Setting agent, benzoxazine resin-based composite material and preparation method of benzoxazine resin-based composite material

Abstract

The invention discloses a setting agent, a benzoxazine resin-based composite material and a preparation method, and belongs to the technical field of composite materials. The setting agent comprises benzoxazine matrix resin, a composite toughening agent and a diluent, wherein the composite toughening agent is composed of an oxazine ring modified thermosetting compound and a thermoplastic compound. Dissolving and diluting the setting agent with an organic solvent to obtain a setting agent solution, and brushing the surface of the inorganic fiber fabric with the setting agent solution for fabric setting; and completely infiltrating the benzoxazine matrix resin in a glue injection tank under constant pressure between the shaped fabric and fabric layers, setting the pressure difference between the outlet and the inlet of the glue injection tank, and curing under the state of keeping the pressure difference to obtain the benzoxazine resin matrix composite material. The setting agent can improve the interlayer toughness of the benzoxazine resin-based composite material under the condition of not influencing other properties.

Description

Technical Field

[0001] The invention relates to a setting agent, a benzoxazine resin-based composite material and a preparation method, and belongs to the technical field of composite materials. Background Art

[0002] The resin transfer molding (RTM) process does not require the preparation of prepregs. The fiber or fabric preform is placed in a closed mold, and then the resin matrix is ​​directly injected to finally obtain a composite part with excellent comprehensive properties. Benzoxazine resin is a new type of phenolic resin that maintains excellent heat resistance. Low molecular weight, low viscosity and good solubility make it suitable for RTM process.

[0003] However, there are still some problems in the preparation and application of high-performance benzoxazine RTM composites. Due to the requirement of low viscosity of the matrix resin in the RTM process, the matrix benzoxazine resin generally has a high-rigidity molecular main chain, resulting in low elongation at break of its cured product, making the interlayer toughness of the composite material low. In addition, the high-temperature setting agents suitable for the RTM process are concentrated in resin systems such as bismaleimide and cyanate ester, which are relatively brittle and have difficulty in co-curing with the matrix benzoxazine resin.

[0004] At present, there are two main strategies for improving interlayer toughness of benzoxazine RTM composites: bulk toughening and interlayer toughening. The main methods of bulk toughening include: copolymer toughening of thermosetting molecules such as epoxy, rubber elastomer toughening, and thermoplastic resin blending toughening. Bulk toughening can improve the flexibility of molecular chains or form a phase separation structure, thereby enhancing the energy absorption capacity. However, toughening of the matrix benzoxazine will increase the viscosity of the matrix resin, making it difficult to inject glue, and at the same time reduce the glass transition temperature of the polymer, affecting its heat resistance. The method of interlayer toughening is to concentrate the toughening components between the fiber layers. The main methods include: macroscopically uniformly distributing and fixing the thermoplastic particles on the fabric, spinning the thermoplastic components into fibers and then mixing them into the reinforcement fabric. It does not affect the viscosity of the matrix resin, and the toughening effect is achieved by melting the thermoplastic components between the layers during the thermal curing stage and diffusing and mixing with the thermosetting resin. However, this method is difficult to accurately control the phase structure of thermoplastic / thermosetting components, and more thermoplastic components (15% to 30%) need to be added between layers to achieve a good toughening effect. Since the thermoplastic component has high viscosity and poor compatibility with the matrix resin, it affects the void ratio of the preform, making it difficult for the matrix resin to flow, resulting in a long injection time and easy impregnation or uneven impregnation. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a setting agent, a benzoxazine resin-based composite material and a preparation method. The setting agent can improve the interlaminar toughness of the benzoxazine resin-based composite material without affecting other properties.

[0006] To achieve the above object, the present invention adopts the following technical solution:

[0007] A setting agent comprises the following components by weight: 10 to 50 parts of benzoxazine matrix resin, 30 to 60 parts of composite toughening agent, and 10 to 15 parts of diluent; wherein the composite toughening agent is composed of a thermosetting compound and a thermoplastic compound modified with an oxazine ring.

[0008] Furthermore, the benzoxazine matrix resin includes one or more combinations of diphenol-type benzoxazine and diamine-type benzoxazine.

[0009] Furthermore, in the composite toughening agent, the oxazine ring-modified thermosetting compound accounts for 15 to 30 parts by weight, and the thermoplastic compound accounts for 15 to 30 parts by weight.

[0010] Furthermore, the oxazine ring-modified thermosetting compound is an oxazine ring-modified molecule with a flexible long chain, and the structural formula is as follows:

[0011]

[0012] Wherein, n is 3 to 6; R1 and R2 are one of hydrogen and alkyl.

[0013] Furthermore, the thermoplastic compound is one or more of polysulfone, polyetherketone, polyphenylene ether, polyamide, and polyurethane.

[0014] Furthermore, the diluent is a mixture of epoxy resin and benzaldehyde, and the epoxy resin is glycidyl ether, glycidyl ester or glycidyl amine.

[0015] A method for preparing a setting agent comprises the following steps:

[0016] (1) heating a thermoplastic compound to raise its temperature, adding a high boiling point acid and adjusting the pH to acidic, stirring under nitrogen protection, then adding an oxazine ring-modified thermosetting compound, continuing to stir, and cooling to obtain a composite toughening agent;

[0017] (2) Adding a benzoxazine matrix resin, a composite toughening agent and a diluent into a reactor, heating and stirring the reactor under nitrogen protection, and then cooling the reactor to obtain a solid qualitative agent.

[0018] Furthermore, in step (1), the thermoplastic compound is heated to 100-150° C. and the pH is adjusted to 2-6.

[0019] Furthermore, after adding the high boiling point acid in step (1), stirring is carried out for 2 to 10 hours under nitrogen protection, so that the difference in solubility parameters between the treated thermoplastic compound and the benzoxazine matrix resin is greater than the difference in solubility parameters between the oxazine ring-modified thermosetting compound and the benzoxazine matrix resin.

[0020] Furthermore, after adding the oxazine ring-modified thermosetting compound in step (1), stirring is continued for 2 to 8 hours, and then the temperature is lowered to 30 to 50° C. to obtain a composite toughening agent solid.

[0021] Furthermore, in step (2), the temperature is raised to 90-100° C., stirred for 2-5 hours, and then cooled to 30-50° C.

[0022] A method for preparing a benzoxazine resin-based composite material comprises the following steps:

[0023] The setting agent is dissolved and diluted with an organic solvent to obtain a setting agent solution, the setting agent solution is brushed on the surface of the inorganic fiber fabric, and the solvent is removed at room temperature to set the fabric;

[0024] The benzoxazine matrix resin is completely infiltrated into the shaped fabric and the fabric layers under constant pressure in a glue injection tank, a pressure difference is set between the outlet and the inlet of the glue injection tank, and the curing is carried out while maintaining the pressure difference to obtain a benzoxazine resin-based composite material.

[0025] Furthermore, the organic solvent is one or more of acetone, ethanol, and ethylene glycol; the mass fraction of the setting agent solution is 60% to 70%, and the amount of the setting agent solution is 10 to 40 g / m 2 .

[0026] Furthermore, the pressure difference between the inlet and outlet of the glue injection tank is set to 0.1-0.4 MPa, and curing is performed for 0.5-2 hours while maintaining the pressure difference. The curing temperature is 160-200° C. and the curing time is 4-16 hours.

[0027] The beneficial effects achieved by the present invention compared with the prior art are as follows:

[0028] (1) The present invention pre-treats the thermoplastic compound and utilizes polarity to form a composite toughening agent of a flexible thermosetting compound / thermoplastic compound containing oxazine side groups that is compatible at the molecular level. During the injection molding process of preparing the composite material, a pressure difference is set, and the principle of like dissolves like and stress induction are utilized to form a microphase structure of thermosetting / thermoplastic compound separation and thermoplastic molecule orientation, and the oriented microphase structure is further frozen during the curing process. The orientation control and freezing of the microphase structure can be achieved simultaneously during the injection molding and curing processes, and it has high universality, and can achieve a significant improvement in the interlayer toughness of the composite material using a small amount of composite toughening agent.

[0029] (2) The present invention develops a setting agent based on the composite toughening agent, and prepares a benzoxazine resin-based composite material based on the setting agent. The setting agent has good compatibility with the base benzoxazine resin and does not affect the injection and impregnation process of the base resin. At the same time, the setting agent can be connected to the cross-linked network of the base benzoxazine resin to ensure the integrity of the cross-linked network and does not affect the heat resistance of the benzoxazine composite material. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the process of preparing the benzoxazine resin-based composite material in an embodiment of the present invention. DETAILED DESCRIPTION

[0031] In order to make the various technical features and advantages or technical effects in the above technical solutions of the present invention more obvious and easy to understand, they are described in detail below with reference to the accompanying drawings.

[0032] Example 1

[0033] (1) Weigh 20 parts of hexapolymer polysulfone, heat to 125°C, add sulfonic acid, adjust the pH of the system to 3, and stir for 6 hours under nitrogen protection. Continue to add 20 parts of oxazine ring modified five-polymer long-chain molecules to the reactor, continue stirring for 5 hours, cool to 40°C, and obtain a solid. Use a crusher to crush to obtain a composite toughening agent powder. Add 50 parts of benzoxazine matrix resin, 40 parts of composite toughening agent and 10 parts of diluent (including 5 parts of bisphenol A diglycidyl ether and 5 parts of benzaldehyde) to the reactor, heat to 100°C, and stir for 4 hours under nitrogen protection. Cool to 40°C to obtain a solid. Prepare an acetone / ethanol mixed solvent (the volume ratio of acetone to ethanol is 1:1), add the above-mentioned setting agent solid (the content of setting agent in the solvent is 60%), and stir at a stirring speed of 500r / min for 10 minutes to obtain a setting agent solution.

[0034] (2) Apply the above coating to the surface of T700 carbon fiber twill fabric with a single layer thickness of 0.4 mm in batches, and apply a small amount of coating to the same position on the surface to slightly wet the surface of the fabric. The amount of setting agent solution is controlled to be 40 g / m 2 After spraying, the solvent is removed at room temperature to allow the fabric to set.

[0035] (3) 10 layers of carbon fiber twill fabric are stacked in sequence and placed in a flat mold for closing. The pressure in the mold is set to -0.2 MPa. When the glue is discharged from the glue outlet without generating bubbles, the injection time is recorded. The pressure of the glue inlet is further set to 0.2 MPa and the pressure of the glue outlet is -0.2 MPa, and the pressure is maintained for 0.5 h. After the injection is completed, the curing is continued while maintaining the pressure difference. The curing procedure is: curing at 170 ° C for 4 h, and finally curing at 190 ° C for 2 h. After curing, it is cooled to room temperature and demolded to obtain a benzoxazine resin-based composite material.

[0036] Example 2

[0037] (1) Weigh 15 parts of hexapolymer polysulfone, heat to 100°C, add sulfonic acid, adjust the pH of the system to 6, and stir for 2 hours under nitrogen protection. Continue to add 15 parts of oxazine ring modified five-polymerization long-chain molecules into the reactor, continue to stir for 2 hours, cool to 50°C, and obtain a solid. Use a crusher to crush to obtain a composite toughening agent powder. Add 10 parts of benzoxazine matrix resin, 30 parts of composite toughening agent and 12 parts of diluent (including 6 parts of bisphenol A diglycidyl ether and 6 parts of benzaldehyde) into the reactor, heat to 90°C, and stir for 5 hours under nitrogen protection. Cool to 50°C to obtain a solid. Prepare an acetone / ethanol mixed solvent (the volume ratio of acetone to ethanol is 1:1), add the above-mentioned setting agent solid (the content of setting agent in the solvent is 65%), and stir at a stirring speed of 500r / min for 12 minutes to obtain a setting agent solution.

[0038] (2) Apply the above coating to the surface of T700 carbon fiber twill fabric with a single layer thickness of 0.4 mm in batches, and apply a small amount of coating to the same position on the surface to slightly wet the surface of the fabric. The amount of setting agent solution is controlled to be 10 g / m2. After spraying, remove the solvent at room temperature to set the fabric.

[0039] (3) 10 layers of carbon fiber twill fabric are stacked in sequence and placed in a flat mold for closing. The pressure in the mold is set to -0.2 MPa. When the glue is discharged from the glue outlet without generating bubbles, the injection time is recorded. The pressure of the glue inlet is further set to 0.1 MPa and the pressure of the glue outlet is -0.2 MPa, and the pressure is maintained for 1 hour. After the injection is completed, the curing is continued while maintaining the pressure difference. The curing procedure is: curing at 160°C for 2 hours, and finally curing at 200°C for 2 hours. After curing, it is cooled to room temperature and demolded to obtain a benzoxazine resin-based composite material.

[0040] Example 3

[0041] (1) Weigh 30 parts of hexapolymer polysulfone, heat to 150°C, add sulfonic acid, adjust the pH of the system to 2, and stir under nitrogen protection for 10 hours. Continue to add 30 parts of oxazine ring modified five-polymerization long-chain molecules into the reactor, continue to stir for 8 hours, cool to 30°C, and obtain a solid. Use a crusher to crush to obtain a composite toughening agent powder. Add 30 parts of benzoxazine matrix resin, 60 parts of composite toughening agent and 15 parts of diluent (including 8 parts of bisphenol A diglycidyl ether and 7 parts of benzaldehyde) into the reactor, heat to 95°C, and stir for 2 hours under nitrogen protection. Cool to 30°C to obtain a solid. Prepare an acetone / ethanol mixed solvent (the volume ratio of acetone to ethanol is 1:1), add the above-mentioned setting agent solid (the content of setting agent in the solvent is 70%), and stir at a stirring speed of 500r / min for 10 minutes to obtain a setting agent solution.

[0042] (2) Apply the above coating to the surface of T700 carbon fiber twill fabric with a single layer thickness of 0.4 mm in batches, and apply a small amount of coating to the same position on the surface to slightly wet the surface of the fabric. The amount of setting agent solution is controlled to be 30 g / m 2 After spraying, the solvent is removed at room temperature to allow the fabric to set.

[0043] (3) 10 layers of carbon fiber twill fabric are stacked in sequence and placed in a flat mold for closing. The pressure in the mold is set to -0.2 MPa. When the glue is discharged from the glue outlet without generating bubbles, the injection time is recorded. The pressure of the glue inlet is further set to 0.2 MPa and the pressure of the glue outlet is -0.2 MPa, and the pressure is maintained for 2 h. After the injection is completed, the curing is continued while maintaining the pressure difference. The curing procedure is: curing at 160 ° C for 8 h, and finally curing at 180 ° C for 8 h. After curing, it is cooled to room temperature and demolded to obtain a benzoxazine resin-based composite material.

[0044] Comparative Example 1

[0045] The preparation method of Comparative Example 1 is substantially the same as that of Example 1, except that the composite toughening agent is not prepared. The benzoxazine base resin is 90 parts by mass, and the diluent is 10 parts by mass.

[0046] Comparative Example 2

[0047] The preparation method of Comparative Example 2 is substantially the same as that of Example 1, except that the composite toughening agent is not prepared. The benzoxazine base resin is 50 parts by mass, the hexapolymer polysulfone is 40 parts by mass, and the diluent is 10 parts by mass.

[0048] The above examples and comparative examples recorded the injection time during the molding process, and tested the glass transition temperature, line ablation rate, porosity, flexural strength, interlaminar shear strength and impact damage tolerance (CAI value) of the obtained benzoxazine resin-based composite material. The results are shown in Table 1.

[0049] Table 1 Typical values ​​of injection time during molding process and properties of benzoxazine resin-based composite materials

[0050]

[0051] It can be seen from Table 1 that the interlayer toughness of the benzoxazine resin-based composite material prepared in the present invention is greatly improved, while other mechanical properties, heat resistance, molding processability, ablation performance, and interlayer molding quality are not affected.

[0052] Although the present invention has been disclosed as above by way of embodiments, it is not intended to limit the present invention. Appropriate modifications or equivalent substitutions of the technical solutions of the present invention made by ordinary technicians in the field should all be included in the protection scope of the present invention. The protection scope of the present invention shall be based on what is defined in the claims.

Claims

1. A setting agent, characterized in that The invention comprises the following components by weight: 10 to 50 parts of benzoxazine matrix resin, 30 to 60 parts of composite toughening agent and 10 to 15 parts of diluent; wherein the composite toughening agent is composed of thermosetting compound and thermoplastic compound modified by oxazine ring.

2. The setting agent according to claim 1, characterized in that The benzoxazine-based resin includes one or more combinations of diphenol-type benzoxazine and diamine-type benzoxazine.

3. The setting agent according to claim 1, characterized in that In the composite toughening agent, the oxazine ring-modified thermosetting compound is 15 to 30 parts by weight, and the thermoplastic compound is 15 to 30 parts by weight; The oxazine ring-modified thermosetting compound is an oxazine ring-modified molecule with a flexible long chain, and the structural formula is as follows: Wherein, n is 3 to 6; R1 and R2 are one of hydrogen and alkyl; The thermoplastic compound is one or more of polysulfone, polyetherketone, polyphenylene ether, polyamide and polyurethane.

4. The setting agent according to claim 1, characterized in that The diluent is a mixture of epoxy resin and benzaldehyde, and the epoxy resin is glycidyl ether, glycidyl ester or glycidyl amine.

5. A method for preparing the setting agent according to any one of claims 1 to 4, characterized in that: The steps include: (1) heating a thermoplastic compound to raise its temperature, adding a high boiling point acid and adjusting the pH to acidic, stirring under nitrogen protection, then adding an oxazine ring-modified thermosetting compound, continuing to stir, and cooling to obtain a composite toughening agent; (2) Adding a benzoxazine matrix resin, a composite toughening agent and a diluent into a reactor, heating and stirring the reactor under nitrogen protection, and then cooling the reactor to obtain a solid qualitative agent.

6. The preparation method according to claim 5, characterized in that: In step (1), the thermoplastic compound is heated to 100-150° C., and the pH is adjusted to 2-6; after adding the high boiling point acid, stirring is carried out under nitrogen protection for 2-10 hours; after adding the thermosetting compound modified with the oxazine ring, stirring is continued for 2-8 hours, and then the temperature is reduced to 30-50° C. to obtain a composite toughening agent solid.

7. The preparation method according to claim 5, characterized in that: In step (2), the temperature is raised to 90-100° C., stirred for 2-5 h, and then cooled to 30-50° C.

8. A method for preparing a benzoxazine resin-based composite material, characterized in that: The steps include: The setting agent according to any one of claims 1 to 4 is dissolved and diluted with an organic solvent to obtain a setting agent solution, the setting agent solution is brushed on the surface of the inorganic fiber fabric, and the solvent is removed at room temperature to set the fabric; The benzoxazine matrix resin is completely infiltrated into the shaped fabric and the fabric layers under constant pressure in a glue injection tank, a pressure difference is set between the outlet and the inlet of the glue injection tank, and the curing is carried out while maintaining the pressure difference to obtain a benzoxazine resin-based composite material.

9. The preparation method according to claim 8, characterized in that: The organic solvent is one or more of acetone, ethanol, and ethylene glycol; the mass fraction of the setting agent solution is 60% to 70%, and the amount of the setting agent solution is 10 to 40 g / m 2 .

10. The preparation method according to claim 8, characterized in that: The pressure difference between the inlet and outlet of the glue injection tank is set to 0.1-0.4 MPa, and the curing is carried out for 0.5-2 hours while maintaining the pressure difference. The curing temperature is 160-200° C. and the curing time is 4-16 hours.

Images