Method for detecting filler content in composite insulator silicone rubber

Abstract

The invention discloses a method for detecting the filler content in composite insulator silicone rubber, and relates to the field of content detection.The method comprises the steps that on the basis of a preset frequency value, a terahertz detection platform is adopted to conduct terahertz detection on target composite insulator silicone rubber to obtain a terahertz spectrum signal; determining an absorption coefficient based on the terahertz spectrum signal; based on a preset absorption coefficient-filler content function, determining the filler content corresponding to the target composite insulator silicone rubber according to the absorption coefficient; wherein the preset frequency value and the preset absorption coefficient-filler content function are determined by carrying out terahertz detection on a plurality of silicone rubber samples containing fillers and carrying out statistical analysis on terahertz spectrum signals obtained by detection. According to the invention, rapid, accurate and non-contact filler content detection can be realized.

Description

Technical Field

[0001] The present application relates to the field of content detection, and in particular to a method for detecting filler content in composite insulator silicone rubber. Background Art

[0002] Composite insulators are important insulating parts in power grids. Their main component is silicone rubber. The fillers in silicone rubber can enhance its various properties. The fillers can be aluminum hydroxide and white carbon black. Aluminum hydroxide is an ideal flame retardant filler with stable chemical properties and is not easy to absorb moisture. When the composite insulator fails, it has the functions of flame retardancy and smoke elimination. White carbon black can effectively prevent the deep penetration of oxygen, light and heat energy, and it not only increases the operating time of the composite insulator, but also supplements the mechanical strength of the composite insulator shed.

[0003] In some scenarios, the filler content in composite insulator silicone rubber is usually tested using Fourier infrared spectroscopy, thermogravimetric analysis, etc. These testing methods have the disadvantages of damaging samples, requiring a high testing environment, having complex testing procedures, and being time-consuming. For example, thermogravimetric analysis can accurately detect the various components in silicone rubber, and by monitoring the decomposition of different fillers at different temperatures during the temperature increase process, the quality of the components in silicone rubber can be determined. However, this method is destructive to samples and cannot be tested on site. Summary of the invention

[0004] The purpose of the present application is to provide a method for detecting filler content in composite insulator silicone rubber, which can realize fast, accurate and contactless filler content detection.

[0005] To achieve the above objectives, this application provides the following solutions:

[0006] The present application provides a method for detecting filler content in composite insulator silicone rubber, comprising:

[0007] Obtaining target composite insulator silicone rubber;

[0008] Based on the preset frequency value, a terahertz detection platform is used to perform terahertz detection on the target composite insulator silicone rubber to obtain a terahertz spectrum signal;

[0009] Determining an absorption coefficient based on the terahertz spectral signal;

[0010] Based on a preset absorption coefficient-filler content function, determining the filler content corresponding to the target composite insulator silicone rubber according to the absorption coefficient;

[0011] The preset frequency value and the preset absorption coefficient-filler content function are determined after performing terahertz detection on a plurality of silicone rubber samples containing fillers and performing statistical analysis on the terahertz spectrum signals obtained by the detection.

[0012] According to the specific embodiments provided by the present application, the present application discloses the following technical effects: the present application provides a method for detecting filler content in composite insulator silicone rubber, performs terahertz detection on multiple silicone rubber samples containing fillers, and performs statistical analysis on the terahertz spectrum signals obtained by the detection to determine the preset frequency value and the preset absorption coefficient-filler content function. On this basis, the terahertz detection platform is used to perform terahertz detection on the target composite insulator silicone rubber based on the preset frequency value, and then the absorption coefficient is determined, and then the absorption coefficient is input into the preset absorption coefficient-filler content function to finally obtain the filler content corresponding to the target composite insulator silicone rubber. Whether it is terahertz detection of silicone rubber samples containing fillers or target composite insulator silicone rubber, due to the use of terahertz detection, non-contact detection, fast detection speed and high detection accuracy can be achieved. Furthermore, the present application uses the preset frequency value and the preset absorption coefficient-filler content function determined in advance by experiments in the detection process, without the need to spend extra time to conduct corresponding experiments or processing, and can also obtain the detection results of silicone rubber that fit the actual situation, with higher accuracy and higher efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0014] Figure 1 A schematic flow chart of a method for detecting filler content in composite insulator silicone rubber provided in one embodiment of the present application;

[0015] Figure 2 A schematic diagram of a terahertz detection platform provided in one embodiment of the present application;

[0016] Figure 3 It is a comparison chart of the refractive index of multiple silicone rubber samples containing fillers;

[0017] Figure 4 The terahertz time-domain electric field signal comparison diagram of multiple silicone rubber samples containing fillers;

[0018] Figure 5 A comparison chart of the absorption rates of multiple silicone rubber samples containing fillers and the substances in the samples;

[0019] Figure 6 It is a comparison diagram of multiple silicone rubber samples containing fillers at the 1.21thz characteristic absorption peak;

[0020] Figure 7It is a linear diagram of the 1.21thz characteristic absorption peak and filler content;

[0021] Figure 8 It is a comparison diagram of multiple silicone rubber samples containing fillers at the 1.33thz characteristic absorption peak;

[0022] Fig. 9 This is a linear diagram of the 1.33thz characteristic absorption peak and filler content.

[0023] Figure numerals: 1 - femtosecond pulse laser, 2 - beam splitter, 3 - time delay optical path, 4 - terahertz emitter, 5 - material scanning platform, 6 - terahertz detector, 7 - phase-locked amplifier, 8 - terminal. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0025] Research has found that in non-destructive testing, terahertz testing has the advantages of non-contact testing, fast testing speed, and high testing accuracy, and can be used as an effective means to detect the content of silicone rubber components in composite insulators. The frequency of terahertz waves is between 0.1thz and 10thz, which has a higher resolution than microwave detection. Its energy is small and will not affect the safety of detection personnel. It has good penetration for paper, polymers, textiles, etc. There are multiple characteristic peaks at terahertz frequencies, which can be used to determine the content of various substances in the mixture. Based on this, this application realizes the detection of filler content in composite insulator silicone rubber based on terahertz.

[0026] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0027] In an exemplary embodiment, Figure 1 As shown, a method for detecting filler content in composite insulator silicone rubber is provided. In an embodiment of the present application, the method includes the following steps 101 to 104.

[0028] Step 101, obtaining target composite insulator silicone rubber.

[0029] Step 102: Based on a preset frequency value, a terahertz detection platform is used to perform terahertz detection on the target composite insulator silicone rubber to obtain a terahertz spectrum signal.

[0030] like Figure 2 As shown, the terahertz detection platform includes a femtosecond pulse laser 1, a beam splitter 2, a terahertz detection branch, a material scanning platform 5, a terahertz detector 6, a phase-locked amplifier 7 and a terminal 8.

[0031] Specifically, the material scanning platform 5 is used to carry the target composite insulator silicone rubber; the femtosecond pulse laser 1 is used to generate pulsed laser and send it to the beam splitter 2. The beam splitter 2 is used to split the received laser into two laser beams, and send one of them to the terahertz detection branch, and send the other to the terahertz detector 6; and the power of the laser emitted by the beam splitter 2 to the terahertz detection branch is higher than the power of the laser emitted by the beam splitter 2 to the terahertz detector 6.

[0032] The terahertz detection branch is used to generate a terahertz pulse of the preset frequency value according to the received laser excitation, and irradiate and penetrate the target composite insulator silicone rubber to reach the terahertz detector 6; specifically, the terahertz detection branch includes a time delay optical path 3 and a terahertz transmitter 4 arranged in sequence. In other words, after the beam splitter 2 splits the laser into two, a stronger pump pulse reaches the terahertz transmitter 4 through the time delay optical path 3, and a terahertz signal is generated in the terahertz transmitter 4. The terahertz signal passes through the target composite insulator silicone rubber and reaches the terahertz detector 6 at the same time as another weaker laser beam used as a detection laser pulse.

[0033] The terahertz detector 6 is used to determine the terahertz spectrum signal according to the received laser, and then send the terahertz spectrum signal to the terminal 8 via the phase-locked amplifier 7; the terminal 8 is used to store the terahertz spectrum signal (that is, the terahertz time-domain electric field signal). In fact, the calculation of the subsequent steps 103 and 104 can also be implemented in the terminal 8. The terminal 8 can be a computer.

[0034] Step 103, based on the terahertz spectrum signal, determine the absorption coefficient. It should be noted that the electromagnetic wave oscillation period contained in the terahertz pulse is limited, the spectrum distribution is wide, and the spectrum width of the terahertz pulse emitted by different emission sources is not the same, some range from 0.1thz to tens of thz, while some can reach a spectrum width of more than 100thz. The terahertz detection frequency used in this application is 0thz-3thz. After exceeding 3thz, the sample's absorption rate signal noise is too large, and the absorption characteristic peak cannot be distinguished.

[0035] The terahertz signal is an electromagnetic wave signal. The energy of the terahertz signal propagating in different media changes, which in turn causes the amplitude and phase of the signal to change, as shown in the formula:

[0036] E ref(ω)=E0(ω)·p(ω,L).

[0037] Where E0(ω) is the signal generated by the terahertz transmitter, E ref is the waveform after propagating a distance L in the air, and p(ω,L) is the propagation model of the terahertz wave in the medium, as shown in the following formula:

[0038]

[0039] in, is the complex refractive index and c is the speed of light.

[0040] The terahertz spectrum signal determined by the terahertz detector is a terahertz time-domain electric field signal, which can be transformed by Fourier transform to obtain a terahertz frequency-domain signal, as shown in the following formula:

[0041]

[0042] Among them, E(ω) is the terahertz frequency domain signal, E(t) is the terahertz time domain signal, and A(ω) is the frequency domain amplitude.

[0043] Based on the terahertz frequency domain signal, the refractive index and extinction coefficient of the target composite insulator silicone rubber are determined; the calculation formula of the refractive index n(ω) is:

[0044]

[0045] The calculation formula of the extinction coefficient k(ω) is:

[0046]

[0047] in, is the phase of the terahertz frequency domain signal, ω is the frequency of the terahertz wave, d is the thickness of the target composite insulator silicone rubber, and ρ(ω) is the propagation coefficient.

[0048] Based on Lambert's law, the absorption coefficient is determined according to the extinction coefficient; the calculation formula of the absorption coefficient α(ω) is:

[0049]

[0050] Step 104: Based on a preset absorption coefficient-filler content function, determine the filler content corresponding to the target composite insulator silicone rubber according to the absorption coefficient.

[0051] The preset frequency value and the preset absorption coefficient-filler content function are determined after performing terahertz detection on a plurality of silicone rubber samples containing fillers and performing statistical analysis on the terahertz spectrum signals obtained by the detection.

[0052] In the following specific application example, the process of determining the preset frequency value and the preset absorption coefficient-filler content function includes:

[0053] (1) Obtain multiple silicone rubber samples containing fillers. Specifically, high temperature vulcanized silicone rubber is used as the research object. The multiple silicone rubber samples containing fillers are all set up, using polydimethylsiloxane (PDMS) as the base material of silicone rubber, and aluminum hydroxide and white carbon black are selected as fillers. Among them, PDMS is vinyl terminated, and white carbon black is fumed silica. In addition, a small amount of hydroxyl silicone oil, colorant, and vulcanizer need to be added. The content is less than 10% of the total weight, and there is no absorption peak in the frequency range of 0thz-3thz, which has little effect on the results. The formula of multiple silicone rubber samples containing fillers obtained based on the above conditions can be shown in Table 1 below.

[0054] Table 1

[0055]

[0056]

[0057] After mixing the materials according to Table 1 above, use a rubber mixer to fully mix the components and maintain the temperature at 150°C for heat treatment for 3 hours; then add a vulcanizing agent and vulcanize the silicone rubber in a flat vulcanizer to form a stable silicone rubber sample with a sample size of 50mm×50mm. Since the thickness has a certain influence on the terahertz measurement results, the sample thickness of this application is 2mm to facilitate the extraction of the sample terahertz signal.

[0058] (2) For any silicone rubber sample containing fillers, perform terahertz detection within a preset frequency range and obtain a corresponding sample terahertz spectrum signal, and then determine the absorption coefficient based on the sample terahertz spectrum signal. The terahertz detection platform used for terahertz detection in this step has the same structure and function as the terahertz detection platform in step 102, and will not be repeated here. The preset frequency range is 0thz-3thz.

[0059] After obtaining the sample terahertz spectrum signal, the process of determining the absorption coefficient is the same as step 103, which will not be repeated here.

[0060] (3) Determine a characteristic absorption peak and a frequency value corresponding to the characteristic absorption peak according to the absorption coefficients corresponding to the plurality of silicone rubber samples containing fillers; the frequency value corresponding to the characteristic absorption peak is a preset frequency value.

[0061] Figure 3 The refractive index comparison chart of several silicone rubber samples containing fillers is shown below. Figure 4This is a comparison of the terahertz time-domain electric field signals of multiple silicone rubber samples containing fillers. Combining the two figures, it can be seen that the waveforms of the terahertz time-domain signals of samples with different filler contents are very similar. As the filler content increases, the propagation speed of the terahertz signal in the medium will slow down, and the sample terahertz signal will lag. At the same time, the factors affecting the terahertz time-domain signal are also the thickness of the sample. As the filler content increases, the propagation speed of the terahertz signal in the medium is affected. According to the calculation and comparison of the refractive index, it can be seen that the amount of filler added will affect the refractive index of the sample, thereby affecting the propagation speed of the electromagnetic signal in the medium.

[0062] Figure 5 This is a comparison chart of the absorption rates of several silicone rubber samples containing fillers and the substances in the samples. Figure 5 It can be seen that the absorption rate of various components in the silicone rubber sample at 0thz-3thz, the material PDMS has no obvious absorption peak, and the absorption rate increases only around 1.26. White carbon black is an approximate straight line at this frequency, and has little effect on the absorption characteristic peak of the silicone rubber sample. The characteristic peak of the silicone rubber sample is only contributed by aluminum hydroxide. It can be found that after 1.26thz, the absorption of PDMS shows a downward trend. After the superposition of the absorption of aluminum hydroxide and white carbon black, the overall absorption of silicone rubber tends to be stable.

[0063] The absorption characteristic peaks of silicone rubber samples at 0thz-3thz frequencies were selected for research, and it was found that characteristic absorption peaks appeared at 1.21thz and 1.33thz, which were used as characteristic frequencies for analyzing the filler content of silicone rubber. That is, the preset frequency value is 1.21thz or 1.33thz.

[0064] The reason for the appearance of the above absorption characteristic peaks is that the aluminum hydroxide molecules and the aluminum hydroxide molecules and other substances have mutual forces. Aluminum hydroxide is called gibbsite, which is composed of Al atoms as the center and the upper and lower hydrogen and oxygen atoms combined into an octahedron. The gap position in each octahedron is Al. 3+ The upper and lower positions are occupied by hydroxyl groups, forming a layered structure, and the connection between atoms in each layer is achieved by hydrogen bonds. The hydroxyl groups in the molecular layer are divided into free hydroxyl groups and hydrated hydroxyl groups, and the distance between the layers is affected by external pressure, temperature and other factors.

[0065] (4) According to the filler content in the plurality of silicone rubber samples containing fillers and the absorption coefficient corresponding to the characteristic absorption peak, a linear regression process is performed and the obtained regression equation is marked as a preset absorption coefficient-filler content function.

[0066] Figure 6 This is a comparison chart of multiple silicone rubber samples containing fillers at the 1.21thz characteristic absorption peak. Figure 7 It is a linear diagram of the 1.21thz characteristic absorption peak and filler content; Figure 8 This is a comparison chart of multiple silicone rubber samples containing fillers at the 1.33thz characteristic absorption peak. Fig. 9 This is a linear diagram of the 1.33thz characteristic absorption peak and filler content.

[0067] The absorption characteristic peaks in the frequency range of 0thz-3thz are mainly generated by the stretching vibration of hydroxyl groups. At the same time, the vibration peaks of hydrogen bonds are also in the terahertz band. The absorption peak frequency of free hydroxyl groups is higher than that of hydrated hydroxyl groups. For silicone rubber, the aluminum hydroxide filler content will directly affect the peak value of this characteristic peak. Figure 6-Figure 9 It can be seen that with the increase of aluminum hydroxide content, the absorption rate of silicone rubber decreases, forming a good linear relationship. The corresponding functional relationship can be obtained through linear regression to facilitate subsequent calculations and applications.

[0068] In summary, the present application changes the content of each filler in silicone rubber to produce multiple silicone rubber samples. Under the detection of the terahertz detection platform, the terahertz time-domain electric field signal is obtained, the refractive index and absorptivity of the sample are obtained by calculation, the refractive index of the sample with different filler contents is verified, and the characteristic peak of the terahertz absorptivity of the sample is analyzed at the same time, the interference of PDMS and white carbon black is eliminated, and the relationship between the aluminum content and the absorptivity is obtained; it is also obtained that: according to the different silicone rubber fillers, the terahertz time-domain signal of the sample forms a lagging feature, the more fillers are added, the later the time domain characteristic peak appears, and the higher the refractive index of the sample; it is also obtained that: in the range of 0thz-3thz, the terahertz absorption characteristic frequency of silicone rubber appears at 1.21thz and 1.33thz, and at this characteristic frequency, the content of aluminum hydroxide added is inversely proportional to the peak value of the absorption peak.

[0069] The technical features of the above embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0070] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A method for detecting filler content in composite insulator silicone rubber, characterized in that: The method for detecting filler content in composite insulator silicone rubber comprises: Obtaining target composite insulator silicone rubber; Based on the preset frequency value, a terahertz detection platform is used to perform terahertz detection on the target composite insulator silicone rubber to obtain a terahertz spectrum signal; Determining an absorption coefficient based on the terahertz spectral signal; Based on a preset absorption coefficient-filler content function, determining the filler content corresponding to the target composite insulator silicone rubber according to the absorption coefficient; The preset frequency value and the preset absorption coefficient-filler content function are determined after performing terahertz detection on a plurality of silicone rubber samples containing fillers and performing statistical analysis on the terahertz spectrum signals obtained by the detection.

2. The method for detecting filler content in composite insulator silicone rubber according to claim 1, characterized in that: The process of determining the preset frequency value and the preset absorption coefficient-filler content function includes: Obtain multiple samples of silicone rubber containing fillers; For any silicone rubber sample containing fillers, terahertz detection is performed within a preset frequency range to obtain a corresponding sample terahertz spectrum signal, and then the absorption coefficient is determined based on the sample terahertz spectrum signal; Determine a characteristic absorption peak and a frequency value corresponding to the characteristic absorption peak according to the absorption coefficients corresponding to the plurality of silicone rubber samples containing fillers; the frequency value corresponding to the characteristic absorption peak is a preset frequency value; According to the filler content in a plurality of silicone rubber samples containing fillers and the absorption coefficient corresponding to the characteristic absorption peak, a linear regression process is performed and the obtained regression equation is marked as a preset absorption coefficient-filler content function.

3. The method for detecting filler content in composite insulator silicone rubber according to claim 2, characterized in that: When the preset frequency range is 0thz-3thz, the preset frequency value is 1.21thz or 1.33thz.

4. The method for detecting filler content in composite insulator silicone rubber according to claim 1, characterized in that: Determining an absorption coefficient based on the terahertz spectrum signal includes: Performing Fourier transform on the terahertz spectrum signal to obtain a terahertz frequency domain signal; Determining the refractive index and extinction coefficient of the target composite insulator silicone rubber based on the terahertz frequency domain signal; Based on Lambert's law, the absorption coefficient is determined from the extinction coefficient.

5. The method for detecting filler content in composite insulator silicone rubber according to claim 4, characterized in that: The calculation formula of the refractive index is: The calculation formula of the extinction coefficient is: Where n(ω) is the refractive index, k(ω) is the extinction coefficient, is the phase of the terahertz frequency domain signal, c is the speed of light, ω is the frequency of the terahertz wave, d is the thickness of the target composite insulator silicone rubber, and ρ(ω) is the propagation coefficient.

6. The method for detecting filler content in composite insulator silicone rubber according to claim 4, characterized in that: The calculation formula of the absorption coefficient is: Among them, α(ω) is the absorption coefficient, c is the speed of light, and k(ω) is the extinction coefficient.

7. The method for detecting filler content in composite insulator silicone rubber according to claim 1, characterized in that: The terahertz detection platform includes a femtosecond pulse laser, a beam splitter, a terahertz detection branch, a material scanning platform, a terahertz detector, a lock-in amplifier and a terminal; The material scanning platform is used to carry the target composite insulator silicone rubber; The femtosecond pulse laser is used to generate pulsed laser and send it to the beam splitter; The beam splitter is used to split the received laser into two laser beams, and send one of the beams to the terahertz detection branch, and send the other beam to the terahertz detector; The terahertz detection branch is used to generate a terahertz pulse of the preset frequency value according to the received laser excitation, and irradiate and penetrate the target composite insulator silicone rubber to reach the terahertz detector; The terahertz detector is used to determine a terahertz spectrum signal according to the received laser, and then send the terahertz spectrum signal to the terminal via the lock-in amplifier; The terminal is used to store the terahertz spectrum signal.

8. The method for detecting filler content in composite insulator silicone rubber according to claim 7, characterized in that: The terahertz detection branch comprises a time delay optical path and a terahertz emitter which are arranged in sequence.

9. The method for detecting filler content in composite insulator silicone rubber according to claim 7, characterized in that: The power of the laser emitted by the beam splitter to the terahertz detection branch is higher than the power of the laser emitted by the beam splitter to the terahertz detector.

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