Thermal degradation determination method, thermal history estimation method, thermal degradation determination device, and thermal history estimation device

Abstract

This thermal degradation determination method involves determining thermal degradation of a rubber composition. The thermal degradation determination method includes a thermal degradation determination process for determining whether the thermal degradation of the rubber composition exceeds a predetermined level of thermal degradation. The thermal degradation determination process involves comparing the weight ratio of a carbon precursor in the rubber composition with a set threshold value to determine whether the thermal degradation of the rubber composition exceeds the predetermined level of thermal degradation.

Description

Thermal degradation determination method, thermal history estimation method, thermal degradation determination device, thermal history estimation device

[0001] The present invention relates to a thermal degradation determination method, a thermal history estimation method, a thermal degradation determination device, and a thermal history estimation device.

[0002] Degradation of rubber compositions has been evaluated in the past. For example, thermal degradation of rubber compositions has been evaluated by examining changes in the chemical structure of the rubber composition or measuring changes in the hardness of the rubber composition using FT-IR (see, for example, Non-Patent Document 1).

[0003] Tetsuya Kawashima and Toshio Ogawa, "Destruction of NBR due to Thermal Degradation," Journal of the Society of Rubber Science and Technology of Japan, Vol. 75, No. 6, 2002, The Society of Rubber Science and Technology of Japan, pp. 257-262

[0004] However, conventional evaluation methods have difficulty quantifying the thermal degradation of rubber compositions, and even if quantification is achieved, the evaluation range is wide, making it difficult to accurately evaluate the thermal degradation of rubber compositions. Therefore, there is a demand for a method and an apparatus that can accurately evaluate the thermal degradation of rubber compositions.

[0005] The present invention has been made in consideration of the above-mentioned problems, and its purpose is to provide a thermal degradation determination method, a thermal history estimation method, a thermal degradation determination device, and a thermal history estimation device that can accurately evaluate the thermal degradation of a rubber composition.

[0006] In order to achieve the above-mentioned object, the thermal degradation determination method of the present invention is a thermal degradation determination method for determining thermal degradation of a rubber composition, and includes a thermal degradation determination process for determining whether the thermal degradation of the rubber composition exceeds a predetermined degree of thermal degradation, and the thermal degradation determination process compares the weight ratio of carbon precursor in the rubber composition with a set threshold value to determine whether the thermal degradation of the rubber composition exceeds the predetermined degree of thermal degradation.

[0007] In one embodiment of the thermal degradation determination method of the present invention, the threshold value is a value based on the weight ratio of the carbon precursor in a reference rubber composition, which is a rubber composition used under one or more specified thermal degradation conditions, and the thermal degradation determination process determines that the thermal degradation of the rubber composition exceeds the specified degree of thermal degradation if the weight ratio of the carbon precursor in the rubber composition is greater than the threshold value.

[0008] A thermal degradation determination method according to one embodiment of the present invention includes a carbonization rate detection process for determining the weight ratio of carbon precursors in the rubber composition, and the carbonization rate detection process determines the weight ratio of the components of the rubber composition by comparing it with the weight ratio of the components of a reference rubber composition, which is an unused rubber composition.

[0009] In the method for determining thermal degradation according to one aspect of the present invention, the components of the rubber composition and the reference rubber composition are polymers.

[0010] A method for determining thermal degradation according to one aspect of the present invention calculates the weight ratio of the carbon precursor in the rubber composition by subtracting the weight ratio of the polymer in the rubber composition from the weight ratio of the polymer in the reference rubber composition.

[0011] In the thermal degradation determining method according to one aspect of the present invention, the component of the rubber composition and the reference rubber composition is a carbon component.

[0012] A thermal degradation determination method according to one aspect of the present invention calculates the weight ratio of the carbon precursor in the rubber composition by subtracting the weight ratio of the carbon component in the reference rubber composition from the weight ratio of the carbon component in the rubber composition.

[0013] In a method for determining thermal degradation according to one aspect of the present invention, the weight ratio of the polymers is measured by thermogravimetric analysis.

[0014] A method for determining thermal deterioration according to one aspect of the present invention measures the weight ratio of the carbon component by thermogravimetric analysis.

[0015] In a method for determining thermal degradation according to one aspect of the present invention, the weight ratio of the carbon precursor in the reference rubber composition is set in advance.

[0016] A method for determining thermal degradation according to one embodiment of the present invention prepares a plurality of thermally degraded rubber compositions, which are rubber compositions used under different thermal degradation conditions, and selects the reference rubber composition from among the plurality of thermally degraded rubber compositions.

[0017] In the thermal degradation determination method according to one aspect of the present invention, the threshold value is a predetermined weight ratio.

[0018] In a thermal degradation determination method according to one aspect of the present invention, the predetermined thermal degradation conditions include at least one of temperature and time.

[0019] In order to achieve the above-mentioned object, the thermal history estimation method of the present invention is a thermal history estimation method for estimating the thermal history of a rubber composition, and includes a thermal history estimation process for identifying the thermal history of a used rubber composition, which is the rubber composition that has been used, and the thermal history estimation process identifies the temperature at which the used rubber composition was used based on the weight ratio of a carbon precursor in the used rubber composition.

[0020] In a thermal history estimation method according to one aspect of the present invention, the weight ratio of the carbon precursor in a reference rubber composition, which is a rubber composition used under one or more predetermined thermal degradation conditions, and the predetermined thermal degradation conditions are prepared in advance, and the predetermined thermal degradation conditions are the time and temperature at which the reference rubber composition was used. The thermal history estimation process compares the weight ratio of the carbon precursor in the used rubber composition and the time at which the used rubber composition was used with the weight ratio of the carbon precursor in the reference rubber composition and the time among the predetermined thermal degradation conditions to identify the temperature at which the used rubber composition was used.

[0021] In the thermal history estimation method according to one aspect of the present invention, the time during which the rubber composition has been used is an estimated value.

[0022] A thermal history estimation method according to one embodiment of the present invention includes a carbonization rate detection process for identifying the weight ratio of carbon precursors in the rubber composition, and the carbonization rate detection process identifies the weight ratio of the components of the rubber composition by comparing it with the weight ratio of the components of a reference rubber composition, which is an unused rubber composition.

[0023] In the thermal history estimation method according to one aspect of the present invention, the components of the rubber composition and the reference rubber composition are polymers.

[0024] A thermal history estimation method according to one aspect of the present invention calculates the weight ratio of the carbon precursor in the rubber composition by subtracting the weight ratio of the polymer in the rubber composition from the weight ratio of the polymer in the reference rubber composition.

[0025] In the thermal history estimation method according to one aspect of the present invention, the components of the rubber composition and the reference rubber composition are carbon components.

[0026] A thermal history estimation method according to one aspect of the present invention calculates the weight ratio of the carbon precursor in the rubber composition by subtracting the weight ratio of the carbon component in the reference rubber composition from the weight ratio of the carbon component in the rubber composition.

[0027] In a thermal history estimation method according to one aspect of the present invention, the weight ratio of the polymers is measured by thermogravimetric analysis.

[0028] A thermal history estimation method according to one aspect of the present invention measures the weight ratio of the carbon component by thermogravimetric analysis.

[0029] In order to achieve the above-mentioned object, the thermal degradation determination device of the present invention is a thermal degradation determination device that determines the thermal degradation of a rubber composition, and is equipped with a thermal degradation determination processing unit that determines whether the thermal degradation of the rubber composition exceeds a predetermined degree of thermal degradation, and the thermal degradation determination processing unit compares the weight ratio of carbon precursor in the rubber composition with a set threshold value to determine whether the thermal degradation of the rubber composition exceeds the predetermined degree of thermal degradation.

[0030] In order to achieve the above-mentioned object, the thermal history estimation device of the present invention is a thermal history estimation device that estimates the thermal history of a rubber composition, and is equipped with a thermal history estimation processing unit that identifies the thermal history of a used rubber composition, which is the rubber composition that has been used, and the thermal history estimation processing unit identifies the temperature at which the used rubber composition was used based on the weight ratio of a carbon precursor in the used rubber composition.

[0031] According to the present invention, it is possible to provide a thermal degradation determination method, a thermal history estimation method, a thermal degradation determination device, and a thermal history estimation device that can accurately evaluate the thermal degradation of a rubber composition.

[0032] FIG. 1 is a diagram illustrating the results of thermogravimetric analysis (TGA) on a rubber composition. FIG. 2 is a diagram illustrating an example of a target for thermal degradation determination by the thermal degradation determination method according to the present embodiment. FIG. 3 is a diagram for explaining a usage environment / carbonization rate table generated in the thermal degradation determination method according to the present embodiment. FIG. 4 is a diagram for explaining a usage environment / carbonization rate table generated in the thermal degradation determination method according to the present embodiment. FIG. 5 is a diagram for explaining thresholds in the thermal degradation determination method according to the present embodiment. FIG. 6 is a flowchart of a thermal degradation determination process for executing the thermal degradation determination method. FIG. 7 is a flowchart of a carbonization rate detection process performed in the thermal degradation determination process. FIG. 8 is a flowchart of a thermal history estimation process for executing the thermal history estimation method according to an embodiment of the present invention. FIG. 9 is a block diagram showing the functional configuration of a thermal degradation determination device for executing the thermal degradation determination method according to the present embodiment. FIG. 10 is a block diagram showing the functional configuration of a thermal history estimation device for executing the thermal history estimation method according to the present embodiment.

[0033] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0034] As a result of extensive research, the present inventors have newly discovered that the degree of thermal degradation of a rubber composition is related to the amount of carbon precursor contained in the rubber composition. Based on this discovery, the present invention was completed through further research.

[0035] A thermal degradation determination method according to the present invention is a method for determining thermal degradation of a rubber composition. The thermal degradation determination method according to the present invention includes a thermal degradation determination process for determining whether thermal degradation of the rubber composition exceeds a predetermined level. The thermal degradation determination process compares the weight ratio of the carbon precursor in the rubber composition with a set threshold value to determine whether thermal degradation of the rubber composition exceeds the predetermined level.

[0036] Furthermore, a thermal history estimation method according to the present invention is a thermal history estimation method for estimating the thermal history of a rubber composition. The thermal history estimation method according to the embodiment of the present invention includes a thermal history estimation process for identifying the thermal history of a used rubber composition, which is a rubber composition that has been used. The thermal history estimation process identifies the temperature at which the used rubber composition was used, based on the weight ratio of a carbon precursor in the used rubber composition.

[0037] As described above, the present invention determines the degree of thermal degradation of a used rubber composition based on the weight ratio of the carbon precursor contained in the used rubber composition, and also estimates the thermal history of the used rubber composition. The weight ratio of the carbon precursor contained in the rubber composition is the ratio of the weight of the carbon precursor contained in the rubber composition to the total weight of the rubber composition. Hereinafter, in this description, the weight ratio of the carbon precursor contained in the rubber composition is also referred to as the carbonization rate.

[0038] The carbon precursor is produced when a rubber composition is heated in an air atmosphere, causing thermal degradation (thermo-oxidative degradation) of the polymer in the rubber composition, resulting in cyclization of the polymer. The carbon precursor is a char formed by carbonization of the polymer in the rubber composition. In this way, when heated at high temperatures, the polymer contained in the rubber composition undergoes thermal degradation, undergoes a structural change, and undergoes cyclization to become a carbon precursor. The present invention determines the amount of carbon precursor produced by thermal degradation of the polymer contained in the rubber composition, and determines the degree of thermal degradation of the rubber composition or estimates the thermal history of the rubber composition. The thermal history of a rubber composition refers to the temperature at which the rubber composition was used, i.e., the ambient temperature of the environment in which the rubber composition was used, and the time the rubber composition was used.

[0039] First, the principles of detecting thermal degradation of a rubber composition in the thermal degradation determination method and thermal history estimation method according to the present invention will be described. FIG. 1 is a diagram illustrating the results of thermogravimetric analysis (TGA) of a rubber composition. In FIG. 1, the solid line A shows the analysis results of a used rubber composition, which is a rubber composition that has been used, while the dashed line B shows the analysis results of a reference rubber composition, which is a rubber composition that has not been used. The used rubber composition is, for example, a rubber composition that has been used in a given usage environment. As described above, the usage environment refers to the ambient temperature in the environment in which the rubber composition is used and the usage time at this ambient temperature. An example of the rubber composition to be analyzed is a test piece of hydrogenated nitrile rubber (HNBR). Furthermore, an example of the usage environment for the used rubber composition is 130°C to 150°C and 500 hours to 550 hours. In other words, the used rubber composition is a test piece of an unused rubber composition that has been heated at a temperature of 130°C to 150°C for 500 to 550 hours.

[0040] The heating step of the rubber composition in the thermogravimetric analysis is performed as shown by the solid line C and the right horizontal axis in FIG. 1 , in which a first heating H1 is performed in an inert gas atmosphere to heat the rubber composition within a predetermined first temperature range, and then a second heating H2 is performed in an air atmosphere to heat the rubber composition within a predetermined second temperature range. As an example, the first heating H1 is performed in an inert gas atmosphere, in which nitrogen (N ２ In the second heating H2, the temperature is increased at a predetermined gradient in a first temperature range from 35° C. to 600° C. in an air atmosphere, and then decreased at a predetermined gradient. In the subsequent second heating H2, the temperature is increased at a predetermined gradient in a second temperature range from about 400° C. to 1000° C. in an air atmosphere, for example.

[0041] As shown by lines A and B in Figure 1, in the polymer pyrolysis region of the first heating H1 under a nitrogen atmosphere, the polymer of the rubber composition is thermally decomposed and disappears. Specifically, the rubber composition is heated in a polymer combustion region of approximately 450°C to 550°C under a nitrogen atmosphere, and the polymer of the rubber composition disappears. At that time, the weight of the rubber composition decreases. The measured value (weight loss rate) by thermogravimetric analysis corresponding to this weight loss represents the weight ratio of the polymer contained in the rubber composition.

[0042] In the subsequent second heating H2, the carbon components contained in the reference rubber composition are burned and eliminated, as shown by line A in FIG. 1 . The carbon components contained in the reference rubber composition are primarily carbon black. The weight of the rubber composition is reduced by the combustion of the carbon components. The measured value (weight reduction rate) by thermogravimetric analysis corresponding to this weight reduction represents the weight ratio of the carbon components contained in the rubber composition. As shown in FIG. 1 , as the second heating H2 continues, ash remains.

[0043] On the other hand, as shown by line B in Figure 1, after the polymer has disappeared by the first heating H1, the used rubber composition still contains carbon precursors generated by thermal degradation of the polymer in the used rubber composition. Therefore, the weight loss rate of the used rubber composition after the first heating H1, i.e., the weight ratio of the polymer measured by thermogravimetric analysis for the used rubber composition, is smaller than the weight ratio of the polymer measured by thermogravimetric analysis for the reference rubber composition. This difference in the weight ratio of the polymers corresponds to the weight ratio (carbonization rate) of the carbon precursors generated by thermal degradation of the used rubber composition.

[0044] The carbon precursor of the used rubber composition is burned and consumed together with other carbon components during the second heating H2. At this time, the weight of the rubber composition decreases. The measured value (weight loss rate) by thermogravimetric analysis corresponding to this weight loss represents the total weight ratio of the carbon precursor and carbon components contained in the used rubber composition. Therefore, the weight ratio of the carbon component measured by thermogravimetric analysis for the used rubber composition is greater than the weight ratio of the carbon component measured by thermogravimetric analysis for the reference rubber composition. This difference in the weight ratio of the carbon component corresponds to the weight ratio of the carbon precursor generated by thermal degradation of the used rubber composition, and is the carbonization rate. Note that as the second heating H2 continues, ash remains.

[0045] As described above, by comparing the results of thermogravimetric analysis, the difference in the weight ratio of the carbon precursor generated in the rubber composition can be calculated. Specifically, by comparing the weight ratio of the polymer or the weight ratio of the carbon component measured by thermogravimetric analysis, the weight ratio or difference in the weight ratio of the carbon precursor generated in the rubber composition can be calculated. Therefore, by comparing the results of thermogravimetric analysis, the degree of thermal degradation of the rubber composition or the difference in the thermal degradation of the rubber composition can be determined. In the above example, the results of thermogravimetric analysis are compared between a reference rubber composition, i.e., a rubber composition that has not been thermally deteriorated, and a used rubber composition. The calculated difference in the weight ratio of the polymer or the weight ratio of the carbon component is the weight ratio (carbonization rate) of the carbon precursor generated in the used rubber composition due to the thermal degradation of the rubber composition. Meanwhile, by comparing the results of thermogravimetric analysis of used rubber compositions used in different environments, the degree of difference in thermal degradation can be determined. Furthermore, by comparing the results of thermogravimetric analysis between the reference rubber composition and the used rubber composition with the results of thermogravimetric analysis between the reference rubber composition and the other used rubber compositions, the difference in the degree of thermal degradation can be determined.

[0046] The present invention is based on the principle that, as described above, it is possible to detect the presence or absence of thermal degradation of a rubber composition and the degree of thermal degradation of the rubber composition by calculating the weight ratio of the carbon precursor or the difference in the weight ratio of the carbon precursor from a comparison of the weight ratio of the polymer or the weight ratio of the carbon component.

[0047] Hereinafter, a thermal degradation determination method according to an embodiment of the present invention will be specifically described.

[0048] As described above, the thermal degradation determination method according to this embodiment is a method for determining whether the thermal degradation of a rubber composition exceeds a predetermined level of degradation. The predetermined level of degradation, which serves as a threshold for this determination, is, for example, an acceptable level of thermal degradation that maintains the predetermined function of a component formed from the rubber composition. The rubber composition is, for example, a rubber body used in a gear damper or a torsional damper. Specifically, the thermal degradation determination method is used to determine the thermal degradation of a rubber ring 101 of a torsional damper 100 as shown in FIG. 2 . The rubber ring 101 is a rubber composition molded into a ring shape. The rubber composition forming the rubber ring 101 is, for example, hydrogenated nitrile rubber (HNBR). The torsional damper 100 is used, for example, as a component of a vehicle engine, and the ambient temperature in the operating environment is high. For this reason, portions of the rubber ring 101 exposed to heat are prone to thermal degradation, making it important to manage the thermal degradation of the rubber ring 101.

[0049] In the following description, as an example, a thermal degradation determination method is performed to determine whether the degree of thermal degradation of the rubber ring 101 of a torsional damper 100 that was installed in a vehicle exceeds the degree of degradation that is acceptable for the rubber ring 101 of the torsional damper 100. The degree of degradation that is acceptable for the rubber ring 101 of the torsional damper 100 is the degree of thermal degradation that allows the rubber ring 101 of the torsional damper 100 to maintain its desired function. The predetermined function of the rubber ring 101 is, for example, the function of causing the vibration ring 102 of the torsional damper 100 to vibrate at a predetermined natural frequency. Specifically, the thermal degradation determination method determines whether the ambient temperature of the usage environment in which the rubber ring 101 was used exceeds the upper limit of a predetermined temperature range. This predetermined temperature range is, for example, the temperature range specified in the specifications of the torsional damper 100. This threshold value of the upper limit of the specified temperature range is based on the premise that if the rubber ring 101 is used above the upper limit of the specified temperature range, the degree of thermal deterioration of the rubber ring 101 will exceed the degree of deterioration that is acceptable for the rubber ring 101 of the torsional damper 100.

[0050] The degree of thermal degradation of a rubber composition varies depending on the usage environment of the rubber composition. Specifically, the degree of thermal degradation of a rubber composition varies depending on the ambient temperature of the usage environment in which the rubber composition is used and the time it is used at that ambient temperature. Therefore, in the thermal degradation determination method according to this embodiment, first, a judgment criterion table for setting an acceptable degree of thermal degradation, i.e., a threshold value, is generated. This judgment criterion table is specifically a usage environment / carbonization rate table, which associates the usage environment (temperature and time) of the rubber composition with the carbonization rate (weight ratio of carbon precursor) of the rubber composition corresponding to that usage environment. The carbonization rate of the rubber composition corresponding to the usage environment (temperature and time) of the rubber composition is the weight ratio of the carbon precursor generated by thermal degradation of the rubber composition used in that usage environment to the weight of the entire rubber composition. The usage environment / carbonization rate table is, for example, a table listing the usage environment (temperature and time) of the rubber composition and the carbonization rate corresponding to that usage environment, and is also information that makes it possible to know, for example, the usage environment (temperature and time) of the rubber composition and the carbonization rate corresponding to that usage environment.

[0051] FIG. 3 is a diagram illustrating a usage environment / carbonization rate table generated by the thermal degradation determination method according to this embodiment. As shown in FIG. 3 , the usage environment / carbonization rate table shows, for example, the relationship between usage time (h) and carbonization rate (wt%) at the ambient temperature of a specific usage environment. As described above, the carbonization rate (wt%) indicates the weight ratio (wt%) of the carbon precursor generated by thermal degradation of the rubber composition. As an example, FIG. 3 shows the relationship between usage time (h) and carbonization rate (wt%) when the ambient temperature of the usage environment is 110°C, 130°C, 150°C, and 170°C. As shown in FIG. 3 , at each ambient temperature, the usage time (h) and the carbonization rate (wt%) are plotted as straight lines Th1, Th2, Th3, and Th4, each having a slope. Furthermore, the higher the ambient temperature, the greater the slope of the line plotting usage time (h) and carbonization rate (wt%).

[0052] The usage environment / carbonization rate table is generated by performing the thermogravimetric analysis shown in Figure 1 on the rubber rings 101 (reference rubber compositions) of multiple torsional dampers 100. Specifically, rubber rings 101 of the torsional dampers 100 that have been used for different periods of time at the ambient temperature of each usage environment are prepared, and thermogravimetric analysis is performed on the multiple prepared rubber rings 101 to obtain the weight ratio (wt%) of the polymer or the weight ratio (wt%) of the carbon component in the multiple rubber rings 101. Meanwhile, thermogravimetric analysis is performed on the rubber rings 101 of unused torsional dampers 100 or the rubber composition that forms the rubber rings 101 to obtain the weight ratio (wt%) of the polymer or the weight ratio (wt%) of the carbon component. In this way, the weight ratio (wt%) of the polymer or the weight ratio (wt%) of the carbon component measured by thermogravimetric analysis for a plurality of used rubber compositions (used rubber rings 101) that have been used for different periods of time at each of a plurality of ambient temperatures in a plurality of use environments is compared with the weight ratio (wt%) of the polymer or the weight ratio (wt%) of the carbon component measured by thermogravimetric analysis for a reference rubber composition (an unused rubber ring 101 or its rubber composition), and the carbonization rate of each used rubber composition is calculated. Specifically, the carbonization rate of each used rubber composition is calculated by subtracting the weight ratio of the polymer of each used rubber composition from the weight ratio of the polymer of the reference rubber composition, or by subtracting the weight ratio of the carbon component of the reference rubber composition from the weight ratio of the carbon component of each used rubber composition.

[0053] For example, the carbonization rate of each used rubber composition is calculated as shown in Fig. 4. That is, the carbonization rates (wt%) of three rubber rings 101 used in a usage environment where the ambient temperature of the usage environment is 110°C and the usage times are 120 hours, 480 hours, and 1008 hours, the carbonization rates (wt%) of three rubber rings 101 used in a usage environment where the ambient temperature of the usage environment is 130°C and the usage times are 120 hours, 480 hours, and 1008 hours, the carbonization rates (wt%) of three rubber rings 101 used in a usage environment where the ambient temperature of the usage environment is 150°C and the usage times are 120 hours, 480 hours, and 1008 hours, and the carbonization rates (wt%) of three rubber rings 101 used in a usage environment where the ambient temperature of the usage environment is 170°C and the usage times are 120 hours, 480 hours, and 1008 hours are calculated. Based on this calculated carbonization rate (wt%), it is possible to obtain straight lines Th1 to Th4 shown in Figure 3, which show the relationship between the usage time (h) and the carbonization rate (wt%) when the ambient temperature of the usage environment is 110°C, 130°C, 150°C, and 170°C, respectively. Note that multiple rubber rings 101 used in each usage environment may be prepared instead of one. Also, multiple unused rubber rings 101 may be prepared instead of one. In this case, the carbonization rate calculated for the rubber ring 101 used in each usage environment may be a value based on multiple carbonization rates, such as an average value of the multiple carbonization rates.

[0054] From the use environment / carbonization rate table obtained as described above, an allowable degree of thermal degradation (threshold value) can be set depending on the rubber composition to be determined by the thermal degradation determination method. For example, if the degree of thermal degradation due to use in an ambient temperature of the use environment higher than 130°C is not allowable for the rubber ring 101 of the torsional damper 100, as shown in Figure 5, the relationship line Th2 between the use time (h) and the carbonization rate (wt%) at an ambient temperature of the use environment of 130°C is set as the threshold for determining whether the degree of thermal degradation is allowable. In this case, the rubber ring 101 whose carbonization rate falls within region R1, which is a region where the carbonization rate is higher than the relationship line Th2 between the use time (h) and the carbonization rate (wt%) at an ambient temperature of the use environment of 130°C, is determined to be a rubber ring 101 experiencing an unallowable degree of thermal degradation. On the other hand, when the ambient temperature of the usage environment is 130°C, a rubber ring 101 having a carbonization rate falling within region R2, which is a region where the carbonization rate is equal to or less than the relationship line Th2 between usage time (h) and carbonization rate (wt%), is judged to be a rubber ring 101 that has undergone an acceptable level of thermal deterioration.

[0055] The above-described usage environment / carbonization rate table provides a relationship line between usage time (h) and carbonization rate (wt%) at ambient temperatures (°C) in a plurality of usage environments. However, the usage environment / carbonization rate table may provide a relationship line between usage time (h) and carbonization rate (wt%) at an ambient temperature (°C) in a single usage environment. For example, if the allowable degree of thermal degradation is fixed depending on the rubber composition to be assessed by the thermal degradation assessment method, the usage environment / carbonization rate table may provide a relationship line between usage time (h) and carbonization rate (wt%) at an ambient temperature (°C) in a single usage environment. For example, in the above example, the usage environment / carbonization rate table may provide a relationship line Th2 between usage time (h) and carbonization rate (wt%) when the ambient temperature of the usage environment is 130°C. In the case of the usage environment / carbonization rate table described above, which provides a relationship line between usage time (h) and carbonization rate (wt%) for each of the ambient temperatures (°C) of multiple usage environments, a threshold value for determining whether or not the degree of thermal degradation is acceptable can be selected and set depending on the type of rubber composition to be assessed by the thermal degradation assessment method.

[0056] In the thermal degradation assessment process, the threshold used to determine whether the degree of thermal degradation is acceptable is not limited to the relationship between the usage time (h) and the carbonization rate (wt%) at the ambient temperature of a specific usage environment, as described above. For example, the threshold used to determine whether the degree of thermal degradation is acceptable in the thermal degradation assessment process may be a specific carbonization rate. Specifically, for example, a specific carbonization rate (13 wt% in the illustrated example) as shown by line Th5 in FIG. 3 may be used as the threshold. In this case, if the carbonization rate of the used rubber ring 101 is greater than this specific carbonization rate, the used rubber ring 101 is determined to have experienced an unacceptable level of thermal degradation. On the other hand, if the carbonization rate of the used rubber ring 101 is equal to or less than this specific carbonization rate, the used rubber ring 101 is determined to have experienced an acceptable level of thermal degradation.

[0057] Furthermore, the threshold value for distinguishing whether the degree of thermal degradation is acceptable or not may not be a straight line as described above, but may be various threshold values ​​such as a line enclosing an area, corresponding to the rubber composition to be judged and corresponding to the physical properties of the rubber composition required for products, etc. made from the rubber composition. In this case, it is preferable that the usage environment / carbonization rate table has information on the carbonization rates of many rubber compositions (reference rubber compositions) used in many different usage environments.

[0058] In addition, in the thermal degradation assessment process, in addition to the carbonization rate, the time the rubber composition to be assessed has been used in the usage environment may be compared with a threshold value to determine whether the degree of thermal degradation is acceptable. In this case, the determination of thermal degradation can be made more accurately. For example, in the above example, as shown in FIG. 5 , if the carbonization rate detected from the rubber ring 101 (used rubber ring P1) used for 600 hours is 5 wt %, and the carbonization rate detected from the rubber ring 101 (used rubber ring P2) used for 2000 hours is 5 wt %, the used rubber ring P2 can be determined to be a rubber ring 101 that has undergone an acceptable level of thermal degradation, while the used rubber ring P1 can be determined to be a rubber ring 101 that has undergone an unacceptable level of thermal degradation, based on the threshold value of line Th2. In this case, for example, the used rubber ring P2 is experiencing a slower rate of thermal degradation than the used rubber ring P1, and the used rubber ring P2 can be determined to be a rubber ring 101 that has undergone an acceptable level of thermal degradation.

[0059] The rubber ring 101 used to create the usage environment / carbonization rate table is, for example, a sample piece of the rubber ring 101. Specifically, for example, the sample piece is obtained by cutting a portion of a predetermined size from one of the portions of the torsional damper 100 at both ends of the rubber ring 101 that are exposed to the outside.

[0060] The heating process in the thermogravimetric analysis for creating the usage environment / carbonization rate table is, for example, as follows: In the first heating H1, the temperature is increased from 35°C to 600°C at a rate of 10°C / min, maintained at that state for 5 minutes, and then decreased to 400°C at a rate of 30°C / min. In the subsequent second heating H2, the temperature is increased from 400°C to 1000°C at a rate of 20°C / min.

[0061] The thermal degradation determination method according to this embodiment calculates the carbonization rate by performing the thermogravimetric analysis shown in Figure 1 on the rubber composition to be determined, and then determines the degree of thermal degradation using the calculated carbonization rate and the above-mentioned usage environment / carbonization rate table. Below, the thermal degradation determination method according to this embodiment will be specifically described using the thermal degradation determination method for the rubber ring 101 of the torsional damper 100, whose usage environment is unknown, as an example.

[0062] The thermal degradation assessment method first performs a carbonization rate detection process to determine the carbonization rate of a rubber ring 101 in which a carbon precursor has been generated due to thermal degradation. First, the carbonization rate detection process for polymer components will be described. In the carbonization rate detection process, the rubber ring 101 (hereinafter referred to as the used rubber ring 101), which is the used rubber composition to be assessed, is subjected to the above-described thermogravimetric analysis. This thermogravimetric analysis measures the polymer weight ratio, carbon component weight ratio, and ash weight ratio of the used rubber ring 101. Next, the polymer weight ratio of the used rubber ring 101 is subtracted from the polymer weight ratio of an unused rubber ring 101 (hereinafter referred to as the reference rubber ring 101), which is the reference rubber composition, to calculate the difference in polymer weight ratio. The polymer weight ratio of the reference rubber ring 101 can be determined using values ​​from a previously created usage environment / carbonization rate table. The polymer weight ratio of the reference rubber ring 101 may also be determined during the carbonization rate detection process. As described above, the difference in the calculated weight ratio of the polymer is the carbonization rate of the used rubber ring 101, and is the weight ratio of the carbon precursor generated by thermal degradation of the used rubber ring 101.

[0063] In this way, in the carbonization rate detection process for polymers, the difference in weight ratio before and after thermal degradation is detected for the weight ratio of the polymer, which is a component of the used rubber ring 103 whose weight ratio has changed due to thermal degradation. Note that in the carbonization rate detection process for polymers, the thermogravimetric analysis may be terminated when the weight ratio of the polymer in the used rubber ring 101 is measured.

[0064] Next, the carbonization rate detection process targeting the carbon component will be described. As described above, the carbonization rate of the used rubber composition can be obtained based on either the weight ratio of the polymer or the weight ratio of the carbon component. Therefore, the carbonization rate detection process may be performed targeting the carbon component rather than the polymer. In the carbonization rate detection process targeting the carbon component, the used rubber ring 101 is first subjected to the above-described thermogravimetric analysis. This thermogravimetric analysis measures the polymer weight ratio, carbon component weight ratio, and ash weight ratio of the used rubber ring 101. Next, the carbon component weight ratio of the reference rubber ring 101 is subtracted from the carbon component weight ratio of the used rubber ring 101 to calculate the difference in the carbon component weight ratio. The carbon component weight ratio of the reference rubber ring 101 can be determined using a value in a previously created usage environment / carbonization rate table. The carbon component weight ratio of the reference rubber ring 101 may also be measured in the carbonization rate detection process. As described above, the difference in the calculated weight ratio of the carbon component is the carbonization rate of the used rubber ring 101, and is the weight ratio of the carbon precursor generated by thermal degradation of the used rubber ring 101.

[0065] In this way, in the carbonization rate detection process targeting the carbon component, the difference in weight ratio before and after thermal degradation is detected for the carbon component, which is a component of the used rubber ring 103 whose weight ratio has changed due to thermal degradation. Note that in the carbonization rate detection process targeting the carbon component, the thermogravimetric analysis may be terminated when the weight ratio of the carbon component in the used rubber ring 101 is measured.

[0066] Next, a thermal degradation determination process is performed to determine whether the thermal degradation of the used rubber ring 101 exceeds a predetermined level based on the carbonization rate of the used rubber ring 101 calculated in the carbonization rate detection process and the use environment / carbonization rate table. As described above, the predetermined level of thermal degradation is a level of thermal degradation that maintains the predetermined function of the rubber ring 101. For example, the predetermined function of the rubber ring 101 is the function of causing the vibrating body 102 in the torsional damper 100 to vibrate at a predetermined natural frequency. As an example, it is assumed that the degree of thermal degradation of the rubber ring 101 of the torsional damper 100 due to use in an ambient temperature of the use environment higher than 130°C is not acceptable (see threshold value Th2 in FIG. 5 ).

[0067] In the thermal degradation determination process, the usage environment / carbonization rate table is referenced to determine whether the carbonization rate of the used rubber ring 101 calculated in the carbonization rate detection process is a carbonization rate that corresponds to allowable thermal degradation. Specifically, it is determined whether the carbonization rate of the used rubber ring 101 is included in region R1, which is higher than the relationship line Th2 between the usage time (h) and the carbonization rate (wt%) when the ambient temperature of the usage environment is 130°C, or whether it is included in region R2, which is the carbonization rate equal to or lower than the relationship line Th2 between the usage time (h) and the carbonization rate (wt%) when the ambient temperature of the usage environment is 130°C, as shown in Figure 5.

[0068] In the thermal degradation determination process, if the carbonization rate of the used rubber ring 101 falls within region R1, the used rubber ring 101 is determined to be a rubber ring 101 that has experienced an unacceptable level of thermal degradation. On the other hand, if the carbonization rate of the used rubber ring 101 falls within region R2, the used rubber ring 101 is determined to be a rubber ring 101 that has experienced an acceptable level of thermal degradation.

[0069] In the thermal degradation assessment process, the carbonization rate corresponding to the allowable thermal degradation that serves as the threshold is not limited to the relationship lines Th1 to Th4 between the usage time (h) and the carbonization rate (wt%) at the ambient temperature of a specific usage environment. For example, in the thermal degradation assessment process, the carbonization rate corresponding to the allowable thermal degradation that serves as the threshold may be a specific carbonization rate. Specifically, for example, a specific carbonization rate (13 wt% in the illustrated example) as shown by line Th5 in FIG. 3 may be used as the threshold. In this case, if the carbonization rate of the used rubber ring 101 is greater than this specific carbonization rate, the used rubber ring 101 is determined to have experienced an unacceptable level of thermal degradation. On the other hand, if the carbonization rate of the used rubber ring 101 is equal to or less than this specific carbonization rate, the used rubber ring 101 is determined to have experienced an allowable level of thermal degradation.

[0070] Next, a thermal degradation determination process for executing the above-described thermal degradation determination method will be described below. Fig. 6 is a flowchart of the thermal degradation determination process for executing the thermal degradation determination method.

[0071] In the thermal degradation assessment process, first, a carbonization rate detection process is performed (step S1). FIG. 7 is a flowchart of the carbonization rate detection process performed in the thermal degradation assessment process. In the carbonization rate detection process, as shown in FIG. 7, first, the above-described thermogravimetric analysis is performed on the used rubber ring 101 (step S11), and the polymer weight ratio, carbon component weight ratio, and ash weight ratio of the used rubber ring 101 are measured. Next, the carbonization rate of the used rubber ring 101 is calculated (step S12). In step S12, the polymer weight ratio of the used rubber ring 101 is subtracted from the polymer weight ratio of the reference rubber ring 101 to calculate the difference in polymer weight ratio. This calculated difference in polymer weight ratio is the carbonization rate of the used rubber ring 101. Alternatively, in step S12, the difference in carbon component weight ratio may be calculated by subtracting the carbon component weight ratio of the reference rubber ring 101 from the carbon component weight ratio of the used rubber ring 101. In this case, the difference between the calculated weight ratios of the carbon components is the carbonization rate of the used rubber ring 101. In step S12, the polymer weight ratio or the carbon component weight ratio of the reference rubber ring 101 is obtained by referring to the usage environment / carbonization rate table. Once the carbonization rate of the used rubber ring 101 is calculated in this way, the carbonization rate detection process ends.

[0072] Next, in the thermal degradation determination process, as shown in Fig. 6, it is determined whether the carbonization rate of the used rubber ring 101 calculated by the carbonization rate detection process corresponds to an acceptable level of thermal degradation (step S2). In step S2, if the carbonization rate of the used rubber ring 101 is greater than the acceptable level of thermal degradation, that is, if the carbonization rate of the used rubber ring 101 is greater than the threshold value (Yes in step S2), the used rubber ring 101 is determined to be a rubber ring 101 that has experienced an unacceptable level of thermal degradation (step S3), and the thermal degradation determination process is terminated. On the other hand, if the carbonization rate of the used rubber ring 101 is equal to or less than the threshold value (No in step S2), the used rubber ring 101 is determined to be a rubber ring 101 that has experienced an acceptable level of thermal degradation (step S4), and the thermal degradation determination process is terminated.

[0073] As described above, the thermal degradation determination method according to the present embodiment makes it possible to determine whether the thermal degradation of a used rubber composition is at an acceptable level. Furthermore, the thermal degradation determination method according to the present embodiment makes it possible to determine the degree of thermal degradation of a used rubber composition with higher accuracy than conventional evaluations using changes in hardness of the rubber composition or evaluations using Fourier Transform-Infrared Spectroscopy (FT-IR).

[0074] Furthermore, according to the thermal degradation determination method of this embodiment, various thresholds can be set as the threshold for determining whether or not thermal degradation is tolerable, and the thermal degradation of the used rubber composition can be determined from various perspectives.

[0075] Next, a thermal history estimation method according to an embodiment of the present invention will be specifically described.

[0076] The thermal history estimation method according to this embodiment, like the thermal degradation determination method according to this embodiment described above, detects the carbonization rate of the used rubber composition (used rubber composition), which is the subject of thermal history estimation, and, like the thermal degradation determination method according to this embodiment described above, refers to a usage environment / carbonization rate table (see Figures 3 and 4) prepared in advance to estimate the ambient temperature of the usage environment in which the used rubber composition was used based on the detected carbonization rate of the used rubber composition.

[0077] Similar to the thermal deterioration determination method described above, the thermal history estimation method will be described below, using the rubber ring 101 used in the torsional damper 100 shown in FIG. 2 as the subject of thermal history estimation. The ambient temperature of the usage environment of the used rubber ring 101, the subject of thermal history estimation, is unknown. Furthermore, the usage time of the used rubber ring 101, the subject of thermal history estimation, is known. The usage time of the used rubber ring 101, the subject of thermal history estimation, is not known, and may be a time estimated from the vehicle's travel distance, average speed, etc. Hereinafter, both usage times will be simply referred to as usage time.

[0078] In the thermal history estimation method, first, a usage environment / carbonization rate table (see FIGS. 3 and 4) is created, similarly to the thermal deterioration determination method described above. Next, similarly to the thermal deterioration determination method described above, a carbonization rate detection process is performed on the used rubber ring 101, and the carbonization rate, which is the weight ratio of carbon precursors generated by thermal deterioration of the used rubber ring 101, is detected.

[0079] The thermal history estimation method then executes a thermal history estimation process. In the thermal history estimation process, the detected relationship between the carbonization rate of the used rubber ring 101 and usage time is compared with relationship lines (Th1 to Th4) between usage time (h) and carbonization rate (wt%) at ambient temperatures (°C) of multiple usage environments obtained from a usage environment / carbonization rate table, and a relationship line between usage time (h) and carbonization rate (wt%) that approximates the detected relationship between the carbonization rate of the used rubber ring 101 and usage time is identified. Then, the ambient temperature of the usage environment of this identified relationship line between usage time (h) and carbonization rate (wt%) is estimated to be the ambient temperature of the usage environment of the used rubber ring 101.

[0080] 3, if the used rubber ring 101 is the used rubber ring P3 that has been used for 1200 hours and has a detected carbonization rate of 15 wt%, referring to the usage environment / carbonization rate table, it can be seen that the relationship between the usage time and the carbonization rate of the used rubber ring P3 is close to the relationship line Th3 between the usage time and the carbonization rate when the ambient temperature of the usage environment is 150° C. Therefore, the ambient temperature of the usage environment of the used rubber ring P3 is estimated to be 150° C., which is the ambient temperature of the usage environment of the relationship line Th3.

[0081] Next, a thermal history estimation process for executing the thermal history estimation method will be described with reference to FIG.

[0082] In the thermal history estimation process, first, the carbonization rate detection process shown in Fig. 7 is performed (step S21). That is, first, thermogravimetric analysis is performed on the used rubber ring 101 (step S11), and the weight ratio of the polymer, the weight ratio of the carbon component, and the weight ratio of the ash of the used rubber ring 101 are measured. Next, the carbonization rate of the used rubber ring 101 is calculated (step S12). Note that in step S12, as in the case of the thermal deterioration determination process described above, only the weight ratio of the polymer may be measured, or only the weight ratio of the polymer and the weight ratio of the carbon component may be measured.

[0083] 8, the thermal history estimation process refers to the usage environment / carbonization rate table to identify the ambient temperature of the usage environment that depicts a relationship line between usage time and carbonization rate that has a relationship similar to the relationship between the carbonization rate of the used rubber ring 101 calculated by the carbonization rate detection process and the usage time of the used rubber ring 101 (step S22). Once the ambient temperature of the usage environment is identified, the identified ambient temperature of the usage environment is estimated to be the ambient temperature of the usage environment of the used rubber ring 101 (step S23), and the thermal history estimation process ends.

[0084] As described above, the thermal history estimation method according to the present embodiment makes it possible to estimate the ambient temperature of the environment in which a used rubber composition is used. Furthermore, the thermal history estimation method according to the present embodiment makes it possible to determine the degree of thermal degradation of a used rubber composition more accurately than conventional evaluations using changes in hardness of the rubber composition or evaluations using FT-IR, and therefore makes it possible to accurately estimate the thermal history of a used rubber composition.

[0085] Next, a thermal degradation determining device for executing the above-described thermal degradation determining method will be described. Fig. 9 is a block diagram showing the functional configuration of a thermal degradation determining device 1 for executing the thermal degradation determining method.

[0086] As shown in Figure 9, the thermal degradation determination device 1 has a thermal degradation determination processing unit 10 that executes the above-mentioned thermal degradation determination process. The thermal degradation determination processing unit 10 has a carbonization rate detection processing unit 11 that executes the above-mentioned carbonization rate detection process. The thermal degradation determination processing unit 10 also has a carbonization rate determination processing unit 12. The carbonization rate determination processing unit 12 determines whether the carbonization rate of the rubber composition used is at an acceptable level for thermal degradation, that is, it has a functional configuration that executes steps S2 to S4 of the above-mentioned thermal degradation determination process. The thermal degradation determination device 1 also has a usage environment / carbonization rate table creation unit 13 that creates the above-mentioned usage environment / carbonization rate table.

[0087] The carbonization rate detection processing unit 11 controls, for example, a thermogravimetric analyzer that performs thermogravimetric analysis to detect the carbonization rate of the rubber composition. The thermal degradation determination device 1 may or may not include a thermogravimetric analyzer. If the thermal degradation determination device 1 does not include a thermogravimetric analyzer, the thermal degradation determination device 1 is, for example, capable of being controllably connected to a thermogravimetric analyzer.

[0088] The thermal degradation determination device 1 also has a control unit 14 and a memory unit 15. The control unit 14 is configured with an information processing device capable of executing computer programs, such as an MCU (Micro Controller Unit) including a processor such as a CPU (Central Processing Unit) and a memory unit. The memory unit included in the control unit 14 is realized by a known memory unit (storage medium), such as a ROM, RAM, or flash memory. The control unit 14 is a functional configuration that comprehensively controls each functional configuration of the thermal degradation determination device 1. The memory unit 15 stores a usage environment / carbonization rate table and various data. The thermal degradation determination device 1 also has various interfaces, such as an operation unit 16.

[0089] The thermal degradation determination device 1 has the above-described configuration and executes the above-described thermal degradation determination method. The thermal degradation determination device 1 may constitute a device or may constitute an IC chip that is mounted on another device and executes the above-described thermal degradation determination method.

[0090] Next, a thermal history estimation device for executing the thermal history estimation method will be described. Fig. 10 is a block diagram showing the functional configuration of a thermal history estimation device 2 for executing the thermal history estimation method.

[0091] As shown in FIG. 10 , the thermal history estimation device 2 includes a thermal history estimation processing unit 20 that executes the thermal history estimation process described above. The thermal history estimation processing unit 20 includes a carbonization rate detection processing unit 21 that executes the carbonization rate detection process described above. The thermal history estimation processing unit 20 also includes an ambient temperature estimation processing unit 22. The thermal history estimation device 2 also includes a usage environment / carbonization rate table creation unit 23 that creates the usage environment / carbonization rate table described above. The ambient temperature estimation processing unit 22 references the usage environment / carbonization rate table to identify the ambient temperature of the usage environment that draws a relationship line between usage time and carbonization rate that has a relationship similar to the relationship between the carbonization rate of the used rubber composition calculated by the carbonization rate detection process and the usage time of the used rubber composition, and estimates the ambient temperature of this identified usage environment as the ambient temperature of the usage environment of the used rubber composition. In other words, the ambient temperature estimation processing unit 22 is functionally configured to execute steps S22 and S23 of the thermal history estimation process described above.

[0092] The carbonization rate detection processing unit 21 controls, for example, a thermogravimetric analyzer that performs thermogravimetric analysis to detect the carbonization rate of the rubber composition. The thermal history estimation device 2 may or may not have a thermogravimetric analyzer. When the thermal history estimation device 2 does not have a thermogravimetric analyzer, the thermal history estimation device 2 is, for example, capable of being controllably connected to a thermogravimetric analyzer.

[0093] The thermal history estimation device 2 also has a control unit 24 and a memory unit 25. The control unit 24 is configured with an information processing device capable of executing computer programs, such as an MCU (Micro Controller Unit) including a processor such as a CPU (Central Processing Unit) and a memory unit. The memory unit included in the control unit 24 is realized by a known memory unit (storage medium), such as a ROM, RAM, or flash memory. The control unit 24 is a functional configuration that comprehensively controls each functional configuration of the thermal history estimation device 2. The memory unit 25 stores a usage environment / carbonization rate table and various data. The thermal history estimation device 2 also has various interfaces, such as an operation unit 26.

[0094] The thermal history estimation device 2 has the above-described configuration and executes the above-described thermal history estimation method. The thermal history estimation device 2 may constitute a device or may constitute an IC chip that is mounted on another device and executes the above-described thermal history estimation method.

[0095] Although the present invention has been described above through the above embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It will be apparent to those skilled in the art that various modifications and improvements can be made to the above embodiments. It is clear from the claims that such modifications and improvements can also be included within the technical scope of the present invention.

[0096] The above-described embodiments are intended to facilitate understanding of the present invention and are not intended to limit the scope of the present invention. Furthermore, the above-described embodiments do not limit the scope of the present invention, and the present invention may include any and all applications. The components of the above-described embodiments, as well as their arrangement, materials, conditions, shape, size, etc., are not limited to those illustrated and may be modified as appropriate. For example, the present invention includes differences that arise during implementation due to manufacturing tolerances, etc. Furthermore, components illustrated in different embodiments may be partially substituted or combined within the scope of technical inconsistency. Furthermore, the various configurations may be selectively combined as appropriate to achieve at least some of the above-described problems and effects.

[0097] 1 Thermal deterioration determination device, 2 Thermal history estimation device, 10 Thermal deterioration determination processing unit, 11 Carbonization rate detection processing unit, 12 Carbonization rate determination processing unit, 13 Usage environment / carbonization rate table creation unit, 14 Control unit, 15 Memory unit, 16 Operation unit, 20 Thermal history estimation processing unit, 21 Carbonization rate detection processing unit, 22 Ambient temperature estimation processing unit, 23 Usage environment / carbonization rate table creation unit, 24 Control unit, 25 Memory unit, 26 Operation unit, 100 Torsional damper, 101 Rubber ring, 102 Vibration ring, H1 First heating, H2 Second heating, P1, P2, P3 Used rubber ring, Th1, Th2, Th3, Th4 Relationship line (threshold), Th5 Line (threshold)

Claims

1. A thermal degradation determination method for determining thermal degradation of a rubber composition, comprising a thermal degradation determination process for determining whether the thermal degradation of the rubber composition exceeds a predetermined level, wherein the thermal degradation determination process compares the weight ratio of a carbon precursor in the rubber composition with a set threshold value to determine whether the thermal degradation of the rubber composition exceeds the predetermined level.

2. A thermal degradation determination method, wherein the threshold value is a value based on the weight ratio of a carbon precursor in a reference rubber composition, which is a rubber composition used under one or more predetermined thermal degradation conditions, and the thermal degradation determination process determines that the thermal degradation of the rubber composition exceeds the predetermined degree of thermal degradation when the weight ratio of the carbon precursor in the rubber composition is greater than the threshold value.

3. A thermal degradation determination method according to claim 1, further comprising a carbonization rate detection process for determining the weight ratio of carbon precursors in the rubber composition, wherein the carbonization rate detection process determines the weight ratio of the components of the rubber composition by comparing it with the weight ratio of the components of a reference rubber composition that is an unused rubber composition.

4. The method for determining thermal degradation according to claim 3, wherein the components of the rubber composition and the reference rubber composition are polymers.

5. The method for determining thermal degradation according to claim 4, wherein the weight ratio of the carbon precursor in the rubber composition is calculated by subtracting the weight ratio of the polymer in the rubber composition from the weight ratio of the polymer in the reference rubber composition.

6. The method for determining thermal degradation according to claim 3, wherein the components of the rubber composition and the reference rubber composition are carbon components.

7. The method for determining thermal degradation according to claim 6, wherein the weight ratio of the carbon precursor in the rubber composition is calculated by subtracting the weight ratio of the carbon component in the reference rubber composition from the weight ratio of the carbon component in the rubber composition.

8. The method for determining thermal degradation according to claim 5, wherein the weight ratio of the polymers is measured by thermogravimetric analysis.

9. The method for determining thermal deterioration according to claim 7, wherein the weight ratio of the carbon component is measured by thermogravimetric analysis.

10. The method for determining thermal degradation according to claim 1, wherein the weight ratio of the carbon precursor in the reference rubber composition is set in advance.

11. A method for determining thermal degradation according to claim 2, comprising preparing a plurality of thermally degraded rubber compositions, each of which is a plurality of rubber compositions used under different thermal degradation conditions, and selecting the reference rubber composition from among the plurality of thermally degraded rubber compositions.

12. The thermal degradation determination method according to claim 1, wherein the threshold value is a predetermined weight ratio.

13. The thermal degradation determination method according to claim 2, wherein the predetermined thermal degradation conditions include at least one of temperature and time.

14. A thermal history estimation method for estimating the thermal history of a rubber composition, comprising a thermal history estimation process for identifying the thermal history of a used rubber composition, which is the rubber composition that has been used, and the thermal history estimation process identifies the temperature at which the used rubber composition was used based on the weight ratio of a carbon precursor in the used rubber composition.

15. A thermal history estimation method according to claim 14, wherein the weight ratio of the carbon precursor in a reference rubber composition, which is a rubber composition used under one or more predetermined thermal degradation conditions, and the predetermined thermal degradation conditions are prepared in advance, the predetermined thermal degradation conditions being the time and temperature at which the reference rubber composition was used, and the thermal history estimation process compares the weight ratio of the carbon precursor in the used rubber composition and the time at which the used rubber composition was used with the weight ratio of the carbon precursor in the reference rubber composition and the time among the predetermined thermal degradation conditions to identify the temperature at which the used rubber composition was used.

16. The method for estimating thermal history according to claim 15, wherein the time during which the rubber composition has been used is an estimated value.

17. A thermal history estimation method according to claim 14, further comprising a carbonization rate detection process for determining the weight ratio of carbon precursors in the rubber composition, wherein the carbonization rate detection process determines the weight ratio of the components of the rubber composition by comparing it with the weight ratio of the components of a reference rubber composition, which is an unused rubber composition.

18. The thermal history estimation method according to claim 17, wherein the components of the rubber composition and the reference rubber composition are polymers.

19. The thermal history estimation method according to claim 18, wherein the weight ratio of the carbon precursor in the rubber composition is calculated by subtracting the weight ratio of the polymer in the rubber composition from the weight ratio of the polymer in the reference rubber composition.

20. The thermal history estimation method according to claim 17, wherein the components of the rubber composition and the reference rubber composition are carbon components.

21. The method for estimating thermal history according to claim 20, wherein the weight ratio of the carbon precursor in the rubber composition is calculated by subtracting the weight ratio of the carbon component in the reference rubber composition from the weight ratio of the carbon component in the rubber composition.

22. The method for estimating thermal history according to claim 19, wherein the weight ratio of the polymer is measured by thermogravimetric analysis.

23. The thermal history estimation method according to claim 21, wherein the weight ratio of the carbon component is measured by thermogravimetric analysis.

24. A thermal degradation determination device for determining thermal degradation of a rubber composition, comprising a thermal degradation determination processing unit for determining whether the thermal degradation of the rubber composition exceeds a predetermined degree of thermal degradation, wherein the thermal degradation determination processing unit compares the weight ratio of a carbon precursor in the rubber composition with a set threshold value to determine whether the thermal degradation of the rubber composition exceeds the predetermined degree of thermal degradation.

25. A thermal history estimation device for estimating the thermal history of a rubber composition, comprising a thermal history estimation processing unit that identifies the thermal history of a used rubber composition, which is the rubber composition that has been used, and the thermal history estimation processing unit identifies the temperature at which the used rubber composition was used based on the weight ratio of a carbon precursor in the used rubber composition.

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