing device to unload the resin powder to the needle roller, and the scraper is set at the discharge port of the hopper; the oscillating brush is located below the scraper side and obliquely above the needle roller; the oscillating brush swings along the axial direction of the needle roller, and the swing frequency is 3Hz; the vibrating screen is located directly below the needle roller; the vibrating screen swings along the axial direction of the needle roller, and the swing frequency is the same as the oscillating brush;

[0059] The CV value of the resin powder mass in different areas of the fabric surface is 1.81%;

[0060] (5) The fabric is passed through a high temperature section in a melting furnace, a medium temperature section in a melting furnace, a low temperature section in a melting furnace, and a pair of cold rollers outside the melting furnace in sequence, and is rolled up to obtain a thermoplastic fabric prepreg with a uniform resin content distribution; wherein the temperature of the high temperature section in the melting furnace is 335°C, the temperature of the medium temperature section is 310°C, and the temperature of the low temperature section is 290°C; and the temperature of the pair of cold rollers outside the melting furnace is 35°C.

[0061] The average resin content in the final thermoplastic fabric prepreg is 42.15wt%, and the CV value of the resin content in different regions is 1.07%; the porosity of the board made of the thermoplastic fabric prepreg is 0.56%.

[0062] Comparative Example 1

[0063] A method for preparing a thermoplastic fabric prepreg with uniform resin content distribution is basically the same as that in Example 1, except that: in step (4), the distance between any two adjacent needles on the surface of the needle roller is 9 mm, and the CV value of the resin powder mass in different areas on the fabric surface is 11.72%.

[0064] The average resin content in the final thermoplastic fabric prepreg is 42.31wt%, and the CV value of the resin content in different regions is 6.64%; the porosity of the board made of the thermoplastic fabric prepreg is 3.48%.

[0065] Comparative Example 2

[0066] A method for preparing a thermoplastic fabric prepreg with uniform resin content distribution is basically the same as that in Example 1, except that: in step (4), the distance between any two adjacent needles on the surface of the needle roller is 10 mm, and the CV value of the resin powder mass in different areas on the fabric surface is 13.91%.

[0067] The average resin content in the final thermoplastic fabric prepreg is 39.02wt%, and the CV value of the resin content in different regions is 8.01%; the porosity of the board made of the thermoplastic fabric prepreg is 5.45%.

[0068] Compared with Example 1, the CV values ​​of the resin powder mass in different areas of the fabric surface, the CV values ​​of the resin content in different areas of the thermoplastic fabric prepreg, and the porosity of the board made of the thermoplastic fabric prepreg are significantly increased in Comparative Examples 1 and 2. This is because the distance between any two adjacent needles on the surface of the needle roller of the powder spreading machine in Comparative Examples 1 and 2 is too large to form a "measuring cup" for accommodating powders of 50-300 μm. The powder will slip from the needle gap in advance, resulting in uneven transfer of the powder.

[0069] Comparative Example 3

[0070] A method for preparing a thermoplastic fabric prepreg with uniform resin content distribution is basically the same as that in Example 1, except that: Step (3) is: after the resin is crushed by a grinder, it is sieved by an ultrasonic sieving machine, and the powder below the 150-mesh sieve is taken to obtain a resin powder with a particle size of 10-100 μm and a median diameter of 52 μm (the differential distribution and cumulative distribution of the particle size of the resin powder are as follows Figure 5 As shown); in step (4), the CV value of the resin powder mass in different areas of the fabric surface is 12.51%.

[0071] The average resin content in the final thermoplastic fabric prepreg is 35.71wt%, and the CV value of the resin content in different regions is 7.41%; the porosity of the board made of the thermoplastic fabric prepreg is 6.77%.

[0072] Compared with Example 1, the CV values ​​of the resin powder mass in different areas of the fabric surface, the CV values ​​of the resin content in different areas of the thermoplastic fabric prepreg, and the porosity of the board made of the thermoplastic fabric prepreg in Comparative Example 3 are significantly increased. This is because the particle size of the resin powder screened in Comparative Example 3 is too small, which easily causes the powder to be blocked in the needle roller, resulting in uneven powder spreading.

[0073] Comparative Example 4

[0074] A method for preparing a thermoplastic fabric prepreg with uniform resin content distribution is basically the same as that in Example 1, except that: Step (3) is: after the resin is crushed by a grinder, it is sieved by an ultrasonic sieving machine, and the powder below the 30-mesh sieve is taken to obtain a resin powder with a particle size of 100-450 μm and a median diameter of 250 μm (the differential distribution and cumulative distribution of the particle size of the resin powder are as follows Figure 6 As shown); in step (4), the CV value of the resin powder mass in different areas of the fabric surface is 7.49%.

[0075] The average resin content in the final thermoplastic fabric prepreg is 36.14wt%, and the CV value of the resin content in different regions is 12.14%; the porosity of the board made of the thermoplastic fabric prepreg is 9.88%.

[0076] Compared with Example 1, the CV values ​​of the resin powder mass in different areas of the fabric surface, the CV values ​​of the resin content in different areas of the thermoplastic fabric prepreg, and the porosity of the board made of the thermoplastic fabric prepreg in Comparative Example 4 are significantly increased. This is because the particle size of the resin powder screened in Comparative Example 4 is too large, and it is easy to bounce and move on the fabric surface when sprinkling the powder, affecting the uniformity of the distribution.

[0077] Example 2

[0078] A method for preparing a thermoplastic fabric prepreg with uniform resin content distribution is basically the same as that in Example 1, except that: in step (4), the distance between any two adjacent needles on the surface of the needle roller is 5 mm, and the CV value of the resin powder mass in different areas on the fabric surface is 1.58%.

[0079] The average resin content in the final thermoplastic fabric prepreg is 42.04wt%, and the CV value of the resin content in different regions is 0.91%; the porosity of the board made of the thermoplastic fabric prepreg is 1.12%.

[0080] Example 3

[0081] A method for preparing a thermoplastic fabric prepreg with uniform resin content distribution is basically the same as that in Example 1, except that: in step (4), the distance between any two adjacent needles on the surface of the needle roller is 8 mm, and the CV value of the resin powder mass in different areas on the fabric surface is 2.72%.

[0082] The average resin content in the final thermoplastic fabric prepreg is 41.63wt%, and the CV value of the resin content in different regions is 1.60%; the porosity of the board made of the thermoplastic fabric prepreg is 1.08%.

[0083] When testing the CV values ​​of the resin powder mass in different areas of the fabric surface, the average values ​​of the resin powder mass in the five rectangular sample boxes of each test group (i.e., Examples 1 to 3 and Comparative Examples 1 to 3) are shown in Table 2:

[0084] Table 2

[0085] Group Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Mean (g) 2.4872 2.5387 2.4965 2.5792 2.4489 1.9478

[0086] Example 4

[0087] A method for preparing a thermoplastic fabric prepreg with uniform resin content distribution, the specific steps are as follows:

[0088] (1) Preparation of raw materials;

[0089] Fabric: EC6 satin fiberglass fabric, surface density 296g / m 2 ;

[0090] Resin: PPS, melting point 280°C;

[0091] (2) After the resin is crushed by a grinding mill, it is sieved by an ultrasonic sieving machine. First, a 50-mesh sieve is used to sieve the powder below the 50-mesh sieve, and then a 200-mesh sieve is used to sieve the powder above the 200-mesh sieve to obtain a resin powder with a particle size of 50-160 μm and a median diameter of 96 μm;

[0092] (3) After the fabric is flattened, it is passed through a powder spreading machine at 157g / m2 The resin powder is dispersed on the single side surface of the flattened fabric with a gram weight; wherein the powder spreading machine includes a needle roller, a hopper, a scraper, an oscillating brush, and a vibrating screen; the diameter of the needle roller is 200mm, and the rotation speed is 6.91r / min; the distance between any two adjacent needles on the surface of the needle roller is 5mm, and the diameter of all needles is 0.5mm; the distribution of all needles on the surface of the needle roller satisfies: the overall pattern formed by connecting the roots of all adjacent two needles one by one is a diamond grid (each grid hole is diamond-shaped and has the same size, and the maximum internal angle of the diamond is 135°); the hopper and the scraper are located directly above the needle roller at the same time; the hopper uses a stirring device or a pressure device to unload the resin powder to the needle roller, and the scraper is set at the discharge port of the hopper; the oscillating brush is located below the scraper side and obliquely above the needle roller; the oscillating brush swings along the axial direction of the needle roller, and the swing frequency is 5Hz; the vibrating screen is located directly below the needle roller; the vibrating screen swings along the axial direction of the needle roller, and the swing frequency is the same as the oscillating brush;

[0093] The CV value of the resin powder mass in different areas of the fabric surface is 2.52%;

[0094] (4) The fabric is sequentially passed through a high temperature section in a melting furnace, a medium temperature section in a melting furnace, a low temperature section in a melting furnace, and a counter-pressure cold roller outside the melting furnace, and is rolled up to obtain a thermoplastic fabric prepreg with a uniform resin content distribution; wherein the temperature of the high temperature section in the melting furnace is 340°C, the temperature of the medium temperature section is 320°C, and the temperature of the low temperature section is 295°C; and the temperature of the counter-pressure cold roller outside the melting furnace is 35°C.

[0095] The average resin content in the final thermoplastic fabric prepreg is 33.57wt%, and the CV value of the resin content in different regions is 2.14%; the porosity of the board made of the thermoplastic fabric prepreg is 1.02%.

[0096] Example 5

[0097] A method for preparing a thermoplastic fabric prepreg with uniform resin content distribution, the specific steps are as follows:

[0098] (1) Preparation of raw materials;

[0099] Fabric: Carbon fiber felt, surface density 150g / m 2 ;

[0100] Resin: PP with glass fiber powder added (the content of glass fiber powder in PP is 10wt%), the melting point of PP is 160℃;

[0101] (2) After flattening the fabric, use a volume of 2.4m 3 , temperature is 380℃, and oxygen flow rate is 0.15m 3 The flattened fabric is heated for 2 minutes in an infrared heating oven connected to an ozone generator with a flow rate of / h;

[0102] (3) After the resin is crushed by a grinding mill, it is sieved by an ultrasonic sieving machine. First, a 45-mesh screen is used to sieve the powder below the 45-mesh screen, and then a 150-mesh screen is used to sieve the powder above the 150-mesh screen to obtain a resin powder with a particle size of 100-270 μm and a median diameter of 159 μm (the differential distribution and cumulative distribution of the particle size of the resin powder are shown in Figure 2 shown);

[0103] (4) Through a powder spreading machine at 150g / m 2 The resin powder is dispersed on the single side surface of the flattened fabric with a gram weight; wherein the powder spreading machine includes a needle roller, a hopper, a scraper, an oscillating brush, and a vibrating screen; the diameter of the needle roller is 200mm, and the rotation speed is 9.91r / min; the distance between any two adjacent needles on the surface of the needle roller is 6mm, and the diameter of all needles is 0.5mm; the distribution of all needles on the surface of the needle roller satisfies: the overall pattern formed by connecting the roots of all two adjacent needles one by one is a diamond grid (the holes of each grid are diamond-shaped and have the same size, and the maximum internal angle of the diamond is 135°); the hopper and the scraper are located directly above the needle roller at the same time; the hopper uses a stirring device or a pressure device to unload the resin powder to the needle roller, and the scraper is set at the discharge port of the hopper; the oscillating brush is located below the scraper side and obliquely above the needle roller; the oscillating brush swings along the axial direction of the needle roller, and the swing frequency is 4.5Hz; the vibrating screen is located directly below the needle roller; the vibrating screen swings along the axial direction of the needle roller, and the swing frequency is the same as the oscillating brush;

[0104] The CV value of the resin powder mass in different areas of the fabric surface is 2.65%;

[0105] (5) The fabric is sequentially passed through a high temperature section in a melting furnace, a medium temperature section in a melting furnace, a low temperature section in a melting furnace, and a counter-pressure cold roller outside the melting furnace, and is wound up to obtain a thermoplastic fabric prepreg with a uniform resin content distribution; wherein the temperature of the high temperature section in the melting furnace is 215°C, the temperature of the medium temperature section is 185°C, and the temperature of the low temperature section is 165°C; and the temperature of the counter-pressure cold roller outside the melting furnace is 30°C.

[0106] The average resin content in the final thermoplastic fabric prepreg is 50.66wt%, and the CV value of the resin content in different regions is 2.01%; the porosity of the board made of the thermoplastic fabric prepreg is 1.37%.

[0107] Example 6

[0108] A method for preparing a thermoplastic fabric prepreg with uniform resin content distribution, the specific steps are as follows:

[0109] (1) Preparation of raw materials;

[0110] Fabric: T300 plain weave carbon fiber fabric, surface density 281g / m 2 ;

[0111] Resin: PEI and PEEK blended resin, the mass ratio of PEI and PEEK in the blended resin is 1:1, the melting point of PEI is 360°C, and the melting point of PEEK is 343°C;

[0112] (2) After the fabric is flattened, use a volume of 2.8m 3 , temperature is 400℃, and oxygen flow rate is 0.3m 3 The flattened fabric is heated for 5 minutes in an infrared heating oven connected to an ozone generator with a flow rate of / h;

[0113] (3) After the resin is crushed by a grinding mill, it is sieved by an ultrasonic sieving machine. First, a 50-mesh screen is used to sieve the powder below the 50-mesh screen, and then a 200-mesh screen is used to sieve the powder above the 200-mesh screen to obtain a resin powder with a particle size of 50-180 μm and a median diameter of 83 μm (the differential distribution and cumulative distribution of the particle size of the resin powder are shown in Figure 4 shown);

[0114] (4) Through a powder spreading machine at 200g / m 2 The resin powder is dispersed on the single side surface of the flattened fabric with a gram weight; wherein the powder spreading machine includes a needle roller, a hopper, a scraper, a swing brush, and a vibrating screen; the diameter of the needle roller is 200mm, and the rotation speed is 8.85r / min; the distance between any two adjacent needles on the surface of the needle roller is 8mm, and the diameter of all needles is 0.5mm; Figure 7 As shown, the distribution of all needles on the surface of the needle roller satisfies: the overall pattern formed by connecting the roots of all two adjacent needles one by one is a regular hexagonal grid; the hopper and the scraper are located directly above the needle roller at the same time; the hopper uses a stirring device or a pressurizing device to unload the resin powder to the needle roller, and the scraper is set at the discharge port of the hopper; the oscillating brush is located below the scraper side and obliquely above the needle roller; the oscillating brush swings along the axial direction of the needle roller, and the swing frequency is 5Hz; the vibrating screen is located directly below the needle roller; the vibrating screen swings along the axial direction of the needle roller, and the swing frequency is the same as the oscillating brush;

[0115] The CV value of the resin powder mass in different areas of the fabric surface is 1.19%;

[0116] (5) The fabric is passed through a high temperature section in a melting furnace, a medium temperature section in a melting furnace, a low temperature section in a melting furnace, and a counter-pressure cold roller outside the melting furnace in sequence, and is rolled up to obtain a thermoplastic fabric prepreg with a uniform resin content distribution; wherein the temperature of the high temperature section in the melting furnace is 395°C, the temperature of the medium temperature section is 365°C, and the temperature of the low temperature section is 350°C; and the temperature of the counter-pressure cold roller outside the melting furnace is 40°C.

[0117] The average resin content in the final thermoplastic fabric prepreg is 50.66wt%, and the CV value of the resin content in different regions is 1.28%; the porosity of the board made of the thermoplastic fabric prepreg is 1.33%.

Claims

1. A method for preparing thermoplastic fabric prepreg with uniform resin content distribution, wherein the resin powder is dispersed on the flattened fabric surface by a powder spreading machine, and the resin powder is melted and cooled in sequence, and then rolled up. The powder spreading machine includes a needle roller, and the weight of the resin powder is ≥100g / m 2 , characterized in that, The particle size of the resin powder is 50-300μm, and the median diameter is 80-180μm; the spacing between any two adjacent needles on the surface of the needle roller is equal, ranging from 3-8mm, and the distribution of all needles on the surface of the needle roller satisfies: the overall pattern formed by connecting the roots of all adjacent two needles one by one is a diamond grid or a regular hexagonal grid.

2. The method for preparing a thermoplastic fabric prepreg with uniform resin content distribution according to claim 1, characterized in that: The powder spreading machine also includes a hopper and a scraper which are located directly above the needle roller. The hopper uses a stirring device or a pressurizing device to discharge the resin powder to the needle roller, and the scraper is arranged at the discharge port of the hopper.

3. The method for preparing a thermoplastic fabric prepreg with uniform resin content distribution according to claim 2, characterized in that: The powder spreading machine also includes an oscillating brush located below the scraper side and obliquely above the needle roller. The oscillating brush oscillates along the axial direction of the needle roller at an oscillation frequency of 2-5 Hz.

4. The method for preparing a thermoplastic fabric prepreg with uniform resin content distribution according to claim 3, characterized in that: The powder spreading machine also comprises a vibrating screen located just below the needle roller, and the vibrating screen swings along the axial direction of the needle roller, and the swing frequency is the same as that of the swing brush.

5. The method for preparing a thermoplastic fabric prepreg with uniform resin content distribution according to claim 1, characterized in that: The weight of the resin powder is 100-200g / m 2 .

6. The method for preparing a thermoplastic fabric prepreg with uniform resin content distribution according to claim 1, characterized in that: The fabric is pretreated, and the pretreatment process is: the fabric is contacted with ozone while being heated, the heating temperature is 380-420° C., and the pretreatment time is 2-5 minutes.

7. The method for preparing a thermoplastic fabric prepreg with uniform resin content distribution according to claim 6, characterized in that: The equipment used for pretreatment includes an infrared heating oven and an ozone generator connected to the infrared heating oven. The volume of the infrared heating oven is 2.4-3.2m 3 The oxygen flow rate of the ozone generator is 0.15-0.30m 3 / h.

8. The method for preparing a thermoplastic fabric prepreg with uniform resin content distribution according to claim 1, characterized in that: Melting and cooling the resin powder in sequence means that the fabric passes through the high temperature section in the melting furnace, the medium temperature section in the melting furnace, the low temperature section in the melting furnace, and the cold roller outside the melting furnace in sequence, the temperature of the high temperature section is 50-60°C higher than the melting point of the resin powder, the temperature of the medium temperature section is 20-40°C higher than the melting point of the resin powder, the temperature of the low temperature section is 5-15°C higher than the melting point of the resin powder, and the temperature of the cold roller is 30-40°C; when the resin powder is a mixture, the melting point of the component with the lowest melting point is taken as the melting point of the mixture, and the difference in melting points of the components does not exceed 17°C.

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