Benzoxazine resin system, its preparation method and method for preparing composite material

Abstract

The present invention discloses a benzoxazine resin system, its essential preparation method and a method for preparing a composite material, belonging to the field of composite materials. The raw material components of the benzoxazine resin system include benzoxazine monomers, thermosetting modifiers, diluents and inorganic filler particles, and have properties such as low viscosity, high temperature resistance, ablation resistance and small shrinkage, and are suitable for composite material molding as a matrix resin. The preparation method of the benzoxazine resin system optimizes the preparation conditions, so that the prepared benzoxazine resin system has excellent ablation resistance and good mechanical properties. The composite material prepared by this method for preparing a composite material has excellent compressive strength, flexural strength and interlaminar shear strength.

Description

Technical Field

[0001] The present invention relates to a low-viscosity ablative-resistant benzoxazine resin system, a preparation method thereof, and a method for preparing a composite material, and belongs to the field of composite materials. Background Art

[0002] Resin-based ablative materials have currently become one of the most mature and widely used thermal protection material systems. With the rapid development of high-tech systems such as rocket engines, missiles, and space vehicles, higher requirements are put forward for the ablative resistance performance and processing performance of ablative materials. Benzoxazine resin can undergo ring-opening polymerization reaction to form a phenolic-like network structure without releasing small molecules, having obvious advantages in processing and molding. Moreover, its raw materials are easily available and the cost is low, so it has become a good choice for thermal protection material systems.

[0003] At present, the application research of benzoxazine resin in composite materials mainly focuses on the prepreg resin matrix and is suitable for autoclave process or compression molding process. Compared with the autoclave process or compression molding process, the RTM process avoids the complex mechanical or semi-mechanical resin impregnation process, and the subsequent curing is carried out in an oven without the need for an energy-consuming autoclave or press, having significant advantages in achieving low cost. Therefore, it is necessary to expand the benzoxazine resin system applicable to the RTM process, which requires the resin system to have low viscosity and a long process window.

[0004] Chinese invention patent CN03117779.4 discloses a modified benzoxazine resin applicable to RTM. However, the reduction of its viscosity is mainly achieved through the introduction of reactive or non-reactive side groups and complex functional group reactions and catalytic reactions, with complex regulation, high cost, and narrow applicability. In addition, the residual carbon rate of the commonly used benzoxazine matrix after ablation is still relatively low, generally about 50% at 800 °C, and the ablation performance needs to be further improved.

[0005] Therefore, how to reduce the viscosity of the benzoxazine resin system, improve the ablative resistance performance of the resin system, and further improve the mechanical properties of the composite material is an urgent problem to be solved. Summary of the Invention

[0006] The object of the present invention is to overcome the existing deficiencies and provide a benzoxazine resin system having properties of low viscosity, high temperature resistance, ablative resistance, and small shrinkage, and being suitable for composite material molding as a matrix resin. The object of the present invention is also to propose a preparation method of a benzoxazine resin system, which makes the prepared benzoxazine resin system have excellent ablative resistance performance and good mechanical properties by optimizing the preparation conditions. The object of the present invention is also to propose a method for preparing a composite material with a benzoxazine resin system, and the prepared composite material has excellent compressive strength, flexural strength, and interlaminar shear strength.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0008] A benzoxazine resin system, whose raw material components, calculated by weight, include 50-80 parts of benzoxazine monomer, 15-25 parts of thermosetting modifier, 3-15 parts of diluent and 2-10 parts of inorganic filler particles.

[0009] Furthermore, the benzoxazine monomer is a bifunctional benzoxazine compound component, which plays a leading role in the material performance, and is specifically at least one of the diamine-type benzoxazines, and the structural formula is as follows:

[0010]

[0011] Wherein, X is one of -CH2-, -SO2-, and -O-; R1 and R2 are one of hydrogen and alkyl.

[0012] Furthermore, the thermosetting modifier can adjust the viscosity of the resin and improve the processability of the resin system, and is specifically at least one of the linear phenolic resins, and the structural formula is as follows:

[0013]

[0014] Wherein, R1 and R2 are one of hydrogen and alkyl.

[0015] Furthermore, the diluent can further adjust the processability of the resin, and is specifically at least one of the following compounds:

[0016]

[0017] R1=-CF3, -CN or -NO2

[0018]

[0019] Furthermore, the inorganic filler particles can improve the ablation resistance of the resin, and are specifically at least one of TiO2, La2O3, and ZrO2.

[0020] A method for preparing a benzoxazine resin system comprises the following steps:

[0021] 1) grinding and dispersing 50 to 80 parts by weight of benzoxazine and 2 to 10 parts by weight of inorganic filler particles in a ball mill, then subjecting the mixture to a heat treatment in an oven, and then transferring the mixture to a three-roll mill for dispersion to obtain a resin system;

[0022] 2) Place the resin system in a stirring kettle, then add 15 - 25 parts by mass of thermosetting modifier and 3 - 15 parts by mass of diluent, heat and stir evenly, and obtain the benzoxazine resin system after cooling.

[0023] A method for preparing a composite material using a benzoxazine resin system, comprising the following steps:

[0024] 1) Prepare a preform using fibers;

[0025] 2) Keep the benzoxazine resin system molten at a temperature of 70 - 110 °C, and impregnate the preform under a pressure of 0.1 - 0.5 MPa to obtain an impregnated system;

[0026] 3) Cure and mold the impregnated system in an oven using the RTM curing process, and then cool to room temperature to obtain the composite material.

[0027] Further, the preform is a premix, plain weave fabric or 2.5D fabric.

[0028] Further, the fibers are selected from at least one of carbon fiber, glass fiber, quartz fiber, or basalt fiber.

[0029] Further, the weight percentage of the fibers in the composite material is 60% - 65%.

[0030] Further, the RTM curing process is step - wise temperature - rising curing, the curing temperature is 140 - 200 °C, and the curing time is 4 - 10 h.

[0031] The beneficial effects of the present invention are:

[0032] (1) By introducing and blending a simple small - molecule active diluent instead of complex chemical structure modification, the present invention can effectively reduce the melt viscosity of the benzoxazine resin system and increase the process window time; in the present invention, the melt viscosity of the benzoxazine resin system is less than 400 mPa·s, and the holding time is greater than 6 hours, meeting the requirements of resin for liquid molding of composite materials.

[0033] (2) By adding a small amount of ablative - resistant inorganic filler particles and performing pre - treatment with the benzoxazine resin system in advance, the compatibility of the organic / inorganic system is greatly improved. The addition of inorganic filler particles does not affect the RTM processability of the benzoxazine resin system, but can significantly improve the ablation performance of the benzoxazine resin system, and the char residue rate at 800 °C is greater than 55%.

[0034] (3) By reasonably selecting the resin composition, the present invention reduces the injection temperature at an appropriate resin viscosity. Injection can be carried out at 80-90 °C, which has good processability, reduces the molding difficulty, and is convenient to operate. On the basis of excellent ablation resistance, the resin system still has good mechanical properties and can be used for integral structures. Detailed implementation mode

[0035] To deepen the understanding of the present invention, the following will further describe the present invention in detail in conjunction with embodiments. These embodiments are only used to explain the present invention and do not limit the protection scope of the present invention.

[0036] Example 1:

[0037] This example discloses a benzoxazine resin system. Its raw material components are calculated by mass fraction and include 50 parts of diamine-type benzoxazine resin monomer TDS-BOZ, 25 parts of linear phenolic resin, 15 parts of diluent, and 10 parts of TiO2.

[0038] This example discloses a preparation method of a benzoxazine resin system. The preparation steps are as follows: Grind and disperse 50 parts of diamine-type benzoxazine resin monomer TDS-BOZ and 10 parts of TiO2 in a ball mill, and then transfer them to a three-roll mill for further dispersion after heat treatment in an oven. Place the above resin system in a stirring kettle, add 25 parts of linear phenolic resin and 15 parts of diluent, and mechanically stir at 100 °C for 1 hour. After the resin is stirred evenly, cool it to a suitable viscosity to obtain the TDS-type benzoxazine resin system. Conduct a rotary viscometer test and a thermogravimetric (TG) test on the TDS-type benzoxazine resin system. The isothermal rheological properties at 90 °C are shown in Table 1, and the char yield data at 800 °C are shown in Table 2.

[0039] This example discloses a method for preparing a composite material with a benzoxazine resin system. Use the RTM curing process to prepare a carbon fiber-reinforced benzoxazine resin matrix composite laminate, and the weight percentage of carbon fiber in the composite material is 60%. The preparation process is as follows: At 90 °C and 0.4 MPa, impregnate the T700 plain weave carbon cloth with the TDS-type benzoxazine resin system, keep it at 140 °C for 1 h, continue to heat up to 180 °C, cure for 6 h, and then cool to room temperature to prepare the composite material. Cut the composite material into standard specimens according to regulations and test the tensile strength, bending strength, and interlaminar shear strength of the composite material on a universal material testing machine. The performance data are shown in Table 3.

[0040] Example 2:

[0041] This example discloses a benzoxazine resin system. Its raw material components are calculated by mass fraction and include 66 parts of diamine-type benzoxazine resin monomer TDS-BOZ, 20 parts of linear phenolic resin, 10 parts of diluent, and 4 parts of TiO2.

[0042] This embodiment discloses a method for preparing a benzoxazine resin system, and the preparation steps are as follows: grind and disperse 66 parts of diamine benzoxazine resin monomer TDS-BOZ and 4 parts of TiO2 in a ball mill, heat treat in an oven, and then transfer to a three-roller machine for dispersion. The above resin system is placed in a stirring kettle, and then 20 parts of linear phenolic resin and 10 parts of diluent are added, and mechanically stirred at 100°C for 1 hour. After the resin is stirred evenly, it is cooled to a suitable viscosity to obtain a TDS-type benzoxazine resin system. The resin prepared by the TDS-type benzoxazine resin system is subjected to a drum viscosity test and a TG test. The isothermal rheological properties at 90°C are shown in Table 1, and the carbon residue rate data at 800°C are shown in Table 2.

[0043] This embodiment discloses a method for preparing a composite material using a benzoxazine resin system, and a carbon fiber reinforced benzoxazine resin-based composite laminate is prepared using an RTM curing process, and the weight percentage of carbon fiber in the composite material is 63%. The preparation process is: at 70°C and 0.5MPa, T700 plain carbon cloth is impregnated with a TDS type benzoxazine resin system, kept at 140°C for 1h, continued to heat to 200°C, cured for 3h, and then cooled to room temperature to prepare a composite material. The composite material is cut into standard specimens according to regulations, and the tensile strength, flexural strength and interlaminar shear strength of the composite material are tested on a universal material testing machine. The performance data are shown in Table 3.

[0044] Embodiment 3:

[0045] This embodiment discloses a benzoxazine resin system, the raw material components of which, calculated by weight, include 64 parts of diamine type benzoxazine resin monomer TDS-BOZ, 20 parts of linear phenolic resin, 10 parts of diluent and 6 parts of TiO2.

[0046] This embodiment discloses a method for preparing a benzoxazine resin system, and the preparation steps are as follows: grind and disperse 64 parts of diamine benzoxazine resin monomer TDS-BOZ and 6 parts of TiO2 in a ball mill, heat treat in an oven, and then transfer to a three-roller machine for dispersion. The above resin system is placed in a stirring kettle, and then 20 parts of linear phenolic resin and 10 parts of diluent are added, and mechanically stirred at 100°C for 1 hour. After the resin is stirred evenly, it is cooled to a suitable viscosity to obtain a TDS-type benzoxazine resin system. The TDS-type benzoxazine resin system is subjected to a drum viscosity test and a TG test. The isothermal rheological properties at 90°C are shown in Table 1, and the carbon residue rate data at 800°C are shown in Table 2.

[0047] This embodiment discloses a method for preparing a composite material using a benzoxazine resin system, and a carbon fiber reinforced benzoxazine resin-based composite laminate is prepared using an RTM curing process, and the weight percentage of carbon fiber in the composite material is 65%. The preparation process is: at 110°C and 0.1MPa, a TDS-type benzoxazine resin system is used to impregnate T700 plain carbon cloth, keep it at 140°C for 4h, continue to heat it to 180°C, cure it for 6h, and then cool it to room temperature to obtain a composite material. The composite material is cut into standard specimens according to regulations, and the tensile strength, flexural strength and interlaminar shear strength of the composite material are tested on a universal material testing machine. The performance data are shown in Table 3.

[0048] Embodiment 4:

[0049] This embodiment discloses a benzoxazine resin system, the raw material components of which, calculated by weight, include 66 parts of diamine type benzoxazine resin monomer TDS-BOZ, 18 parts of linear phenolic resin, 12 parts of diluent and 4 parts of TiO2.

[0050] This embodiment discloses a method for preparing a benzoxazine resin system, and the preparation steps are as follows: grind and disperse 66 parts of diamine benzoxazine resin monomer TDS-BOZ and 4 parts of TiO2 in a ball mill, heat treat in an oven, and then transfer to a three-roller machine for dispersion. The above resin system is placed in a stirring kettle, and then 18 parts of linear phenolic resin and 12 parts of diluent are added, and mechanically stirred at 100°C for 1 hour. After the resin is stirred evenly, it is cooled to a suitable viscosity to obtain a TDS-type benzoxazine resin system. The TDS-type benzoxazine resin system is subjected to a drum viscosity test and a TG test. The isothermal rheological properties at 90°C are shown in Table 1, and the carbon residue rate data at 800°C are shown in Table 2.

[0051] This embodiment discloses a method for preparing a composite material using a benzoxazine resin system, and a carbon fiber reinforced benzoxazine resin-based composite laminate is prepared using an RTM curing process, and the weight percentage of carbon fiber in the composite material is 63%. The preparation process is: at 100°C and 0.2MPa, a TDS type benzoxazine resin system is used to impregnate T700 plain carbon cloth, keep it at 150°C for 1h, continue to heat it to 180°C, cure it for 6h, and then cool it to room temperature to prepare a composite material. The composite material is cut into standard specimens according to regulations, and the tensile strength, bending strength and interlaminar shear strength of the composite material are tested on a universal material testing machine. The performance data are shown in Table 3.

[0052] Embodiment 5:

[0053] This embodiment discloses a benzoxazine resin system, the raw material components of which, calculated by weight, include 80 parts of diamine type benzoxazine resin monomer TDS-BOZ, 15 parts of linear phenolic resin, 3 parts of diluent and 2 parts of TiO2.

[0054] This embodiment discloses a preparation method of a benzoxazine resin system. The preparation steps are as follows: After grinding and dispersing 80 parts of a diamine-type benzoxazine resin monomer TDS-BOZ and 2 parts of TiO2 in a ball mill, heat treatment is carried out by heating the oven, and then it is transferred to a three-roll mill for further rolling and dispersing. Place the above resin system in a stirring kettle, add 15 parts of linear phenolic resin and 3 parts of diluent, and mechanically stir at 100 °C for 1 hour. After the resin is stirred evenly, cool it to a suitable viscosity to obtain a TDS-type benzoxazine resin system. Conduct a rotary viscometer test and a thermogravimetric (TG) test on the TDS-type benzoxazine resin system. The isothermal rheological properties at 90 °C are shown in Table 1, and the char residue rate data at 800 °C are shown in Table 2.

[0055] This embodiment discloses a method for preparing a composite material using a benzoxazine resin system. The resin transfer molding (RTM) curing process is used to prepare a carbon fiber-reinforced benzoxazine resin matrix composite laminate, and the weight percentage of carbon fiber in the composite material is 61%. The preparation process is as follows: At 90 °C and 0.3 MPa, impregnate the T700 plain weave carbon cloth with the TDS-type benzoxazine resin system, keep it at 140 °C for 1 h, continue to heat up to 180 °C, and cure for 6 h, and then cool to room temperature to prepare the composite material. Cut the composite material into standard specimens according to regulations, and test the tensile strength, flexural strength and interlaminar shear strength of the composite material on a universal material testing machine. The performance data are shown in Table 3.

[0056] As can be seen from Tables 1 to 3, the resin prepared by the present invention has a low viscosity and a high char residue rate. The resin prepared by the present invention can be cured using the RTM molding process, and the prepared composite material has excellent mechanical properties, indicating that the internal quality of the composite material is good.

[0057] Table 1 Isothermal Rheological Properties of Benzoxazine Resin System

[0058]

[0059] Table 2 Char Residue Rate of Cured Benzoxazine Resin

[0060]

[0061] Table 3 Properties of Benzoxazine Composite Material

[0062]

[0063]

[0064] The specific embodiments of the present invention disclosed above are intended to help understand the content of the present invention and implement it accordingly. Those of ordinary skill in the art can understand that various substitutions, changes, and modifications are possible without departing from the spirit and scope of the present invention. The present invention should not be limited to the content disclosed in the embodiments of this specification, and the protection scope of the present invention shall be subject to the scope defined by the claims.

Claims

1. A benzoxazine resin system, characterized in that, Calculated by mass fraction, its raw material components include 50-80 parts of benzoxazine monomer, 15-25 parts of thermosetting modifier, 3-15 parts of diluent and 2-10 parts of inorganic filler particles; the inorganic filler particles are anti-ablative inorganic filler particles; The benzoxazine monomer is a bifunctional benzoxazine compound, specifically at least one of diamine-type benzoxazines, and the structural formula is as follows: Wherein, X is one of -CH2-, -SO2-, -O-; R1 and R2 are one of hydrogen and alkyl; The thermosetting modifier is at least one of linear phenolic resins, and the structural formula is as follows: Wherein, R1 and R2 are one of hydrogen and alkyl; The diluent is at least one of the following compounds:

2. The benzoxazine resin system according to claim 1, wherein The inorganic filler particles are at least one of TiO2, La2O3, and ZrO2.

3. A method for preparing the benzoxazine resin system according to any one of claims 1-2, characterized in that, It includes the following steps: 1) Grind and disperse 50-80 parts by mass of benzoxazine and 2-10 parts by mass of inorganic filler particles in a ball mill, then perform heat treatment with temperature increase in an oven, and then continue to transfer to a three-roll mill for over-rolling dispersion to obtain a resin system; 2) Place the resin system in a stirring kettle, then add 15-25 parts by mass of thermosetting modifier and 3-15 parts by mass of diluent, heat and stir evenly, and obtain a benzoxazine resin system after cooling.

4. A method for preparing a composite material using the benzoxazine resin system according to any one of claims 1-2, characterized in that, It includes the following steps: 1) Prepare a preform using fibers; 2) Keep the benzoxazine resin system molten at a temperature of 70-110°C and impregnate the preform under a pressure of 0.1-0.5 MPa to obtain an impregnated system; 3) Cure and mold the impregnated system in an oven using the RTM curing process, and then cool to room temperature to obtain a composite material.

5. The method according to claim 4, wherein The preform is a premix, plain weave fabric or 2.5D fabric.

6. The method according to claim 4, characterized in that, The fiber is selected from at least one of carbon fiber, glass fiber, quartz fiber, or basalt fiber; the weight percentage of the fiber in the composite material is 60%-65%.

7. The method according to claim 4, wherein The RTM curing process is stepwise temperature increase curing, the curing temperature is 140-200°C, and the curing time is 4-10 h.

Images