KR20170026741A - Method of Manufacturing of Composite Material for Carbon Fiber-reinforced Thermoplastic Plastic - Google Patents

Abstract

The present invention relates to a method for manufacturing a composite material for a carbon fiber-reinforced thermoplastic resin. The manufacturing method suggests a new method for improving mechanical properties of the composite material. In the new composite manufacturing process, in order to bond polypropylene (PP) as a basic material, linear low density polyethylene (LLDPE), and a nitric acid-treated high strength carbon fiber surface functionalizer, a silane-based binder is added. The process is a very useful technique, capable of improving the mechanical properties, such as excellent strength, particularly excellent tensile strength, and flexural strength.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a carbon fiber-reinforced thermoplastic composite material,

The present invention relates to a method for producing a composite material for a carbon fiber-reinforced thermoplastics in which the carbon fiber and the polypropylene composite material are improved by surface treatment of the carbon fiber and the mechanical properties are improved by mixing the linear low density polyethylene with the polypropylene .

Carbon fiber is a high-tech material with high strength, high elasticity, high thermal properties and high conductivity, which is widely used in industries such as military supplies, aviation, building materials and ships. Particularly, in the automobile industry, not only have excellent mechanical properties such as tensile strength, fracture toughness and impact strength, but also demands and necessity for lightening of materials are increasing. Carbon fiber reinforcement polymer (CFRP) is one of the solutions to this requirement. The first generation of CFRP used thermosetting resins such as epoxy, vinyl ester, polyester and phenolic resin as the base material and converted to carbon fiber-reinforced thermoplastics ( Carbon fiber reinforcement thermoplastic (CFRT). It is well known that thermoplastic resins are more environmentally friendly than thermosetting resins because they can be recycled while being heated and re-molded with new components. It is also known that thermoplastic resins have no cross-linking unlike thermosetting resins. When a thermoplastic resin is used as a base material of a composite material, the composite material having high toughness can be produced and the production cost can be lowered.

Among the thermoplastic resins, polypropylene is one of the promising materials because of its excellent processability, low unit cost and high performance. Polypropylene is already widely used not only in the automobile industry but also in various industrial fields. For the automotive industry, excellent tensile properties, impact strength and fracture toughness are required.

Korean Patent Publication No. 1995-0018178

It is an object of the present invention to provide a method for producing a composite material for a carbon fiber-reinforced thermoplastic resin which can improve mechanical properties such as excellent strength, particularly excellent tensile strength and flexural strength.

In order to accomplish the above object, the present invention provides a method for producing a carbon nanotube, comprising: (a) a step of nitric acid treatment by immersing carbon fibers in a nitric acid solution; Preparing a binder solution by dissolving 3-methylacryloxypropyl trimethoxysilane as a silane coupling agent in distilled water (second step); Immersing the nitric acid-treated carbon fibers in the binder solution to prepare a carbon fiber treated with the binder (third step); And mixing the carbon fiber treated with the binder with a base material (fourth step); A method of producing a composite material for a carbon fiber-reinforced thermoplastic polymer is provided.

The method for producing a composite material for a carbon fiber-reinforced thermoplastics according to the present invention has excellent physical properties such as tensile strength and flexural strength as compared with a conventional composite material due to nitric acid treatment and addition of a binder to the surface of the carbon fiber have.

1 is a graph showing the tensile strength of a composite material for a carbon fiber-reinforced thermoplastic resin.
2 is a graph showing flexural strength and flexural modulus of a composite material for a carbon fiber-reinforced thermoplastic resin.
3 is a graph showing the impact strength of the composite material for a carbon fiber-reinforced thermoplastic resin.

Hereinafter, the present invention will be described in more detail.

The inventors of the present invention have conducted research and development on a method for producing a composite material for a carbon fiber-reinforced thermoplastic resin by adding a silane-based bonding agent for bonding nitriding to the surface of the carbon fiber and functionalizing the surface of the carbon fiber The present inventors have developed a method for producing a composite material for a carbon fiber-reinforced thermoplastics in which mechanical and physical properties such as tensile strength and flexural strength are improved.

The present invention relates to a process for nitric acid treatment by immersing carbon fibers in a nitric acid solution (first step); Preparing a binder solution by dissolving 3-methylacryloxypropyl trimethoxysilane as a silane coupling agent in distilled water (second step); Immersing the nitric acid-treated carbon fibers in the binder solution to prepare a carbon fiber treated with the binder (third step); And mixing the carbon fiber treated with the binder with a base material (fourth step); The present invention provides a method for producing a composite material for a carbon fiber-reinforced thermoplastic polymer.

The nitric acid treatment can immerse the carbon fiber in a 64 to 66 wt% nitric acid solution at 100 to 115 캜 for 2 to 3 hours. If the amount of the nitric acid solution is less than 64 wt%, the surface of the carbon fiber may not be sufficiently treated and the functionalizer may not be sufficiently formed. If the nitric acid solution is more than 66 wt% It is more preferable that the nitric acid treatment is performed in a 64 to 66 wt% nitric acid solution.

The nitric acid solution used in the nitric acid treatment may be a nitric acid solution having a concentration of about 65%. The corresponding concentration has a molar concentration value of about 16M, and when a nitric acid solution of about 16M is used, the surface of the carbon fiber can be activated to suitably react.

In order to treat the surface of the carbon fiber with nitric acid, the carbon fiber is precipitated in an acetone solution of a polar aprotic solution for 10 to 12 hours to remove impurities. Thereafter, desizing is performed to remove the epoxy present on the surface of the carbon fiber Is effectively removed.

After the drying process, the carbon fiber is dried at 90 to 110 ° C. After the drying process, the carbon fiber is precipitated in a nitric acid solution having a concentration of about 65% at 100 to 115 ° C for 2 to 3 hours and then washed with distilled water , And the carbon fibers can be dried at 80-100 ° C in a vacuum furnace to evaporate the remaining moisture.

The nitric acid treatment is the best method for surface treatment because it can increase the surface roughness of the carbon fiber at the same time and is effective in inducing an acid functional group on the surface of the carbon fiber.

The silane-based coupling agent has the largest molecular volume, high surface energy, and high non-polarity value. However, since the silane-based coupling agent has high molecular weight and high non-polarity value, When the non-polarity value of the carbon fiber is increased by adding the silane-based binder to the base material, which is a part of the material, since the base material has a large non-polarity value, the base material and the surface of the carbon fiber can show high mechanical strength, When a chemical functional group such as a carboxyl group or a carboxyl group is included in the surface of the carbon fiber, it can have a high polarity due to the methoxy group, and therefore, it is more preferable to use an example phosphorous bonding agent.

The silane coupling agent has various silane coupling agents depending on the type of the organic functional group, but the chemical structure of a typical silane coupling agent is represented by the following formula (1).

[Chemical Formula 1]

R'-Si- (OR) ₃

In the above formula (1), R is a (C1 to C4) alkyl group, and R 'is an alkyl group having 1 to 4 carbon atoms such as an amino group, a methacryloxy (C1 to C4) alkyl group, a styryl group, an epoxy group, a vinyl group, a ureido group, sulfide group and mercapto group. More specifically, the silane-based bonding agent is excellent in compatibility with polypropylene and polyethylene, and can improve adhesion of an organic resin to an inorganic surface. 3-methylacryloxypropyl (meth) acrylate, which is capable of improving tensile strength and bending strength when forming a composite of a carbon fiber and a base material and capable of reacting not only with inorganic minerals but also with an organic thermosetting resin trimethoxysilane).

More specifically, referring to FIG. 1 and FIG. 2, it can be seen that when 3-methacryloxypropyltrimethoxysilane is used, the bonding force between the base material and the carbon fiber increases, When 3-methacryloxypropyltrimethoxysilane is used as the phosphorus-containing binder, tensile strength, flexural strength and flexural modulus increase.

The silane-based binder solution is dissolved in an amount of 1 to 2% by weight based on 100% by weight of distilled water.

Since the hydrolysis reaction takes place through dissolution with the distilled water and the silane functionalizing agent is present in the solution, it is necessary to adjust the pH of the solution to about 3.5 to 4.5 in order to stabilize it. To adjust the pH, an organic acid such as acetic acid , And the organic acid is not necessarily limited to acetic acid.

After the addition of acetic acid, the mixture is stirred for 30 to 60 minutes using a magnetic stirrer.

The nitric acid-treated carbon fibers may be immersed in a binder solution for 45 to 60 minutes and then dried in a vacuum furnace at a temperature of 80 to 100 ° C. If the carbon fiber is heated to less than 80 ° C, If the temperature exceeds 100 ° C, the functioning group of the surface of the carbon fiber may be lost. Therefore, it is more preferable to dry the carbon fiber at a temperature of 80 to 100 ° C in a vacuum furnace.

When the polypropylene alone is used, the free base material has a low free surface energy and is inactive. Therefore, there is a limitation in using polypropylene as a base material. When considering the shape and impact characteristics, a base material mixed with polypropylene and polyethylene is used .

More specifically, in the case of a base material obtained by mixing polypropylene and linear low density polyethylene among the types of polypropylene and polyethylene, the important factors in the mixing process are miscibility and morphology between the two resins, When mixed with linear low density polyethylene, it has excellent compatibility and low crystallization rate. Therefore, it is difficult to mix low-density polyethylene with linear low-density polyethylene because the crystallization rate is not reduced compared with other types of polyethylene other than linear low density polyethylene. The use of the mixed base material is more preferable.

The base material may be composed of 60 to 80% by weight of polypropylene and 20 to 40% by weight of linear low density polyethylene. If it is out of the above range, the toughness of the composite material is insufficient or mechanical properties such as tensile strength or flexural strength are decreased In particular, when 80% by weight of polypropylene and 20% by weight of linear low density polyethylene are mixed, it is easy to make contact with linear low density polyethylene due to the large surface area of polypropylene, so that it has a spherical base shape It is more preferable to use a base material in which 80% by weight of polypropylene and 20% by weight of linear low density polyethylene are mixed with respect to 100% by weight of the base material .

 The base material having the weight ratio described above and the surface-treated carbon fibers are mixed using a stirring mixer.

The mixing is carried out by mixing 5 to 15% by weight of the carbon fibers treated with the binder and 85 to 95% by weight of the base material at 160 to 180 DEG C for 90 to 120 minutes at a rotation speed of 110 to 130 m / s, There is a problem that the injection moldability is not good or the carbon fiber surface characteristics are decreased. Therefore, it is more preferable to perform the reaction in the mixing condition.

After the mixing process, the mixture is pulverized into granules for injection molding, and the temperature of the extruder may be set to 160 to 180 ° C for injection molding.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the present invention is not limited by these examples.

(Example)

1. Preparation of carbon fiber and base metal

The carbon fiber had a tensile strength of 4900 MPa, an elastic modulus of 230 GPa, a density of 1.80 g / cm < ³ >, and carbon fibers having a length of 2 to 5 mm were prepared.

Further, to prepare a base material for polyester's Korea propylene polymer (density 0.89 g / cm ³⁾ and linear low density polyethylene (density 0.92 g / cm ^3).

 The fractions of polypropylene, linear low density polyethylene and carbon fiber for producing the composite material for the carbon fiber-reinforced thermoplastics were 60% wt, 30% wt and 10% wt, respectively.

2. Type and amount of silane-based binder used

3-Methacryloxypropyl trimethoxysilane (MEMO, Korea Bio-Gen ) was used as a silane-based binder, and 1 to 2 parts by weight of a binder was used based on 100 parts by weight of the composite material.

3. Surface treatment of carbon fiber

The prepared carbon fibers were precipitated in an acetone solution for 12 hours, washed with distilled water obtained from a Pure Power manufactured by Romax Company, and dried at 100 ° C.

After the drying process, it was precipitated in a 65% nitric acid solution at 110 ° C for 2 hours, and after the precipitation, it was washed with distilled water.

After the cleaning process, the carbon fibers were dried at 80 to 100 DEG C in a vacuum furnace to evaporate the remaining moisture.

4. Preparation of binder solution

The 3-methacryloxypropyltrimethoxysilane solution was dissolved in distilled water in an amount of 1 to 2% by weight. On the other hand, the pH of the solution was adjusted to 3.5 to 4.5 to stabilize the hydrolysis reaction and the silane functional group in the solution, and acetic acid was added to adjust the pH. The 3-methacryloxypropyltrimethoxysilane solution and distilled water were stirred for 30 to 60 minutes using a magnetic stirrer until a clear homogeneous solution was formed, and 3-methacryloxy The propyl trimethoxysilane was carefully added. The surface treated carbon fibers were precipitated in a solution containing 3-methacryloxypropyltrimethoxysilane for 45 to 60 minutes and dried in a vacuum furnace at a temperature of about 80 ° C.

5. Carbon fiber and Mixing process of base metal

The mixing conditions were mixed at a rotational speed of 120 m / s for 90 minutes at about 180 ° C. and the injection molding process was carried out at a temperature of 140 to 180 ° C. to determine the effect of the nitric acid treatment, the binder, and the addition of the linear low density polyethylene. Respectively.

6. Grinding process in granular form

After the mixing process, the mixture was pulverized into granules for injection molding, and the temperature of the extruder was set at about 170 ° C for injection molding.

(Comparative Example 1)

The conditions were the same as those of the above example, except that only the polypropylene was used as the base material and the nitric acid treatment and 3-methacryloxypropyltrimethoxysilane were not added to the carbon fibers.

(Comparative Example 2)

The conditions were the same as those of the above example, except that only the polypropylene was used as the base material and 3-methacryloxypropyltrimethoxysilane was not added.

(Comparative Example 3)

The conditions were the same as those of the above example except that only the polypropylene was used as the base material.

(Comparative Example 4)

The conditions were the same as those of the above example, except that nitric acid treatment and 3-methacryloxypropyltrimethoxysilane were not added to the carbon fibers.

(Comparative Example 5)

The conditions were the same as those of the above example, except that the 3-methacryloxypropyltrimethoxysilane was not added to the carbon fibers.

(Experimental Example)

1. Experimental Method

(1) Tensile strength test method

Experiment according to American Society for Testing and Materials (ASTM) D638-08

Specimen shape: dog-bone

Test equipment: SHIMADZU's universal testing machine

Load: 500 kN

Crosshead speed (test speed): 5 mm / min

(2) Flexural strength test method

3 point bending test

Specimen configuration: Bar shape (64.5 x 11.5 x 5.7 mm)

Test equipment: SHIMADZU's universal testing machine

Load: 300 kN

Test speed: 3 mm / min

Span length between lower supports: 42.5 mm

(3) Impact strength test method

Charpy impact test

Specimen configuration: Bar shape (64.5 x 11.5 x 5.7 mm)

Test equipment: SSAUL BESTECH's impact tester (BESTIPT-334CI)

2. Comparison of properties against tensile strength

Referring to FIG. 1, in measuring the tensile strengths of the composite materials produced according to Examples and Comparative Examples 1 to 5, the composite materials prepared according to the Examples were compared with the composite materials prepared according to Comparative Examples 1 to 3 The tensile strengths were decreased by 44.7%, 49.8% and 53.7%, respectively, and the tensile strengths were increased by 24.0% and 4.3%, respectively, as compared with the composite materials prepared according to Comparative Example 4 and Comparative Example 5.

3. Comparison of properties of flexural strength and flexural modulus

Referring to FIG. 2, in measuring the flexural strength and flexural modulus of the composite material produced according to Examples, Comparative Examples 4 and 5, the composite material produced according to Examples was prepared according to Comparative Example 4 and Comparative Example 5 The flexural strength and flexural modulus of composites increased by 20.4% and 32.3%, respectively.

4. Comparison of properties against impact strength

The reaction conditions were observed when batch polypropylene / linear low density polyethylene blends at 175 ° C for 30 seconds were used to effect crystal batches and batch foaming processes affecting the impact strength.

Referring to FIG. 3, in the measurement of the impact strength of the composite material produced according to Examples and Comparative Examples 1 to 5, the composite material produced according to the Example had a higher impact strength than the composite material prepared according to Comparative Examples 1 to 5 Increased by 127.3%, 50.9%, 43.3%, 96.6% and 10.9%, respectively.

While the present invention has been particularly shown and described with reference to specific embodiments thereof, those skilled in the art will appreciate that such specific embodiments are merely preferred embodiments and that the scope of the present invention is not limited thereby. something to do. It is therefore intended that the scope of the invention be defined by the claims appended hereto and their equivalents.

Claims (5)

Immersing the carbon fibers in a nitric acid solution and nitric acid treatment (first step);
Preparing a binder solution by dissolving 3-methylacryloxypropyl trimethoxysilane as a silane coupling agent in distilled water (second step);
Immersing the nitric acid-treated carbon fibers in the binder solution to prepare a carbon fiber treated with the binder (third step); And
Mixing the carbon fibers treated with the bonding agent with the base material (step 4);
Wherein the carbon fiber-reinforced thermoplastics composite material is a carbon fiber-reinforced thermoplastic resin. [2] The method of claim 1, wherein the nitric acid treatment is performed by immersing the carbon fibers in a nitric acid solution having a concentration of 64 to 66% by weight at 100 to 115 캜 for 2 to 3 hours. The carbon fiber-reinforced thermoplastics composite material according to claim 1, wherein the nitrided carbon fiber is immersed in a binder solution for 45 to 60 minutes and dried in a vacuum furnace at a temperature of 80 to 100 ° C. Way. The method of claim 1, wherein the base material comprises 60 to 80% by weight of polypropylene and 20 to 40% by weight of linear low density polyethylene. The method of claim 1, wherein the mixing is performed by mixing 5-15 wt% of the carbon fiber treated with the binder and 85-95 wt% of the base material at a rotation speed of 110-130 m / s for 90-120 minutes at 160-180 캜 Wherein the carbon fiber-reinforced thermoplastic composite material is a carbon fiber-reinforced thermoplastic composite material.

Images