High-strength and high-toughness benzoxazine resin-based hot-melt prepreg for thermal insulation and preparation method thereof, benzoxazine resin-based composite material and preparation method thereof

Abstract

The present invention relates to a high-strength and high-toughness benzoxazine resin-based hot-melt prepreg for thermal insulation, a preparation method thereof, and a benzoxazine resin-based composite material and a preparation method thereof. The method comprises the following steps: heating a hot-melt benzoxazine resin, melting it, adding epoxy-terminated silicone and a low-density filler, and stirring evenly to obtain a mixture; forming the mixture into an adhesive film; and laminating the adhesive film with a lightweight fiber-reinforced material, hot-pressing and compounding the film to obtain a benzoxazine resin-based hot-melt prepreg. By proposing a method for preparing the high-strength and high-toughness benzoxazine resin-based hot-melt prepreg for thermal insulation, the technical problem in the prior art that commonly used lightweight composite materials for thermal insulation mainly use phenolic resin as a matrix, and the phenolic resin undergoes a condensation reaction, resulting in high brittleness of the cured product and low product strength is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of composite material thermal insulation, and in particular to a high-strength and high-toughness benzoxazine resin-based hot-melt prepreg for thermal insulation and a preparation method thereof, and a benzoxazine resin-based composite material and a preparation method thereof. Background Art

[0002] Driven by the need to reduce aircraft weight, medium- and low-density phenolic resin-based composites are increasingly being used in the thermal protection systems of new-generation hypersonic ballistic missiles, following traditional glass fiber / phenolic composites. Currently, commonly used lightweight thermal insulation composites primarily use phenolic resin as a matrix. Phenolic resins undergo a condensation reaction, resulting in high brittleness and low product weight. While various methods have been used to improve the toughness of these composites using tough phenolic resins, the strength issue remains unresolved.

[0003] Patent CN 109721762 discloses a resin-based heat-insulating composite material and its preparation method. Based on the hot-melt prepreg molding process, the material density is reduced by adding a self-expanding filler member whose volume expands when heated. However, this method uses closed mold molding, which has high requirements for the mold, and the mechanical strength of the obtained composite material is low. Patent CN111574808 discloses a lightweight heat-insulating composite material and its preparation method. It uses a phenolic resin matrix, lightweight fibers and glass air microspheres to prepare low-density prepreg and composite materials. However, the density of the composite material is relatively high (0.7-1.3g / cm 3 ), and the strength performance is not high.

[0004] Therefore, in order to solve the above problems, the present invention urgently needs to provide a high-strength and high-toughness benzoxazine resin-based hot-melt prepreg for thermal insulation and a preparation method thereof, a benzoxazine resin-based composite material and a preparation method thereof. Summary of the Invention

[0005] The object of the present invention is to provide a high-strength and high-toughness benzoxazine resin-based hot-melt prepreg for thermal insulation and a preparation method thereof, a benzoxazine resin-based composite material and a preparation method thereof. By proposing a preparation method of a high-strength and high-toughness benzoxazine resin-based hot-melt prepreg for thermal insulation, the technical problem that the commonly used lightweight composite materials for thermal insulation in the prior art mainly use phenolic resin as the matrix and the phenolic resin is a condensation reaction, resulting in high brittleness of the cured product and low product strength is solved.

[0006] The present invention provides a method for preparing a high-strength and high-toughness benzoxazine resin-based hot-melt prepreg for thermal insulation, comprising the following steps:

[0007] The hot-melt benzoxazine resin is heated and melted, and then epoxy-terminated silicone and low-density filler are added and stirred to obtain a mixture;

[0008] forming the mixture into a film;

[0009] The adhesive film and the lightweight fiber reinforcement material are stacked and hot-pressed to obtain a benzoxazine resin-based hot-melt prepreg.

[0010] Preferably, the amount of epoxy-terminated silicone added is 15%-45% of the mass of the hot-melt benzoxazine resin.

[0011] Preferably, the addition amount of the low-density filler is 50%-70% of the mass of the hot-melt benzoxazine resin.

[0012] Preferably, the reinforcing material is one of quartz fiber felt, basalt fiber felt, quartz fiber cloth, high silica fiber cloth, alkali-free glass fiber cloth, a mixed cloth woven of quartz fiber and aramid fiber, a mixed cloth woven of glass fiber and aramid fiber, and a mixed cloth woven of quartz fiber and sulfone fiber.

[0013] Preferably, the low-density filler comprises at least one of hollow glass microspheres, expanded microspheres, or phenolic microspheres.

[0014] Preferably, a hot melt coating machine is used to coat the mixture into a film of uniform thickness, the coating temperature is 70-90°C, and the surface density of the film is controlled by adjusting the roller gap and the coating speed, and the coating speed is 5-10m / min.

[0015] Preferably, a hot-melt prepreg machine composite production device is used for hot pressing composite, the pressing roller temperature is 90-120° C., and the composite speed is 5-10 m / min.

[0016] The present invention also provides a benzoxazine resin-based hot-melt prepreg obtained by the method for preparing a high-strength, high-toughness, thermally insulating benzoxazine resin-based hot-melt prepreg as described in any one of the above.

[0017] The present invention also provides a method for preparing a benzoxazine resin-based composite material, wherein the benzoxazine resin-based hot-melt prepreg described above is cured and formed, wherein the curing process comprises:

[0018] Heat to 100°C at a rate of 30°C / h and keep warm for 2h;

[0019] Heat to 130°C at a rate of 20°C / h, pressure (0.3-1.5) MPa, and hold for 1.5 h;

[0020] The temperature was raised to 180°C at a heating rate of 10°C / h, the pressure was (0.3-1.5) MPa, and the temperature was kept at this temperature for 10 hours.

[0021] The present invention also provides a benzoxazine resin-based composite material obtained based on the above-mentioned method for preparing the benzoxazine resin-based composite material.

[0022] The high-strength and high-toughness benzoxazine resin-based hot-melt prepreg for thermal insulation and its preparation method, as well as the benzoxazine resin-based composite material and its preparation method provided by the present invention have the following improvements compared with the prior art:

[0023] 1. The method for preparing a high-strength and high-toughness thermal insulating benzoxazine resin-based hot-melt prepreg proposed in the present invention significantly reduces the density of the benzoxazine resin-based composite material by introducing lightweight fiber reinforcement materials and low-density fillers, while having the significant characteristic of low thermal conductivity. In addition, by using hot-melt benzoxazine as the resin matrix, the strength of the composite material is significantly improved compared to the phenolic system, achieving the high strength goal. The introduction of epoxy-terminated silicone regulates the overall toughness of the composite material, which not only reduces the curing temperature of benzoxazine, but also improves the toughness of the composite material, achieving the goal of high toughness.

[0024] 2. The method for preparing a high-strength and high-toughness benzoxazine resin-based hot-melt prepreg for thermal insulation proposed in the present invention adopts a hot-melt method to prepare the prepreg, which can more accurately control the resin content of the prepreg. It has the advantages of a simple prepreg preparation process, high production efficiency, and the obtained composite material has both high strength and toughness.

[0025] 3. The addition amount of the epoxy-terminated silicone of the present invention can be selected in a wide range. Preferably, the addition amount of the toughness modifier epoxy-terminated silicone is 15%-45% of the mass fraction of the hot-melt benzoxazine resin. When this addition ratio is adopted, the mechanical strength and toughness of the benzoxazine resin-based composite material are greatly improved.

[0026] 4. The low-density filler content of the present invention can be selected over a wide range. Preferably, the low-density functional filler content is 50%-70% of the mass of the hot-melt benzoxazine resin. Studies have found that when the low-density functional filler content exceeds 70%, dispersibility decreases, mixing becomes uneven, and coating processability deteriorates. When the low-density functional filler content is less than 50%, the composite material density is high, failing to achieve a significant density reduction effect. DETAILED DESCRIPTION

[0027] The technical solution of the present invention will be described clearly and completely below. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0028] The present invention provides a method for preparing a high-strength and high-toughness benzoxazine resin-based hot-melt prepreg for thermal insulation, comprising the following steps:

[0029] S1) heating a hot-melt benzoxazine resin, melting it, adding epoxy-terminated silicone and a low-density filler, and stirring until uniform to obtain a mixture;

[0030] S2) forming the mixture into a film;

[0031] S3) Laminating the adhesive film and the lightweight fiber-reinforced material, and hot-pressing and compounding them to obtain a benzoxazine resin-based hot-melt prepreg.

[0032] Preferably, the amount of epoxy-terminated silicone added is 15%-45% of the mass of the hot-melt benzoxazine resin.

[0033] Preferably, the addition amount of the low-density filler is 50%-70% of the mass of the hot-melt benzoxazine resin.

[0034] Preferably, the reinforcing material is one of quartz fiber felt, basalt fiber felt, quartz fiber cloth, high silica fiber cloth, alkali-free glass fiber cloth, a mixed cloth woven of quartz fiber and aramid fiber, a mixed cloth woven of glass fiber and aramid fiber, and a mixed cloth woven of quartz fiber and sulfone fiber.

[0035] Preferably, the low-density filler comprises at least one of hollow glass microspheres, expanded microspheres, or phenolic microspheres.

[0036] Preferably, a hot melt coating machine is used to coat the mixture into a film of uniform thickness, the coating temperature is 70-90°C, and the surface density of the film is controlled by adjusting the roller gap and the coating speed, and the coating speed is 5-10m / min.

[0037] Preferably, a hot-melt prepreg machine composite production device is used for hot pressing composite, the pressing roller temperature is 90-120° C., and the composite speed is 5-10 m / min.

[0038] The present invention also provides a benzoxazine resin-based hot-melt prepreg obtained by the method for preparing a high-strength, high-toughness, thermally insulating benzoxazine resin-based hot-melt prepreg as described in any one of the above.

[0039] The present invention also provides a method for preparing a benzoxazine resin-based composite material, wherein the benzoxazine resin-based hot-melt prepreg described above is cured and formed, wherein the curing process comprises:

[0040] Heat to 100°C at a rate of 30°C / h and keep warm for 2h;

[0041] Heat to 130°C at a rate of 20°C / h, pressure (0.3-1.5) MPa, and hold for 1.5 h;

[0042] The temperature was raised to 180°C at a heating rate of 10°C / h, the pressure was (0.3-1.5) MPa, and the temperature was kept at this temperature for 10 hours.

[0043] The present invention also provides a benzoxazine resin-based composite material obtained based on the above-mentioned method for preparing the benzoxazine resin-based composite material.

[0044] The present invention proposes a method for preparing a high-strength and high-toughness thermal insulating benzoxazine resin-based hot-melt prepreg. By introducing lightweight fiber reinforcement materials and low-density fillers, the density of the benzoxazine resin-based composite material is significantly reduced, while having the significant characteristic of low thermal conductivity. In addition, by using hot-melt benzoxazine as the resin matrix, the strength of the composite material is significantly improved compared to the phenolic system, achieving the high strength goal. The introduction of epoxy-terminated silicone regulates the overall toughness of the composite material, which not only reduces the curing temperature of benzoxazine, but also improves the toughness of the composite material, achieving the goal of high toughness.

[0045] The present invention proposes a method for preparing a high-strength and high-toughness benzoxazine resin-based hot-melt prepreg for thermal insulation. By preparing the prepreg using a hot-melt method, the resin content of the prepreg can be more accurately controlled. The method has the advantages of a simple prepreg preparation process, high production efficiency, and the obtained composite material has both high strength and toughness.

[0046] The addition amount of the epoxy-terminated silicone in the present invention can be selected in a wide range. The addition amount of the toughness modifier epoxy-terminated silicone is 15%-45% of the mass fraction of the hot-melt benzoxazine resin. When this addition ratio is adopted, the mechanical strength and toughness of the benzoxazine resin-based composite material are greatly improved. Studies have found that when the content of the epoxy-terminated silicone is higher than 45%, the preparation processability and dispersibility are reduced; when the addition amount of the toughness modifier is lower than 15%, the toughening effect is not obvious.

[0047] The low-density filler of the present invention can be added in a wide range of amounts. Preferably, the low-density functional filler is added in an amount of 50%-70% by mass of the hot-melt benzoxazine resin. Studies have found that when the low-density functional filler content exceeds 70%, dispersibility decreases, mixing becomes uneven, and the coating processability deteriorates. When the low-density functional filler content is less than 50%, the composite material density is high and a significant density reduction effect is not achieved. When the low-density filler content is 60%-65% by mass of the hot-melt benzoxazine resin, the prepreg preparation processability is good, and the composite material density ranges from 0.45-0.5g / cm 3 .

[0048] Example 1

[0049] The method for preparing the high-strength and high-toughness thermal insulation benzoxazine resin-based hot-melt prepreg proposed in this embodiment includes the following steps:

[0050] 101) heating a hot melt benzoxazine resin at 70° C. for 2 hours, and after melting, adding epoxy-terminated silicone and a low-density filler, and stirring uniformly using a planetary stirrer to obtain a mixture; wherein the low-density filler is hollow glass microspheres, the amount of epoxy-terminated silicone added is 45% by weight of the benzoxazine resin, and the amount of low-density filler added is 70% by weight of the benzoxazine resin;

[0051] 102) The mixed material was made into a film using a hot melt prepreg machine, wherein the coating temperature was 75°C, and the coating speed was adjusted to 8m / min by adjusting the roller gap and coating speed, and the film surface density was controlled to be 150g / m 2 ;

[0052] 103) The adhesive film and the lightweight fiber reinforcement material are stacked and hot-pressed to obtain a benzoxazine resin-based hot-melt prepreg, wherein a layer of adhesive film is placed on the upper and lower sides of the lightweight fiber reinforcement material, the lightweight fiber reinforcement material is quartz fiber cloth, and hot-pressed composite production equipment is used for hot-melt prepreg composite production. The pressing roller temperature is controlled at 90°C, and the composite speed is controlled at 8m / min. The lightweight fiber reinforcement material accounts for 15% of the benzoxazine resin-based hot-melt prepreg.

[0053] 104) This embodiment also provides a method for preparing a benzoxazine resin-based composite material, wherein the benzoxazine resin-based hot-melt prepreg described above is laid flat, sequentially coated with adhesive felt and a vacuum bag, placed in an autoclave, evacuated to a vacuum degree of 10 kPa, maintained at this vacuum degree for 20 minutes, and cured to obtain a benzoxazine resin-based composite material; wherein the curing process includes:

[0054] Heat to 100°C at a rate of 30°C / h and keep warm for 2h;

[0055] Heat to 130°C at a rate of 20°C / h, pressure 1.0 MPa, and hold for 1.5 h;

[0056] The temperature was raised to 180°C at a heating rate of 10°C / h, the pressure was 1.0 MPa, and the mixture was kept at this temperature for 10 h.

[0057] The physical properties of the benzoxazine resin-based composites are shown in Table 1.

[0058] From Table 1, the benzoxazine resin-based composite material obtained by the present invention has a density of 0.44 g / cm 3 , tensile strength is 31.3MPa, high tensile strength, elongation at break is 3.51%, thermal conductivity is 0.11W / m·K, lightweight, high strength, high toughness and low thermal conductivity.

[0059] Example 2

[0060] The preparation method of the benzoxazine resin-based composite material in this example is the same as that in Example 1, except that the amount of epoxy-terminated silicone added is 15% of the mass of the benzoxazine resin. The physical properties of the obtained benzoxazine resin-based composite material are shown in Table 1.

[0061] As shown in Table 1, the benzoxazine resin-based composite material obtained in this embodiment is lightweight, has high strength, high toughness and low thermal conductivity. Compared with Example 1, the elongation at break is reduced due to the reduced addition amount of epoxy-terminated silicone.

[0062] Example 3

[0063] The preparation method of the benzoxazine resin-based composite material in this embodiment is the same as that in Example 1, except that the low-density filler accounts for 50% of the mass of the benzoxazine resin. The physical properties of the obtained benzoxazine resin-based composite material are shown in Table 1.

[0064] As shown in Table 1, the benzoxazine resin-based composite material obtained in this embodiment is lightweight, has high strength, high toughness and low thermal conductivity. Compared with Example 1, the density and thermal conductivity of this embodiment are increased due to the reduced amount of low-density filler added.

[0065] Example 4

[0066] The preparation method of the benzoxazine resin-based composite material in this embodiment is the same as that in Example 1, except that the lightweight fiber reinforcement material is a mixed cloth woven of quartz fiber and aramid fiber. The physical properties of the obtained benzoxazine resin-based composite material are shown in Table 1.

[0067] Example 5

[0068] The preparation method of the benzoxazine resin-based composite material in this example is the same as that in Example 1, except that the low-density filler is expanded microspheres. The physical properties of the obtained benzoxazine resin-based composite material are shown in Table 1.

[0069] The density and thermal conductivity of the benzoxazine resin-based composite material obtained in this embodiment are substantially the same as those in Example 1, indicating that expanded microspheres can also be used as low-density fillers; in some embodiments, phenolic microspheres can also be used to provide a low-thermal-conductivity, lightweight benzoxazine resin-based composite material.

[0070] Comparative Example 1

[0071] The preparation steps of this comparative example are the same as those of Example 1, except that the hot-melt thermosetting benzoxazine resin is replaced with a hot-melt thermosetting phenolic resin. The obtained composite material is shown in Table 1.

[0072] Compared with Example 1, the composite material obtained in this example has low tensile strength and elongation at break, and poor toughness, because the hot-melt thermosetting benzoxazine resin is replaced with a hot-melt thermosetting phenolic resin.

[0073] Comparative Example 2

[0074] The preparation steps of this comparative example are the same as those of Example 1, except that epoxy-terminated silicone is not added. The obtained composite material is shown in Table 1.

[0075] Compared with Example 1, the composite material obtained in this example has lower tensile strength and elongation at break and poor toughness due to the absence of epoxy-terminated silicone. This shows that the addition of epoxy-terminated silicone has a significant effect on the toughness of the composite material.

[0076] Comparative Example 3

[0077] The preparation steps of this comparative example are the same as those of Example 1, except that no low-density filler is added. The obtained composite material is shown in Table 1.

[0078] Compared with Example 1, the composite material obtained in this example has high density and high thermal conductivity because no low-density filler is added, and a lightweight composite material with low thermal conductivity cannot be obtained.

[0079] Comparative Example 4

[0080] The preparation steps of this comparative example are the same as those of Example 1, except that epoxy-terminated silicone and low-density filler are not added. The obtained composite material is shown in Table 1.

[0081] Compared with Example 1, the composite material obtained in this example has high density, poor toughness and high thermal conductivity because epoxy-terminated silicone and low-density filler are not added.

[0082] Comparative Example 5

[0083] The preparation steps of this comparative example are the same as those of Example 1, except that the epoxy-terminated silicone is replaced with phenyl-terminated silicone. The obtained composite material is shown in Table 1.

[0084] Compared with Example 1, the composite material obtained in this example has significantly lower tensile strength and elongation at break than Example 1 due to the use of phenyl-terminated silicone, indicating that the addition of epoxy-terminated silicone significantly improves the tensile strength and toughness of the composite material.

[0085] Table 1 Physical properties of composite materials

[0086]

[0087]

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a high-strength, high-toughness, thermally insulating benzoxazine resin-based hot-melt prepreg, characterized by: The following steps are involved: The hot-melt benzoxazine resin is heated and melted, and then epoxy-terminated silicone and low-density filler are added and stirred to obtain a mixture; forming the mixture into a film; The adhesive film and the lightweight fiber reinforcement material are stacked and hot-pressed to obtain a benzoxazine resin-based hot-melt prepreg; The amount of epoxy-terminated silicone added is 15%-45% of the mass of the hot-melt benzoxazine resin; The addition amount of the low-density filler is 50%-70% of the mass of the hot-melt benzoxazine resin.

2. The method for preparing a high-strength, high-toughness, thermally insulating benzoxazine resin-based hot-melt prepreg according to claim 1, characterized in that: The reinforcing material is one of quartz fiber felt, basalt fiber felt, quartz fiber cloth, high silica fiber cloth, alkali-free glass fiber cloth, a mixed cloth woven by quartz fiber and aramid fiber, a mixed cloth woven by glass fiber and aramid fiber, and a mixed cloth woven by quartz fiber and sulfone fiber.

3. The method for preparing a high-strength, high-toughness, thermally insulating benzoxazine resin-based hot-melt prepreg according to claim 1, wherein: The low-density filler includes at least one of hollow glass microspheres, expanded microspheres, or phenolic microspheres.

4. The method for preparing a high-strength, high-toughness, thermally insulating benzoxazine resin-based hot-melt prepreg according to claim 1, wherein: The mixed material is coated into a film of uniform thickness using a hot melt coating machine at a coating temperature of 70-90°C. The surface density of the film is controlled by adjusting the roller gap and coating speed at a coating speed of 5-10m / min.

5. The method for preparing a high-strength, high-toughness, thermally insulating benzoxazine resin-based hot-melt prepreg according to claim 1, wherein: The hot-melt prepreg machine composite production device is used for hot pressing composite, the pressing roller temperature is 90-120°C, and the composite speed is 5-10 m / min.

6. A benzoxazine resin-based hot-melt prepreg obtained by the method for preparing a high-strength and high-toughness benzoxazine resin-based hot-melt prepreg for thermal insulation according to any one of claims 1 to 5.

7. A method for preparing a benzoxazine resin-based composite material, characterized in that: The benzoxazine resin-based hot-melt prepreg according to claim 6 is cured and formed, wherein the curing process comprises: The temperature was raised to 100°C at a heating rate of 30°C / h and kept at this temperature for 2 h; Heat to 130°C at a rate of 20°C / h, pressure of (0.3-1.5) MPa, and hold for 1.5 h; Heat to 180°C at a rate of 10°C / h, pressure of (0.3-1.5) MPa, and keep warm for 10 hours.

8. A benzoxazine resin-based composite material obtained based on the preparation method of the benzoxazine resin-based composite material according to claim 7.

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