TWI843665B - Method for enhancing the interface strength between carbon fiber and acrylic resin - Google Patents

Abstract

A method for enhancing the interface strength between carbon fiber and acrylic resin comprises: preparing a carbon fiber containing a surface slurry; performing a silane impregnation operation, passing the carbon fiber containing the surface slurry through an impregnation tank containing silane, performing a heating reaction and a drying process under the condition of controlling the acid-base value and temperature of silane, thereby changing the surface energy of the carbon fiber so that it can be bonded to the surface of the acrylic resin. The silane carbon fiber acrylic composite is formed by heating and reacting with acrylic resin. The composite has good interface strength after the carbon fiber and the acrylic resin are combined. It is used to solve the problem of low interface properties caused by the lack of carbon fiber surface slurry for thermoplastic acrylic resin in the market, so that thermoplastic acrylic resin carbon fiber composites meet industrial applications.

Description

Method for enhancing the interface strength between carbon fiber and acrylic resin

The present invention relates to a "method for enhancing the interface strength between carbon fiber and acrylic resin", which helps to increase the surface energy of carbon fiber, further has a good impregnation effect with acrylic resin, and enhances the interface strength between carbon fiber and acrylic resin.

According to the knowledge, carbon fiber composites are composed of carbon fibers, matrices, and interfaces, and polymer materials are the most widely used matrices. The function of the interface is to transfer the load in the composite material. The carbon fiber and the matrix form a material with comprehensive high performance through the interface. However, the carbon fiber surface becomes chemically inert during the carbonization and sintering process, resulting in poor interface performance with the matrix. Therefore, carbon fiber manufacturers need to further treat the carbon fiber surface to make it have specific functional groups for use with specific polymer matrices.

There are many methods for carbon fiber surface treatment. The research methods that have been carried out can be summarized into: oxidation method, high-energy radiation treatment method, coating method, etc.

The oxidation method is divided into liquid phase oxidation, gas phase oxidation, electrochemical oxidation, etc. according to the different oxidizing media used. The oxidation method actually uses different oxidation technologies to oxidize the surface of carbon fibers, increase the oxygen-containing functional groups on the surface of carbon fibers, produce surface etching, and enhance bonding and intercalation. However, this method often uses strong oxidants, strong acids, ozone, etc., and the operation process is dangerous and produces many waste liquid pollution problems.

High-energy radiation treatment uses microparticles or plasma emitted by high-energy rays to bombard the fiber surface, generating chemical bonding between the fiber surface and the resin substrate, and improving the wettability of the resin substrate to the carbon fiber. The effect achieved by this method is similar to that of the oxidation method. On the one hand, chemically reactive free radicals or grafted active functional groups are generated on the fiber surface, increasing the chemical bonding between the carbon fiber surface and the resin matrix, and improving the wettability of the resin matrix to the carbon fiber. On the other hand, high-energy rays moderately etch the carbon fiber surface to increase the fiber surface roughness and improve the mechanical action between the fiber surface and the substrate. However, this process has high equipment costs, complex control, and high production costs.

The surface coating method is to coat a medium with a certain thickness and certain reactivity on the surface of the carbon fiber. The medium can build a "bridge" between the carbon fiber surface and the resin matrix, improve the compatibility between the polymer and the reinforcing fiber, reduce the interfacial tension, and have a beneficial effect on the interface of the composite material from the perspective of physical methods. In addition to the coupling agent method, electropolymerization method and sizing agent treatment, the surface coating method also includes chemical vapor deposition method, magnetron sputtering, etc.

It is known that the surface slurry treatment of carbon fiber is for use in thermosetting epoxy resin. If it is to be used in thermoplastic resins such as acrylic resin, the original carbon fiber slurry must be removed with a solvent and then treated with a thermoplastic resin slurry, as shown in the literature "Effect of sizing agent on interfacial properties of carbon fiber-reinforced PMMA composite" LiJian published online February 2, 2021. https://doi.org/10.1177/2633366X20978657 . This causes problems and troubles in the use of carbon fiber in thermoplastic acrylic resin.

In view of this, the inventor has been engaged in the manufacturing, development and design of related products for many years. After careful design and careful evaluation for the above-mentioned goals, he finally obtained this invention which is truly practical.

The technical problem that this invention aims to solve is that currently carbon fibers are generally surface treated and contain a certain amount of sizing agent on the surface, mainly for use in thermosetting epoxy resins. Therefore, it is difficult to find carbon fibers containing sizing agents for use in thermoplastic polymers, especially carbon fibers specifically for use in acrylic resins, which hinders the development of thermoplastic carbon fiber composites with environmentally friendly recycling characteristics. Carbon fibers provided for use in epoxy resins have low interfacial strength when used in acrylic resin systems, and cannot exert the overall performance of acrylic carbon fiber composites.

In view of the above-mentioned deficiencies in the prior art, the present invention provides a method for enhancing the interfacial strength between carbon fiber and acrylic resin, comprising: preparing a carbon fiber containing a surface slurry; performing a silane impregnation operation, passing the carbon fiber containing the surface slurry through an impregnation tank containing silane, and performing drying and heating reaction treatment under the condition of controlling the acid-base value and temperature of silane, thereby changing the The carbon fiber surface energy; acrylic resin polymerization reaction, the aforementioned carbon fiber containing silane is passed through an acrylic resin impregnation tank mixed with a molten slurry containing monomers, oligomers, initiators, etc. containing acrylic functional groups, and then pressed and heated for reaction polymerization to form a silane carbon fiber acrylic composite. This composite has good interface strength after the carbon fiber and the acrylic resin are combined.

Preferably, the impregnation tank contains an organic solvent, and silane is dispersed in the organic solvent at a ratio of 0.5% to 3%, and the pH value of the impregnation tank is controlled between pH 2 and 3.

Preferably, the pH value is controlled at pH 2-3 using inorganic acid and organic acid, wherein the organic acid is any one of acrylic acid and methacrylic acid containing acrylic functional groups.

The organic solvent is any organic solvent such as ether, dichloromethane, benzene, tetrachloromethane, chloroform, etc.

Preferably, the silane is any one of amino silane, epoxy silane and acyloxy silane or a mixture thereof.

Preferably, the drying and heating reaction treatment includes a low-temperature heating and a high-temperature heating. The low-temperature heating is to remove the solvent through a low-temperature oven, the heating temperature is set below 70°C, and the exhaust explosion-proof and heating removal of the solvent are performed. The high-temperature heating is to heat through a high-temperature oven such as a vacuum oven and a continuous oven. The carbon fiber is placed in a dry high-temperature oven for heating reaction treatment. The heating temperature is set between 100°C and 150°C, and the heat treatment is performed for 15 to 30 minutes in a vacuum environment, so that the silane can fully react with the surface of the carbon fiber, increase the surface energy of the carbon fiber, and form a silane carbon fiber.

The low-temperature heating and high-temperature heating are processed in any manner such as staged or continuous.

Preferably, a cooling operation is further included, wherein the carbon fiber after the heating reaction is naturally cooled in a vacuum environment, and then packaged in a PE bag and placed in a -22°C equipment environment for cooling, so as to prevent the carbon fiber surface from absorbing water and further reacting.

Preferably, the acrylic resin is a slurry composed of 3-45% by weight of polymethyl methacrylate (PMMA) dissolved in methyl methacrylate (MMA) monomer, and then 0.5-3% of acrylic reaction initiator, anti-ultraviolet additive and filler are added.

Compared with the effects of previous technologies: 1. Improve the surface energy of carbon fiber: The surface energy of carbon fiber 10 treated by this method is significantly improved. The surface energy of the original carbon fiber is less than the surface energy of acrylic resin 29.4mN/m. After treatment, the surface energy of the carbon fiber is greater than 40mN/m, which means that it can have a good impregnation effect with acrylic resin 40.

2. Enhanced interface strength: The carbon fiber 10 treated by the reaction method and the acrylic resin 40 are made into a silane carbon fiber acrylic composite 41, and its interlaminar shear strength (ILSS) is higher than that of the untreated one, and even reaches the current application level of thermosetting epoxy resin carbon fiber composites.

3. Simple process, effectively reducing costs: This method does not require the use of expensive equipment, strong acids, strong oxidants and other harmful chemicals, which helps to achieve environmental protection effects. It is further used to solve the problem of low interface properties caused by the lack of carbon fiber surface slurry for thermoplastic acrylic resin on the market, so that thermoplastic acrylic resin carbon fiber composites meet industrial applications.

10: Carbon fiber

11: Silane carbon fiber

20: Immersion tank

30: Drying and heating reaction treatment

31: Low temperature oven

32: High temperature oven

40:Acrylic resin

41: Silane carbon fiber acrylic composite

[Figure 1] is a schematic diagram of the carbon fiber of the present invention undergoing silane reaction.

[Figure 2] is a schematic diagram of the silane carbon fiber combined with acrylic resin of the present invention.

In order to enable the Honorable Review Committee to have a further understanding and recognition of the purpose, features and efficacy of the present invention, the following is a detailed description in conjunction with the [Simple Explanation of Figures]: First, please refer to Figures 1 and 2, a method for enhancing the interfacial strength between carbon fiber and acrylic resin, including: preparing a carbon fiber 10, which is a carbon fiber 10 containing a surface slurry; a silane impregnation operation, wherein the carbon fiber 10 containing the surface slurry passes through an impregnation tank 20 containing silane, wherein the impregnation tank 20 contains an organic solvent, and then silane is dispersed in the organic solvent at a ratio of 0.5% to 3%, and the impregnation tank 20 is impregnated with silane. The pH value of the carbon fiber 10 is controlled between pH 2 and 3. After passing through the impregnation tank 20, the carbon fiber 10 is then dried and heated for reaction 30 to change the surface energy of the carbon fiber 10. The acrylic resin polymerization reaction is to make the carbon fiber 10 containing silane pass through the impregnation tank of the acrylic resin 40 mixed with the molten slurry containing the monomer, oligomer, initiator, etc. containing the acrylic functional group to make a unidirectional prepreg. After lamination, it is then pressed and heated for reaction polymerization to form a silane carbon fiber acrylic composite 41. This composite has good interface strength after the carbon fiber and the acrylic resin are combined.

The organic solvent is any organic solvent such as ether, dichloromethane, benzene, tetrachloromethane, chloroform, etc., and dichloromethane is the best.

The pH value is controlled at pH 2~3 using inorganic acids and organic acids, such as organic acids containing acrylic functional groups and any acid such as methacrylic acid. Among them, organic acids containing acrylic functional groups are preferred, and methacrylic acid is the best.

The silane is any one of the above silanes such as amino silane, epoxy silane and methacryloxy silane or a mixture thereof;

The silane is amino silane, as shown below:

The silane is epoxy silane, as shown below:

The silane is methacrylic acyloxy silane (Acyloxy Silanes), as shown below:

The following is only an example to illustrate the possible implementation of the present invention, but it is not intended to limit the scope of the present invention to be protected. It is necessary to explain it first; please refer to FIG. 1 at the same time. In this embodiment, the carbon fiber 10 containing the surfactant passes through the impregnation tank 20 and then undergoes a heating reaction. The impregnation tank 20 contains a dichloromethane organic solvent, and silane is dispersed in the organic solvent at a ratio of 1%. The impregnation tank 20 is controlled to have an acid-base value between pH 2 and 3 with acrylic acid. The drying and heating reaction treatment 30 includes a low-temperature heating and a high-temperature heating. The low-temperature heating is performed by a low-temperature drying. The solvent is removed by the box 31, and the heating temperature is set at 50°C and explosion-proof exhaust and heating are performed to remove the solvent. After low-temperature heating, the carbon fiber 10 is rolled up. The high-temperature heating is performed by heating through a high-temperature oven 32 such as a vacuum oven or a continuous oven. The carbon fiber 10 is placed in the high-temperature oven 32 for heating reaction treatment. The heating temperature is set between 100°C and 150°C, and the heat treatment is performed for 15 to 30 minutes in a vacuum environment, so that the silane can fully react with the surface of the carbon fiber 10, thereby changing the surface energy of the carbon fiber 10 to form a silane carbon fiber 11.

After the above heating reaction, a cooling operation can be performed. The carbon fiber 10 after the heating reaction is naturally cooled in a vacuum environment, and then packed in a PE bag and placed in a -22°C equipment environment for cooling to prevent the surface of the carbon fiber 10 from absorbing water and further reacting.

The following carbon fiber, carbon fiber with surface sizing removed, silane carbon fiber 11 impregnated with silane, and acrylic resin were measured for surface energy (including polar force and dispersion force) using a Kruss 12 tension meter. The comparison example used carbon fiber with surface sizing removed. The treatment process was to rewind about 300g of carbon fiber on a glass tube and place it in an appropriate ultrasonic oscillator. THF was poured into the ultrasonic oscillator to cover the carbon fiber, soak it for more than 72 hours, and ultrasonically oscillate it at any time. After the carbon fiber was taken out, it was placed in another ultrasonic oscillator and washed with clean deionized water. The water was changed after ultrasonic oscillation for 30 minutes, and it was treated five times in total. Then evacuate the mixture in a vacuum oven at 100°C overnight. Take it out and pack it in a PE bag and place it in a freezer.

The surface energy test results are shown in the table below;

From the above surface energy test results, it can be seen that the surface energy of the carbon fiber before the reaction is less than the surface energy of the acrylic resin 29.4mN/m. The silane carbon fiber 11 after the reaction treatment of the present invention can produce a better surface energy effect of 49.0024mN/m. Accordingly, after the carbon fiber 10 is impregnated, dried and heated, the surface energy (surface energy) and σ _s ^d (disperse part) values of the carbon fiber 10 are significantly increased, which means that the surface energy of the carbon fiber after impregnation and heating reaction is significantly improved.

Then, the effect on the composite is verified. The carbon fiber, the carbon fiber without the slurry, and the silane carbon fiber 11 treated with silane are impregnated with an acrylic resin 40 and heat-formed to form an acrylic composite. The interlaminar shear strength ILSS (Interlaminar shear strength) value is tested with a universal testing machine. The acrylic resin is polymethyl methacrylate (PMMA) dissolved in methyl methacrylate (MMA) monomer at a weight percentage of 3-45%, and then 0.5-3% of an acrylic reaction initiator, an anti-ultraviolet additive, and a filler are added to form a slurry, and acrylic acid is used to adjust the acrylic resin to an acidic state. The acrylic resin 40 impregnated carbon fiber is made into prepreg material by using a drum type prepreg molding machine, and the carbon fiber, the carbon fiber without slurry, and the silane carbon fiber 11 are impregnated into the acrylic resin 40. Then, the prepreg material is stacked into 19cm×12cm×36 layers in a 50Ton hydraulic press at 75℃×15min+100℃×15min and a pressure of 70kg/ ^cm2 to form a flat specimen. The specimen is cooled to below 50℃ in the mold, and then the flat specimen is cut into specimens according to ASTM D2344 by a diamond slicer after being taken out and then ILSS is measured. In the comparison example of epoxy resin carbon fiber composite, the carbon fiber and epoxy resin are made into prepreg material by the same drum type prepreg molding machine. The above-mentioned prepreg material is stacked into 19cm×12cm×36 layers in a 50Ton hydraulic press, hardened at 120℃×60min, and formed into a flat specimen under a pressure of 70kg/ ^cm2. It is cooled in the mold to below 50℃, taken out and then hardened at 120℃ for two hours to ensure complete hardening. The flat specimen is then cut into specimens according to ASTM D2344 using a diamond slicer and tested for ILSS.

The test values are shown in the following table:

From the above test results, it can be seen that the ILSS value of the silane carbon fiber acrylic composite 41 formed by the carbon fiber 10 after silane reaction treatment is significantly improved, reaching the current application level of thermosetting epoxy resin carbon fiber composites.

From the above description, it can be seen that the present invention and its preparation method can achieve the following advantages: Improve the surface energy of carbon fiber: The surface energy of carbon fiber 10 treated by this method is significantly improved. The surface energy of the original carbon fiber 10 is less than the surface energy of acrylic resin 40, which is 29.4mN/m. After treatment, the surface energy of carbon fiber 10 is greater than 40mN/m, which means that the impregnation with acrylic resin is very good.

The following benefits can be obtained by using the structure of the above specific implementation example:

1. Improve the surface energy of carbon fiber: The surface energy of carbon fiber 10 treated by this method is significantly improved. The surface energy of the original carbon fiber is less than the surface energy of acrylic resin 29.4mN/m. After treatment, the surface energy of the carbon fiber is greater than 40mN/m, which means that it can have a good impregnation effect with acrylic resin 40.

2. Enhanced interface strength: The carbon fiber 10 treated by the reaction method and the acrylic resin 40 are made into a silane carbon fiber acrylic composite 41, and its interlaminar shear strength (ILSS) is higher than that of the untreated one, and even reaches the current application level of thermosetting epoxy resin carbon fiber composites.

3. Simple process, effectively reducing costs: This method does not require the use of expensive equipment, strong acids, strong oxidants and other harmful chemicals, which helps to achieve environmental protection effects. It is further used to solve the problem of low interface properties caused by the lack of carbon fiber surface slurry for thermoplastic acrylic resin on the market, so that thermoplastic acrylic resin carbon fiber composites meet industrial applications.

In summary, this invention has indeed achieved a breakthrough structural design and has improved invention content. At the same time, it can achieve industrial applicability and progress. Moreover, this invention has not been seen in any publication and is also novel. It should comply with the relevant provisions of the Patent Law. Therefore, we have filed an invention patent application in accordance with the law and pleaded with the review committee of the Jun Bureau to grant legal patent rights. We are very grateful.

However, the above is only a preferred embodiment of the present invention and should not be used to limit the scope of implementation of the present invention; that is, all equivalent changes and modifications made according to the scope of the patent application of the present invention should still fall within the scope of the patent of the present invention.

10: Carbon fiber

11: Silane carbon fiber

20: Immersion tank

30: Drying and heating reaction treatment

31: Low temperature oven

32: High temperature oven

Claims (7)

A method for enhancing the interface strength between carbon fiber and acrylic resin comprises: preparing a carbon fiber containing a surface slurry; performing a silane impregnation operation, passing the carbon fiber containing the surface slurry through an impregnation tank containing silane, and performing drying and heating reaction treatment under the condition of controlling the acid-base value and temperature of silane, thereby changing the surface energy of the carbon fiber; performing a cooling operation, cooling the carbon fiber after the heating reaction The silane-containing carbon fiber is naturally cooled in a vacuum environment; the acrylic resin polymerizes, and the carbon fiber containing silane is passed through an impregnation tank of an acrylic resin mixed with a molten slurry containing monomers, oligomers, initiators, etc. containing acrylic functional groups, and then pressed and heated for reaction polymerization to form a silane carbon fiber acrylic composite. This composite has good interface strength after the carbon fiber and the acrylic resin are combined. A method for enhancing the interface strength between carbon fiber and acrylic resin as described in claim 1, wherein the impregnation tank contains an organic solvent, silane is dispersed in the organic solvent at a ratio of 0.5% to 3%, and the pH value of the impregnation tank is controlled between pH 2 and 3. A method for enhancing the interfacial strength between carbon fiber and acrylic resin as described in claim 2, wherein the organic solvent is any organic solvent such as ether, dichloromethane, benzene, tetrachloromethane, chloroform, etc. A method for enhancing the interface strength between carbon fiber and acrylic resin as described in claim 1, wherein the silane is any silane such as amino silane, epoxy silane, and methacryloyloxy silane, or a mixture thereof. The method for enhancing the interface strength between carbon fiber and acrylic resin as described in claim 1, wherein the drying and heating reaction treatment includes a low-temperature heating and a high-temperature heating. The low-temperature heating is to remove the solvent through a low-temperature oven, the heating temperature is set below 70°C, and the exhaust explosion-proof and heating removal of the solvent are performed. The high-temperature heating is to heat through a high-temperature oven such as a vacuum oven and a continuous oven. The carbon fiber is placed in the high-temperature oven for heating reaction treatment, the heating temperature is set between 100°C and 150°C, and the heat treatment is performed for 15 to 30 minutes in a vacuum environment, so that the silane can fully react with the carbon fiber surface, increase the surface energy of the carbon fiber, and form a silane carbon fiber. A method for enhancing the interface strength between carbon fiber and acrylic resin as described in claim 5, wherein the low-temperature heating and high-temperature heating are performed in either a stepwise or continuous manner. A method for enhancing the interface strength between carbon fiber and acrylic resin as described in claim 1, wherein the acrylic resin is a slurry composed of 3-45% by weight of polymethyl methacrylate (PMMA) dissolved in methyl methacrylate (MMA) monomer, and then 0.5-3% of an acrylic reaction initiator, an anti-ultraviolet additive and a filler are added.

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