Method for measuring glass transition temperature of filler-containing polymer

Abstract

The invention discloses a method for measuring the glass transition temperature of a filler-containing polymer, which comprises the following steps of: 1, preparing a filler-containing polymer sample into a flaky sample, and polishing the surface of the sample; 2, fixing the sample on a heating table of a nanomechanical tester, applying a constant load on the filler on the surface of the sample, and measuring the change of displacement along with the temperature by using a high-precision sensor of the nanomechanical tester; 3, analyzing the displacement-temperature curve to obtain the glass transition temperature of the sample; 4, changing the position of the sample, and testing on the polymer to obtain a displacement-temperature curve; and 5, analyzing a displacement-temperature curve measured on the polymer to obtain the glass transition temperature of the sample and the temperature when the polymer is converted into a high-elastic state. According to the invention, the filler and the polymer can be respectively tested to obtain the temperature when the glass transition is completed. According to the invention, a relatively accurate temperature range can be provided for glass transition.

Description

Technical Field

[0001] The invention relates to the technical field of glass transition temperature evaluation, and in particular to a method for measuring the glass transition temperature of a filler-containing polymer. Background Art

[0002] Glass transition is an inherent property of amorphous polymer materials. g ) is one of the characteristic temperatures of polymer materials, which directly affects the performance and process performance of the materials and determines the use temperature of the materials. Therefore, it has long been an important content of polymer physics research. When the glass transition occurs, many physical properties, especially mechanical properties, will change dramatically, and the polymer will change from a rigid glass state to a soft rubber state. In principle, all physical properties that undergo sudden or discontinuous changes during the glass transition process, such as modulus, specific heat, thermal expansion coefficient, refractive index, thermal conductivity, dielectric constant, dielectric loss, mechanical loss, nuclear magnetic resonance absorption, etc. can be used to measure the glass transition temperature. Therefore, there are many methods for testing the glass transition temperature, such as the dilatometer method, the refractometer method, the thermomechanical method (temperature-deformation method), the differential thermal analysis method, the nuclear magnetic resonance method, and the dynamic mechanical analysis method (DMA). Among them, the dynamic mechanical analysis method has excellent reliability and repeatability, and is therefore widely used in the measurement of the glass transition temperature.

[0003] Studies have shown that the properties of micro-nanoscale materials are likely to be different from those of bulk materials, and it is necessary to directly measure the glass transition temperature of micro-nanoscale polymer materials. For uniform micro-nanoscale polymer materials, the dynamic mechanical analysis method of the nanomechanical tester can obtain reliable and repeatable glass transition temperatures. Usually, the storage modulus, loss modulus and Tan-Delta of polymer materials at different temperatures and frequencies are obtained by performing frequency sweeping compression tests at different locations of the sample within a certain frequency range at different temperatures. The glass transition temperature can be obtained by the relationship between the storage modulus, loss modulus and Tan-Delta with temperature. However, for micro-nanoscale polymer materials containing fillers, especially when the fillers are of different sizes and unevenly distributed, the storage modulus, loss modulus and even Tan-Delta measured at different locations of the sample are quite different. The storage modulus, loss modulus and Tan-Delta curves obtained by this method with temperature have large fluctuations, making it difficult or even impossible to obtain an accurate glass transition temperature.

[0004] Patent number ZL202011303310.2 is a method for measuring the glass transition temperature of a polymer containing fillers. This method requires the use of a focused ion beam to process micro-nano-scale cylinders on the surface of a polymer sample containing fillers. The test time is long, and the filler and resin cannot be tested separately. Therefore, a new method for testing the glass transition temperature of a polymer containing fillers needs to be developed. Summary of the invention

[0005] In order to overcome the defects of the above prior art, the present invention provides a method for measuring the glass transition temperature of a filler-containing polymer, which can test the filler and the polymer separately to obtain the temperature when the glass transition is completed. The method has the characteristics of low sample requirements, simple sample preparation, efficient testing and accurate results, and can give a relatively accurate temperature range for the glass transition.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for determining the glass transition temperature of a filler-containing polymer comprises the following steps:

[0008] Step 1: Prepare the filler-containing polymer sample into a thin sheet sample and polish the sample surface;

[0009] Step 2: Fix the sample on the heating stage of the nanomechanical tester, apply a constant load on the filler on the surface of the sample, and use the high-precision sensor of the nanomechanical tester to detect the change of displacement with temperature;

[0010] Step 3: Analyze the displacement-temperature curve to obtain the glass transition temperature of the sample;

[0011] Step 4: Change the sample position, test on the polymer, and obtain the displacement-temperature curve;

[0012] Step 5: Analyze the displacement-temperature curve measured on the polymer to obtain the glass transition temperature of the sample and the temperature at which the polymer transforms into a highly elastic state.

[0013] In the step 1, a filler-containing polymer sample is prepared into a thin sheet with a thickness ranging from tens of micrometers to several millimeters by a mechanical method.

[0014] In the step 2, the sample is glued to the silicon wafer using high temperature silver glue to achieve free expansion of the sample;

[0015] Dynamic creep test is used for data processing, and a dynamic load of a certain frequency is superimposed on the quasi-static load. According to the parameters of the nanomechanical tester, the dynamic loading function is set, and the sample is heated while the load is applied. The temperature range and heating rate are set according to the sample and test requirements, and the change of displacement with temperature is measured.

[0016] In step 2, the high-precision sensor of the nanomechanical tester uses a Berkovich indenter to test the sample.

[0017] In the present invention, the filler may be, for example, silicon dioxide, and the polymer may be, for example, epoxy resin.

[0018] Among them, the temperature corresponding to the sudden increase in displacement in step 3 is the glass transition temperature.

[0019] Beneficial effects of the present invention:

[0020] The present invention aims at the current situation that it is difficult to accurately measure the glass transition temperature of polymer materials containing fillers (especially when the fillers are of different sizes and unevenly distributed) at the micron to millimeter scale. The present invention can quickly obtain the thermal expansion variation curve of samples at the micron to millimeter scale with temperature, and not only obtain the accurate glass transition temperature, but also obtain the temperature when the glass transition is completed.

[0021] The present invention utilizes a tiny pressure head of a nanomechanical tester, and can perform tests on fillers and polymers respectively to obtain respective displacement-temperature curves.

[0022] The present invention can obtain the temperature when the polymer is transformed into a highly elastic state. The present invention relies on the existing nanomechanical tester and the heating device attached thereto, and in principle, no additional equipment needs to be built. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Optical microscope photo of epoxy resin containing silica filler.

[0024] Figure 2 Schematic diagram of the displacement measured on the filler as a function of temperature.

[0025] Figure 3 Schematic diagram of the displacement measured on the resin changing with temperature. DETAILED DESCRIPTION

[0026] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0027] A method for determining the glass transition temperature of a filler-containing polymer comprises the following steps:

[0028] Step 1: Use mechanical methods to prepare the filler-containing polymer sample into a thin sheet with a thickness of about tens of microns to several millimeters, and polish the surface as much as possible;

[0029] Step 2: In order to achieve free expansion of the sample, the sample was glued to the silicon wafer with high-temperature silver glue and then fixed to the heating stage of the nanomechanical tester for testing.

[0030] In order to facilitate data processing, dynamic creep test technology is adopted, that is, dynamic loads of a certain frequency are superimposed on quasi-static loads.

[0031] According to the parameters of the nanomechanical tester, set the dynamic loading function (maximum load, dynamic load amplitude, frequency, holding time, etc.), heat the sample while applying the load, set the temperature range and heating rate according to the sample and test requirements, and measure the change of displacement with temperature;

[0032] Step 3: Plot the displacement of the filled polymer as a function of temperature and analyze the curve to determine the glass transition temperature.

[0033] Step 4: Change the sample position and perform the above test on the filler and epoxy resin respectively.

[0034] Example 1: Glass transition temperature test of epoxy resin sample containing silica filler:

[0035] Test piece: Epoxy resin containing silica filler:

[0036] The test steps are as follows:

[0037] Step 1: Use mechanical methods to prepare the epoxy resin sample containing silica filler into thin sheets and polish the surface as much as possible, such as Figure 1 shown.

[0038] Figure 1 The brighter particles in the middle are silica fillers, and the others are epoxy resins.

[0039] Step 2: Glue the processed sample to the silicon wafer with high-temperature silver glue, and then fix it to the heating table of the nanomechanical tester for testing. Set the dynamic loading function (maximum quasi-static load 1mN, dynamic load amplitude 50μN, frequency 220Hz, load holding time 600s), set the heating table temperature to 80℃, and after the heating table temperature stabilizes at 80℃, use the Berkovich indenter to test on the silica filler. At the same time, heat the sample from 80℃ to 130℃, the heating rate is 5℃ / min, the time is 600s, which is consistent with the load holding time, and measure the change of displacement with temperature.

[0040] Step 3: Draw the displacement curve measured on the filler as a function of temperature, such as Figure 2As shown. From the curve of displacement versus temperature, it can be seen that as the temperature increases, the sample begins to expand and the displacement increases negatively (in the nanomechanical tester, the displacement is positive downward). When the temperature rises to about 90°C, the displacement begins to increase positively. This may be because as the temperature rises, the sample softens and the creep rate of the sample gradually exceeds the thermal expansion rate of the sample. Below 100°C, the displacement changes more slowly with increasing temperature. When the temperature rises to about 100°C, the displacement begins to increase negatively again, and as the temperature rises, the displacement increases negatively very quickly, thus determining that the glass transition temperature is about 100°C.

[0041] Step 4: Change the test position and test on epoxy resin. The displacement-temperature curve is as follows: Figure 3 As shown. From the curve of displacement versus temperature, it can be seen that as the temperature increases, the sample begins to expand and the displacement increases negatively (in the nanomechanical tester, the displacement is positive downward). When the temperature rises to about 86°C, the displacement begins to increase positively. This is because as the temperature rises, the sample softens and the creep rate of the sample gradually exceeds the thermal expansion rate of the sample. When the temperature rises to about 97°C, the displacement begins to increase negatively again, and as the temperature rises, the displacement increases negatively very quickly. It is determined that the glass transition temperature is about 97°C. Compared with the results measured on the filler, the transition temperature is advanced. This is because the softening of the sample and the glass transition are both caused by the epoxy resin.

[0042] When the indenter is measuring on epoxy resin, the indenter can quickly sense the changes in epoxy resin. However, when the indenter is measuring on filler, the changes in epoxy resin need to be transmitted to the indenter through the filler, resulting in a lag in the changes in epoxy resin measured by the indenter, or even the inability to measure the changes in epoxy resin. As the temperature further increases, when the temperature reaches 120°C, the displacement begins to increase positively again. This is because the sample enters a highly elastic state and becomes softer. Therefore, it is determined that the temperature at which the epoxy resin changes to a highly elastic state is 120°C.

[0043] In summary, in view of the current situation that the glass transition temperature of polymer materials containing fillers (especially when the fillers are of different sizes and unevenly distributed) at the micron to millimeter scale is difficult to measure accurately, the present invention can quickly obtain the curve of thermal expansion variation with temperature of samples at the micron to millimeter scale, not only to obtain the accurate glass transition temperature, but also to obtain the temperature when the glass transition is completed. Compared with the existing methods, the method of the present invention is simple in sample preparation, efficient in testing, and accurate in results. Tests can be carried out on fillers and polymers respectively to obtain their respective displacement-temperature curves. The temperature when the polymer is transformed into a highly elastic state can be obtained. The present invention relies on the existing nanomechanical tester and its accompanying heating device, and in principle, no additional equipment needs to be built. The invention is of great significance to the application and development of polymer materials and the measurement of glass transition temperature.

Claims

1. A method for determining the glass transition temperature of a filler-containing polymer, characterized in that: The following steps are involved: Step 1: Prepare the filler-containing polymer sample into a thin sheet sample and polish the sample surface; Step 2: Fix the sample on the heating stage of the nanomechanical tester, apply a constant load on the filler on the surface of the sample, and use the high-precision sensor of the nanomechanical tester to measure the change of displacement with temperature; Step 3: Analyze the displacement-temperature curve to obtain the glass transition temperature of the sample; Step 4: Change the sample position, test on the polymer, and obtain the displacement-temperature curve; Step 5: Analyze the displacement-temperature curve measured on the polymer to obtain the glass transition temperature of the sample and the temperature at which the polymer transforms into a highly elastic state.

2. The method for determining the glass transition temperature of a filler-containing polymer according to claim 1, characterized in that: In the step 1, a filler-containing polymer sample is prepared into a thin sheet with a thickness ranging from tens of micrometers to several millimeters by a mechanical method.

3. The method for determining the glass transition temperature of a filler-containing polymer according to claim 1, characterized in that: In step 2, the sample is glued to the silicon wafer using high-temperature silver glue to achieve free expansion of the sample.

4. The method for determining the glass transition temperature of a filler-containing polymer according to claim 3, characterized in that: Dynamic creep test is used for data processing, and a dynamic load of a certain frequency is superimposed on the quasi-static load. According to the parameters of the nanomechanical tester, the dynamic loading function is set, and the sample is heated while the load is applied. The temperature range and heating rate are set according to the sample and test requirements, and the change of displacement with temperature is measured.

5. The method for determining the glass transition temperature of a filler-containing polymer according to claim 1, characterized in that: In step 2, the high-precision sensor of the nanomechanical tester uses a Berkovich indenter to test the sample.

6. The method for determining the glass transition temperature of a filler-containing polymer according to claim 1, characterized in that: Examples of fillers include silica and polymers include epoxy resins.

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