In-mold foaming part with bionic network support and preparation method of in-mold foaming part

Abstract

The invention discloses a preparation method of an in-mold foamed rigid foam workpiece, which comprises the following steps: polymerizing a polymeric monomer material to obtain a polymer; the polymer is crushed and then subjected to primary foaming, and primary foaming particles are obtained; filling a mold with the primary foaming particles, laying at least one bionic network layer in the mold, and carrying out secondary in-mold foaming to obtain the in-mold foaming rigid foam part, wherein the bionic network layer can be selected to be two or more than two layers. According to the method, a bionic network structure framework is implanted in PMI particle foaming, a particle matrix-bionic network synergistic enhancement system is constructed, the mechanical property bottleneck of a traditional particle foaming part is broken through, and multi-dimensional performance jump is achieved.

Description

Technical Field

[0001] This application relates to the field of materials preparation technology, and in particular to a rigid foam component that can be prepared by in-mold foaming. Background Technology

[0002] In aerospace, high-end equipment manufacturing, and other fields, PMI foam is often used to manufacture irregularly shaped structural components such as drone wings and protective parts for special vehicles due to its lightweight and high strength properties. However, traditional monolithic PMI foam engraving processes have significant drawbacks: Firstly, during the processing of irregularly shaped parts, the material removal rate of the foam is as high as 70%, resulting in significant material waste and high costs. For example, engraving a monolithic foam for drone wings is costly, and the processing of complex curved surfaces can easily cause internal micro-cracks, reducing structural reliability. Secondly, for complex cavity structures, the engraving process is cumbersome and has a long production cycle, making it difficult to meet the demands of mass production and high efficiency.

[0003] To overcome cost and efficiency bottlenecks, PMI granule in-mold foaming technology has been applied. This technology precisely lays PMI granules layer by layer according to the cavity shape, and then foams them at high temperature to form a single piece, increasing material utilization to over 85% and reducing overall costs by 40%-60%. However, since the bonding between granules relies solely on their own melting during foaming, the interlayer bonding strength is 30%-50% lower than that of a whole piece of foam. When the part is subjected to tensile and impact loads, the particle-to-particle interface is prone to peeling and cracking, which has become the core obstacle restricting its large-scale application under high-stress conditions. Summary of the Invention

[0004] This application provides an in-mold foamed part with biomimetic network support to solve the technical problems of insufficient tensile properties and impact resistance under in-mold foaming of PMI particles.

[0005] Specifically, this application provides the following technical solutions:

[0006] 1. A method for preparing an in-mold foamed rigid foam part, comprising:

[0007] The monomer materials are polymerized to obtain a polymer.

[0008] The polymer is crushed and then foamed once to obtain primary foamed particles.

[0009] The mold is filled with the primary foamed particles, and at least one layer of biomimetic network layer is laid therein, which can be two or more layers, for secondary in-mold foaming to obtain the in-mold foamed rigid foam part.

[0010] 2. The preparation method according to item 1, wherein the biomimetic network layer is a fiber layer with a spider web-like structure.

[0011] 3. The preparation method according to item 1 or 2, wherein the biomimetic network layer is prepared by the following method:

[0012] The fiber membrane is laser-cut into the aforementioned spiderweb-like structure.

[0013] Preferably, the fiber membrane is selected from polyimide nanofiber membranes, carbon fiber membranes, or basalt fiber membranes.

[0014] More preferably, the thickness of the fiber membrane is 12-25 μm.

[0015] 4. The preparation method according to item 3, wherein the spider web-like structure includes a plurality of radial lines radiating from the center and a plurality of concentric circles surrounding the center.

[0016] 5. The preparation method according to item 4, wherein the spacing between the plurality of concentric circles is 1–15 mm, and / or the angle between the plurality of radiation lines is 12–36°.

[0017] Preferably, the spacing between the plurality of concentric circles gradually decreases as the distance from the center of the circle increases.

[0018] Preferably, the angles between the plurality of radiation lines are equal.

[0019] 6. The preparation method according to item 4, wherein the width of the fiber forming the concentric circles and radial lines is 12-25 μm.

[0020] 7. The preparation method according to item 1, wherein the interval between the plurality of biomimetic network layers is 5 to 15% of the total thickness of the primary foamed particles, and the distance from the bottom and top of the primary foamed particles is 15 to 25% of the total thickness.

[0021] 8. The preparation method according to item 1, wherein the polymeric monomer material is selected from one or more of methacrylic acid, acrylic acid, methacrylonitrile, and acrylonitrile.

[0022] 9. The preparation method according to item 1, wherein the temperature of the first foaming is 150-200℃ and the reaction time is 0.5-3 hours.

[0023] 10. The preparation method according to item 1, wherein the particle size of the primary foaming particles is 5-15 mesh.

[0024] 11. The preparation method according to item 1, wherein the temperature of the secondary in-mold foaming is 180-230℃ and the reaction time is 0.5-5 hours.

[0025] 12. Rigid foam components prepared according to any one of items 1 to 11.

[0026] The effects of the invention

[0027] The in-mold foamed parts and their preparation method provided in this application construct a "particle matrix-biomimetic network" synergistic enhancement system by implanting a biomimetic network structure skeleton into PMI particle foaming, thereby breaking through the mechanical performance bottleneck of traditional particle foamed parts and achieving a multi-dimensional performance leap.

[0028] Enhanced tensile and impact resistance: A biomimetic network constructed from high-strength fibers forms a dual effect of "mechanical interlocking + interfacial bonding" with the PMI particle matrix. Under tension, the network structure acts like "fiber skeletons" to distribute force throughout the entire structure; under impact, the network absorbs energy through elastic deformation, enabling it to withstand the aerodynamic loads of high-speed UAV flight and the impact scenarios of equipment protective components.

[0029] Maintaining lightweight performance: By using fiber materials to construct the network, the mechanical properties can be improved while maintaining the lightweight advantage of PMI materials.

[0030] Cost reduction: Compared with the existing technology of carving a whole piece of PMI foam to obtain the part, the in-mold foaming process of this solution can significantly reduce costs.

[0031] Using the preparation method of this application, the part obtained by in-mold foaming after implanting a biomimetic fiber network can achieve structural reinforcement, and can be further thinned and weight reduced in the design, achieving a balance of "lightness, strength and economy" in the part. Detailed Implementation

[0032] The present application will now be described in further detail with reference to specific embodiments. The embodiments given are intended to enable a more thorough understanding of the present application and to fully convey the scope of the present application to those skilled in the art.

[0033] It should be noted that the terms "comprising" or "including" used throughout the specification and appendices are open-ended and should be interpreted as "comprising but not limited to". The subsequent descriptions in the specification are preferred embodiments for carrying out this application; however, these descriptions are for the purpose of understanding the general principles of the specification and are not intended to limit the scope of this application. The scope of protection of this application shall be determined by the appendices.

[0034] This application provides a method for preparing rigid foam parts through in-mold foaming. The method includes laying a biomimetic network structure fiber layer in polymer particles, and then foaming it in a mold to obtain the foam part. The biomimetic network layer has a spider web-like structure, and its mesh-like fiber filaments exist in the foam part, forming a cooperative load-bearing system with the foam particle matrix.

[0035] In a specific implementation, the method includes the following steps:

[0036] The monomer materials are polymerized to obtain a polymer.

[0037] The polymer is crushed and then foamed once to obtain primary foamed particles.

[0038] The mold is filled with the primary foamed particles, and at least one layer of biomimetic network layer is laid therein, which can be two or more layers, for secondary in-mold foaming to obtain the in-mold foamed rigid foam part.

[0039] In specific embodiments, the method of this application can be used in the in-mold foaming preparation of PMI (polymethacrylimide) foam materials. In other optional embodiments, the method can also be used in the preparation of other foam materials such as PET (polyethylene terephthalate), PVC (polyvinyl chloride), PMMA (polymethyl methacrylate), and PEI (polyetherimide).

[0040] In some specific embodiments, the polymeric monomer is selected from one or more of methacrylic acid, acrylic acid, methacrylonitrile, and acrylonitrile.

[0041] In some specific embodiments, the polymerization is carried out by mixing the polymerizable monomer with an initiator and a foaming agent in a certain proportion.

[0042] In some preferred embodiments, the polymeric monomers are methacrylic acid and methacrylonitrile, and the mass ratio of methacrylic acid, methacrylonitrile to initiator and foaming agent is 50-80:30-60:0.1-3:1-10.

[0043] In some preferred embodiments, the methacrylic acid monomer is in the amount of 50, 55, 60, 65, 70, 75, or 80 parts by weight; the methacrylonitrile is in the amount of 30, 35, 40, 45, 50, 55, or 60 parts by weight; the initiator is in the amount of 0.1, 0.2, 0.5, 0.8, 1.0, 1.5, 2, 2.5, or 3 parts by weight; and the foaming agent is in the amount of 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 parts by weight.

[0044] In some specific embodiments, the polymerization temperature is 30-80℃, and the polymerization time is 24-240h. For example, the polymerization temperature is 30℃, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 80℃ or any range thereof; the polymerization time is 24h, 48h, 72h, 120h, 150h, 180h, 200h, 240h or any range thereof.

[0045] In some specific embodiments, the obtained polymer is crushed into polymer particles of 15-30 mesh using a crusher. For example, the mesh sizes are 15, 18, 20, 22, 23, 24, 25, 26, 28, or 30 mesh.

[0046] In some preferred embodiments, the polymer particles are 7 to 10 mesh, more preferably 8 mesh.

[0047] In a specific embodiment, the polymer particles are foamed once.

[0048] In a specific embodiment, the temperature of the primary foaming is 150-200℃, and the reaction time is 0.5-3h. For example, the temperature of the primary foaming is 150, 180, 200, 220, 250℃ or any range thereof; the reaction time is 0.5h, 1h, 1.5h, 2h, 2.5h, 3h or any range thereof.

[0049] In a specific embodiment, the polymer particles are foamed once to obtain foamed particles.

[0050] In some specific embodiments, the particle size of the obtained primary foamed particles is 5-15 mesh. For example, 5 mesh, 6 mesh, 7 mesh, 8 mesh, 9 mesh, 10 mesh, 11 mesh, 12 mesh, 13 mesh, 14 mesh, and 15 mesh.

[0051] In a specific implementation, the primary foamed particles and the biomimetic network layer are filled into a mold together for secondary foaming.

[0052] In a specific implementation, the biomimetic network layer is a fiber layer with a spider web-like structure.

[0053] In some specific embodiments, the biomimetic network layer is made of fiber membrane by laser cutting.

[0054] In some specific embodiments, the fiber membrane is selected from polyimide nanofiber membranes, carbon fiber membranes, or basalt fiber membranes.

[0055] In some specific embodiments, the thickness of the fiber membrane is 12-25 μm.

[0056] In some specific embodiments, the spider web-like structure includes several radial lines radiating from the center and several concentric circles surrounding the center.

[0057] In the embodiments of this application, the center of the circle is the origin of the center of the biomimetic network layer.

[0058] In some specific embodiments, the spacing between the plurality of concentric circles is 1 to 15 mm, for example, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm or any range thereof.

[0059] In some specific embodiments, the angle between the plurality of radiation lines is 12 to 36°, for example, 12°, 15°, 20°, 24°, 28°, 30°, 32°, 36° or any range thereof.

[0060] In a specific implementation, the spacing between any two concentric circles may be the same or different.

[0061] In some specific embodiments, the spacing between the plurality of concentric circles gradually decreases as the distance from the center of the circle increases.

[0062] In specific implementations, the angles between the plurality of radiation lines may be equal or unequal.

[0063] In some specific implementations, the angles between the plurality of radiation lines are equal.

[0064] In some preferred embodiments, the mesh area in the spiderweb-like structure is 5-20 mm. 2 The mesh is a grid formed by several concentric circles and radial lines that make up the biomimetic network layer. The area of ​​the mesh is determined by the spacing between the concentric circles and the angle between the radial lines.

[0065] In specific implementations, the spacing between the concentric circles or the angle between the radial lines can be reasonably varied according to the type, size, and performance requirements of the foam particles.

[0066] In a specific implementation, the biomimetic network layer can be laid in one or more layers between the foamed particles.

[0067] In a specific implementation, the biomimetic network layer should not be laid too close to the bottom or top of the overall foam layer.

[0068] In specific embodiments, the biomimetic network layer is laid starting at a certain distance from the top or bottom of the mold. In some specific embodiments, the distance from the bottom and top of the primary foaming particles to the biomimetic network layer is 15-25% or more of the total thickness, that is, the distance from the bottom or top of the foaming mold is 15-25% or more of the total height of the mold. For example, the biomimetic network layer is laid starting at a position 20% of the total height from the top or bottom of the mold.

[0069] In some specific embodiments, the biomimetic network layer is laid in two or more layers between the primary foamed particles, with the interval between each layer being 5 to 15% of the total thickness of the primary foamed particles.

[0070] In specific implementations, the spacing of the biomimetic network layers can be reasonably varied according to the type, size, and performance requirements of the foam particles.

[0071] In specific implementations, the placement of the biomimetic network layer can be determined based on the shape, structure, and usage characteristics of the foamed part to enhance the mechanical properties of specific areas. In actual use scenarios, certain areas of some foamed parts may experience greater pressure or impact, often becoming points of failure. Therefore, a biomimetic network layer can be strategically placed at these locations to strengthen the impact resistance of those areas and improve the overall service life of the part.

[0072] In some specific embodiments, the cutting width of the fiber filaments forming the concentric circles and radial lines is 12-25 μm.

[0073] In some specific embodiments, the cross-sectional area of ​​the fiber is 100-500 μm. 2 For example, it can be 100μm 2 150μm 2 200μm 2 350μm 2 300μm 2 350μm 2 400μm 2 450μm 2 500μm 2 Or any interval thereof.

[0074] In a specific implementation, the thickness of the fibers forming the biomimetic network layer can be obtained by laser cutting according to actual needs.

[0075] In a specific embodiment, the primary particles with the biomimetic network layer are subjected to secondary in-mold foaming. In this embodiment, the temperature for the secondary in-mold foaming is 180-230℃, and the reaction time is 0.5-5 hours.

[0076] This application also provides rigid foam components prepared by the aforementioned preparation method.

[0077] This application addresses the shortcomings of insufficient tensile and impact resistance in in-mold foaming of PMI granules by providing an innovative solution using biomimetic network reinforcement technology. The key lies in embedding a specifically designed biomimetic network structure between each layer of PMI granules during the in-mold foaming process. Through the foaming process, the network and the granule matrix are tightly integrated, forming a collaborative load-bearing system of "granule matrix-biomimetic network". The biomimetic network typically uses high-strength fiber materials to ensure that the flowability of the foamed granules is not affected, while simultaneously achieving interlayer mechanical anchoring. When the part is subjected to tensile loads, the biomimetic network, through the mechanical interlocking of the fiber nodes with the upper and lower granule layers, rapidly disperses the local tensile force to adjacent granule layers, preventing single granule layers from breaking due to stress overload. Under impact loads, the network fibers undergo elastic deformation, efficiently absorbing energy and transmitting the impact force to the entire part along the network path. This structure acts like a "stress buffer-dispersion system" built inside the part, providing a solid defense for structural stability.

[0078] Example

[0079] This application provides a general and / or specific description of the materials and test methods used in the experiments. In the following examples, unless otherwise specified, % represents wt%, i.e., weight percentage. All reagents or instruments used, unless otherwise specified, are commercially available conventional reagent products or conventional laboratory instruments.

[0080] Example 1: Preparation of In-Mold Foamed Parts

[0081] In-mold foamed rigid foam parts are prepared using the following method:

[0082] (1) Preparation of biomimetic fiber network: A polyimide nanofiber membrane (14 μm thick) was laser-cut into a spider web-like fiber network composed of several concentric circles and radial lines radiating from the center (the cross-sectional area of ​​the fiber filaments was 200 μm). 2 The spacing between the concentric circles gradually increases from 5mm to 11mm in the direction away from the center, and the angle between the radiating lines is 18°.

[0083] (2) Preparation of polymer: Methacrylic acid, methacrylonitrile, azobisisobutyronitrile and formamide were added to the reactor in a mass ratio of (70:40:0.5:5) and polymerized at 60°C for 120 h to obtain polymer.

[0084] (3) Preparation of primary foamed granules: The polymer is crushed using a crusher and the particle size is set to 8 mesh to obtain primary foamed granules.

[0085] (4) Filling with foam material: Fill the 100mm thick mold with primary foam particles (the upper right and lower left corners of the part are more susceptible to impact and are easily damaged). After laying a 20mm thick layer of primary foam particles at the bottom, begin laying the biomimetic network fiber layer. The interval between each two layers is about 10% of the total thickness of the part, with primary foam particles evenly filling each layer. When laying the fiber layer, alternately lay the layers with the vertical position of the easily damaged points at the lower left and upper right corners as the center point. A 20mm thick layer of primary foam particles is laid between the top layer of biomimetic network fiber and the top layer to fill the mold.

[0086] (5) Secondary foaming: The foaming conditions are 180℃, foaming for 2 hours, and the reaction ends to obtain foam parts that have been foamed in the mold.

[0087] The molds used in the following examples and comparative examples are the same as those in Example 1.

[0088] Example 2: Preparation of In-Mold Foamed Parts

[0089] In-mold foamed rigid foam parts are prepared using the following method:

[0090] (1) Preparation of biomimetic fiber network: A polyimide nanofiber membrane (14 μm thick) was laser-cut into a spider web-like fiber network composed of several concentric circles and radial lines radiating from the center (the cross-sectional area of ​​the fiber filaments was 200 μm). 2 The spacing between the concentric circles gradually increases from 9mm to 14mm in the direction away from the center, and the angle between the radiating lines is 30°.

[0091] (2) Preparation of polymer: Methacrylic acid, methacrylonitrile, azobisisobutyronitrile and formamide were added to the reactor in a mass ratio of (70:40:0.5:5) and polymerized at 60°C for 120 h to obtain polymer.

[0092] (3) Preparation of primary foamed granules: The polymer is crushed using a crusher and the particle size is set to 8 mesh to obtain primary foamed granules.

[0093] (4) Filling with foam material: Fill the 100mm thick mold with primary foam particles (the upper right and lower left corners of the part are more susceptible to impact and are easily damaged). After laying a 20mm thick layer of primary foam particles at the bottom, begin laying the biomimetic network fiber layer. The interval between each two layers is about 10% of the total thickness of the part, with primary foam particles evenly filling each layer. When laying the fiber layer, alternately lay the layers with the vertical position of the easily damaged points at the lower left and upper right corners as the center point. A 20mm thick layer of primary foam particles is laid between the top layer of biomimetic network fiber and the top layer to fill the mold.

[0094] (5) Secondary foaming: The foaming conditions are 180℃, foaming for 2 hours, and the reaction ends to obtain foam parts that have been foamed in the mold.

[0095] Example 3: Preparation of In-Mold Foamed Parts

[0096] In-mold foamed rigid foam parts are prepared using the following method:

[0097] (1) Preparation of biomimetic fiber network: A polyimide nanofiber membrane (14 μm thick) was laser-cut into a spider web-like fiber network composed of several concentric circles and radial lines radiating from the center (the cross-sectional area of ​​the fiber filaments was 200 μm). 2 The spacing between the concentric circles gradually increases from 2mm to 8mm in the direction away from the center, and the angle between the radiating lines is 14.4°.

[0098] (2) Preparation of polymer: Methacrylic acid, methacrylonitrile, azobisisobutyronitrile and formamide were added to the reactor in a mass ratio of (70:40:0.5:5) and polymerized at 60°C for 120 h to obtain polymer.

[0099] (3) Preparation of primary foamed granules: The polymer is crushed using a crusher and the particle size is set to 8 mesh to obtain primary foamed granules.

[0100] (4) Filling with foam material: Fill the 100mm thick mold with primary foam particles (the upper right and lower left corners of the part are more susceptible to impact and are easily damaged). After laying a 20mm thick layer of primary foam particles at the bottom, begin laying the biomimetic network fiber layer. The interval between each two layers is about 10% of the total thickness of the part, with primary foam particles evenly filling each layer. When laying the fiber layer, alternately lay the layers with the vertical position of the easily damaged points at the lower left and upper right corners as the center point. A 20mm thick layer of primary foam particles is laid between the top layer of biomimetic network fiber and the top layer to fill the mold.

[0101] (5) Secondary foaming: The foaming conditions are 180℃, foaming for 2 hours, and the reaction ends to obtain foam parts that have been foamed in the mold.

[0102] Example 4: Preparation of In-Mold Foamed Parts

[0103] In-mold foamed rigid foam parts are prepared using the following method:

[0104] (1) Preparation of biomimetic fiber network: A polyimide nanofiber membrane (14 μm thick) was laser-cut into a spider web-like fiber network composed of several concentric circles and radial lines radiating from the center (the cross-sectional area of ​​the fiber filaments was 200 μm). 2The spacing between the concentric circles gradually increases from 5mm to 11mm in the direction away from the center, and the angle between the radiating lines is 18°.

[0105] (2) Preparation of polymer: Methacrylic acid, methacrylonitrile, azobisisobutyronitrile and formamide were added to the reactor in a mass ratio of (70:40:0.5:5) and polymerized at 60°C for 120 h to obtain polymer.

[0106] (3) Preparation of primary foamed granules: The polymer is crushed using a crusher and the particle size is set to 5 mesh to obtain primary foamed granules.

[0107] (4) Filling with foam material: Fill the 100mm thick mold with primary foam particles (the upper right and lower left corners of the part are more susceptible to impact and are easily damaged). After laying a 20mm thick layer of primary foam particles at the bottom, begin laying the biomimetic network fiber layer. The interval between each two layers is about 10% of the total thickness of the part, with primary foam particles evenly filling each layer. When laying the fiber layer, alternately lay the layers with the vertical position of the easily damaged points at the lower left and upper right corners as the center point. A 20mm thick layer of primary foam particles is laid between the top layer of biomimetic network fiber and the top layer to fill the mold.

[0108] (5) Secondary foaming: The foaming conditions are 180℃, foaming for 2 hours, and the reaction ends to obtain foam parts that have been foamed in the mold.

[0109] Example 5: Preparation of In-Mold Foamed Parts

[0110] In-mold foamed rigid foam parts are prepared using the following method:

[0111] (1) Preparation of biomimetic fiber network: A polyimide nanofiber membrane (14 μm thick) was laser-cut into a spider web-like fiber network composed of several concentric circles and radial lines radiating from the center (the cross-sectional area of ​​the fiber filaments was 200 μm). 2 The spacing between the concentric circles gradually increases from 5mm to 11mm in the direction away from the center, and the angle between the radiating lines is 18°.

[0112] (2) Preparation of polymer: Methacrylic acid, methacrylonitrile, azobisisobutyronitrile and formamide were added to the reactor in a mass ratio of (70:40:0.5:5) and polymerized at 60°C for 120 h to obtain polymer.

[0113] (3) Preparation of primary foamed granules: The polymer is crushed using a crusher and the particle size is set to 14 mesh to obtain primary foamed granules.

[0114] (4) Filling with foam material: Fill the 100mm thick mold with primary foam particles (the upper right and lower left corners of the part are more susceptible to impact and are easily damaged). After laying a 20mm thick layer of primary foam particles at the bottom, begin laying the biomimetic network fiber layer. The interval between each two layers is about 10% of the total thickness of the part, with primary foam particles evenly filling each layer. When laying the fiber layer, alternately lay the layers with the vertical position of the easily damaged points at the lower left and upper right corners as the center point. A 20mm thick layer of primary foam particles is laid between the top layer of biomimetic network fiber and the top layer to fill the mold.

[0115] (5) Secondary foaming: The foaming conditions are 180℃, foaming for 2 hours, and the reaction ends to obtain foam parts that have been foamed in the mold.

[0116] Example 6: Preparation of In-Mold Foamed Parts

[0117] In-mold foamed rigid foam parts are prepared using the following method:

[0118] (1) Preparation of biomimetic fiber network: A polyimide nanofiber membrane (14 μm thick) was laser-cut into a spider web-like fiber network composed of several concentric circles and radial lines radiating from the center (the cross-sectional area of ​​the fiber filaments was 200 μm). 2 The spacing between the concentric circles gradually increases from 5mm to 11mm in the direction away from the center, and the angle between the radiating lines is 18°.

[0119] (2) Preparation of polymer: Methacrylic acid, methacrylonitrile, azobisisobutyronitrile and formamide were added to the reactor in a mass ratio of (70:40:0.5:5) and polymerized at 60°C for 120 h to obtain polymer.

[0120] (3) Preparation of primary foamed granules: The polymer is crushed using a crusher and the particle size is set to 8 mesh to obtain primary foamed granules.

[0121] (4) Filling with foam material: First-stage foam granules are filled into the 100mm thick mold (the upper right and lower left corners of the part are more susceptible to impact and are therefore vulnerable to damage). After laying a bottom layer of 20mm thick first-stage foam granules, the biomimetic network fiber layer is then laid. The interval between each two layers is approximately 10% of the total thickness of the part, with first-stage foam granules evenly distributed within each layer. The fiber layers are laid with the center point perpendicular to the center of the part as the origin. A 20mm thick layer of first-stage foam granules is placed between the top layer of biomimetic network fiber and the top layer to fill the mold.

[0122] (5) Secondary foaming: The foaming conditions are 180℃, foaming for 2 hours, and the reaction ends to obtain foam parts that have been foamed in the mold.

[0123] Comparative Example 1: Preparation of In-Mold Foamed Parts

[0124] In-mold foamed rigid foam parts are prepared using the following method:

[0125] (1) Preparation of biomimetic fiber network: A polyimide nanofiber membrane (14 μm thick) was laser-cut into a spider web-like fiber network composed of several concentric circles and radial lines radiating from the center (the cross-sectional area of ​​the fiber filaments was 200 μm). 2 The spacing between concentric circles gradually increases from 0.1 mm to 1 mm in the direction away from the center, and the angle between the radiating lines is 10°.

[0126] (2) Preparation of polymer: Methacrylic acid, methacrylonitrile, azobisisobutyronitrile and formamide were added to the reactor in a mass ratio of (70:40:0.5:5) and polymerized at 60°C for 120 h to obtain polymer.

[0127] (3) Preparation of primary foamed granules: The polymer is crushed using a crusher and the particle size is set to 8 mesh to obtain primary foamed granules.

[0128] (4) Filling with foam material: Fill the 100mm thick mold with primary foam particles (the upper right and lower left corners of the part are more susceptible to impact and are easily damaged). After laying a 20mm thick layer of primary foam particles at the bottom, begin laying the biomimetic network fiber layer. The interval between each two layers is about 10% of the total thickness of the part, with primary foam particles evenly filling each layer. When laying the fiber layer, alternately lay the layers with the vertical position of the easily damaged points at the lower left and upper right corners as the center point. A 20mm thick layer of primary foam particles is laid between the top layer of biomimetic network fiber and the top layer to fill the mold.

[0129] (5) Secondary foaming: The foaming conditions are 180℃, foaming for 2 hours, and the reaction ends to obtain foam parts that have been foamed in the mold.

[0130] Comparative Example 2: Preparation of In-Mold Foamed Parts

[0131] In-mold foamed rigid foam parts are prepared using the following method:

[0132] (1) Preparation of biomimetic fiber network: A polyimide nanofiber membrane (14 μm thick) was laser-cut into a spider web-like fiber network composed of several concentric circles and radial lines radiating from the center (the cross-sectional area of ​​the fiber filaments was 200 μm). 2 The spacing between the concentric circles gradually increases from 5mm to 11mm in the direction away from the center, and the angle between the radiating lines is 18°.

[0133] (2) Preparation of polymer: Methacrylic acid, methacrylonitrile, azobisisobutyronitrile and formamide were added to the reactor in a mass ratio of (70:40:0.5:5) and polymerized at 60°C for 120 h to obtain polymer.

[0134] (3) Preparation of primary foamed granules: The polymer is crushed using a crusher, and the particle size is set to 18 mesh to obtain primary foamed granules.

[0135] (4) Filling with foam material: Fill the 100mm thick mold with primary foam particles (the upper right and lower left corners of the part are more susceptible to impact and are easily damaged). After laying a 20mm thick layer of primary foam particles at the bottom, begin laying the biomimetic network fiber layer. The interval between each two layers is about 10% of the total thickness of the part, with primary foam particles evenly filling each layer. When laying the fiber layer, alternately lay the layers with the vertical position of the easily damaged points at the lower left and upper right corners as the center point. A 20mm thick layer of primary foam particles is laid between the top layer of biomimetic network fiber and the top layer to fill the mold.

[0136] (5) Secondary foaming: The foaming conditions are 180℃, foaming for 2 hours, and the reaction ends to obtain foam parts that have been foamed in the mold.

[0137] Comparative Example 3: Preparation of In-Mold Foamed Parts

[0138] In-mold foamed rigid foam parts are prepared using the following method:

[0139] (1) Preparation of biomimetic fiber network: A polyimide nanofiber membrane (14 μm thick) was laser-cut into a fiber mesh composed of several square grids (the cross-sectional area of ​​the fiber filaments was 200 μm). 2 The mesh size is 9mm.

[0140] (2) Preparation of polymer: Methacrylic acid, methacrylonitrile, azobisisobutyronitrile and formamide were added to the reactor in a mass ratio of (70:40:0.5:5) and polymerized at 60°C for 120 h to obtain polymer.

[0141] (3) Preparation of primary foamed particles: The prepolymer is crushed with a crusher and the particle size is set to 8 mesh to obtain primary foamed particles.

[0142] (4) Filling with foam material: Fill the 100mm thick mold with primary foam particles (the upper right and lower left corners of the part are more susceptible to impact and are easily damaged). After laying a 20mm thick layer of primary foam particles at the bottom, begin laying the biomimetic network fiber layer. The interval between each two layers is about 10% of the total thickness of the part, and primary foam particles are evenly filled in between. A 20mm thick layer of primary foam particles is laid between the top biomimetic network fiber layer and the top layer to fill the mold.

[0143] (5) Secondary foaming: The foaming conditions are 180℃, foaming for 2 hours, and the reaction ends to obtain foam parts that have been foamed in the mold.

[0144] Comparative Example 4: Preparation of In-Mold Foamed Parts

[0145] In-mold foamed rigid foam parts are prepared using the following method:

[0146] (1) Preparation of prepolymer: Methacrylic acid, methacrylonitrile, azobisisobutyronitrile and formamide were added to the reactor in a mass ratio of (70:40:0.5:5) and the polymerization reaction was carried out at 60°C for 120 h.

[0147] (2) Preparation of primary foamed particles: The prepolymer is crushed with a crusher and the particle size is set to 8 mesh to obtain primary foamed particles.

[0148] (3) Filling with foam material: Fill the mold with foam particles once in the 100mm thick mold (the upper right and lower left of the part are more likely to be impacted).

[0149] (4) Secondary foaming: The foaming conditions are 180℃, foaming for 2 hours, and the reaction ends to obtain foam parts that have been foamed in the mold.

[0150] Experimental Example 1

[0151] The porous foam materials obtained in the above embodiments and comparative examples were subjected to performance tests. The results are shown in Table 1. The test standards and methods included:

[0152] Apparent density was determined according to GB / T 6343-2009 Determination of apparent density of foamed plastics and rubber; tensile strength was determined according to ASTM-D638-2010 Tensile strength of plastics; compressive strength was determined according to GB / T8813-2008 Determination of compressive properties of rigid foamed plastics.

[0153] Average Absorbed Energy Test Method:

[0154] 1) Fix a marker vertically at the bottom of the test stand to ensure that the marker does not wobble. Make a square clamp that is 0.5cm higher than the marker. Fix the sample on the square clamp, ensuring that the sample does not wobble and that the center of the bottom is 0.5cm away from the marker.

[0155] 2) Select one sample of each type for pre-testing. Adjust the ball mass and drop height, starting from a lower height (0.5m) and gradually increasing it (0.2m each time) until the sample shows obvious damage (cracks or dents deeper than 0.5cm, etc.) or marker marks appear on the bottom surface of the sample (vertical deformation of the sample >50%). This indicates that the sample has reached the upper limit of its impact resistance performance. Record the ball mass (m), drop height (h0), and rebound height (h1). This data is not included in the final result.

[0156] 3) Test the mass and drop height of the ball obtained in 2) once for each sample. Test 5 samples in each group and record h1 five times. Measure the depth of the indentation (if any) and record the direction of crack propagation.

[0157] Energy absorbed: Ea = mg(h0 - h1)

[0158] Table 1. Material performance test results

[0159]

[0160]

[0161] The experimental results show that the preparation method described in this application, by laying a certain number of layers of spider web-structured fiber network in the foamed particles, allows the network to be tightly integrated with the particle matrix, forming a synergistic load-bearing system, which can effectively improve the mechanical properties of the resulting parts. Since the laying of the fiber network will affect the internal structure of the foam material to a certain extent, the shape and mesh density of the biomimetic network need to be reasonably selected. Too dense a mesh will lead to weak interlayer adhesion in the foam, and the composite structure is prone to interlayer defects, thus affecting mechanical properties and impact resistance. While a too sparse mesh will make the interlayer adhesion stronger, the improvement in impact resistance and mechanical properties is very limited. The radial structure resembling a spider web can strengthen the structure at the center of the web. When laid in vulnerable areas of the part, it can enhance energy absorption at those locations, showing a significant improvement for parts with special structures compared to a uniform network structure.

[0162] The above description is merely a preferred embodiment of this application and is not intended to limit the application in any other way. Any person skilled in the art may make changes or modifications to the disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of this application without departing from the scope of the technical solution of this application shall still fall within the protection scope of this application.

Claims

1. A method for preparing an in-mold foamed rigid foam part, comprising: The monomer materials are polymerized to obtain a polymer. The polymer is crushed and then foamed once to obtain primary foamed particles. The mold is filled with the primary foamed particles, and at least one layer of biomimetic network layer is laid therein, which can be two or more layers, for secondary in-mold foaming to obtain the in-mold foamed rigid foam part.

2. The preparation method according to claim 1, wherein, The biomimetic network layer is a fiber layer with a spider web-like structure.

3. The preparation method according to claim 1 or 2, wherein, The biomimetic network layer is fabricated using the following method: The fiber membrane is laser-cut into the aforementioned spiderweb-like structure. Preferably, the fiber membrane is selected from polyimide nanofiber membranes, carbon fiber membranes, or basalt fiber membranes. More preferably, the thickness of the fiber membrane is 12-25 μm.

4. The preparation method according to claim 3, wherein, The spiderweb-like structure includes several radial lines radiating from the center and several concentric circles surrounding the center.

5. The preparation method according to claim 4, wherein, The spacing between the concentric circles is 1–15 mm, and / or the angle between the radial lines is 12–36°. Preferably, the spacing between the plurality of concentric circles gradually decreases as the distance from the center of the circle increases. Preferably, the angles between the plurality of radiation lines are equal.

6. The preparation method according to claim 4, wherein, The cross-sectional area of ​​the fibers forming the concentric circles and radial lines is 100-500 μm. 2 .

7. The preparation method according to claim 1, wherein, The interval between the several layers of biomimetic network is 5 to 15% of the total thickness of the primary foamed particles, and the distance from the bottom and top of the primary foamed particles is 15 to 25% of the total thickness.

8. The preparation method according to claim 1, wherein, The polymer monomer material is selected from one or more of methacrylic acid, acrylic acid, methacrylonitrile, and acrylonitrile.

9. The preparation method according to claim 1, wherein, The temperature for the first foaming is 150-200℃, and the reaction time is 0.5-3 hours.

10. The preparation method according to claim 1, wherein, The particle size of the primary foaming particles is 5-15 mesh.

11. The preparation method according to claim 1, wherein, The secondary in-mold foaming temperature is 180-230℃, and the reaction time is 0.5-5 hours.

12. Rigid foam components prepared by the preparation method according to any one of claims 1 to 11.

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