Apparatus and method for detecting glass transition temperature of a polymer material using ultrasonic waves

Abstract

The application discloses a device and method for detecting the glass transition temperature of a polymer material by using ultrasonic waves, and the device comprises a signal acquisition module and a signal processing module, wherein the signal acquisition module comprises a temperature rising assembly, a fixing assembly and a detection assembly; the fixing assembly is installed in the temperature rising assembly and is used for fixing the detection assembly and a test block; the test block is a polymer material, and the detection assembly comprises a probe; during the detection, the temperature rising assembly is heated and kept warm, the probe can be relatively moved with the test block in the Z-axis direction of the fixing assembly, the probe excites and receives the ultrasonic waves returned by the test block, the signal processing module collects and analyzes the ultrasonic waves returned by the test block and received by the probe at different time stages, and the glass transition temperature of the polymer material is indicated. The application realizes the low-cost, high-efficiency and accurate detection of the glass transition temperature of the polymer material and has the engineering practical significance.

Description

Technical Field

[0001] This invention belongs to the field of polymer material testing, and specifically relates to an apparatus and method for detecting the glass transition temperature of polymer materials using ultrasonic waves. Background Technology

[0002] Polymer materials play a vital role in various fields, but the glass transition directly impacts their performance and processing capabilities. At the glass transition temperature, the microstructure and properties of polymer materials undergo drastic changes. Below the glass transition temperature, the polymer is a plastic; above it, it is a rubber. From an engineering perspective, the glass transition temperature represents the upper limit of the operating temperature for engineering plastics and the lower limit for rubber or elastomers. Therefore, the glass transition temperature directly affects the thermal properties of polymer materials and is a crucial parameter for evaluating their stability and reliability at high temperatures.

[0003] Detecting the glass transition temperature (Tg) of polymer materials has long been a major focus of polymer physics research. Differential scanning calorimetry (DSC), thermomechanical analysis (TMA), and dynamic thermomechanical analysis (TMA) are three measurement methods that have been studied in depth. For example, patent CN113670471A discloses a method for detecting the Tg of a glass transition temperature based on a drawn-tower grating coating. This method selects either a first or second coating testing method based on the known range of the Tg of the coating to be tested, and then performs the test using a glass transition temperature testing device based on a drawn-tower grating coating. This approach first preliminarily classifies the known range of the coating to be tested, then adaptively selects the first and second coating testing methods. Combined with the glass transition temperature testing device based on a drawn-tower grating coating, it achieves accurate testing of the Tg of coatings with both high and low Tg, without requiring special treatment of the grating coating sample, making the testing method simple.

[0004] However, existing methods for detecting the glass transition temperature of polymers generally suffer from problems such as expensive equipment, cumbersome operation, and limited versatility, thus limiting their application in industrial settings. Currently, they are mostly used in laboratory research or quality control of advanced fields such as aerospace materials. There is a lack of efficient, low-cost testing methods to meet the large-scale testing needs of polymer materials in civilian, commercial, and other industrial sectors.

[0005] Therefore, how to design accurate and reliable detection devices and methods for the glass transition temperature of polymer materials to meet the needs of low-cost, high-volume, and industrialized polymer material testing is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides an apparatus and method for detecting the glass transition temperature of polymer materials using ultrasound. The apparatus includes a signal acquisition module and a signal processing module. In the signal acquisition module, a probe and a test block move relative to each other on a fixed assembly, acquiring and receiving ultrasonic signals from the polymer test block at different temperatures. These signals are then analyzed and characterized by the signal processing module to determine the glass transition temperature of the polymer material. Before and after the glass transition, the propagation process of ultrasound in the polymer material changes significantly due to variations in its microstructure and properties. This change is reflected in the acquired ultrasonic signals, with the most significant change being in the amplitude characteristics. Therefore, the extreme points of the ultrasonic amplitude can correspond to the starting point of the glass transition in the polymer material as temperature changes. The apparatus and method for detecting the glass transition temperature of polymer materials provided by this invention achieve low-cost, high-efficiency, and accurate detection of the glass transition temperature of polymer materials, which has practical engineering significance.

[0007] In a first aspect, the present invention provides an apparatus for detecting the glass transition temperature of a polymer material using ultrasound, comprising: The signal acquisition module and the signal processing module are included. The signal acquisition module includes a heating component, a fixing component, and a detection component. The fixing component is installed in the heating component and is used to fix the detection component and the test block. The test block is made of polymer material and the detection component includes a probe. During the testing process, the heating component heats and maintains the temperature, while the probe can move relative to the test block in the Z-axis direction of the fixed component. The probe excites and receives the ultrasonic waves returned by the test block, and the signal processing module collects and analyzes the ultrasonic waves returned by the test block at different time stages to characterize and give the glass transition temperature of the polymer material.

[0008] Furthermore, the fixing assembly includes a crossbeam, a mechanical cantilever, a first slide rail, a second slide rail, a probe clamp, and a test block clamp. The crossbeam is installed directly above the opening of the heating component. The first slide rail is set on the crossbeam and arranged in the X-axis direction. The mechanical cantilever is fixed in the Z-axis and Y-axis directions through the first slide rail and the crossbeam. The second slide rail is arranged in the Z-axis direction of the mechanical cantilever. The probe clamp and the test block clamp are both arranged and connected to the second slide rail. Both the probe clamp and the test block clamp can move in the Z-axis direction. The probe clamp is located above the test block clamp. The probe is mounted in the probe holder, the test block is mounted in the test block holder, the probe is located directly above the test block, the probe excites ultrasonic waves to the test block and receives the ultrasonic waves returned by the test block, and the ultrasonic waves emitted by the probe are perpendicular to the surface of the test block.

[0009] Furthermore, the movement of the sample clamp in the Z-axis direction is below the horizontal plane of the liquid medium inside the heating component, and includes a distance of 5mm-10mm from the vertical distance to the horizontal plane of the liquid medium inside the heating component. The movement of the probe clamp in the negative Z-axis direction at least causes the probe to contact the sample, and the movement of the probe clamp in the positive Z-axis direction at least causes the probe to be above the horizontal plane of the liquid medium inside the heating component.

[0010] Furthermore, a heat-insulating wedge is installed at the bottom of the probe, and a coupling agent is added between the wafer and the wedge inside the probe to achieve ultrasonic signal transmission.

[0011] Secondly, the present invention also provides a method for detecting the glass transition temperature of a polymer material using ultrasound, utilizing the apparatus described above for detecting the glass transition temperature of a polymer material using ultrasound, comprising the following steps: S1: Debug the probe using a standard block and calibrate the signal processing module; S2: Install the fixing component and the heating component, and fix the detection component to the fixing component; S3: At the initial liquid medium temperature, move the probe along the negative Z-axis until the probe contacts the test block, and adjust the ultrasonic detection gain so that the amplitude of the first echo on the bottom surface of the test block reaches the preset threshold. S4: Move the probe along the positive Z-axis until the probe is higher than the horizontal surface of the liquid medium inside the heating component, and the heating component heats the liquid medium. S5: After the liquid medium temperature reaches the target temperature, move the probe along the negative Z-axis until the probe contacts the test block. The probe then generates ultrasonic waves, receives the ultrasonic waves returned by the test block, and transmits them to the signal processing module. S6: Repeat steps S4-S5 above at all target temperatures of the liquid medium in the heating component, and the probe completes the reception of the ultrasonic waves returned by the test block and the transmission to the signal processing module. S7: The signal processing module analyzes the ultrasonic waves returned by the test block at each target temperature to complete the detection of the glass transition temperature of the polymer material.

[0012] Furthermore, the preset threshold is 80%~90%, and the target temperature is 0.5℃~1℃ of the temperature difference between the current liquid medium and the previous temperature.

[0013] Furthermore, the probe is debugged using standard blocks, and the signal processing module is calibrated, specifically through the following steps: The probe excites and receives ultrasound on the standard block at all target temperatures to obtain the corresponding first initial amplitude. All the obtained first initial amplitude values ​​are processed to obtain the corresponding first amplitude values; The relationship between the first magnitude and the first initial magnitude is as follows: ; Among them, h n h is the first initial amplitude at temperature n. max h is the largest initial amplitude among all target temperatures. n ' is the first amplitude at temperature n.

[0014] Furthermore, the signal processing module analyzes the ultrasonic waves returned by the test blocks at various target temperatures, specifically including the following steps: The ultrasonic waves returned by the receiving test block are transformed to obtain the second initial amplitude of the signal envelope; The second initial amplitude is processed to obtain the second amplitude; By combining the first amplitude value corresponding to the temperature, the second amplitude value is corrected to obtain the first bottom wave amplitude value; The glass transition temperature of the sample is given by the rule of variation between the amplitude of the first wave and the target temperature.

[0015] Furthermore, the ultrasonic waves returned by the receiving test block are transformed to obtain a second initial amplitude of the signal envelope, specifically including: Perform a discrete Fourier transform on the ultrasonic signal returned by the receiving test block to obtain the transformed signal D(i), i=0,1,2,...,M-1; Performing a Z-transform on D(i) yields the following relationship: ; Perform an inverse Fourier transform on Z(i) to obtain the signal z(m); Based on the signal z(m), the second initial amplitude of the signal envelope is calculated, and the calculation relationship is as follows: ; Where M is the number of discrete points of the ultrasonic signal returned by the receiving test block, and I m Let x(m) be the second initial amplitude obtained by transforming the ultrasonic signals returned from the receiving test blocks at M discrete points, and let z(m) be the real part of z(m). Let z(m) be the imaginary part.

[0016] Furthermore, the relationship between the second amplitude and the second initial amplitude is as follows: ; The relationship between the first initial amplitude and the first and second initial amplitudes is as follows: ; Among them, I n I is the second initial amplitude at temperature n. max k is the second largest initial amplitude among all target temperatures. n Let be the amplitude of the first bottom wave at temperature n.

[0017] The present invention provides an apparatus and method for detecting the glass transition temperature of polymer materials using ultrasound, which has at least the following beneficial effects: (1) The probe and the test block in the signal acquisition module move relative to each other on the fixed component to acquire and receive ultrasonic signals of polymer test blocks at different temperatures. After analysis and characterization by the signal processing module, the glass transition temperature of the polymer material is given. This realizes low-cost, high-efficiency and accurate detection of the glass transition temperature of polymer materials, which has practical engineering significance and great market application prospects and promotion value.

[0018] (2) The device for detecting the glass transition temperature of polymer materials by ultrasonic testing is more cost-effective and easier to operate than traditional glass transition temperature testing equipment. It can also achieve automated control, and the measurement results are accurate. It is easy to use in batches and industrial applications and has universality.

[0019] (3) The method of ultrasonic testing of glass transition temperature of polymer materials, combined with ultrasonic signal processing and analysis technology, realizes the integrated operation of acquisition, processing and control, and improves the efficiency and accuracy of glass transition temperature testing of polymer materials. Attached Figure Description

[0020] Figure 1 A front view of a device for detecting the glass transition temperature of polymer materials using ultrasonic waves, provided by the present invention; Figure 2 A top view of an apparatus for detecting the glass transition temperature of polymer materials using ultrasonic waves, provided by the present invention. Figure 3 This invention provides a flowchart of a method for detecting the glass transition temperature of polymer materials using ultrasonic waves; Figure 4 A flowchart of a method for analyzing ultrasound using a signal processing module provided by the present invention; Figure 5 A graph showing the variation of the amplitude of a primary wave with the target temperature in a certain embodiment of the present invention.

[0021] Explanation of reference numerals in the attached figures: 1-Heating component, 2-Crossbeam, 3-First slide rail, 4-Mechanical cantilever, 5-Probe clamp, 6-Probe, 7-Test block clamp, 8-Test block, 9-Second slide rail. Detailed Implementation

[0022] To better understand the above technical solutions, a detailed description of the solutions will be provided below in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0023] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms, and “multiple” generally includes at least two unless the context clearly indicates otherwise.

[0024] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device that includes said element.

[0025] Before and after the glass transition temperature of a polymer material, the propagation process of ultrasound in the polymer material changes significantly due to changes in its microstructure and properties. This change is reflected in the acquired ultrasound signals, with the most significant change being in the amplitude characteristics of the ultrasound. Therefore, with temperature changes, the extreme points of the ultrasound amplitude can correspond to the starting point of the glass transition of the polymer material. This invention provides a device for detecting the glass transition temperature of a polymer material using ultrasound, comprising: a signal acquisition module and a signal processing module (not shown in the figure). The signal acquisition module includes a heating component 1, a fixing component, and a detection component. The polymer material is placed in the heating component 1 and is heated and kept at a constant temperature as the temperature of the heating component increases. The fixing component is installed in the heating component 1 to fix the detection component, and the detection component can move along the Z-axis direction during the detection process on the fixing component. The detection component includes a probe 6 and a test block 8 made of polymer material. The probe 6 and the test block 8 can move relative to each other in the Z-axis direction. The probe 6 excites ultrasound and receives the ultrasound returned by the test block 8. The signal processing module acquires and analyzes the ultrasonic waves returned from test block 8 by the detection component at different time stages, characterizing and providing the glass transition temperature of the polymer material. The signal processing module can select a host computer for acquiring and analyzing ultrasonic signals.

[0026] like Figure 1 and Figure 2As shown, the fixing assembly includes a crossbeam 2, a mechanical cantilever 4, a first slide rail 3, a second slide rail 9, a probe clamp 5, and a test block clamp 7. The crossbeam 2 is installed directly above the opening of the heating assembly 1. The first slide rail 3 is set on the crossbeam 2 and arranged in the X-axis direction. The mechanical cantilever 4 is fixed to the crossbeam 2 in the Z-axis and Y-axis directions through the first slide rail 3. The second slide rail 9 is arranged in the Z-axis direction of the mechanical cantilever 4. The probe clamp 5 and the test block clamp 7 are both arranged and connected to the second slide rail 9. Both the probe clamp 5 and the test block clamp 7 can move in the Z-axis direction. The probe clamp 5 is located above the test block clamp 7. The probe 6 is mounted on the probe holder 5, and the test block 8 is mounted on the test block holder 7. The probe 6 is located directly above the test block 8. The probe 6 excites ultrasonic waves to the test block 8 and receives the ultrasonic waves returned by the test block 8. The ultrasonic waves emitted by the probe 6 are perpendicular to the surface of the test block 8.

[0027] The heating component 1 can be a square water bath, wherein the Z-axis direction is perpendicular to the horizontal plane of the liquid medium in the heating component 1, and the plane formed by the X-axis and Y-axis directions is parallel to the horizontal plane of the liquid medium.

[0028] The movement of the test block clamp 7 in the Z-axis direction is below the horizontal plane of the liquid medium inside the heating assembly 1, including a distance of 5mm-10mm from the vertical distance to the horizontal plane of the liquid medium inside the heating assembly 1. The movement of the probe clamp 5 in the negative Z-axis direction at least ensures that the probe 6 contacts the sample, and the movement of the probe clamp 5 in the positive Z-axis direction at least ensures that the probe 6 is above the horizontal plane of the liquid medium inside the heating assembly 1. The dimensions of the crossbeam 2 and the mechanical cantilever 4 are designed to suit the dimensions and positions of the test block clamp 7 and the probe clamp 5; specific dimensional values ​​are not specifically limited here.

[0029] A heat-insulating wedge (not shown in the figure) is installed at the bottom of the probe 6, and a coupling agent is added between the wafer (not shown in the figure) inside the probe 6 and the wedge to achieve ultrasonic signal transmission.

[0030] The device for detecting the glass transition temperature of polymer materials using ultrasound is more cost-effective and easier to operate than traditional glass transition temperature detection equipment. It can also achieve automated control, provides accurate measurement results, and is suitable for batch and industrial applications, making it universally applicable.

[0031] like Figure 3 As shown, the present invention also provides a method for detecting the glass transition temperature of polymer materials using ultrasound, wherein the ultrasonic signal is acquired by immersion in a liquid medium using ultrasound, and the method utilizes the apparatus described above for detecting the glass transition temperature of polymer materials using ultrasound, comprising the following steps: S1: Debug the probe using a standard block and calibrate the signal processing module; S2: Install the fixing component and the heating component, and fix the detection component to the fixing component; S3: At the initial liquid medium temperature, move the probe along the negative Z-axis until the probe contacts the test block, and adjust the ultrasonic detection gain so that the amplitude of the first echo on the bottom surface of the test block reaches the preset threshold. S4: Move the probe along the positive Z-axis until the probe is higher than the horizontal surface of the liquid medium inside the heating component, and the heating component heats the liquid medium. S5: After the liquid medium temperature reaches the target temperature, move the probe along the negative Z-axis until the probe contacts the test block. The probe then generates ultrasonic waves, receives the ultrasonic waves returned by the test block, and transmits them to the signal processing module. S6: Repeat steps S4-S5 above at all target temperatures of the liquid medium in the heating component, and the probe completes the reception of the ultrasonic waves returned by the test block and the transmission to the signal processing module. S7: The signal processing module analyzes the ultrasonic waves returned by the test block at each target temperature to complete the detection of the glass transition temperature of the polymer material.

[0032] By employing ultrasonic testing to detect the glass transition temperature of polymer materials, and combining ultrasonic signal processing and analysis techniques, an integrated operation of acquisition, processing, and control has been achieved, improving the efficiency and accuracy of glass transition temperature detection for polymer materials.

[0033] The preset threshold is 80%~90%, and the target temperature is 0.5℃~1℃ higher than the previous liquid medium temperature difference. The preset threshold for the echo amplitude is to ensure that the amplitude of the echo is approximately at 80%~90% of the screen height. The initial liquid medium temperature is generally room temperature, i.e., 20℃, but it can be preset according to the differences in polymer materials and application scenarios; no specific limitation is made here. The target temperature is 0.5℃~1℃ higher than the previous liquid medium temperature difference, meaning that in step S6, the target temperature for each cycle is any value between 0.5℃ and 1℃ higher than the previous target temperature. The difference in target temperature is determined based on various factors such as the recognition accuracy of ultrasound on the polymer material's microstructure and properties, the error in ultrasound acquisition and analysis, and the accuracy of the polymer material's glass transition temperature. Values ​​such as 0.5℃, 0.8℃, and 1℃ can be selected; no further limitation is made on the specific value here.

[0034] The probe is debugged using a standard block, and the signal processing module is calibrated, specifically through the following steps: The probe excites and receives ultrasound on the standard block at all target temperatures to obtain the corresponding first initial amplitude. All the obtained first initial amplitude values ​​are processed to obtain the corresponding first amplitude values; The relationship between the first magnitude and the first initial magnitude is as follows: ; Among them, hn h is the first initial amplitude at temperature n. max h is the largest initial amplitude among all target temperatures. n ' is the first amplitude at temperature n.

[0035] The signal processing module analyzes the ultrasonic waves returned by the test blocks at various target temperatures, specifically including the following steps: like Figure 4 As shown, the ultrasonic waves returned by the receiving test block are transformed to obtain the second initial amplitude of the signal envelope; The second initial amplitude is processed to obtain the second amplitude; By combining the first amplitude value corresponding to the temperature, the second amplitude value is corrected to obtain the first bottom wave amplitude value; The glass transition temperature of the sample is given by the rule of variation between the amplitude of the first wave and the target temperature.

[0036] Furthermore, the ultrasonic waves returned by the receiving test block are transformed to obtain a second initial amplitude of the signal envelope, specifically including: Perform a discrete Fourier transform on the ultrasonic signal returned by the receiving test block to obtain the transformed signal D(i), i=0,1,2,...,M-1; Performing a Z-transform on D(i) yields the following relationship: ; Perform an inverse Fourier transform on Z(i) to obtain the signal z(m); Based on the signal z(m), the second initial amplitude of the signal envelope is calculated, and the calculation relationship is as follows: ; Where M is the number of discrete points of the ultrasonic signal returned by the receiving test block, and I m Let x(m) be the second initial amplitude obtained by transforming the ultrasonic signals returned from the receiving test blocks at M discrete points, and let z(m) be the real part of z(m). Let z(m) be the imaginary part.

[0037] At this time, the ultrasonic signal received by the probe from the test block is the frequency modulation amplitude modulation signal (AM-FM signal), and the frequency modulation amplitude modulation signal is subjected to discrete Fourier transform.

[0038] Furthermore, the relationship between the second amplitude and the second initial amplitude is as follows: ; The relationship between the first initial amplitude and the first and second initial amplitudes is as follows: ; Among them, I nI is the second initial amplitude at temperature n. max k is the second largest initial amplitude among all target temperatures. n Let be the amplitude of the first bottom wave at temperature n. Example

[0039] In this embodiment, modified polypropylene (MPP) was selected as the polymer material specimen. The specific steps of the polymer material glass transition temperature characterization method based on ultrasonic amplitude change characteristics are as follows: S1: The probe is debugged using a standard block, and the signal processing module is calibrated; the probe excites and receives ultrasound from the standard block at all target temperatures to obtain the corresponding first initial amplitude. All the obtained first initial amplitude values ​​are processed to obtain the corresponding first amplitude values; The relationship between the first magnitude and the first initial magnitude is as follows: ; Among them, h n h is the first initial amplitude at temperature n. max h is the largest initial amplitude among all target temperatures. n ' is the first amplitude at temperature n.

[0040] S2: The fixing component and the heating component are installed, and the detection component is fixed to the fixing component; the crossbeam 2 is installed directly above the opening of the heating component 1, the first slide rail 3 is set on the crossbeam 2 and arranged in the X-axis direction, the mechanical cantilever 4 is fixed in the Z-axis and Y-axis directions by the first slide rail 3 and the crossbeam 2, the second slide rail 9 is arranged in the Z-axis direction of the mechanical cantilever 4, the probe clamp 5 and the test block clamp 7 are both arranged and connected to the second slide rail 9, the probe clamp 5 and the test block clamp 7 can both move in the Z-axis direction, the probe clamp 5 is located on the test block clamp 7 The probe 6 is mounted on the probe holder 5, and the test block 8 is mounted on the test block holder 7. The probe 6 is located directly above the test block 8. The ultrasonic wave emitted by the probe 6 is perpendicular to the surface of the test block 8. The movement of the test block holder 7 in the Z-axis direction is below the horizontal plane of the liquid medium inside the heating component 1, and includes a distance of 8 mm from the vertical distance of the horizontal plane of the liquid medium inside the heating component 1. The movement of the probe holder 5 in the negative Z-axis direction at least makes the probe 6 contact the sample, and the movement of the probe holder 5 in the positive Z-axis direction at least makes the probe 6 higher than the horizontal plane of the liquid medium inside the heating component 1.

[0041] S3: At the initial liquid medium temperature, move the probe along the negative Z-axis until the probe contacts the test block, and adjust the ultrasonic detection gain so that the amplitude of the first echo on the bottom surface of the test block reaches the preset threshold. The initial liquid medium temperature is room temperature, 20℃, and the preset threshold is 80%.

[0042] S4: Move the probe along the positive Z-axis until the probe is above the horizontal plane of the liquid medium inside the heating component, and the heating component heats the liquid medium.

[0043] S5: After the liquid medium temperature reaches the target temperature, move the probe along the negative Z-axis until the probe contacts the test block. The probe then generates ultrasonic waves, receives the ultrasonic waves returned by the test block, and transmits them to the signal processing module. The target temperature is 1℃ lower than the previous liquid medium temperature.

[0044] S6: Repeat steps S4-S5 above at all target temperatures of the liquid medium in the heating component, and the probe completes the reception of the ultrasonic waves returned by the test block and the transmission to the signal processing module.

[0045] S7: Perform a discrete Fourier transform on the ultrasonic signal returned by the receiving test block to obtain the transformed signal D(i), i=0, 1, 2, ..., M-1; Performing a Z-transform on D(i) yields the following relationship: ; Perform an inverse Fourier transform on Z(i) to obtain the signal z(m); Based on the signal z(m), the second initial amplitude of the signal envelope is calculated, and the calculation relationship is as follows: ; Where M is the number of discrete points of the ultrasonic signal returned by the receiving test block, and I m Let x(m) be the second initial amplitude obtained by transforming the ultrasonic signals returned from the receiving test blocks at M discrete points, and let z(m) be the real part of z(m). Let z(m) be the imaginary part; The second initial amplitude is processed to obtain the second amplitude; The relationship between the second amplitude and the second initial amplitude is as follows: ; Based on the first amplitude value corresponding to the temperature, the second amplitude value is corrected to obtain the first bottom wave amplitude value. The relationship between the first bottom wave amplitude value and the first initial amplitude value and the second initial amplitude value is as follows: ; Among them, I n I is the second initial amplitude at temperature n. max k is the second largest initial amplitude among all target temperatures. n The amplitude of the first bottom wave at temperature n; By using the rule of variation between the bottom wave amplitude and the target temperature, the glass transition temperature of the sample is given, thus completing the detection of the glass transition temperature of polymer materials.

[0046] like Figure 5 As shown, the amplitude-temperature change curve of the obtained MPP polymer sample has obvious extreme points, where the amplitude of the vertical axis is the dimensionless relative amplitude, and the temperature corresponding to the extreme point is 72℃, that is, the glass transition temperature of the MPP polymer sample characterized by ultrasound is 72℃.

[0047] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if these modifications and modifications of the invention fall within the scope of the claims and their equivalents, the invention is also intended to include these modifications and modifications.

Claims

1. A method for detecting the glass transition temperature of polymer materials using ultrasonic waves, characterized in that, An apparatus for detecting the glass transition temperature of polymer materials using ultrasonic waves, the apparatus comprising: The signal acquisition module and the signal processing module are included. The signal acquisition module includes a heating component, a fixing component, and a detection component. The fixing component is installed in the heating component and is used to fix the detection component and the test block. The test block is made of polymer material and the detection component includes a probe. During the testing process, the heating component heats and maintains the temperature. The polymer material is placed in the heating component and is heated and maintained as the temperature of the heating component increases. The heating component uses a square water bath. The probe can move relative to the test block in the Z-axis direction of the fixed component. The probe excites and receives the ultrasonic waves returned by the test block. The signal processing module collects and analyzes the ultrasonic waves returned by the test block received by the probe at different time stages to characterize and give the glass transition temperature of the polymer material. The fixing assembly includes a crossbeam, a mechanical cantilever, a first slide rail, a second slide rail, a probe clamp, and a test block clamp. The crossbeam is installed directly above the opening of the heating assembly. The first slide rail is set on the crossbeam and arranged in the X-axis direction. The mechanical cantilever is fixed in the Z-axis and Y-axis directions by the first slide rail and the crossbeam. The second slide rail is arranged in the Z-axis direction of the mechanical cantilever. The probe clamp and the test block clamp are both arranged and connected to the second slide rail. Both the probe clamp and the test block clamp can move in the Z-axis direction. The probe clamp is located above the test block clamp. The probe is mounted on the probe holder, the test block is mounted on the test block holder, the probe is located directly above the test block, the probe excites ultrasonic waves to the test block and receives the ultrasonic waves returned by the test block, and the ultrasonic waves emitted by the probe are perpendicular to the surface of the test block. The method includes the following steps: S1: Debug the probe using a standard block and calibrate the signal processing module, including: the probe excites and receives ultrasound from the standard block at all target temperatures to obtain the corresponding first initial amplitude; process all obtained first initial amplitudes to obtain the corresponding first amplitude. S2: Install the fixing component and the heating component, and fix the detection component to the fixing component; S3: At the initial liquid medium temperature, move the probe along the negative Z-axis until the probe contacts the test block, and adjust the ultrasonic detection gain so that the amplitude of the first echo on the bottom surface of the test block reaches the preset threshold. S4: Move the probe along the positive Z-axis until the probe is higher than the horizontal surface of the liquid medium inside the heating component, and the heating component heats the liquid medium. S5: After the liquid medium temperature reaches the target temperature, move the probe along the negative Z-axis until the probe contacts the test block. The probe then generates ultrasonic waves, receives the ultrasonic waves returned by the test block, and transmits them to the signal processing module. S6: Repeat steps S4-S5 above at all target temperatures of the liquid medium in the heating component, and the probe completes the reception of the ultrasonic waves returned by the test block and the transmission to the signal processing module. S7: The signal processing module analyzes the ultrasonic waves returned by the test block at each target temperature, including: transforming the ultrasonic waves returned by the test block to obtain the second initial amplitude of the signal envelope; processing the second initial amplitude to obtain the second amplitude; combining the first amplitude of the corresponding temperature to correct the second amplitude and obtain the first bottom wave amplitude; and giving the glass transition temperature of the sample based on the variation rule of the first bottom wave amplitude and the target temperature. Complete the detection of the glass transition temperature of polymer materials.

2. The method for detecting the glass transition temperature of polymer materials using ultrasound as described in claim 1, characterized in that, The movement of the sample clamp in the Z-axis direction is below the horizontal plane of the liquid medium inside the heating component, and includes a distance of 5mm-10mm from the vertical distance to the horizontal plane of the liquid medium inside the heating component. The movement of the probe clamp in the negative Z-axis direction is at least such that the probe contacts the sample, and the movement of the probe clamp in the positive Z-axis direction is at least such that the probe is above the horizontal plane of the liquid medium inside the heating component.

3. The method for detecting the glass transition temperature of polymer materials using ultrasound as described in claim 2, characterized in that, A heat-insulating wedge is installed at the bottom of the probe, and a coupling agent is added between the crystal and the wedge inside the probe to achieve ultrasonic signal transmission.

4. The method for detecting the glass transition temperature of polymer materials using ultrasound as described in claim 1, characterized in that, The preset threshold is 80% to 90%, and the target temperature is 0.5℃ to 1℃ different from the previous liquid medium temperature.

5. The method for detecting the glass transition temperature of polymer materials using ultrasound as described in claim 1, characterized in that, The relationship between the first magnitude and the first initial magnitude is as follows: ； Among them, h n h is the first initial amplitude at temperature n. max h is the largest initial amplitude among all target temperatures. n ' is the first amplitude at temperature n.

6. The method for detecting the glass transition temperature of polymer materials using ultrasound as described in claim 1, characterized in that, The ultrasonic waves returned from the receiving test block are transformed to obtain the second initial amplitude of the signal envelope, specifically including: Perform a discrete Fourier transform on the ultrasonic signal returned by the receiving test block to obtain the transformed signal D(i), i=0,1,2,...,M-1; Performing a Z-transform on D(i) yields the following relationship: ； Perform an inverse Fourier transform on Z(i) to obtain the signal z(m); Based on the signal z(m), the second initial amplitude of the signal envelope is calculated, and the calculation relationship is as follows: ； Where M is the number of discrete points of the ultrasonic signal returned by the receiving test block, and I m Let x(m) be the second initial amplitude obtained by transforming the ultrasonic signals returned from the receiving test blocks at M discrete points, and let z(m) be the real part of z(m). Let z(m) be the imaginary part.

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