EPDM (ethylene-propylene-diene monomer) resin-based carbon fiber prepreg forming method

Abstract

The invention relates to the technical field of thermal insulation materials, and particularly discloses an EPDM (Ethylene-Propylene-Diene Monomer) resin-based carbon fiber prepreg forming method which comprises the following steps: S1, dissolving EPDM by using a solvent to prepare a glue solution; s2, carbon fibers are cut and pre-dried, then the carbon fibers are put into a mold, the glue solution prepared in the step S1 is added for impregnation, and the mold is put into a vacuum impregnation tank for protective atmosphere pressure impregnation; and S3, taking out the material after the impregnation is completed, scraping off the glue solution on the surface, and ventilating and horizontally standing until the solvent is volatilized to obtain the ethylene-propylene-diene monomer resin-based carbon fiber prepreg. According to the method provided by the invention, the interface bonding performance of the ethylene-propylene-diene monomer resin-based carbon fiber prepreg and the ethylene-propylene-diene monomer resin is improved by controlling the viscosity and the dosage of the dipping glue solution and adopting the glue solution scraping step.

Description

Technical Field

[0001] The invention relates to the technical field of thermal insulation and ablation-resistant materials for solid rocket engines, and in particular to a method for molding EPDM resin-based carbon fiber prepreg. Background Art

[0002] Solid rocket engine insulation materials can effectively prevent the high-temperature and high-pressure gas and flames generated by the propellant from damaging the engine casing. Its performance and quality are important factors affecting the reliability of solid rocket engines. Carbon fiber braided reinforced composite materials have high strength, high impact resistance, high temperature resistance and other characteristics, which can significantly improve the ablation and erosion resistance of insulation materials. They are often used as the insulation layer reinforcement layer at the tail of the straight barrel section of the casing and the rear head.

[0003] At present, the main research methods include double vacuum bag impregnation molding process, vacuum pressure tank impregnation molding process, etc. However, EPDM resin has a large polarity, the viscosity of the prepared impregnation glue is uneven and fluctuates greatly, and the vacuum effect accelerates the separation of EPDM and solvent in the impregnation glue, resulting in uneven distribution of the resin matrix. After pressure impregnation, it is easy to adhere to the surface of the carbon fiber braid in an unwetted manner, which seriously affects the molding quality of the prepreg. Summary of the invention

[0004] The invention provides a method for molding an EPDM resin-based carbon fiber prepreg, which can improve the molding stability and the uniformity of the impregnation amount of the EPDM resin-based carbon fiber prepreg.

[0005] The technical solution of the present invention is to provide a method for forming an EPDM resin-based carbon fiber prepreg, comprising the following steps: S1, dissolving EPDM rubber with a solvent to prepare a glue solution; S2, the carbon fiber is cut and pre-baked, then placed in a mold, and the glue prepared in S1 is added for impregnation, and the mold is placed in a vacuum impregnation tank for pressure impregnation in a protective atmosphere; S3. After the impregnation is completed, the material is taken out, the glue on the surface is scraped off, and the material is left to stand in a ventilated horizontal position until the solvent evaporates to obtain an EPDM resin-based carbon fiber prepreg.

[0006] Optionally, the EPDM rubber is cut and dissolved in a solvent; the viscosity of the rubber solution is controlled at 5-7 Pa•s.

[0007] Optionally, stirring is performed during the dissolution process, with a stirring speed of 2000-4000 r / min and a time controlled at 20-45 min.

[0008] Optionally, the carbon fiber is T300 12K carbon fiber, cut into squares.

[0009] Optionally, the carbon fiber pre-baking temperature is 50-60° C., and the pre-baking time is 2-3 hours.

[0010] Optionally, the mold cavity matches the shape of the carbon fiber, and its size exceeds the corresponding size of the carbon fiber to be impregnated by 2-4 cm; during the adhesive impregnation, the height of the adhesive liquid level is 3-5 mm higher than the carbon fiber.

[0011] Optionally, during vacuum impregnation, nitrogen is used for pressurization, the pressure is controlled at 2.0-2.5 MPa, and the pressurization time is controlled at 30-45 min.

[0012] Optionally, when scraping off the glue on the surface in S3, the impregnated carbon fiber material is pulled out horizontally from between two parallel clamping plates, and the distance between the two clamping plates is 1-2 mm higher than the thickness of the carbon fiber.

[0013] Optionally, when scraping off the glue on the surface, both sides of the carbon fiber are pulled upwards once.

[0014] Optionally, the horizontal standing time is 72-108h.

[0015] The present invention has the following beneficial effects: 1. The present invention improves the stability of the dipping amount by controlling the viscosity of the glue solution and coordinating the dipping mold and the amount of glue solution added, thereby solving the problem of material waste caused by the difficulty in quantitative dipping of the glue solution. 2. After the impregnation is completed, the glue scraping operation is added to solve the problem that the surface of the EPDM resin-based carbon fiber prepreg is not impregnated with too much glue and the difference in the amount of glue impregnation in the same batch is large.

[0016] 3. The present invention also effectively improves the molding stability of EPDM resin-based carbon fiber prepreg by controlling the carbon fiber specifications and pre-baking conditions, the impregnation pressure and time of the impregnation tank. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a top view and a front view of the impregnation mold used in the present invention.

[0018] Figure 2 It is the scraping tool used in the present invention.

[0019] Figure 3 It is a photo of EPDM resin-based carbon fiber prepreg, wherein A is prepared by the method of Example 1, and B is prepared by the preparation method of Comparative Example 1.

[0020] Figure 4 It is a schematic diagram of six-point sampling to characterize the uniformity of carbon fiber impregnation. DETAILED DESCRIPTION

[0021] The present invention is described in detail below in conjunction with specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and a specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0022] The experimental methods in the following examples are conventional methods unless otherwise specified. The raw materials, reagents, etc. used in the following examples are commercially available products unless otherwise specified.

[0023] The present invention provides a method for forming an EPDM resin-based carbon fiber prepreg, comprising the following steps: S1, dissolving EPDM rubber with a solvent to prepare a glue solution; S2, the carbon fiber is cut and pre-baked, then placed in a mold, and the glue prepared in S1 is added for impregnation, and the mold is placed in a vacuum impregnation tank for pressure impregnation in a protective atmosphere; S3. After the impregnation is completed, the material is taken out, the glue on the surface is scraped off, and the material is left to stand in a ventilated horizontal position until the solvent evaporates to obtain an EPDM resin-based carbon fiber prepreg.

[0024] In some embodiments, the EPDM rubber is cut and dissolved with a solvent; preferably, it is cut into an area not greater than 1 cm 2 The glue can be quickly dissolved by removing the broken pieces. The viscosity of the glue is controlled at 5-7Pa•s. In addition to EPDM rubber, the glue can also be added with appropriate amounts of phenolic resin, vulcanizing agent and other additives as needed.

[0025] In some embodiments, the carbon fiber is T300 12K carbon fiber, which is cut into squares. In the following embodiments, the carbon fiber is cut into 19 cm*19 cm squares, placed in an oven, and pre-baked at 50-60° C. for 2-3 hours.

[0026] In some embodiments, the mold cavity matches the shape of the carbon fiber, and the size exceeds the corresponding size of the carbon fiber to be impregnated by 2-4 cm; the height of the glue liquid level during the glue impregnation is 3-5 mm higher than the carbon fiber. In the following embodiments, the mold is made of stainless steel, and its structure is as follows Figure 1 As shown, there is a groove matching the shape of the carbon fiber, and the size of the groove is 22cm*22cm. During impregnation, the mold is placed in a tray and hung in a vacuum pressure impregnation tank, and the top cover is closed.

[0027] In some embodiments, during vacuum impregnation, nitrogen is used for pressurization, the pressure is controlled at 2.0-2.5 MPa, and the pressurization time is controlled at 30-45 min.

[0028] In some embodiments, when scraping off the glue on the surface in S3, the impregnated carbon fiber material is pulled out horizontally from between two parallel clamping plates, and the spacing between the two clamping plates is 1-2 mm higher than the thickness of the carbon fiber. The present invention also provides a scraping tool, which includes two parallel stainless steel plates, the spacing between the two stainless steel plates is adjusted by bolts, as shown in FIG. Figure 2 When scraping off the glue on the surface, pull the two sides of the carbon fiber upwards and do it once.

[0029] In some embodiments, after scraping off the glue on the surface, the material is ventilated and left to stand for 72-108 hours.

[0030] The present invention is described in detail below in conjunction with specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and a specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0031] Embodiment 1: (1) Preparation of impregnation glue: Cut the EPDM resin into pieces with an area less than 1 cm 2 The pieces were mixed with solvent and stirred evenly with a high-speed stirrer. The speed was controlled at 2500r / min and the stirring time was controlled at 40min. The viscosity of the mixed EPDM resin-based glue was tested to be 6.5Pa·s.

[0032] (2) Pretreatment of carbon fiber: Select carbon fiber with specification of T300 12K, cut it into 19cm*19cm square, put it in an oven, and pre-bake it at 55℃ for 2h.

[0033] (3) Carbon fiber soaking: Place the carbon fiber in a 22cm*22cm stainless steel mold, add an appropriate amount of impregnation glue until the glue is about 4mm above the carbon fiber. Place the mold in a tray and hang it in a vacuum pressure impregnation tank, and close the top cover.

[0034] (4) Pressurized impregnation: After removing the air from the tank, inject nitrogen. The pressure in the tank is controlled at 2.5 MPa for 30 minutes.

[0035] (5) Scrape off the glue: Take out the prepreg, lay it flat and put it into the scraping tool, and pull it out horizontally from the other end of the tool. Turn the prepreg over and repeat the above steps.

[0036] (6) Ventilation and drying: Place the prepreg in a fume hood and leave it horizontally for 72 hours.

[0037] The relevant properties of the prepreg prepared in this experiment are shown in Table 1, and the actual photos are shown in Figure 3 A. When sampling for uniformity of dipping, ventilate the prepreg to evaporate the solvent, and then Figure 4The method shown is to cut 2 cm diameter discs at six points of the prepreg and weigh them to characterize the uniformity of carbon fiber impregnation. The reference standard for interface performance is QJ 2038.1A-2004 "Test Method for Interface Bonding Strength of Solid Rocket Engine Combustion Chamber".

[0038] Table 1

[0039] Embodiment 2: (1) Preparation of impregnation glue: Cut the EPDM rubber into pieces with an area less than 1 cm 2 Add the solvent to the broken pieces and stir them evenly with a high-speed stirrer. During the stirring process, the speed is controlled at 3000r / min and the time is controlled at 35min. The viscosity of the EPDM resin-based glue liquid is tested to be 7.0Pa·s.

[0040] (2) Pretreatment of carbon fiber: Select carbon fiber with specification of T300 12K, cut it into 19cm*19cm square, put it in an oven, and pre-bake it at 60℃ for 2h.

[0041] (3) Carbon fiber soaking: Place the carbon fiber in a 22cm*22cm stainless steel mold, add an appropriate amount of impregnation glue until the glue is about 3mm above the carbon fiber. Place the mold in a tray and hang it in a vacuum pressure impregnation tank, and close the top cover.

[0042] (4) Pressurized impregnation: After removing the air from the tank, nitrogen is injected. The pressure in the tank is controlled at 2.4 MPa for 35 minutes.

[0043] (5) Scrape off the glue: Take out the prepreg, lay it flat and put it into the scraping tool, and pull it out horizontally from the other end of the tool. Turn the prepreg over and repeat the above steps.

[0044] (6) Ventilation and drying: Place the prepreg in a fume hood and leave it horizontally for 84 hours.

[0045] The relevant properties of the prepreg prepared in this experiment are shown in Table 2.

[0046] Table 2

[0047] Embodiment 3: (1) Preparation of impregnation glue: Cut the EPDM rubber into pieces with an area less than 1 cm 2 The pieces were added with solvent and stirred evenly with a high-speed stirrer. The speed was controlled at 4000r / min and the stirring time was controlled at 20min. The viscosity of the mixed EPDM resin-based glue was tested to be 5.1Pa·s.

[0048] (2) Pretreatment of carbon fiber: Select carbon fiber with specification of T300 12K, cut it into 19cm*19cm square, put it in an oven, and pre-bake it at 50℃ for 3h.

[0049] (3) Carbon fiber soaking: Place the carbon fiber in a 22cm*22cm stainless steel mold, add an appropriate amount of impregnation glue until the glue is about 5mm above the carbon fiber. Place the mold in a tray and hang it in a vacuum pressure impregnation tank, and close the top cover.

[0050] (4) Pressurized impregnation: After removing the air from the tank, inject nitrogen. The pressure in the tank is controlled at 2.0 MPa for 45 minutes.

[0051] (5) Scrape off the glue: Take out the prepreg, lay it flat and put it into the scraping tool, and pull it out horizontally from the other end of the tool. Turn the prepreg over and repeat the above steps.

[0052] (6) Ventilation and drying: Place the prepreg in a fume hood and leave it horizontally for 108 hours.

[0053] Table 3

[0054] Comparative Example 1 (1) Preparation of impregnation glue solution: Put EPDM rubber into the solvent and stir it. The speed is controlled at 6000r / min and the time is controlled at 30min.

[0055] (2) Pretreatment of carbon fiber: Select carbon fiber with specification of T300 12K, cut it into 19cm*19cm square, put it in an oven, and pre-bake it at 50℃ for 1h.

[0056] (3) Carbon fiber immersion: Place the carbon fiber in a container that can be evenly spread, such as a stainless steel basin, and add the impregnation glue until it is completely immersed.

[0057] (4) Pressurized impregnation: After removing the air from the tank, inject nitrogen. The pressure in the tank is controlled at 2.0 MPa for 60 minutes.

[0058] (5) Ventilation and drying: Place the prepreg in a fume hood and leave it horizontally for 96 hours.

[0059] The photo of the prepared prepreg is shown in Figure 3 B.

[0060] from Figure 3It can be seen that the carbon fiber prepreg prepared by the conventional method in Comparative Example 1 is unevenly impregnated with resin, the amount of impregnation in the edge area is significantly lower than that in the middle area, and a large amount of unimpregnated resin exists on the surface of the carbon fiber in an attached manner. However, the carbon fiber prepreg prepared by the method of the present invention has a uniform amount of impregnation in each area, and the impregnation glue attached to the surface has been completely scraped off.

[0061] Comparative Example 2 Based on Example 1, the only difference is that when preparing the glue solution, the amount of EPDM rubber used is reduced and the amount of solvent used is increased to control the viscosity of the glue solution to 3.5 Pa•s.

[0062] The appearance of the obtained prepreg is as follows Figure 3 C, the performance is shown in Table 4. There is no excess glue on the surface, but the viscosity of the glue is too low to make it difficult to wet and adhere. The amount of glue is far lower than the required value, and the interface performance is poor.

[0063] Table 4

[0064] Comparative Example 3 Based on Example 1, the only difference is that when preparing the glue solution, the amount of EPDM rubber is increased and the amount of solvent is reduced to control the viscosity of the glue solution to 7.8 Pa•s.

[0065] The appearance of the obtained prepreg is as follows Figure 3 D, the performance is shown in Table 5. The viscosity of the glue is relatively large and it is difficult to scrape it off evenly, resulting in glue adhesion on the surface, a high amount of glue dipping, and poor batch stability.

[0066] Table 5

[0067] Comparative Example 4 The same as Example 1, except that a manual scraper is used to scrape off the glue in step (5).

[0068] The appearance of the obtained prepreg is as follows Figure 3 E, the performance is shown in Table 6. The scraping effect of the manual scraper depends on the operator, and there are instabilities and differences, resulting in poor uniformity of the glue dipping amount.

[0069] Table 6

[0070] Comparative Example 5 The same as Example 1, except that during the soaking of the carbon fiber in step (3), the liquid level of the adhesive is 1 cm higher than the carbon fiber.

[0071] The appearance of the obtained prepreg is as follows Figure 3F, and the properties are shown in Table 7. The amount of glue impregnation is relatively uniform, and there is no obvious excess glue on the surface, but the amount of glue impregnation is high.

[0072] Table 7

[0073] The above embodiments describe the preferred implementation of the present invention, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for molding EPDM resin-based carbon fiber prepreg, characterized in that: The following steps are involved: S1, dissolving EPDM rubber with a solvent to prepare a glue solution; S2, the carbon fiber is cut and pre-baked, then placed in a mold, and the glue prepared in S1 is added for impregnation, and the mold is placed in a vacuum impregnation tank for pressure impregnation in a protective atmosphere; S3. After the impregnation is completed, the material is taken out, the glue on the surface is scraped off, and the material is left to stand in a ventilated horizontal position until the solvent evaporates to obtain an EPDM resin-based carbon fiber prepreg.

2. The molding method according to claim 1, characterized in that: After cutting, the EPDM rubber is dissolved with a solvent; the viscosity of the rubber solution is controlled at 5-7 Pa•s.

3. The molding method according to claim 1, characterized in that: Stirring is performed during the dissolution process, with a stirring speed of 2000-4000 r / min and a time controllable within 20-45 min.

4. The molding method according to claim 1, characterized in that: The carbon fiber is T300 12K carbon fiber, which is cut into squares.

5. The molding method according to claim 1, characterized in that: The pre-baking temperature of carbon fiber is 50-60°C and the pre-baking time is 2-3h.

6. The molding method according to claim 1, characterized in that: The mold cavity matches the shape of the carbon fiber, and its size exceeds the corresponding size of the carbon fiber to be impregnated by 2-4 cm; when the glue is impregnated, the height of the glue liquid level is 3-5 mm higher than the carbon fiber.

7. The molding method according to claim 1, characterized in that: During vacuum impregnation, nitrogen is used for pressurization, the pressure is controlled at 2.0-2.5MPa, and the pressurization time is controlled at 30-45min.

8. The molding method according to any one of claims 1 to 7, characterized in that: When scraping off the glue on the surface in S3, the impregnated carbon fiber material is pulled horizontally out from between two parallel clamping plates, and the distance between the two clamping plates is 1-2 mm higher than the thickness of the carbon fiber.

9. The molding method according to claim 8, characterized in that: When scraping off the glue on the surface, pull both sides of the carbon fiber upwards once.

10. The molding method according to any one of claims 1 to 7, characterized in that: The horizontal standing time is 72-108h.

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