Functionalized cage polysilsesquioxane toughened bismaleimide resins and composites thereof, methods of making and uses

Abstract

The application provides a functionalized cage polysilsesquioxane toughened bismaleimide resin and a composite material thereof, a preparation method and an application, and belongs to the field of composite materials. The bismaleimide resin is modified by the functionalized cage polysilsesquioxane, and the resin with significantly improved strength and toughness and excellent thermomechanical properties is prepared. The interlaminar shear performance of the carbon fiber composite material with the resin as a matrix is significantly improved, and the carbon fiber composite material has a good application prospect in the fields of aerospace, electronic appliances, automobile industry and the like.

Description

Technical Field

[0001] This invention belongs to the field of composite materials, specifically relating to a functionalized cage-type polysilsesquioxane-toughened bismaleimide resin and its composite materials, preparation method and uses. Background Technology

[0002] Bismaleimide (BMI) is a high-performance thermosetting resin widely used in aerospace, electronics, and automotive industries due to its excellent heat resistance, chemical resistance, electrical insulation, and mechanical properties. The BMI molecule contains abundant maleimide double bonds, which undergo cross-linking reactions during curing to form a highly cross-linked three-dimensional network structure, thus endowing the material with superior properties.

[0003] Despite its many excellent properties, BMI resin is relatively brittle and lacks toughness, making it prone to crack propagation and fracture under stress concentration or low-temperature conditions. This limits its use in applications requiring high toughness. The brittleness of BMI resin mainly stems from its highly cross-linked rigid network structure. When subjected to external forces, stress concentrates at the crack tip, easily leading to rapid crack propagation and ultimately brittle fracture. Diallylbisphenol A (DPI) exhibits good compatibility with bismaleimide diphenylmethane, significantly improving processing performance and toughness. Therefore, BMI resin typically refers to a compound system of the two and has been widely used.

[0004] To further enhance the toughness of BMI resin, other components can be introduced into the above system to modify BMI. These modifications mainly include: rubber toughening, where rubber elastomers are introduced into the BMI resin to absorb energy through the deformation of the rubber phase, thereby improving the material's toughness; thermoplastic resin toughening, where thermoplastic resins are introduced into the BMI resin to form a semi-interpenetrating network structure, improving the material's toughness and impact resistance; inorganic filler toughening, where inorganic fillers, such as carbon nanotubes and graphene, are introduced into the BMI resin to improve the material's toughness through interfacial effects and bridging; and copolymerization modification, where flexible segments are introduced through copolymerization with other monomers, reducing the resin's crosslinking density and improving the material's toughness.

[0005] However, suitable toughening modification requires comprehensive consideration of the balance between toughening effect and other properties such as heat resistance and processing performance. The biggest advantage of BMI resin compared to more common epoxy resins is its heat resistance; sacrificing heat resistance significantly for toughening is counterproductive. For example, Wang et al. modified BMI resin with diallyl benzoxazine (Wang Y, Kou K, Zhuo L, et al. Thermal, mechanical and dielectric properties of BMI modified by the Bis allyl benzoxazine[J]. Journal of Polymer Research, 2015, 22: 1-8.), and the results showed that although the impact strength of the modified resin increased to 11.8 kJ / m... 2 Its flexural strength is increased to 124.1 MPa, but its glass transition temperature is reduced to 225°C, which limits its application in high-temperature environments.

[0006] Toughening BMI resin can effectively enhance the toughness of carbon fiber composites, thus broadening their service life and application range. However, the strength of the resin itself and the interfacial properties of the composite should not be sacrificed due to the toughening process. For example, Guo Jizhang introduced thermoplastic resin into bismaleimide resin for toughening modification (Study on the performance of high-modulus and high-strength carbon fiber reinforced bismaleimide resin-based composites [D]. Nanchang Aviation University, 2021.), which increased the impact strength by about 46%, achieving a good toughening effect, while the heat resistance remained basically unchanged. However, due to the presence of the interlaminar toughening structure, the interfacial properties of the toughened composite were relatively poor, resulting in lower 90° tensile, 90° compressive, and interlaminar shear properties compared to the untoughened composite.

[0007] Therefore, a toughening method that maintains or even enhances the thermomechanical properties of BMI resin and the interlaminar shear properties of carbon fiber composites is provided. This method can not only improve the impact resistance and fatigue resistance of the material, but also enhance its reliability and service life, thereby broadening its application fields. Summary of the Invention

[0008] The purpose of this invention is to provide a functionalized cage-type polysilsesquioxane-toughened bismaleimide resin and its composite materials, preparation method, and applications.

[0009] This invention provides a modified resin, which is a modified resin with functionalized cage-type polysilsesquioxane as toughening agent and bismaleimide resin as matrix, wherein the mass of functionalized cage-type polysilsesquioxane accounts for 0.01% to 10% of the mass of the modified resin.

[0010] Furthermore, the functionalized cage-like polysilsesquioxane is dispersed as a toughening agent in the bismaleimide resin matrix.

[0011] Furthermore, the functionalized cage-like polysilsesquioxane accounts for 0.05% to 0.3% of the mass of the modified resin, preferably 0.1% to 0.3%.

[0012] Furthermore, its raw materials include functionalized cage-type polysilsesquioxane, diallyl bisphenol A, and bismaleimide diphenylmethane; the mass ratio of diallyl bisphenol A to bismaleimide diphenylmethane is 2-4:3-5, preferably 3:4;

[0013] The bismaleimide monomer is selected from bismaleimide diphenylmethane, 1,2-phenylene-bis-maleimide, N,N'-m-phenylenebismaleimide, N,N'-(1,4-phenylene)bismaleimide, N,N'-(4-methyl-1,3-phenylene)bismaleimide, 2,2″-bis[4-(4-maleimide-phenoxy)phenyl]propane, and bis(3-ethyl-5-methyl-4-maleimide-phenyl)methane.

[0014] Furthermore, the functionalized cage-type polysilsesquioxane is prepared by dehydration condensation of silane compounds, wherein the silane compounds are selected from allyltrichlorosilane, octenyltrichlorosilane, chloropropyltrichlorosilane, aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, and allyltriethoxysilane.

[0015] Furthermore, the functionalized cage-like polysilsesquioxane is

[0016] The present invention also provides a composite material, the raw materials of which include the above-mentioned modified resin and fiber.

[0017] Furthermore, the fiber is selected from carbon fiber, glass fiber, aramid fiber, basalt fiber, polyimide fiber, polyphenylene sulfide fiber, polybenzimidazole fiber, poly(p-phenylenebenzobisoxazole) fiber, and preferably carbon fiber.

[0018] The present invention also provides a method for preparing the above-mentioned modified resin and composite material, the method comprising the following steps: mixing and reacting functionalized cage-type polysilsesquioxane, diallyl bisphenol A and bismaleimide diphenylmethane, and curing to obtain the modified resin; or, mixing and reacting functionalized cage-type polysilsesquioxane, diallyl bisphenol A and bismaleimide diphenylmethane to obtain a resin prepolymer, and combining the resin prepolymer with carbon fiber to prepare a prepreg, and curing to obtain the composite material.

[0019] Furthermore, the reaction temperature is 100–150°C, and the time is 0.01–1 hour;

[0020] The curing conditions are as follows: reaction at 140-160℃ for 1-3 hours, reaction at 170-190℃ for 1-3 hours, reaction at 210-230℃ for 3-5 hours, and reaction at 240-260℃ for 3-5 hours in sequence.

[0021] Furthermore, the reaction was carried out at a temperature of 140°C for 0.5 hours.

[0022] The curing conditions are as follows: reaction at 150°C for 2 hours, reaction at 180°C for 2 hours, reaction at 220°C for 4 hours, and reaction at 250°C for 4 hours in sequence.

[0023] This invention also provides the use of the above-mentioned modified resins and composite materials in the preparation of materials for the aerospace, electronics, and automotive industries.

[0024] Experimental results show that the present invention uses functionalized cage-type polysilsesquioxane-modified bismaleimide resin to prepare a resin with significantly improved strength and toughness and excellent thermomechanical properties. The interlaminar shear properties of carbon fiber composites based on this resin are significantly improved, and it has good application prospects in aerospace, electronics, automotive industry and other fields.

[0025] Obviously, based on the above description of the present invention, and according to common technical knowledge and conventional methods in the field, various other modifications, substitutions or alterations can be made without departing from the basic technical concept of the present invention.

[0026] The following detailed embodiments further illustrate the above-described content of the present invention. However, this should not be construed as limiting the scope of the present invention to the following embodiments. All technologies implemented based on the above-described content of the present invention fall within the scope of the present invention. Attached Figure Description

[0027] Figure 1 The NMR spectrum of octaallyl POSS is 1H NMR and solid-state NMR spectrum is 1S NMR.

[0028] Figure 2 The NMR 1H spectrum and solid-state NMR silicon spectrum of octaaminopropyl POSS.

[0029] Figure 3 The ILSS cross section of functionalized POSS-modified BDM / DBA and M40J composite material (left: untreated carbon fiber, middle: POSS-ally, right: POSS-AP). Detailed Implementation

[0030] The functionalized cage-like polysilsesquioxanes used in the embodiments of this invention are either commercially available products or synthesized chemically by those skilled in the art using known knowledge and experimental methods through the following reaction route:

[0031] (1) Preparation of POSS-ally

[0032] 8.78 g of allyltrichlorosilane (ATCS) was dissolved in 50 mL of xylene and stirred with 100 mL of water for 5 hours. After removing the aqueous layer using a separatory funnel, the xylene layer was washed three times with water, and 2.4 mL of a phase transfer catalyst (20% benzyltrimethylammonium hydroxide / methanol solution) was added. The mixture was refluxed at 60 °C for 4 hours and then allowed to stand for 4 days. The mixture was then refluxed again at 60 °C for 24 hours, cooled, filtered, washed, and dried to obtain a white solid powder, octaallyl POSS, denoted as POSS-ally.

[0033]

[0034] (2) Preparation of POSS-AP

[0035] 180 mL of methanol was added to a 250 mL three-necked flask, followed by 10 mL of 3-aminopropyltriethoxysilane (APTES) and 15 mL of dilute hydrochloric acid (HCl, 36-38%). The mixture was heated to 70 °C and refluxed for 19 h. The reaction solution was then added to an equal volume of tetrahydrofuran, immediately turning into a white emulsion. After standing, a white precipitate formed at the bottom. The precipitate was washed with a 1:1 mixture of methanol and tetrahydrofuran to remove unreacted APTES and HCl. After several washes, the mixture was vacuum filtered to obtain octaaminopropyl POSS, denoted as POSS-AP.

[0036]

[0037] Example 1: Preparation of functionalized POSS-modified BDM / DBA resin

[0038] POSS-ally was dispersed in methanol to form a homogeneous solution. 39 g of diallyl bisphenol A (DBA) was added at 75°C and stirred for 4 h. Then, 52 g of bismaleimide diphenylmethane (BDM) was added to form a blend of the three, with the mass of POSS-ally controlled to be 0.1 wt% of the total mass of POSS-ally, DBA, and BDM. The mixture was prepolymerized at 140°C for half an hour, followed by degassing at 150°C under vacuum for 1 hour to obtain a resin casting solution. The resin casting solution was cured using the following curing regime: 150°C for 2 h + 180°C for 2 h + 220°C for 4 h + 250°C for 4 h. After annealing, a functionalized POSS-modified BDM / DBA resin casting was obtained, denoted as 0.1% POSS-ally.

[0039] Example 2: Preparation of functionalized POSS-modified BDM / DBA resin

[0040] Referring to the method of Example 1, in preparing functionalized POSS-modified BDM / DBA resin, the only difference is that the mass of POSS-ally is controlled to be 0.05wt%, 0.2wt%, and 0.3wt% of the total mass of POSS-ally, DBA, and BDM, respectively; or, POSS-ally is replaced with POSS-AP and the mass of POSS-AP is controlled to be 0.05wt%, 0.1wt%, 0.2wt%, and 0.3wt% of the total mass of POSS-AP, DBA, and BDM, respectively. Different functionalized POSS-modified BDM / DBA resin castings are prepared, which are denoted as 0.05% POSS-ally, 0.2% POSS-ally, 0.3% POSS-ally, 0.05% POSS-AP, 0.1% POSS-AP, 0.2% POSS-AP, and 0.3% POSS-AP, respectively.

[0041] Example 3: Preparation of functionalized POSS-modified BDM / DBA resin-based carbon fiber composite material

[0042] POSS-ally was dispersed in methanol to form a homogeneous solution. Then, 39g of diallyl bisphenol A (DBA) was added at 75℃ and stirred for 4 hours. Next, 52g of bismaleimide diphenylmethane (BDM) was added at 140℃ for half an hour of prepolymerization. The mass of POSS-ally was controlled to be 0.1wt% of the total mass of POSS-ally, DBA, and BDM. The mixture was then defoamed under vacuum at 150℃ for 1 hour to obtain a resin prepolymer. The resin prepolymer was coated onto M40J carbon fibers to prepare a prepreg, which was then placed in a mold for hot-press curing. The resin curing regime was: 150℃ for 2 hours + 180℃ for 2 hours + 220℃ for 4 hours + 250℃ for 4 hours. After annealing, a functionalized POSS-modified BDM / DBA resin-based carbon fiber composite material was obtained, denoted as 0.1% POSS-ally-M40J.

[0043] Example 4: Preparation of functionalized POSS-modified BDM / DBA resin-based carbon fiber composite material

[0044] Referring to the method of Example 3, in preparing functionalized POSS-modified BDM / DBA resin-based carbon fiber composite material, the only difference is that POSS-ally is replaced with POSS-AP and the mass of POSS-AP is controlled to be 0.1 wt% of the total mass of POSS-AP, DBA and BDM, thus obtaining 0.1% POSS-AP-M40J.

[0045] The following section describes the preparation of comparative samples.

[0046] Comparative Example 1: Preparation of BDM / DBA Resin

[0047] Referring to the method in Example 1, when preparing the functionalized POSS-modified BDM / DBA resin casting, no POSS was added, and the resulting BDM / DBA resin casting was denoted as BDM / DBA.

[0048] Comparative Example 2: Preparation of BDM / DBA Resin-Based Carbon Fiber Composites

[0049] Referring to the method in Example 3, when preparing functionalized POSS-modified BDM / DBA resin-based carbon fiber composite material, no POSS was added, resulting in BDM / DBA-M40J.

[0050] The following experimental examples demonstrate the beneficial effects of the present invention.

[0051] Experimental Example 1: Structural Characterization of POSS-ally and POSS-AP

[0052] 1. Experimental Methods

[0053] POSS-ally and POSS-AP were dissolved in deuterated dimethyl sulfoxide for 400MHz proton NMR spectroscopy, while POSS-ally and POSS-AP powders were directly subjected to 400MHz silicon NMR spectroscopy.

[0054] 2. Experimental Results

[0055] Figure 1 These are the POSS-ally 1H NMR and solid-state 1H NMR spectra. The 1H NMR spectrum shows that the chemical shifts, from low to high, are the peaks for the methylene group of the allyl group and the hydrogen atoms on the double bond in the cage-like siloxane structure, with an area ratio of 2:1:2, corresponding to the number of hydrogen atoms.

[0056] A sharp singlet was observed at -82.2 ppm in the solid-state NMR silicon spectrum, which is a typical peak for T8 structure silicon atoms. This indicates that all silicon atoms are in the same chemical environment, meaning the product is a fully condensed hexahedral siloxane structure.

[0057] Figure 2These are POSS-AP NMR (H1Nm) and solid-state NMR (SiNm) spectra. The H1Nm spectrum shows that the chemical shifts, from low to high, are the peaks for hydrogen atoms on the methylene and amino groups of the aminopropyl group within the cage-like siloxane structure, with an area ratio of 1:1:1:1, corresponding to the number of hydrogen atoms. The amino hydrogen has a higher chemical shift because the formation of hydrogen bonds in organic molecules reduces the electron cloud density around the hydrogen nucleus, resulting in a deshielding effect that significantly increases the chemical shift of hydrogen on the nitrogen atom, which can form hydrogen bonds. Due to the electron traction effect (inductive effect) of the two nitrogen atoms, the H1Nm spectrum of the hydrogen-bonded proton appears at a low-field position.

[0058] A sharp singlet was observed at -78.3 ppm in the solid-state NMR silicon spectrum, which is a typical peak for T8 structure silicon atoms. This indicates that all silicon atoms are in the same chemical environment, meaning the product is a fully condensed hexahedral siloxane structure.

[0059] Experimental Example 2: Performance Characterization of Functionalized POSS-Modified BDM / DBA Resin

[0060] 1. Experimental Methods

[0061] The resin castings prepared in Examples 1 and 2 were subjected to mechanical property tests according to standard GB / T 2567-2021 "Test Methods for Properties of Resin Castings", specifically including tensile, unnotched impact, and flexural performance tests. Dynamic thermomechanical properties were obtained by testing the resin castings on a DMA (Mechanical and Dynamic Mechanics) testing machine.

[0062] 2. Experimental Results

[0063] Tables 1 and 2 show the mechanical properties of POSS-ally and POSS-AP modified BDM / DBA resins. The highest impact strength was observed when the functionalized POSS content was 0.3 wt%, with 0.3 wt% POSS-AP exhibiting the highest impact strength at 11.49 kJ / m². 2 The highest elongation at break was observed when the amount of functionalized POSS added was 0.1 wt%, with the highest elongation at break (2.32%) observed at 0.1% POSS-AP.

[0064] Table 1 Mechanical properties of octaallyl POSS-modified BDM / DBA resin

[0065]

[0066] Table 2 Mechanical properties of octaaminopropyl POSS modified BDM / DBA resin

[0067]

[0068] Table 3 shows the dynamic thermomechanical properties of POSS-ally and POSS-AP modified BDM / DBA resins. For POSS-ally, 0.1 wt% POSS-ally has the highest crosslinking density, at which point the material's strength and elongation at break are also the highest. Functionalized POSS acts as a "site occupant" in the bismaleimide crosslinking network, hindering further crosslinking. At higher contents, the resin crosslinking density decreases, and the mechanical properties decrease accordingly. With increasing POSS-AP content, the storage modulus (E') first increases and then decreases, with E' gradually weakening at high temperatures, and the glass transition temperature (T) decreasing. g The crosslinking density gradually decreases. The E' of 0.1wt% POSS-AP is the highest, and at this point, the tensile strength, elongation at break, and flexural strength of the material are also the highest.

[0069] Table 3 Dynamic thermomechanical properties of functionalized POSS-modified BDM / DBA resin

[0070]

[0071]

[0072] Example 3: Characterization of functionalized POSS-modified BDM / DBA resin-based carbon fiber composites

[0073] 1. Experimental Methods

[0074] The resin-based carbon fiber composites prepared in Examples 3 and 4 were tested for interlaminar shear strength according to ASTM D2344 to evaluate the interfacial properties of the composites. Interlaminar shear strength (ILSS) reflects the macroscopic debonding performance of the composite interface.

[0075] 2. Experimental Results

[0076] Table 4 shows the ILSS of the functionalized POSS-modified BDM / DBA and M40J composite material. Figure 3 The images show the interlaminar shear strength (ILSS) cross-sections of the functionalized POSS-modified BDM / DBA / M40J composite material (left: untreated carbon fiber, middle: POSS-ally, right: POSS-AP). It can be seen that the interlaminar shear strength of the composite material is enhanced after POSS functionalization. Furthermore, compared with the 0.1% POSS-ally modified BDM / DBA resin-based carbon fiber composite material, the interlaminar shear strength of the 0.1% POSS-AP modified BDM / DBA resin-based carbon fiber composite material is significantly improved.

[0077] The functionalized POSS-modified BDM / DBA resin-based carbon fiber composite material of this invention can better adapt to deformation and slow down the crack propagation rate when shear occurs.

[0078] Table 4 Interlaminar shear strength of functionalized POSS-modified BDM / DBA resin

[0079]

[0080] In summary, this invention provides a functionalized cage-type polysilsesquioxane-modified bismaleimide resin, its composite materials, preparation method, and applications. This invention utilizes functionalized cage-type polysilsesquioxane to modify bismaleimide resin, resulting in a resin with significantly improved strength and toughness and excellent thermomechanical properties. Carbon fiber composites based on this resin exhibit significantly improved interlaminar shear properties, showing promising application prospects in aerospace, electronics, and automotive industries.

Claims

1. A modified resin, characterized in that, The modified resin is prepared by: POSS-ally was dispersed in methanol to form a homogeneous solution. 39 g of diallyl bisphenol A was added at 75°C and stirred for 4 hours. Then, 52 g of bismaleimide diphenylmethane was added to form a blend of the three. The mass of POSS-ally was controlled to be 0.3 wt% of the total mass of POSS-ally, diallyl bisphenol A, and bismaleimide diphenylmethane. The mixture was prepolymerized at 140°C for half an hour, and then defoamed under vacuum at 150°C for 1 hour to obtain a resin casting solution. The resin casting solution was cured using the following curing regime: 150°C for 2 hours + 180°C for 2 hours + 220°C for 4 hours + 250°C for 4 hours. After annealing, the modified resin was obtained. Alternatively, POSS-AP is dispersed in methanol to form a homogeneous solution. 39g of diallyl bisphenol A is added at 75°C and stirred for 4 hours. Then, 52g of bismaleimide diphenylmethane is added to form a blend of the three, controlling the mass of POSS-AP to be 0.1wt% of the total mass of POSS-AP, diallyl bisphenol A, and bismaleimide diphenylmethane. The mixture is prepolymerized at 140°C for half an hour, and then defoamed under vacuum at 150°C for 1 hour to obtain a resin casting solution. The resin casting solution is then cured using the following curing regime: 150°C for 2 hours + 180°C for 2 hours + 220°C for 4 hours + 250°C for 4 hours. After annealing, the modified resin is obtained. Alternatively, POSS-AP is dispersed in methanol to form a homogeneous solution. 39g of diallyl bisphenol A is added at 75°C and stirred for 4 hours. Then, 52g of bismaleimide diphenylmethane is added to form a blend of the three, controlling the mass of POSS-AP to be 0.3wt% of the total mass of POSS-AP, diallyl bisphenol A, and bismaleimide diphenylmethane. The mixture is prepolymerized at 140°C for half an hour, and then defoamed under vacuum at 150°C for 1 hour to obtain a resin casting solution. The resin casting solution is then cured using the following curing regime: 150°C for 2 hours + 180°C for 2 hours + 220°C for 4 hours + 250°C for 4 hours. After annealing, the modified resin is obtained. The structure of the POSS-ally is as follows: ; The structure of the POSS-AP is as follows: .

2. A composite material, characterized in that, Its raw materials include the modified resin and fiber as described in claim 1.

3. A method for preparing the modified resin of claim 1 and the composite material of claim 2, characterized in that, The method includes the following steps: mixing and reacting POSS-ally or POSS-AP, diallyl bisphenol A and bismaleimide diphenylmethane, and curing to obtain a modified resin; or mixing and reacting POSS-ally or POSS-AP, diallyl bisphenol A and bismaleimide diphenylmethane to obtain a resin prepolymer, and then combining the resin prepolymer with carbon fibers to prepare a prepreg, and curing to obtain a composite material.

4. Use of the modified resin of claim 1 and the composite material of claim 2 in the preparation of materials with high flexural strength and impact strength in the aerospace, electronics, and automotive industries.

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