A photopolymer 3D printed part and its application

Abstract

This invention provides a photopolymerizable 3D printed part and its application. The photopolymerizable 3D printed part of this invention is an elastomer obtained by photopolymerizable 3D printing, and the crosslinking density of the photopolymerizable 3D printed part is 0.001–10 mmol / cm². 3 Furthermore, its glass transition temperature is below 30℃.

Description

[0001] This application is a divisional application filed on November 29, 2021, with application number "202111433487.9". Technical Field

[0002] This invention relates to the field of polymer materials, and more specifically to a photopolymerizable 3D printed part and its application. Background Technology

[0003] Multiscale porous materials have seen rapid development in various fields due to their advantages such as light weight, high load-bearing capacity to mass ratio, low thermal conductivity, large impact energy dissipation, and good resilience. These materials are widely used in buffer pads, membranes in separation processes, biological scaffolds, electromagnetic wave management, catalysis, and porous electrodes in the electronics and microelectronics industries. In recent years, porous materials prepared based on high-pressure fluid physics foaming technology have many advantages, including small pore size, high pore density, environmental friendliness, and controllable foaming ratio, making it an important method for preparing microporous polymers. However, to achieve a macroscopic three-dimensional structure in these polymer foam materials, molds are usually required, resulting in high mold-making costs and long development cycles. Limited by mold-making and processing technology, it is difficult to construct complex porous structures.

[0004] 3D printing can rapidly construct complex structures, producing materials with controllable shapes and adjustable properties. This technology boasts high automation, high efficiency, and personalized customization. Currently, patent documents CN106493968A and CN110193931A disclose a method for producing foamed products by combining nozzle-based fused deposition modeling (FDM-3D) technology with high-pressure fluid technology. FDM-3D printing uses thermoplastic polymer filaments as raw materials, melting and extruding them through a heated nozzle, and then depositing the molten filaments layer by layer to construct three-dimensional structures. This layer-by-layer deposition and solidification method lacks chemical cross-linking between layers, resulting in weak interlayer bonding and poor interlayer mechanical properties in foamed products, limiting practical applications.

[0005] Besides FDM-3D printing, photopolymer 3D printing is another widely popular 3D printing technology, offering advantages such as short manufacturing cycles and high forming precision. In photopolymer 3D printing, light is applied to the surface of photosensitive resin according to the cross-sectional information of each layer of the part. The resin layer in the irradiated area undergoes a photopolymerization reaction and solidifies, forming a thin layer. The stage moves a certain layer thickness, and new liquid resin fills the gaps, allowing for the next layer to be exposed and cured. Because the previous layer contains unreacted monomers, the resin in the newly cured layer reacts with the resin in the previous layer during curing, forming a chemical cross-linking network that firmly bonds to the previous layer. This process is repeated until the entire part is manufactured. Therefore, the interlayer mechanical properties of photopolymer 3D printing are far superior to those of FDM-3D printing. Furthermore, the printing resolution and surface finish of photopolymer 3D printing are higher than those of FDM-3D printing.

[0006] Generally, photopolymer 3D printing materials are mostly unsaturated resins. Under irradiation with light of a certain wavelength, the photoinitiator absorbs light energy, forming active free radicals or cations, which initiate the polymerization of resins containing multiple functional groups (mainly double bonds and epoxy groups) to form a three-dimensional network polymer. However, due to the high crosslinking density, high glass transition temperature, and small free volume space of the resulting polymer, it is difficult for the high-pressure fluid used for foaming to dissolve into the polymer material to form a foam material. Therefore, it is difficult to use photopolymer 3D printing materials in the production of foam materials. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a photopolymerizable 3D printed part, which is an elastomer obtained through photopolymerizable 3D printing, exhibiting low crosslinking density and a glass transition temperature below 30°C. Furthermore, this invention also provides a method for preparing a multi-scale porous foam material using the aforementioned photopolymerizable 3D printed part, and the multi-scale porous foam material obtained using this method, which possesses excellent tensile properties, foaming properties, resilience, and surface smoothness.

[0008] This invention provides a photopolymerizable 3D printed part, which is an elastomer obtained by photopolymerizable 3D printing, and its crosslinking density is 0.001~10mmol / cm³. 3 Furthermore, its glass transition temperature is below 30℃.

[0009] According to an embodiment of the present invention, the photopolymerizable 3D printed part can be obtained from a photosensitive resin composition, specifically, by curing the photosensitive resin composition using a photopolymerizable 3D printing device. The photosensitive resin composition comprises a high molecular weight oligomer, a monomer, and a photoinitiator, wherein the number average molecular weight of the high molecular weight oligomer is 3500–100000 g / mol.

[0010] According to an embodiment of the present invention, reversible covalent bonds may be optionally introduced into the molecular chain segments of the high molecular weight oligomer. During the high-temperature and high-pressure foaming process of the subsequent preparation of the foamed material, the reversible covalent bonds break, so that the polymer network forms a thermoplastic-like network, which allows the high-pressure fluid to dissolve better into the polymer network, thereby improving the foaming effect.

[0011] According to an embodiment of the present invention, the reversible covalent bond can be a disulfide bond, a hindered urea bond, a boron-oxygen bond, an imine bond, a Diels-Alder bond, a dynamic acylhydrazone bond, an oxime-carbamate bond, or other reversible covalent bonds.

[0012] According to an embodiment of the present invention, the reversible covalent bond can be introduced into the high molecular weight oligomer by reacting a compound having the above-mentioned reversible covalent bond and having an amino or hydroxyl group at the molecular end group with an isocyanate.

[0013] According to an embodiment of the present invention, the number average molecular weight of the high molecular weight oligomer is preferably 6,000 to 80,000 g / mol, more preferably 8,000 to 60,000 g / mol.

[0014] It should be noted that, in this invention, the number-average molecular weight is determined using gel permeation chromatography (GPC).

[0015] According to the technical solution of the present invention, the high molecular weight oligomer can be one or more selected from polyurethane (meth)acrylate oligomers, polyurea (meth)acrylate oligomers, polyurea polyurethane (meth)acrylate, and vinyl-terminated polydimethylsiloxane.

[0016] According to the technical solution of the present invention, the polyurethane (meth)acrylate oligomer can be obtained by first reacting a polyol with an isocyanate, then adding a chain extender for the polyol, and finally attaching an acrylic group or a methacrylate group to the end group. Alternatively, the polyurethane (meth)acrylate oligomer can be obtained by first reacting a polyol with an isocyanate, and then attaching an acrylic group or a methacrylate group to the end group. Or, the polyurethane (meth)acrylate oligomer can be obtained by reacting a high molecular weight polyol with isocyanate methacrylate.

[0017] According to the technical solution of the present invention, the polyurea (meth)acrylate can be obtained by first reacting polyetheramine with isocyanate, then adding a chain extender of polyamine, and then attaching acrylic or methacrylate groups to the end groups. Alternatively, the polyurea (meth)acrylate can be obtained by first reacting polyetheramine with isocyanate, and then attaching acrylic or methacrylate groups to the end groups. Alternatively, the polyurea (meth)acrylate oligomer can be obtained by reacting high molecular weight polyetheramine with isocyanoethyl methacrylate.

[0018] According to the technical solution of the present invention, the polyurea polyurethane (meth)acrylate oligomer refers to an oligomer containing both a polyurethane structure and a polyurea structure. It is obtained by selecting at least one soft-segment polyol and a polyetheramine, reacting them with an isocyanate, then adding at least one polyol or polyamine chain extender, and finally attaching acrylic or methacrylate groups to the end groups.

[0019] According to the technical solution of the present invention, the isocyanate may be at least one selected from diphenylmethane diisocyanate, isocyanoethyl methacrylate, toluene diisocyanate, hydrogenated phenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, terephthalic diisocyanate, trimethyl-1,6-hexanediisocyanate, and naphthalene diisocyanate.

[0020] According to an embodiment of the present invention, the soft segment polyol may be at least one selected from polyether polyols, polyester polyols, polyolefin polyols, and polydimethylsiloxane polyols.

[0021] According to an embodiment of the present invention, the polyether polyol may be at least one selected from polytetrahydrofuran diol, polypropylene glycol, binary or ternary copolymer polyether diol formed from polytetrahydrofuran and propylene oxide and / or ethylene oxide, and polytrimethylene ether diol.

[0022] According to an embodiment of the present invention, the polyester polyol may be at least one selected from polycaprolactone diol and polyethylene adipate diol.

[0023] According to an embodiment of the present invention, the chain extender may be selected from polyols, diamines, alkanolamines, etc.

[0024] According to an embodiment of the present invention, the polyol chain extender may be at least one selected from 1,4-butanediol, trimethylolpropane, glycerol, ethylene glycol, propylene glycol, diethylene glycol, neopentyl glycol, 1,4-cyclohexanediol, and hydrogenated bisphenol A.

[0025] According to an embodiment of the present invention, the diamine chain extender may be at least one selected from 3,5-dimethylthiotoluenediamine and 2,4-diamino-3,5-dimethylthiochlorobenzene.

[0026] According to an embodiment of the present invention, the monomer can be a monofunctional monomer or a low-viscosity polyfunctional monomer. Specifically, it can be at least one selected from cyclotrimethylolpropane methyl acetal acrylate, ethoxyethoxyethyl acrylate, acryloylmorpholine, butyl acrylate, isobornyl acrylate, isobornyl methacrylate, 2-(tert-butylamino)methacrylate, tetrahydrofuran acrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, lauryl acrylate, isooctyl acrylate, tripropylene glycol diacrylate, 3-ethoxytrimethylolpropane triacrylate, trimethylolpropane triethoxy acrylate, ethoxypentaerythritol tetraacrylate, 1,6-hexanediol diacrylate, propoxyneoprene glycol diacrylate, bisphenol A diacrylate, and polyethylene glycol diacrylate.

[0027] According to embodiments of the present invention, the monomer may further include a multifunctional thiol compound, without particular limitation, and may be one or more selected from, for example, trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptopropionic acid), (mercapto)propylmethylsiloxane, and pentaerythritol tetrakis(3-mercaptobutyrate).

[0028] According to an embodiment of the present invention, the photoinitiator is a free radical initiator, which may be selected from at least one of 1-hydroxycyclohexylphenyl ketone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 2,4,6-trimethylbenzoyl-ethoxy-phenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, ethyl 2,4,6-trimethylbenzoylphosphonate, 2,2-dimethoxy-1,2-diphenyl ketone, 2-ethyloctyl-4-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-methyl-1-(4-methylthiophenyl)-2-morpholino-1-propanone, ethyl 2,4,6-trimethylbenzoylphenylphosphine, camphorquinone, and ethyl 4-dimethylaminobenzoate.

[0029] According to an embodiment of the present invention, the weight parts of each component in the photosensitive resin composition are: 1-98 parts of high molecular weight oligomer, 1-98 parts of monomer, and 0.3-15 parts of photoinitiator.

[0030] According to an embodiment of the present invention, the photosensitive resin composition may further contain a matting agent.

[0031] According to an embodiment of the present invention, the matting agent may be at least one selected from Sudan I, Sudan III, BASF Olissa Orange, and fluorescent whitening agent OB.

[0032] According to an embodiment of the present invention, the photosensitive resin composition may further contain a leveling agent.

[0033] According to an embodiment of the present invention, the weight parts of each component in the photosensitive resin composition are: 1-95 parts of high molecular weight oligomer, 1-98 parts of monomer, 0.3-15 parts of photoinitiator, 0.02-0.5 parts of matting agent, and 0.02-3 parts of leveling agent.

[0034] According to an embodiment of the present invention, the photosensitive resin composition is used in photopolymerization 3D printing. Specifically, the photosensitive resin composition is used in stereolithography (SLA), digital projection processing (DLP) printing, desktop liquid crystal (LCD) printing, continuous liquid interface (CLIP) printing, two-photon 3D printers, and multi-material 3D printing.

[0035] According to an embodiment of the present invention, photopolymer 3D printing can be performed under the following conditions: a photosensitive resin composition is placed in a photopolymer 3D printer, 3D printing is performed under optional heating conditions, and then a post-curing treatment is performed to obtain a photopolymer 3D printed part.

[0036] According to an embodiment of the present invention, heating can be performed during the photopolymerization 3D printing process. Heating can reduce the viscosity of the resin composition to facilitate smoother printing. The heating temperature can be between 25°C and 80°C.

[0037] According to an embodiment of the present invention, the post-curing treatment can be performed under a UV lamp during the photopolymerization 3D printing process.

[0038] According to an embodiment of the present invention, the crosslinking density of the photopolymerizable 3D printed part is 0.001–10 mmol / cm². 3 The preferred value is 0.002–6 mmol / cm³. 3 More preferably, it is 0.004–2 mmol / cm². 3 By limiting the crosslinking density of the photopolymer 3D printed part of the present invention to the above-mentioned range, in the subsequent process of preparing foamed material by placing it in a high-pressure container and injecting high-pressure fluid, the low crosslinking density of the elastomer obtained by photopolymer 3D printing allows the high-pressure fluid to fully diffuse and dissolve in the elastomer material, thereby forming a homogeneous polymer / gas system; then, a supersaturated system is obtained by rapidly depressurizing or rapidly heating as the driving force, initiating nucleation of the homogeneous system; under the action of the driving force, the bubble nuclei grow, and as the driving force disappears and the temperature of the polymer matrix decreases, a multi-scale porous material is obtained.

[0039] It should be noted that, in this invention, the crosslinking density is measured using the equilibrium swelling method.

[0040] According to an embodiment of the present invention, the glass transition temperature of the photopolymerizable 3D printed part is below 30°C, preferably below 10°C, and more preferably below 0°C.

[0041] It should be noted that, in this invention, the glass transition temperature is measured using differential scanning calorimetry (DSC) according to the GB / T 19466.2-2004 standard.

[0042] Furthermore, according to an embodiment of the present invention, the Shore hardness of the photocurable 3D printed part of the present invention is 20A to 50D, preferably 30A to 80A, and more preferably 40A to 70A.

[0043] It should be noted that in this invention, Shore hardness is measured according to the American Society for Testing and Materials (ASTM) standard D1415 method.

[0044] Furthermore, according to an embodiment of the present invention, the tensile strength of the photocurable 3D printed part of the present invention is 0.5 to 30 MPa, preferably 2 to 20 MPa, and more preferably 2.5 to 10 MPa.

[0045] Furthermore, according to an embodiment of the present invention, the elongation at break of the photopolymerized 3D printed part of the present invention is 100% to 1200%, preferably 200% to 1000%.

[0046] It should be noted that, in this invention, the tensile strength and elongation at break of the photocured 3D printed parts before foaming are measured according to the American Society for Testing and Materials (ASTM) standard D412.

[0047] Furthermore, according to an embodiment of the present invention, the resilience of the photopolymerizable 3D printed part is 20% to 80%, preferably 30% to 70%.

[0048] It should be noted that in this invention, resilience is measured according to the method of ASTM D2632-2015, the American Society for Testing and Materials standard.

[0049] The present invention also provides a method for preparing multi-scale porous foamed material using the photocurable 3D printed part, which includes the following steps: placing the photocurable 3D printed part into a high-pressure container, injecting gas for high-pressure impregnation, and then rapidly depressurizing to atmospheric pressure to obtain multi-scale porous foamed material.

[0050] According to the present invention, "rapid pressure relief" refers to the pressure exerted on an object being released from high pressure to normal pressure or ambient pressure in a short period of time. The average pressure relief rate of rapid pressure relief is greater than 2.5 MPa / s, for example, greater than 5 MPa / s, greater than 8 MPa / s, or greater than 9 MPa / s.

[0051] It should be noted that in this invention, "multi-scale porous" refers to the formation of micron-scale micropores within the porous structure of the printed part itself after high-pressure fluid impregnation and foaming, which is obtained by photopolymerization 3D printing process.

[0052] According to an embodiment of the present invention, a photopolymerizable 3D printed part is placed in a high-pressure container, and gas is injected. This gas diffuses fully within the printed part under high pressure, forming a homogeneous system. After high-pressure impregnation for a period of time, the pressure is rapidly released to atmospheric pressure, and the product is removed, thus obtaining a multi-scale porous structure. In a preferred embodiment, the product is prepared without a mold.

[0053] According to an embodiment of the present invention, the high-pressure impregnation can be carried out under heating, and the heating temperature is 10 to 180°C higher than the glass transition temperature of the photocurable 3D printed part, preferably 50 to 150°C higher.

[0054] According to an embodiment of the present invention, the high-pressure impregnation can also be carried out without heating. After the photocured 3D printed part is rapidly depressurized, it is immediately removed and placed in hot water at a temperature 20–200°C higher than the glass transition temperature of the photocured 3D printed part. In this way, the 3D printed part can be softened, making it easier for the gas to foam during diffusion.

[0055] According to an embodiment of the present invention, when the high-pressure impregnation is performed without heating, the photocured 3D printed part can be quickly depressurized, immediately removed, and placed in a microwave oven for heating. In this way, after rapid heating in the microwave oven, the 3D printed part softens and can form larger pores.

[0056] According to an embodiment of the present invention, the gas may be at least one selected from carbon dioxide, nitrogen, methane, butane, methanol, ethanol, and water (vapor).

[0057] According to an embodiment of the present invention, after gas is injected into the high-pressure container, the pressure of the high-pressure impregnation can be 1 MPa to 40 MPa, preferably 2 MPa to 30 MPa, and more preferably 3 MPa to 25 MPa.

[0058] According to an embodiment of the present invention, after gas is injected into the high-pressure container, the high-pressure impregnation time can be appropriately selected as needed, which can be 0.5 to 36 hours, preferably 1 to 24 hours, and more preferably 2 to 12 hours.

[0059] The present invention also provides a multi-scale porous foam material obtained by the preparation method of the multi-scale porous foam material.

[0060] According to an embodiment of the present invention, the tensile strength of the multi-scale porous foam material of the present invention is 0.2 to 25 MPa, preferably 1 to 15 MPa, and more preferably 2 to 10 MPa.

[0061] According to an embodiment of the present invention, the elongation at break of the multi-scale porous foam material of the present invention is 250% to 1500%, preferably 300% to 1000%.

[0062] It should be noted that, in this invention, the tensile properties of the foamed sample are measured according to the method of GB / T6344-96.

[0063] According to an embodiment of the present invention, the foaming density of the multi-scale porous foamed material of the present invention is 0.11–0.95 g / cm³. 3 Preferably, the concentration is 0.15–0.75 g / cm³. 3 More preferably, it is 0.2–0.5 g / cm³. 3 .

[0064] It should be noted that, in this invention, the foaming density ρ f The measurement was performed according to ASTM D792-2008, the American Society for Laboratory Materials standard. The formula for calculating the foam density is: ρ f =W1 / (W1+W2-W3)

[0065] Where W1 is the mass of the foamed sample in air, W2 is the weight of the metal ball that immerses the foamed sample in water, and W3 is the mass of the foamed sample in water.

[0066] According to an embodiment of the present invention, the foaming ratio of the multi-scale porous foam material of the present invention is 1.3 to 10, preferably 1.5 to 5.

[0067] It should be noted that in this invention, the foaming ratio is calculated according to the following formula: n = ρ p / ρ f Where n represents the foaming ratio of the printed sample, ρ p ρ represents the density of the sample before foaming. f This indicates the density of the sample after foaming.

[0068] Furthermore, according to embodiments of the present invention, the multi-scale porous foam material of the present invention exhibits good resilience. Specifically, the resilience of the multi-scale porous foam material of the present invention is 25% to 80%, preferably 30% to 70%.

[0069] Beneficial effects

[0070] (1) The photosensitive resin composition containing high molecular weight oligomers provided by this invention forms a polymer with low cross-linking density during the photopolymerization 3D printing process. This provides sufficient free volume space in the structure, allowing high-pressure fluid to diffuse fully within the printed polymer. Then, under rapid pressure reduction, a foam structure is formed. This invention overcomes the problem of traditional photopolymerization 3D printing materials being unable to foam, and enables the design and control of hierarchical structures in foamed materials.

[0071] (2) This invention utilizes photopolymerization 3D printing technology, where there are covalent chemical cross-links between layers, resulting in strong interlayer bonding. The mechanical properties of the product after high-pressure fluid foaming are far superior to those of FDM-3D printed thermoplastic materials. Photopolymerization 3D printing offers high precision and good surface quality. The product after high-pressure fluid foaming only forms a pore structure inside, allowing the surface of the product to maintain high-precision details and smoothness.

[0072] (3) The present invention provides high molecular weight oligomers including polyurethane (meth) acrylate, polyurea (meth) acrylate, etc., which are printed to form an elastomer material. Under the action of high pressure fluid, a multi-scale porous product is formed, which has the characteristics of low density and high resilience.

[0073] (4) The foaming device of the present invention is simple and only requires a sealed container. The photocurable 3D printed part can be placed in the container with or without heating, and gas can be injected into the container. After the gas permeates the printed part for a certain period of time, the sample can be taken out to obtain a multi-scale porous structure product. The equipment is simple, easy to operate, does not require additional chemical foaming agents, and is green and environmentally friendly.

[0074] (5) Although foaming is carried out in a foaming device, the shape of the finished product does not need to be limited by a mold, thereby greatly reducing production costs. Attached Figure Description

[0075] Figure 1 This is a flowchart illustrating the method involved in Embodiment 1 of the present invention;

[0076] Figure 2 These are photographs of the printed parts prepared in Embodiment 1 of the present invention before and after foaming.

[0077] Figure 3 This is a scanning electron microscope image of the cross-section of the printed part prepared in Example 1 of the present invention after foaming;

[0078] Figure 4 This is a scanning electron microscope image of the cross-section of the printed part prepared in Example 4 of the present invention after foaming;

[0079] Figure 5 This is the glass transition temperature measurement curve of the DLP printed part in Embodiment 1 of the present invention;

[0080] Figure 6 This is a photograph of the actual product after foaming of the FDM-printed article in Comparative Example 2 of this invention. Detailed Implementation

[0081] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0082] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0083] Example 1

[0084] Preparation of multi-scale porous foam material 1

[0085] The specific steps for preparing high molecular weight polyurea acrylate oligomer 1 are as follows:

[0086] 300g of polyetheramine (molecular weight 4000g / mol), 15g of hexamethylene diisocyanate, and 10ml of tetrahydrofuran were mixed, and 0.03g of dibutyltin dilaurate was added. The mixture was then heated to 70℃ and reacted for 5h. 3g of chain extender 3,5-dimethylthiotoluene diamine was added, and the reaction was continued for 1h. A small amount of oligomer was then taken out, and the isocyanate group content was measured using the method specified in HG / T2409-1992. When the theoretical value was reached, hydroxypropyl acrylate was added to react with all the isocyanate groups, and the reaction was continued at 70℃ for 3h. The -NCO in the oligomer was tested for complete reaction using infrared spectroscopy. If the characteristic peak of -NCO at wavenumber 2260 disappeared, it indicated that the hexamethylene diisocyanate had completely reacted. The solvent tetrahydrofuran was removed by vacuum distillation to obtain high molecular weight polyurea acrylate oligomer 1 with a number average molecular weight of 35230g / mol.

[0087] Photopolymerization 3D printing: High molecular weight polyurea acrylate oligomer 1 (60g), 4-acryloylmorpholine (40g), and 2,4,6-trimethylbenzoyl-ethoxy-phenylphosphine oxide (2.5g) were stirred evenly at 60℃, and then stirred with a planetary mixer for 10 min to obtain a clear liquid. The obtained liquid was placed in a digital light processing (DLP) 3D printer and 3D printed at 25℃ to produce a frame structure. Post-curing was then performed under a UV lamp to obtain photopolymerization 3D printed part 1. Its performance data are shown in Table 1.

[0088] Foaming molding: The above-mentioned photocured 3D printed part 1 is placed in an autoclave, CO2 gas is injected at a temperature of 60°C, the pressure is adjusted to 10MPa, and the CO2 gas is used to completely immerse the printed part for 1 hour. Then the pressure is released quickly, with an average pressure release rate of 10MPa / s. The product is then removed to obtain multi-scale porous foam material 1, and its performance data are shown in Table 1.

[0089] Example 2

[0090] Preparation of multi-scale porous foam material 2

[0091] The specific steps for preparing high molecular weight polyurethane acrylate oligomer 2 are as follows:

[0092] 200g of polycaprolactone diol (molecular weight 2000g / mol), 33.3g of isophorone diisocyanate, and 20ml of tetrahydrofuran were mixed. 0.05g of dibutyltin dilaurate was added, and the mixture was heated to 50℃ and reacted for 5h. Then, 2g of chain extender glycerol was added, and the reaction was continued for 1h. A small amount of oligomer was then taken out, and the isocyanate group content was measured using the method specified in HG / T2409-1992. When the theoretical value was reached, hydroxypropyl acrylate was added to react with all the isocyanate groups, and the reaction was continued at 70℃ for 3h. The -NCO in the oligomer was tested for complete reaction using infrared spectroscopy. If the characteristic peak of -NCO at wavenumber 2260 disappeared, it indicated that the isophorone diisocyanate had completely reacted. The solvent tetrahydrofuran was removed by vacuum distillation to obtain high molecular weight polyurethane acrylate oligomer 2 with a number average molecular weight of 41870g / mol.

[0093] Photopolymerization 3D printing: High molecular weight polyurethane acrylate oligomer 2 (50g), lauryl acrylate (50g), and ethyl 2,4,6-trimethylbenzoylphenylphosphonate (3g) were stirred evenly at 60℃, and then stirred with a planetary mixer for 5 minutes to obtain a clear liquid. The obtained liquid was placed in a digital light processing (DLP) 3D printer for 3D printing, and a printed part with a frame structure was printed. Then, it was post-cured under a UV lamp to obtain photopolymerization 3D printed part 2. Its performance data are shown in Table 1.

[0094] Foaming molding: The above-mentioned photocured 3D printed part 2 was placed in an autoclave, and CO2 gas was injected at a temperature of 50°C. The pressure was adjusted to 5MPa, and the CO2 gas was used to completely immerse the printed part for 0.5h. Then the pressure was released quickly, with an average pressure release rate of 9.5MPa / s. The product was then removed, and multi-scale porous foamed material 2 was obtained. Its performance data is shown in Table 1.

[0095] Example 3

[0096] Preparation of multi-scale porous foam material 3

[0097] The specific steps for preparing high molecular weight polyurethane acrylate oligomer 3 are as follows:

[0098] 200g of polytrimethylene ether glycol (molecular weight 4000g / mol), 22.2g of isophorone diisocyanate, and 50ml of tetrahydrofuran were mixed. 0.15g of dibutyltin dilaurate was added, and the mixture was heated to 50℃ and reacted for 5h. Then, 4g of chain extender glycerol was added, and the reaction was continued for 1h. A small amount of oligomer was then taken out, and the isocyanate group content was measured using the method specified in HG / T2409-1992. When the theoretical value was reached, hydroxyethyl acrylate was added to react with all the isocyanate groups, and the reaction was continued at 70℃ for 3h. The -NCO in the oligomer was tested for complete reaction using infrared spectroscopy. If the characteristic peak of -NCO at wavenumber 2260 disappeared, it indicated that the isophorone diisocyanate had completely reacted. The solvent tetrahydrofuran was removed by vacuum distillation to obtain high molecular weight polyurethane acrylate oligomer 3 with a number average molecular weight of 57440g / mol.

[0099] Photopolymerization 3D printing: High molecular weight polyurethane acrylate oligomer 3 (80g), acrylamide morpholine (40g), and ethyl 2,4,6-trimethylbenzoylphenylphosphonate (3g) were stirred evenly at 80℃, and then stirred with a planetary mixer for 5 minutes to obtain a clear liquid. The obtained liquid was placed in a stereolithography (SLA) 3D printer and 3D printed at 60℃ to produce a frame structure. Post-curing was then performed under ultraviolet light, followed by heat annealing to obtain photopolymerized 3D printed part 3. Its performance data are shown in Table 1.

[0100] Foaming molding: The above-mentioned photocured 3D printed part 3 is placed in an autoclave, CO2 gas is injected at a temperature of 110°C, the pressure is adjusted to 15MPa, and the CO2 gas is used to completely immerse the printed part for 3 hours. Then the pressure is released quickly, with an average pressure release rate of 12MPa / s. The product is then removed, and a multi-scale porous foamed material 3 is obtained. Its performance data is shown in Table 1.

[0101] Example 4

[0102] Preparation of multi-scale porous foam material 4

[0103] The specific steps for preparing high molecular weight polyurethane acrylate oligomer 4 are as follows:

[0104] 300g of polypropylene glycol (molecular weight 3000g / mol), 24g of terephthalic diisocyanate, and 50ml of tetrahydrofuran were mixed, and 0.05g of dibutyltin dilaurate was added. The mixture was then heated to 50℃ and reacted for 5h. 3.6g of 2-hydroxyethyl disulfide was added, and a small amount of oligomer was taken out. The isocyanate group content was measured using the method specified in HG / T2409-1992. When the theoretical value was reached, ethyl 2-(tert-butylamino)methacrylate was added to react all the isocyanate groups. The reaction was continued at 70℃ for 3h. The -NCO in the oligomer was tested for complete reaction using infrared spectroscopy. If the characteristic peak of -NCO at wavenumber 2260 disappeared, it indicated that the terephthalic diisocyanate had completely reacted. The solvent tetrahydrofuran was removed by vacuum distillation to obtain a high molecular weight polyurethane acrylate oligomer 4 containing two reversible bonds: hindered urea bonds and disulfide bonds, with a number average molecular weight of 6700g / mol.

[0105] Photopolymerization 3D printing: High molecular weight polyurethane acrylate oligomer 4 (80g), acrylamide morpholine (40g), isobornyl acrylate (10g), and ethyl 2,4,6-trimethylbenzoylphenylphosphonate (3g) were stirred evenly at 80℃, and then stirred with a planetary mixer for 5 minutes to obtain a clear liquid. The obtained liquid was placed in a digital light processing (DLP) 3D printer and 3D printed at 45℃ to produce a frame structure. Post-curing was then performed under a UV lamp to obtain photopolymerization 3D printed part 4. Its performance data are shown in Table 1.

[0106] Foaming molding: The above-mentioned photocured 3D printed part 4 is placed in an autoclave, CO2 gas is injected at a temperature of 100°C, the pressure is adjusted to 20MPa, and the CO2 gas is used to completely immerse the printed part for 3 hours. Then the pressure is released quickly, with an average pressure release rate of 12MPa / s. The product is then removed, and multi-scale porous foamed material 4 is obtained. Its performance data is shown in Table 1.

[0107] Example 5

[0108] Preparation of multi-scale porous foam material 5

[0109] Vinyl-terminated polydimethylsiloxane (CAS No.: 68083-19-2, purchased from Sigma-Aldrich) with a molecular weight of 25000 g / mol was selected as the high molecular weight oligomer.

[0110] Photopolymerization 3D printing: Vinyl-terminated polydimethylsiloxane (100g), (mercapto)propylmethylsiloxane (20g), trimethylolpropane tris(3-mercaptopropionate) (15g), and ethyl 2,4,6-trimethylbenzoylphenylphosphonate (3g) were stirred at 50°C until homogeneous, then stirred with a planetary mixer for 5 minutes to obtain a clear liquid. The resulting liquid was placed in a digital light processing (DLP) 3D printer and 3D printed at 60°C to produce a frame structure. Post-curing was then performed under UV light to obtain photopolymerized 3D printed part 5, the performance data of which are shown in Table 1.

[0111] Foaming molding: The above-mentioned photocured 3D printed part 5 is placed in an autoclave, and N2 gas is injected at a temperature of 50°C. The pressure is adjusted to 15MPa, and the N2 gas is used to completely immerse the printed part for 5 hours. Then the pressure is released quickly, with an average pressure release rate of 9MPa / s. The product is then removed, and a multi-scale porous foamed material 5 is obtained. Its performance data is shown in Table 1.

[0112] Example 6

[0113] Preparation of multi-scale porous foam material 6

[0114] The specific steps for preparing high molecular weight polyurethane polyurea acrylate oligomer 6 are as follows:

[0115] 100g of polytetrahydrofuran diol (molecular weight 2000g / mol), 22.2g of isophorone diisocyanate, and 50ml of tetrahydrofuran were mixed. 0.05g of dibutyltin dilaurate was added, and the mixture was heated to 70℃ and reacted for 5 hours. Then, 2.32g of dimethylglyoxime was added, and the reaction was continued for another hour. A small amount of oligomer was then taken out, and the isocyanate group content was measured using the method specified in HG / T2409-1992. When the theoretical value was reached, 2-(tert-butylamino) was added. Ethyl methacrylate was reacted to remove all isocyanate groups, and the reaction was continued at 70°C for 3 hours. The -NCO in the oligomer was tested by infrared spectroscopy to see if it had completely reacted. If the characteristic peak of -NCO at wavenumber 2260 disappeared, it indicated that the isophorone diisocyanate had completely reacted. The solvent tetrahydrofuran was removed by vacuum distillation to obtain a high molecular weight polyurethane polyurea acrylate oligomer 6 containing two reversible bonds: oxime-carbamate bonds and hindered urea bonds, with a number average molecular weight of 32150 g / mol.

[0116] Photopolymerization 3D printing: High molecular weight polyurethane polyurea acrylate oligomer 6 (80g), butyl acrylate (40g), and ethyl 2,4,6-trimethylbenzoylphenylphosphonate (3g) were stirred evenly at 80℃, and then stirred with a planetary mixer for 5 minutes to obtain a clear liquid. The resulting liquid was placed in a DLP-3D printer and 3D printed at 30℃ to produce a frame structure. Post-treatment under ultraviolet light was then performed to obtain photopolymerized 3D printed part 6. Its performance data are shown in Table 1.

[0117] Foaming molding: The above-mentioned photocured 3D printed part 6 was placed in an autoclave, CO2 gas was injected, the pressure was adjusted to 12MPa, and the CO2 gas was used to completely immerse the printed part for 4 hours. Then the pressure was released quickly, with an average pressure release rate of 10MPa / s. The product was taken out and placed in hot water at 100℃ to foam, and multi-scale porous foamed material 6 was obtained. Its performance data are shown in Table 1.

[0118] Comparative Example 1

[0119] Photopolymerization 3D printing: Bisphenol A glycerol dimethacrylate (80g) (number-average molecular weight 512g / mol), isobornyl acrylate (17g), and ethyl 2,4,6-trimethylbenzoylphenylphosphonate (3g) were stirred evenly at 80℃ and then stirred with a planetary mixer for 5 minutes to obtain a clear liquid. The resulting liquid was placed in a digital light processing (DLP) 3D printer and 3D printed at 60℃ to produce a frame structure. Post-curing was then performed under a UV lamp to obtain comparison photopolymerization 3D printed part 1, whose performance data are shown in Table 1.

[0120] Foaming molding: The above-mentioned comparative photocured 3D printed part 1 was placed in an autoclave. CO2 gas was injected at a temperature of 120°C, and the pressure was adjusted to 15MPa. The CO2 gas was allowed to completely immerse the printed part for 3 hours. Then the pressure was released quickly, with an average pressure release rate of 12MPa / s. The product was then removed. Due to the high cross-linking density, CO2 could hardly penetrate into the interior of the molecules and could not foam. It maintained its original shape. Its performance data is shown in Table 1.

[0121] Comparative Example 2

[0122] FDM-3D printing: Thermoplastic polyurethane filament TPU, 85A, purchased from Shenzhen Guanghua Weiye Co., Ltd., was used. An FDM printer was used with a nozzle temperature of 250℃, a printing speed of 60mm / s, and an infill rate of 50% to obtain FDM-3D printed part 1.

[0123] Foaming molding: The above-mentioned FDM-3D printed part 1 was placed in an autoclave, and CO2 gas was injected at a temperature of 80°C. The pressure was adjusted to 12MPa, and the CO2 gas was used to completely immerse the printed part for 2 hours. Then the pressure was released quickly, with an average pressure release rate of 12MPa / s. The product was then removed, and the comparative foamed material was obtained. Due to the use of thermoplastic material for printing, the layers are physically bonded during the printing process, and the interlayer bonding force is weak. During the foaming expansion process, cracks are easily generated, resulting in a decrease in mechanical strength. Its performance data is shown in Table 1.

[0124] The performance tests of this invention are shown below:

[0125] Glass transition temperature: The glass transition temperature of the sample was tested by differential scanning calorimetry (DSC) according to GB / T 19466.2-2004 standard.

[0126] Crosslinking density: The crosslinking density was tested using the equilibrium swelling method.

[0127] Tensile strength / elongation at break of the sample before foaming: The tensile properties and elongation at break of the sample were tested according to ASTM D412, the American Society for Testing and Materials (ASTM) standard.

[0128] Tensile strength / elongation at break of the foamed sample: The tensile properties and elongation at break of the sample were measured according to the method of GB / T6344-96.

[0129] Foaming density ρ f The foaming density ρ of the test sample was determined according to the American Society for Testing and Materials standard ASTM D792-2008. f The formula for calculating foam density is: ρ f =W1 / (W1+W2-W3)

[0130] Where W1 is the mass of the foamed sample in air, W2 is the weight of the metal ball that immerses the foamed sample in water, and W3 is the mass of the foamed sample in water.

[0131] Expansion ratio: Calculated using the formula: n = ρ p / ρ f Test. Where n represents the foaming ratio of the printed sample, ρ p ρ represents the density of the sample before foaming. f This indicates the density of the sample after foaming. A foaming ratio greater than 1 indicates that the sample can foam, and the larger the value, the better the foaming performance; while a foaming ratio of 1 indicates that the sample cannot foam.

[0132] Resilience: Measured according to the method of ASTM D2632-2015, American Society for Testing and Materials.

[0133] Surface smoothness: The appearance of foamed products is observed by the naked eye. Foamed products with virtually no 2mm cracks on the sample surface are rated as ○, and foamed products with 2mm cracks are rated as ×.

[0134] Table 1

[0135]

[0136] As can be seen from the results in Table 1 above, the crosslinking density and glass transition temperature of the photocurable 3D printed elastomers in Examples 1 to 6 fall within the range of the present invention, thus the tensile properties, foaming properties, resilience and surface smoothness of the foamed material obtained after foaming the photocurable 3D printed parts are all excellent.

[0137] Furthermore, a comparison between Example 1 and Example 4 shows that introducing reversible covalent bonds into high molecular weight oligomers enables photopolymerized 3D printed parts to form thermoplastic-like materials, making gas foaming easier. Electron micrographs show the formation of larger spherical foam pores. Figure 4 and Figure 3 (In comparison), this increases the foaming ratio and improves resilience.

[0138] In contrast, the photosensitive resin composition used in Comparative Example 1 contains high molecular weight oligomers whose molecular weight does not fall within the scope of the present invention. As a result, the photocurable 3D printed parts prepared from this photosensitive resin composition have a high glass transition temperature and a high crosslinking density, and cannot foam.

[0139] Comparative Example 2 used FDM-3D printing technology. From Figure 6 It can be seen that there are obvious cracks between the layers of the foamed material. This is because, in the FDM-3D printing process, no chemical cross-linking is formed between the layers, resulting in weak interlayer bonding and a significant decrease in the mechanical properties of the foamed material. In contrast, the foamed material of this invention, due to the use of photopolymerization 3D printing technology, has covalent cross-linking between the layers. During the foaming process, the layers do not expand and break. Therefore, the mechanical properties of the resulting printed parts and the foamed material are far superior to those of the FDM-3D printing process, and the surface finish is also significantly higher.

[0140] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing multi-scale porous foamed materials using photopolymer 3D printed parts, characterized in that, Includes the following steps: The photopolymer 3D printed part is placed in a high-pressure container, gas is injected, and impregnation is carried out under high pressure of 1MPa to 40MPa for 0.5 to 36 hours. Then, the pressure is rapidly released to atmospheric pressure to obtain a multi-scale porous foam material. The impregnation is carried out with or without heating the high-pressure vessel. When heated, the heating temperature is 10 to 180°C higher than the glass transition temperature of the photopolymer 3D printed part; Without heating, quickly depressurize the photocured 3D printed part, remove it immediately, and place it in hot water that is 20 to 200°C higher than the glass transition temperature of the photocured 3D printed part, or heat it in a microwave oven. The photopolymer 3D printed part is an elastomer obtained by photopolymer 3D printing, and the crosslinking density of the photopolymer 3D printed part is 0.001 to 6 mmol / cm³. 3 Furthermore, its glass transition temperature is below 30℃; The photopolymer 3D printed parts have a tensile strength of 0.5–30 MPa, an elongation at break of 100%–1200%, and a resilience of 20%–80%. The photocurable 3D printed part is obtained by photocuring a photosensitive resin composition into a 3D printed part. The photosensitive resin composition comprises, by weight, 1-98 parts of high molecular weight oligomer, 1-98 parts of monomer, and 0.3-15 parts of photoinitiator, wherein the number average molecular weight of the high molecular weight oligomer is 3500-100000 g / mol. The high molecular weight oligomer is selected from at least one of polyurethane (meth) acrylate oligomers, polyurea (meth) acrylate oligomers, polyurea polyurethane (meth) acrylate oligomers, and vinyl-terminated polydimethylsiloxanes. The monomer is selected from one or more of the following: cyclotrimethylolpropane methyl acetal acrylate, ethoxyethoxyethyl acrylate, acrylmorpholine, butyl acrylate, isobornyl acrylate, isobornyl methacrylate, ethyl 2-(tert-butylamino)methacrylate, tetrahydrofuran acrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, lauryl acrylate, isooctyl acrylate, tripropylene glycol diacrylate, trimethylolpropane triethoxyacrylate, pentaerythritol tetraacrylate ethoxylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate propionate, bisphenol A diacrylate, polyethylene glycol diacrylate, trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetra(3-mercaptopropionic acid), and pentaerythritol tetra(3-mercaptobutyric acid).

2. The method according to claim 1, characterized in that, The high molecular weight oligomer may optionally incorporate reversible covalent bonds into its molecular chain segments, wherein the reversible covalent bonds are selected from at least one of disulfide bonds, hindered urea bonds, boron-oxygen bonds, imine bonds, Diels-Alder bonds, dynamic acylhydrazone bonds, and oxime-carbamate bonds.

3. The method according to claim 1, characterized in that, The photoinitiator is selected from at least one of 1-hydroxycyclohexylphenyl ketone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 2,4,6-trimethylbenzoyl-ethoxy-phenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 2,2-dimethoxy-1,2-diphenyl ethyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-methyl-1-(4-methylthiophenyl)-2-morpholino-1-propanone, ethyl 2,4,6-trimethylbenzoylphenylphosphonate, camphorquinone, and ethyl 4-dimethylaminobenzoate.

4. The method according to claim 1, characterized in that, The polyurethane (meth)acrylate oligomer is obtained by first reacting a polyol with an isocyanate, then adding a chain extender to the polyol, and finally attaching acrylate groups or methacrylate groups to the end groups. Alternatively, the polyurethane (meth)acrylate oligomer is obtained by first reacting a polyol with an isocyanate, and then attaching acrylate groups or methacrylate groups to the end groups; Alternatively, the polyurethane (meth)acrylate oligomer is obtained by reacting a high molecular weight polyol with isocyanate (meth)acrylate.

5. The method according to claim 1, characterized in that, The polyurea (meth)acrylate oligomer is obtained by first reacting polyetheramine with isocyanate, then adding a chain extender of polyamine, and then attaching acrylate groups or methacrylate groups to the end groups. Alternatively, the polyurea (meth)acrylate oligomer is obtained by first reacting polyetheramine with isocyanate, and then attaching acrylate groups or (meth)acrylate groups to the end groups; or, the polyurea (meth)acrylate oligomer is obtained by reacting high molecular weight polyetheramine with isocyanate (meth)acrylate.

6. The method according to claim 1, characterized in that, The polyurea polyurethane (meth)acrylate oligomer refers to an oligomer containing the structures of polyurethane and polyurea; it is obtained by selecting at least one of a soft segment polyol and a polyetheramine, reacting it with an isocyanate, then adding at least one of a polyol or a polyamine chain extender, and then attaching acrylate groups or methacrylate groups to the end groups.

7. The method according to any one of claims 4-6, characterized in that, The isocyanate is selected from at least one of diphenylmethane diisocyanate, toluene diisocyanate, hydrogenated phenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, terephthalic diisocyanate, trimethyl-1,6-hexanediisocyanate, and naphthalene diisocyanate.

8. The method according to claim 6, characterized in that, The soft segment polyol is selected from at least one of polyether polyol, polyester polyol, polyolefin polyol, and polydimethylsiloxane polyol.

9. The method according to claim 8, characterized in that, The polyether polyol is selected from at least one of polytetrahydrofuran diol, polypropylene glycol, binary or ternary copolymer polyether diol formed by polytetrahydrofuran with propylene oxide and / or ethylene oxide, and polytrimethylene ether diol.

10. The method according to claim 8, characterized in that, The polyester polyol is selected from at least one of polycaprolactone diol and polyethylene adipate diol.

11. The method according to claim 4, characterized in that, The chain extender of the polyol is selected from at least one of 1,4-butanediol, trimethylolpropane, glycerol, ethylene glycol, propylene glycol, diethylene glycol, neopentyl glycol, 1,4-cyclohexanediol, and hydrogenated bisphenol A.

12. The method according to claim 5, characterized in that, The chain extender of the polyamine is selected from at least one of 3,5-dimethylthiotoluene diamine and 2,4-diamino-3,5-dimethylthiochlorobenzene.

13. The method according to claim 1, characterized in that, The photosensitive resin composition further comprises additive A, wherein additive A is selected from at least one of Sudan I, Sudan III, BASF Oleo Orange, and fluorescent whitening agent OB.

14. The method according to claim 1, characterized in that, The photosensitive resin composition also includes a leveling agent.

15. The method according to claim 14, characterized in that, The weight parts of each component in the photosensitive resin composition are as follows: 1-95 parts of high molecular weight oligomer, 1-98 parts of monomer, 0.3-15 parts of photoinitiator, 0.02-0.5 parts of additive A, and 0.02-3 parts of leveling agent.

16. The method according to claim 1, characterized in that, Photopolymer 3D printing is performed under the following conditions: a photosensitive resin composition is placed in a photopolymer 3D printer, 3D printing is performed under optional heating conditions, and then post-curing is performed to obtain a photopolymer 3D printed part.

17. The method according to claim 16, characterized in that, The heating temperature is 25℃~80℃.

18. The method according to claim 16, characterized in that, In the photopolymer 3D printing process, the post-curing treatment is performed under a UV lamp.

19. The method according to claim 1, characterized in that, The crosslinking density of the photopolymerized 3D printed part is 0.002–6 mmol / cm³. 3 .

20. The method according to claim 1, characterized in that, The glass transition temperature of the photopolymer 3D printed part is below 10°C.

21. The method according to claim 1, characterized in that, The Shore hardness of the photopolymer 3D printed part is 20A to 50D.

22. The method according to claim 1, characterized in that, The tensile strength of the photopolymer 3D printed part is 2-20 MPa.

23. The method according to claim 1, characterized in that, The elongation at break of the photopolymerized 3D printed part is 200% to 1000%.

24. The method according to claim 1, characterized in that, The resilience of the photopolymer 3D printed parts is 30% to 70%.

25. The method according to claim 1, characterized in that, Rapid pressure relief refers to reducing the pressure on an object from high pressure to normal pressure or ambient pressure in a short period of time, with an average pressure relief rate greater than 2.5 MPa / s.

26. The method according to claim 1, characterized in that, The gas is selected from at least one of carbon dioxide, nitrogen, methane, butane, or water vapor.

27. The method according to claim 1, characterized in that, The average pressure relief rate of the rapid pressure relief is greater than 5 MPa / s.

28. A multi-scale porous foam material prepared by the method of any one of claims 1 to 27.

29. The multi-scale porous foamed material according to claim 28, characterized in that, The tensile strength of the multi-scale porous foam material is 0.2–25 MPa, and the elongation at break is 250%–1500%.

30. The multi-scale porous foamed material according to claim 28, characterized in that, The foaming density of the multi-scale porous foam material is 0.11–0.95 g / cm³. 3 , The formula for calculating foam density is: f =W1 / (W1+W2-W3) in, f W1 represents the mass of the foamed sample in air, W2 represents the weight of the metal ball used to immerse the foamed sample in water, and W3 represents the mass of the foamed sample in water.

31. The multi-scale porous foamed material according to any one of claims 28 to 30, characterized in that, The expansion ratio of the multi-scale porous foamed material is 1.3 to 10. The formula for calculating the foaming ratio is: n = p / f , Where n represents the foaming ratio, p This indicates the density of the sample before foaming. f This indicates the density of the sample after foaming.

32. The multi-scale porous foam material according to any one of claims 28 to 30, characterized in that, The resilience of the multi-scale porous foam material is 25% to 80%.

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