JPS61111449A - Thermogravimetric analysis method - Google Patents

Abstract

PURPOSE:To calculate activation energy having interchangeability without variance even if measuring apparatus and measuring conditions vary by limiting a weight decrease in a prescribed range and calculating the activation energy by an Ozawa's method using the thermo-balance data in the linear range of a relatively low temp. elevating rate. CONSTITUTION:The Ozawa's calculation is executed with the low range of a weight decrease rate by using data on the temp. elevating rate only wethin the specified value range by which the activation energy DELTAE is calculated. More specifically, the temp. elevating rate is first set at 1 deg.C/min and the sample is heated. Each temp. T03 and time when the weight decrease rate attains 3%, 4%, 5% with the weight at the temp. T0 when the actual temp. elevating rate is constant as a reference are measured and the temp. elevating rate beta=dT/dt is calculated. The similar measurement is executed with the case of 2 deg.C/min and 5 deg.C/min stemp. elevating rate. The data is further subjected offline to processing and the Ozawa's calculation is executed, by which the activation energy DELTAE of the sample is calculated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates primarily to a thermogravimetric analysis method for short-term heat resistance testing of electrically insulating materials.

[Technical background of the invention and its problems] Short-time heat resistance test 1@1 for evaluating the heat resistance of insulating materials in a short time: As the demand for this test increases, one of the methods is to evaluate heat resistance by thermogravimetric analysis. Evaluation methods have been developed.

As a thermogravimetric analysis method, a thermobalance (hereinafter referred to as TG) is used to measure the time-quantitative progress of weight reduction of the insulating material due to heating, and from this TO curve, the activation energy of deterioration ΔE [
Although there is a method for calculating ΔE], there are variations in the measurement results of ΔE depending on the type of TG used and measurement conditions, making it difficult to obtain a unique ΔE as common data.

One of the reasons for the variation in the measurement results of ΔE is
There is a variation in the rate of temperature rise in the TG.

Tables 1 to 3 are manufactured by Company A, Company B, and Company C (DTG), respectively.
100% of PVF (polyvinyl formal) using
Actual heating rate average value ("C/min ] is shown by the present inventors, and it was found that the actual heating rate varies depending on the type of TG, heating temperature range, and heating rate setting value. The number in the name is the temperature increase rate set value C°C/min].

Table 1 Table 2 Table 3 According to the study results of the present inventors, the variation in the average temperature increase rate is mainly due to the delay in the rise of temperature at the initial stage of heating.

On the other hand, as a method of calculating ΔB from the TG curve, multiple T
Ozawa's method, which performs mathematical processing on the G curve [see Institute of Electrical Engineers of Japan Technical Report (Part ■) No. 134 (August 1986)] is recommended, but in this case too, the analysis results may vary depending on the measurement conditions. Figure 2 shows an example of the ΔB calculation results when the number of TG curves used in the calculation is changed, and Figure 3 shows an example of the ΔB calculation results when TG0 curves with different heating rates are used. , when a TG curve with a fast heating rate is used, the reaction of the sample cannot follow the heating rate, and therefore ΔE appears to be higher than expected. The state in which the measurement results of ΔE change is shown for the cases where TGs from Company A, Company B, and Company 0 are used, and in this case as well, there is overall variation in the 1° measurement results of ΔE.

The reason for this is that, as described above, differences in the structure of the TG itself result in differences in nonlinearity of temperature rise characteristics, temperature detection characteristics in thermogravimetric measurements, buoyancy effects during heating, and the like.

Therefore, by limiting the measurement conditions, variations in the measurement results of ΔE can be reduced.

Figure 5 shows the measurement results of ΔE when the temperature increase rate is limited to a temperature range where the temperature increase characteristic is linear.
This is shown for TG of 0 company, and in this case, the weight reduction rate is 5% or less, and the To of 3 companies shows the same results.

Object of the Invention The present invention limits the weight loss point to a predetermined range, and uses TG data in a linear range with a relatively low heating rate to calculate ΔB.
[Summary of the Invention] The present invention aims to provide a rational thermogravimetric analysis method that calculates ΔE using Ozawa's method and thereby obtains a compatible and unique ΔE. Thermogravimetric analysis is carried out by heating a sample. The measurement data of a thermobalance is read at a low heating rate and within a certain range of heating rates until a predetermined low weight loss rate is reached. The above measurement data is calculated using Ozawa's method. This thermogravimetric analysis method calculates activation energy through processing, and thereby allows calculation of consistent and compatible activation energy even when measuring equipment and measurement conditions are different.

[Embodiments of the invention] An embodiment of the present invention is shown in FIG.

In FIG. 1, 1 is a TG, heating and measurement are controlled by a control device 2, and measurement data is recorded in a temperature and weight recorder 3.

On the other hand, the above measurement data is inputted to the microcomputer 5 via the interface 4 and subjected to calculation processing, and the calculation results are plotted on the plotter 7 and typed on the printer 8.

6 is a timer that controls the operation of the microcomputer 5.

Note that the measurement data of the microcomputer 51dTG1 is usually processed offline.

In consideration of the above-mentioned problem, the present invention uses data only in the range where the heating rate is a constant value, and performs Ozawa's calculation for the range where the weight loss rate is low (for example, 3%, 4%, 5 cm) to calculate ΔE. calculate. - In order to increase the accuracy of calculations, each measurement value is read as a digital value of 3 or more digits.

That is, first, the sample is heated by setting the temperature increase rate to 1° C./min.

Temperature T when the actual temperature increase rate becomes constant.

The weight reduction rate is 3% based on the weight of
The temperature increase rate β±7 is calculated by measuring each temperature To8 and the time when the temperature becomes high.

Similar measurements are performed for temperature increase rates of 2° C./min and 5° C./min.

Further, the above data is processed off-line and Ozawa's calculation is performed to calculate the activation energy ΔE of the material.

That is, find the TG curve for each heating rate.

This is the common logarithm of the heating rate on the Y axis, the opposite of absolute temperature! If the pattern is plotted on a graph with the X axis as a straight line, the slope of this straight line is determined by the method of least squares, and the activation energy ΔE is calculated from the slope α using the following formula.

1,987 ΔE=□×α 0,4567 "Effects of the Invention" As explained above, according to the present invention, the activity of the insulating material is calculated by processing the measurement data of the thermobalance that heats the insulating material using Ozawa's method. In the thermogravimetric analysis method for heat resistance evaluation that calculates the chemical energy, the measurement data when heated with a thermobalance is obtained when the heating rate is relatively low and stable, and the data is obtained within a relatively small range of weight loss rate. Since it is used as the measurement data for Ozawa's calculation, there is no variation due to the thermobalance model or measurement conditions, and it is possible to calculate a compatible and unique activation energy.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of measuring equipment showing one embodiment of the present invention;
5 to 5 are graphs showing measurement data for explaining conventional problems in thermogravimetric analysis. 1...Thermobalance (TG) 2...Control device 3...
・Temperature Nik recorder 4...Interface PS5・
...Microcomputer 6...Timer 7...Plotter 8...Printer agent Patent attorney Yoshiaki Inomata (1 person) (see Figure 1 and Figure 2) Figure 4 Fish mass extinction + P (1) Figure 5 Stop - area game (χ n

Claims (1)

[Claims] The measurement data of a thermobalance for heating a sample for heat resistance evaluation and thermogravimetric analysis is read repeatedly at a low heating rate and within a certain range of heating rates until a predetermined low weight loss rate is reached. A thermogravimetric analysis method characterized by calculating activation energy by performing calculation processing using a method.