Phenolic resin-based silicon-boron modified material as well as preparation method and application thereof

Abstract

The invention belongs to the field of phenolic resin, and particularly discloses a phenolic resin-based silicon-boron modified material as well as a preparation method and application of the phenolic resin-based silicon-boron modified material. Phenyltriethoxysilane monomers and hydroxymethyl phenol are blended and then subjected to in-situ prepolymerization to form an interpenetrating network structure; then boric acid is introduced to continuously participate in the chemical reaction to obtain highly reacted silicon-boron modified phenolic resin with special silicon-oxygen bonds and boron-oxygen bonds; the residual weight of the phenolic resin-based modified material is 63% and is much higher than that of traditional phenolic resin; the PFMM resin prepared by the invention can be kept stable at a higher temperature, has higher oxidation resistance, is suitable for a harsh thermal environment, and has higher compressive strength and breaking strength; and implementation of a forming process is facilitated. The resin content in the prepreg cloth can be accurately controlled through the integrated forming process; the porosity of the composite material is obviously reduced, and the mechanical property and the ablation property are optimized; and low-cost manufacturing can be achieved while integrated rapid forming is achieved.

Description

Technical Field

[0001] The invention relates to the field of phenolic resins, in particular to a phenolic resin-based silicon-boron modified material and a preparation method and application thereof. Background Art

[0002] Traditional phenolic resins, despite their excellent mechanical properties and high temperature resistance, are widely used in many fields. However, the limitations of their molecular structure lead to low thermal stability and residual carbon rate, high brittleness, and low crosslinking degree, which limits their application in the field of high-performance engineering materials. Therefore, with the improvement of scientific and technological levels and the growth of demand for high-performance materials, the modification of phenolic resins has become an inevitable trend. The modification aims to improve the heat resistance, toughness, and adhesion of phenolic resins and reduce their tendency to oxidize at high temperatures. Methods for modifying phenolic resin-based materials include chemical modification and physical modification. Chemical modification is achieved through hydroxyl etherification, epoxidation, or the introduction of components such as molybdenum, boron, phosphorus, and silicone. Physical modification improves resin performance by means of blending or the introduction of nanomaterials.

[0003] The traditional phenolic resin composite molding process has problems such as low efficiency and high cost. Therefore, the integrated rapid prototyping process came into being to improve production efficiency, reduce costs, and meet the needs of high-performance composite materials. The application of integrated rapid prototyping technology in the field of high-performance thermal protection such as solid rocket engine composite shells shows broad prospects and can meet the requirements of structural and functional integration. In recent years, domestic and foreign scholars have achieved a series of research results in the modification of phenolic resin, the development of new molding processes, and the application of integrated molding technology, which has promoted the development of phenolic resin integrated rapid prototyping technology. In the integrated molding technology, especially the hot melt adhesive film method, the hot melt characteristics of the modified phenolic resin are used to prepare the prepreg tape through melt coating, pressing and cooling under solvent-free conditions, thereby avoiding environmental pollution and physical harm to the operator. This method can accurately control the resin content, reduce the porosity of the composite material, and improve the mechanical properties.

[0004] Therefore, there is an urgent need to modify traditional phenolic resins to meet the needs of more demanding conditions in more occasions. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a phenolic resin-based silicon-boron modified material and a preparation method and application thereof.

[0006] To achieve the above object, the present invention is implemented according to the following technical solutions:

[0007] One of the purposes of the present invention is to provide a method for preparing a phenolic resin-based silicon-boron modified material, comprising the following steps:

[0008] S1. Phenol, formaldehyde, boric acid and silicon components were weighed in a molar ratio of 1:1.2:0.2:0.1, phenol and formaldehyde were placed in a three-necked flask, and then ammonia water was added as a catalyst, and mechanical stirring was performed at 70° C. for 1.5 hours. After the reaction was completed, the water in the reaction system was removed by a vacuum dehydration process to obtain a preliminary product of hydroxymethylphenol (SA);

[0009] S2, dispersing the silicon component monomer in ethanol, and adjusting the pH to 6-6.5 with acetic acid to form a uniform solution, the solution is mixed with hydroxymethylphenol solution under strong stirring, and then reacted under reflux conditions of 100° C. for 1 hour to ensure that the silicon component and SA are fully reacted;

[0010] S3. Slowly add boric acid (BA) dissolved in ethanol to the above mixture, and react under reflux conditions at 100° C. for 2 hours. After the reaction is completed, remove the solvent and residual water to obtain a phenolic resin-based silicon-boron modified material PFMM.

[0011] Furthermore, the silicon component is phenyltriethoxysilane or tetraethoxysilane.

[0012] The second object of the present invention is to provide a phenolic resin-based silicon-boron modified material prepared by the above method.

[0013] The third object of the present invention is to provide an application of a phenolic resin-based silicon-boron modified material in the preparation of high-performance phenolic resin cured engineering materials, comprising the following steps:

[0014] (1) heating the phenolic resin-based silicon boron modified material to 95-135° C., at which time the viscosity of the phenolic resin-based silicon boron modified material is less than 1000 mPa·s;

[0015] (2) Weaving and molding: The phenolic resin-based silicon boron modified material film is woven into samples of corresponding specifications and sizes. The pressing process is as follows: the room temperature is raised to 90°C, kept warm for 30 minutes, and the air is released once; then a full pressure of 30 tons is applied, the temperature is raised to 130°C, and the temperature is kept warm for 1 hour; then the temperature is raised to 160°C, and the temperature is kept warm for 1 hour; finally, the temperature is raised to 170°C, and the temperature is kept warm for 30 minutes. After natural cooling, the material is taken out to prepare high-performance phenolic resin cured engineering materials.

[0016] Compared with the prior art, the present invention prepolymerizes phenyltriethoxysilane monomer and hydroxymethylphenol in situ to form an interpenetrating network structure, and then introduces boric acid to continue to participate in the chemical reaction to obtain a highly reactive silicon-boron modified phenolic resin with special silicon-oxygen bonds and boron-oxygen bonds. The residual weight of this phenolic resin-based modified material is 63%, which is much higher than that of traditional phenolic resin. In the integrated molding process of PFMM, the composite process conditions of phenolic film resin and carbon fiber are first studied, and then the hot melt prepreg / carbon cloth composite material is prepared by tearing film, baking material, loading material, and film forming procedures. The PFMM resin prepared by the present invention can remain stable at higher temperatures, has stronger anti-oxidation and ablation ability, is suitable for more severe thermal environments, and is more conducive to the implementation of molding processes. The integrated molding process can achieve precise control of the resin content in the prepreg; significantly reduce the porosity of the composite material, and optimize the mechanical properties and ablation properties; and can achieve low-cost manufacturing while achieving integrated rapid molding. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 These are the TGA and DTG curves of the phenolic resin-based silicon-boron modified materials of Examples 1 and 2.

[0018] Figure 2 The DSC curves of the phenolic resin-based silicon-boron modified materials of Examples 1 and 2 during curing. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments. The specific embodiments described herein are only used to explain the present invention and are not used to limit the invention.

[0020] Example 1

[0021] Raw materials: phenol, formaldehyde, phenyltriethoxysilane (PTS), boric acid, ammonia, acetic acid, ethanol.

[0022] The process flow of synthesizing PFMM (boron-silicon modified phenolic polymer) can be described in detail according to the following steps:

[0023] (a) Based on a large number of previous repeated experiments, we determined the optimal molar ratio for the synthesis of PFMM, which is 1:1.2:0.2:0.1 for phenol:formaldehyde:boric acid:phenyltriethoxysilane (PTS). These ratios are accurately calculated based on experimental data to ensure the high efficiency of the reaction and the stability of the product.

[0024] (b) Under laboratory conditions, accurately measured phenol and paraformaldehyde are placed in a three-necked flask, and then ammonia water is added as a catalyst. The mixture is mechanically stirred at 70°C for 1.5 hours to promote the uniform reaction. After this step is completed, the water in the reaction system is removed by a vacuum dehydration process to obtain the initial product hydroxymethylphenol.

[0025] (c) Next, PTS, acetic acid and ethanol were mixed and the pH was adjusted to about 6.5 to form a uniform solution. The solution was mixed with hydroxymethylphenol solution under strong stirring and then reacted under reflux conditions at about 100° C. for 1 hour to ensure that PTS and SA were fully reacted.

[0026] (d) Slowly add boric acid (BA) dissolved in ethanol to the above mixture and continue to react under the same reflux conditions for 2 hours. After the reaction is completed, remove the solvent and residual water by appropriate methods to obtain the final product PFMM. This step is the key to the synthesis of PFMM because it involves the reaction of boric acid with hydroxymethylphenol and PTS to ultimately form the desired boron-oxygen bonds and silicon-oxygen bonds.

[0027] The entire synthesis process requires precise control of reaction conditions, including temperature, pH value and reaction time, to ensure the quality and yield of the product. Through this method, PFMM with specific chemical structure and properties was successfully synthesized, providing basic materials for further application research. The specific reaction formula is as follows.

[0028]

[0029] The phenolic resin-based silicon-boron modified material of this embodiment can be used to prepare high-performance phenolic resin cured engineering materials, and the specific operations are as follows:

[0030] (a) Determination of processing temperature and time: The curing reaction characteristics and gel characteristics of the resin were analyzed using a rheometer and a differential scanning calorimeter (DSC) to determine the optimal processing temperature and time.

[0031] (b) Establishing viscosity-temperature-time model: Through chemical rheology and double Arrhenius theory, a viscosity-temperature-time function relationship model of the resin is established, which can be used to predict the low viscosity platform of the film resin and guide the preparation of hot melt adhesive film.

[0032] (c) Preparation of resin prepreg: To ensure that the resin can fully impregnate the fiber, the temperature of the resin impregnated fiber preform should be between 95 and 135°C, at which time the viscosity of the resin is less than 1000 mPa·s.

[0033] (d) Weaving and molding process: Finally, we weave the PFMM film into samples of corresponding specifications and sizes, and perform rapid hot pressing molding under certain temperature and pressure conditions to prepare high-performance samples with specific sizes and structures.

[0034] Example 2

[0035] Raw materials: phenol, formaldehyde, tetraethoxysilane (TEOS), boric acid, ammonia, acetic acid, ethanol.

[0036] The process flow of synthesizing PFMM can be described in detail according to the following steps:

[0037] (a) First, based on a large number of previous repeated experiments, we determined the optimal molar ratio for synthesizing PFMM, which is 1:1.2:0.2:0.1 for phenol:formaldehyde:boric acid:tetraethoxysilane. These ratios were accurately calculated based on experimental data to ensure the high efficiency of the reaction and the stability of the product.

[0038] (b) Under laboratory conditions, accurately measured phenol and paraformaldehyde are placed in a three-necked flask, and then ammonia water is added as a catalyst. The mixture is mechanically stirred at 70°C for 1.5 hours to promote the uniform reaction. After this step is completed, the water in the reaction system is removed by a vacuum dehydration process to obtain the initial product hydroxymethylphenol.

[0039] (c) Next, tetraethoxysilane, acetic acid and ethanol were mixed and the pH was adjusted to about 6 to form a uniform solution. The solution was mixed with hydroxymethylphenol solution under strong stirring and then reacted under reflux conditions at about 100° C. for 1 hour to ensure that tetraethoxysilane and SA were fully reacted.

[0040] (d) Slowly add boric acid (BA) dissolved in ethanol to the above mixture and continue to react under the same reflux conditions for 2 hours. After the reaction is completed, remove the solvent and residual water by appropriate methods to obtain the final product PFMM. This step is the key to the synthesis of PFMM because it involves the reaction of boric acid with hydroxymethylphenol and PTS to ultimately form the desired boron-oxygen bond and silicon-oxygen bond. The specific reaction formula is as follows.

[0041]

[0042] The phenolic resin-based silicon-boron modified material of this embodiment can be used to prepare high-performance phenolic resin cured engineering materials, and the specific operations are as follows:

[0043] (a) Determination of processing temperature and time: The curing reaction characteristics and gel characteristics of the resin were analyzed using a rheometer and a differential scanning calorimeter (DSC) to determine the optimal processing temperature and time.

[0044] (b) Establishing viscosity-temperature-time model: Through chemical rheology and double Arrhenius theory, a viscosity-temperature-time function relationship model of the resin is established, which can be used to predict the low viscosity platform of the film resin and guide the preparation of hot melt adhesive film.

[0045] (c) Preparation of resin prepreg: To ensure that the resin can fully impregnate the fiber, the temperature of the resin impregnated fiber preform should be between 95 and 135°C, at which time the viscosity of the resin is less than 1000 mPa·s.

[0046] (d) Weaving and molding process: Finally, we weave the PFMM film into samples of corresponding specifications and sizes, and perform rapid hot pressing molding under certain temperature and pressure conditions to prepare high-performance samples with specific sizes and structures.

[0047] The phenolic resin-based silicon-boron modified materials prepared in Example 1 and Example 2 were respectively tested to obtain TGA and DTG curves as shown in Figure 1 As shown by Figure 1 It can be seen that the residual weight of Example 1 is 63%, and the residual weight of Example 2 is 62.5%, which are much higher than the residual carbon ratio of traditional phenolic resin, indicating the successful preparation of phenolic resin-based silicon-boron modified materials.

[0048] The DSC curves of the phenolic resin-based silicon-boron modified materials prepared in Example 1 and Example 2 when they are cured are as follows: Figure 2 As shown, right Figure 2 It can be seen that the curing temperatures of the phenolic resin-based silicon boron modified materials of Example 1 and Example 2 are 130°C and 168°C.

[0049] The technical solution of the present invention is not limited to the above-mentioned specific embodiments. All technical variations made according to the technical solution of the present invention fall within the protection scope of the present invention.

Claims

1. A method for preparing a phenolic resin-based silicon-boron modified material, characterized in that: The following steps are involved: S1. Phenol, formaldehyde, boric acid and silicon components were weighed in a molar ratio of 1:1.2:0.2:0.1, phenol and formaldehyde were placed in a three-necked flask, and then ammonia water was added as a catalyst, and mechanical stirring was performed at 70° C. for 1.5 hours. After the reaction was completed, the water in the reaction system was removed by a vacuum dehydration process to obtain a preliminary product of hydroxymethylphenol (SA); S2, dispersing the silicon component monomer in ethanol, and adjusting the pH to 6-6.5 with acetic acid to form a uniform solution, the solution is mixed with hydroxymethylphenol solution under strong stirring, and then reacted under reflux conditions of 100° C. for 1 hour to ensure that the silicon component and SA are fully reacted; S3. Slowly add boric acid (BA) dissolved in ethanol to the above mixture, and react under reflux conditions at 100° C. for 2 hours. After the reaction is completed, remove the solvent and residual water to obtain a phenolic resin-based silicon-boron modified material PFMM.

2. The method for preparing a phenolic resin-based silicon-boron modified material according to claim 1, characterized in that: The silicon component is phenyltriethoxysilane or tetraethoxysilane.

3. A phenolic resin-based silicon-boron modified material prepared by the method according to claim 1 or 2.

4. Use of the phenolic resin-based silicon-boron modified material as claimed in claim 3 in the preparation of high-performance phenolic resin cured engineering materials.

5. The use of the phenolic resin-based modified material according to claim 4 in the preparation of high-performance phenolic resin-cured engineering materials, characterized in that: The following steps are involved: (1) heating the phenolic resin-based silicon boron modified material to 95-135° C., at which time the viscosity of the phenolic resin-based silicon boron modified material is less than 1000 mPa·s; (2) Weaving and molding: The phenolic resin-based silicon boron modified material film is woven into samples of corresponding specifications and sizes. The pressing process is as follows: the room temperature is raised to 90°C, kept warm for 30 minutes, and the air is released once; then a full pressure of 30 tons is applied, the temperature is raised to 130°C, and the temperature is kept warm for 1 hour; then the temperature is raised to 160°C, and the temperature is kept warm for 1 hour; finally, the temperature is raised to 170°C, and the temperature is kept warm for 30 minutes. After natural cooling, the material is taken out to prepare high-performance phenolic resin cured engineering materials.

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