High-strength low-density epoxy SMC composite material and preparation method thereof

Abstract

The application belongs to the field of epoxy resin composites, and specifically provides a high-strength low-density epoxy SMC composite material and a preparation method thereof, which is prepared by the following steps: S01. Taking a PVC core plate, gluing after grooving, then laying a fiber cloth, vacuumizing under negative pressure after film covering, then pouring a pre-impregnation liquid, and placing to obtain a pre-cured composite plate; S02. Taking the pre-cured composite plate, placing overnight after mold pressing treatment, and then obtaining after demolding and edge trimming treatment; the pre-impregnation liquid preparation step comprises the following: mixing an active diluent, an accelerator, modified microspheres and a filler, first adding an epoxy resin, stirring, then adding the remaining amount of epoxy resin, and then adding a curing agent and a demolding agent, and continuously mixing to obtain the pre-impregnation liquid; the modified microspheres are used as a pre-impregnation liquid additive component, and the prepared SMC composite material product has a density ≤1.57 g / cm 3 , an impact strength ≥84.5 KJ / m 2 , and good flame retardance.

Description

Technical Field

[0001] This application belongs to the field of epoxy resin composite material technology, and in particular relates to a high-strength, low-density epoxy SMC composite material and its preparation method. Background Technology

[0002] Sheet molding compound (SMC) is a thermosetting fiber-reinforced composite material. Compared with traditional metal materials, SMC composite materials have significant advantages such as high specific strength and high specific modulus, and have been widely used in the automotive, rail transportation, electronics and electrical and construction fields.

[0003] SMC composite materials are mainly produced by coating a fiber-reinforced core board with gel coat, vacuuming it, then injecting prepreg under negative pressure, and finally thermosetting. The prepreg, as the continuous phase of the SMC composite, plays a crucial role in bonding the reinforcing fibers and transferring stress after curing, and its liquid phase composition significantly affects the material's properties. The SMC composite prepreg mainly consists of a resin matrix, fillers, thickeners, initiators, polymerization inhibitors, and release agents. The resin matrix used, categorized by raw material type, primarily includes epoxy resin, unsaturated polyester resin, and phenolic resin. Epoxy resin, in particular, exhibits significant advantages over other resin components due to its high bonding strength, low curing shrinkage, and excellent heat resistance. To promote the lightweighting of SMC composites, hollow glass microspheres are often added to the prepreg. However, glass microspheres themselves have poor impact resistance and compatibility issues with the resin system, affecting the material's service life.

[0004] Patent application CN117343519A discloses a lightweight polyester SMC (polyester molding compound) with excellent thermal stability and its preparation method. The method uses silane-modified hollow ceramic microspheres instead of traditional glass microspheres, and through treatment, ester organic substances are coated on the surface of the hollow ceramic microspheres to improve the compatibility between the microspheres and the system, thus preparing an SMC product with good mechanical strength.

[0005] Although the aforementioned application documents describe how modifying hollow ceramic microspheres before adding them to the system can improve the mechanical strength of the composite material and enhance the compatibility between the microspheres and the resin, the ceramic microspheres used have a high density, which is not conducive to material lightweighting. Furthermore, the ceramic microspheres themselves are rigid particles with limited impact resistance. Therefore, it is necessary to find a high-strength, low-density epoxy SMC composite material and its preparation method that can promote the lightweighting of the composite material, improve its impact resistance, and enhance the compatibility between the added components and the resin system. Summary of the Invention

[0006] To address the aforementioned issues and further promote the lightweighting of composite materials, improve impact resistance, and enhance the compatibility of additives with the resin system, this application provides a high-strength, low-density epoxy SMC composite material and its preparation method.

[0007] This application first provides a method for preparing a high-strength, low-density epoxy SMC composite material, which includes the following steps:

[0008] S01. Take a PVC core board, groove it and apply glue, then lay fiber cloth, then cover it with film and vacuum it, inject prepreg liquid under negative pressure, and place it to obtain a pre-cured composite board.

[0009] S02. Take a pre-cured composite board, control the pressure at 10-12MPa and the temperature at 140-150℃, mold it overnight, and then demold and trim it to obtain the final product.

[0010] The prepreg solution is prepared by mixing the following raw materials in parts by weight: 60-70 parts epoxy resin, 15-20 parts modified microspheres, 3-5 parts reactive diluent, 3-4 parts curing agent, 1-2 parts accelerator, and 0.5-1 part release agent; the preparation steps include the following:

[0011] Take the reactive diluent, accelerator, modified microspheres and filler and mix them. Add epoxy resin first and stir. Then add the remaining epoxy resin, then add curing agent and release agent, and continue mixing to obtain the prepreg solution.

[0012] The modified microspheres are obtained by dry mixing of amino-terminated template-deformed polyetheretherketone microspheres and mixed micro powders by air-drying, followed by granulation by binder spraying.

[0013] The mixed micro powder is obtained by mixing montmorillonite, aluminum hydroxide and magnesium hydroxide in a mass ratio of (10-15):(2-3):(3.5-4);

[0014] The mass ratio of the initial addition of epoxy resin to the supplementary addition of epoxy resin is (3-4):(9-10).

[0015] By adopting the above technical solution, modified microspheres, as the main additive component of the prepreg, can promote the lightweighting process of the cured resin. During the preparation of the modified microspheres, after template removal, the polyetheretherketone (PEEK) microspheres form a cavity structure, resulting in microspheres with low apparent density. Since the template removal process leaves micropores on the microsphere surface, mixed micropowder is used for pore sealing to prevent the liquid phase components of the prepreg from penetrating into the cavities after the modified microspheres are added to the prepreg system. Amino end-capping modification gives the microsphere surface a positive charge, which on the one hand inhibits the self-agglomeration of microspheres during spray granulation; on the other hand, in the early dry mixing stage of spray granulation, the positive charge on the microsphere surface can adsorb the negatively charged montmorillonite in the mixed micropowder, achieving preliminary pore sealing. When the charge reaches a neutral state, the microsphere surface is electrically saturated. At this time, the electrically neutral components in the mixed micropowder continue to adhere to the microsphere surface under the action of the binder, thereby enhancing the pore sealing effect.

[0016] Furthermore, the modified microspheres are prepared using the following steps:

[0017] (1). Take silane-modified glass microspheres, disperse them, then add hydroquinone, difluorobenzophenone and base catalyst, heat and react, then add end-capping agent for further treatment, and after filtration, washing and drying, obtain templated polyether ether ketone;

[0018] (2). Take the templated polyetheretherketone, treat it with etching solution overnight, then filter and dry to obtain detemplated polyetheretherketone;

[0019] (3) Remove the template polyether ether ketone and mix the micro powder by blowing dry, then use a binder spray granulation, and the product is sieved to obtain modified microspheres.

[0020] Furthermore, in step (1), the preparation steps of the silane-modified glass microspheres include the following:

[0021] Glass microspheres were taken, activated with mixed acid, mixed with silane coupling agent, dispersed, heated and filtered to obtain silane-modified glass microspheres.

[0022] The average particle size of the glass microspheres is 100-150 micrometers;

[0023] The mixed acid is prepared by mixing concentrated sulfuric acid with a mass concentration of 93%-98% and hydrogen peroxide with a mass concentration of 28%-30% in a volume ratio of (8-10):(2-3).

[0024] The silane coupling agent is one or two of diphenyldimethoxysilane, phenyltrimethoxysilane, and p-chlorophenyltrimethoxysilane;

[0025] The mass ratio of the glass microspheres to the silane coupling agent is (10-12):(0.2-0.3).

[0026] By employing the above technical solution, the silanol groups on the surface of glass microspheres are activated after treatment with mixed acid. Subsequently, a heated grafting reaction is carried out with a silane coupling agent containing benzene rings. The benzene rings in the coupling agent act as sterically hindered groups, forming grafting sites with varying density on the surface of the glass microspheres. The steric hindrance effect in the region adjacent to the benzene rings results in a lower polymerization density of the templated polyetheretherketone (PEEK), while other regions exhibit denser polymerization. During subsequent etching, this controllable density distribution of the templated PEEK product allows the etching solution to preferentially penetrate the template layer through the low-density steric hindrance sites, promoting the detemplation process of PEEK and ultimately obtaining PEEK microspheres with a regular cavity structure.

[0027] Furthermore, in step (1), the mass ratio of silane-modified glass microspheres, hydroquinone, difluorobenzophenone, alkaline catalyst and end-capping agent used is (3-4):(4.4-5.2):(8.1-8.7):(2-3):(0.5-0.6);

[0028] The capping agent is , , , One or two of them.

[0029] By adopting the above technical solution, the phenolic hydroxyl group of the end-capping agent molecule, as a monofunctional end-capping unit, can participate in the polyether ether ketone polymerization reaction and actively terminate chain growth. The unreacted amino functional groups remain on the surface of the polyether ether ketone microspheres after polymerization and are protonated during the acid etching process, making the surface of the polyether ether ketone microspheres positively charged. Through electrostatic adsorption, the positively charged polyether ether ketone microspheres preferentially attract the negatively charged montmorillonite component in the mixed micropowder, thereby achieving the pre-sealing of the pores on the surface of the microspheres.

[0030] Furthermore, in step (1), the heating reaction is as follows: adjust the temperature to 130-140℃ and stir the reaction for 3-4 hours, then raise the temperature to 150-165℃ and maintain it for 2-3 hours;

[0031] The alkaline catalyst is either potassium carbonate or sodium carbonate.

[0032] By adopting the above technical solution, during the synthesis of polyether ether ketone under heating and alkaline catalysis, the silanol groups on the surface of the activated glass microspheres preferentially adsorb and enrich the monomer molecules in the early stage of the polymerization reaction through the formation of hydrogen bonds and other forces. Subsequently, the adsorbed monomers are polymerized using the surface of the glass microspheres as a template to obtain polyether ether ketone with a regular structure.

[0033] Furthermore, in step (2), the etching solution is obtained by mixing ammonium fluoride with a mass concentration of 38%-40% and hydrofluoric acid with a mass concentration of 5.5%-8.5% in a volume ratio of (4-5):(1-2).

[0034] By adopting the above technical solution, the etching solution can penetrate the polyetheretherketone layer structure and corrode the internal glass microspheres through the low-density pores created by the steric hindrance of the silane coupling agent, thereby achieving template removal.

[0035] Furthermore, in step (3), the mixed powder is composed of montmorillonite, aluminum hydroxide, and magnesium hydroxide in a specific ratio.

[0036] (10-15):(2-3):(3.5-4) were mixed to obtain the solution;

[0037] The average particle size of the montmorillonite is 0.5-1 μm;

[0038] The aluminum hydroxide has an average particle size of 30-50 nm.

[0039] The average particle size of the magnesium hydroxide is 20-30 nm.

[0040] By adopting the above technical solution, aluminum hydroxide and magnesium hydroxide in the mixed micro powder can continue to seal the pores left in the low-density area of ​​the microspheres due to the templated polyether ether ketone etching process, and decompose as flame retardant components when heated. Through the difference in decomposition temperature, a long-lasting flame retardant barrier is constructed.

[0041] In step (3), the preparation steps of the adhesive include the following: take polyvinyl alcohol, maleic acid, tetraethyl orthosilicate and water, mix them, disperse them by ultrasonication, adjust the viscosity to 20-25 cP and the pH value to 5.5-6.2, and the adhesive is obtained.

[0042] This application also provides a high-strength, low-density epoxy SMC composite material prepared by the above preparation method.

[0043] Compared with the prior art, this application has the following beneficial effects:

[0044] 1. This application obtains low-density polyether ether ketone modified microspheres through template-based processing combined with template removal, and uses them as an additive component in the prepreg to prepare SMC composite materials, thereby promoting the lightweighting of the composite materials. Compared with traditional glass microspheres, the modified microspheres have better compatibility with the resin and better impact resistance. After being added to the system, they can improve the problem of easy breakage of composite materials due to phase separation and impact, and the composite materials have a longer service life.

[0045] 2. This application uses end-capping agents to terminate the growth of polyether ether ketone chains and promote the positive electrochemical oxidation of the modified microsphere surface. The modified microspheres can be attracted by negatively charged montmorillonite in the mixed micro powder through electrostatic adsorption, pre-sealing the micropores remaining on the surface of the modified microspheres due to etching treatment, and preventing the modified microspheres from losing their cavity structure due to wetting after being added to the pre-impregnation liquid system. Different flame retardant components in the mixed micro powder can also construct a long-lasting flame retardant barrier through the difference in decomposition temperature.

[0046] 3. Using the modified microspheres of this application as an additive component in the prepreg solution, the density of the prepared SMC composite material product is ≤1.57 g / cm³. 3 Impact strength ≥84.5KJ / m 2 It has good flame retardancy. Attached Figure Description

[0047] Figure 1 The apparent density test results are for the modified microspheres of Examples 1-4, Comparative Examples 1-2, and the template-free polyether ether ketone of Comparative Example 3. Detailed Implementation

[0048] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0050] When using “including,” “having,” and “contains” as described herein, the intention is to cover non-exclusive inclusion, unless an explicit qualifying term such as “only,” “consisting of,” etc., is used, in which case another component may be added.

[0051] The terms "preferred," "more preferably," "better," and "even better" used in this application refer to embodiments of this application that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this application. That is, in this application, "preferred," "more preferably," "better," and "even better" are merely descriptions of implementations or embodiments with better effects, but do not constitute a limitation on the scope of protection of this application.

[0052] In this application, terms such as "further," "even more," and "particularly" are used for descriptive purposes and indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0053] In this application, "at least one" means one or more, such as one, two, or more. "Multiple" or "several" means at least two, such as two, three, etc., and "multi-layered" means at least two layers, such as two layers, three layers, etc., unless otherwise explicitly specified. In the description of this application, "several" means at least one, such as one, two, etc., unless otherwise explicitly specified.

[0054] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0055] Unless otherwise specified, all steps in this application may be performed sequentially or randomly. For example, the method comprising steps (a) and (b) indicates that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order; for example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc. Unless otherwise stated, singular terms may include plural forms and should not be construed as having a quantity of one.

[0056] In this application, "above" or "below" includes the number itself. For example, "below 1" includes 1.

[0057] In this application, room temperature refers to 0~40℃, including but not limited to 10~40℃, or further to 20~30℃.

[0058] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in this application, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. All reagents or instruments whose manufacturers are not specified are conventional products that can be purchased commercially. In addition to the specific methods, equipment, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description in this application, any prior art methods, equipment, and materials similar to or equivalent to those described, used, or made by the methods, equipment, and materials in the embodiments of this application may be used to implement this application.

[0059] The technical solution of the present invention will be explained in detail below with reference to several representative embodiments.

[0060] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0061] Description of raw materials used in the embodiments and comparative examples of this invention:

[0062] Glass microspheres with an average particle size of 100-150 μm;

[0063] High-strength fiberglass cloth, Grade S, surface density 200g / m² 2 ;

[0064] Carbon fiber cloth, 3K, areal density 150g / m 2 ;

[0065] PVC core board, flame retardant (V0), density 1.45g / cm³;

[0066] Adhesive (DS100A), viscosity 3000-4000 cP;

[0067] Triglycidyl m-aminophenol (MF-3302), EE (epoxy equivalent) ≥96g / eq;

[0068] Montmorillonite, MgO wt% ≥ 5.24, average particle size 0.5-1 μm;

[0069] Aluminum hydroxide, with an average particle size of 30-50 nm;

[0070] Magnesium hydroxide, with an average particle size of 20-30 nm.

[0071] Preparation Example 1

[0072] Mix 40 mL of 93 wt% concentrated sulfuric acid with 10 mL of 28 wt% hydrogen peroxide, then add 10 g of glass microspheres, activate at 75 ℃ for 20 min, then adjust the pH to 6.8, wash with water and dry, then mix with 0.2 g of diphenyldimethoxysilane, add 0.5 mL of polyvinylpyrrolidone and 50 mL of anhydrous ethanol under a nitrogen atmosphere, adjust the magnetic stirring at 200 rpm for 10 min, then raise the temperature to 80 ℃ for 5 h, filter and dry to obtain silane-modified glass microspheres.

[0073] Mix 20 mL of toluene with 50 mL of dimethyl sulfoxide, add 0.5 mL of Tween-20 and 3 g of silane-modified glass microspheres, adjust the magnetic stirring speed to 100 rpm, add 4.4 g of hydroquinone, 8.1 g of 4,4'-difluorobenzophenone and 2 g of potassium carbonate to the system under a nitrogen atmosphere, stir at 130 °C for 3 h, then raise the temperature to 150 °C and maintain for 2 h, then add 0.5 g of 2,4-diaminophenol and continue treatment for 0.5 h, then filter and collect the filtrate, wash once with anhydrous ethanol and twice with hot water at 60 °C, and dry to obtain templated polyether ether ketone.

[0074] Mix 40 mL of 38 wt% ammonium fluoride with 10 mL of 5.5 wt% hydrofluoric acid, then add 5 g of templated polyether ether ketone, treat overnight, filter and collect the solid part, adjust the pH to 6.5, wash twice with water, and dry to obtain detemplated polyether ether ketone.

[0075] Preparation Example 2

[0076] Mix 45 mL of 95 wt% concentrated sulfuric acid with 12 mL of 28 wt% hydrogen peroxide, then add 11 g of glass microspheres. Activate at 80 °C for 30 min, then adjust the pH to 7.1. After washing and drying, mix with 0.1 g of phenyltrimethoxysilane and 0.2 g of p-chlorophenyltrimethoxysilane. Under a nitrogen atmosphere, add 1 mL of polyvinylpyrrolidone and 60 mL of anhydrous ethanol. Stir with magnetic stirring at 250 rpm for 10 min, then raise the temperature to 85 °C for 6 h. After filtration and drying, obtain silane-modified glass microspheres.

[0077] Mix 20 mL of toluene with 60 mL of dimethyl sulfoxide, add 0.8 mL of Tween-20 and 4 g of silane-modified glass microspheres, adjust the magnetic stirring speed to 200 rpm, add 4.8 g of hydroquinone, 8.5 g of 4,4'-difluorobenzophenone and 3 g of sodium carbonate to the system under a nitrogen atmosphere, stir at 135 °C for 4 h, then raise the temperature to 155 °C and maintain for 3 h, then add 0.4 g of 4-amino-2-methylphenol and 0.2 g of 3-aminophenol, continue treatment for 1 h, then filter and collect the filtrate, wash twice with anhydrous ethanol and three times with hot water at 60 °C, and dry to obtain templated polyether ether ketone.

[0078] Mix 50 mL of 40 wt% ammonium fluoride with 10 mL of 8.5 wt% hydrofluoric acid, then add 6 g of templated polyether ether ketone, treat overnight, filter and collect the solid portion, adjust the pH to 6.8, wash with water 3 times, and dry to obtain detemplated polyether ether ketone.

[0079] Preparation Example 3

[0080] Mix 50 mL of 98 wt% concentrated sulfuric acid with 15 mL of 30 wt% hydrogen peroxide, then add 12 g of glass microspheres. Activate at 80 °C for 30 min, then adjust the pH to 7.2. After washing and drying, mix with 0.25 g of p-chlorophenyltrimethoxysilane. Under a nitrogen atmosphere, add 1 mL of polyvinylpyrrolidone and 75 mL of anhydrous ethanol. Stir magnetically at 300 rpm for 10 min, then raise the temperature to 90 °C for 6 h. After filtration and drying, obtain silane-modified glass microspheres.

[0081] Mix 20 mL of toluene with 65 mL of dimethyl sulfoxide, add 0.8 mL of Tween-20 and 4 g of silane-modified glass microspheres, adjust the magnetic stirring speed to 200 rpm, add 5.2 g of hydroquinone, 8.7 g of 4,4'-difluorobenzophenone and 3 g of sodium carbonate to the system under a nitrogen atmosphere, stir at 140 °C for 4 h, then raise the temperature to 165 °C and maintain for 3 h, then add 0.6 g of 3-aminophenol and continue treatment for 1 h, then filter and collect the filtrate, wash twice with anhydrous ethanol and three times with hot water at 60 °C, and dry to obtain templated polyether ether ketone.

[0082] Mix 50 mL of 40 wt% ammonium fluoride with 20 mL of 8.5 wt% hydrofluoric acid, then add 6 g of templated polyether ether ketone, treat overnight, filter and collect the solid portion, adjust the pH to 6.8, wash three times with water, and dry to obtain detemplated polyether ether ketone.

[0083] Example 1

[0084] Mix 2g polyvinyl alcohol, 0.3g ammonium citrate, 0.5g maleic acid, 1mL glycerol, 5mL tetraethyl orthosilicate and 50mL deionized water, and ultrasonically disperse at 20KHz for 5min. Adjust the viscosity to 20cP and the pH to 5.5 to obtain the binder.

[0085] Take 10g of montmorillonite, 2g of aluminum hydroxide and 3.5g of magnesium hydroxide and mix and disperse for 1min. Mix with 50g of template-free polyether ether ketone and dry mix with a blower at a flow rate of 12×20L / min for 5min. Then open the atomizer and control the inlet air temperature at 120℃, the outlet air temperature at 80℃ and the atomization pressure at 0.2MPa. Use a binder for spray granulation and then pass through a 100-mesh sieve to obtain modified microspheres.

[0086] Mix 30g of ethylene glycol diglycidyl ether, 10g of triethylamine, and 150g of modified microspheres. Adjust the stirring speed to 200rpm and treat for 3min. Then add 150g of triglycidyl-m-aminophenol and continue treatment for 20min. Then add 450g of triglycidyl-m-aminophenol to the system, followed by 30g of m-phenylenediamine and 5g of zinc stearate. Continue stirring and treating for 0.5h to obtain the pre-impregnation solution.

[0087] Take a 500mm×200mm×20mm PVC core board, cut and drill holes in both directions, then apply 180g / m². 2 The surface layer of adhesive is brushed with adhesive, and a single layer of high-strength glass fiber cloth and carbon fiber cloth are laid in a two-dimensional mixture. Then, a gel coat is applied, a vacuum is drawn under negative pressure, and a conduit is connected. The prepreg is poured in until it flows and fills the mold completely. After standing for 2 hours, a molding machine is used to control the pressure at 10 MPa, the temperature at 140℃, the molding speed at 50 mm / s, and the pressure is maintained for 3 minutes. The mixture is then left to stand overnight at room temperature. After trimming, a high-strength, low-density epoxy SMC composite material is obtained.

[0088] The template-free polyether ether ketone was prepared in Preparation Example 1.

[0089] Example 2

[0090] Mix 2.5g polyvinyl alcohol, 0.4g ammonium citrate, 0.8g maleic acid, 1.2mL glycerol, 5mL tetraethyl orthosilicate and 50mL deionized water, and ultrasonically disperse at 20KHz for 5min. Adjust the viscosity to 24cP and the pH to 5.8 to obtain the binder.

[0091] Take 12g of montmorillonite, 2.5g of aluminum hydroxide and 3.5g of magnesium hydroxide, mix and disperse for 3min, then mix with 50g of template-free polyether ether ketone, control the blower flow rate to 12×20L / min and dry mix for 5min, then open the atomizer, control the inlet air temperature to 120℃, the outlet air temperature to 80℃, and the atomization pressure to 0.2MPa, use a binder for spray granulation, and then pass through a 100-mesh sieve to obtain modified microspheres.

[0092] Mix 35g of ethylene glycol diglycidyl ether, 10g of triethylamine, and 150g of modified microspheres, and treat with a stirring speed of 200rpm for 3min. Then add 180g of triglycidyl-m-aminophenol and continue treatment for 20min. Next, add 500g of triglycidyl-m-aminophenol to the system, then add 40g of m-phenylenediamine and 8g of zinc stearate, and continue stirring for 1h to obtain the pre-impregnation solution.

[0093] Take a 500mm×200mm×20mm PVC core board, cut and drill holes in both directions, then apply 200g / m². 2 The adhesive was brushed onto the surface of the substrate, and a single layer of high-strength glass fiber cloth and carbon fiber cloth were laid in a two-dimensional mixture. Then, a gel coat was applied, and a vacuum was drawn up. The conduit was then connected, and the prepreg was poured in until it flowed and filled the mold completely. After standing for 3 hours, a molding machine was used to control the pressure at 12 MPa, the temperature at 145℃, the molding speed at 55 mm / s, and the pressure was maintained for 5 minutes. The mixture was then left to stand overnight at room temperature. After trimming, a high-strength, low-density epoxy SMC composite material was obtained.

[0094] In this case, the template-free polyether ether ketone was prepared in Preparation Example 2.

[0095] Example 3

[0096] Take 3g of polyvinyl alcohol, 0.5g of ammonium citrate, 1g of maleic acid, 1.5mL of glycerol, 5mL of tetraethyl orthosilicate and 75mL of deionized water, mix them, and ultrasonically disperse them at 20KHz for 5min. Adjust the viscosity to 25cP and the pH value to 6.2 to obtain the binder.

[0097] Take 15g of montmorillonite, 3g of aluminum hydroxide and 4g of magnesium hydroxide and mix and disperse for 5min. Mix with 50g of template-free polyether ether ketone and dry mix with a blower at a flow rate of 12×20L / min for 5min. Then open the atomizer and control the inlet air temperature at 120℃, the outlet air temperature at 80℃ and the atomization pressure at 0.3MPa. Use a binder for spray granulation and then pass through a 100-mesh sieve to obtain modified microspheres.

[0098] Mix 50g of ethylene glycol diglycidyl ether, 20g of triethylamine, and 200g of modified microspheres. Adjust the stirring speed to 300rpm and treat for 5min. Then add 200g of triglycidyl-m-aminophenol and continue treatment for 30min. Then add 500g of triglycidyl-m-aminophenol to the system, followed by 40g of m-phenylenediamine and 10g of zinc stearate. Continue stirring and treating for 1h to obtain the pre-impregnation solution.

[0099] Take a 500mm×200mm×20mm PVC core board, cut and drill holes in both directions, then apply 200g / m². 2 The adhesive was brushed onto the surface of the substrate, and a single layer of high-strength glass fiber cloth and carbon fiber cloth were laid in a two-dimensional mixture. Then, a gel coat was applied, and a vacuum was drawn up. The conduit was then connected, and the prepreg was poured in until it flowed and filled the mold completely. After standing for 3 hours, a molding machine was used to control the pressure at 12 MPa, the temperature at 150℃, and the molding speed at 60 mm / s for 5 minutes. The mixture was then left to stand overnight at room temperature. After trimming, a high-strength, low-density epoxy SMC composite material was obtained.

[0100] In this case, the template-free polyether ether ketone was prepared in Preparation Example 3.

[0101] Example 4

[0102] The only difference between this embodiment and Example 1 is that the preparation steps of the pre-impregnation solution are as follows:

[0103] Mix 50g of ethylene glycol diglycidyl ether, 20g of triethylamine, and 180g of modified microspheres. Adjust the stirring speed to 200rpm and treat for 5min. Then add 200g of triglycidyl-m-aminophenol and continue treatment for 30min. Then add 500g of triglycidyl-m-aminophenol, 40g of m-phenylenediamine, and 8g of zinc stearate to the system and continue stirring for 1h to obtain the pre-impregnation solution.

[0104] In this case, the template-free polyether ether ketone was prepared in Preparation Example 2.

[0105] The remaining steps are the same as in Example 1.

[0106] Comparative Example 1

[0107] The difference between this comparative example and Example 1 is that the preparation steps of the modified microspheres are as follows:

[0108] Take 15g of montmorillonite, 3g of aluminum hydroxide and 4g of magnesium hydroxide and mix and disperse for 5min. Mix with 50g of templated polyetheretherketone and dry mix with a blower at a flow rate of 12×20L / min for 5min. Then open the atomizer and control the inlet air temperature at 120℃, the outlet air temperature at 80℃ and the atomization pressure at 0.3MPa. Use a binder for spray granulation and then pass through a 100-mesh sieve to obtain modified microspheres.

[0109] The remaining steps are the same as in Example 1.

[0110] Comparative Example 2

[0111] The difference between this comparative example and Example 1 is that the preparation steps of the template-free polyetheretherketone are as follows:

[0112] Mix 40 mL of 93 wt% concentrated sulfuric acid with 10 mL of 28 wt% hydrogen peroxide, then add 10 g of glass microspheres, activate at 75 ℃ for 20 min, then adjust the pH to 6.8, wash and dry, and mix with 1.5 g of diphenyldimethoxysilane. Under a nitrogen atmosphere, add 0.5 mL of polyvinylpyrrolidone and 50 mL of anhydrous ethanol, adjust the magnetic stirring at 200 rpm for 10 min, then raise the temperature to 80 ℃ for 5 h, filter and dry to obtain silane-modified glass microspheres.

[0113] Mix 20 mL of toluene with 50 mL of dimethyl sulfoxide, add 0.5 mL of Tween-20 and 3 g of silane-modified glass microspheres, adjust the magnetic stirring speed to 100 rpm, add 4.4 g of hydroquinone, 8.1 g of 4,4'-difluorobenzophenone and 2 g of potassium carbonate to the system under a nitrogen atmosphere, stir at 130 °C for 3 h, then raise the temperature to 150 °C and maintain for 2 h, then add 0.5 g of hydroquinone and continue the treatment for 0.5 h, then filter and collect the filtrate, wash once with anhydrous ethanol and twice with hot water at 60 °C, and dry to obtain templated polyether ether ketone.

[0114] Take 40 mL of 38 wt% ammonium fluoride and mix it with 10 mL of 5.5 wt% hydrofluoric acid. Then add 5 g of templated polyether ether ketone and treat overnight. Then filter and take the solid part. Adjust the pH to 6.5, wash twice with water, and dry to obtain detemplated polyether ether ketone.

[0115] The remaining steps are the same as in Example 1.

[0116] Comparative Example 3

[0117] The difference between this comparative example and Example 1 is that the preparation steps of the prepreg are as follows:

[0118] Mix 50g of ethylene glycol diglycidyl ether, 20g of triethylamine, and 200g of template-degraded polyether ether ketone, and treat with a stirring speed of 300 rpm for 5 min. Then add 200g of triglycidyl-m-aminophenol and continue treatment for 30 min. Next, add 500g of triglycidyl-m-aminophenol to the system, followed by 40g of m-phenylenediamine and 10g of zinc stearate, and continue stirring for 1 h to obtain the pre-impregnation solution.

[0119] The remaining steps are the same as in Example 1.

[0120] Performance testing

[0121] 1. Physical performance testing

[0122] Physical properties of the high-strength, low-density epoxy SMC composite materials from Examples 1-4 and Comparative Examples 1-3 were tested.

[0123] Table 1. Physical property test items of high-strength, low-density epoxy SMC composite materials in Examples 1-4 and Comparative Examples 1-3

[0124]

[0125] The test results are shown in Table 2.

[0126] Table 2. Physical property test results of high-strength, low-density epoxy SMC composite materials in Examples 1-4 and Comparative Examples 1-3

[0127]

[0128] As can be seen from Examples 1-4 and Comparative Examples 1-3, and in conjunction with Tables 1 and 2, the test samples of the Examples all meet the composite material test indicators and can maintain a product density lower than the average level of the Comparative Examples. This indicates that the SMC composite materials of the Examples can achieve better performance while meeting the requirements of lightweighting. In terms of impact strength, the impact strength of the test groups of the Examples shows an increasing trend with the increase of the amount of modified microspheres added. This indicates that within a certain range, the increase of modified microspheres helps to improve the impact resistance of SMC composite products. Combined with the fact that the test product of Comparative Example 1 without removing the template glass microspheres had the worst impact resistance among all test groups, it can be explained that the modified microspheres of the organic material increased its compatibility with the epoxy resin body, and improved the impact resistance of the composite material by toughening it through organic microspheres.

[0129] 2. Microsphere apparent density test

[0130] Referring to the national standard GB / T23652-2009, the apparent density of the modified microspheres from Examples 1-4, Comparative Examples 1-2, and the template-free polyetheretherketone from Comparative Example 3 was tested. The test results are as follows: Figure 1 As shown.

[0131] Take Examples 1-4 and Comparative Examples 1-3 and refer to Table 2 and Figure 1 It can be seen that the modified microspheres prepared using the process described in the examples have a low apparent density, which can be maintained at 0.62 g / cm³. 3 In Comparative Example 1, since the modified microspheres were not detemplated, the apparent density of the microspheres was determined by the inner glass microspheres and the outer polyether ether ketone shell. The modified microspheres prepared in Comparative Example 3 had the highest apparent density among all test groups because the detemplated polyether ether ketone was not mixed with the mixed micropowder and spray granulation was not performed. As a result, it did not have a pore-sealing structure. Based on the product density data in Table 2, since the apparent density difference of the modified microspheres in each test group of Examples 1-4 is only within 5%, the impact on product density is relatively limited. The density of the composite material product is mainly affected by the amount of modified microspheres used. In contrast to the example schemes, in Comparative Example 1, since the apparent density of the modified microspheres is much higher than that of the example schemes, the density of the composite material product is affected by the density of the microspheres, and the density of the product in Comparative Example 1 is higher than that of the other test groups. In Comparative Example 2, since the modified microspheres were not end-capped and positively electrolyzed, the surface powder of the modified microspheres in the comparative example scheme was more significantly detached during the mixing of the prepreg liquid than in the example scheme. Some exposed cavities were penetrated by the liquid phase system of the prepreg liquid, resulting in an increase in product density. In Comparative Example 3, since the template-removed polyether ether ketone was not sealed, the template-removed polyether ether ketone was wetted by the liquid phase during the mixing of the prepreg components and lost its cavity effect, resulting in a significant increase in the density of the composite material product.

[0132] Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a high-strength, low-density epoxy SMC composite material, characterized in that, It is prepared by the following steps: S01. Take a PVC core board, groove it and apply glue, then lay fiber cloth, then cover it with film and vacuum it, inject prepreg liquid under negative pressure, and place it to obtain a pre-cured composite board. S02. Take a pre-cured composite board, control the pressure at 10-12MPa and the temperature at 140-150℃, mold it overnight, and then demold and trim it to obtain the final product. The prepreg solution is prepared by mixing the following raw materials in parts by weight: 60-70 parts epoxy resin, 15-20 parts modified microspheres, 3-5 parts reactive diluent, 3-4 parts curing agent, 1-2 parts accelerator, and 0.5-1 part release agent; the preparation steps include the following: Take the reactive diluent, accelerator, modified microspheres and filler and mix them. Add epoxy resin first and stir. Then add the remaining epoxy resin, then add curing agent and release agent, and continue mixing to obtain the prepreg solution. The modified microspheres are obtained by dry mixing of amino-terminated template-deformed polyether ether ketone microspheres and mixed micro powders by air blowing, followed by granulation by binder spraying; the mixed micro powders are obtained by mixing montmorillonite, aluminum hydroxide and magnesium hydroxide in a mass ratio of (10-15):(2-3):(3.5-4). The modified microspheres were prepared using the following steps: (1). Take silane-modified glass microspheres, disperse them, then add hydroquinone, difluorobenzophenone and base catalyst, heat and react, then add end-capping agent for further treatment, and then obtain templated polyether ether ketone after filtration, washing and drying. (2). Take the templated polyetheretherketone, treat it with etching solution overnight, then filter and dry to obtain detemplated polyetheretherketone; (3) Remove the template polyether ether ketone and mix the micro powder by air drying, then use a binder spray granulation, and the product is sieved to obtain modified microspheres; In step (1), the preparation steps of silane-modified glass microspheres include the following: Glass microspheres were taken, activated with mixed acid, mixed with silane coupling agent, dispersed, heated and filtered to obtain silane-modified glass microspheres. The mixed acid is prepared by mixing concentrated sulfuric acid with a mass concentration of 93%-98% and hydrogen peroxide with a mass concentration of 28%-30% in a volume ratio of (8-10):(2-3); the silane coupling agent is one or two of diphenyldimethoxysilane, phenyltrimethoxysilane, and p-chlorophenyltrimethoxysilane. The mass ratio of the glass microspheres to the silane coupling agent is (10-12):(0.2-0.3).

2. The method for preparing a high-strength, low-density epoxy SMC composite material according to claim 1, characterized in that, The mass ratio of the initial addition of epoxy resin to the supplementary addition of epoxy resin is (3-4):(9-10).

3. The method for preparing a high-strength, low-density epoxy SMC composite material according to claim 1, characterized in that, In step (1), the mass ratio of silane-modified glass microspheres, hydroquinone, difluorobenzophenone, alkaline catalyst and end-capping agent used is (3-4):(4.4-5.2):(8.1-8.7):(2-3):(0.5-0.6); The alkaline catalyst is one of potassium carbonate and sodium carbonate; The capping agent is , , , One or two of them.

4. The method for preparing a high-strength, low-density epoxy SMC composite material according to claim 1, characterized in that, In step (1), the heating reaction is as follows: adjust the temperature to 130-140℃ and stir the reaction for 3-4 hours, then raise the temperature to 150-165℃ and maintain it for 2-3 hours.

5. The method for preparing a high-strength, low-density epoxy SMC composite material according to claim 1, characterized in that, In step (2), the etching solution is obtained by mixing ammonium fluoride with a mass concentration of 38%-40% and hydrofluoric acid with a mass concentration of 5.5%-8.5% in a volume ratio of (4-5):(1-2).

6. The method for preparing a high-strength, low-density epoxy SMC composite material according to claim 1, characterized in that, In step (3), the average particle size of montmorillonite is 0.5-1 μm; The aluminum hydroxide has an average particle size of 30-50 nm. The average particle size of the magnesium hydroxide is 20-30 nm.

7. A high-strength, low-density epoxy SMC composite material prepared by any one of the preparation methods described in claims 1-6.

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