Sizing agent for polycarbonate and carbon fiber composite material

Abstract

The invention relates to a sizing agent for a polycarbonate and carbon fiber composite material. The sizing agent comprises low polycarbonate, a dispersing agent, a stabilizer, epoxy resin, a wetting agent and deionized water, based on the total mass of the solid components being 100%, the low polycarbonate composition comprises 50-60% of low polycarbonate, 10-15% of a dispersant, 10-15% of a stabilizer, 7-29% of epoxy resin and 1-2% of a wetting agent. The number average molecular weight of the low polycarbonate is 2000 to 5000. Preferably, the number-average molecular weight of the low polycarbonate is 3000-5000, and the mass concentration of the sizing agent is 30%-40%. The sizing agent is suitable for sizing recycled carbon fibers, has excellent mechanical properties in reinforcing a composite material of polycarbonate and carbon fibers, is stable, is beneficial to storage, and is suitable for industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of sizing agents for carbon fibers, in particular to a sizing agent for polycarbonate and carbon fiber composite materials. Background Art

[0002] Polycarbonate, commonly referred to as PC, is a polymer containing carbonate groups in its molecular chain. Depending on the ester group, polycarbonates can be generally classified into three categories: aliphatic, aromatic, and aliphatic-aromatic. As an engineering plastic with excellent overall performance, polycarbonate is widely used in industry, agriculture, and daily life.

[0003] Carbon fiber (CF), a high-performance new fiber with a carbon content exceeding 90%, is typically produced from polyacrylonitrile precursor fibers through oxidation and carbonization. It boasts low density, high strength, high-temperature resistance, corrosion resistance, abrasion resistance, and high modulus, along with the flexibility and weavability of fibers. It is currently one of the primary reinforcement materials for advanced composite materials and is widely used in aerospace, sports equipment, and industrial applications. Carbon fiber-reinforced polycarbonate composites combine the high strength and modulus of carbon fiber with the toughness, chemical resistance, thermal stability, and corrosion resistance of polymers, resulting in widespread application.

[0004] Conventional polycarbonate has a high viscosity even at high temperatures, and has a low affinity with carbon fibers, which are inert on the surface. Composite materials composed of a direct mixture of the two have limited strength gains and poor overall performance. Therefore, it is necessary to surface treat and modify the CF to enhance the interaction between the reinforcement phase and the substrate interface, including mechanical intercalation, van der Waals forces, and chemical bonding. The most common method is to treat the carbon fiber with a sizing agent. The sizing agent is evenly coated on the carbon fiber surface, which can change the fiber surface morphology, that is, the surface roughness changes, which helps to strengthen the adhesion and anchoring effect between the fiber and the matrix.

[0005] Although there are many sizing agents on the market, such as modified polyurethane emulsion-based sizing agents used in polycarbonate and carbon fiber composites, they are highly targeted in their application to different resin systems. The effects of the same sizing agent vary in different resin systems. Therefore, designing sizing agents for polycarbonate is a research hotspot for carbon fiber surface modification. Summary of the Invention

[0006] The object of the present invention is to provide a sizing agent for polycarbonate and carbon fiber composite materials, which can make the composite materials have good and stable performance.

[0007] To achieve the purpose of the present invention, the technology of the solution is:

[0008] A sizing agent for polycarbonate and carbon fiber composite materials comprises: a low-density polycarbonate, a dispersant, a stabilizer, an epoxy resin, a wetting agent, and deionized water. Based on 100% total solids, the composition comprises 50-60% low-density polycarbonate, 10-15% dispersant, 10-15% stabilizer, 7-29% epoxy resin, and 1-2% wetting agent. The low-density polycarbonate has a number-average molecular weight of 2000-5000. Preferably, the low-density polycarbonate has a number-average molecular weight of 3000-5000.

[0009] Furthermore, the mass concentration of the sizing agent is 30% to 40%.

[0010] Furthermore, the dispersant is selected from polyacrylamide; the stabilizer is selected from polyvinyl alcohol. The number average molecular weight of polyacrylamide is between 10,000 and 30,000, preferably between 15,000 and 20,000. The number average molecular weight of polyvinyl alcohol is between 5,000 and 18,000, preferably between 7,000 and 12,000.

[0011] Furthermore, the method for preparing the oligocarbonate includes: S1, vacuum drying bisphenol A and diphenyl carbonate separately; S2, stirring bisphenol A and diphenyl carbonate with nitrogen and heating to 150°C to melt the monomers, adding a catalyst, and maintaining the temperature at 150°C for 0.5h, then heating to 170°C, 190°C and 230°C for 0.5h each, and then vacuuming for 15 minutes to remove the by-product phenol, and naturally cooling to obtain a solid product; S3, dissolving the solid product in tetrahydrofuran, precipitating with anhydrous ethanol, and drying to obtain the product.

[0012] Furthermore, the molar ratio of bisphenol A to diphenyl carbonate is 1:1.05 to 1.1. The catalyst is selected from sodium acetate, sodium hydroxide, and cesium carbonate; the molar ratio of the catalyst to bisphenol A is 10 -5 ~10 -3 .

[0013] Furthermore, the wetting agent is selected from polyethylene glycol laurate and polyethylene glycol stearate; the sizing agent also includes 0-0.2% of a preservative; the preservative is selected from benzoic acids and isothiazolinones.

[0014] Correspondingly, the present invention also provides a composite material, wherein the composite material contains carbon fibers, and the carbon fibers are sizing-treated using the aforementioned sizing agent for recycled carbon fibers.

[0015] The sizing agent prepared by the present invention is used for polycarbonate and carbon fiber composite materials, especially for preparing composite materials from recycled carbon fibers. Since oligocarbonate and epoxy resin are used as raw materials at the same time, the relative molecular mass of the oligocarbonate is smaller than that of commercial PC, the relative proportion of hydroxyl groups at the end of the molecular chain is increased, so that the oligocarbonate has certain reactivity, can improve the interface performance of the composite material, and make the composite material have excellent mechanical properties. At the same time, the sizing agent is stable and conducive to storage, and is suitable for industrial production. DETAILED DESCRIPTION

[0016] To make the purpose, technical solutions and advantages of the examples of the present application clearer, the technical solutions in the examples of the present application will be described clearly and completely below. Where specific conditions are not specified in the examples, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially.

[0017] Example 1

[0018] Preparation of oligocarbonates:

[0019] S1. Recrystallize bisphenol A from toluene and dry in vacuum at 60°C; recrystallize diphenyl carbonate from methanol and dry in vacuum at room temperature;

[0020] S2, take 0.4 mol bisphenol A and 0.42 mol diphenyl carbonate into a three-necked flask with a stirrer, a nitrogen tube, and a tail gas conduit (connected to a condenser), stir with nitrogen and heat to 150 ° C until the monomers melt, add 140 μL of NaOH aqueous solution (0.057 g / mL), and keep the reaction at 150 ° C for 0.5 h, then heat to 170 ° C, 190 ° C and 230 ° C for 0.5 h, then evacuate for 15 min to remove the by-product phenol (vacuum degree <133.3 Pa), and obtain a solid product after natural cooling;

[0021] S3. The product was dissolved in 200 ml of tetrahydrofuran, and then precipitated with 3 times the volume of anhydrous ethanol to remove unreacted raw materials or residual phenol, and dried at 60° C. under forced air to obtain oligocarbonate.

[0022] The sizing agent configuration was prepared by the following method:

[0023] S1. Take 75g of the above-mentioned oligocarbonate, 15g of polyacrylamide, and 43.5g of bisphenol A epoxy resin and mix them evenly for later use;

[0024] S2. Add 175 g of deionized water to a stainless steel stirred tank A and start mechanical stirring, maintaining a speed of 150 rpm, and gradually add the above mixture. Continue stirring for 40 minutes after complete addition;

[0025] S3. The aqueous mixture was transferred to a stainless steel stirred tank B, 15 g of polyvinyl alcohol, 1.5 g of polyethylene glycol laurate as a wetting agent, and 175 g of deionized water were added. A high-speed emulsifier was turned on and emulsified at a speed of 5000 rpm for 20 min to obtain a sizing agent.

[0026] Example 2

[0027] The preparation method of oligocarbonate is the same as that in Example 1.

[0028] Sizing agent configuration:

[0029] S1. Take 90g of the above-mentioned oligocarbonate, 22.5g of polyacrylamide, and 13.5g of bisphenol A epoxy resin and mix them evenly for later use;

[0030] S2. Add 175 g of deionized water to the stainless steel stirred tank A and start mechanical stirring at 200 rpm. Gradually add the above mixture and continue stirring for 35 min after complete addition.

[0031] S3. The aqueous mixture was transferred to a stainless steel stirred tank B, 22.5 g of polyvinyl alcohol, 1.5 g of polyethylene glycol laurate as a wetting agent, and 175 g of deionized water were added. A high-speed emulsifier was turned on and emulsified at a speed of 6000 rpm for 15 min to obtain a sizing agent.

[0032] Example 3

[0033] The preparation method of oligocarbonate is the same as that in Example 1.

[0034] Sizing agent configuration:

[0035] S1. Take 82.5g of the above-mentioned oligocarbonate, 18g of polyacrylamide, and 30g of bisphenol A epoxy resin and mix them evenly for later use;

[0036] S2. Add 175 g of deionized water to a stainless steel stirred tank A and start mechanical stirring at 180 rpm. Gradually add the above mixture and continue stirring for 35 min after complete addition.

[0037] S3. The aqueous mixture was transferred to a stainless steel stirred tank B, 18 g of polyvinyl alcohol, 1.5 g of polyethylene glycol laurate as a wetting agent, and 175 g of deionized water were added. A high-speed emulsifier was turned on and emulsified at a speed of 6000 rpm for 15 min to obtain a sizing agent.

[0038] Example 4

[0039] The preparation method of oligocarbonate is the same as that in Example 1.

[0040] Sizing agent configuration:

[0041] S1. Take 110g of the above-mentioned oligocarbonate, 26g of polyacrylamide, and 36.5g of bisphenol A epoxy resin and mix them evenly for later use;

[0042] S2. Add 150 g of deionized water to the stainless steel stirred tank A and start mechanical stirring at 200 rpm. Gradually add the above mixture and continue stirring for 40 min after complete addition.

[0043] S3. The aqueous mixture was transferred to a stainless steel stirred tank B, 26 g of polyvinyl alcohol, 1.5 g of polyethylene glycol laurate as a wetting agent, and 150 g of deionized water were added. A high-speed emulsifier was turned on and emulsified at 6000 rpm for 20 min to obtain a sizing agent.

[0044] Example 5

[0045] The preparation method of oligocarbonate is the same as that in Example 1.

[0046] Sizing agent configuration:

[0047] S1. Take 100g of the above-mentioned oligocarbonate, 20g of polyacrylamide, and 57.5g of bisphenol A epoxy resin and mix them evenly for later use;

[0048] S2. Add 150 g of deionized water to the stainless steel stirred tank A and start mechanical stirring at 200 rpm. Gradually add the above mixture and continue stirring for 40 min after complete addition.

[0049] S3. The aqueous mixture was transferred to a stainless steel stirred tank B, 21 g of polyvinyl alcohol, 1.5 g of polyethylene glycol laurate as a wetting agent, and 150 g of deionized water were added. A high-speed emulsifier was turned on and emulsified at a speed of 6000 rpm for 15 min to obtain a sizing agent.

[0050] Example 6

[0051] The preparation method of oligocarbonate is the same as that in Example 1.

[0052] Sizing agent configuration:

[0053] S1. Take 75g of the above-mentioned oligocarbonate and mix it with 15g of polyacrylamide for later use;

[0054] S2. Add 125 g of deionized water to the stainless steel stirred tank A and start mechanical stirring at 200 rpm. Gradually add the above mixture and continue stirring for 40 min after complete addition.

[0055] S3. The aqueous mixture was transferred to a stainless steel stirred tank B, 15 g of polyvinyl alcohol, 1.5 g of polyethylene glycol laurate as a wetting agent, and 123.5 g of deionized water were added. A high-speed emulsifier was turned on and emulsified at a speed of 6000 rpm for 15 min to obtain a sizing agent.

[0056] Example 7

[0057] Sizing agent configuration:

[0058] S1. Take 75g of commercially available bisphenol A polycarbonate, 15g of polyacrylamide, and 43.5g of bisphenol A epoxy resin and mix them evenly for later use;

[0059] S2. Add 175 g of deionized water to a stainless steel stirred tank A and start mechanical stirring at 200 rpm. Gradually add the above mixture and continue stirring for 45 min after complete addition.

[0060] S3. The aqueous mixture was transferred to a stainless steel stirred tank B, 15 g of polyvinyl alcohol, 1.5 g of polyethylene glycol laurate as a wetting agent, and 175 g of deionized water were added. A high-speed emulsifier was turned on and emulsified at a speed of 6000 rpm for 20 min to obtain a sizing agent.

[0061] Example 8 Sizing agent room temperature static stability test

[0062] The sizing agents of Examples 1 to 7 were allowed to stand at room temperature for a period of time to observe whether the sizing agent emulsions produced stratification, precipitation, demulsification, and the like.

[0063] The above test results are shown in Table 1:

[0064] Table 1

[0065]

[0066] As can be seen from Table 1, the sizing agents prepared in Examples 1-7 have good static stability and are conducive to storage.

[0067] Example 9 Composite material performance test

[0068] Purchased, recycled unsized carbon fibers were soaked in the sizing solutions of Examples 1-7, allowing the sizing agent to fully penetrate. After 20 minutes, the fibers were placed in an 80°C constant-temperature oven and dried for 2 hours. Composite materials were prepared by combining all the sized carbon fibers at a 30 wt% content with a PC matrix: an appropriate amount of commercially available PC was dried in a vacuum oven at 120°C for 4-6 hours. The torque rheometer was set to 250°C and a speed of 10 rpm before the PC was added. The sized carbon fibers were pre-cut into 10 mm lengths and added after the PC melted. The speed was set to 40 rpm and mixed for 5 minutes. The material was then removed and pressed into sheets using a semi-automatic press (mold temperature 260°C, mold pressure 10 MPa). Mechanical properties were tested on 12 mm × 80 mm × 2 mm strips of the same specifications. Five samples were used for each composite, and the values ​​were averaged. The results are shown in Table 2.

[0069] Table 2

[0070]

[0071] As can be seen from Table 2, when the sizing agent made of oligocarbonate and bisphenol A epoxy resin is added at the same time, the mechanical properties of the composite material made of recycled carbon fiber and matrix PC are good. When bisphenol A epoxy resin is missing, the mechanical properties are reduced. When commercial PC (1.5~3×10 4 ), the mechanical properties of the composite material also decline. Because the relative molecular weight of the homemade oligocarbonate is lower than that of commercial PC, the relative proportion of hydroxyl groups on the molecular chain is increased. This, on the one hand, makes the oligocarbonate more reactive, allowing for a more uniform dispersion in the polyacrylamide / polyvinyl alcohol system, and increasing the probability of chemical bonding or hydrogen bonding with oxygen-containing functional groups on the carbon fiber surface. Furthermore, because the oligocarbonate backbone itself is bisphenol A polycarbonate, it has good compatibility with the PC matrix, which can improve the interface properties of the composite material.

[0072] The embodiments described above are part of the embodiments of the present application, rather than all of the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

Claims

1. A sizing agent for polycarbonate and carbon fiber composite materials, characterized in that: The sizing agent includes oligocarbonate, a dispersant, a stabilizer, an epoxy resin, a wetting agent, and deionized water. Based on 100% solid components, the oligocarbonate comprises 50-60% polycarbonate, 10-15% dispersant, 10-15% stabilizer, 7-29% epoxy resin, and 1-2% wetting agent. The number average molecular weight of the oligocarbonate is 2000-5000.

2. The sizing agent for polycarbonate and carbon fiber composite materials according to claim 1, characterized in that: The mass concentration of the sizing agent is 30% to 40%.

3. The sizing agent for polycarbonate and carbon fiber composite materials according to claim 1, characterized in that: The dispersant is selected from polyacrylamide; and the stabilizer is selected from polyvinyl alcohol.

4. The sizing agent for polycarbonate and carbon fiber composite materials according to claim 1, characterized in that: The method for preparing oligocarbonate comprises: S1, vacuum drying bisphenol A and diphenyl carbonate respectively; S2, stirring bisphenol A and diphenyl carbonate through nitrogen and heating to 150°C to melt the monomers, adding a catalyst, maintaining the temperature at 150°C for 0.5h, then heating to 170°C, 190°C and 230°C for 0.5h each, then vacuuming for 15 minutes to remove the by-product phenol, and naturally cooling to obtain a solid product; S3, dissolving the solid product in tetrahydrofuran, precipitating with anhydrous ethanol, and drying to obtain the product.

5. The sizing agent for polycarbonate and carbon fiber composite materials according to claim 4, characterized in that: The molar ratio of bisphenol A to diphenyl carbonate is 1:1.05-1.

1.

6. The sizing agent for polycarbonate and carbon fiber composite materials according to claim 4, characterized in that: The catalyst is selected from sodium acetate, sodium hydroxide, and cesium carbonate; the molar ratio of the catalyst to bisphenol A is 10 -5 ~10 -3 .

7. The sizing agent for polycarbonate and carbon fiber composite materials according to claim 1, characterized in that: The wetting agent is selected from polyethylene glycol laurate and polyethylene glycol stearate; the sizing agent also includes 0-0.2% of a preservative; the preservative is selected from benzoic acid and isothiazolinone.

8. A composite material comprising carbon fibers, characterized in that: The carbon fiber is sizing treated using the sizing agent for recycled carbon fiber according to any one of claims 1 to 7.

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