JPH0383840A - Carbon fiber-reinforced material and carbon fiber-reinforced inorganic cured material - Google Patents

Abstract

PURPOSE:To provide the subject carbon fiber-reinforced material having a low corrosion action on iron (alloy) in contact therewith by adding a metal powder having a prescribed average diameter and showing a lower surface potential than that of carbon to an epoxy resin and covering the surface of a carbon fiber with the above-mentioned resin. CONSTITUTION:To an epoxy resin (e.g. bisphenol A type epoxy resin), a metal powder (e.g. iron powder or zinc powder) having 10nm-500mum average diameter and showing a lower surface potential than that of carbon is added and required additives such as a curing agent, a surfactant and an antioxidant are further added thereto. The surface of a carbon fiber is then covered with the resultant epoxy resin to produce the objective carbon fiber-reinforced material. By blending the obtained carbon fiber-reinforced material in mortar, concrete, etc., a hardened material excellent in strength characteristics, deformation properties, elastic properties, etc., and suitable for a building material, etc., can be produced and the produced hardened material shows a low corrosion action on iron (alloy) in contact therewith.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention is mainly used in the field of civil engineering and construction, such as floors, walls,
The present invention relates to a carbon fiber reinforcing material excellent in preventing galvanic corrosion of iron and iron alloys used for roofs, etc., and a carbon fiber reinforced hydraulic inorganic cured body using the carbon fiber reinforcing material.

(Prior Art) Due to its excellent mechanical properties such as specific strength, specific modulus of elasticity, etc. and chemical stability, carbon fiber has been recognized for its usefulness in a wide range of fields and has been used in large quantities. In these fields, carbon fibers are commonly used as reinforcing materials for composite materials. In addition to polyacrylonitrile (PAN)-based carbon fibers, pitch-based carbon fibers made from inexpensive pitch have recently been developed.
There is a trend toward using carbon fiber, which is inexpensive and has high performance, to cover the fabric.

On the other hand, hardened bodies manufactured from cement-based materials have high compressive strength and are inexpensive, so they are used in large quantities mainly in the field of civil engineering and construction. Often used in conjunction with other materials.

A hardened cementitious material reinforced with carbon fiber, which is a composite of both, has strength properties that could not be achieved with conventional hardened cementitious materials due to the excellent mechanical and chemical properties of the fibers. It is expected to be a new construction material with properties such as deformability, elasticity, and high durability, and has been used for raised floors and curtain walls.

However, these carbon fiber reinforced inorganic cured bodies (CFRC)
) often come into contact with metal materials such as steel, which is the most common structural material. Furthermore, in order to impart toughness to CFRC, composites with metal materials are often actively carried out, and research in this field has been active in recent years.

By the way, in general, the pH of the hardened cement material is -1
Since it can be regarded as a buffer solution system of about 2.5 degrees, it is the best anti-corrosion environment for many metals, including steel, to form a thermodynamically stable passive state in such an alkaline environment. be. However, carbon fiber has conductivity and is a material with a potential comparable to precious metals, so it forms a galvanic cell with metals with a lower potential such as steel and iron alloys. Tends to increase corrosion rate.

Previous methods to solve this problem include using stainless steel reinforcing bars instead of ordinary steel or galvanized steel, and using polymers with a resistance of 100Ω or more between iron or iron alloys and carbon fiber reinforced cement materials. Or a method of forming an electrically insulating layer made of an inorganic material (JP-A-80-188448, JP-A-81-2B1553, JP-A-81-22)
No. 7038) and the like are known.

These methods require the use of expensive stainless steel instead of ordinary steel or the formation of an electrically insulating layer between iron and iron alloys, so the scope of use and handling methods for carbon fiber-reinforced cementitious materials are limited. and processing methods etc. are limited. In addition, since an electrically insulating layer is formed between carbon fiber and iron or iron alloy, even when painting iron or iron alloy, there are always defects in the coating, and in those areas the base material is damaged. It will be exposed directly to the environment. In such a case, the worst area ratio of small anode (steel material, etc.)/large cathode (carbon fiber) will result, and as a result, the corrosion rate will increase dramatically.

(Problems to be Solved by the Invention) The present invention attempts to solve the above-mentioned problem of corrosion of steel and iron alloys by controlling the surface potential of carbon fibers, which is the direct cause of galvanic corrosion. be.

Further, by using carbon fibers whose surface potential is controlled in this manner as a reinforcing material for a hydraulic inorganic cured body, a hydraulic inorganic cured body that is less likely to cause galvanic corrosion is provided.

(Means and Effects for Solving the Problems) The carbon fiber reinforcing material of the present invention is one in which the surface potential of the carbon fibers is reduced to a base potential by subjecting the carbon fibers to a surface treatment. That is, it is a carbon fiber reinforcing material in which the surface of carbon fibers is coated with an epoxy resin to which metal powder having an average diameter of 10 na+ to 500 na and having a potential lower than that of carbon is added.

Furthermore, it is a carbon fiber reinforced hydraulic inorganic cured body having excellent galvanic corrosion resistance, in which the surface-treated carbon fiber reinforcing material is contained in the hydraulic inorganic cured body.

Generally, empirically, there is a difference of T between overvoltage (η) and current (i).
Since the relationship of af'el line η-ma-bj7ogi is established, the corrosion current, which is a factor that determines the corrosion rate, decreases exponentially by reducing the potential difference. Usually p)1
-12.5, the potential of carbon fiber is approximately 0.2V
The potential of steel is about -0.5V, and the potential difference is about 0.
There is about 7v.

Therefore, if carbon fiber, which is the direct cause of galvanic corrosion of steel and iron alloys, is subjected to surface treatment to lower the electrical potential,
The corrosion current during galvanic cell formation is significantly reduced, and the corrosion rate of steel and iron alloys used together is reduced. Thereby, a carbon fiber reinforcing material with excellent galvanic corrosion prevention properties and a carbon fiber reinforced hydraulic inorganic cured body using the reinforcing material can be obtained.

The surface treatment method of making the surface potential of the carbon fiber less noble in the present invention is a surface treatment method of coating the surface of the carbon fiber with an epoxy resin containing a metal powder that can serve as a sacrificial anode.

Furthermore, if a carbon fiber whose surface oxygen atomic content is increased by surface oxidation treatment is used, it becomes a carbon fiber reinforcing material that is effective in preventing corrosion of steel materials and the like.

In the surface treatment method of the present invention, metal powder dispersed in an epoxy resin serves as a sacrificial anode to suppress corrosion of iron or iron alloys that come into contact with carbon fibers. Therefore, the metal powder in the epoxy resin that coats the carbon fibers is preferably a metal powder whose standard potential is more base than that of carbon, and whose potential is about the same as that of iron or which is more base than iron. These metal powders include Fe, Cr, Mg,
Be.

Examples include those containing at least one of Aρ, Zn, and Cd.

Examples of materials suitable for use in the present invention include iron powder, stainless steel powder, cadmium powder, zinc powder, magnesium alloy powder, beryllium powder, and aluminum flakes.

The shape of the metal powder may be spherical, flaky or fibrous, with an average diameter of 10 nm to 50 nm.
It is in the range of 0-, preferably in the range of 10 nm to 100 m. The average diameter here is the average of the maximum diameters of the cross sections of the metal powder.

Those with an average diameter of less than Lon11 are unstable and difficult to handle due to problems such as dust explosion. Also, the average diameter is 500
- is not preferable because the dispersibility in the resin becomes poor. The amount of metal powder to be blended in the epoxy resin is preferably about 1 to 10 wt% from the viewpoint of workability, but is not particularly limited.

Epoxy resins that can be used include bisphenol A type, bisphenol F type, bisphenol AD type, novolac type, etc., and those modified with urethane, tar, phenol, xylene, coumaron, ketone, etc. may also be used.

As the curing agent, known curing agents such as amine type, polyaminoamide type, acid and acid anhydride type can be used. When curing the epoxy resin, various curing accelerators may be added. Further, when dispersing the metal powder, a small amount of a surfactant, a coupling agent, an antioxidant, etc. may be added as necessary to improve dispersibility.

In addition, when the carbon fibers used are subjected to surface oxidation treatment so that the oxygen atom/carbon atomic ratio (O/C) on the surface becomes 0.1 or more, compared to carbon fibers before surface oxidation, saturated calcium hydroxide The surface potential inside is about 0. Since LV becomes less noble, if the carbon fiber is surface oxidized and then further surface treated with the resin, the surface potential of the carbon fiber will become more noble, making it the most effective carbon fiber reinforcing material for galvanic corrosion prevention. .

Examples of surface oxidation treatment methods include ordinary air oxidation, electrolytic oxidation, and plasma oxidation treatment methods. The surface oxidation conditions in the present invention are E S CA (ElectronSp
electronoscopy for chemical A
In the surface analysis by
Carbon atomic ratio (O/C) is 0.1 or more, preferably 0.2
It is desirable to do more than that. Oxygen atom/carbon atom ratio (O
/C) is the ratio of the number of oxygen atoms and the number of carbon atoms calculated from the 01s and C1s peaks in the ESCA spectrum.

The surface potential of the carbon fibers surface-treated in this manner becomes less noble, the potential difference between the steel and the iron alloy decreases, and the corrosion potential and corrosion current during coupling decrease, resulting in a decrease in the corrosion rate.

The carbon fibers used in the present invention include polyacrylonitrile (
There are pitch-based carbon fibers made from tar pitch, and various types of commercially available products can be produced by hand. The form of such carbon fibers is not limited, and may be in the form of continuous fibers, woven fabrics, nets, strands, felt, short fibers, etc., depending on the final purpose of the product and other factors. Use with.

The method of coating carbon fibers with an epoxy resin containing metal powder according to the present invention is applicable to all of these carbon fibers, and is not limited to the raw materials, shapes, etc. of the carbon fibers. Carbon fibers that have been subjected to sizing treatment may be used as is, but it is preferable to remove the sizing agent before surface oxidation treatment.

On the other hand, hydraulic inorganic materials such as mortar, concrete, or calcium silicate materials, which form a stable environment for iron and iron alloys, can be used as short fibers, chopped fibers, continuous fibers, or carbon fibers that have undergone the above surface treatment. To provide a carbon fiber-reinforced hydraulic inorganic hardened body that can be easily composited with steel materials by being used as a reinforcing material in a mesh-like state, compared to a hydraulic inorganic hardened body reinforced with ordinary carbon fibers. I can do it.

This carbon fiber-reinforced hydraulic inorganic hardened body uses iron or an iron alloy as a reinforcing material, and when the carbon fibers and the iron or iron alloy come into contact, the potential difference between the carbon fibers of the present invention and the reinforcing bars is small. The galvanic corrosion current becomes smaller and the corrosion rate of iron and iron alloys decreases. Therefore, compared to carbon fiber-reinforced hydraulic inorganic cured bodies using ordinary carbon fibers, the corrosion rate of iron and iron alloys is significantly reduced, resulting in improved durability and reliability as a building material.

(Example) Example 1 PAN-based carbon fiber bundle (near diameter, 5 m, 12,000
Filament, O/C ratio -0,0862, Heitzl, UK
(manufactured by Gelafil Co., Ltd.) and an epoxy resin (main material: Ebicoat 828) to which iron powder (manufactured by Fukuda Metals Co., Ltd.) whose surface standard potential in a saturated calcium hydroxide aqueous solution is approximately -0, 71V is added.
, curing agent: 5E-11s (manufactured by Yuka Shikuru Co., Ltd.), and 8
Cured at 0°C.

After curing, the volume percent of carbon fiber in the cured product is approximately 51 vof
It became I%. The average particle diameter of the iron powder used and the amount of iron powder added to the epoxy resin are shown in Table 1.

The potential of the treated carbon fiber bundle was determined using a silver-silver chloride electrode (Ag/AgCf!/sat, Ki) as a reference electrode.
Table 1 shows the results of measurements using a conventional electrometer in a saturated aqueous calcium hydroxide solution (pH-12.5), which forms an environment similar to that in a hardened cement material.

Note that the potentials used in Table 1 are values based on a standard hydrogen electrode, with the equilibrium potential of the silver-silver chloride electrode being 0.197V. In addition, the surface potential of the carbon fiber bundle used was 0.1
47 (V 5 NHE).

Table 1 Iron powder particle size Iron powder addition amount Surface potential ca > (vt%) (V vs NH
E) 83.9 4.78 -0.0082
3.1 4.78 -0.02347.4
4.76 0.01733.9
146 0.077 Example 2 The same PAN-based carbon fiber bundle as used in Example 1 was subjected to plasma oxidation treatment, and then this carbon fiber bundle (fiber near, 5 m,
Epoxy resin (main material: Ebicoat 828, curing agent: 5E) containing 12.000 filament, O/C ratio ■0°121) and iron powder (manufactured by Fukuda Metals Co., Ltd.) with an average particle system of about 33.9. -11, manufactured by Yuka Shell Co., Ltd.) and hardened at 80°C.

The surface standard potential in a saturated calcium hydroxide aqueous solution is approximately -
〇, The amount of 71V iron powder added is 4 to epoxy resin.
．． It was set to 76vt%. The potential of this carbon fiber bundle was measured using a silver-silver chloride electrode (Ag/AgCII/sat,
Table 2 shows the results of measurements using a conventional electrometer in a saturated 7 kl (IJ) lucium aqueous solution.

Example 3 The same PAN-based carbon fiber bundle as used in Example 1 (near yarn, 5 m, 12,000 filaments, O/C ratio -0,
0882) with an epoxy resin (main material: Ebicoat 828, curing agent: 5E-11, manufactured by Yuka Shell Co., Ltd.) to which aluminum powder (manufactured by Kojundo Kagaku Kenkyujo) with an average particle size of approximately 3.0- is added. and cured at 80°C. The amount of aluminum powder added with a surface potential of approximately -o, sav in a saturated calcium hydroxide aqueous solution is 4.76 w with respect to the epoxy resin.
It was set as t%.

Using the potential of this carbon fiber bundle as a reference electrode, a silver-silver chloride electrode (Ag/A g C1!/sat, K C12)
Table 2 shows the results of measurement using a conventional electrometer in a saturated calcium hydroxide aqueous solution.

Comparative Example 1 The same PAN-based carbon fiber bundle as used in Example 1 (fiber near, !os, 12,000 filaments, O/C ratio -0)
, 0862) with epoxy resin (main material: Ebicoat 828
, curing agent: 5E-11, manufactured by Yuka Shell Co., Ltd.), and 8
Cured at 0°C.

Using the potential of this carbon fiber bundle as a reference electrode, a silver-silver chloride electrode (Ag/AgCN/sat, KCN
) was measured in a saturated aqueous calcium hydroxide solution using an ordinary electrometer, and the results are shown in Table 2.

Comparative Example 2 The potential of pitch-based carbon fiber (O/C ratio -0,0344, manufactured by Nippon Steel Corporation) was measured using a silver-silver chloride electrode (A) as a reference electrode.
Table 2 shows the results of measurements using an ordinary electrometer in a saturated calcium hydroxide aqueous solution using the following formula: g/A g CII/sat, K Cfl ).

Table 2 Surface potential (Vys Example 2 -0.103 Example 3 -0.153 Comparative example 1 0.147 Comparative example 2 0.177 NHE) Example 4 Same PAN-based carbon fiber as used in Example 1 The bundle was surface-treated in the same manner as in Example 1 using iron powder with an average particle size of 83.9 m so that the amount added to the epoxy resin was 4.76 wt%. (using silica sand) at a volume ratio (Vf) of 2%. The average fiber length of the carbon fiber bundle was approximately 4 km.

Reinforcing bars (5 mmφ) were embedded in mortar with a water/cement ratio of 0.5 so as to be in contact with carbon fibers, and after curing in humid air for one week, they were exposed outdoors for six months, during which time
Artificial seawater was sprayed every 4 hours.

After 6 months of exposure, the mortar was crushed and the rusted area of the reinforcing bars was examined. The results are shown in Table 3.

Comparative Example 3 The same pitch-based carbon fiber used in Comparative Example 2 was mixed with Vf in mortar (using ordinary Portland cement and No. 8 silica sand).
It was distributed so that it was 2%. The remaining fiber length of carbon fiber is approximately 311! It was I.

Reinforcing bars (5 nusφ) were embedded in mortar with a water/cement ratio of 0.5 so as to be in contact with carbon fibers, and after curing in humid air for 1 week, they were exposed outdoors for 6 months, during which time artificial heating was performed every 24 hours. Sprayed with seawater.

After 6 months of exposure, the mortar was crushed and the rusting status of the reinforcing bars was examined. The results are shown in Table 3.

Comparative Example 4 The same PAN-based carbon fiber bundle used in Example 1 was surface-treated with epoxy resin in the same manner as in Comparative Example 1, and the volume ratio (Vf ) was distributed to 2%. The average fiber length of the carbon fiber bundle was approximately 40 mm.

Reinforcing bars (5vaIlφ) were embedded in mortar with a water/cement ratio of 0.5 so as to be in contact with the carbon fibers, and after curing in humid air for one week, they were exposed outdoors for six months, during which time artificial Sprayed with seawater.

After 6 months of exposure, the mortar was crushed and the rusted area of the reinforcing bars was examined. The results are shown in Table 3.

Table 3 Rust area of reinforcing steel (%) Example 40.1 Comparative example 36.8 Comparative example 4i, 9 As described above, by applying surface treatment to carbon fiber, the surface potential of carbon fiber becomes less noble. It was found that as a result, the potential difference with the reinforcing steel was reduced and the corrosion rate was reduced.

(Effects of the Invention) According to the present invention, it has become possible to obtain a carbon fiber reinforcing material and a carbon fiber reinforced hydraulic inorganic material that are unlikely to cause galvanic corrosion between them and iron and iron alloys. Therefore,
Compared to carbon fiber-reinforced hydraulic inorganic materials using ordinary carbon fibers, the corrosion rate of iron and iron alloys that come into contact with this material is significantly reduced, resulting in improved durability and reliability as a building material.

teenager Reason Man

Claims (1)

[Claims] 1. An average diameter of 10 nm to 5, which exhibits a surface potential less noble than carbon.
A carbon fiber reinforcing material made by coating the surface of carbon fiber with epoxy resin containing 00 μm metal powder. 2. The carbon fiber reinforcing material according to claim 1, wherein the carbon fiber has an oxygen atom/carbon atomic ratio (O/C) on the surface of the carbon fiber of 0.1 or more. 3. A carbon fiber-reinforced hydraulic inorganic hardened body, characterized in that the carbon fiber reinforcing material according to claim 1 or 2 is contained in mortar, concrete, or a calcium silicate-based material.