Method for predicting elongation life of resin members

Abstract

To provide a method for predicting elongation life of resin members in a very short time and with a simple process.SOLUTION: A method for predicting elongation life of resin members is a method for predicting the elongation life of resin members containing a resin and an antioxidant, which, for the resin members, includes the steps of: performing treatment using a chemical luminescence method at three or more mutually different temperatures for the resin members to identify an oxidation induction time at each temperature; and predicting the elongation life of the resin members at a specific temperature based on results of plotting each temperature and each oxidation induction time on an Arrhenius plot.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for predicting the elongation life of a resin member. [Background technology]

[0002] It is known that heat and light can break the molecular bonds of resins, causing them to deteriorate and resulting in the loss of their inherent properties. For example, resin materials are used in the outer sheath of insulated electric wires and the insulating members placed at the ends of insulated electric wires (collectively referred to as "insulating members" in this specification), and it is known that these materials also lose their flexibility (elongation) over time. Insulated electric wires are often used in environments where it is difficult to frequently check their performance or replace them. Therefore, it is very important to predict the period until an insulating member no longer exhibits sufficient elongation (also referred to as "elongation life" in this specification).

[0003] As a method for evaluating the degradation of various resin products, there is a method for analyzing actually deteriorated resin products and determining their lifespan. Also, a method for determining the lifespan of insulating materials for insulated electric wires using gas chromatography-mass spectrometry has been proposed (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5760817 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the method of analyzing the elongation of actually deteriorated resin products has the problem that it takes a very long time to evaluate. Furthermore, in evaluation methods using accelerated deterioration, the crystallinity of the resin may change due to the heat applied during the accelerated thermal deterioration treatment or during analysis. Therefore, it is necessary to analyze the elongation taking into account the change in the crystallinity of the resin, which can make the evaluation very complicated. Therefore, a main object of the present invention is to provide a method for predicting the elongation life of a resin member in a very short time without performing complicated processing. [Means for solving the problem]

[0006] In order to solve the above problem, according to one aspect of the present invention, A method for predicting an extended life of a resin member containing a resin and an antioxidant, a step of treating the resin workpiece by a chemiluminescence method at three or more temperatures different from each other, and specifying an oxidation induction time at each of the temperatures; a step of predicting an elongation life of the resin member at a specific temperature from an Arrhenius plot result of each of the temperatures and each of the oxidation induction times; A method for predicting the elongation life of a resin member is provided, including: [Effects of the Invention]

[0007] According to the present invention, a method for predicting the elongation life of a resin member is provided, which can be performed in a very short time and with simple processing. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a flowchart showing the flow of a method for predicting the elongation life of a resin member according to an embodiment of the present invention. [Figure 2] 1 is a schematic graph for explaining changes in luminescence intensity by chemiluminescence. [Figure 3]1 is a graph obtained by linearly approximating an Arrhenius plot of the temperatures at which chemiluminescence was performed and the corresponding oxidation induction times in Example 1. [Figure 4] 4 is a graph obtained by linearly extrapolating the Arrhenius plot shown in FIG. 3. [Figure 5] 1 is a graph obtained by linearly extrapolating an Arrhenius plot of the temperature and oxidation induction time at which the chemiluminescence method was performed in Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0009] The method for predicting the extension life of a resin member of the present invention will be described below using one embodiment as an example, although the method for predicting the extension life of a resin member of the present invention is not limited to the following embodiment.

[0010] As mentioned above, the molecular bonds of resin are broken by heat or light. At this time, radicals are generated within the resin, and these radicals react with oxygen in the air to generate peroxy radicals. Peroxy radicals are highly reactive, extracting oxygen from other molecules and generating peroxides and radicals. The generated radicals then generate more peroxy radicals. Peroxides are also unstable, so they decompose and generate more peroxy radicals and radicals. In other words, when radicals are generated within a resin, a chain reaction of oxidation occurs, causing rapid deterioration of the resin. For this reason, various resin components generally contain antioxidants along with the resin.

[0011] The inventors have found that the elongation life of a resin part containing such a resin and an antioxidant can be predicted by treating the resin part by chemiluminescence at multiple temperatures and creating an Arrhenius plot of the treatment temperature and the corresponding oxidation induction time (OIT). The reason why this method can predict the elongation life is as follows. The chemiluminescence method, also known as the chemical luminescence method, detects the weak light generated when molecules in a reaction system transition from an excited state to a ground state during a chemical reaction. This chemiluminescence method can detect the oxidation reaction of a substance at an early stage with high sensitivity and detect the luminescence emitted from peroxides generated during resin degradation. As described below, this luminescence is detected when the antioxidant is completely consumed. In other words, the oxidation induction time determined by chemiluminescence represents the time required for the antioxidant in the resin part to be consumed at the treatment temperature. Meanwhile, the reduction in the elongation of the resin part occurs when the antioxidant in the resin part is completely consumed and the above-mentioned radical reaction begins. Therefore, there is a close relationship between the oxidation induction time determined by the chemiluminescence method and the elongation life of the resin part. According to Arrhenius' law, the chemical reaction rate (here, the consumption rate of the antioxidant) depends on the temperature, and the following equation holds between the time L until the antioxidant is consumed and the temperature T [K]: lnL=X+E a / RT (X is a constant, E a is the activation energy (constant), and R is the gas constant. Furthermore, by creating an Arrhenius plot of multiple treatment temperatures and the corresponding oxidation induction times using the chemiluminescence method, the slope and intercept of the above equation can be derived. Using this result (graph), it is possible to predict the time L until the antioxidant is consumed at a specific temperature, i.e., the elongation life of the resin part at a specific temperature.

[0012] The method for predicting the extended life of this embodiment can be applied to various resin members containing resin and antioxidant. The type of resin contained in the resin member is not particularly limited. The resin member may contain only one type of resin, or may contain two or more types of resin. For example, when the resin member is an insulating member for an insulated electric wire (such as an outer covering or a member disposed at the end of the insulated electric wire), the resin may be polypropylene, cross-linked polyethylene, ethylene propylene rubber, or the like. The type of antioxidant contained in the resin member is not particularly limited. The resin member may contain only one type of antioxidant, or may contain two or more types. When the resin member is an insulating member for an insulated electric wire, the antioxidant may be a phenol-based antioxidant, an aromatic amine-based antioxidant, a sulfur-based antioxidant, a phosphorus-based antioxidant, or the like. The resin member may further contain components other than the resin member and the antioxidant, as long as the purpose and effect of this embodiment are not impaired. Examples of components other than the resin and the antioxidant include colorants and various additives (for example, crosslinking agents and ultraviolet absorbers).

[0013] The flow of the method for predicting the elongation life of a resin member according to this embodiment is shown in the flowchart of Fig. 1. In the method according to this embodiment, first, the resin member is treated by a chemiluminescence method at three or more different temperatures, and the oxidation induction time at each temperature is identified (hereinafter also referred to as the "chemiluminescence treatment step", S10). Then, an Arrhenius plot is made of the multiple temperatures at which the chemiluminescence treatment was performed and the corresponding oxidation induction times (OITs), and the extension life of the resin part at a specific temperature is predicted from the results (hereinafter also referred to as the "extension life prediction step", S20). The prediction method of this embodiment may further include other steps as long as the purpose and effect are not impaired. The chemiluminescence treatment step S10 and the extended life prediction step S20 will be described in detail below.

[0014] (Chemiluminescence treatment process) In the chemiluminescence treatment step S10, a measurement sample is prepared from a resin component whose extension life is to be predicted, or from a resin component equivalent thereto (S11). In this embodiment, the measurement sample may be prepared from the resin component whose extension life is to be predicted. Alternatively, the measurement sample may be prepared from another resin component that was manufactured under the same conditions as the resin component whose extension life is to be predicted, and that was stored or used under the same conditions. The number of measurement samples to be prepared is adjusted appropriately depending on the number of times the chemiluminescence method is to be performed.

[0015] The measurement sample prepared above is treated by chemiluminescence at three or more different temperatures (T1, T2, T3, ...) (S13). At this time, the number of temperatures at which the chemiluminescence is performed (hereinafter also referred to as "treatment temperatures") may be three, four or more. The greater the number of treatment temperatures, the higher the prediction accuracy in the life prediction step S20. On the other hand, the fewer the number of treatment temperatures, the higher the treatment efficiency in the chemiluminescence treatment step S20. Therefore, it is preferable that the number of treatment temperatures be between three and six. Here, it is preferable that the multiple treatment temperatures are at least 10°C apart from one another, from the viewpoint of improving the prediction accuracy in the life prediction step S20 described below. Furthermore, while any temperature may be used for each treatment, a higher treatment temperature is preferable from the viewpoint of shortening the oxidation induction time. On the other hand, it is preferable that the treatment temperature is equal to or lower than the melting point of the resin in the resin component. If the treatment temperature is equal to or lower than the melting point of the resin, there is no need to consider decomposition of the resin or changes in crystallinity. Therefore, it becomes possible to more accurately predict the extended life in the extended life prediction step S20 described below.

[0016] The device used in the chemiluminescence method is called a chemiluminescence analyzer, and for example, a device manufactured by Tohoku Electronics Industries Co., Ltd. can be used. The chemiluminescence analyzer includes a sample chamber for accommodating and heating the sample, a detector (photomultiplier tube), and a spectral filter disposed therebetween. The procedure for processing by the chemiluminescence method using such a chemiluminescence analyzer will be described below, along with the changes in luminescence intensity observed by the chemiluminescence method shown in Figure 2. When performing chemiluminescence processing, the measurement sample is first placed in the test chamber of the chemiluminescence analyzer and heated under an inert atmosphere (e.g., nitrogen atmosphere). This decomposes the luminescent components (e.g., peroxides) originally present in the measurement sample, and an emission peak associated with the decomposition is observed. The atmosphere in the sample chamber is then converted to an oxygen atmosphere. The sample is then heated at the above-mentioned processing temperature (T1). This generates the aforementioned peroxy radicals in the measurement sample, gradually consuming the antioxidant. However, in this state, the antioxidant reacts with the generated peroxy radicals, resulting in an equilibrium state. In other words, the emission intensity hardly changes from the start of heating under the oxygen atmosphere. After that, when the antioxidant is almost completely consumed, peroxides are generated in the measurement sample. As a result, the emission intensity increases sharply and a peak appears, as shown in Figure 2. In this embodiment, the oxidation induction time (α1) is defined as the time from the start of heating (t1) at a predetermined treatment temperature (T1) in an oxygen atmosphere to the time point (t2) at which the peak begins to rise. The time point (t2) at which the peak begins to rise is determined from the intersection of the line representing the equilibrium state due to the antioxidant and the line (tangent) that rises due to the increase in the amount of luminescence in the graph showing the luminescence intensity. The same process is repeated with a new measurement sample and different treatment temperatures, and the oxidation induction times (α1, α2, α3, . . .) at each treatment temperature (T1, T2, T3, . . .) are determined. The oxygen flow rate in the sample chamber during the chemiluminescence treatment can be set as appropriate, and is selected as appropriate depending on the type of resin member, the type of resin in the resin member, and the like.

[0017] (Extended life prediction process) In the extended life prediction step S20, an Arrhenius plot is created (S21) of the treatment temperatures (T1, T2, T3, . . . ) [K] and oxidation induction times (t1, t2, t3, . . . ) [minutes] used in the chemiluminescence treatment step S10. That is, the reciprocals of the treatment temperatures {(1 / T1), (1 / T2), (1 / T3), . . .} are represented as x, and the corresponding logarithms of the oxidation induction times {(ln(α1), ln(α2), ln(α3), . . .}} are represented as y. The multiple points on the Arrhenius plot are then linearly approximated and, if necessary, extrapolated (extended). From the obtained straight line, the oxidation induction time (αx) at a specific temperature (Tx) for which the elongation life is to be predicted is identified, and the oxidation induction time is estimated as the elongation life of the resin member at that temperature (Tx) (S23). Although the specific temperature (Tx) used to predict the extension life in this embodiment is not particularly limited, it is very useful for predicting the extension life at temperatures between 80°C and 155°C inclusive in heat resistance evaluation assuming the usage environment of the insulating member of the insulated electric wire. This range corresponds to JIS C4003 Type Y-Type F and JASO D611.

[0018] (effect) Measurement of oxidation induction time (OIT) using the chemiluminescence method can be performed in a short time under relatively mild conditions. Furthermore, the crystallinity of the resin member is unlikely to change during OIT measurement, eliminating the need for complex processing. Therefore, the method of this embodiment makes it possible to accurately predict the elongation life of a resin member in a very short time without complex processing. This method for predicting the elongation life of a resin member can be used for performance evaluation during the development of the resin member and quality inspection during the manufacture of the resin member. Furthermore, according to the method for predicting the extension life, it is possible to easily determine the extension life of the insulating member of the insulated wire, and it is also possible to easily determine the time to replace the insulated wire. [Example]

[0019] Below, an example will be shown in which the elongation life of the outer sheath of an insulated wire was actually predicted and verified.

[0020] 1. Example 1 (1) Preparation of measurement samples Three measurement samples were prepared from a resin member (sample 1) containing polypropylene and an antioxidant (a mixture of a phenolic antioxidant and a phosphorus-based antioxidant) with an antioxidant concentration of 0.45 mass %. Similarly, three measurement samples were prepared from a resin member (sample 2) containing polypropylene and an antioxidant (a mixture of a phenolic antioxidant and a phosphorus-based antioxidant) with an antioxidant concentration of 0.75 mass%.

[0021] (2) Chemiluminescence treatment The measurement sample of Sample 1 was treated by chemiluminescence at three temperatures (200°C, 210°C, 220°C) using a chemiluminescence analyzer (Tohoku Electronics Industries Co., Ltd.), and the oxidation induction time at each temperature was determined. The treatment conditions for the chemiluminescence method were as follows: (Processing conditions) - Sample chamber temperature during heating (processing temperature): 200℃, 210℃, 220℃ Heating time in nitrogen atmosphere: 5 minutes Heating time in oxygen atmosphere: 10 to 150 minutes Oxygen flow rate in oxygen atmosphere: 50 ml / min

[0022] Similarly to the above, the measurement sample of Sample 2 was also treated by the chemiluminescence method at three temperatures (200°C, 210°C, 220°C), and the oxidation induction time at each temperature was determined.

[0023] (3) Arrhenius plot and life prediction The treatment temperatures in the chemiluminescence method and the corresponding oxidation induction times were plotted as Arrhenius plots, and a linear approximation graph for each sample is shown in Figure 3. Figure 4 also shows a linear extrapolation graph of the Arrhenius plot for each sample. The elongation life of each sample at 100°C was predicted from the graph in Figure 4 (the two straight lines obtained). The predicted elongation life of Sample 1 was approximately 10,000 hours, and the predicted elongation life of Sample 2 was approximately 40,000 hours.

[0024] (4) Verification of predicted elongation life Thermal degradation tests were performed on the above-mentioned Sample 1 and Sample 2 at 120°C, 135°C, and 150°C, respectively. Specifically, tensile tests were performed on samples at each of the above temperatures for various heating times in accordance with JIS 7161-1:2014 using a tensile tester to determine the strain for each heating time. The obtained strain and heating time were plotted as an Arrhenius plot to determine the time until the strain reached 100% (elongation life). The heating temperature and elongation life were then plotted on a graph, and the linear approximation results are shown in Figure 4. The elongation life of Sample 1 at 100°C was approximately 10,000 hours, and the elongation life of Sample 2 at 100°C was approximately 40,000 hours. There was no significant difference between the elongation life predicted by the thermal degradation test method and that predicted using the chemiluminescence method. In other words, the method for predicting the elongation life of a resin member of the present invention is effective.

[0025] 2. Example 2 Three measurement samples were prepared from a resin part (Sample 3) containing cross-linked polyethylene resin and an antioxidant (a mixture of a phenolic antioxidant and a phosphorus-based antioxidant) with an antioxidant concentration of 0.2 mass%. Similarly, three measurement samples were prepared from a resin part (Sample 4) containing cross-linked polyethylene resin and an antioxidant (a mixture of a phenolic antioxidant and a phosphorus-based antioxidant) with an antioxidant concentration of 0.4 mass%.

[0026] As in Example 1, chemiluminescence treatment was performed at three temperatures (190°C, 200°C, and 210°C), and the oxidation induction time at each temperature was determined. The chemiluminescence treatment temperatures and the corresponding oxidation induction times were plotted as an Arrhenius plot and linearly extrapolated to form a graph shown in Figure 5. The extension life of each sample at 90°C was predicted from the graph in Figure 5 (the two straight lines obtained). As a result, the extension life of each of Samples 3 and 4 was predicted to exceed 30 years. [Industrial Applicability]

[0027] The method for predicting the extension life of a resin member of the present invention makes it possible to predict the extension life of various resin members, such as insulating members for insulated electric wires, and is therefore extremely useful in various industrial fields.

Claims

1. A method for predicting an extended life of a resin member containing a resin and an antioxidant, a step of treating the resin workpiece by a chemiluminescence method at three or more temperatures different from each other and specifying an oxidation induction time at each of the temperatures; a step of predicting an elongation life of the resin member at a specific temperature from an Arrhenius plot result of each of the temperatures and each of the oxidation induction times; A method for predicting the elongation life of a resin member, comprising:

2. 2. The method for predicting the elongation life of a resin member according to claim 1, The resin member is an insulating member for an insulated wire. A method for predicting the elongation life of resin components.

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