Preparation method of polyimide foam composite material with high mechanical strength

Abstract

The invention discloses a preparation method of a polyimide foam composite material with high mechanical strength, which comprises the following steps: (1) adding a mixture of organic acid anhydride and organic amine and fatty alcohol into an organic solvent, dissolving and heating for reaction to obtain a prepolymer solution; (2) adding the functional filler into the prepolymer solution, then supplementing the polar organic solvent, and fully stirring to form a foaming base material; and (3) adding a catalyst, a foaming agent, a surfactant and a cross-linking agent into the foaming base material, uniformly stirring, pouring into a mold for free foaming, heating after foaming, and curing to obtain the high-mechanical-strength polyimide foam composite material. The polar organic solvent and the functional filler are supplemented into the foaming base material, fusion and densification of the foam body are achieved, the hard polyimide foam is obtained, and structure-function integrated preparation of the polyimide foam is achieved through the functional nano filler. Therefore, the high-mechanical-strength polyimide foam composite material is prepared.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer structure-function integrated lightweight composite materials, and specifically relates to a method for preparing a high mechanical strength polyimide foam composite material. Background Art

[0002] Polyimide foam material refers to a kind of soft and hard porous material with polyimide resin as the main component, and containing micro / macro open-cell structures, closed-cell structures or a combination of the two. Compared with traditional foam materials (polyethylene, polypropylene, polyvinyl chloride, polyurethane, polystyrene), polyimide foam material has better thermal stability, radiation resistance, good toughness, intrinsic flame retardancy and reduces the smoke and toxic gases produced by combustion. It also has excellent properties such as good mechanical properties, high temperature resistance, and solvent resistance. Polyimide foam is increasingly used in heat insulation, noise reduction and insulation materials in high-tech fields such as aerospace, ships, high-speed rail, and microelectronics.

[0003] Since the powder method for preparing polyimide foam has strong controllability and stable process, large-sized polyimide foam production can be achieved. This technology is currently one of the most mature production technologies for the preparation of polyimide foam materials. For example, patent CN202310141076.5 uses polyester ammonium salt as a precursor, and obtains polyester ammonium salt precursor copolymer powder after drying, grinding, and sieving. The mold is sealed and placed in a microwave oven, and a high-performance high-temperature resistant heat-insulating polyimide foam is obtained by microwave low heat. Compared with the powder method, isocyanate-based polyimide foam has the advantages of fast foaming process, low cost, and suitability for large-scale production. For example, patents CN201510193907.9, CN201711305372.5, CN202011258887.6, etc. prepared a series of isocyanate-based polyimide foams by a one-step method.

[0004] Polyimide foam has shown great potential in the fields of electronic devices, composite materials, thermal insulation materials, etc. In recent years, with the increasing demand for energy-saving, environmentally friendly and high-efficiency materials, researchers have begun to explore new materials with multiple functions. However, the overall deviation of the mechanical strength of polyimide foam materials makes it difficult to meet the application requirements in the field of high-strength structural functional composite materials. Summary of the invention

[0005] In order to solve the technical problem that the mechanical properties of the current polyimide foam material are poor, the present invention provides a high mechanical strength polyimide foam composite material prepared based on a densification strategy. By adding an organic solvent to the polyimide foaming liquid, the surface tension of the pore structure is increased to achieve the collapse and secondary fusion of the pore structure, thereby obtaining a high mechanical strength polyimide foam material with uniform pore structure size. On this basis, nano-functional bodies can be introduced to design and prepare a multifunctional high mechanical strength polyimide foam material. The specific scheme adopted by the present invention is:

[0006] A method for preparing a high mechanical strength polyimide foam composite material, the preparation method comprising the following steps:

[0007] (1) adding a mixture of an organic acid anhydride and an organic amine and a fatty alcohol into an organic solvent, dissolving and heating to react, thereby obtaining a prepolymer solution;

[0008] (2) adding a functional filler into a prepolymer solution, then adding a polar organic solvent, and stirring thoroughly to form a foaming base material;

[0009] (3) Adding a catalyst, a foaming agent, a surfactant and an isocyanate into the foaming base material, stirring evenly, pouring into a mold for free foaming, and heating and curing after the foaming is completed to obtain a polyimide foam composite material with high mechanical strength.

[0010] Preferably, in step (1), the amount of organic amine added is 3% to 60% of the molar amount of the organic anhydride.

[0011] Preferably, in step (1), the organic acid anhydride is any one of pyromellitic dianhydride, hexafluoro dianhydride, 4,4'-biphenyltetracarboxylic dianhydride or 3,3',4,4'-benzophenonetetracarboxylic dianhydride;

[0012] The monomer of the organic amine is any one of p-phenylenediamine, 2-trifluoromethyl-4,4'-diaminodiphenyl ether or 4,4'-diaminodiphenyl ether and 4,4'-diaminodiphenyl sulfone.

[0013] The polar organic solvent is any one of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone, or a mixed solvent of two of them.

[0014] Preferably, in step (2), the functional filler is any one or more of SiC powder, carbon nanomaterial, and magnetic nanoparticles, the particle size of the functional filler is in the range of 0.5 μm to 50 μm, and the addition amount of the functional filler is 0 wt% to 100 wt% of the mass of the prepolymer solution;

[0015] The carbon nanomaterial is selected from any one of carbon nanotubes or graphene;

[0016] The magnetic nanoparticles are selected from any one of metal Ni powder or Fe3O4 powder.

[0017] Preferably, in step (1), the reaction temperature of the heating reaction is 60°C to 80°C.

[0018] Preferably, in step (3), the foaming agent is water;

[0019] The catalyst is dibutyltin dilaurate or triethanolamine;

[0020] The surfactant is polyethylene glycol;

[0021] The isocyanate is selected from any one or more of toluene diisocyanate, diphenylmethane diisocyanate, polyphenylmethane polyisocyanate, hexamethylene diisocyanate and isophorone diisocyanate.

[0022] Preferably, in step (3), the curing temperature of the post-curing is 160° C. to 220° C., and the curing time is 1 to 2 hours.

[0023] Preferably, the pore size of the high mechanical strength polyimide foam composite material is 100 μm to 500 μm, and the density is 50 kg / m 3 ~300kg / m 3 .

[0024] Preferably, the high mechanical strength polyimide foam composite material is used in the fields of electromagnetic shielding, wave absorption and piezoelectric sensors.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) Low cost and high efficiency: Compared with the polyimide foam prepared by the traditional method, the present invention reduces the viscosity of the foam liquid phase by adding an excessive amount of polar organic solvent when preparing the high mechanical strength polyimide foam composite material, and at the same time increases the surface tension of the foam, thereby causing the foam to collapse and fuse, and realize the densification of the foam. The density and structural support of the foam structure are effectively improved, and it has the advantages of multifunctionality, stable structure, short preparation cycle, excellent thermal stability and flame retardancy.

[0027] (2) Ultra-high mechanical strength: Compared with the polyimide foam prepared by the traditional preparation method, the high mechanical strength polyimide foam composite material prepared by the preparation method of the present invention has typical high mechanical strength characteristics, with a tensile strength of more than 5 MPa and a bending strength of more than 20 MPa. In addition, the functional filler introduced during the preparation process can make the molecular arrangement of the pores more dense and play a certain structural support role, which is beneficial to the structural enhancement and performance improvement of the foam. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is an electron microscope image of the high mechanical strength polyimide foam composite material prepared in Example 1;

[0029] Figure 2 This is an infrared image of the high mechanical strength polyimide foam composite material prepared in Example 2;

[0030] Figure 3 This is an image of the mechanical tensile properties of the high mechanical strength polyimide foam composite material prepared in Example 3;

[0031] Figure 4 This is the piezoelectric performance image of the high mechanical strength polyimide foam composite material prepared in Example 4. DETAILED DESCRIPTION

[0032] A method for preparing a high mechanical strength polyimide foam composite material, the preparation method comprising the following steps:

[0033] (1) adding a mixture of an organic acid anhydride and an organic amine and a fatty alcohol into an organic solvent, dissolving and heating to react, thereby obtaining a prepolymer solution;

[0034] (2) adding a functional filler into a prepolymer solution, then adding a polar organic solvent, and stirring thoroughly to form a foaming base material;

[0035] (3) Adding a catalyst, a foaming agent, a surfactant and an isocyanate into the foaming base material, stirring evenly, pouring into a mold for free foaming, and heating and curing after the foaming is completed to obtain a polyimide foam composite material with high mechanical strength.

[0036] Furthermore, in step (1), the amount of organic amine added is 3% to 60% of the molar amount of the organic anhydride.

[0037] Further, in step (1), the organic acid anhydride is any one of pyromellitic dianhydride, hexafluoro dianhydride, 4,4'-biphenyltetracarboxylic dianhydride or 3,3',4,4'-benzophenonetetracarboxylic dianhydride;

[0038] The monomer of the organic amine is any one of p-phenylenediamine, 2-trifluoromethyl-4,4'-diaminodiphenyl ether or 4,4'-diaminodiphenyl ether and 4,4'-diaminodiphenyl sulfone.

[0039] The polar organic solvent is any one of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone, or a mixed solvent of two of them.

[0040] Furthermore, in step (2), the functional filler is any one or more of SiC powder, carbon nanomaterials, and magnetic nanoparticles, the particle size of the functional filler is in the range of 0.5 μm to 50 μm, and the amount of the functional filler added is 0 wt% to 100 wt% of the mass of the prepolymer solution;

[0041] The carbon nanomaterial is selected from any one of carbon nanotubes or graphene;

[0042] The magnetic nanoparticles are selected from any one of metal Ni powder or Fe3O4 powder.

[0043] Furthermore, in step (1), the reaction temperature of the heating reaction is 70°C to 80°C.

[0044] Further, in step (3), the foaming agent is water;

[0045] The catalyst is dibutyltin dilaurate or triethanolamine;

[0046] The surfactant is polyethylene glycol;

[0047] The isocyanate is selected from any one or more of toluene diisocyanate, diphenylmethane diisocyanate, polyphenylmethane polyisocyanate, hexamethylene diisocyanate and isophorone diisocyanate.

[0048] Furthermore, in step (3), the curing temperature of the post-curing is 160° C. to 220° C., and the curing time is 1 to 2 hours.

[0049] Furthermore, the pore size of the high mechanical strength polyimide foam composite material is 100 μm to 500 μm, and the density is 50 kg / m 3 ~300kg / m 3 .

[0050] Furthermore, the high mechanical strength polyimide foam composite material is applied in the fields of electromagnetic shielding, wave absorption and piezoelectric sensors.

[0051] The technical solutions of the present invention are described below through the following embodiments.

[0052] Example 1

[0053] A mixture of 9.0 g of pyromellitic anhydride, 20 mL of N, N-dimethylacetamide and 5.8 mL of methanol was added to the reactor, heated to 60 ° C and fully dissolved and reacted. Then 2.9 g of p-phenylenediamine was added, and after fully reacting for 2 hours, 4.25 g of SiC powder was added, followed by 2 mL of N, N-dimethylformamide, and stirred evenly to form a foaming base material. 1.2 g of water, 0.25 g of dibutyltin dilaurate, and 0.5 g of triethanolamine were added to the foaming base material in sequence to fully dissolve, and then 1.15 g of surfactant polyethylene glycol (PEG) and silicone surfactant were added, and 14 g of polymethylene polyphenyl polyisocyanate (PAPI) was added and quickly stirred evenly, and then poured into the mold for free foaming. After the foaming is completed, the foam is heated at 160 ° C in an oven for 2 hours and then cured to obtain a hard polyimide foam material (i.e., a high mechanical strength polyimide foam composite material).

[0054] Figure 1 This is an electron microscope image of the high mechanical strength polyimide foam prepared in this example. Figure 1 It can be found that the density of the prepared polyimide foam is 160kg / m 3 The pore size is mainly between 50μm and 500μm. At the same time, it can be found that the prepared foam has an ultra-thick cell wall structure, which can effectively support the mechanical strength of the foam.

[0055] Example 2

[0056] Add 7.6g of 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride, 20mL of N,N-dimethylacetamide and 4.5mL of methanol to the reactor, heat to 70℃ and fully dissolve and react. Then add 1.3g of 4,4'-diaminodiphenyl ether, fully react for 2h, add 10g of SiC powder, then add 3mL of N,N-dimethylacetamide, stir evenly to form a foaming base. Add 1.1g of water as a foaming agent, 0.25g of dibutyltin dilaurate as a catalyst and 0.5g of triethanolamine to the foaming base in sequence and fully dissolve, then add 1.25g each of the surfactant polyethylene glycol (PEG) and the silicone surfactant, and then add 17g of polymethylene polyphenyl polyisocyanate (PAPI) and quickly stir evenly, then pour into the mold for free foaming. After the foaming is completed, the foam is heated in an oven at 220° C. for 2 hours and then cured to obtain a hard polyimide foam material (ie, a polyimide foam composite material with high mechanical strength).

[0057] In order to prove that the polyimide foam in this example has completed imidization, the hard polyimide foam prepared in this example is characterized by FT-IR infrared images. Figure 2This is the FT-IR infrared image of the rigid polyimide foam prepared in this example. Figure 2 Medium: 1700-1800cm -1 The absorption peak in this region is usually related to the stretching vibration of the carbonyl C=O. In the polyimide structure, the carbonyl group on the imide ring will produce characteristic absorption in this region, thus indicating the presence of polyimide.

[0058] Example 3

[0059] Add 8.2g of 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride, 20mL of N,N-dimethylformamide and 5.3mL of methanol to the reactor, heat to 80℃ and fully dissolve and react. Then add 0.5g of 4,4'-diaminodiphenyl ether, fully react for 2h, add 5g of SiC powder and 2g of metal Ni powder, then add 3mL of N,N-dimethylacetamide, stir evenly to form a foaming base. Add 1.3g of water as a foaming agent, 0.25g of dibutyltin dilaurate as a catalyst and 0.5g of triethanolamine to the foaming base in sequence and fully dissolve, then add 1.25g each of the surfactant polyethylene glycol (PEG) and the silicone surfactant, and then add 16g of polymethylene polyphenyl polyisocyanate (PAPI) and quickly stir evenly before pouring into the mold for foaming. After the foaming is completed, the foam is heated in an oven at 200° C. for 2 hours and then cured to obtain a hard polyimide foam material (i.e., a high mechanical strength polyimide foam composite material). The mechanical properties of the high mechanical strength polyimide foam composite material prepared in this embodiment are verified by mechanical tests. Figure 3 The figure shows the mechanical tensile image of the rigid polyimide foam prepared in this example. It can be found that the compression strength of the prepared composite material reaches 5.3MPa, and the bending strength is greater than 20MPa, showing high mechanical strength, which can meet the application requirements of high-performance structural composite materials.

[0060] Example 4

[0061] Add 8.6g hexafluorodianhydride and 20mL N,N-dimethylformamide and 4.3mL ethanol mixed solution to the reactor, heat to 80℃ and fully dissolve and react. Then add 2.0g 4,4'-diaminodiphenyl ether, fully react for 2h, add 20g SiC powder, then add 5mL N,N-dimethylformamide, stir evenly to form a foaming base. Add 1.1g water as a foaming agent, 0.25g dibutyltin dilaurate as a catalyst and 0.5g triethanolamine to the foaming base in sequence and fully dissolve, then add 1.25g each of the surfactant polyethylene glycol (PEG) and the silicone surfactant, then add 3g hexamethylene diisocyanate and 14g polymethylene polyphenyl polyisocyanate (PAPI), stir quickly and evenly, then pour into the mold for free foaming. After the foaming is completed, the foam is heated in an oven at 180° C. for 2 hours and then cured to obtain a hard polyimide foam material (ie, a polyimide foam composite material with high mechanical strength).

[0062] The piezoelectric response characteristics of the high mechanical strength polyimide foam composite material prepared in this embodiment are characterized by the piezoelectric response characteristics. Figure 4 As shown, in Figure 4 The piezoelectric characteristic curve shows obvious periodic fluctuations, which means that when the material is subjected to periodic external excitation (such as pressure, vibration, etc.), it will produce a periodic piezoelectric response output voltage. Each complete fluctuation cycle corresponds to the piezoelectric effect process of the material under external excitation. There are multiple voltage peaks on the curve, which represent the maximum output voltage generated by the material under each excitation. The size of the peak reflects the strength of the piezoelectric response of the material. The higher the peak value, the stronger the piezoelectric effect generated by the material under the excitation condition. The peak value of the curve in the figure can reach 3V, which means that the obtained hard polyimide foam material exhibits excellent piezoelectric properties; and from Figure 4 It can be seen that within a certain time range, the fluctuation of the curve is relatively stable, and the periodicity and peak value are relatively consistent, indicating that the piezoelectric response of the material has good repeatability and stability, and can generate piezoelectric output relatively stably under the same excitation conditions. In summary, the high mechanical strength polyimide foam composite material prepared in this embodiment exhibits excellent piezoelectric properties, and under the action of stress of a certain frequency, it can generate a stable voltage output, which can be used to design a structure-sensing function integrated composite material. Therefore, the high mechanical strength polyimide foam composite material prepared in this application is used for service performance monitoring of structural parts.

[0063] The above embodiments are used to help understand the method and core concept of the present invention, and are not intended to limit the content of the invention. Without departing from the principles of the present invention, local improvements and modifications to the present invention also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a high mechanical strength polyimide foam composite material, characterized in that: The preparation method comprises the following steps: (1) adding a mixture of an organic acid anhydride and an organic amine and a fatty alcohol into an organic solvent, dissolving and heating to react, thereby obtaining a prepolymer solution; (2) adding a functional filler into a prepolymer solution, then adding a polar organic solvent, and stirring thoroughly to form a foaming base material; (3) Adding a catalyst, a foaming agent, a surfactant and an isocyanate into the foaming base material, stirring evenly, pouring into a mold for free foaming, and heating and curing after the foaming is completed to obtain a polyimide foam composite material with high mechanical strength.

2. The method for preparing a high mechanical strength polyimide foam composite material according to claim 1, characterized in that: In step (1), the amount of organic amine added is 3% to 60% of the molar amount of the organic acid anhydride.

3. The method for preparing a high mechanical strength polyimide foam composite material according to claim 1, characterized in that: In step (1), the organic acid anhydride is any one of pyromellitic dianhydride, hexafluoro dianhydride, 4,4'-biphenyltetracarboxylic dianhydride or 3,3',4,4'-benzophenonetetracarboxylic dianhydride; The monomer of the organic amine is any one of p-phenylenediamine, 2-trifluoromethyl-4,4'-diaminodiphenyl ether or 4,4'-diaminodiphenyl ether and 4,4'-diaminodiphenyl sulfone. The polar organic solvent is any one of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone, or a mixed solvent of two of them.

4. The method for preparing a high mechanical strength polyimide foam composite material according to claim 1, characterized in that: In step (2), the functional filler is any one or more of SiC powder, carbon nanomaterials, and magnetic nanoparticles, the particle size of the functional filler is in the range of 0.5 μm to 50 μm, and the amount of the functional filler added is 0 wt% to 100 wt% of the mass of the prepolymer solution; The carbon nanomaterial is selected from any one of carbon nanotubes or graphene; The magnetic nanoparticles are selected from any one of metal Ni powder or Fe3O4 powder.

5. The method for preparing a high mechanical strength polyimide foam composite material according to claim 1, characterized in that: In step (1), the reaction temperature of the heating reaction is 60°C to 80°C.

6. The method for preparing a high mechanical strength polyimide foam composite material according to claim 1, characterized in that: In step (3), the foaming agent is water; The catalyst is dibutyltin dilaurate or triethanolamine; The surfactant is polyethylene glycol; The isocyanate is selected from any one or more of toluene diisocyanate, diphenylmethane diisocyanate, polyphenylmethane polyisocyanate, hexamethylene diisocyanate and isophorone diisocyanate.

7. The method for preparing a high mechanical strength polyimide foam composite material according to claim 1, characterized in that: In step (3), the curing temperature of the post-curing is 160° C. to 220° C., and the curing time is 1 to 2 hours.

8. The high mechanical strength polyimide foam composite material prepared by the method for preparing a high mechanical strength polyimide foam composite material according to any one of claims 1 to 8, characterized in that: The high mechanical strength polyimide foam composite material has a pore size of 100 μm to 500 μm and a density of 50 kg / m 3 ~300kg / m 3 .

9. The high mechanical strength polyimide foam composite material prepared by the method for preparing a high mechanical strength polyimide foam composite material according to any one of claims 1 to 8, characterized in that: The high mechanical strength polyimide foam composite material is applied to the fields of electromagnetic shielding, wave absorption and piezoelectric sensors.

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