A composition for thermoplastic prepreg and use thereof, a thermoplastic prepreg, a structural member for a low-flying aircraft

Abstract

The application discloses a composition for thermoplastic prepreg and application thereof, a thermoplastic prepreg and a structural member for low-altitude aircraft, and relates to the field of advanced composite materials.The composition comprises: a methyl methacrylate prepolymer, the viscosity of the methyl methacrylate prepolymer being 80 Pa.s to 120 Pa.s; initiator microcapsules, the average particle size of the initiator microcapsules being 100 microns to 200 microns, and the shell material of the initiator microcapsules comprising gelatin, sodium hexametaphosphate and glutaraldehyde.Compared with the prior art, the application mainly selects a specific methyl methacrylate prepolymer and a specific initiator microcapsule for collocation and use, and controls the proportion of the use amount of the two, so that a prepreg system capable of long-term storage at room temperature and completing curing and forming under low-temperature and low-pressure conditions is realized, the prepreg system has good paving performance and composite material forming adaptability, and the manufacturing requirements in the fields of low-altitude aircraft composite materials and the like are met.

Description

Technical Field

[0001] This invention relates to the field of advanced composite materials, and more particularly to a composition for thermoplastic prepregs and its applications, thermoplastic prepregs, and structural components for low-altitude aircraft. Background Technology

[0002] With the rapid development of the low-altitude economy, the low-altitude aircraft industry, represented by unmanned aerial vehicles (UAVs), electric vertical take-off and landing (eVTOL) aircraft, and flying cars, is rapidly emerging.

[0003] To improve flight efficiency, increase range, and enhance payload capacity, low-altitude aircraft extensively utilize carbon fiber reinforced composite materials in the manufacture of key structural components such as wings, fuselages, rotors, skins, and load-bearing frames. Currently, composite materials typically account for more than 50% of the structural mass of advanced low-altitude aircraft, and in some models, even exceed 70%.

[0004] Currently, composite material structures for low-altitude aircraft are mainly manufactured using thermosetting prepreg processes. Although thermosetting prepregs have excellent mechanical properties, their resin systems tend to continuously cross-link during storage, typically requiring frozen storage and transportation below -18°C. This not only increases manufacturing and logistics costs but also limits shelf life, hindering the large-scale industrial production of low-altitude aircraft.

[0005] Furthermore, thermosetting prepregs generally require curing in an autoclave at temperatures of 120–180°C and a molding pressure of 0.5–0.7 MPa or higher. The high investment and energy consumption of autoclave equipment hinders the low-cost manufacturing of large composite material structural components for low-altitude aircraft.

[0006] In recent years, thermoplastic composites have attracted attention in order to reduce production costs. However, traditional thermoplastic resins (such as polyetheretherketone (PEEK), polyetherketoneketone (PEKK), and polyphenylene sulfide (PPS)) have high melt viscosity and require high-temperature processing above 300°C, which requires sophisticated equipment and makes fiber impregnation difficult. At the same time, traditional thermoplastic prepregs are rigid at room temperature and have poor lay-up properties, making them difficult to meet the manufacturing requirements of complex curved surface structures for low-altitude aircraft.

[0007] In summary, there is an urgent need for a prepreg system that combines room temperature storage, low temperature and low pressure curing, and good lay-up properties to meet the low-cost and large-scale manufacturing needs of composite material structures for low-altitude aircraft. Summary of the Invention

[0008] To address the aforementioned problems, this invention provides a composition for thermoplastic prepregs and its applications, thermoplastic prepregs, and structural components for low-altitude aircraft.

[0009] In a first aspect, the present invention provides a composition for thermoplastic prepregs, comprising:

[0010] A methyl methacrylate prepolymer, wherein the viscosity of the methyl methacrylate prepolymer is 80 Pa·s to 120 Pa·s;

[0011] Initiator microcapsules, wherein the average particle size of the initiator microcapsules is 100-200 micrometers, and the shell material of the initiator microcapsules includes gelatin, sodium hexametaphosphate and glutaraldehyde;

[0012] The weight ratio of the methyl methacrylate prepolymer to the initiator microcapsules is ≥20:1.

[0013] Furthermore, the weight ratio of the methyl methacrylate prepolymer to the initiator microcapsule is (20-30):1.

[0014] Further, the weight ratio of the gelatin, the sodium hexametaphosphate, and the glutaraldehyde is (2.2-2.7):(1.5-1.8):(2.0-2.3).

[0015] Furthermore, the core material of the initiator microcapsule is an initiator, which includes benzoyl peroxide, and the weight ratio of the initiator to the gelatin is (1-2):(1-2).

[0016] Furthermore, the preparation of the methyl methacrylate prepolymer includes the following process:

[0017] Methyl methacrylate and a photoinitiator were mixed at a weight ratio of 100:(1-3), and then subjected to a light intensity of 10 mW / cm². 2 -20mW / cm 2 The methyl methacrylate prepolymer was obtained by irradiating it with ultraviolet light for 1.5-2.5 hours at a light distance of 10-20 cm.

[0018] The photoinitiator includes 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.

[0019] Furthermore, the preparation of the initiator microcapsules includes the following process:

[0020] Gelatin, sodium hexametaphosphate, and water were stirred and mixed to obtain a compound coagulation system;

[0021] Add 20wt%-30wt% of an initiator core material aqueous solution to the compound coagulation system and stir to emulsify. After emulsification, adjust the pH of the system to 4.5-5.0 and add glutaraldehyde to continue stirring for cross-linking and curing. Filter, wash and dry to obtain the initiator microcapsules.

[0022] Secondly, based on the same inventive concept, the present invention provides the application of the thermoplastic prepreg composition described in the first aspect in the preparation of thermoplastic prepregs and structural components for low-altitude aircraft.

[0023] Thirdly, based on the same inventive concept, the present invention provides a thermoplastic prepreg comprising:

[0024] The thermoplastic prepreg composition described in the first aspect; and

[0025] The reinforcing material includes at least one of carbon fiber, glass fiber, and aramid fiber.

[0026] Furthermore, the curing temperature of the thermoplastic prepreg is 80℃-120℃;

[0027] And / or, the curing pressure of the thermoplastic prepreg is 0.1 MPa-0.5 MPa;

[0028] And / or, the storage temperature of the thermoplastic prepreg is 20℃-30℃.

[0029] Fourthly, based on the same inventive concept, the present invention provides a structural component for a low-altitude aircraft comprising the thermoplastic prepreg composition described in the first aspect or the thermoplastic prepreg described in the second aspect.

[0030] The technical solutions provided in the embodiments of the present invention have at least the following advantages compared with the prior art:

[0031] This invention provides a composition for thermoplastic prepregs and its applications, thermoplastic prepregs, and structural components for low-altitude aircraft. Compared to existing technologies, this invention mainly uses a specific methyl methacrylate prepolymer and a specific initiator microcapsule in combination, controlling the ratio of their amounts. By using "B-stage (partially polymerized) methyl methacrylate prepolymer of suitable viscosity (80-120 Pa·s, stable at room temperature + moderate coverage)" + "gelatin / sodium hexametaphosphate / glutaraldehyde shell microencapsulation initiator (particle size 100-200 μm, room temperature isolation, molding and cell wall breaking release)" + "≥20:1 dosage ratio (matching residual double bonds, maintaining toughness)", the ternary synergy achieves a prepreg system that can be stored at room temperature for a long time and can be cured and molded under low temperature and low pressure conditions, while having good coverage performance and composite material molding adaptability, thereby meeting the manufacturing needs of low-altitude aircraft composite materials and other fields. Attached Figure Description

[0032] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a sample image showing the storage and curing of a mixture of methyl methacrylate prepolymer and initiator microcapsules in a thermoplastic prepreg composition provided in an embodiment of the present invention; wherein, Figure 1 In the image: (a) is a picture of a stored sample, and (b) is a picture of a cured sample. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Unless otherwise specified, all raw materials, reagents, instruments, and equipment used in this invention can be purchased commercially or prepared using existing methods. Furthermore, unless otherwise specified or detailed, the steps and parameters involved can be performed according to the publicly available thermoplastic prepreg preparation process steps and parameters, or directly using existing equipment according to the instruction manual; these will not be elaborated upon further in this invention document.

[0037] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed according to national standards. If no corresponding national standard exists, then generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0038] Example 1

[0039] This example provides a composition for thermoplastic prepregs, comprising:

[0040] The preparation of a methyl methacrylate prepolymer includes: mixing methyl methacrylate and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide photoinitiator in a weight ratio of 100:1.5, followed by stirring and mixing under light intensity of 15 mW / cm². 2 The methyl methacrylate prepolymer was obtained by irradiating it with ultraviolet light at a wavelength of 365 nm for 2 hours at a light irradiation distance of 15 cm. The viscosity of the methyl methacrylate prepolymer at 25 °C was measured to be 100 Pa·s.

[0041] The preparation of initiator microcapsules includes: 1) mixing a 5 wt% gelatin aqueous solution containing 2.5 g of gelatin and a sodium hexametaphosphate aqueous solution containing 1.6 g of sodium hexametaphosphate to obtain a complex polymer system; 2) adding a 25 wt% benzoyl peroxide solution (diethyl phthalate as solvent) to the complex polymer system and stirring and emulsifying at a stirring speed of 500 rpm for 30 min at a temperature of 45 °C, then adjusting the pH to 4.8 and adding 2.1 g of glutaraldehyde and continuing stirring for 8 h to complete crosslinking and curing; filtering, washing, and drying at room temperature for 24 h to obtain initiator microcapsules; the average particle size of the initiator microcapsules was determined to be 150 micrometers;

[0042] The weight ratio of the methyl methacrylate prepolymer to the initiator microcapsules is 20:1.

[0043] Example 2

[0044] This example provides a composition for thermoplastic prepregs, which differs from Example 1 only in that:

[0045] (1) The viscosity of the methyl methacrylate prepolymer is 80 Pa·s;

[0046] (2) The average particle size of the initiator microcapsules is 100 micrometers.

[0047] Example 3

[0048] This example provides a composition for thermoplastic prepregs, which differs from Example 1 only in that:

[0049] (1) The viscosity of the methyl methacrylate prepolymer is 120 Pa·s;

[0050] (2) The average particle size of the initiator microcapsules is 200 micrometers.

[0051] Example 4

[0052] This example provides a composition for thermoplastic prepregs, which differs from Example 1 only in that:

[0053] (1) The weight ratio of the methyl methacrylate prepolymer to the initiator microcapsule is 28:1.

[0054] Comparative Example 1

[0055] This example provides a composition for thermoplastic prepregs, which differs from Example 1 only in that:

[0056] (1) The initiator was not microencapsulated.

[0057] Comparative Example 2

[0058] This example provides a composition for thermoplastic prepregs, which differs from Example 1 only in that:

[0059] (1) The viscosity of the methyl methacrylate prepolymer is 180 Pa·s.

[0060] Comparative Example 3

[0061] This example provides a composition for thermoplastic prepregs, which differs from Example 1 only in that:

[0062] (1) The average particle size of the initiator microcapsules is 240 micrometers.

[0063] Comparative Example 4

[0064] This example provides a composition for thermoplastic prepregs, which differs from Example 1 only in that:

[0065] (1) The gelatin in the initiator microcapsule shell material was changed to chitosan.

[0066] Comparative Example 5

[0067] This example provides a composition for thermoplastic prepregs, which differs from Example 1 only in that:

[0068] (1) The weight ratio of the methyl methacrylate prepolymer and the initiator microcapsules is adjusted to 10:1.

[0069] Test Example 1

[0070] In this example, the thermoplastic prepreg compositions obtained in Examples 1-4 and Comparative Examples 1-5 were subjected to a 10-day storage performance test at 60°C. The increase rate of storage viscosity (%) was calculated based on the viscosity before and after the storage test. The test results are shown in Table 1.

[0071] Table 1

[0072] Test sample Increase in storage viscosity (%) Example 1 24.7 Example 2 29.6 Example 3 32.2 Example 4 22.9 Comparative Example 1 120.0 Comparative Example 2 48.3 Comparative Example 3 55.8 Comparative Example 4 72.4 Comparative Example 5 88.9

[0073] As shown in Table 1, after 10 days of storage at 60°C, the viscosity increase rate of Examples 1-4 was 22.9%–32.2%, all lower than the 48.3%–120.0% of Comparative Examples 1-5, indicating that the thermoplastic prepreg composition of the present invention has good storage stability. Among them, Example 4 had the lowest viscosity increase rate, indicating that under the test conditions, adjusting the weight ratio of methyl methacrylate prepolymer to initiator microcapsules to 28:1 can further reduce the viscosity increase during storage.

[0074] Compared to Example 1, Comparative Example 1, which did not use initiator microcapsules, showed a 120.0% increase in storage viscosity, indicating that microencapsulation effectively isolates the initiator and inhibits premature reactions during storage. In Comparative Example 2, the prepolymer viscosity increased to 180 Pa·s, and in Comparative Example 3, the microcapsule particle size increased to 240 micrometers, both showing a significant decrease in storage stability, indicating that the prepolymer viscosity and microcapsule particle size should be controlled within the range defined in this invention. In Comparative Example 4, replacing the gelatin shell with chitosan increased the storage viscosity by 72.4%, indicating that the shell system composed of gelatin, sodium hexametaphosphate, and glutaraldehyde is more conducive to the stable encapsulation of the initiator. In Comparative Example 5, the weight ratio of prepolymer to microcapsules decreased to 10:1, and the relative amount of microcapsules increased, resulting in an 88.9% increase in storage viscosity, indicating that controlling the weight ratio of the two to be no less than 20:1 is beneficial to improving the storage stability of the composition.

[0075] Test Example 2

[0076] In this example, the thermoplastic prepreg composition obtained in Example 1 and Comparative Examples 1-5 is further combined with T700 carbon fiber cloth reinforcement to prepare a thermoplastic prepreg: After the thermoplastic prepreg composition is mixed evenly, a thermoplastic prepreg with a resin content of 35 wt% is obtained by impregnation; the thermoplastic prepreg is heated at a pressure of 0.5 MPa and a temperature of 80°C for 2 hours, and the resin is cured to obtain a composite material. The mechanical property test results are shown in Table 2.

[0077] Table 2

[0078] Test sample Tensile strength (MPa) Example 1 738.6 Comparative Example 1 481.3 Comparative Example 2 593.7 Comparative Example 3 628.4 Comparative Example 4 546.8 Comparative Example 5 661.5

[0079] As shown in Table 2, under the conditions of pressure of 0.5 MPa, temperature of 80°C and heating for 2 hours, the tensile strength of the composite material obtained in Example 1 is 738.6 MPa, which is significantly higher than that of Comparative Examples 1-5 (481.3 MPa to 661.5 MPa). This indicates that the thermoplastic prepreg composition of the present invention can effectively improve the tensile properties of the composite material.

[0080] Compared to Example 1, Comparative Example 1 did not use initiator microcapsules, which made the initiator prone to uneven dispersion or premature reaction, resulting in a significant decrease in the tensile strength of the composite material. In Comparative Example 2, the viscosity of the methyl methacrylate prepolymer increased to 180 Pa·s, reducing fiber wettability and affecting the interfacial bonding between the resin and the reinforcement. In Comparative Example 3, the microcapsule particle size increased to 240 micrometers, which easily led to uneven dispersion of the initiator and uneven curing. Comparative Example 4 used chitosan instead of gelatin shell material, which was not conducive to the stable encapsulation of the initiator and its effective release during molding. In Comparative Example 5, the weight ratio of prepolymer to microcapsules decreased to 10:1, and the relatively high amount of microcapsules may lead to excessively rapid curing reaction and decreased system toughness. All of the above factors resulted in the tensile strength of the composite material being lower than that of Example 1.

[0081] In summary, the embodiments of the present invention provide a composition for thermoplastic prepregs and its application, thermoplastic prepregs, and structural components for low-altitude aircraft. Compared with the prior art, the present invention mainly achieves a prepreg system that can be stored at room temperature for a long time and cured under low temperature and low pressure conditions by selecting specific methyl methacrylate prepolymers and specific initiator microcapsules and controlling the ratio of the two, thereby meeting the manufacturing needs of low-altitude aircraft composite materials and other fields.

[0082] Various embodiments of the present invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible subranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the range referred to.

[0083] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A composition for thermoplastic prepregs, characterized in that, include: A methyl methacrylate prepolymer, wherein the viscosity of the methyl methacrylate prepolymer is 80 Pa·s to 120 Pa·s; Initiator microcapsules, wherein the average particle size of the initiator microcapsules is 100-200 micrometers, and the shell material of the initiator microcapsules includes gelatin, sodium hexametaphosphate and glutaraldehyde; The weight ratio of the methyl methacrylate prepolymer to the initiator microcapsules is ≥20:

1.

2. The composition for thermoplastic prepregs according to claim 1, characterized in that, The weight ratio of the methyl methacrylate prepolymer to the initiator microcapsule is (20-30):

1.

3. The composition for thermoplastic prepregs according to claim 1, characterized in that, The weight ratio of the gelatin, the sodium hexametaphosphate, and the glutaraldehyde is (2.2-2.7):(1.5-1.8):(2.0-2.3).

4. The composition for thermoplastic prepregs according to claim 1, characterized in that, The core material of the initiator microcapsule is an initiator, which includes benzoyl peroxide, and the weight ratio of the initiator to the gelatin is (1-2):(1-2).

5. The composition for thermoplastic prepregs according to claim 1, characterized in that, The preparation of the methyl methacrylate prepolymer includes the following process: Methyl methacrylate and a photoinitiator were mixed at a weight ratio of 100:(1-3), and then subjected to a light intensity of 10 mW / cm². 2 -20mW / cm 2 The methyl methacrylate prepolymer was obtained by irradiating it with ultraviolet light for 1.5-2.5 hours at a light distance of 10-20 cm. The photoinitiator includes 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.

6. The composition for thermoplastic prepregs according to claim 1, characterized in that, The preparation of the initiator microcapsules includes the following process: Gelatin, sodium hexametaphosphate, and water were stirred and mixed to obtain a compound coagulation system; Add 20wt%-30wt% of an initiator core material aqueous solution to the compound coagulation system and stir to emulsify. After emulsification, adjust the pH of the system to 4.5-5.0 and add glutaraldehyde to continue stirring for cross-linking and curing. Filter, wash and dry to obtain the initiator microcapsules.

7. The use of a thermoplastic prepreg composition in the preparation of thermoplastic prepregs and structural components for low-altitude aircraft.

8. A thermoplastic prepreg, characterized in that, include: The thermoplastic prepreg composition according to any one of claims 1-6; as well as The reinforcing material includes at least one of carbon fiber, glass fiber, and aramid fiber.

9. The thermoplastic prepreg according to claim 8, characterized in that, The curing temperature of the thermoplastic prepreg is 80℃-120℃; And / or, the curing pressure of the thermoplastic prepreg is 0.1 MPa-0.5 MPa; And / or, the storage temperature of the thermoplastic prepreg is 20℃-30℃.

10. A structural component for a low-altitude aircraft, characterized in that, Includes the thermoplastic prepreg composition according to any one of claims 1-6 or the thermoplastic prepreg according to any one of claims 8-9.

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