阅读说明：本技术 利用纳米力学测试仪实现三种玻璃化转变温度测试方法 (Method for realizing three glass transition temperature tests by using nano-mechanical tester ) 是由 秦元斌 付琴琴 解德刚 张朋诚 单智伟 张鹏 于 2020-11-19 设计创作，主要内容包括：本发明公开了利用纳米力学测试仪实现三种玻璃化转变温度测试方法,同时实现了测试结果的统一。该发明利用纳米力学测试仪,结合加热台,利用多种方法对非晶态高分子材料的玻璃化转变温度进行测量,集多种测试方法于一体,并对每种测试方法的结果进行比较,给出更为全面准确且一致的玻璃化转变温度,期待在高分子材料应用、玻璃化转变温度测量等领域具有良好的应用前景。(The invention discloses a method for realizing three glass transition temperature tests by using a nano mechanical tester, and simultaneously realizes the unification of test results. The invention utilizes a nano-mechanical tester and combines a heating table, utilizes a plurality of methods to measure the glass-transition temperature of the amorphous polymer material, integrates the plurality of testing methods, compares the results of each testing method, provides more comprehensive, accurate and consistent glass-transition temperature, and is expected to have good application prospect in the fields of polymer material application, glass-transition temperature measurement and the like.)

1. Three glass transition temperature test methods are realized by utilizing a nano mechanical tester, and the method is characterized by comprising the following steps;

the method comprises the following steps:

the method comprises the following steps of preparing a test sample into a wedge-shaped sample or a step-shaped sample, and fixing the wedge-shaped sample or the step-shaped sample on a heating table of a nanometer mechanical tester for measuring the thermal expansion coefficient, wherein the specific implementation mode is disclosed in the patent of 'a method for measuring the thermal expansion coefficient of a tiny test sample by using a nanometer mechanical tester', and the application number is 201910462583.2;

step two:

obtaining the thermal expansion coefficient or relative expansion amount of the sample at different temperatures, and obtaining the glass transition temperature of the material according to the change curve of the thermal expansion coefficient or relative expansion amount along with the temperature;

step three:

performing frequency sweep indentation test on the sample in a certain frequency range at different temperatures to obtain the storage modulus, loss modulus and Tan-Delta of the high polymer material at different temperatures and different frequencies, and obtaining the glass transition temperature through the change relationship of the storage modulus, the loss modulus and the Tan-Delta along with the temperature;

step four:

applying a constant load on the surface of a sample, measuring the change of displacement along with temperature by using a high-precision sensor of a nano mechanical tester to obtain a displacement-temperature curve, and finding out the temperature corresponding to an inflection point on the curve, namely the glass transition temperature;

step five:

changing the test conditions as required and repeating the steps;

step six:

and comparing the test results, giving out uniform glass transition temperature, and giving out test conditions or definition modes of different methods according to the temperature.

2. The method for realizing three glass transition temperatures by using a nanomechanical tester as recited in claim 1, wherein the three frequencies in the step range from 1 to 200 Hz.

3. The method for realizing three glass transition temperatures by using a nanomechanical tester as recited in claim 1, wherein the constant load in the fourth step is determined according to the load and displacement range of the nanomechanical tester and the sample, and is generally 1-10 mN.

4. The method for realizing three glass transition temperatures by using a nanomechanical tester as recited in claim 1, wherein the temperature change in the first and fourth steps is 5 ℃/min.

Technical Field

The invention relates to the technical field of glass transition temperature evaluation, in particular to a method for realizing three glass transition temperature tests by utilizing a nanometer mechanical tester.

Background

Glass transition amorphous high molecular polymerIntrinsic property of the material, glass transition temperature (T)_g) The temperature is one of the characteristic temperatures of high polymer materials, directly influences the service performance and the process performance of the materials, and determines the service temperature of the materials, so that the temperature is an important content of high polymer physical research for a long time. When glass transition occurs, many physical properties, particularly mechanical properties, change dramatically, and the polymer changes from a rigid glassy state to a soft rubbery state. In principle, all physical properties which change abruptly or discontinuously during the glass transition, such as modulus, specific heat, coefficient of thermal expansion, refractive index, thermal conductivity, dielectric constant, dielectric loss, mechanical loss, nuclear magnetic resonance absorption, etc., can be used for measuring the glass transition temperature. Therefore, there are many methods for measuring the glass transition temperature, such as dilatometry, refractive index method, thermomechanical method (temperature-deformation method), differential thermal analysis method, Dynamic Mechanical Analysis (DMA), and nuclear magnetic resonance method. However, it is likely that the glass transition temperatures obtained for different test methods will vary, even if the same test method has a T measured under different test conditions or in different defined ways_gCan also vary greatly. For example, in the dynamic mechanical analysis, the glass transition temperature is defined as a temperature at the starting point of a sharp decrease in storage modulus, as a temperature corresponding to the peak value of loss modulus, and as a temperature corresponding to the peak value of Tan-Delta (ratio of loss modulus to storage modulus), and the glass transition temperatures obtained by different definition methods are greatly different. Measurement T of a Material depending on the test method (test conditions, definition mode)_gCan vary by about 50 c or even higher, which seriously affects the application of the polymeric material and the communication between researchers. Therefore, it is necessary to unify various test methods, various test conditions, and various definition methods to obtain a unified and accurate glass transition temperature.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention aims to provide a method for realizing three glass transition temperature tests by using a nanomechanical tester, and the glass transition temperature of a polymer material can be obtained more comprehensively, accurately and uniformly. Specific test conditions and defining ways can be given for different test methods.

In order to achieve the purpose, the invention adopts the technical scheme that:

three glass transition temperature test methods are realized by utilizing a nano mechanical tester, and the method comprises the following steps;

the method comprises the following steps:

the method comprises the following steps of preparing a test sample into a wedge-shaped sample or a step-shaped sample, and fixing the wedge-shaped sample or the step-shaped sample on a heating table of a nanometer mechanical tester for measuring the thermal expansion coefficient, wherein the specific implementation mode is disclosed in the patent of 'a method for measuring the thermal expansion coefficient of a tiny test sample by using a nanometer mechanical tester', and the application number is 201910462583.2;

step two:

obtaining the thermal expansion coefficient or relative expansion amount of the sample at different temperatures, and obtaining the glass transition temperature of the material according to the change curve of the thermal expansion coefficient or relative expansion amount along with the temperature;

step three:

performing frequency sweep indentation test on the sample in a certain frequency range at different temperatures to obtain the storage modulus, loss modulus and Tan-Delta of the high polymer material at different temperatures and different frequencies, and obtaining the glass transition temperature through the change relationship of the storage modulus, the loss modulus and the Tan-Delta along with the temperature;

step four:

applying a constant load on the surface of a sample, measuring the change of displacement along with temperature by using a high-precision sensor of a nano mechanical tester to obtain a displacement-temperature curve, and finding out the temperature corresponding to an inflection point on the curve, namely the glass transition temperature;

step five:

changing the test conditions (such as heating rate, test frequency and the like) according to the requirements and repeating the steps;

step six:

and comparing the test results, giving out uniform glass transition temperature, and giving out test conditions or definition modes of different methods according to the temperature.

The three frequency ranges of the steps are 1-200 Hz.

The constant load in the fourth step is determined according to the load and displacement measuring range of the nano mechanical tester and a sample, and is generally 1-10 mN.

The temperature change in said steps one and four is 5 deg.C/min.

The invention has the beneficial effects that:

the invention relies on the existing nanometer mechanics tester and the heating device attached to the tester, and in principle, no additional equipment is required to be built.

The invention realizes three testing methods of glass transition temperature on the same nanometer mechanical tester, and expands the application of the nanometer mechanical tester.

The invention realizes the three testing methods on the same equipment, and avoids errors caused by the temperature measurement problems of different equipment.

The invention can obtain more comprehensive, accurate and uniform glass transition temperature of the polymer material. Specific test conditions and definition modes can be given to different test methods, so that comparison among different test methods and communication among researchers are facilitated.

Drawings

FIG. 1 is a graph showing the relative expansion of an epoxy resin as a function of temperature.

FIG. 2 is a plot of storage modulus versus temperature at a test frequency of 1 Hz.

FIG. 3 is a graph of loss modulus versus temperature with a test frequency of 1 Hz.

FIG. 4 is a plot of Tan-Delta as a function of temperature with a test frequency of 1 Hz.

FIG. 5 is a displacement-temperature curve obtained by applying a constant load of 10mN to the surface of an epoxy resin sample and using a high-precision sensor of a nanomechanical tester.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings.

Example 1:

glass transition temperature testing of epoxy resin samples:

test piece: epofix cold curing embedding resin produced by Struers company has the following specific preparation method: the resin and the curing agent are uniformly mixed according to the weight ratio of 25:3, and then the mixture is placed in a vacuum tank for vacuumizing so as to reduce bubbles in the epoxy resin, and the curing is carried out for more than 12 hours. The epoxy resin is polished by a mechanical method, and then the sample is heated to more than 100 ℃ and slowly cooled to reduce the influence of stress in the sample preparation process, so that a more uniform sample with more stable performance is obtained.

The test procedure was as follows:

(1) the method for measuring the thermal expansion coefficient of the micro test sample by using the nanometer mechanical tester is disclosed in the embodiment, which is a patent with the application number of 201910462583.2. The specific test is divided into three sections: the temperature rise rate is 5 ℃/min at 30-40 ℃, the maximum load is 10mN, and the load retention time is 120 s; the temperature rise rate is 5 ℃/min at 40-50 ℃, the maximum load is 8mN, and the load retention time is 120 s; the temperature rise rate is 5 ℃/min at 50-55 ℃, the maximum load is 4mN, and the load retention time is 60 s.

The relative expansion rate of the finally obtained epoxy resin as a function of temperature is shown in FIG. 1, and it can be seen from this change that the glass transition temperature of the epoxy resin obtained by this test method is about 50 ℃.

(2) The sample is subjected to frequency sweep indentation test at different temperatures in the range of 1-200Hz to obtain the storage modulus, loss modulus and Tan-Delta of the epoxy resin at different temperatures and different frequencies, as shown in FIGS. 2, 3 and 4. FIGS. 2, 3 and 4 are graphs of the storage modulus, loss modulus and Tan-Delta of epoxy resin with temperature, respectively, and the test frequency is 1 Hz. If the temperature at which the onset of a sharp decrease in storage modulus is selected is the glass transition temperature, the glass transition temperature of this epoxy resin is approximately 50 ℃, which is in accordance with the aforementioned glass transition temperature measured by the coefficient of thermal expansion. If the temperature corresponding to the peak of the loss modulus is selected as the glass transition temperature, it is difficult to determine an accurate peak value because the loss modulus fluctuates greatly. If the peak of Tan-Delta is chosen to correspond to a glass transition temperature, the glass transition temperature is about 82 deg.C, well above 50 deg.C.

(3) Applying a constant load of 10mN on the surface of an epoxy resin sample, keeping the load for 360s, measuring the change of displacement along with the temperature by using a high-precision sensor of a nano mechanical tester within the range of 30-60 ℃, and obtaining a displacement-temperature curve at the temperature rise rate of 5 ℃/min, as shown in figure 5. The glass transition temperature of the epoxy resin obtained from this curve is about 50 ℃. At about 30.4 c, the curve has an inflection point due to sample creep, which is greater at the beginning of the test and at a rate greater than the thermal expansion rate. There is also an inflection in the curve at about 53.8 c because the sample has transitioned from a hard glassy state to a soft rubbery state.

From the above analysis, we can see that the glass transition temperature of the epoxy resin can be determined to be about 50 ℃, and different testing methods can obtain a more uniform test result. For the dynamic mechanical analysis, the temperature of the starting point of the sharp decrease of the storage modulus (test frequency of 1Hz) should be selected as the glass transition temperature, and for other methods, the temperature increase rate is preferably selected to be 5 ℃/min.

In summary, the present invention addresses such a situation: it is likely that the glass transition temperatures of the polymeric materials obtained by the different test methods will vary, even if the T measured under different test conditions or in different defined ways by the same test method_gWill also be different. According to the test method, measurement T of the material_gCan vary by about 50 c or even higher, which seriously affects the application of the polymer and communication between researchers. The invention can obtain the glass transition temperature of the same material by three different methods on the same equipment, and can compare the results of different test methods to further obtain more accurate and same glass transition temperature. Practice shows that different test methods can obtain a uniform test result under specific test conditions and specific definition modes, and communication between the same rows is facilitated. The method has important significance for the application and development of high polymer materials and the measurement of the glass transition temperature.