阅读说明：本技术 基于太赫兹介电谱的橡胶材料老化状态判别系统及方法 (Rubber material aging state discrimination system and method based on terahertz dielectric spectrum ) 是由 张献生 常天英 刘陵玉 李羿璋 崔洪亮 于 2020-07-15 设计创作，主要内容包括：本公开提供了一种基于太赫兹介电谱的橡胶材料老化状态判别系统,属于橡胶材料老化判断技术领域,包括太赫兹时域光谱仪,太赫兹时域光谱仪的发射透镜天线和接收透镜天线均设置在密闭箱体中,待测样品设置在发射透镜天线和接收透镜天线的焦点处,且待测样品表面与太赫兹传输路径垂直；本公开保证了对测试样品的非接触无损测量,样品材料要求低、操作方便、测量频率宽、精确度高、测量的值波动范围小,在塑料、橡胶等绝缘材料中的老化检测中优势突出。(The system comprises a terahertz time-domain spectrograph, wherein a transmitting lens antenna and a receiving lens antenna of the terahertz time-domain spectrograph are both arranged in a closed box body, a sample to be detected is arranged at the focus of the transmitting lens antenna and the receiving lens antenna, and the surface of the sample to be detected is vertical to a terahertz transmission path; the method ensures non-contact nondestructive measurement of a test sample, has low sample material requirement, convenient operation, wide measurement frequency, high precision and small measurement value fluctuation range, and has outstanding advantages in aging detection of insulating materials such as plastics, rubber and the like.)

1. A rubber material aging state distinguishing system based on a terahertz dielectric spectrum is characterized by comprising a terahertz time-domain spectrometer, wherein a transmitting lens antenna and a receiving lens antenna of the terahertz time-domain spectrometer are both arranged in a closed box body;

the sample to be measured is arranged at the focus of the transmitting lens antenna and the receiving lens antenna, and the surface of the sample to be measured is vertical to the terahertz transmission path.

2. The system for discriminating the aging state of a rubber material based on terahertz dielectric spectroscopy as defined in claim 1, wherein the sample to be measured is flat.

3. The system for discriminating the aging state of a rubber material based on terahertz dielectric spectroscopy as defined in claim 2, wherein the thickness of the sample to be measured ranges from 0.1mm to 10 mm.

4. The system for discriminating the aging state of a rubber material based on terahertz dielectric spectroscopy as defined in claim 2, wherein the light receiving area of the sample to be measured is greater than or equal to 5 square millimeters.

5. The system for discriminating the aging state of a rubber material based on terahertz dielectric spectroscopy as defined in claim 2, wherein the sample to be measured is held by a sample, and both the sample to be measured and the sample holder are also provided in the airtight box.

6. A method for discriminating an aging state of a rubber material based on a terahertz dielectric spectrum, which is characterized by using the discrimination system of any one of claims 1 to 5, and comprises the following steps:

filling nitrogen or dry air in the closed box body;

when no sample exists, testing the complex refractive index of the air with the same thickness as that of the sample to be tested, and calibrating and measuring a reference value of the system;

testing the complex refractive index of a sample by using a terahertz time-domain spectrometer, wherein the complex refractive index at least comprises a real part of the refractive index and an extinction coefficient;

calculating dielectric spectrum data of the material according to the relation between the dielectric constant and the refractive index;

and obtaining the dielectric strength and the resonance effect of the material by fitting a function based on the obtained dielectric spectrum data.

7. The method for discriminating the aging state of a rubber material based on terahertz dielectric spectrum according to claim 6, wherein the dielectric spectrum data at least comprises a real part and an imaginary part of a dielectric spectrum, the real part of the dielectric spectrum is a difference value between a square of the real part of the refractive index and a square of the extinction coefficient, and the imaginary part of the dielectric spectrum is twice a product of the real part of the refractive index and the extinction coefficient;

alternatively, the first and second electrodes may be,

the terahertz emitted by the spectrometer is divided into two paths, one path of terahertz passes through the delayer and is input to the receiving end as a comparison signal as probe light, the other path of pump light is directly transmitted to the transmitting end and acts on a sample, and the signal is received by the receiving end after penetrating through the sample and is compared and calculated with the probe light.

8. The method for judging the aging state of a rubber material based on the terahertz dielectric spectrum as claimed in claim 6, wherein the fitting function is specifically as follows: and the sum of the dielectric constant of the sample to be tested under the infinite frequency, the dielectric function under a Debye relaxation motion model and the dielectric functions under m Lorentz resonance models.

9. The method for discriminating the aging state of a rubber material based on terahertz dielectric spectroscopy as defined in claim 8, wherein the fitting function employs a constraint condition that an error between a fitting curve and a test curve is minimum.

10. The method for discriminating the aging state of a rubber material based on terahertz dielectric spectroscopy as claimed in claim 8, wherein the parameters obtained by fitting are a zero-frequency dielectric constant, a dielectric constant at an infinite frequency, a dielectric strength and a resonance frequency;

the zero-frequency dielectric constant represents the macroscopic comprehensive dielectric property of the material and comprises dielectric properties caused by relaxation type polarization and resonance type polarization, the dielectric constant at infinite frequency represents a macroscopic dielectric value caused by resonance type polarization, the dielectric strength represents a dielectric variable caused by change of a microscopic polar structure in the material, and the resonance frequency represents a resonance effect generated by the whole change of a molecular chain and the crystallization degree.

Technical Field

The disclosure relates to the technical field of rubber material aging judgment, in particular to a system and a method for judging the aging state of a rubber material based on terahertz dielectric spectroscopy.

Background

The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art.

The rubber product has excellent material performance, is visible everywhere in social life, aging is physical and chemical changes which gradually occur in the using or storing process of the rubber product due to the comprehensive influence of internal and external factors, such as surface stickiness or hardening, deformation, color change and the like in appearance, aging is a slow and complex chemical reaction process, and finally the application performance of the rubber product is greatly reduced and becomes a main source of potential safety hazard. The essence of aging is the molecular chain cleavage or cross-linking of the material under the influence of external factors such as light, temperature, humidity, chemical media and microbial contamination, and the molecular weight and distribution thereof induced thereby, the stereoregularity of the material and the chemical structure of the material are changed.

Dielectric spectroscopy is another expression of a physical quantity, i.e., a dielectric constant, of a substance to be measured when the complex dielectric constant (also called complex permittivity) depends on the frequency of an electromagnetic wave or temperature. The dielectric spectroscopy method is a method for studying the interaction between a substance and an electromagnetic wave, and the main parameters are complex dielectric constant, complex conductivity, loss tangent and the like.

The inventor of the present disclosure finds that, in a microwave band with a lower frequency band, the state of an insulating material after aging is judged by using the changes of dielectric constant and loss tangent in a certain frequency band based on a dielectric spectrum technology, and meanwhile, the evolution process of a polar structure in the material is analyzed by fitting a Debye equation, so that the dielectric spectrum technology has great potential and value in field detection application as a spectrum analysis technology of nondestructive detection; but the microwave low-frequency band has the defects of narrow bandwidth, large fluctuation range of measured values and the like, and the material structure change is difficult to realize fine analysis.

Disclosure of Invention

In order to solve the defects of the prior art, the invention provides a system and a method for judging the aging state of a rubber material based on a terahertz dielectric spectrum, which ensure the non-contact nondestructive measurement of a test sample, have low requirement on the sample material, convenient operation, wide measurement frequency, high accuracy and small fluctuation range of the measured value, and have outstanding advantages in the aging detection of insulating materials such as plastics, rubber and the like.

In order to achieve the purpose, the following technical scheme is adopted in the disclosure:

the first aspect of the disclosure provides a rubber material aging state discrimination system based on terahertz dielectric spectroscopy.

A rubber material aging state distinguishing system based on terahertz dielectric spectroscopy comprises a terahertz time-domain spectrometer, wherein a transmitting lens antenna and a receiving lens antenna of the terahertz time-domain spectrometer are both arranged in a closed box body;

the sample to be measured is arranged at the focus of the transmitting lens antenna and the receiving lens antenna, and the surface of the sample to be measured is vertical to the terahertz transmission path.

The second aspect of the disclosure provides a method for judging the aging state of a rubber material based on terahertz dielectric spectroscopy.

A method for judging the aging state of a rubber material based on terahertz dielectric spectroscopy utilizes a judging system of the first aspect of the disclosure, and comprises the following steps:

filling nitrogen or dry air in the closed box body;

when no sample exists, testing the complex refractive index of the air with the same thickness as that of the sample to be tested, and calibrating and measuring a reference value of the system;

testing the complex refractive index of a sample by using a terahertz time-domain spectrometer, wherein the complex refractive index at least comprises a real part of the refractive index and an extinction coefficient;

calculating dielectric spectrum data of the material according to the relation between the dielectric constant and the refractive index;

and obtaining the dielectric strength and the resonance effect of the material by fitting a function based on the obtained dielectric spectrum data.

Compared with the prior art, the beneficial effect of this disclosure is:

1. the system and the method disclosed by the disclosure are characterized in that a terahertz time-domain spectroscopy (THz-TDS) is used for testing the complex refractive index of an aged sample, corresponding dielectric spectrum parameters are calculated through a refractive index and dielectric constant calculation formula, several dielectric parameters capable of judging the molecular structure change of a material are calculated through a fitting algorithm, and the aging state judgment and the aging time correlation of the material are realized through comparison with the dielectric parameter values of the unaged material.

2. The system and the method disclosed by the disclosure realize the detection and judgment of the aging of the rubber product through a certain fitting algorithm, can qualitatively analyze the change process of the microstructure of the material, ensure the non-contact nondestructive measurement of a test sample, have low requirement on the material of the sample, are convenient to operate, have wide measurement frequency and high accuracy, and have advantages in the aging detection of insulating materials such as plastics, rubber and the like.

3. The system and the method have the advantages of simple and easy operation of equipment, higher test precision, and the tested frequency bandwidth reaching THz (10)¹²Hz), can represent smaller variation trend in a wide frequency band, has low manufacturing requirement on the sample, and only needs to make the sample into a flat plate shape; the calculation method is quick, can be integrated, has low application environment requirement, and can test a wide variety of samples.

Drawings

The accompanying drawings, which are included to provide a further understanding of the disclosure, illustrate embodiments of the disclosure and together with the description serve to explain the disclosure and are not to limit the disclosure.

Fig. 1 is a schematic structural diagram of a rubber material aging state discrimination system based on terahertz dielectric spectroscopy provided in embodiment 1 of the present disclosure.

Fig. 2 is a schematic flow chart of a fitting algorithm provided in embodiment 2 of the present disclosure.

FIG. 3 is a schematic diagram illustrating an example of a process of calculating a dielectric parameter of a rubber article in a thermal oxidation aging process according to example 2 of the present disclosure.

1. A terahertz time-domain spectrometer; 2. sealing the box body; 3. a sample holder; 4. a dryer or nitrogen tank; 5. dry air or nitrogen; 6. a computer; 7. and (5) testing the sample to be tested.

Detailed Description

The present disclosure is further described with reference to the following drawings and examples.

It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

The embodiments and features of the embodiments in the present disclosure may be combined with each other without conflict.

As described in the background art, the microwave low-frequency band has the defects of narrow bandwidth, large fluctuation range of measured values, and the like, and it is difficult to realize fine analysis on the structural change of the material. Compared with microwave, the terahertz frequency band is improved by several orders of magnitude in bandwidth, sensitive to the change of the microstructure of the material and more suitable for the change of a fine structure than the microwave. THz-TDS is not influenced by uncertainty of Krams-Kronig analysis in the traditional far infrared spectrum, and becomes a powerful tool for the experimental characterization of parameters of the terahertz complex dielectric spectrum of the polymer.