Modified phenolic resin with multi-aromatic ring structure as well as preparation method and application of modified phenolic resin

Abstract

The invention discloses modified thermoplastic phenolic resin with a multi-aromatic ring structure as well as a preparation method and application of the modified thermoplastic phenolic resin. The structural formula of the modified phenolic resin with the multi-aromatic ring structure is shown as a formula I in the specification. The compound is prepared from naphthalene diphenol, phenylphenol, phenol and formaldehyde through addition condensation reaction. From the perspective of resin matrix molecular structure design, a multi-aromatic ring structure (naphthalene ring, biphenyl structure and the like) is introduced into a main chain structure, so that the content of aromatic rings in the resin molecular structure is increased, the residual carbon rate of the resin is increased, and the carbon forming quality of the resin is improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of design, preparation and application of high-performance composite matrix resin, and particularly relates to a multi-aromatic ring structure modified phenolic resin and a preparation method and application thereof, in particular to a preparation method and application of a high-carbon yield and high-carbon mass ablation-resistant phenolic resin containing naphthalene ring and biphenyl structure in the main chain structure. BACKGROUND

[0002] Phenolic resin is a kind of resin obtained by condensation polymerization of phenolic compounds and aldehyde compounds, and is the earliest artificial synthetic polymer material to realize industrial production and application. It has been widely used in industry due to the easy availability of raw materials, low price, simple and mature production process, less investment in manufacturing and processing equipment, and the performance after curing can meet the requirements of various uses. Phenolic resin has the advantages of high temperature resistance, high carbon residue, low smoke toxicity, low cost, and can maintain the integrity of its structure and the stability of its size at high temperatures, and thus has a very wide application in the field of high-performance composites in the fields of construction, transportation, electronics, and high-tech fields such as aviation and aerospace.

[0003] Compared with traditional industrial bitumen, phenolic resin has excellent processability, low viscosity, easy penetration into fiber braiding body, and can fully infiltrate the fiber braiding body to form a good composite interface, thereby significantly improving the performance of the composite material. Moreover, resin carbon converted from phenolic resin has low environmental pollution, high carbon strength and high hardness, so phenolic resin is often used as a precursor resin for carbon materials, such as high-performance carbon / carbon (C / C) composite matrix and carbon / phenolic ablation-resistant material densification impregnant, etc. Unlike the application of traditional phenolic resin, the new carbon precursor phenolic resin needs to control its structure during synthesis, and also needs to study the changes of its structure during pyrolysis. Therefore, starting from the source of molecular structure design, combining with the synthesis reaction control technology of resin, the control of the carbon structure, mass and performance of resin through the regulation of the organic structure of resin has become a new field running through the synthesis of organic resin to the preparation of inorganic material, and also provides a new feasible technical approach for the manufacture of high-performance carbon materials.

[0004] The currently used carbon precursor organic resin mainly includes furan resin and traditional phenol formaldehyde resin, wherein the carbonization rate of the furan resin is relatively low (about 55%), and a medium or strong acid such as phosphoric acid needs to be used as a curing agent, and problems such as flammability and high smoke exist. As the traditional phenol formaldehyde resin applied as the carbon precursor, the oxygen element content is relatively high, the carbonization rate is relatively low, and the resin curing shrinkage is relatively large. In addition, the matrix carbon obtained after carbonization of the ordinary phenolic resin is prone to cracking, and the strength is relatively low, and the comprehensive performance of the composite material is difficult to control. Therefore, how to solve the problem of excessive shrinkage of the carbon precursor resin during high-temperature carbonization, improve the carbonization structure of the matrix resin, increase the carbon residue rate of the matrix resin, and improve the carbonization quality of the resin, has become a core problem that must be solved in the design and preparation of a new type of carbon precursor resin, and is also one of the key technologies to be broken through in the research and development of a new type of heat-resistant composite material matrix resin. SUMMARY

[0005] The purpose of the present application is to provide a multi-aromatic ring structure modified thermoplastic phenolic resin and its preparation method and application, by introducing rigid structures such as naphthalenediol and phenylphenol into the molecular structure, the carbon residue rate of the phenolic resin is improved, the carbonization and curing shrinkage of the resin is reduced, and the carbonization structure and carbonization quality of the resin are improved.

[0006] In order to achieve the above purpose, the present application provides a multi-aromatic ring structure modified phenolic resin.

[0007] The multi-aromatic ring structure modified phenolic resin provided by the present application has a structural formula as shown in formula I:

[0008]

[0009] Wherein x+y+z=1, x is in the range of 0-1, but not 1; y is in the range of 0-0.5 (specifically, 0-0.25); z is in the range of 0-0.5 (specifically, 0-0.25), and y and z cannot be 0 at the same time.

[0010] The multi-aromatic ring structure modified phenolic resin shown in formula I is prepared by addition condensation reaction of naphthalenediol, phenylphenol and phenol and formaldehyde;

[0011] Wherein, the molar ratio of naphthalenediol to phenol is 0-0.25, and the molar ratio of phenylphenol to phenol is 0-0.25, and both cannot be 0 at the same time.

[0012] The naphthalenediol includes at least one of 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 1,7-dihydroxynaphthalene and 1,8-dihydroxynaphthalene.

[0013] The phenylphenol includes at least one of o-phenylphenol, p-phenylphenol and m-phenylphenol.

[0014] The multi-ring structure modified phenolic resin is prepared by a method comprising the following steps:

[0015] A mixed solution containing phenol, naphthalene diol, phenyl phenol and a catalyst is heated to a desired temperature, an aqueous formaldehyde solution is added dropwise to the mixed solution, and an addition reaction is first carried out at a low temperature, and then a polycondensation reaction is carried out at a higher temperature to obtain a multi-ring structure modified phenolic resin.

[0016] In the above method, the naphthalene diol includes at least one of 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 1,7-dihydroxynaphthalene and 1,8-dihydroxynaphthalene;

[0017] The phenyl phenol includes at least one of o-phenylphenol, p-phenylphenol and m-phenylphenol;

[0018] The amount of naphthalene diol is 0-25% of the total moles of phenolic monomers, the amount of phenyl phenol is 0-25% of the total moles of phenolic monomers, and both cannot be 0 at the same time;

[0019] The catalyst is an acidic catalyst, and the amount of catalyst is 0.5-5% of the total mass of phenols used, preferably 1% and 2%.

[0020] The catalyst can be specifically one, two or more of oxalic acid, hydrochloric acid, sulfuric acid, p-toluenesulfonic acid and phosphoric acid;

[0021] The catalyst is added in the form of a catalyst solution, and can be specifically at least one of a sulfuric acid solution, a phosphoric acid solution, a p-toluenesulfonic acid solution, a hydrochloric acid solution and an oxalic acid solution.

[0022] The aqueous formaldehyde solution is a 37% aqueous formaldehyde solution;

[0023] The ratio of the moles of pure formaldehyde in the added aqueous formaldehyde solution to the total moles of phenolic monomers (phenol, naphthalene diol and phenyl phenol) is 0.5-0.7, preferably 0.5-0.6;

[0024] The temperature of the addition reaction can be 50-60°C, and the time can be 1-3 hours;

[0025] The temperature of the polycondensation reaction can be 60-100°C, preferably 80-90°C, and the time can be 2-10 hours, preferably 4-6 hours.

[0026] The above method further includes the following steps in the polycondensation reaction: After the reaction is completed, the product is washed repeatedly with hot water until the washing solution is neutral (pH = 6.5-7.5). Then, the product is dissolved in methyl ethyl ketone (MEK), poured into a separatory funnel, and deionized water is added and mixed evenly. After the water and MEK separate into layers, the lower layer of water is released. The operation is repeated until the water layer is nearly neutral to remove the catalyst encapsulated in the product. The MEK layer containing the product is collected, and the solvent MEK is removed by rotary evaporation to obtain the polycyclic aromatic modified phenolic resin.

[0027] The application of the aforementioned polycyclic aromatic modified phenolic resin as a matrix resin in the preparation of high-performance composite materials also falls within the scope of protection of this invention.

[0028] In the aforementioned applications, the high-performance composite materials include high-temperature resistant composite materials, ablation-resistant composite materials, and structural ablation-integrated composite materials, etc.

[0029] The application of the aforementioned polycyclic aromatic modified phenolic resin as a carbon precursor in the preparation of low-density phenolic aerogels, carbon aerogels and their lightweight C / C composites also falls within the scope of protection of this invention.

[0030] The aforementioned polycyclic aromatic modified phenolic resins are used as carbon precursors to prepare low-density phenolic aerogels, carbon aerogels, and their lightweight C / C composites, exhibiting high carbonization rate and high carbonization quality.

[0031] Compared with the prior art, the polycyclic aromatic structure modified ablation-resistant phenolic resin of the present invention has the following beneficial effects:

[0032] (1) This invention proposes to introduce polyaromatic ring structures (naphthalene ring, biphenyl structure, etc.) into the main chain structure of the resin matrix from the perspective of resin matrix molecular structure design, so as to increase the content of aromatic rings in the resin molecular structure, thereby improving the carbon residue rate of the resin and improving the carbonization quality of the resin.

[0033] (2) The polycyclic aromatic modified phenolic resin proposed in this invention has excellent solubility in common solvents such as ethanol, acetone, butanone or tetrahydrofuran. It can be formulated into a resin solution with a solid content of 60-85%. Its viscosity is moderate and its process performance is excellent, which is suitable for the requirements of various composite material molding processes such as compression molding and RTM.

[0034] (3) The polycyclic aromatic modified phenolic resin proposed in this invention has the characteristics of good temperature resistance and high carbon residue. The TGA test results of this resin under nitrogen atmosphere show that the 5% weight loss temperature of the cured phenolic resin of this invention (T0.05) is... d 5 )≥300℃, residual carbon rate (R) at 800℃ 800℃ ≥65%. Attached Figure Description

[0035] Figure 1 Synthetic route of the polyaromatic structure modified thermoplastic phenolic resin of the present application.

[0036] Figure 2 H-NMR of the LNPF-9-9 resin prepared in Example 6 of the present application. 1 H-NMR).

[0037] Figure 3 GPC curve of the LNPF-9-9 resin prepared in Example 6 of the present application.

[0038] Figure 4 DSC curve of the LNPF-9-9 resin prepared in Example 6 of the present application and the PR resin D.

[0039] Figure 5 TGA curve and DTG curve of the LNPF-9-9 resin prepared in Example 6 of the present application and the PR resin prepared in the comparative example.

[0040] Figure 6 XRD curve of the carbide of the LNPF-9-9 resin prepared in Example 6 of the present application and the PR resin prepared in the comparative example.

[0041] Figure 7 Raman curve of the carbide of the LNPF-9-9 resin prepared in Example 6 of the present application and the PR resin prepared in the comparative example. DETAILED DESCRIPTION

[0042] The present application will be further described in conjunction with the specific embodiments, and the examples given are only for the purpose of illustrating the present application, and are not intended to limit the scope of the present application. The examples provided below can serve as a guide for further improvement by those of ordinary skill in the art, and do not in any way constitute a limitation on the present application.

[0043] The experimental methods in the following examples are all conventional methods, and are carried out according to the techniques or conditions described in the literature in the art or according to the product instructions, unless otherwise specified. The materials, reagents, etc. used in the following examples can be obtained from commercial channels, unless otherwise specified.

[0044] Synthesis of naphthalene modified thermoplastic phenolic resin (NPF-19) with n(phenol):n(naphthalenediol) = 19

[0045] Put 1,5-dihydroxynaphthalene 8 g (0.05 mol), phenol 89.40 g (0.95 mol), oxalic acid 0.97 g in a 500 mL three-necked flask equipped with a stirrer, thermometer and condenser pipe, and heat while stirring. When the temperature reaches 50°C, drop 37% formaldehyde aqueous solution 40.54 g into the flask using a constant pressure funnel, and control the drop rate to be 5-6 s / drop to ensure that the temperature of the material is stable at 50±2°C during the drop. After the drop is completed, keep the temperature at 50±1°C for 3 h. Continue to heat, and heat to 80°C for 4 h. After the reaction is completed, first wash with 100 mL hot water, repeat 3 times, and then wash the resin with ketone. After the resin is dissolved, pour it into a separatory funnel, add distilled water, shake, and then stand still. After the layers are separated, remove the water layer, and wash 3 times until the water layer is neutral. Finally, remove the ketone by rotary evaporation to obtain 96.56 g of naphthalene modified thermoplastic phenolic resin (NPF-19).

[0046] Example 2, synthesis of naphthalene modified thermoplastic phenolic resin (NPF-9) with n(phenol):n(naphthalenediol)=9

[0047] Put 1,5-dihydroxynaphthalene 16 g (0.1 mol), phenol 84.60 g (0.9 mol), and concentrated hydrochloric acid 2.63 g in a 500 mL three-necked flask equipped with a stirrer, thermometer and condenser, and heat while stirring. When the temperature is stable at 60±2°C, drop 37% formaldehyde aqueous solution 48.64 g into the flask using a constant pressure funnel, and control the drop rate to be 7-8 s / drop to ensure that the temperature of the system is stable at 60±2°C during the drop. After the drop is completed, keep the temperature at 60±1°C for 2 h. Continue to heat, and heat to 90°C for 6 h. After the reaction is completed, first wash with 100 mL hot water, repeat 3 times, and then dissolve the resin in ketone. After the resin is dissolved, pour it into a separatory funnel, add distilled water, shake, and then stand still. After the layers are separated, remove the water layer, and wash multiple times until the water layer is neutral. Finally, remove the ketone by rotary evaporation to obtain 97.00 g of naphthalene modified thermoplastic phenolic resin (NPF-9).

[0048] Example 3, synthesis of naphthalene modified thermoplastic phenolic resin (NPF-4) with n(phenol):n(naphthalenediol)=4

[0049] Into a 500 mL three-necked flask equipped with a stirrer, thermometer and condenser, 1,5-dihydroxynaphthalene 32 g (0.2 mol), phenol 75.29 g (0.8 mol), concentrated hydrochloric acid 5.80 g were placed, and the temperature was raised while stirring, and when the temperature was stabilized at 50 ± 2 °C, 37% aqueous formaldehyde solution 40.54 g (0.5 mol) was added dropwise using a constant pressure dropping funnel, and the dropping rate was controlled to be 6-8 s / drop, and the temperature was ensured to be stabilized at 50 ± 2 °C during the dropping. After the dropping was completed, the reaction was carried out at 50 ± 1 °C for 3 h. Then the temperature was raised, and the reaction was carried out at 70 °C for 6 h. After the reaction was completed, 100 mL of hot water was first added for water washing, and the operation was repeated 3 times, then the resin was dissolved in a proper amount of methyl ketone, and the dissolved resin was poured into a separatory funnel, and distilled water was added and shaken, and then it was allowed to stand, and after the layers were separated, the water layer was removed, and the washing was repeated until the water layer was neutral, and finally the methyl ketone was removed by rotary evaporation, and 90.35 g of naphthalene modified thermoplastic phenol-formaldehyde resin (NPF-4) was prepared.

[0050] Example 4, synthesis of polyaromatic ring modified thermoplastic phenol-formaldehyde resin (LNPF-4-8) with n(phenol):n(naphthalenediol) = 4 and n(phenol):n(phenylphenol) = 8

[0051] Into a 500 mL three-necked flask equipped with a stirrer, thermometer and condenser, 1,5-dihydroxynaphthalene 32 g (0.2 mol), phenol 75.2 g (0.8 mol), o-phenylphenol 17 g (0.1 mol), concentrated hydrochloric acid 1.68 g were placed, and the temperature was raised while stirring, and when the temperature was stabilized at 60 ± 2 °C, 37% aqueous formaldehyde solution 56.76 g (0.7 mol) was added dropwise using a constant pressure dropping funnel, and the dropping rate was controlled to be 5-6 s / drop, and the reaction was ensured not to be too violent, and the temperature was ensured to be stabilized at 60 ± 2 °C during the dropping. After the dropping was completed, the reaction was carried out at 60 ± 2 °C for 2 h. Then the temperature was raised, and the reaction was carried out at 100 °C for 2 h. After the reaction was completed, 100 mL of hot water was first added for water washing, and the operation was repeated 3 times, then the resin was dissolved in a proper amount of methyl ketone, and the dissolved resin was poured into a separatory funnel, and distilled water was added and shaken, and then it was allowed to stand, and after the layers were separated, the water layer was removed, and the washing was repeated until the water layer was neutral, and finally the methyl ketone was removed by rotary evaporation, and 126.67 g of polyaromatic ring modified thermoplastic phenol-formaldehyde resin (LNPF-4-8) was prepared.

[0052] Example 5, synthesis of polyaromatic ring modified thermoplastic phenol-formaldehyde resin (LNPF-4-4) with n(phenol):n(naphthalenediol) = 4 and n(phenol):n(phenylphenol) = 4

[0053] A 500 mL three-necked flask equipped with a stirrer, thermometer and condenser was charged with 1,5-dihydroxynaphthalene 32 g (0.2 mol), phenol 75.2 g (0.8 mol), o-phenylphenol 34 g (0.2 mol), concentrated hydrochloric acid 1.91 g, and heated with stirring to 60 ± 2 °C. Then, 37% aqueous formaldehyde solution 48.64 g (0.6 mol) was added dropwise at a rate of 5-6 s / drop using a constant pressure dropping funnel to avoid violent heating of the reaction and to ensure that the temperature was stabilized at 60 ± 2 °C during the dropwise addition. After the dropwise addition was completed, the reaction was maintained at 60 ± 2 °C for 2 h. Then, the temperature was increased to 90 °C and maintained for 6 h. After the reaction was completed, the resin was dissolved in butanone and washed with hot water three times. The resin was then dissolved in butanone and transferred to a separatory funnel. Distilled water was added and the mixture was shaken and allowed to stand until the layers separated. The aqueous layer was removed and the resin was washed several times until the aqueous layer was neutral. Finally, the butanone was removed by rotary evaporation to obtain 142.38 g of a polyaromatic ring-modified thermoplastic phenol-formaldehyde resin (LNPF-4-4).

[0054] Example 6. Synthesis of a polyaromatic ring-modified thermoplastic phenol-formaldehyde resin (LNPF-9-9) with n(phenol):n(naphthalenediol) = 9 and n(phenol):n(phenylphenol) = 9

[0055] A 500 mL three-necked flask equipped with a stirrer, thermometer and condenser was charged with 1,5-dihydroxynaphthalene 32 g (0.2 mol), phenol 75.2 g (0.8 mol), o-phenylphenol 34 g (0.2 mol), concentrated hydrochloric acid 1.91 g, and heated with stirring to 60 ± 2 °C. Then, 37% aqueous formaldehyde solution 48.64 g (0.6 mol) was added dropwise at a rate of 5-6 s / drop using a constant pressure dropping funnel to avoid violent heating of the reaction and to ensure that the temperature was stabilized at 60 ± 2 °C during the dropwise addition. After the dropwise addition was completed, the reaction was maintained at 60 ± 2 °C for 2 h. Then, the temperature was increased to 90 °C and maintained for 6 h. After the reaction was completed, the resin was dissolved in butanone and washed with hot water three times. The resin was then dissolved in butanone and transferred to a separatory funnel. Distilled water was added and the mixture was shaken and allowed to stand until the layers separated. The aqueous layer was removed and the resin was washed several times until the aqueous layer was neutral. Finally, the butanone was removed by rotary evaporation to obtain 142.38 g of a polyaromatic ring-modified thermoplastic phenol-formaldehyde resin (LNPF-4-4).

[0056] Example 7. Synthesis of a biphenyl-modified thermoplastic phenol-formaldehyde resin (LPF-4) with n(phenol):n(phenylphenol) = 4

[0057] 75.2 g (0.8 mol) of phenol, 34 g (0.2 mol) of o-phenylphenol, and 2.95 g of concentrated hydrochloric acid were placed in a 500 mL three-necked flask equipped with a stirrer, thermometer, and condenser. The mixture was stirred and heated until it reached 60 ± 2 °C. Then, using a constant pressure funnel, 56.75 g (0.7 mol) of 37% formaldehyde aqueous solution was added dropwise at a rate of 5-6 s / drop to avoid a violent temperature rise and to ensure the temperature remained stable at 60 ± 2 °C during the addition. After the addition was complete, the mixture was kept at 60 ± 2 °C for 2 hours. The temperature was then increased to 80 °C over 30 ± 5 minutes and maintained at this temperature for 6 hours. After the reaction was completed, 100 mL of hot water was added for washing. This was repeated 3 times. The resin was then dissolved in an appropriate amount of butanone. The dissolved resin was poured into a separatory funnel, and distilled water was added. After shaking and standing, the water layer was removed after separation. The water layer was washed multiple times until it was neutral. Finally, the butanone was removed by rotary evaporation to obtain 127.05 g of biphenol-modified thermoplastic phenolic resin (LPF-4).

[0058] Comparative Example 1: Synthesis of Traditional Thermoplastic Phenolic Resin

[0059] 94.11 g (1 mol) of phenol and 0.94 g of oxalic acid were placed in a 500 mL three-necked flask equipped with a stirrer, thermometer, and condenser. The mixture was stirred and heated until it reached 60 ± 2 °C. Then, 56.76 g (0.7 mol) of 37% formaldehyde aqueous solution was added dropwise using a constant pressure funnel. The dropping rate was controlled to avoid a violent temperature rise during the addition, ensuring the temperature remained stable at 60 ± 2 °C. After the addition was complete, the mixture was kept at 60 ± 2 °C for 2 hours. The temperature was then increased to 90 ± 2 °C and maintained for 6 hours. After the reaction was complete, 100 mL of hot water was added for washing, repeated three times. The resin was then dissolved in an appropriate amount of butanone. The dissolved resin was poured into a separatory funnel, distilled water was added, and the mixture was shaken and allowed to stand. After separation, the aqueous layer was removed. The mixture was washed repeatedly until the aqueous layer was neutral. Finally, the butanone was removed by rotary evaporation, yielding 130.41 g of conventional thermoplastic phenolic resin (PR).

[0060] The modified resins prepared in Examples 1-7 of this invention used the same characterization techniques for molecular structure and carbon structure, such as NMR, IR, and XRD. Most of these were qualitative characterizations used to prove the presence or absence of functional groups and whether the carbon layers were ordered. The spectra were very similar. To avoid too many homogeneous images, we took the test results of Example 6 as an example and listed the specific test result images and compared them with the comparative examples.

[0061] The test conditions are as follows:

[0062] (1) Liquid nuclear magnetic resonance hydrogen spectrum 1 H-NMR: The instrument used was a Bruker AVIII 400HD, and the solvent used was deuterated dimethyl sulfoxide (DMSO-d6).

[0063] (2) Gel permeation chromatography (GPC) test conditions: tetrahydrofuran as the mobile phase, polystyrene spheres as the stationary phase; tested on a Waters 1515 gel permeation chromatograph, with a flow rate of 10 mL / min and a temperature of 35°C.

[0064] (3) Resin cured product preparation conditions: 120°C / 2h→140°C / 2h→160°C / 2h→180°C / 4h, with a temperature ramping time of 30 min between temperature stages.

[0065] (4) Curing behavior test (DSC): the modified resin was mixed with 10% of the resin mass of curing agent hexamethylenetetramine (HMTA) in ethanol, and then coated on an aluminum foil and air-dried to remove the solvent. A Mettler Toledo DSC822e differential scanning calorimeter was used, with N2as the test atmosphere, a flow rate of 50 mL / min, a temperature ramping rate of 20°C / min, and a test range of 30-300°C.

[0066] (5) Thermogravimetric analysis (TGA) test conditions: the solid sample was crushed and sieved, and the sample with a particle size of 40-60 mesh was reserved for testing. The sample was dried at 105°C for 30 minutes before testing, and was cooled in a desiccator to remove adsorbed water. The TGA test was performed on a Netzsch TG209F1-Is10 in a nitrogen atmosphere, with a temperature ramping rate of 10°C / min, a flow rate of 50 mL / min, a protective gas of nitrogen at a flow rate of 20 mL / min, and a test range of 30-1000°C.

[0067] (6) Resin carbide preparation conditions: 30°C→180°C / 1h→450°C / 1h→800°C / 2h, with a temperature ramping rate of 1°C / min.

[0068] (7) XRD analysis: the 800°C carbonized products of the two resins were tested at room temperature on a DMAX-2400 X-ray powder diffractometer produced by Shimadzu Corporation of Japan; CuKα

[0069] radiation source, with an emission voltage of 40 kV and a current of 200 mA. The test scanning angle range was 10-80°, and the scanning speed was 6° / min.

[0070] (8) Raman analysis: tested at room temperature on a LabRAM HR Evolution produced by HORIBA of France.

[0071] The corresponding test results of the products obtained in the above examples and comparative examples are as follows:

[0072] The molecular structure characteristics of the comparative example PR and the LNPF-9-9 resin in Example 6 were characterized by FT-IR, such as... Figure 2 As shown. From Figure 2 It can be seen that the hydrogen at 7.3-7.5 ppm corresponds to the hydrogen on phenylphenol, and the hydrogen at 7.6 ppm corresponds to the hydrogen on the naphthalene ring. The 1H NMR spectrum shows that the product contains biphenyl and naphthalene ring structures, which proves the successful synthesis of the modified resin.

[0073] The molecular weight and molecular weight distribution of the LNPF-9-9 resin in Example 6 were characterized by gel permeation chromatography (GPC). The results are as follows: Figure 3 As shown. From Figure 3 It can be seen from the GPC curve of LNPF-9-9 resin that LNPF resin exhibits polydispersity characteristics, indicating that the polymerization reaction proceeds smoothly.

[0074] The curing behavior of the PR resin in the comparative example and the LNPF-9-9 resin prepared in Example 6 was studied using DSC. Figure 4 The DSC curves for the two resins are shown. It can be seen that, compared to PR resin, the curing temperature of LNPF-9-9 resin shifts towards lower temperatures, indicating that this resin has better curing process performance.

[0075] The thermal properties of the cured resin under nitrogen atmosphere were characterized using TGA, and the corresponding results are as follows: Figure 5 As shown. From Figure 5 It can be seen that the residual carbon rate of LNPF-9-9 resin at 800℃ is 66.05%, which is significantly higher than that of traditional phenolic resin. This indicates that the introduction of biphenyl and naphthalene ring structures increases the content of benzene rings in the resin, thereby improving the residual carbon rate. Figure 5 It can also be seen that the 5% weight loss temperature of LNPF-9-9 resin is 394.5℃, which is about 70℃ higher than that of traditional PR resin. Moreover, the maximum thermal decomposition rate of LNPF-9-9 resin is only 1.40% / min, which is about 21% lower than that of traditional phenolic resin (1.78% / min), indicating that the thermal stability of this resin is significantly improved.

[0076] Table 1 summarizes the TGA test results of the LNPF resin samples prepared in Examples 1-7. It can be seen that the 5% weight loss temperature of the cured resins of this series is greater than 300℃, and the carbon residue at 800℃ is greater than 65%, indicating that the resins of this series have good stability and high carbon residue.

[0077] Table 1. Summary of TGA test results of LNPF series resins prepared in Examples 1-7

[0078] Number Name T d5％ / %]]> Carbon residue (800°C) / % Thermal decomposition peak temperature / °C Example 1 NPF-19 310.0 65.80 515.3 Example 2 NPF-9 348.0 65.30 531.0 Example 3 NPF-4 344.0 68.23 517.3 Example 4 LNPF-4-8 342.45 66.15 531.4 Example 5 LNPF-4-4 348.15 66.29 530.9 Example 6 LNPF-9-9 394.5 66.05 529.0 Example 7 LPF-4 332.4 65.85 498.5

[0079] The structure characteristics of the carbonized LNPF-9-9 resin were characterized by XRD and Raman, and the results are shown in Figure 6 and Figure 7 The XRD pattern Figure 6 shows two broad peaks at 24° and 43°, which are attributed to (002) and (100) crystal planes, respectively. This means that the carbon of LNPF resin and PR resin both have amorphous carbon crystal structure. There are two broad peaks in the Raman spectrum Figure 7 , the D peak at about 1350 cm -1 represents the defects of carbon atom lattice, and the G peak at about 1580 cm -1 is related to the in-plane stretching vibration of sp 2 hybrid of carbon atom. It can be seen from Figure 7 that the G peak of LNPF-10-10 resin is improved, which means that the introduction of biphenyl structure and naphthalene ring structure improves the graphitization degree of LNPF resin.

[0080] In addition, from the results of our synthesis practice, when the ratio of naphthalenediol to phenol exceeds 25%, gelation occurs during the synthesis of the resin, which leads to the failure of the synthesis of the resin. This is the basis for providing different ratios of monomers in the present patent.

[0081] The present application has been described in detail. For those skilled in the art, without departing from the purpose and scope of the present application, and without unnecessary experiments, the present application can be implemented in a wider range under the same parameters, concentrations and conditions. Although the present application gives a special example, it should be understood that further improvements can be made to the present application. In summary, according to the principle of the present application, this application intends to include any changes, uses or improvements of the present application, including changes made by conventional techniques known in the art, which are outside the scope disclosed in the present application.

Claims

1. A polycyclic aromatic modified phenolic resin, the structural formula of which is shown in Formula I: Where x + y + z = 1, x ranges from 0 to 1, y ranges from 0 to 0.5, z ranges from 0 to 0.5, and y and z cannot both be 0 at the same time.

2. The polycyclic aromatic hydrocarbon modified phenolic resin according to claim 1, characterized in that, The polycyclic aromatic modified phenolic resin shown in Formula I is prepared by the addition condensation reaction of naphthol, phenylphenol, and phenol with formaldehyde. The molar ratio of naphthol to phenol is 0–0.25, and the molar ratio of phenylphenol to phenol is 0–0.25, and neither of them is 0 at the same time.

3. The polycyclic aromatic hydrocarbon modified phenolic resin according to claim 2, characterized in that, The naphthol includes at least one of 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 1,7-dihydroxynaphthalene, and 1,8-dihydroxynaphthalene; The phenylphenol includes at least one of o-phenylphenol, p-phenylphenol, and m-phenylphenol.

4. A method for preparing the polycyclic aromatic resin modified with phenolic resin according to any one of claims 1-3, comprising the following steps: A mixed solution containing phenol, naphthol, phenylphenol, and a catalyst is heated to the desired temperature. An aqueous formaldehyde solution is then added dropwise to the mixed solution. First, an addition reaction is carried out at a low temperature, and then a condensation reaction is carried out at a higher temperature to obtain a polycyclic aromatic hydrocarbon modified thermoplastic phenolic resin.

5. The method according to claim 4, characterized in that, The catalyst is an acidic catalyst, and the amount of catalyst used is 0.5-5% of the total mass of phenol used; The formaldehyde aqueous solution is a 37% formaldehyde aqueous solution; The ratio of the number of moles of pure formaldehyde to the total number of moles of phenolic monomers in the added formaldehyde aqueous solution is 0.5-0.

7.

6. The method according to claim 4 or 5, characterized in that, The addition reaction is carried out at a temperature of 50-60°C for 1-3 hours. The polycondensation reaction is carried out at a temperature of 60-100℃ for 2-10 hours.

7. The method according to claim 4 or 5, characterized in that, The polycondensation reaction further includes the following steps: After the reaction is complete, the product is washed repeatedly with hot water until the washing liquid is neutral. Then, the product is dissolved in methyl ethyl ketone (MEK), poured into a separatory funnel, and deionized water is added and mixed evenly. After standing, the water and MEK separate into layers, and the lower layer of water is released. The operation is repeated until the water layer is nearly neutral to remove the catalyst encapsulated in the product. The MEK layer containing the product is collected, and the solvent MEK is removed by rotary evaporation to obtain a polycyclic aromatic modified phenolic resin.

8. The use of the polycyclic aromatic modified phenolic resin according to any one of claims 1-3 as a matrix resin in the preparation of high-performance composite materials.

9. The application according to claim 8, characterized in that, The high-performance composite materials include high-temperature resistant composite materials, ablation-resistant composite materials, and structural ablation-integrated composite materials.

10. The use of the polycyclic aromatic modified phenolic resin according to any one of claims 1-3 as a carbon precursor in the preparation of low-density phenolic aerogels, carbon aerogels and their lightweight C / C composites.

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