JPS60243554A - Detection of surface characteristics - Google Patents

Abstract

PURPOSE:To enable measurement of carbon fibers, etc. for their surface characteristics on the manufacturing line, by detecting a current value with selection of carbon fiber and graphite fiber which have undergone surface oxydation processes as an electrode on one side and changing a electric potential in an electrolytic solution and within the specified voltage. CONSTITUTION:Electrolytic solution, for instance, aqueous solution of phosphoric acid is admitted in an electrolytic solution cell 4. Then, a surface oxidation treated carbon fiber or a tow of a plurality of the fibers are allowed to touch a dielectric roller 2 and conveyed continuously to the electrolytic solution and taken up by non-dielectric roller 3. Further, a counter electrode 5, for instance, platinum electrode and the reference electrode, for instance, Ag/AgCl electrode are installed. Then, a scanning potential is applied without exceeding the electrolytic potential of the electrolytic solution and current-potential curve is detected with a polarographic meter 7. Then, from change of current values oxidation conditions of carbon and graphite fibers are detected. As the oxidation condition of the fibers can be detected continuously, an excellent composite can be obtained from these fibers.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a novel method for detecting surface properties of carbon fibers.

[Prior art]

The strength properties of the composite and its durability depend on the bonding strength between the reinforcing fibers and the resin, and for this reason carbon fibers require surface treatments such as vapor phase oxidation, liquid phase oxidant treatment, electrolytic oxidation. Surface treatment by oxidation, such as treatment, is generally carried out, and
In addition to the above publication, various proposals have been made.

Depending on the degree of these surface treatments, the surface properties of carbon fibers change significantly chemically and physically, and the composite properties are affected (although the surface condition is sufficient to clarify the optimal surface treatment for the composite properties). Examples of surface analysis of carbon fiber obtained by changing surface treatment methods and conditions include measurement of specific surface area by gas adsorption, titration analysis, and analysis of functional groups by ESCA, etc. Although there are many methods, these studies are merely analytical studies at the research stage, and it is practically impossible to use these methods for industrial quality control.

[Purpose of the invention]

The inventors of the present invention have completed the present invention as a result of repeated studies to develop a practical detection method that can accurately and continuously capture the surface characteristics of carbon fibers that are well correlated with composite characteristics. Ta.

The first object of the present invention is to apply surface analysis of carbon fibers to product inspection in factories, and the second object is to perform surface treatment process control by directly linking it to manufacturing lines.

[Structure of the invention]

That is, the gist of the present invention is to run carbon fibers or graphite fibers in an electrolyte solution, and in the solution, between 10,000 carbon fibers or graphite fibers as electrodes and counter electrodes provided in the solution. , is a method for detecting the surface characteristics of carbon fibers or graphite fibers, which is characterized by continuously detecting changes in current value caused by changing the potential within a voltage range below the electrolytic voltage.

Many attempts have been made to apply carbon fiber to electrodes, and there are some known examples of applying the potential scanning method to chemical modification of carbon fiber electrodes and analysis of glabellar compounds.

However, there has never been an example in which the characteristic values obtained from the potential scanning method have been studied in relation to the strength characteristics of the composite (
This is a fact that was revealed for the first time as a result of our intensive investigation. Although the details of how the characteristic values obtained by the potential scanning method are related to the surface characteristics of carbon fibers are unknown,
This is probably a characteristic that corresponds to the concentration of functional groups that participate in redox reactions on the surface of carbon fibers and the physical surface area.Separating from the details, as is clear from the examples, the potential scanning method The obtained characteristic values correspond well to the strength characteristics of the composite and are considered to be an index expressing the magnitude of the interfacial bonding force, and the strength characteristics of the composite can be maximized by controlling the characteristic values. .

The present invention will be specifically explained below.

Measuring devices suitable for carrying out the present invention include, for example, the first to
Although it is shown in Figure 3, any device that can perform measurements using carbon fiber as a working electrode may be used.

The carbon fiber sample may be passed through the electrolytic solution so that the electrode surface area is constant, or one or more tows may be passed through the electrolyte solution at the same time. When threading a continuous yarn, the carbon fibers are brought into contact with a conductive roller outside the electrolytic cell to apply a potential to the carbon fibers. In this case, the number of conductive rollers may be one, or two or more may be used on both sides of the electrolytic cell. Alternatively, the length of the sample may be controlled by immersing the carbon fiber in the electrolyte using a non-conductive roller as shown in Figures 1 and 2, or by utilizing the overflow of the electrolyte as shown in Figure 3. A method of regulating the sample length by immersing carbon fibers is also possible.

The counter electrode may be any electrode having a large electrode area and material that does not cause errors in measurement, such as a platinum electrode.

In addition, as a standard electrode, a saturated calomel electrode, kg/Ag
C1 electrode etc. can be used.

The electrolyte solution used in the present invention can basically be anything as long as it can conduct electricity (preferred examples include potassium chloride, sodium nitrate, potassium hydroxide, sodium hydroxide, etc., but concentrated sulfuric acid, etc.) can be used as the electrolyte solution. There must be no intercalation compound with the carbon fiber.

The electrolyte concentration is preferably in the range of 1 to 20%.

As a potential scanning detection device, a general electrochemical detection device is used, such as cyclic portummetry, differential polarography, or alternating current polarography, and any of these devices may be used.

For example, when detecting with cyclic portummetry, connect a carbon fiber as a working electrode, an AgZAgCl electrode as a standard electrode, and a platinum electrode as a counter electrode to a bote/shotostat connected to a function generator and a recorder. This is possible.

The carbon fibers referred to in the present invention are not limited to acrylic fibers, but are also so-called pitch-based fibers? It also includes cellulose-based carbon fibers and graphite fibers.

Carbon fiber sample forms include tow, sheet, cloth,
Any material can be used as long as it can maintain its shape as an electrode, such as a pH electrode, and it is okay even if resin such as a sizing agent is attached to the sample, but in this case, the effective surface area will decrease, so it is necessary to compensate for this. There is.

It is preferable that the carbon fibers or graphite fibers used to carry out the present invention have been previously subjected to surface oxidation treatment using a dry or wet method, but these treatments may not necessarily be performed. For example, if it has an elastic modulus of about 24 t/m', it can be coated as it is untreated.
It is fully possible to apply the present invention from the viewpoint of understanding positive characteristics.

〔Example〕

The present invention will be specifically explained below with reference to Examples.

Example 1 Pyrophil T-1 (Mitsubishi Rayon Co., Ltd.) 12.0
A non-sized carbon fiber tow 1 of 00 filament is used as a working electrode and immersed in an electrolytic solution 8 so that the immersion sample length is 30 cIrL using the apparatus 4 shown in FIG. using the Kamiki Seisakusho Portummetry Analyzer P-1 using Ag/AgCl electrodes.
Potential scanning was performed at 100. A 5% sour/acid aqueous solution was used as the electrolytic solution, nitrogen was bubbled through it, the influence of residual oxygen was removed, and the sample carbon fiber was run at a speed of 0.1 m/min.

The potential scanning range is set so as not to exceed the electrolytic potential of the electrolytic solution [-
The standard conditions were a range from 0.2 V to +0.8 V, and the standard scanning speed was 20 mV/sec.

Draw a current-potential curve with an X-Y recorder, and
The current value l was read using a potential of +0.4 V with respect to the AgC1 electrode as a reference potential, and ipB was calculated according to the following formula.

iph = '(j'A)/total sample surface area (crfL
”) In the formula, the total surface area of the sample is the weight of the sample, the number of filaments,
The value calculated from the basis weight 2 and density was used.

Co/posit characteristics were determined by creating a unidirectional prepreg using Pyrofil #32°Resi/ (trademark manufactured by Mitsubishi Rayo Co., Ltd.) as a matrix, molding it into a flat plate at 130°C for 3 hours, and then preparing a test piece of lO size x 15m true x 2 dragons. The interlaminar shear stress (IL) was measured by the short beam method along the fiber axis.
Ipa% and conoposite I obtained for this sample evaluated SS)
LSS is shown in Table 1.

Table 1 Example 2 Elastic modulus obtained by firing acrylic precursor 28
After winding the carbon fiber of t/i+m2 onto a -H bobbin, electrolytic oxidation was performed for 20 seconds in a 5-functional sodium nitrate aqueous solution, and the surface oxidation level was varied by changing the current density.

The electrolytically treated carbon fibers were subsequently passed through a potential scanning treatment tank, washed with water, dried, treated with a sizing agent, and wound onto a bobbin.

Table 2 shows the ILSS of the tp& and conoposite when the surface oxidation level was changed. S carbon fiber is 12,000
The fabric weight was 0.785//m and the density was 1.7751/cnL3. It becomes possible to continuously produce carbon fiber.

[Brief explanation of the drawing]

1-3 illustrate examples of apparatus suitable for carrying out the present invention. 1 Carbon fiber 2 Conductive roller 3 Non-conductive roller 4 Electrolyte solution bath 5 Counter electrode 6 Standard electrode 7 Connection terminal for polarographic analyzer or potentiostat, etc. 8 Electrolyte solution paralysis 2 Flash paralysis 3 Illustration procedure amendment (0 shots) August 22, 1980 1, Indication of Case Special Application No. 59-99759 3, Person making the amendment Relationship with the case Applicant Director, Mitsubishi Rayon Co., Ltd., 3-19 Kyobashi 2-chome, Chuo-ku, Tokyo (603) President: Akio Kawasaki 4, Representative: 2-3-19 Kyobashi, Chuo-ku, Tokyo Address: Date of correction order: 5 pages, 5 lines, 1 differential J → “Differential pulse”

Claims (1)

[Claims] Carbon fibers or graphite fibers are made to run through an electrolyte solution, and in the solution, a potential within a voltage range below the electrolytic voltage is generated between 10,000 electrodes of carbon fibers or graphite fibers and a counter electrode provided in the solution. A method for detecting the surface characteristics of carbon fibers or graphite fibers, which is characterized by continuously detecting changes in current value caused by changing the current value.