High-strength and high-residual-carbon carbon / carbon composite material and preparation method thereof

Abstract

The invention provides a carbon / carbon composite material with high strength and high residual carbon and a preparation method thereof, and the method comprises the following steps: mixing bisphenol A epoxy acrylate with HDDA, adding a photoinitiator, and fully stirring and mixing to obtain EA; adding a thermal curing agent into the PR for pretreatment; mixing EA and the treated PR in proportion, then adding CF and FS, and fully stirring and mixing to obtain a dual-curing resin system; performing preforming through ultraviolet curing; and carrying out thermocuring treatment in a vacuum drying oven to obtain the product. According to the method, the dependence on a mold in a traditional carbon / carbon composite material prefabricated body preparation process is avoided, and the manufacturing cost is effectively reduced; by introducing an ultraviolet light auxiliary curing technology, hollow structures such as trusses and cantilevers can be directly manufactured; the optimized thermocuring process realizes the curing of the dual-curing resin system under the non-pressure condition, and avoids the phenomena of'expansion, bubbling 'and the like of a molded component caused by water vapor generated in the curing process of phenolic resin.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and particularly relates to a carbon / carbon composite material with high strength and high residual carbon and a preparation method thereof. Background Art

[0002] Carbon / carbon composite material is a high-performance material, which is composed of carbon fiber or graphite fiber as the reinforcing material and combined with a carbonaceous matrix. Due to its excellent mechanical properties, low coefficient of thermal expansion, high thermal conductivity and electrical conductivity, excellent heat shock resistance, ablation resistance and friction resistance, it shows great application potential in many industries such as aerospace, automobile manufacturing, and medical equipment.

[0003] In terms of preparing the preform of carbon / carbon composite materials, the currently commonly used methods include needle punching, weaving, winding and lamination processes. However, these traditional processes often rely on specific molding dies, have certain limitations for the integrated molding of complex structures, and the cost of related processing equipment is relatively high. With the continuous pursuit of personalized design, flexible manufacturing processes and new material development, additive manufacturing technology has developed rapidly in the field of complex structure molding and high-performance applications. This technology can not only significantly reduce costs and shorten the production cycle, but also provide highly customized design solutions.

[0004] Although the patent authorization number CN113321912B discloses a high-temperature resistant 3D printing photosensitive resin and its preparation method and application, it uses an epoxy resin system. Although the patent authorization number CN107383763B discloses a preparation method of a halogen-free flame-retardant low-smoke and low-toxic hot-melt phenolic prepreg, in essence, it is a modification of phenolic resin, and the main function of phenolic epoxy resin is an adhesive, and its essential property is the same as that of epoxy resin, with a low residual carbon rate and is not suitable for 3D printing itself.

[0005] In summary, the traditional preparation process of carbon / carbon composite material preforms leads to high manufacturing costs due to the dependence on molds, and the phenolic epoxy resin system used is not suitable for additive manufacturing, and problems such as "expansion and bubbling" of the formed components caused by the water vapor generated during the curing process of phenolic resin. Based on this, the present invention proposes a carbon / carbon composite material with high strength and high residual carbon and a preparation method thereof. Summary of the Invention

[0006] The present invention provides a carbon / carbon composite material with high strength and high residual carbon and a preparation method thereof, and the purpose is to solve the above problems existing in the background art.

[0007] In order to achieve the above purpose, the embodiment of the present invention provides a preparation method of a carbon / carbon composite material with high strength and high residual carbon, including the following steps:

[0008] S1. Mix bisphenol A epoxy acrylate and 1,6 - hexanediol diacrylate (HDDA) in a certain mass ratio, then add a photoinitiator, and stir and mix well to obtain a photosensitive resin EA; this photosensitive resin has a high curing depth;

[0009] S2. Add a thermal curing agent to the phenolic resin PR for pretreatment to control its initial curing temperature;

[0010] S3. Mix the photosensitive resin and the pretreated phenolic resin in proportion, then add carbon fiber CF and fumed silica FS, and stir and mix well to obtain a dual - curing resin system; this dual - curing resin system has no bubbles and has an excellent curing depth;

[0011] S4. Perform pre - forming by ultraviolet light curing to obtain a pre - formed component;

[0012] S5. Place the pre - formed component in a vacuum drying oven for thermal curing treatment to prepare the high - strength and high - residual - carbon carbon / carbon composite material.

[0013] Preferably, in step S1, bisphenol A epoxy acrylate and 1,6 - hexanediol diacrylate (HDDA) are mixed in a mass ratio of 7:3.

[0014] Preferably, in step S1, the photoinitiator is 1.50 wt% trimethylbenzoyl - diphenylphosphine oxide (TPO) and 0.50 wt% phenylbis(2,4,6 - trimethylbenzoyl)phosphine oxide (819).

[0015] Preferably, in step S2, the thermal curing agent is benzenesulfonyl chloride, and its content is 0.8 wt% of the phenolic resin.

[0016] Preferably, in step S3, the mass ratio of the photosensitive resin to the pretreated phenolic resin is 5:5, 4:6 or 3:7.

[0017] Preferably, in step S3, the content of carbon fiber CF is 5 - 15 wt%, and the content of fumed silica FS is 3 wt%.

[0018] Preferably, in step S3, the process of stirring and mixing well is as follows: stir at 1000 rpm for 5 min, then stir at 1800 rpm for 5 min, then stir at 1500 rpm for 5 min, and finally stir at 1800 rpm for 5 min.

[0019] Preferably, in step S4, the ultraviolet light curing uses a screw - extrusion type ultraviolet - assisted three - dimensional direct writing (UV - DIW) forming platform; the nozzle diameter is 1.0 mm, the printing layer height is 0.1 mm, and the ultraviolet light intensity is 180 - 220 mW / cm 2, the printing speed is 20 mm / s, the filling density is 100%, and the filling angle is 0-90°.

[0020] Preferably, in step S5, the heat curing process is as follows: under vacuum conditions, the temperature is raised to 80 °C and held for 2 h, then raised to 100 °C and held for 2 h, then raised to 120 °C and held for 1 h, and finally raised to 140 °C and held for 2 h.

[0021] Based on the general concept of an invention, an embodiment of the present invention provides a high-strength and high-residual-carbon carbon / carbon composite material obtained by the above preparation method.

[0022] The above solution of the present invention has the following beneficial effects:

[0023] The present invention avoids the dependence on molds in the preparation process of traditional carbon / carbon composite preforms, effectively reducing the manufacturing cost; by introducing ultraviolet light-assisted curing technology, it can directly manufacture hollow structures such as trusses and cantilevers; the optimized heat curing process realizes the curing of the dual-curing resin system under pressureless conditions, avoiding phenomena such as "expansion and bubbling" of the formed components caused by water vapor generated during the curing process of phenolic resin. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention, and those of ordinary skill in the art can also obtain other drawings based on these drawings without creative efforts.

[0025] Figure 1 is a schematic diagram of the configuration of the dual-curing resin system according to an embodiment of the present invention;

[0026] Figure 2 is an optimization diagram of the photoinitiator according to an embodiment of the present invention;

[0027] Figure 3 is the rheological behavior of the dual-curing resin system according to an embodiment of the present invention;

[0028] Figure 4 is an optimization diagram of the heat curing process according to an embodiment of the present invention;

[0029] Figure 5 is the tensile and bending properties of the formed components according to an embodiment of the present invention;

[0030] Figure 6 is the residual carbon rate and open porosity of the formed components after pyrolysis according to an embodiment of the present invention;

[0031] Figure 7The thermal curing behavior of the dual-curing resin system of the present invention: (a) the influence of phenolic resin content and benzenesulfonyl chloride on the curing behavior; (b) the dual-curing resin system; (c) the sample after photocuring; (d) the sample without carbon fiber added; (e) the sample with carbon fiber added. Detailed implementation manners

[0032] To make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following will be described in detail with reference to the accompanying drawings and specific embodiments.

[0033] Unless otherwise defined, all professional terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention.

[0034] Unless otherwise specifically stated, various raw materials, reagents, instruments and equipment used in the present invention can be obtained through market purchase or can be prepared by existing methods.

[0035] Aiming at the problems that the traditional preparation process of carbon / carbon composite preforms relies on molds, resulting in high manufacturing costs, the phenolic epoxy resin system used is not suitable for additive manufacturing, and in the epoxy resin system, when phenolic resin is added, "expansion and bubbling" and other phenomena occur in the formed components due to the water vapor generated during the curing process of phenolic resin, etc., the present invention provides a preparation method of a high-strength and high-residual-carbon carbon / carbon composite, including the following steps:

[0036] S1. Mix bisphenol A epoxy acrylate and 1,6-hexanediol diacrylate HDDA in a certain mass ratio, and then add a photoinitiator, and stir and mix well to obtain a photosensitive resin EA; this photosensitive resin has a high curing depth;

[0037] S2. Add a thermal curing agent to the phenolic resin PR for pretreatment to control its initial curing temperature;

[0038] S3. Mix the photosensitive resin and the pretreated phenolic resin in a certain proportion, and then add carbon fiber CF and fumed silica FS, and stir and mix well to obtain a dual-curing resin system; this dual-curing resin system has no bubbles and has excellent curing depth;

[0039] S4. Perform preforming by ultraviolet light curing to obtain a preformed component;

[0040] S5. Place the preformed component in a vacuum drying oven for thermal curing treatment to prepare the high-strength and high-residual-carbon carbon / carbon composite.

[0041] Preferably, in step S1, bisphenol A epoxy acrylate and 1,6 - hexanediol diacrylate (HDDA) are mixed at a mass ratio of 7:3.

[0042] Preferably, in step S1, the photoinitiator is 1.50 wt% trimethylbenzoyl - diphenylphosphine oxide (TPO) and 0.50 wt% phenylbis(2,4,6 - trimethylbenzoyl)phosphine oxide (819).

[0043] Preferably, in step S2, the thermal curing agent is benzenesulfonyl chloride, and its content is 0.8 wt% of the phenolic resin.

[0044] Preferably, in step S3, the mass ratio of the photosensitive resin to the pretreated phenolic resin is 5:5, 4:6, or 3:7.

[0045] Preferably, in step S3, the content of carbon fiber CF is 5 - 15 wt% of the resin after mixing the pretreated phenolic resin and the photosensitive resin, and the content of fumed silica FS is 3 wt% of the resin after mixing the pretreated phenolic resin and the photosensitive resin.

[0046] Preferably, in step S3, the process of sufficient stirring and mixing is as follows: stir at 1000 rpm for 5 min, then stir at 1800 rpm for 5 min, then stir at 1500 rpm for 5 min, and finally stir at 1800 rpm for 5 min.

[0047] Preferably, in step S4, the ultraviolet curing uses a screw - extrusion type ultraviolet - assisted three - dimensional direct writing (UV - DIW) forming platform; the nozzle diameter is 1.0 mm, the printing layer height is 0.1 mm, the ultraviolet light intensity is 180 - 220 mW / cm 2 , the printing speed is 20 mm / s, the filling density is 100%, and the filling angle is 0 - 90°.

[0048] Preferably, in step S5, the thermal curing process is as follows: under vacuum conditions, heat up to 80 °C and keep warm for 2 h, heat up to 100 °C and keep warm for 2 h, heat up to 120 °C and keep warm for 1 h, and heat up to 140 °C and keep warm for 2 h.

[0049] Based on the general concept of an invention, an embodiment of the present invention provides a high - strength and high - residual - carbon carbon / carbon composite material obtained by the above - mentioned preparation method.

[0050] Example

[0051] A preparation method of a high - strength and high - residual - carbon carbon / carbon composite material, comprising the following steps:

[0052] Step one: The schematic diagram of the preparation process of the dual - curing resin system of the carbon / carbon composite material is as Figure 1As shown. Before configuring the dual-curing resin system, bisphenol A epoxy acrylate and HDDA were first mixed at a mass ratio of 7:3 to adjust its viscosity. Subsequently, 2.00 wt% of a mixed photoinitiator (1.50 wt% TPO + 0.50 wt% 819) was added thereto, and it was thoroughly mixed by a stirring and degassing machine to obtain a photosensitive resin system (EA) with a high curing depth. Before using phenolic resin (PR), 0.8 wt% of the thermal curing agent benzenesulfonyl chloride was added thereto to control its initial curing temperature. The configured photosensitive resin and the treated phenolic resin were mixed at a certain ratio (5:5, 4:6, 3:7), and carbon fiber (CF, 5 - 15 wt%) and fumed silica (FS, 3 wt%) were added thereto. The mixed system was thoroughly mixed by using a stirring and degassing machine. The mixing procedure was as follows: stirring at 1000 rpm for 5 min, then stirring at 1800 rpm for 5 min, then stirring at 1500 rpm for 5 min, and finally stirring at 1800 rpm for 5 min again to obtain a dual-curing resin system without bubbles and with excellent curing depth. The configured dual-curing resin system will complete the preparation and use of samples on the same day. The component ratios are shown in Table 1 in detail.

[0053] Table 1. Component ratios of the dual-curing resin system

[0054]

[0055] Step 2: Using a self-built screw extrusion type ultraviolet light-assisted three-dimensional direct writing (UV-DIW) molding platform, the above dual-curing resin system was preformed. To facilitate the demolding of the formed component from the bottom plate, a layer of Teflon film was evenly laid on the bottom plate before printing. At this stage, the mechanical properties of the formed component were not yet sufficient to bear the load and only served as a support structure.

[0056] Step 3: The preformed component was placed in a vacuum drying oven for subsequent thermal curing treatment to ensure complete curing of the resin, thereby significantly improving the mechanical properties of the component. To ensure that the dual-curing resin systems with different formulations can be effectively molded, the relevant dual-curing process parameters are listed in Table 2 below.

[0057] Table 2 Dual-curing process parameters

[0058]

[0059] During the additive manufacturing process, the curing depth plays a crucial role in determining the layer height of the dual-curing resin system. To improve the accuracy of the formed layers, curing depth tests were conducted on mixtures of photoinitiators with different contents and ratios, aiming to explore the optimal photoinitiator combination to maximize the layer height of the resin system. The experimental results showed that when photoinitiator TPO and photoinitiator 819 were mixed in a ratio of 3:1, the dual-curing resin system achieved the maximum curing depth, as Figure 2 shown. By optimizing the ratio of this mixed photoinitiator, it is possible to ensure optimal layer thickness control during additive manufacturing, thereby improving manufacturing efficiency and product quality.

[0060] Dual-curing resin systems are typically designed to have shear-thinning properties, which reduce viscosity at high shear rates, ensuring that the ink can be smoothly extruded from the nozzle. At the same time, to prevent the formed components from collapsing under static conditions, the ink needs to have sufficient anti-flow ability. Therefore, the rheological properties of the dual-curing resin system were characterized in detail, as Figure 3 shown. Figure 3 (a) shows the variation of the viscosity of the dual-curing resin system with the shear rate. It can be observed that all dual-curing resin systems exhibit shear-thinning properties. Since the viscosity of phenolic resin is higher than that of the photosensitive resin system, as the content of phenolic resin increases, the viscosity of the dual-curing resin system gradually increases. In addition, the addition of carbon fiber increases the solid content of the dual-curing resin system, further increasing the viscosity of the ink. By stress scanning to analyze the relationship between the shear stress and the storage modulus of the dual-curing resin system, as Figure 3 (b) shown, which includes the equilibrium storage modulus G′0 and the yield stress τ y of the dual-curing resin system, as Figure 3 (c) shown. A higher τ y means that the lower layer of the formed component is less likely to collapse under the action of the gravity of the upper layer. At the same time, a larger G ’ 0 is beneficial for the dual-curing resin system to remain unbent when forming tall structures and to prevent sagging when forming spanning structures. As can be seen from Figure 3 (b), at low shear stress, the G ’ of the configured dual-curing resin system is greater than G ” , indicating that the ink exhibits more solid-like behavior rather than viscous behavior at this time. As the shear stress increases, when the shear stress is greater than the τ y corresponding to the dual-curing resin system, G ” will exceed G ’ , and at this time the ink will transform into viscous behavior, showing better fluidity.

[0061] Thixotropy describes the ability of a material to return to a state close to its original state after shear stress is removed. As thixotropy increases, the stability of the sample after extrusion from the nozzle and its ability to maintain precise geometry are significantly improved. Figure 3 As shown in (d), due to the addition of FS to the dual-cure resin system, the dual-cure resin system can quickly change from a low viscosity state to a high viscosity state when the shear rate changes suddenly from a high shear rate to a low shear rate, which is beneficial to maintaining the shape of the component during the molding process. In summary, the formulated dual-cure resin system is suitable for DIW molding with specific direction, composition and shape requirements.

[0062] In the post-processing stage of the additive manufacturing process, since the phenolic resin in the dual-cure resin system has not been fully cured after the initial light curing, thermal curing is used to ensure its complete curing to improve the overall performance of the molded component. However, the phenolic resin will cure through a condensation reaction during the curing process, and this process will be accompanied by the generation of water vapor. The presence of water vapor may cause defects such as expansion or bubbling in the molded component, such as Figure 4 shown.

[0063] To avoid these problems, a step-temperature curing method in a vacuum environment is used. This method allows the resin system to cure slowly under pressureless conditions, while promptly removing the generated water vapor, effectively preventing the occurrence of defects. In addition, the complete curing of the phenolic resin significantly enhances the mechanical properties of the molded component, such as Figure 5 As shown in the figure, with the increase of phenolic resin content, the performance of the composite material gradually improves, indicating that the addition of phenolic resin has an enhancing effect on the mechanical properties of the molded component. When no phenolic resin is added, the tensile strength of 10E0P is only 19.51MPa, and the flexural strength is only 30.00MPa.

[0064] like Figure 6 As shown in the figure, the introduction of phenolic resin system and carbon fiber significantly improves the pyrolysis residual carbon rate of the molded components, laying a solid foundation for the subsequent chemical vapor infiltration densification process. In the chemical vapor infiltration process, the porosity is a key factor affecting the material deposition efficiency, density and pore structure, which in turn determines the thermal and mechanical properties of the material. The appropriate porosity can promote the flow of gas inside the preform, expand the deposition area, and increase the deposition rate and uniformity. However, too high a porosity may weaken the strength of the material and lead to uneven performance. Therefore, by adjusting the content of carbon fiber, the porosity can be effectively controlled to optimize the chemical vapor infiltration process and produce carbon / carbon composites with balanced performance.

[0065] By analyzing the thermal enthalpy changes during the curing process of the dual-cure resin system ( Figure 7 ), and explored its thermal curing behavior, providing a theoretical basis for the optimization of thermal curing process.Figure 7 As can be seen from (a), the initial curing temperature of the photosensitive resin system is approximately 182 °C, and its curing process exhibits two endothermic peaks with peak temperatures of 255 °C and 323 °C respectively. This is because the photosensitive resin system contains two oligomers, bisphenol A epoxy acrylate and HDDA. With the addition of phenolic resin, the endothermic peaks in the curing process of the photosensitive resin system shift towards lower temperatures, and the initial curing temperature drops to approximately 103 °C, indicating that the heat released during the curing of phenolic resin can promote the thermal curing reaction of the photosensitive resin system. As is well known, the curing of phenolic resin is a polycondensation reaction, and water is generated during the process, which may cause the "bubbling" phenomenon in the formed components. To avoid the reaction being too rapid, benzenesulfonyl chloride is introduced to lower the initial curing temperature of the dual-curing resin system so that it can cure slowly in a low-temperature environment. At the same time, a vacuum environment is used to effectively extract the water generated during the reaction, thus avoiding the generation of defects inside the formed components. Figure 7 (a) also shows that after adding 0.8 wt% benzenesulfonyl chloride, the initial curing temperature of the dual-curing resin system decreases from 101.03 °C to 80.86 °C, which provides theoretical support for the optimization of the thermal curing process. Figure 7 (b)-(c) show the endothermic peaks of the dual-curing resin system and the photocured formed components during the curing process. Due to the photocuring process, the photosensitive resin system has been partially cured, so its main endothermic peak (marked in red) becomes smoother. At the same time, with the increase in the content of phenolic resin and carbon fiber, its secondary endothermic peak (marked in blue) becomes more obvious. This is because the addition of phenolic resin and carbon fiber hinders the photocuring of some of the photosensitive resin, resulting in these photosensitive resins needing to rely on the heat released during the curing of phenolic resin for further curing. Figure 7 (d) and (e) clearly show this phenomenon. Due to the hindrance of the photocuring process, the photosensitive resin system fails to effectively provide sufficient support strength for the formed components after photocuring, resulting in the sagging of the formed components. Based on this, it is shown that the DIW technology of photo / thermal dual-curing can realize the forming of structures such as hollow and truss by regulating the content of phenolic resin and carbon fiber.

[0066] The above is the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle described in the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a carbon / carbon composite material with high strength and high residual carbon, characterized in that, The steps include: S1. Mix bisphenol A epoxy acrylate and 1,6-hexanediol diacrylate in a certain mass ratio, add a photoinitiator, and stir and mix thoroughly to obtain a photosensitive resin; S2. Adding a heat curing agent to the phenolic resin for pretreatment; S3. The photosensitive resin and the pretreated phenolic resin are mixed in proportion, and then carbon fiber and fumed silica are added, and the mixture is stirred thoroughly to obtain a dual-cure resin system; S4. Preforming by UV curing to obtain a preformed component; S5. Placing the preformed component in a vacuum drying oven for heat curing to prepare the high-strength and high-residual carbon carbon / carbon composite material.

2. The preparation method of a high-strength and high-residual-carbon carbon / carbon composite material according to claim 1, characterized in that, In step S1, bisphenol A epoxy acrylate and 1,6-hexanediol diacrylate HDDA are mixed in a mass ratio of 7:

3.

3. The preparation method of a high-strength and high-residual-carbon carbon / carbon composite material according to claim 1, characterized in that In step S1, the photoinitiator is 1.50 wt% of trimethylbenzoyl-diphenylphosphine oxide and 0.50 wt% of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide.

4. The preparation method of a high-strength and high-residual-carbon carbon / carbon composite material according to claim 1, characterized in that, In step S2, the thermal curing agent is benzenesulfonyl chloride, and its content is 0.8 wt % of the phenolic resin.

5. The preparation method of a high-strength and high-residual-carbon carbon / carbon composite material according to claim 1, characterized in that, In step S3, the mass ratio of the photosensitive resin to the pretreated phenolic resin is 5:5, 4:6 or 3:

7.

6. The preparation method of a high-strength and high-residual-carbon carbon / carbon composite material according to claim 1, characterized in that, In step S3, the content of carbon fiber is 5-15wt%, and the content of fumed silica is 3wt%.

7. The preparation method of a high-strength and high-residual-carbon carbon / carbon composite material according to claim 1, characterized in that, In step S3, the stirring and mixing process is as follows: stirring at 1000 rpm for 5 min, then stirring at 1800 rpm for 5 min, then stirring at 1500 rpm for 5 min, and finally stirring at 1800 rpm for 5 min.

8. The preparation method of a high-strength and high-residual-carbon carbon / carbon composite material according to claim 1, characterized in that, In step S4, the ultraviolet curing uses a screw extrusion type ultraviolet-assisted three-dimensional direct writing forming platform; the nozzle diameter is 1.0 mm, the printing layer height is 0.1 mm, and the ultraviolet light intensity is 180-220 mW / cm 2 , the printing speed is 20 mm / s, the filling density is 100%, and the filling angle is 0-90°.

9. The preparation method of a high-strength and high-residual-carbon carbon / carbon composite material according to claim 1, characterized in that, In step S5, the heat curing process is: under vacuum conditions, the temperature is raised to 80°C and kept for 2 hours, the temperature is raised to 100°C and kept for 2 hours, the temperature is raised to 120°C and kept for 1 hour, and the temperature is raised to 140°C and kept for 2 hours.

10. A high-strength and high-residual-carbon carbon composite material obtained by the preparation method according to any one of claims 1 to 9.

Images