Thermoplastic adhesive film as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of composite materials, and discloses a thermoplastic adhesive film as well as a preparation method and application thereof. The thermoplastic adhesive film comprises 50-90 parts of epoxy resin, 5-20 parts of a thermoplastic polymer, 1-20 parts of a curing agent, 1-5 parts of a curing accelerator and 5-20 parts of reinforcing filler. The matrix resin is epoxy resin which has good molecular structure polarity, adhesion and wettability with a composite material, so that high strength is ensured; the mixing capacity of the thermoplastic plastic and the epoxy resin is high, so that the bonding capacity and viscosity of the epoxy resin are improved; primary amine or bis-secondary amine is adopted as the curing agent, so that the adhesive film has a thermoplastic property and has secondary processing capacity; the curing accelerator ensures that the cured epoxy resin is a linear thermoplastic polymer; and the reinforcing filler can improve the mechanical property and the bonding strength of the adhesive film. The thermoplastic adhesive film disclosed by the invention has good bonding strength, rapid curing capacity, thermal disassembly capacity and reutilization capacity.

Description

Technical Field

[0001] The present invention relates to the technical field of composite materials, and in particular to a thermoplastic film and a preparation method and application thereof. Background Art

[0002] In recent years, with the development of aerospace, automobile, rail transportation and other fields, the application of lightweight and high-strength fiber-reinforced polymer-based composite materials in the above fields has received widespread attention. However, the poor secondary processability of fiber-reinforced composite materials makes high-efficiency connection and forming technology one of the important guarantees for the structural strength and stability of equipment. At present, adhesive connection methods that do not damage the structural integrity of composite materials, have uniform stress distribution and good fatigue resistance are widely used in composite material connections. However, the commonly used adhesives are mostly thermosetting epoxy resin adhesives, which have slow curing speeds, are difficult to adjust and optimize the connection structure after curing, and have problems with repeated connections.

[0003] One key approach to addressing these issues is to replace the thermosetting epoxy resin adhesives commonly used in composite material bonding with thermoplastic adhesives. However, while existing thermoplastic polymers and thermoplastic hot melt adhesives offer reusability, their bonding strength is far lower than that of commonly used thermosetting epoxy resin adhesives, and their bonding temperature is also higher than that of thermosetting epoxy resin adhesives. For example, CN119842340A discloses a method for preparing a hot melt adhesive that uses APAO polyolefin resin as its primary component and introduces polyethylene wax to lower the thermal bonding temperature. However, due to the weak polarity of the polyolefin's molecular structure, the resulting adhesive exhibits relatively low strength. Another example is CN116285826B, which discloses a polyester hot melt adhesive, its preparation method, and its application. The polyester hot melt adhesive is formulated by compounding three polyester resins with a specific structure to produce a hot melt adhesive with excellent resistance to high and low temperature cycling. However, this hot melt adhesive requires high-temperature preparation conditions of 240-270°C, resulting in relatively weak bonding strength.

[0004] Therefore, developing a thermoplastic adhesive film that can be quickly bonded and connected at a lower temperature, is reusable, and has good adhesion to composite materials to achieve high-efficiency and high-performance connection of fiber-reinforced composite materials is an important technical problem that needs to be urgently solved in this field. Summary of the Invention

[0005] The purpose of the present invention is to provide a thermoplastic film and a preparation method and application thereof, so as to solve the problem of low bonding strength of existing adhesives.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a thermoplastic film comprising the following raw materials in parts by mass:

[0008] 50-90 parts of epoxy resin, 5-20 parts of thermoplastic polymer, 1-20 parts of curing agent, 1-5 parts of curing accelerator, 5-20 parts of reinforcing filler;

[0009] The thermoplastic polymer is one or more of polyethersulfone, polyurethane, polyetheretherketone, and polyvinyl alcohol.

[0010] Preferably, in the above-mentioned thermoplastic film, the epoxy resin is one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, diethylene glycol diglycidyl ether, and poly(propylene glycol) diglycidyl ether.

[0011] Preferably, in the above thermoplastic film, the curing agent is one or more of aniline, methoxyaniline, piperazine, N,N'-dimethylethylenediamine, and ethanolamine.

[0012] Preferably, in the above thermoplastic film, the curing accelerator is one or more of triphenylphosphine, bis(triphenylphosphine)ammonium chloride, 2,4,6-tris(dimethylaminomethyl)phenol, and organic urea.

[0013] Preferably, in the above-mentioned thermoplastic film, the reinforcing filler is one or more of chopped carbon fiber, glass fiber, basalt fiber, carbon nanotube, and graphene.

[0014] The present invention also provides a method for preparing a thermoplastic film, comprising the following steps:

[0015] The epoxy resin and thermoplastic polymer are heated and dissolved under a protective atmosphere to obtain a resin solution; reinforcing fillers are added to the resin solution, and after cooling, a curing agent and a curing accelerator are added and stirred to obtain an adhesive solution; the adhesive solution is mixed using a three-roll mill to obtain a coating solution; and the coating solution is applied to a film to obtain a thermoplastic adhesive film.

[0016] Preferably, in the above-mentioned method for preparing a thermoplastic film, the temperature of the heating and dissolving is 80-150°C; the heating and dissolving process also includes stirring; the stirring speed is 50-200 rpm; the stirring and mixing temperature is 40-50°C; the stirring and mixing speed is 50-100 rpm; and the stirring and mixing time is 10-30 min.

[0017] Preferably, in the above method for preparing a thermoplastic film, the coating speed is 0.5 to 5 m / min.

[0018] The present invention also provides an application of a thermoplastic adhesive film in bonding carbon fiber reinforced polymer-based composite materials, wherein the bonding temperature is 80 to 150° C. and the bonding time is 5 to 20 minutes.

[0019] Preferably, in the above application, the bonding further includes heating and separation, and then secondary bonding; the temperature of the heating and separation is 150-220° C.; the temperature of the secondary bonding is 150-220° C.; and the time of the secondary bonding is 5-20 minutes.

[0020] It can be seen from the above technical solutions that compared with the prior art, the present invention has the following beneficial effects:

[0021] The thermoplastic film of the present invention comprises an epoxy resin matrix whose molecular structure is consistent with that of conventional thermosetting epoxy resin matrices. This provides excellent molecular polarity, adhesion, and wettability with composite materials, ensuring the film's high strength. The introduced thermoplastic plastic exhibits high compatibility with the epoxy resin, enhancing its adhesion and viscosity. The curing agent, a primary amine or a di-secondary amine, renders the cured epoxy resin a linear polymer, ensuring the film's thermoplastic properties and secondary processability. Furthermore, the introduction of a non-reactive curing accelerator increases the curing rate while ensuring the cured epoxy resin is a linear thermoplastic polymer. Reinforcing fillers further enhance the film's mechanical properties and bonding strength. In addition to excellent bonding strength, the thermoplastic film of the present invention also boasts rapid curing, thermal disassembly, and reusability. DETAILED DESCRIPTION

[0022] The present invention provides a thermoplastic film comprising the following raw materials in parts by mass:

[0023] 50-90 parts of epoxy resin, 5-20 parts of thermoplastic polymer, 1-20 parts of curing agent, 1-5 parts of curing accelerator, and 5-20 parts of reinforcing filler.

[0024] In the present invention, the mass fraction of the epoxy resin is preferably 52 to 80 parts, more preferably 57 to 70 parts, and even more preferably 60 parts.

[0025] In the present invention, the mass fraction of the thermoplastic polymer is preferably 7 to 18 parts, more preferably 9 to 15 parts, and even more preferably 10 parts.

[0026] In the present invention, the mass fraction of the curing agent is preferably 5 to 20 parts, more preferably 10 to 19 parts, and even more preferably 18 parts.

[0027] In the present invention, the mass fraction of the curing accelerator is preferably 2 to 5 parts, more preferably 3 to 5 parts, and even more preferably 4 parts.

[0028] In the present invention, the weight percentage of the reinforcing filler is preferably 6 to 15 parts, more preferably 7 to 12 parts, and even more preferably 8 parts.

[0029] In the present invention, the epoxy resin is preferably one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, diethylene glycol diglycidyl ether, and poly(propylene glycol) diglycidyl ether, further preferably bisphenol A epoxy resin or bisphenol F epoxy resin, and more preferably bisphenol F epoxy resin.

[0030] In the present invention, the thermoplastic polymer is preferably one or more of polyethersulfone, polyurethane, polyetheretherketone, and polyvinyl alcohol, more preferably one or more of polyethersulfone, polyurethane, and polyetheretherketone, and more preferably polyethersulfone.

[0031] In the present invention, the curing agent is preferably one or more of aniline, methoxyaniline, piperazine, N,N'-dimethylethylenediamine, and ethanolamine, more preferably one or more of aniline, methoxyaniline, N,N'-dimethylethylenediamine, and ethanolamine, and more preferably a mixture of aniline and ethanolamine.

[0032] In the present invention, the curing accelerator is preferably one or more of triphenylphosphine, bis(triphenylphosphine)ammonium chloride, 2,4,6-tris(dimethylaminomethyl)phenol, and organic urea, more preferably one or more of triphenylphosphine, bis(triphenylphosphine)ammonium chloride, and 2,4,6-tris(dimethylaminomethyl)phenol, and more preferably a mixture of triphenylphosphine and bis(triphenylphosphine)ammonium chloride.

[0033] In the present invention, the reinforcing filler is preferably one or more of chopped carbon fiber, glass fiber, basalt fiber, carbon nanotube, and graphene, further preferably one or more of chopped carbon fiber, glass fiber, and basalt fiber, and more preferably a mixture of chopped carbon fiber and glass fiber.

[0034] The present invention also provides a method for preparing a thermoplastic film, comprising the following steps:

[0035] The epoxy resin and thermoplastic polymer are heated and dissolved under a protective atmosphere to obtain a resin solution; reinforcing fillers are added to the resin solution, and after cooling, a curing agent and a curing accelerator are added and stirred to obtain an adhesive solution; the adhesive solution is mixed using a three-roll mill to obtain a coating solution; and the coating solution is applied to a film to obtain a thermoplastic adhesive film.

[0036] In the present invention, the temperature of the heating and dissolving is preferably 80-150°C, more preferably 90-140°C, and more preferably 120°C; the heating and dissolving process also includes stirring; the stirring speed is preferably 50-200rpm, more preferably 80-150rpm, and more preferably 90rpm.

[0037] In the present invention, the protective atmosphere is preferably nitrogen or argon, more preferably nitrogen.

[0038] In the present invention, the stirring and mixing temperature is preferably 40-50°C, more preferably 40-45°C, and more preferably 40°C; the stirring and mixing speed is preferably 50-100 rpm, more preferably 50-80 rpm, and more preferably 50 rpm; the stirring and mixing time is preferably 10-30 min, more preferably 13-20 min, and more preferably 15 min.

[0039] In the present invention, the distance between the middle roll and the rear roll of the three-roll mill is preferably 0.1 mm.

[0040] In the present invention, the viscosity of the coating liquid at room temperature is preferably 80 to 200 Pa·S, more preferably 100 to 150 Pa·S, and even more preferably 110 Pa·S.

[0041] In the present invention, the coating speed is preferably 0.5-5 m / min, more preferably 0.5-3 m / min, more preferably 0.5 m / min; the coating roller gap is preferably 0.1-1 mm, more preferably 0.1-0.5 mm, more preferably 0.1 mm.

[0042] The present invention also provides an application of a thermoplastic film in bonding carbon fiber reinforced polymer-based composite materials, wherein the bonding temperature is preferably 80 to 150°C, more preferably 85 to 120°C, and more preferably 90°C; the bonding time is preferably 5 to 20 minutes, more preferably 5 to 10 minutes, and more preferably 5 minutes.

[0043] In the present invention, the bonding further includes heating and separation, and then secondary bonding; the temperature of the heating and separation is preferably 150-220°C, more preferably 150-170°C, and more preferably 155°C; the temperature of the secondary bonding is preferably 150-220°C, more preferably 150-180°C, and more preferably 155°C; the time of the secondary bonding is preferably 5-20 minutes, more preferably 8-15 minutes, and more preferably 10 minutes.

[0044] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0045] Example 1

[0046] (1) 600 g of bisphenol A epoxy resin (epoxy value 0.51) and 100 g of polyetheretherketone resin (particle size ≤ 10 μm) were added to a reactor. Under the protection of a nitrogen atmosphere, the mixture was heated and stirred at 130° C. at a stirring speed of 100 rpm for 30 min to obtain a resin solution.

[0047] (2) Add 80 g of chopped carbon fibers (length ≤ 1 mm) to the resin solution, stir evenly, and then lower the temperature to 40 °C;

[0048] (3) Then, 150 g of aniline, 30 g of ethanolamine, and 40 g of triphenylphosphine were added, and the mixture was stirred at 40°C at a speed of 50 rpm for 15 min to obtain a glue solution;

[0049] (4) The glue solution was processed using a three-roll mill, wherein the spacing between the middle roll and the rear roll of the three-roll mill was 0.1 mm, to obtain a coating solution with a viscosity of 120 Pa·s at room temperature;

[0050] (5) applying the coating liquid at a coating speed of 0.5 m / min and a gap between the rubber rollers of 0.1 mm to obtain a film with a thickness of 0.11 mm;

[0051] (6) placing the adhesive film between two layers of carbon fiber reinforced polymer matrix composite materials, heating at 100°C for 10 minutes for bonding, and obtaining a bonded composite material; wherein the carbon fiber reinforced polymer matrix composite material has a thickness of 2 mm, is cross-ply, and is obtained by heating (120°C) and curing the USN15000 prepreg produced by Weihai Guangwei Composite Materials Co., Ltd. through a vacuum bag molding process;

[0052] (7) The bonded composite materials were tested according to GB / T33334-2016 Adhesive Single Lap Tensile Shear Performance Test Method (Composite Material to Composite Material). The tensile shear strength of the composite material to the composite material was 22 MPa.

[0053] (8) Heat the tested composite material to 165°C and use a polytetrafluoroethylene scraper to smooth the bonding area to ensure that the adhesive film in the bonding area is intact;

[0054] (9) heating the sample treated in step (8) at 165° C. for 5 minutes and then cooling to room temperature to obtain a composite material after secondary bonding;

[0055] (10) Repeat step (7), and the tensile shear strength of the composite material after the secondary bonding is 15 MPa.

[0056] In this embodiment, 5 samples were tested for each bonding performance test and the average value was taken.

[0057] Example 2

[0058] (1) 500 g of bisphenol A epoxy resin (epoxy value 0.51), 100 g of polypropylene glycol diglycidyl ether (number average molecular weight 500) and 100 g of polyethersulfone resin (particle size ≤ 10 μm) were added to a reactor and heated and stirred at 120° C. under a nitrogen atmosphere at a stirring speed of 100 rpm for 20 min to obtain a resin solution;

[0059] (2) Add 80 g of chopped carbon fibers (length ≤ 1 mm) to the resin solution, stir evenly, and then lower the temperature to 40 °C;

[0060] (3) Then, 140 g of aniline, 20 g of ethanolamine, 20 g of piperazine, and 40 g of triphenylphosphine were added, and the mixture was stirred at 40°C at a speed of 50 rpm for 15 min to obtain a glue solution;

[0061] (4) The glue solution was processed using a three-roll mill, wherein the spacing between the middle roll and the rear roll of the three-roll mill was 0.1 mm, to obtain a coating solution with a viscosity of 90 Pa·s at room temperature;

[0062] (5) applying the coating liquid at a coating speed of 0.5 m / min and a gap between the rubber rollers of 0.1 mm to obtain a film with a thickness of 0.11 mm;

[0063] (6) placing the adhesive film between two layers of carbon fiber reinforced polymer matrix composite materials, heating at 90°C for 15 minutes for bonding, and obtaining a bonded composite material; wherein the carbon fiber reinforced polymer matrix composite material has a thickness of 2 mm, is cross-ply, and is obtained by heating (120°C) and curing the USN15000 prepreg of Weihai Guangwei Composite Materials Co., Ltd. through a vacuum bag molding process;

[0064] (7) The bonded composite materials were tested according to GB / T33334-2016 Adhesive Single Lap Tensile Shear Performance Test Method (Composite to Composite). The tensile shear strength of the composite to composite material was 22.5 MPa.

[0065] (8) Heat the tested composite material to 150°C and use a polytetrafluoroethylene scraper to smooth the bonding area to ensure that the adhesive film in the bonding area is intact;

[0066] (9) heating the sample treated in step (8) at 150° C. for 5 minutes and then cooling to room temperature to obtain a composite material after secondary bonding;

[0067] (10) Repeat step (7), and the tensile shear strength of the composite material after the secondary bonding is 18.5 MPa.

[0068] In this embodiment, 5 samples were tested for each bonding performance test and the average value was taken.

[0069] Example 3

[0070] (1) 600 g of bisphenol F epoxy resin (epoxy value 0.59) and 100 g of polyethersulfone resin (particle size ≤ 10 μm) were added to a reactor and heated and stirred at 120° C. under a nitrogen atmosphere at a stirring speed of 90 rpm for 20 min to obtain a resin solution;

[0071] (2) Add 40 g of chopped carbon fiber (length ≤ 1 mm) and 40 g of chopped glass fiber (length ≤ 1 mm) to the resin solution, stir evenly, and then reduce the temperature to 40 ° C;

[0072] (3) Then, 130 g of aniline, 50 g of ethanolamine, 20 g of bis(triphenylphosphine)ammonium chloride, and 20 g of triphenylphosphine were added, and the mixture was stirred at 40° C. at a stirring speed of 50 rpm for 15 min to obtain a glue solution;

[0073] (4) The glue solution was processed using a three-roll mill, wherein the spacing between the middle roll and the rear roll of the three-roll mill was 0.1 mm, to obtain a coating solution with a viscosity of 110 Pa·s at room temperature;

[0074] (5) applying the coating liquid at a coating speed of 0.5 m / min and a gap between the rubber rollers of 0.1 mm to obtain a film with a thickness of 0.11 mm;

[0075] (6) placing the adhesive film between two layers of carbon fiber reinforced polymer matrix composite materials, heating at 90°C for 5 minutes for bonding, and obtaining a bonded composite material; wherein the carbon fiber reinforced polymer matrix composite material has a thickness of 2 mm, is cross-ply, and is obtained by heating (120°C) and curing the USN15000 prepreg produced by Weihai Guangwei Composite Materials Co., Ltd. through a vacuum bag molding process;

[0076] (7) The bonded composite materials were tested according to GB / T33334-2016 Adhesive Single Lap Tensile Shear Performance Test Method (Composite Material to Composite Material). The tensile shear strength of the composite material to the composite material was 23 MPa.

[0077] (8) Heat the tested composite material to 155°C and use a polytetrafluoroethylene scraper to smooth the bonding area to ensure that the adhesive film in the bonding area is intact;

[0078] (9) heating the sample treated in step (8) at 155° C. for 5 minutes and then cooling to room temperature to obtain a composite material after secondary bonding;

[0079] (10) Repeat step (7), and the tensile shear strength of the composite material after the secondary bonding is 20.2 MPa.

[0080] In this embodiment, 5 samples were tested for each bonding performance test and the average value was taken.

[0081] In summary, the thermoplastic film provided by the present invention has excellent bonding properties and a fast curing speed by compounding epoxy resin, thermoplastic polymer, curing agent, curing accelerator, and reinforcing filler in specific proportions. Furthermore, the bonded structure can be heated to disassemble and reconnect, thus having a wide range of applications.

[0082] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A thermoplastic film, characterized in that: Contains the following raw materials in parts by weight: 50-90 parts of epoxy resin, 5-20 parts of thermoplastic polymer, 1-20 parts of curing agent, 1-5 parts of curing accelerator, 5-20 parts of reinforcing filler; The thermoplastic polymer is one or more of polyethersulfone, polyurethane, polyetheretherketone, and polyvinyl alcohol.

2. The thermoplastic film according to claim 1, characterized in that: The epoxy resin is one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, diethylene glycol diglycidyl ether, and poly(propylene glycol) diglycidyl ether.

3. The thermoplastic film according to claim 2, characterized in that: The curing agent is one or more of aniline, methoxyaniline, piperazine, N,N'-dimethylethylenediamine, and ethanolamine.

4. The thermoplastic film according to claim 3, characterized in that: The curing accelerator is one or more of triphenylphosphine, bis(triphenylphosphine)ammonium chloride, 2,4,6-tris(dimethylaminomethyl)phenol, and organic urea.

5. The thermoplastic film according to claim 4, characterized in that: The reinforcing filler is one or more of chopped carbon fiber, glass fiber, basalt fiber, carbon nanotube, and graphene.

6. The method for preparing a thermoplastic film according to any one of claims 1 to 5, characterized in that: The following steps are involved: The epoxy resin and thermoplastic polymer are heated and dissolved in a protective atmosphere to obtain a resin solution; reinforcing fillers are added to the resin solution, and after cooling, a curing agent and a curing accelerator are added and stirred to obtain a glue solution; the glue solution is mixed using a three-roll mill to obtain a coating solution; The coating liquid is applied to a film to obtain a thermoplastic film.

7. The method for preparing a thermoplastic film according to claim 6, wherein: The temperature of the heating and dissolving is 80-150°C; the heating and dissolving process also includes stirring; the stirring speed is 50-200rpm; the stirring and mixing temperature is 40-50°C; the stirring and mixing speed is 50-100rpm; and the stirring and mixing time is 10-30min.

8. The method for preparing a thermoplastic film according to claim 6, wherein: The coating speed is 0.5-5 m / min.

9. Use of a thermoplastic adhesive film according to any one of claims 1 to 5 in bonding carbon fiber reinforced polymer-based composite materials, characterized in that: The bonding temperature is 80-150° C.; and the bonding time is 5-20 minutes.

10. The use according to claim 9, characterized in that After the bonding, the process further includes heating and separation, and then secondary bonding; the temperature of the heating and separation is 150-220° C.; the temperature of the secondary bonding is 150-220° C.; and the time of the secondary bonding is 5-20 minutes.