JP2000241351A - Method for diagnosing deterioration of cross-linked polyethylene using fluorescence analyzer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and accurately diagnose an aging deterioration of an electric wire, a cable or the like covered with a polymer material by measuring a fluorescent intensity of a crosslinked polyethylene (test sample) receiving various deterioration factors, and comparing it with that of the same wavelength of a crosslinked polyethylene not receiving a deterioration. SOLUTION: A fluorescent spectrum is measured by using a fluorescent analyzer for a coating material (test sample) made of a polymer material or particularly a crosslinked polyethylene, and that generated by an exciting light incident in this case is measured. It is compared with that in the same wavelength of a crosslinked polyethylene sample before deterioration obtained in advance, and the degree of a deterioration of the test sample is diagnosed. According to this method, since its deterioration degree of a resin itself can be measured by using a small amount of the sample, a deteriorated state of the coating material such as an electric wire, a cable or the like can be simply diagnosed in a used state as it is. When the relationship between the intensity of the deteriorated sample and a mechanical strength is obtained, an estimated residual strength or the like can be obtained without damaging the sample.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a coating material used mainly for insulation and sheathing of electric wires and cables,
Especially useful for deterioration diagnosis and life estimation of cross-linked polyethylene,
The present invention relates to a method for diagnosing deterioration of a polymer.

[0002]

2. Description of the Related Art In recent years, various polymer materials have been used as materials for electric wires and cables, but crosslinked polyethylene has been widely used especially as an insulating material because of its excellent electrical properties. Along with this, there is a demand for the development of a technology capable of easily and accurately diagnosing the deterioration of this material over time.

Conventionally, in order to diagnose the deterioration of the covering material of an electric wire / cable and estimate the service life, apart from the actually laid electric wire / cable, an exposure test and a deterioration acceleration test are performed on the same kind of electric wire / cable, and elongation and tensile tests are performed. 2. Description of the Related Art Changes in mechanical properties such as strength over time are mainly examined, deterioration is estimated from the results, and life is estimated.

[0004]

However, in such a method, the diagnosis of deterioration and the estimation of life require a lot of time and effort, and the result is not necessarily that of the actual cable or wire.
There is a problem that the deterioration of the cable is not always correctly indicated. In other words, since the environment in which the wires and cables are laid differs from one another, in order to correctly diagnose the deterioration of the actually laid wires and cables, the deterioration of the actually laid wires and cables is nondestructive or quasi-destructive. It is desirable to obtain information, diagnose deterioration based on this, and estimate the life.

However, in the conventional method, in order to diagnose deterioration from changes in mechanical properties such as elongation and tensile strength,
Since it is necessary to collect a large amount of test samples from actually laid wires and cables, it is often impossible in practice, and in most cases, wires and cables prepared separately from the actually laid wires and cables Had to diagnose deterioration.

[0006] Recently, from the actually laid wires and cables,
Attempts have also been made to take very few samples and determine the degree of degradation of the coating material using recent instrumental analyzers. For example, a small amount of sample collected from an electric wire or cable is examined for an infrared absorption spectrum by a multiple reflection type Fourier transform infrared spectrometer (FT-IR-ATR), and a specific peak in a specific component is obtained from the obtained spectrum. To determine the degree of degradation by identifying changes in
In the same way, an attempt to measure the degree of deterioration by measuring the change of a specific peak in a specific component by measuring the Raman spectrum in a finer region using Raman spectroscopy has been made. Is being done.

[0007] The present invention has been made in view of such a conventional circumstance, and the deterioration of a polymer material, which deteriorates and emits fluorescence, can be appropriately performed without destroying a product or by using a small amount of a sample. Provided is a non-destructive deterioration diagnosis method for a polymer material that can be diagnosed, easily and accurately diagnoses the aging of an electric wire or a cable coated with such a material, and can estimate the remaining life. The purpose is to:

[0008]

According to the method for diagnosing nondestructive deterioration of a resin according to the present invention, a fluorescence spectrum of a coating material made of a polymer resin, particularly, a crosslinked polyethylene is measured using a fluorescence spectroscope. It is characterized in that the intensity of the fluorescent component generated by the excitation light is measured, and the degree of deterioration is diagnosed by comparing the fluorescent intensity of the same wavelength as that of the crosslinked polyethylene sample before deterioration obtained in advance.

The diagnostic method of the present invention is used for diagnosing deterioration of a polymer by heat, ultraviolet rays and radiation, by positively utilizing a phenomenon in which a degradation component such as polyene generated at the time of polymer degradation appears as a fluorescent component. It is. That is, the fluorescence intensity of a test sample that has undergone environmental degradation is measured using a fluorescence spectrometer, and the degree of degradation is determined from the difference in the fluorescence intensity of the uncrosslinked polyethylene at the same wavelength.

[0010] As the fluorescence spectrometer used in the present invention,
Any spectrofluorometer, fluorometer, or fluorescence spectrophotometer can be used with any device that can measure the spectrum of fluorescence generated by irradiating a polymer sample with excitation light. It is.

[0011]

In the method of the present invention, the degree of deterioration of the resin itself can be determined by measuring the change in the fluorescence intensity using a very small amount of sample and using a fluorescence spectrometer.
It is possible to easily diagnose the deterioration state of the covering material while keeping the wires and cables in use. Further, it is possible to determine the deterioration of the polymer itself, and the present invention can be applied to other polymer materials such as polyolefin.

[0012]

Embodiments of the present invention will be described below.

[0013] A cross-linking agent or the like is added to low-density polyethylene to form a cross-linked polyethylene sheet having a thickness of about 1 mm.
Tested.

Example 1 First, as a deterioration test, an accelerated heat deterioration test was performed using a gear aging tester. Test temperature is 160 ° C and 100 ° C
And two types.

Example 1-1 First, a heat deterioration test sample at 160 ° C. was tested.

The measurement of the original and thermally degraded samples by a fluorescence spectrometer uses a xenon lamp as a light source.
The sample was irradiated with excitation light having a wavelength of 325 nm, and the spectrum of fluorescence generated by excitation from the sample was measured. The measured fluorescence wavelength was 300 to 600 nm. FIG. 1 shows the spectrum of the original sample, and FIG. 2 shows the spectrum of the sample deteriorated at 160 ° C. for 4 days.

As is apparent from FIGS. 1 and 2, the fluorescence intensity changed remarkably around the fluorescence wavelength of 370 nm. Therefore, the fluorescence intensity at a fluorescence wavelength of 370 nm was determined and used as a criterion for determining deterioration.

At 160 ° C., the composition was thermally degraded for 1 to 16 days, and the fluorescence intensity at a fluorescence wavelength of 370 nm in the fluorescence spectrum was measured. Table 1 shows the relationship between the fluorescence intensity and the number of days of deterioration. FIG. 3 summarizes the results.

[0019]

[Table 1] As is clear from Table 1 and FIG. 3, the fluorescence intensity decreases as the number of days of deterioration increases, and the degree of deterioration can be clearly shown.

A small amount of a sample is sampled from a material whose degree of deterioration is unknown, and a fluorescence spectrum is taken from the sample using a fluorescence spectroscope. For example, the fluorescence intensity is measured, and the measured value is plotted on the line shown in FIG. , It is possible to estimate the number of days of deterioration of the material.

Further, as shown in FIG. 4, it is easy to obtain the estimated residual intensity and the like without destroying the sample by previously obtaining the relationship between the fluorescence intensity and the mechanical intensity of the deteriorated sample.

Example 1-2 Next, a heat deterioration test sample at 100 ° C. was tested.

As in the case of 160 ° C., the measurement of the thermally degraded sample with a fluorescence spectrometer was performed at a fluorescence wavelength of 300 to 600 nm using excitation light having a wavelength of 325 nm. 100 ℃
The fluorescence intensity at a fluorescence wavelength of 370 nm in the fluorescence spectrum was also measured for the sample that had been degraded for up to 50 days. Table 2 shows the relationship between the fluorescence intensity and the number of days of deterioration. FIG. 5 shows the relationship between the number of days of deterioration, the fluorescence intensity, and the mechanical intensity.

[0024]

[Table 2] As is clear from Table 2 and FIG. 5, in the case of 100 ° C., almost no change in elongation was observed up to 250 days.
A remarkable decrease in fluorescence intensity was observed. That is, in this case as well, the decrease in the fluorescence intensity with the increase in the number of days of deterioration is clear, clearly indicating that the present method is effective in determining the degree of deterioration.

Embodiment 2 In this embodiment, an application of the present deterioration determination method to radiation deterioration of a covering material of an electric wire / cable used in a radiation region is attempted. As the test sample, the crosslinked polyethylene used in Example 1 was used.

Using Co as a radiation source, γ-ray dose,
Three types of samples, 0.125 MGy, 0.5 MGy, and 1 MGy, were prepared. The unirradiated sample and the irradiated sample were measured using a fluorescence spectrometer.
Fluorescence spectra were measured using nm excitation light.
The spectrum of the unirradiated sample is shown in FIG. 1, and the sample with an irradiation dose of 1 MGy is shown in FIG. That is, a decrease in the fluorescence intensity is observed in the γ-irradiated sample as compared with the unirradiated sample. Table 3 shows the relationship between the fluorescence intensity and the irradiation dose. FIG. 7 summarizes the results and mechanical characteristics.

[0027]

[Table 3] Among the properties required for wire / cable coating materials are electrical properties. One of its electrical properties is the volume resistivity, which is regarded as a measure of the insulating property of the coating material. Therefore, the volume resistivity was measured in order to confirm the degree of deterioration of the γ-irradiated sample. The results are shown in FIG. Deterioration was also confirmed in the volume resistivity as an electrical characteristic.

As described above, regarding the deterioration due to radiation, a clear change in the fluorescence intensity was recognized, and it was confirmed that the deterioration degree can be determined by this method.

[0029]

As described above, according to the method of the present invention, the deterioration of a polymer used for insulation and protection of an electric wire cable due to the environment is measured by using a fluorescence spectrometer to measure the change in fluorescence intensity. From the above, it was found that the determination could be made. That is, it is possible to diagnose the deterioration of the resin by using a very small amount of sample collected from the electric wires and cables.

Since the method of the present invention specifies the change in deterioration of the polymer itself constituting the coating material, it can be applied not only to crosslinked polyethylene but also to other polymers.

Further, according to the principle of the present method, the method can be applied to all deteriorations related to polymer deterioration such as deterioration due to heating, ultraviolet light deterioration, and radiation deterioration, and the application range is extremely wide. It is possible to easily and accurately determine and diagnose deterioration of not only materials for electric wires and cables but also polymer materials used for other purposes.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a fluorescence spectrum of an original sample of a crosslinked polyethylene used in the present invention.

FIG. 2 is a view showing an example of a fluorescence spectrum of a sample after heating a cross-linked polyethylene used in the present invention.

FIG. 3 is a graph showing the relationship between the number of days of deterioration and the fluorescence intensity of a thermally deteriorated sample of crosslinked polyethylene at 160 ° C.

FIG. 4 is a graph showing the relationship between the number of days of deterioration of a cross-linked polyethylene at 160 ° C. and the mechanical properties of the heat-degraded sample.

FIG. 5 is a graph showing the relationship between the number of days of deterioration of a crosslinked polyethylene at 100 ° C. and the mechanical properties of the sample after heat deterioration.

FIG. 6 is a diagram showing an example of a fluorescence spectrum of a crosslinked polyethylene sample after γ-ray irradiation.

FIG. 7 is a graph showing the relationship between irradiation dose, fluorescence intensity, and mechanical properties of a sample degraded by γ-ray irradiation of crosslinked polyethylene.

FIG. 8 is a graph showing the relationship between irradiation dose and electrical characteristics of a sample degraded by gamma irradiation of crosslinked polyethylene.

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Claims (4)

[Claims] 1. A fluorescence spectrum of a material made of cross-linked polyethylene subjected to various deterioration factors is measured using a fluorescence spectrometer, and the fluorescence intensity is obtained in advance and the cross-linked polyethylene before deterioration and the intensity at a specific wavelength are compared with each other. A method for diagnosing deterioration of a crosslinked polyethylene material, comprising diagnosing the degree of deterioration of the crosslinked polyethylene material by comparing. 2. The method for diagnosing deterioration of a crosslinked polyethylene material according to claim 1, wherein the wavelength of the excitation light used for measuring the fluorescence spectrum is 325 nm. 3. The method for diagnosing deterioration of a crosslinked polyethylene material according to claim 1, wherein the various deterioration factors are at least one of heat, radiation, light (including ultraviolet rays), and environmental deterioration factors. 4. The method according to claim 1, wherein the specific wavelength is 370 nm.