A polyurethane foamed composite and a method for producing the same

Abstract

The application belongs to the technical field of polyurethane foam materials, and specifically discloses a polyurethane foaming composite, which comprises polyurethane foam and a plurality of PMI foam blocks, and the plurality of PMI foam blocks are filled and fixed inside the polyurethane foam; and a preparation method of the polyurethane foaming composite is also disclosed, which comprises the following steps: cutting a PMI foam plate, and cutting the PMI foam plate into a plurality of PMI foam blocks; processing a pouring and sealing top cover of a pouring and sealing box to be sealed; loading the PMI foam blocks; pouring polyurethane raw material liquid, pouring the polyurethane foaming material into the pouring and sealing box through a pouring and sealing opening on the pouring and sealing top cover and filling the inner cavity of the pouring and sealing box, so that the polyurethane foaming material is bonded with the PMI foam blocks in the pouring and sealing box to form a mixed product whole; and solidifying, heating the whole pouring and sealing box after pouring and sealing in step four. The application can improve the limitation of polyurethane foam, and form a pouring and sealing foaming composite with good size stability, high compressive strength, heat resistance and light weight.

Description

Technical Field

[0001] This invention relates to the field of polyurethane foam materials technology, specifically to a polyurethane foam composite and its preparation method. Background Technology

[0002] In modern military equipment, various radar antennas typically consist of functional components such as a cavity / base plate, radome, and internal radiators. Within the enclosed cavity formed by the cavity / base plate and radome, the interior is often filled with potting material to create a unified whole. This integrated component is earthquake-resistant, moisture-resistant, and has enhanced overall strength. Due to its light weight and excellent overall performance, polyurethane foam is frequently used as a potting material in antennas.

[0003] Polyurethane foam is often used as a potting or filling material for radar antennas because of its simple molding method and rapid foaming. However, the lower its density, the worse its dimensional stability, the lower its compressive strength, and the poor its high temperature resistance. It usually deforms and bulges at temperatures above 120°C.

[0004] In response to the above situation, various methods have emerged in the industry to improve the strength and stability of polyurethane foam. The most common methods are micro-modification, such as filling with nanoparticle fillers and polymer modification, as well as macro-reinforcement, such as laying glass fiber or steel / aluminum mesh. However, the above methods are all complex to operate, have high development costs, and significantly increase weight. They are not convenient to use for military equipment that needs to reduce weight or has strict weight requirements.

[0005] PMI foam (polymethacrylamide) is currently a top-tier material with superior overall performance and widest process adaptability. It is produced by free polymerization of methacrylic acid and methacrylonitrile to obtain copolymer sheets. At a foaming temperature of 180-230℃, the foaming agent pre-embedded in the copolymer is vaporized to produce PMI foam sheets. During foaming, the cyano and carboxyl groups in the copolymer undergo nucleophilic addition reactions to form a cyclic imide structure. The strong polarity and high stiffness of this structure endow PMI foam with excellent overall performance. Compared to polyurethane foam, PMI foam has more uniform cell structure, higher closed-cell ratio, and isotropic mechanical properties. It possesses high specific strength and specific modulus, strong chemical stability, high temperature resistance, and excellent processability, allowing it to be machined into any shape. It also exhibits good thermal insulation, shock absorption, and impact resistance. Its density is higher than polyurethane foam, ranging from 40 kg / m³ to 200 kg / m³, and it is often used as the core material in sandwich structures, widely applied in military, construction, wind power, and transportation fields.

[0006] However, PMI foam also has its limitations as an antenna potting material. Because PMI foam molding requires high-temperature specialized equipment, it is molded into sheets of different thicknesses according to various densities by professional manufacturers and then sold. Users purchase sheets of a certain size and then machine the PMI foam sheets according to the shape of the parts. After machining, the foam is filled. However, the PMI foam processed in this way has no adhesive, so it must be glued twice during filling to become a whole with the cavity / base plate and antenna cover, which makes the molding process complicated. Summary of the Invention

[0007] This invention provides a polyurethane foam composite and its preparation method, aiming to improve the limitations of polyurethane foam and form a potting foam composite with good dimensional stability, high compressive strength, heat resistance, and light weight.

[0008] This invention is achieved through the following technical solution:

[0009] A method for preparing a polyurethane foam composite includes the following steps:

[0010] Step 1: Based on the required cavity to be filled and the weight after filling, estimate the amount of PMI foam and polyurethane foam to be used. Based on the estimation results, design the shape of PMI foam in the cavity so that it forms the skeleton in the cavity, and the area outside the skeleton is the area filled with polyurethane foam.

[0011] Step 2: Cut the PMI foam board. Based on the estimation and design results in Step 1, cut the PMI foam board into a PMI skeleton or multiple PMI foam blocks.

[0012] Step 3: Process the filling and sealing top cover of the filling box to be sealed. At least two vent holes are opened on the filling and sealing top cover, and at least one of the vent holes on the top cover is a filling and sealing port and at least one is an exhaust port.

[0013] Step 4: Fill in the PMI foam blocks. Fill the inner cavity of the potting box with one or more PMI skeletons from Step 2. After the PMI foam blocks are filled, put the potting cap on the top of the potting box.

[0014] Step 5: Fill polyurethane raw material liquid. Mix the various polyurethane raw material liquids evenly to form polyurethane foam. Then, fill the polyurethane foam into the filling box through the filling port on the filling cap and fill the inner cavity of the filling box, so that the polyurethane foam and the PMI foam block in the filling box are bonded to form a mixed product as a whole.

[0015] Step six, curing: The entire filling box after the filling in step five is heated to cure the mixed products inside, resulting in a can-sealed composite of polyurethane foam and PMI foam.

[0016] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0017] 1. In this solution, PMI foam with excellent temperature resistance and dimensional stability is introduced into the polyurethane foam system. Combining the advantages of both, the limitations of polyurethane foam are improved. The PMI foam blocks form a skeleton inside, which plays a supporting role. The overall strength is high, the compressive strength is high, and the dimensional stability is good. This results in a potting foam composite with good dimensional stability, high compressive strength, heat resistance, and light weight.

[0018] 2. In this design, the area outside the skeleton is filled with polyurethane foam. After the polyurethane foam expands, it can easily bond tightly with the PMI foam blocks, making the two integrated and effectively combining their advantages. The PMI skeleton or the skeleton formed by multiple PMI foam blocks plays a supporting role in the entire polyurethane foam composite, while the polyurethane plays a filling role in the overall polyurethane foam composite. The two combine to form a polyurethane foam composite with high strength and good stability.

[0019] This invention combines the convenience and adhesiveness of polyurethane foam with the high specific strength and specific modulus of PMI foam. Through a potting process, the two are bonded together into a whole, resulting in a potted foam composite with good dimensional stability, high compressive strength, heat resistance, and light weight. The method of this invention does not require microscopic modification of the polyurethane foam, but rather combines polyurethane foam and PMI foam to form a composite. The entire operation is convenient and simple, with low processing costs, and is suitable for various production sites. It effectively solves the operational and performance limitations of single polyurethane foam or single PMI foam.

[0020] Furthermore, in step four, when multiple PMI foam blocks are filled into the inner cavity of the potting box, the multiple PMI foam blocks are shaped according to the skeleton shape designed in step one to form a skeleton structure in the inner cavity of the potting box.

[0021] In this solution, when the inner cavity structure of the potting is complex and it is difficult to cut into a complete PMI skeleton due to its complex structure, the PMI foam board can be cut into multiple PMI foam blocks, and the multiple PMI foam blocks can form a support skeleton.

[0022] However, because PMI foam is relatively heavy, and in some cases where there are requirements for potting weight, it is necessary to control the number of PMI foam blocks. This can result in insufficient PMI foam blocks to fill the potting cavity, causing multiple PMI foam blocks to accumulate at the bottom of the potting cavity. As a result, the overall structure of the potted product is uneven, the strength is poor, and the PMI foam blocks and polyurethane foam cannot form a good bond, affecting the quality and stability of the entire product.

[0023] This solution can shape multiple PMI foam blocks into the required skeleton shape to meet the shape requirements of the inner cavity, and at the same time, it can combine with the injected polyurethane foam to provide effective support, thereby improving the strength and stability of the entire product.

[0024] Furthermore, in step two, the shapes of the cut PMI skeleton include fishbone shape and grid shape, and the shapes of the cut PMI foam blocks include sphere, ellipsoid, cylinder, triangular pyramid, and cuboid.

[0025] The shape and size of the PMI skeleton and PMI foam blocks cut out in this solution can be determined according to the inner cavity or liquid channel of the potting box, weight design, or other requirements. The shape of the cut PMI skeleton, including fishbone and grid shapes, can effectively play a supporting role and improve the strength of the product.

[0026] Furthermore, the formula for calculating the mass of the potting complex is as follows:

[0027] m 灌封复合体 =nV PMI泡沫块 ρ PMI泡沫块 +V 聚氨酯 ρ 聚氨酯

[0028] Where n is the number of PMI foam blocks, ρ PMI泡沫块 Given the density of the PMI foam block, ρ 聚氨酯 Given the density of polyurethane foam, V PMI泡沫块 Given the volume of the PMI foam block, V 聚氨酯 Subtract the volume of all PMI foam blocks from the volume of the inner cavity of the potting box.

[0029] Beneficial effects: In this scheme, the weight of the composite can be adjusted according to the formula, so that the weight of the composite we prepare is controllable. Based on the mass of the allowed filling polyurethane raw material liquid, and given the known PMI foam density and polyurethane foam density, the shape and volume of the PMI foam pieces can be designed, so that a stable quality of the potted foam can be obtained after potting.

[0030] Furthermore, in step five, the potting box is tilted at an angle to the horizontal plane before filling with the polyurethane raw material liquid.

[0031] Beneficial effects: In this solution, the potting box is tilted, so when filling the polyurethane raw material liquid, the mixed liquid can expand upward from bottom to top and along the gaps between the PMI foam blocks, gradually filling the inner cavity. Furthermore, since the polyurethane foam has good adhesion before curing, it adheres to the PMI foam blocks during the foaming process, forming a whole.

[0032] The tilted design of the filling box in this solution allows the polyurethane raw material liquid to fill the gaps between the PMI foam blocks more evenly, resulting in better filling effect and better coating effect between the PMI foam blocks and the polyurethane raw material liquid. This improves the overall strength and stability.

[0033] Furthermore, the filling box is tilted towards the filling port, so that the position height of the filling port is lower than the position height of the vent.

[0034] Beneficial effects: This solution allows the polyurethane raw material liquid to gradually fill the potting box, preventing it from overflowing from the vent before filling is complete, thus affecting product quality.

[0035] Furthermore, the filling port and vent on the filling cap are located near opposite sides of the filling box.

[0036] Beneficial effects: This design maximizes the distance between the filling port and the vent, ensuring that the polyurethane filling material can meet the filling requirements to the greatest extent.

[0037] Furthermore, in step five, during the process of filling the potting box with polyurethane foam, when the polyurethane foam comes out from the vent, the vent hole is blocked with a rubber stopper.

[0038] Beneficial effects: This solution can prevent the foaming material (i.e., polyurethane foaming material) from being discharged, thus ensuring the stability of the density and quality of the foaming material.

[0039] Furthermore, in step five, before filling the polyurethane raw material liquid, a release agent is applied to the side of the potting cap facing the inner cavity of the potting box.

[0040] Beneficial effect: This makes it easier to demold and remove the cured composite product later.

[0041] Furthermore, in step three, the potting cap is detachably connected to the potting box.

[0042] Beneficial effect: This makes it easier to disassemble and assemble the filling cap.

[0043] A polyurethane foam composite is prepared using the above-described method for preparing a polyurethane foam composite, comprising polyurethane foam and a plurality of PMI foam blocks, wherein the plurality of PMI foam blocks are filled and fixed inside the polyurethane foam.

[0044] This solution presents a polyurethane foam composite that combines the convenience and adhesiveness of polyurethane foam with the high specific strength and specific modulus of PMI foam. Through a potting process, the two are bonded together into a whole, which has good dimensional stability, high compressive strength, heat resistance, and light weight. Attached Figure Description

[0045] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0046] Figure 1 This is a schematic diagram of the potting process according to an embodiment of the present invention.

[0047] The attached diagram shows the markings and corresponding component names:

[0048] 1. Filling box; 2. PMI foam block; 3. Filling cap; 4. Filling gap; 5. Filling port; 6. Vent port; 7. Filling box. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0050] This embodiment provides a polyurethane foam composite method, including polyurethane foam and multiple PMI foam blocks 2, with the multiple PMI foam blocks 2 filling and fixing inside the polyurethane foam.

[0051] like Figure 1 As shown, a method for preparing a polyurethane foam composite includes the following steps:

[0052] Step 1: Based on the required cavity to be filled and the weight after filling, make a preliminary estimate of the amount of PMI foam and polyurethane foam to be used. Based on the estimate, design the shape of the PMI foam in the cavity so that it forms the skeleton in the cavity, and the area outside the skeleton is the area filled with polyurethane foam.

[0053] Step two: Cut the PMI foam board. Based on the estimation and design results in Step one, cut the PMI foam board into one PMI skeleton or multiple PMI foam blocks 2. The shapes of the cut PMI skeleton include fishbone and grid shapes, and the shapes of the cut PMI foam blocks 2 include spheres, ellipsoids, cylinders, triangular pyramids, and cuboids. The dimensions of the PMI skeleton and PMI foam blocks 2 can be determined according to actual needs, such as the inner cavity dimensions of the filling box 1, the filling gaps 4 (liquid channels) between the PMI foam blocks 2, or the required weight design.

[0054] Step 3: Process the filling top cover 3 of the filling box 11 to be sealed. At least two vent holes are opened on the filling top cover, and at least one of the vent holes on the top cover is a filling port 6 and at least one is an exhaust port 7. The filling port 6 and the exhaust port 7 on the filling top cover 3 are respectively close to the opposite sides of the filling box 11. In this embodiment, the exhaust port 7 is located on the left side of the filling top cover 3 and the filling port 6 is located on the right side of the filling top cover 3.

[0055] Step 4: Fill in PMI foam blocks 2. Fill one or more PMI skeletons or PMI foam blocks 2 from Step 2 into the inner cavity of the potting box 11. After the PMI foam blocks are filled, cover the top of the potting box 1 with the potting cap 3. Specifically: Fill the inner cavity of the potting box 11 with a PMI skeleton or PMI foam blocks 2 of a certain shape. Alternatively, the PMI foam blocks 2 can be arranged according to the shape of the inner cavity of the potting box 11, leaving gaps as flow channels for the mixed liquid raw materials of polyurethane foam.

[0056] When placing PMI foam blocks, a small amount of two-component structural adhesive (such as epoxy) can be used to bond and fix the position of some PMI foam blocks 2. When placing them, PMI foam blocks 2 can completely fill the inner cavity of the filling box or partially fill the inner cavity of the filling box. When multiple PMI foam blocks fill the inner cavity of the filling box, if there are requirements for the weight of the product, resulting in the inner cavity of the filling box not being completely filled, in order to avoid multiple PMI foam blocks accumulating at the bottom of the inner cavity of the filling box, multiple PMI foam blocks can be shaped with epoxy adhesive according to the skeleton shape designed in step one to form a skeleton structure in the inner cavity of the filling box.

[0057] In this embodiment, before filling the polyurethane raw material liquid in step five, a release agent is applied to the side of the filling top cover 3 facing the inner cavity of the filling box 1, and then it is placed on the top of the inner cavity of the filling box and fixed to ensure that the filling top cover 3 will not move or be pushed open by the foaming material (polyurethane raw material liquid) during the filling process. In this embodiment, the filling top cover 3 and the filling box 1 are detachably connected. The filling top cover 3 and the filling box 1 can be detachably fixed by bolts for easy disassembly.

[0058] Step 5: Fill polyurethane raw material liquid. Mix the various polyurethane raw material liquids evenly to form polyurethane foam material. Then fill the polyurethane foam material into the filling box 1 through the filling port 6 on the filling cap 3 and fill the inner cavity of the filling box 11, so that the polyurethane foam material and the PMI foam block 2 in the filling box 11 are bonded to form a mixed product as a whole.

[0059] In this embodiment, the potting box 11 is tilted at an angle to the horizontal plane before the polyurethane raw material liquid is filled, such as... Figure 1As shown, in this embodiment, a pad 5 is placed on the left side and at the bottom of the potting box 11, so that the potting box 1 is tilted towards the potting port 6, and the position height of the potting port 6 is lower than the position height of the vent 7. In this way, the potting port 6 is close to the bottom of the tilted potting box 11, so that the mixed liquid can be poured in from the bottom of the potting box 11, and the mixed liquid expands upward from bottom to top along the filling gaps 4 between the PMI foam blocks 2, gradually filling the inner cavity. Since the polyurethane foam material has good adhesion before curing, it adheres to the PMI foam blocks 2 during the foaming process to form a whole mixed product.

[0060] During the process of filling polyurethane foam into the potting box 11, when the polyurethane foam comes out from the vent 7, use a rubber plug to block the vent hole (including the vent 7 and the potting port 6) to prevent the foam from being discharged. This can ensure the density and quality stability of the foam.

[0061] Step six, curing: The potting box 11 after the filling in step five is heated as a whole to cure the mixed product inside the potting box 11 to obtain a can-sealed composite of polyurethane foam and PMI foam.

[0062] Step 7: After curing, remove the potting cap 3 from the potting box 1 and take out the obtained polyurethane foam and PMI foam canned composite.

[0063] The polyurethane foam and PMI foam potting composite obtained in the inner cavity of the potting box 11 has controllable weight, and due to the reinforcement of PMI foam block 2 inside, the overall strength is high, the compressive strength is high, and the dimensional stability is good.

[0064] Method for adjusting the weight of polyurethane foam and PMI foam potting composite: Based on the allowable mass of polyurethane foam material to be filled, and given the known density of PMI foam and polyurethane foam, design the shape and volume of PMI foam block 2. This will result in a potting foam composite with stable quality after potting.

[0065] The formula for calculating the mass of the potting complex is as follows:

[0066] m 灌封复合体 =nV PMI泡沫块 ρ PMI泡沫块 +V 聚氨酯 ρ 聚氨酯

[0067] Where n is the number of PMI foam blocks, ρ PMI泡沫块 Given the density of the PMI foam block, ρ 聚氨酯 Given the density of polyurethane foam, V PMI泡沫块 Given the volume of the PMI foam block, V 聚氨酯Subtract the volume of all PMI foam blocks from the volume of the inner cavity of potting box 1.

[0068] This invention combines the convenience and adhesiveness of polyurethane foam with the high specific strength and specific modulus of PMI foam. Through a potting process, the two are bonded together into a whole, resulting in a potted foam composite with good dimensional stability, high compressive strength, heat resistance, and lightweight, and the weight is adjustable. The method of this invention does not require microscopic modification of the polyurethane foam, is easy to operate, has low processing costs, and is suitable for various production sites. It effectively solves the operational and performance limitations of single polyurethane foam or single PMI foam.

[0069] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a polyurethane foam composite, characterized in that, Includes the following steps: Step 1: Based on the required cavity to be filled and the weight after filling, estimate the amount of PMI foam and polyurethane foam to be used. Based on the estimation results, design the shape of the PMI foam in the cavity to form a skeleton within the cavity. The area outside the skeleton is the area filled with polyurethane foam. The formula for calculating the mass of the potting composite is as follows: m 灌封复合体 =nV PMI泡沫块 r PMI泡沫块 +V 聚氨酯 r 聚氨酯 Where n is the number of PMI foam blocks, ρ PMI泡沫块 Given the density of the PMI foam block, ρ 聚氨酯 Given the density of polyurethane foam, V PMI泡沫块 Given the volume of the PMI foam block, V 聚氨酯 Subtract the volume of all PMI foam blocks from the volume of the inner cavity of the potting box; Step 2: Cut the PMI foam board. Based on the estimation and design results in Step 1, cut the PMI foam board into a PMI skeleton or multiple PMI foam blocks. Step 3: Process the filling and sealing cap of the filling box to be sealed. At least two vent holes are opened on the filling and sealing cap, and at least one of the vent holes on the sealing cap is a filling and sealing port and at least one is an exhaust port. Step 4: Fill in the PMI foam blocks. Fill one or more PMI skeletons from Step 2 into the inner cavity of the potting box. After the PMI foam blocks are filled, put the potting top cover on the top of the potting box. When multiple PMI foam blocks are filled into the inner cavity of the potting box, shape the multiple PMI foam blocks according to the skeleton shape designed in Step 1 to form a skeleton structure in the inner cavity of the potting box. Step 5: Filling with polyurethane foam material. Mix various polyurethane raw material liquids evenly to form polyurethane foam material. Then, pour the polyurethane foam material into the filling box through the filling port on the top of the filling box and fill the inner cavity of the filling box. During the process of filling the polyurethane foam material into the filling box, when the polyurethane foam material emerges from the vent, use a rubber stopper to block the vent hole, so that the polyurethane foam material and the PMI foam block in the filling box are bonded to form a mixed product as a whole. Before filling with polyurethane raw material liquid, make the filling box tilted at an angle to the horizontal plane, and tilt the filling box towards the filling port so that the position height of the filling port is lower than the position height of the vent. Step six, curing: The entire filling box after the filling in step five is heated to cure the mixed products inside, resulting in a can-sealed composite of polyurethane foam and PMI foam.

2. The method for preparing a polyurethane foam composite according to claim 1, characterized in that, In step two, the shapes of the cut PMI skeleton include fishbone and grid shapes, and the shapes of the cut PMI foam blocks include spheres, ellipsoids, cylinders, triangular pyramids, and cuboids.

3. The method for preparing a polyurethane foam composite according to claim 1, characterized in that, The filling port and vent on the filling cap are located on opposite sides of the filling box.

4. The method for preparing a polyurethane foam composite according to claim 1, characterized in that, Step 5: Before filling with polyurethane raw material liquid, apply release agent to the side of the potting cap facing the inner cavity of the potting box.

5. A polyurethane foam composite, prepared using the method for preparing a polyurethane foam composite according to any one of claims 1-4, characterized in that, It includes polyurethane foam and multiple PMI foam blocks, with the multiple PMI foam blocks filling and fixing inside the polyurethane foam.

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