A core-shell composite film material and a preparation method and application thereof

Abstract

This invention discloses a core-shell composite thin film material, its preparation method, and its application. The material is composed of composite fibers with a core-shell structure. The core layer of the composite fibers is a PDCPD / SBS mixed nanofiber, whose main components include styrene-butadiene-styrene block copolymer (SBS) and PDCPD. The shell layer of the composite fibers is a polyethersulfone hollow fiber, whose main component is polyethersulfone. By laying the core-shell composite thin film material between carbon fiber layers, two toughening components can be introduced simultaneously, constructing a multi-scale toughening phase-matrix microstructure, ultimately achieving a significant improvement in the interlaminar fracture toughness of the carbon fiber composite material.

Description

Technical Field

[0001] This invention belongs to the field of composite materials, specifically relating to a core-shell composite thin film material, its preparation method, and its application. Background Technology

[0002] Carbon fiber / epoxy resin (CF / EP) composites are an important branch of CF reinforced composites. In recent years, with the deepening understanding of EP / CF composites, their excellent comprehensive properties, such as high specific strength, high specific modulus, strong designability, corrosion resistance, fatigue resistance, and ease of integral molding, have led to their widespread application in the aerospace field, prompting their rapid expansion into other fields and a continuous increase in usage.

[0003] However, the inherent brittleness of epoxy resin results in low toughness in composite materials based on it, making them susceptible to impact damage and delamination failure, which limits their further applications. Therefore, how to increase the toughness of epoxy resin to improve the overall performance of liquid-molded composite materials has significant theoretical and practical value, and has become an important research topic in the field of composite materials.

[0004] CN113265117A discloses an epoxy resin composite material in which carbon fiber components and a core-shell structure component are uniformly dispersed in the epoxy resin component to improve the toughness of the epoxy resin composite material. The core-shell structure component, which provides the toughening effect, is a rubber-based core component. Coating materials selected from any one of polyvinylpyrrolidone, polyvinyl alcohol, low-density polyethylene, and polymethyl methacrylate do not have a toughening effect.

[0005] It has been proven that toughening epoxy resins by adding dicyclopentadiene curing systems to epoxy groups is indeed feasible, but it is only applicable to epoxy anhydride systems. When the epoxy system contains amine curing agents, the Grubbs catalyst will be deactivated, and dicyclopentadiene (DCPD) will not be able to undergo ring-opening metathesis polymerization. In other words, it is not feasible to toughen amine-cured epoxy resins with polydicyclopentadiene (PDCPD). Summary of the Invention

[0006] To address the aforementioned problems in the existing technology, this invention provides a core-shell composite thin film material and its preparation method.

[0007] This invention provides a core-shell composite thin film material, which is composed of composite fibers having a core-shell structure, wherein...

[0008] The core layer of the composite fiber is a PDCPD / SBS hybrid nanofiber, and its main components include styrene-butadiene-styrene block copolymer (SBS) and PDCPD.

[0009] The shell of the composite fiber is a polyethersulfone hollow fiber, and the main component includes polyethersulfone.

[0010] Preferably, the shell thickness accounts for 30% to 45% of the total diameter of the composite fiber.

[0011] This invention also provides a method for preparing a core-shell composite thin film material, comprising the following steps:

[0012] (1) Prepare the core spinning solution and the shell spinning solution separately:

[0013] Styrene-butadiene-styrene block copolymer (SBS) and DCPD are dissolved in organic solvent A, and Grubbs catalyst and retarder are added to obtain core spinning solution;

[0014] Polyethersulfone was dissolved in organic solvent B to obtain a shell spinning solution;

[0015] (2) The composite film is prepared by using coaxial electrospinning technology. Specifically, during electrospinning, the core spinning solution is injected into the inner needle of the coaxial needle, and the shell spinning solution is injected into the outer needle of the coaxial needle, so that the core spinning solution and the shell spinning solution are electrospinned at the same time to form a composite film with a core-shell structure.

[0016] (3) The above composite film is dried to remove the residual solvent in the film. In the core layer, DCDP is polymerized under the action of G rubbs catalyst to form PDCPD, thereby obtaining a core-shell composite film material.

[0017] Preferably, in the core spinning solution, the SBS mass concentration is 3%–5%, the SBS molecular weight is 80,000–300,000, and the DCPD mass concentration is 50%–60%. Preferably, the mass ratio of styrene to butadiene in the SBS is 30:70–40:60. Preferably, the purity of the DCPD is 96%–99%.

[0018] Preferably, the organic solvent A is one of dichloromethane, xylene, and trichloromethane.

[0019] Preferably, the molar ratio of the Grubbs catalyst to DCPD is 1:5000 to 1:20000. Preferably, the purity of the Grubbs catalyst is 96% to 99%. Preferably, the Grubbs catalyst is a second-generation Grubbs catalyst.

[0020] Preferably, the retarder is at least one of tributyl phosphite, trimethyl phosphite, and triethyl phosphite, and the molar ratio of the retarder to DCPD is 1:1000 to 1:5000.

[0021] Preferably, the polyethersulfone mass concentration in the shell spinning solution is 20-30%. Preferably, the molecular weight of the polyethersulfone is 50,000 to 80,000.

[0022] Preferably, organic solvent B is one or a mixture of two of NMP, DMF, and DMSO.

[0023] Preferably, the electrospinning parameters are controlled as follows: the injection speed of the shell spinning solution is set to 0.5-1.0 ml / h, the injection speed of the core spinning solution is set to 0.05-0.10 ml / h, the positive pressure is 10-30 KV, the negative pressure is -1 KV; the temperature is 25-40℃, and the humidity is 40%-60%.

[0024] Preferably, the drying temperature is 60-90°C and the drying time is 20-60 minutes.

[0025] The present invention also provides a carbon fiber composite material comprising at least two carbon fiber layers and at least one core-shell composite film material sandwiched between the carbon fiber layers; wherein the carbon fiber layers and the core-shell composite film material are filled with epoxy resin, so that the layers are tightly bonded to form an integrated structure.

[0026] The present invention also provides a method for preparing carbon fiber composite material, comprising the following steps: preparing at least two layers of carbon fiber, laying the composite film material between the carbon fiber layers, injecting bisphenol A type epoxy resin in combination with an amine curing agent, and performing curing treatment to obtain carbon fiber composite material.

[0027] Specifically, the amine curing agent is diethyltoluenediamine, and the curing treatment is performed at a temperature of 120°C for 4 hours. The beneficial effects of this invention are:

[0028] This invention employs coaxial electrospinning to prepare composite thin film materials with core-shell nanofiber structures. Different types of spinning solutions are advanced between the core and shell layers using a coaxial needle to achieve the nanofiber coating structure. This technology can protect the DCPD / G rubbs catalyst system. A polyethersulfone shell layer, which can dissolve in epoxy resin at high temperatures, is coated on the outer layer, while the core layer is an insoluble, high-toughness, rapidly curing resin. Simultaneously, two toughening mechanisms are introduced to construct a multi-scale toughening phase-matrix microstructure, ultimately achieving synergistic toughening of the epoxy resin composite material. Detailed Implementation

[0029] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims. Unless otherwise stated, all parts and percentages in the following embodiments are by weight.

[0030] Example 1

[0031] Step 1: Prepare a solution by mixing SBS (molecular weight 80,000), DCPD (purity 99%) with a styrene-butadiene mass ratio of 30:70, and dichloromethane. After the system becomes clear and transparent, add Grubbs 2nd generation catalyst (purity 97%) and tributyl phosphite at a molar ratio of 1:5000 to DCPD to obtain the core spinning solution. In this core spinning solution, the mass concentration of SBS is 5%, and the mass concentration of DCPD is 50%.

[0032] Step 2: Take polyethersulfone with a molecular weight of 55,000 and prepare a solution with NMP to obtain a shell spinning solution. The mass concentration of polyethersulfone in the shell spinning solution is 30%.

[0033] Step 3: Spinning is performed using a coaxial needle. The shell spinning solution is added to the outer needle barrel, and the core spinning solution is added to the inner needle barrel. Both the core and shell spinning solutions are electrospun simultaneously to form a composite film with a core-shell structure. The inner needle diameter accounts for 70% of the total needle diameter. The shell spinning solution injection rate is 0.5 ml / h, and the core spinning solution injection rate is 0.1 ml / h. The positive pressure is 20 kV, and the negative pressure is -1 kV; the temperature is 25°C, and the humidity is 40%.

[0034] Step 4: Place the composite film in a 90℃ oven and remove it after 1 hour.

[0035] Example 2

[0036] Step 1: Prepare a solution by mixing SBS (molecular weight 100,000), DCPD (purity 99%) with a styrene-butadiene mass ratio of 40:60, and dichloromethane. After the system becomes clear and transparent, add G Rubbs 2nd generation catalyst (purity 97%) with DCPD at molar ratios of 1:15000 and 1:5000, respectively, along with trimethyl phosphite, to obtain the core spinning solution. In this core spinning solution, the mass concentration of SBS is 3%, and the mass concentration of DCPD is 60%.

[0037] Step 2: Take polyethersulfone with a molecular weight of 55,000 and DMF to prepare a solution to obtain a shell spinning solution with a polyethersulfone mass concentration of 25%.

[0038] Step 3: Spinning is performed using a coaxial needle. The shell spinning solution is added to the outer needle barrel, and the core spinning solution is added to the inner needle barrel, allowing both the core and shell spinning solutions to be electrospun simultaneously, forming a composite film with a core-shell structure. The inner needle diameter accounts for 60% of the total needle diameter. The shell spinning solution injection rate is 0.5 ml / h, and the core spinning solution injection rate is 0.1 ml / h. The positive pressure is 20 kV, and the negative pressure is -1 kV; the temperature is 25°C, and the humidity is 40%.

[0039] Step 4: Place the composite film in a 60℃ oven and remove it after 20 minutes.

[0040] Example 3

[0041] Step 1: Prepare a solution by mixing SBS (molecular weight 100,000), DCPD (purity 99%) with a styrene-butadiene mass ratio of 40:60, and dichloromethane. After the system becomes clear and transparent, add Grubbs 2nd generation catalyst (purity 97%) with DCPD at molar ratios of 1:20000 and 1:1000, respectively, along with triethyl phosphite, to obtain the core spinning solution. In this core spinning solution, the mass concentration of SBS is 3%, and the mass concentration of DCPD is 50%.

[0042] Step 2: Take polyethersulfone with a molecular weight of 55,000 and DMF to prepare a solution to obtain a shell spinning solution with a polyethersulfone mass concentration of 20%.

[0043] Step 3: Spinning is performed using a coaxial needle. The shell spinning solution is added to the outer needle barrel, and the core spinning solution is added to the inner needle barrel, allowing both the core and shell spinning solutions to be electrospun simultaneously, forming a composite film with a core-shell structure. The inner needle diameter accounts for 65% of the total needle diameter. The shell spinning solution injection rate is 0.5 ml / h, and the core spinning solution injection rate is 0.1 ml / h. The positive pressure is 20 kV, and the negative pressure is -1 kV; the temperature is 25°C, and the humidity is 40%.

[0044] Step 4: Place the composite film in a 60℃ oven and remove it after 20 minutes.

[0045] Comparative Example 1

[0046] Step 1: Take polyethersulfone with a molecular weight of 55,000 and DMF to prepare a spinning solution, and the mass concentration of polyethersulfone in the spinning solution is 20%.

[0047] Step 2: Add the spinning solution from Step 1 into the syringe to perform electrospinning of the polyethersulfone nanofiber mat. During electrospinning, the injection speed is 0.5 ml / h, the positive pressure is 20 kV, the negative pressure is -1 kV, the temperature is 25℃, and the humidity is 40%.

[0048] Step 3: Place the above polyethersulfone nanofiber felt in a 60℃ oven and remove it after 20 minutes.

[0049] Comparative Example 2

[0050] Step 1: Prepare a solution by mixing SBS (molecular weight 80,000), DCPD (purity 99%) with a styrene-butadiene mass ratio of 30:70, and dichloromethane. After the system becomes clear and transparent, add Grubbs 2nd generation catalyst (purity 97%) and tributyl phosphite dropwise at a molar ratio of 1:5000 to DCPD to obtain the spinning solution. In this spinning solution, the mass concentration of SBS is 5%, and the mass concentration of DCPD is 50%.

[0051] Step 2: Add the spinning solution from Step 1 into the syringe to perform electrospinning of the SBS / PDCPD composite nanofiber mat. During electrospinning, the injection speed is 0.1 ml / h, the positive pressure is 20 kV, the negative pressure is -1 kV, the temperature is 25℃, and the humidity is 40%.

[0052] Step 3: Place the fiber felt spun in step 2 in a 90℃ oven and remove it after 1 hour to obtain SBS / PDCPD composite nanofiber felt.

[0053] Carbon fiber composites were prepared using a vacuum-assisted resin infusion (VARI) process. The films (mattes) prepared in the examples or comparative examples were laid on two layers of carbon fiber (Toray T30040B grade carbon fiber, areal density 200 g / m²). 2 Between the layers, bisphenol A type epoxy resin (Nanya NPSN 128, epoxy value 0.51) was injected in combination with amine curing agent (diethyltoluene diamine, E100, Albemarle, USA), and cured at 120℃ for 4 hours. The fracture toughness of the composite material was compared.

[0054] Table 1

[0055] GIC type fracture toughness (ISO 13586-2018) blank sample 421 Example 1 1035 Example 2 1072 Example 3 1012 Comparative Example 1 756 Comparative Example 2 896

Claims

1. A core-shell composite thin film material, composed of composite fibers having a core-shell structure, characterized in that, in, The core layer of the composite fiber is a PDCPD / SBS hybrid nanofiber, and its main components include styrene-butadiene-styrene block copolymer and PDCPD. The shell of the composite fiber is a polyethersulfone hollow fiber, and the main component includes polyethersulfone.

2. The composite thin film material according to claim 1, characterized in that, The shell thickness accounts for 30% to 45% of the total diameter of the composite fiber.

3. The method for preparing the composite thin film material according to claim 1 or 2, characterized in that, Includes the following steps: (1) Prepare core spinning solution and shell spinning solution respectively: Dissolve SBS and DCPD in organic solvent A, and add Grubbs catalyst and retarder to obtain core spinning solution; Polyethersulfone was dissolved in organic solvent B to obtain a shell spinning solution; (2) The composite film is prepared by using coaxial electrospinning technology. Specifically, during electrospinning, the core spinning solution is injected into the inner needle of the coaxial needle, and the shell spinning solution is injected into the outer needle of the coaxial needle, so that the core spinning solution and the shell spinning solution are electrospinned at the same time to form a composite film with a core-shell structure. (3) The above composite film is dried to remove the residual solvent in the film. In the core layer, DCDP is polymerized under the action of Grubbs catalyst to form PDCPD, thereby obtaining a core-shell composite film material.

4. The method according to claim 3, characterized in that, In the core spinning solution, the SBS mass concentration is 3%–5% and the molecular weight is 80,000–300,000; the DCPD mass concentration is 50%–60% and the DCPD purity is 96%–99%, with a mass fraction of 50%–60%; the organic solvent A is one of dichloromethane, xylene, and trichloromethane; the Grubbs catalyst purity is 96%–99% and the molar ratio to DCPD is 1:5000–1:20000; and the retarder is at least one of tributyl phosphite, trimethyl phosphite, and triethyl phosphite, with a molar ratio to DCPD of 1:1000–1:5000.

5. The method according to claim 3, characterized in that, In the shell spinning solution, the polyethersulfone mass concentration is 20-30%, the polyethersulfone molecular weight is 50,000 to 80,000, the organic solvent B is one or a mixture of two of NMP, DMF, and DMSO, and the polyethersulfone mass concentration is 20-25%.

6. The method according to claim 3, characterized in that, The electrospinning parameters are controlled as follows: the injection speed of the shell spinning solution is set to 0.5-1.0 ml / h, the injection speed of the core spinning solution is 0.05-0.10 ml / h, the positive pressure is 10-30 KV, the negative pressure is -1 KV; the temperature is 25-40℃, and the humidity is 40%-60%.

7. The method according to claim 3, characterized in that, The drying temperature is 60-90℃, and the drying time is 20-60 minutes.

8. A carbon fiber composite material, characterized in that, The material comprises at least two carbon fiber layers, with at least one core-shell composite film material as described in claim 1 or 2 sandwiched between the carbon fiber layers; wherein the carbon fiber layers and the core-shell composite film material are filled with epoxy resin, so that the layers are tightly bonded to form an integrated structure.

9. The method for preparing the carbon fiber composite material according to claim 8, characterized in that, The process includes the following steps: preparing at least two layers of carbon fiber, laying the composite film material between the carbon fiber layers, injecting bisphenol A type epoxy resin in combination with an amine curing agent, and then performing a curing treatment to obtain a carbon fiber composite material.

10. The method according to claim 9, characterized in that, The amine curing agent is diethyltoluenediamine, and the curing treatment temperature is 120°C for 4 hours.