A phenolic resin prepreg, a method for preparing the same, a sandwich structure and an application of the sandwich structure

Abstract

The application relates to the technical field of aviation composites, in particular to a phenolic resin prepreg, a preparation method thereof, a sandwich structure and application of the sandwich structure; the phenolic resin prepreg comprises fibers and a resin, the resin is made of raw materials including a phenolic resin, a toughening agent, a silane coupling agent, a flame retardant and a curing agent, the toughening agent comprises a carboxyl-terminated butylnitrile rubber prepolymer, and the carboxyl-terminated butylnitrile rubber prepolymer is obtained by reacting carboxyl-terminated butylnitrile rubber and polyether amine with a molar ratio of 1:(0.4-0.9). The modified carboxyl-terminated butylnitrile rubber prepolymer is used as the toughening agent, can not only play a good toughening effect, but also can effectively improve the uniformity between the resin and the fibers and improve various performances of the product.

Description

Technical Field

[0001] This application relates to the field of aerospace composite materials technology, specifically to a phenolic resin prepreg and its preparation method, sandwich structure, and application of the sandwich structure. Background Technology

[0002] The cargo hold floor of a civil aircraft container is a key component of the cargo hold, and demand continues to rise with the rapid growth of the global aviation market. While China has made breakthroughs in the field of passenger and cargo hold flooring for civil aircraft, container cargo hold floors require even stricter lightweight (≤3.3kg / m²) requirements. 2 Requirements such as high strength (e.g., room temperature long beam bending ultimate load ≥1100N) and flame retardancy still require technological breakthroughs to achieve domestic substitution.

[0003] Prepregs are composed of a matrix resin (such as epoxy resin, phenolic resin, etc.) and reinforcing fibers (carbon fiber, glass fiber, aramid fiber, etc.), and are widely used in aerospace, automobile manufacturing, bridge engineering, etc. Chinese patent CN 116100907 B discloses a method for preparing an aircraft cargo hold floor, including the following steps: preparing a phenolic resin upper panel layer, a phenolic resin lower panel layer, an epoxy composite film, and a phenolic foam-filled honeycomb core, respectively; wherein the resin component of the prepreg for the panel includes 100 parts phenolic resin, 5-15 parts toughening agent, 2-8 parts flame retardant, 0.1-0.2 parts coupling agent, and 0-15 parts curing agent. The toughening agent is similar to that of most prepregs, using materials such as rubber, such as carboxyl-terminated nitrile butadiene rubber or polyvinyl butyral.

[0004] However, while carboxylated nitrile rubber (CBR) has good toughening effects, its addition to the resin increases the viscosity of the resin system, leading to poor wettability during subsequent fiber compounding and affecting the performance of the finished product. Meanwhile, the requirements for container cargo hold floor specifications are ≤3.3 kg / m². 2 (43% lighter than the floor in the bulk area), but the room temperature long beam bending limit load requirement is ≥1100N. The contradiction between lightweight and high strength places extremely high demands on the structural design. Summary of the Invention

[0005] This application provides a phenolic resin prepreg, its preparation method, a sandwich structure, and its application. The application uses a modified carboxyl-terminated butadiene-acrylonitrile rubber prepolymer as a toughening agent, which not only provides excellent toughening but also effectively improves the uniformity between the resin and fiber, thereby enhancing the product's various properties. This meets the performance requirements of container cargo hold floors.

[0006] In a first aspect, this application provides a phenolic resin prepreg, which adopts the following technical solution:

[0007] A phenolic resin prepreg includes fibers and resin, wherein the resin is made from raw materials including phenolic resin, toughening agent, silane coupling agent, flame retardant, and curing agent, wherein the toughening agent includes a carboxyl-terminated nitrile butadiene rubber prepolymer, which is obtained by reacting a carboxyl-terminated nitrile butadiene rubber and a polyetheramine in a molar ratio of 1:(0.4-0.9).

[0008] By adopting the above technical solution, this application utilizes polyetheramine to modify carboxyl-terminated nitrile butadiene rubber and obtains a carboxyl-terminated nitrile butadiene rubber prepolymer. On the one hand, the combination of carboxyl-terminated nitrile butadiene rubber and polyetheramine in the prepolymer can further improve the toughening effect of the toughening agent. On the other hand, suitable ether bonds are introduced into the carboxyl-terminated nitrile butadiene rubber prepolymer. The introduction of ether bonds can effectively improve the problems of increased resin viscosity, poor dispersibility and wettability caused by using carboxyl-terminated nitrile butadiene rubber alone, so that the fiber and resin are fully combined and the performance of the finished product is improved.

[0009] Furthermore, the phenolic resin includes thermoplastic phenolic resin or thermosetting phenolic resin; when the phenolic resin is thermoplastic phenolic resin, the raw materials of the prepreg also include a curing agent.

[0010] Furthermore, the preparation method of the carboxyl-terminated butadiene-acrylonitrile rubber prepolymer includes the following steps: mixing carboxyl-terminated butadiene-acrylonitrile rubber and polyetheramine, heating to 60-90℃ and reacting for 1.5-4h, and cooling to room temperature to obtain the prepolymer.

[0011] Furthermore, the polyetheramine is a bifunctional polyetheramine with a molecular weight range of 200-2000. Even further, the polyetheramine can be D-230, D-400, or D-2000.

[0012] By adopting the above technical solutions and optimizing the above-mentioned polyetheramine, the polyetheramine and the carboxyl-terminated butadiene-acrylonitrile rubber prepolymer have good reactivity and good toughening effect.

[0013] Furthermore, the flame retardant includes at least one of bromoantimony compound flame retardant, aluminum hydroxide, magnesium hydroxide, and phosphorus-nitrogen flame retardant, wherein the bromoantimony compound flame retardant is a mixture of antimony trioxide and tetrabromobisphenol A.

[0014] Further, the mass ratio of the phenolic resin, toughening agent, silane coupling agent, and flame retardant is (80-100):15:(0.2-2):(5-20). When the phenolic resin is a thermoplastic phenolic resin and the raw materials also include a curing agent, the mass ratio of the phenolic resin, toughening agent, silane coupling agent, flame retardant, and curing agent is (80-100):15:(0.2-2):(5-20):(5-15).

[0015] Furthermore, the silane coupling agent can be one or more of KH550, KH560, KH570, etc.; the curing agent can be hexamethylenetetramine or an acid catalyst, and the acid catalyst can be phosphoric acid, p-toluenesulfonic acid, hydrochloric acid, etc.

[0016] Furthermore, the resin content in the prepreg is 30-50% by mass.

[0017] Secondly, this application provides a method for preparing a phenolic resin prepreg, which adopts the following technical solution:

[0018] A method for preparing a phenolic resin prepreg includes the following steps:

[0019] Phenolic resin and prepolymer are stirred and mixed at 40-80℃; then silane coupling agent and flame retardant are added sequentially and stirred and mixed, and finally the mixture is heated and cured to obtain resin material; when the phenolic resin is thermoplastic phenolic resin, phenolic resin and prepolymer are stirred and mixed at 40-80℃; then silane coupling agent and flame retardant are added sequentially and stirred and mixed, then a curing agent is added, and finally the mixture is heated and cured to obtain resin material.

[0020] The resin material is prepared into a film using a film-making machine, and then the film is laminated with fibers using a laminating machine to obtain phenolic resin prepreg.

[0021] Furthermore, in the staged heating and curing step, the resin material is obtained by sequentially holding the resin material at a temperature of 60-90℃ for 1-1.5h, at a temperature of 100-120℃ for 1.5-2.5h, and at a temperature of 140-170℃ for 2.5-5h.

[0022] Furthermore, the fibers can be surface-treated in advance by immersing them in an ethanol solution of KH550 for 5 minutes, and then drying them at 110°C for 2 hours for later use.

[0023] Thirdly, this application provides a sandwich structure using the above-mentioned phenolic resin prepreg, employing the following technical solution:

[0024] A sandwich structure using the above-mentioned phenolic resin prepreg includes a honeycomb core and panels disposed on both sides of the honeycomb core. The panels are made of the above-mentioned phenolic resin prepreg, and an adhesive film is disposed between the panels and the honeycomb core. The sandwich structure is prepared by a co-curing process.

[0025] Furthermore, the adhesive film is an epoxy adhesive film, which originally includes 50-80 parts of epoxy resin matrix, 15-25 parts of toughening agent, 10-30 parts of flame retardant, and 5-15 parts of curing agent. Among them, the toughening agent is carboxyl-terminated nitrile butadiene rubber, hydroxyl-terminated nitrile butadiene rubber, polyethersulfone, polyaryletherketone, etc.; the flame retardant is melamine polyphosphate, aluminum hydroxide / magnesium hydroxide, bromine antimony compound flame retardant, etc.; and the curing agent is at least one of dicyandiamide, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenylmethane, m-phenylenediamine, and polyamide.

[0026] Furthermore, the preparation method of the epoxy film includes the following steps: The raw materials are mixed evenly, and a flame-retardant epoxy film is prepared using a two-step hot-melt process. First, the modified epoxy resin is prepared into a film using a film-making machine. Then, the film is laminated with a carrier using a laminating machine to obtain the final film structure. The carrier has a surface weight of 15–40 g / m². 2 Plain-weave fiberglass fabrics, with the final carrier-containing film surface weight controlled at 100–200 g / m². 2 .

[0027] Furthermore, the sandwich structure uses medium- to high-density Nomex or Kevlar honeycomb cores as the core material.

[0028] Furthermore, the sandwich structure is prepared using a co-curing process, specifically including the following steps:

[0029] Cutting: Cutting phenolic prepreg, honeycomb core, and epoxy film;

[0030] Packaging: From bottom to top, the sequence is: release material - phenolic resin prepreg (bottom panel) - epoxy film - honeycomb core - epoxy film - phenolic resin prepreg (top panel) - release material;

[0031] Curing: The encapsulated material is placed in a hot press for curing at a temperature of 120–180°C, a pressure of 0.3–1 MPa, and a time of 1–3 hours.

[0032] Demolding: When the temperature drops below 60℃, the pressure is released and the mold is demolded to obtain a sandwich structure.

[0033] Fourthly, this application provides an application of a sandwich structure for manufacturing container cargo hold floors.

[0034] In summary, this application has the following beneficial effects:

[0035] 1. This application uses carboxyl-terminated nitrile butadiene rubber (NBR) as a toughening system. Furthermore, polyetheramine is used to modify the NBR, resulting in a prepolymer of NBR used as a toughening agent. This toughening agent effectively improves the problems of increased resin viscosity and decreased wettability caused by the addition of NBR to the resin system. Moreover, it exhibits excellent toughening effect, effectively improving the performance of the prepreg and consequently enhancing the performance of subsequent products. Specifically, the sheet material of this application achieves a long beam bending load (W direction) of over 1600N at room temperature, and an insert shear strength of over 8000N at room temperature, meeting the mechanical performance requirements of the product.

[0036] 2. Based on the prepreg in this application, the sandwich structure adopts a co-curing process instead of a secondary bonding process, reducing two steps, lowering energy consumption by 30%, reducing costs, and maintaining excellent performance. Furthermore, the co-curing process reduces manual operation, improving batch consistency and quality stability. It meets the mechanical and flame-retardant performance requirements of container cargo hold floors. Detailed Implementation

[0037] The present application will be further described in detail below with reference to the embodiments.

[0038] Example

[0039] This application first provides a method for preparing a toughening agent, including the following steps:

[0040] Take carboxyl-terminated butadiene-acrylonitrile rubber (CTBN) and polyetheramine in a molar ratio of 1:(0.4-0.9). Add CTBN to a flask at room temperature, then add polyetheramine dropwise. Then heat to 60-90℃ and react for 1.5-4 hours. Cool to room temperature to obtain carboxyl-terminated butadiene-acrylonitrile rubber prepolymer, i.e. toughening agent.

[0041] This application also discloses a method for preparing a phenolic resin prepreg, comprising the following steps:

[0042] The phenolic resin and prepolymer are stirred and mixed at a temperature of 40-80℃ (preferably 60℃); then a silane coupling agent and a flame retardant are added sequentially and stirred (if thermoplastic phenolic resin is used, a curing agent also needs to be added and stirred); in the final stage, the temperature is raised and cured to obtain a resin material; the resin material is prepared into a film using a film-making machine, and then the film is laminated with fibers using a laminating machine to obtain a phenolic resin prepreg. During the lamination process, the pressure is 0.3-1.0 MPa, the temperature is 80-110℃, and the time is 1-3 hours. Preferably, in the embodiments of this application, the pressure is 0.6 MPa, the temperature is 100℃, and the time is 2 hours.

[0043] The mass ratio of phenolic resin, toughening agent, silane coupling agent, and flame retardant is (80-100):15:(0.2-2):(5-20); when the phenolic resin is a thermoplastic phenolic resin, the mass ratio of phenolic resin, toughening agent, silane coupling agent, flame retardant, and curing agent is (80-100):15:(0.2-2):(5-20):(5-15). The flame retardant is a bromine-antimony compound flame retardant, which is a mixture of antimony trioxide and tetrabromobisphenol A, with a mass ratio of antimony trioxide to tetrabromobisphenol A of 1:(2-4). In this embodiment, the silane coupling agent is preferably KH550, and the curing agent is preferably hexamethylenetetramine. The thermoplastic phenolic resin in this embodiment (Examples 1-3) is model BMJ-92, and the thermosetting phenolic resin in Example 4 is model T399HF. The mass ratio of antimony trioxide to tetrabromobisphenol A in this embodiment (Examples 1-4) is 1:3. The fiber is a twill glass fiber fabric.

[0044] In the staged heating and curing step, the resin material is obtained by sequentially holding the resin at 60-90℃ for 1-1.5h, 100-120℃ for 1.5-2.5h, and 140-170℃ for 2.5-5h.

[0045] This application embodiment also provides a sandwich structure, including a honeycomb core and panels disposed on both sides of the honeycomb core. The panels are made of the aforementioned phenolic resin prepreg, and an adhesive film is disposed between the panels and the honeycomb core. The method for preparing the sandwich structure includes the following steps:

[0046] Cutting: Cutting phenolic prepreg, honeycomb core, and epoxy film;

[0047] Packaging: From bottom to top, the sequence is: release material - phenolic resin prepreg (bottom panel) - epoxy film - honeycomb core - epoxy film - phenolic resin prepreg (top panel) - release material;

[0048] Curing: The encapsulated material is placed in a hot press for curing at a temperature of 120–180°C, a pressure of 0.3–1 MPa, and a time of 1–3 hours. Preferably, in this embodiment, the encapsulated material is placed in a hot press for curing at a temperature of 145°C, a pressure of 0.6 MPa, and a time of 1.5 hours.

[0049] Demolding: When the temperature drops below 60℃, the pressure is released and the container cargo hold floor with a sandwich structure is obtained.

[0050] The preparation method of the epoxy film includes the following steps:

[0051] 50-80 parts of epoxy resin matrix, 15-25 parts of toughening agent, 10-30 parts of flame retardant, and 5-15 parts of curing agent are mixed evenly. A flame-retardant epoxy film is prepared using a two-step hot-melt process. First, the modified epoxy resin is prepared into a film using a film-making machine. Then, the film is laminated with a carrier using a laminating machine to obtain the final film structure. The film thickness is 0.05 mm. During the lamination process, the pressure is 0.5-2.0 MPa, the temperature is 100-150℃, and the time is 1-1.5 h. Preferably, in this embodiment, the pressure is 1.0 MPa, the temperature is 120℃, and the time is 1.5 h.

[0052] The carrier has a surface weight of 15–40 g / m³. 2 Plain-weave fiberglass fabrics, with the final carrier-containing film surface weight controlled at 100–200 g / m². 2 Preferably, the carrier has a surface weight of 25 g / m³. 2 The plain-weave glass fiber fabric, with the final carrier-containing film surface weight controlled at 150±15g / m². 2 .

[0053] Furthermore, the sandwich structure uses a medium-to-high density Nomex honeycomb core or Kevlar honeycomb core as the core material, preferably a Nomex honeycomb core, with a thickness of 8.85 mm. The toughening agent is carboxyl-terminated nitrile butadiene rubber, hydroxyl-terminated nitrile butadiene rubber, polyethersulfone, polyaryletherketone, etc.; the flame retardant is melamine polyphosphate, aluminum hydroxide / magnesium hydroxide, bromine-antimony compound flame retardant, etc.; the curing agent is at least one of dicyandiamide, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenylmethane, m-phenylenediamine, and polyamide.

[0054] Preferably, in this embodiment, the raw materials of the epoxy film include: 60 parts of epoxy resin matrix, 20 parts of toughening agent, 15 parts of flame retardant, and 6 parts of curing agent; wherein, the epoxy resin matrix is ​​bisphenol A type epoxy resin, grade E-51, the toughening agent is hydroxyl-terminated nitrile rubber, the flame retardant is aluminum hydroxide, and the curing agent is dicyandiamide.

[0055] The sandwich structure obtained in this embodiment can be used as the floor of a container cargo hold.

[0056] The following explanation is provided through specific examples.

[0057] Example

[0058] Example 1

[0059] This embodiment first provides a method for preparing a toughening agent, including the following steps:

[0060] Carboxyl-terminated butadiene-acrylonitrile rubber (CTBN) and polyetheramine D400 were prepared in a molar ratio of 1:0.8. CTBN was added to a flask at room temperature, followed by the dropwise addition of polyetheramine D400. The mixture was then heated to 80°C and reacted for 2 hours. After cooling to room temperature, the carboxyl-terminated butadiene-acrylonitrile rubber prepolymer, i.e., toughening agent, was obtained.

[0061] This embodiment also provides a method for preparing phenolic resin prepreg, including the following steps:

[0062] Phenolic resin and prepolymer were stirred and mixed at 60℃; then silane coupling agent and flame retardant were added and stirred in sequence, followed by the addition of hexamethylenetetramine curing agent and stirring; finally, the temperature was raised and cured, specifically at 80℃ for 1 hour, at 110℃ for 2 hours, and at 150℃ for 3 hours, to obtain the resin material.

[0063] The resin material is prepared into a film using a film-forming machine, and then the film is laminated with fibers using a laminating machine to obtain a phenolic resin prepreg. The surface weight of the prepreg is 430±20 g / m². 2 The resin content is 35%.

[0064] The mass ratio of phenolic resin, toughening agent, silane coupling agent, flame retardant, and curing agent is 85:15:0.5:12:7.

[0065] This embodiment also provides a sandwich structure, including a honeycomb core and panels disposed on both sides of the honeycomb core. The panels are made of the aforementioned phenolic resin prepreg, and an adhesive film is disposed between the panels and the honeycomb core.

[0066] Example 2

[0067] This embodiment first provides a method for preparing a toughening agent, including the following steps:

[0068] Carboxyl-terminated butadiene-acrylonitrile rubber (CTBN) and polyetheramine D230 were prepared in a molar ratio of 1:0.4. CTBN was added to a flask at room temperature, followed by the dropwise addition of polyetheramine D230. The mixture was then heated to 80°C and reacted for 2 hours. After cooling to room temperature, the carboxyl-terminated butadiene-acrylonitrile rubber prepolymer, i.e., toughening agent, was obtained.

[0069] This embodiment also provides a method for preparing phenolic resin prepreg, including the following steps:

[0070] Phenolic resin and prepolymer were stirred and mixed at 60℃; then silane coupling agent and flame retardant were added and stirred in sequence, followed by the addition of hexamethylenetetramine curing agent and stirring; finally, the temperature was raised and cured, specifically at 80℃ for 1 hour, at 110℃ for 2 hours, and at 150℃ for 3 hours, to obtain the resin material.

[0071] The resin material is prepared into a film using a film-forming machine, and then the film is laminated with fibers using a laminating machine to obtain a phenolic resin prepreg. The surface weight of the prepreg is 434±15 g / m². 2 The resin content is 35%.

[0072] The mass ratio of phenolic resin, toughening agent, silane coupling agent, flame retardant, and curing agent is 80:15:0.2:5:5.

[0073] This embodiment also provides a sandwich structure, including a honeycomb core and panels disposed on both sides of the honeycomb core. The panels are made of the aforementioned phenolic resin prepreg, and an adhesive film is disposed between the panels and the honeycomb core.

[0074] Example 3

[0075] This embodiment first provides a method for preparing a toughening agent, including the following steps:

[0076] Carboxyl-terminated butadiene-acrylonitrile rubber (CTBN) and polyetheramine D2000 were prepared in a molar ratio of 1:0.9. CTBN was added to a flask at room temperature, followed by the dropwise addition of polyetheramine D2000. The mixture was then heated to 80°C and reacted for 2 hours. After cooling to room temperature, the carboxyl-terminated butadiene-acrylonitrile rubber prepolymer, i.e., toughening agent, was obtained.

[0077] This embodiment also provides a method for preparing phenolic resin prepreg, including the following steps:

[0078] Phenolic resin and prepolymer were stirred and mixed at 60℃; then silane coupling agent and flame retardant were added and stirred in sequence, followed by the addition of hexamethylenetetramine curing agent and stirring; finally, the temperature was raised and cured, specifically at 80℃ for 1 hour, at 110℃ for 2 hours, and at 150℃ for 3 hours, to obtain the resin material.

[0079] The resin material is prepared into a film using a film-forming machine, and then the film is laminated with fibers using a laminating machine to obtain a phenolic resin prepreg. The surface weight of the prepreg is 425±20 g / m². 2 The resin content is 35%.

[0080] The mass ratio of phenolic resin, toughening agent, silane coupling agent, flame retardant, and curing agent is 100:15:2:20:15.

[0081] This embodiment also provides a sandwich structure, including a honeycomb core and panels disposed on both sides of the honeycomb core. The panels are made of the aforementioned phenolic resin prepreg, and an adhesive film is disposed between the panels and the honeycomb core.

[0082] Example 4

[0083] This embodiment first provides a method for preparing a toughening agent, including the following steps:

[0084] Carboxyl-terminated butadiene-acrylonitrile rubber (CTBN) and polyetheramine D230 were prepared in a molar ratio of 1:0.8. CTBN was added to a flask at room temperature, followed by the dropwise addition of polyetheramine D230. The mixture was then heated to 80°C and reacted for 2 hours. After cooling to room temperature, the carboxyl-terminated butadiene-acrylonitrile rubber prepolymer, i.e., toughening agent, was obtained.

[0085] This embodiment also provides a method for preparing phenolic resin prepreg, including the following steps:

[0086] Phenolic resin and prepolymer were stirred and mixed at 60℃; then silane coupling agent and flame retardant were added and stirred and mixed in sequence. Finally, the temperature was raised and cured, specifically at 80℃ for 1 hour, at 110℃ for 2 hours, and at 150℃ for 3 hours to obtain resin material.

[0087] The resin material is prepared into a film using a film-forming machine, and then the film is laminated with fibers using a laminating machine to obtain a phenolic resin prepreg. The prepreg has a surface weight of 422±20 g / m2 and a resin content of 35%.

[0088] The mass ratio of phenolic resin, toughening agent, silane coupling agent, and flame retardant is 100:15:0.5:12.

[0089] This embodiment also provides a sandwich structure, including a honeycomb core and panels disposed on both sides of the honeycomb core. The panels are made of the aforementioned phenolic resin prepreg, and an adhesive film is disposed between the panels and the honeycomb core.

[0090] Comparative Example

[0091] The difference between Comparative Example 1 and Example 1 is that the toughening agent is a mixture of carboxyl-terminated butadiene-acrylonitrile rubber and polyetheramine, without prepolymerization.

[0092] The difference between Comparative Example 2 and Example 1 is that the molar ratio of carboxyl-terminated butadiene-acrylonitrile rubber (CTBN) to polyetheramine is 1:0.2.

[0093] The difference between Comparative Example 3 and Example 1 is that the molar ratio of carboxyl-terminated butadiene-acrylonitrile rubber (CTBN) to polyetheramine is 1:1.1.

[0094] The difference between Comparative Example 4 and Example 1 is that the carboxyl-terminated nitrile butadiene rubber was replaced with carboxyl-terminated styrene-butadiene rubber.

[0095] The difference between Comparative Example 5 and Example 1 is that the polyetheramine is replaced with monofunctional polyetheramine FL-1000.

[0096] Performance testing

[0097] The performance of the sandwich structures, i.e. container cargo hold floors, prepared in the examples and comparative examples were tested, and the relevant results are shown in Tables 1 and 2.

[0098] Table 1 Performance test results of the embodiment

[0099]

[0100]

[0101] Table 2 Performance test results of the comparative examples

[0102]

[0103] As can be seen from the performance test of Example 1, the sandwich structure obtained in this application has good mechanical properties under the specified size and density requirements, and meets the practical performance requirements of container cargo hold floor.

[0104] Further analysis of the performance of Comparative Example 1 revealed that when the carboxyl-terminated nitrile butadiene rubber and polyetheramine were not reacted to obtain the carboxyl-terminated nitrile butadiene rubber prepolymer, and the carboxyl-terminated nitrile butadiene rubber and polyetheramine were directly used as toughening agents, the properties of the Comparative Example 1 sheet decreased to varying degrees under the same size and density. This indicates that the application of this invention, which uses the carboxyl-terminated nitrile butadiene rubber and polyetheramine to prepare the carboxyl-terminated nitrile butadiene rubber prepolymer in advance as a toughening agent, can improve the wettability between the fiber and the resin, and has a good toughening effect, thereby improving the various properties of the sheet.

[0105] Further analysis of the performance of Comparative Examples 2 and 3 revealed that although both examples still utilized polyetheramine to modify the carboxyl-terminated nitrile butadiene rubber, their performance remained poor. This is because insufficient polyetheramine is insufficient to modify the carboxyl-terminated nitrile butadiene rubber, while excessive polyetheramine increases the proportion of flexible polyether segments in the prepolymer, reduces polarity, and worsens compatibility with phenolic resin. In this case, the toughening agent is prone to phase separation, forming large agglomerates or uneven dispersion. Furthermore, the amino groups of polyetheramine are reactive, and excessive unreacted amino groups may react with the hydroxymethyl groups in the phenolic resin, disrupting the cross-linked network structure of the phenolic resin itself.

[0106] In addition, regarding the modification of carboxyl-terminated nitrile butadiene rubber, the analysis of Comparative Examples 4 and 5 shows that only suitable types of polyetheramines can better modify carboxyl-terminated nitrile butadiene rubber, so that the toughening agent can have a good toughening effect and improve the performance of the finished product; while monofunctional polyetheramines, due to direct end-capping, will cause poor compatibility, resulting in the toughening agent being unable to play its role.

[0107] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A phenolic resin prepreg, characterized in that, It includes fibers and resin, wherein the resin is made from raw materials including phenolic resin, toughening agent, silane coupling agent and flame retardant; the mass ratio of phenolic resin to toughening agent is (80~100):15; The toughening agent includes a carboxyl-terminated butadiene-acrylonitrile rubber prepolymer, which is obtained by reacting carboxyl-terminated butadiene-acrylonitrile rubber and polyetheramine in a molar ratio of 1:(0.4~0.9). The preparation method of the carboxyl-terminated butadiene-acrylonitrile rubber prepolymer includes the following steps: mixing carboxyl-terminated butadiene-acrylonitrile rubber and polyetheramine, heating to 60~90℃, reacting for 1.5~4h, and cooling to room temperature to obtain the prepolymer; The polyetheramine is a bifunctional polyetheramine with a molecular weight of 200-2000.

2. The phenolic resin prepreg according to claim 1, characterized in that, The flame retardant includes at least one of bromo-antimony compound flame retardant, aluminum hydroxide, magnesium hydroxide, and phosphorus-nitrogen flame retardant, wherein the bromo-antimony compound flame retardant is a mixture of antimony trioxide and tetrabromobisphenol A.

3. The phenolic resin prepreg according to claim 1, characterized in that, The mass ratio of the phenolic resin, toughening agent, silane coupling agent, and flame retardant is (80~100):15:(0.2~2):(5~20).

4. The phenolic resin prepreg according to claim 1, characterized in that, The resin content in the prepreg is 30-50% by mass.

5. A method for preparing a phenolic resin prepreg as described in any one of claims 1 to 4, characterized in that, Includes the following steps: Phenolic resin and prepolymer are stirred and mixed at a temperature of 40~80℃; then silane coupling agent and flame retardant are added in sequence and stirred and mixed; finally, the temperature is raised and cured to obtain resin material. The resin material is prepared into a film using a film-making machine, and then the film is laminated with fibers using a laminating machine to obtain phenolic resin prepreg.

6. The method for preparing a phenolic resin prepreg according to claim 5, characterized in that, In the staged heating and curing step, the resin material is obtained by sequentially holding it at 60~90℃ for 1~1.5h, at 100~120℃ for 1.5~2.5h, and at 140~150℃ for 2.5~5h.

7. A sandwich structure using the phenolic resin prepreg as described in any one of claims 1 to 4, characterized in that, The invention includes a honeycomb core and panels disposed on both sides of the honeycomb core. The panels are made of phenolic resin prepreg as described in any one of claims 1 to 4. An adhesive film is disposed between the panels and the honeycomb core. The sandwich structure is prepared by a co-curing process.

8. An application of the sandwich structure as described in claim 7, characterized in that, The sandwich structure is used to prepare the container cargo hold floor.

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