Evaluation method

Abstract

The present invention performs: a first step in which a test device 10 applies a load to a polymer material; a second step in which a measurement device 20 measures a plurality of chemiluminescence amounts emitted from the polymer material along a time axis; and a third step in which an evaluation device 30 calculates an oxidation induction time from a chemiluminescence amount curve along the plurality of chemiluminescence amounts and calculates the durability of the polymer material on the basis of the length of the oxidation induction time.

Description

Evaluation method

[0001] The present disclosure relates to an evaluation method.

[0002] Compared with inorganic compounds such as metals, ceramics, and glass, polymer materials are more likely to deteriorate and have inferior durability. For example, a living hinge having an opening and closing structure is composed of a polymer material with high flexibility and large elongation at break, such as polypropylene or polyethylene.

[0003] Therefore, products made of polymer materials, etc. must consider deterioration such as photooxidation and bending. Thus, there is a technique for evaluating the durability of polymer materials (see Non-Patent Documents 1 to 7).

[0004] Oishi, "Degradation analysis, durability evaluation, and life prediction supporting the reliability of polymer materials", Polymer, Vol. 48, November issue, 1999, pp. 838 - 841; Mikawa, 5 others, "Comparison of degradation behavior of low-density polyethylene by a weather resistance tester", Materials and Environment, 64, 2015, pp. 139 - 144; "Method for determining exposure environment regarding the weather resistance of plastics using polyethylene reference test pieces (amended on April 1, 2009)", Japan Weathering Test Center, JWTCS4002:2009; Yokoi, 1 other, "Effect of improving hinge characteristics by in-mold pressing hinge molding", Production Research 393, Vol. 42, No. 6, June 1990, pp. 97 - 100; Kaori Negishi, 5 others, "Microscopic Analysis of Degraded Living Hinges of Polypropylene Aerial Cable Closure", Materials and Environment, Vol. 72, No. 3, 2023, pp. 76 - 84; "Environmental stress cracking of plastics", Osaka Institute of Industrial Technology, Technical Sheet, NO. 98037; Sato, 1 other, "Recent trends in highly sensitive chemiluminescence measurement methods - from detection of minute oxidation of resins to curing reactions -", Journal of the Adhesion Society of Japan, Vol. 55, No. 6, 2019, pp. 236 - 245

[0005] However, there is a problem that it takes time to calculate the evaluation of the durability of polymer materials.

[0006] This disclosure is made in view of the above circumstances, and the purpose of this disclosure is to provide a technology that can improve the total test time for evaluating the durability of polymer materials.

[0007] An evaluation method in one aspect of the present disclosure includes a first step in which a test device applies a load to a polymer material, a second step in which a measuring device measures multiple amounts of chemiluminescence emitted from the polymer material along a time axis, and a third step in which an evaluation device calculates the oxidation induction time from a chemiluminescence curve along the multiple amounts of chemiluminescence and calculates the durability of the polymer material based on the length of the oxidation induction time.

[0008] According to this disclosure, the total testing time required for evaluating the durability of polymer materials can be reduced.

[0009] Figure 1 shows an example of the configuration of the durability evaluation system according to the first embodiment. Figure 2 shows an example of a polymer material. Figure 3 shows an example of the measurement of oxidation induction time. Figure 4 shows an example of the operation of the durability evaluation system according to the first embodiment. Figure 5 shows the evaluation results of the degradation resistance performance according to the first embodiment. Figure 6 shows an example of the bending angle of the polymer material. Figure 7 shows an example of the operation of the durability evaluation system according to the second embodiment. Figure 8 shows the evaluation results of the degradation resistance performance according to the second embodiment. Figure 9 shows an example of the operation of the durability evaluation system according to the third embodiment. Figure 10 shows the evaluation results of the degradation resistance performance according to the third embodiment. Figure 11 shows an example of the configuration of the durability evaluation system according to the fourth embodiment. Figure 12 shows an example of the operation of the durability evaluation system according to the fourth embodiment. Figure 13 shows the evaluation results of the degradation resistance performance according to the fourth embodiment. Figure 14 shows an example of the hardware configuration of the evaluation device.

[0010] Embodiments of this disclosure will be described below with reference to the drawings. In the drawings, the same parts are denoted by the same reference numerals and their descriptions are omitted.

[0011] [Summary of this disclosure] This disclosure describes a method for evaluating the durability of a polymer material by applying a load to degrade it, measuring the amount of chemiluminescence emitted from the polymer material multiple times along the time axis, and calculating the length of oxidation induction time from the chemiluminescence curves along the multiple chemiluminescence amounts.

[0012] For example, a polymer material is subjected to photo-oxidative degradation by light irradiation, the amount of peroxide generated on the surface of the polymer material is measured, and the oxidation induction time is calculated from a curve or an approximation curve formed by connecting multiple measured generation amounts over time, and the evaluation is based on the length of this oxidation induction time.

[0013] In other words, radicals generated in polymer materials by light, heat, etc., react with oxygen in the air to form peroxide radicals. The light emitted when the excited carbonyl and singlet oxygen generated by the bimolecular reaction of the peroxide radicals return to the ground state is detected.

[0014] In this way, by utilizing the amount of chemiluminescence emitted from degraded polymer materials, it is possible to detect the initial stages of degradation of polymer materials. Therefore, the total testing time for evaluating the durability of polymer materials can be shortened. Furthermore, since the amount of chemiluminescence is measured as a numerical value, the degree of oxidation, durability, and degradation of polymer materials can be quantitatively evaluated.

[0015] [First Embodiment] In the first embodiment, a case in which a polymer material is degraded by subjecting it to environmental stress will be described.

[0016] (Example of Durability Evaluation System Configuration) Figure 1 is a diagram showing an example of the configuration of a durability evaluation system according to the first embodiment. The durability evaluation system 1 comprises a test device 10, a measuring device 20, and an evaluation device 30.

[0017] The test apparatus 10 is an accelerated weathering test apparatus designed to simulate the degradation of polymer materials due to degradation factors in the outdoor environment. For example, the test apparatus 10 is capable of performing tests in accordance with ISO 11341, JIS K 5600-7-7, JIS K 7350-2, etc.

[0018] Specifically, the test apparatus 10 applies environmental and stress loads to the polymer material. Environmental loads include, for example, light, heat, water, and chemicals. Stress loads include, for example, bending stress, tensile stress, compressive stress, and torsional stress. One or more types of loads are sufficient to be applied to the polymer material.

[0019] Such a test apparatus 10 includes a simulated sunlight light source, a heat source, a water source, a chemical solution input source, a temperature control function, a humidity control function, a bending stress application mechanism, a tensile stress application mechanism, a compressive stress application mechanism, and a torsional stress application mechanism. These structures are arbitrary.

[0020] For example, let's explain light sources.

[0021] The light source emits light in the ultraviolet, visible, and infrared regions. Examples include ultraviolet fluorescent lamps, xenon lamps, sunshine carbon lamps, and metal halide lamps. Xenon lamps are preferred because their spectrum is similar to sunlight and they can accelerate degradation. If further acceleration of degradation is desired, ultraviolet fluorescent lamps and metal halide lamps are also suitable.

[0022] A filter may be placed near the light source to make the spectral radiation distribution of the light source closer to that of sunlight. Sunlight may be used instead of a light source, but since this takes a long time for the polymer material to degrade, it is preferable to combine it with a chemical solution that can accelerate degradation.

[0023] Next, the measuring device 20 will be described.

[0024] The measuring device 20 is a device that measures the amount of chemiluminescence emitted from the surface of a polymer material that has been degraded in the test device 10.

[0025] In particular, the measuring device 20, in order to further accelerate degradation and improve the detection accuracy of chemiluminescence emission, places the polymer material in an oxygen atmosphere and within the temperature at which the surface reaction occurs, and applies light irradiation. It then alternately performs light irradiation and emission measurement, taking multiple measurements of the amount of chemiluminescence emission along the time axis.

[0026] Next, the evaluation device 30 will be described.

[0027] The evaluation device 30 is a device that obtains multiple emission curves along the emission amounts obtained by alternately performing light irradiation and emission amount measurement, calculates the oxidation induction time of the polymer material from the emission curve, and evaluates the durability (degradation life, etc.) of the polymer material based on the length of the oxidation induction time.

[0028] For example, when multiple polymer materials are photo-oxidized under the same conditions, the amount of light emitted from the surface is measured under the same conditions using chemiluminescence, and the oxidation induction time is calculated. Polymer materials with longer oxidation induction times are evaluated as having higher degradation resistance.

[0029] Such an evaluation device 30 includes, for example, a processing unit 31, an output unit 32, and a storage unit 33.

[0030] The processing unit 31 has the function of obtaining a light emission curve by connecting multiple light emission values ​​obtained by alternately performing light irradiation and light emission measurement in a time series, or obtaining a light emission curve that approximates the said multiple light emission values, calculating the oxidation induction time of the polymer material from the light emission curve, and evaluating the durability of the polymer material based on the length of the oxidation induction time.

[0031] The output unit 32 has a function to output the evaluation results of the durability of the polymer material.

[0032] The memory unit 33 has a function to store the evaluation results of the durability of polymer materials.

[0033] Next, we will explain specific examples of each device.

[0034] Existing accelerated weathering test equipment can be used as the test apparatus 10.

[0035] For example, a chemiluminescence analyzer can be used as the measuring device 20 and the evaluation device 30. A chemiluminescence analyzer is a device that measures the amount of chemiluminescence emitted using a known method such as JIS K7351. A computer may also be used in combination. In this case, the chemiluminescence analyzer corresponds to the measuring device 20, and the computer corresponds to the evaluation device 30.

[0036] (Polymer materials) Next, we will explain polymer materials.

[0037] The polymer material is, for example, an olefin-based polymer material including a living hinge structure. The living hinge structure refers to a structure in which two members are joined together by a thin part so that the two members can be opened and closed.

[0038] For example, as shown in FIG. 2, a strip-shaped first polymer material 100a measuring 2 cm × 5 cm including a linear living hinge structure indicated by a dashed line, a second polymer material 100b measuring 1 cm × 1 cm cut out from the first polymer material 100a so as to include the living hinge structure, and a third polymer material 100c cut out in a dumbbell shape from the first polymer material 100a so as to include the living hinge structure.

[0039] For example, the polymer material is a resin cap of a mayonnaise container or a hand cream container, and includes a lid and a lid seat formed in substantially the same shape with a thin and soft resin, and a thin resin member connecting the lid and the lid seat.

[0040] When there is a hinge portion in the test piece of the polymer material, it is preferable that the short side of the test piece and the hinge portion are parallel. The thickness of the polymer material is preferably uniform over the entire plane excluding the hinge portion. In the first embodiment, since only an environmental load is applied to the polymer material, it may not include a living hinge structure.

[0041] (Operation example of the durability evaluation system) Next, an operation example of the durability evaluation system 1 will be described.

[0042] (Step 1) In the test apparatus 10, an accelerated weathering test of the polymer material is performed under preset conditions.

[0043] For example, in accordance with JIS K5600-7-7 and JIS K7350-2, the conditions in the tank are set as "black panel temperature: 63 °C, temperature: 38 °C, humidity: 50% RH, water spray time: 18 minutes out of 2 hours, light irradiation intensity: ultraviolet radiation intensity of wavelength 300 nm to 400 nm is 60 W / m 2 ". Then, the polymer material to be evaluated is placed in the tank and accelerated degradation is performed for 1000 hours.

[0044] (Step 2) In the measuring device 20, for the polymer material subjected to the above various types of deterioration, while alternately repeating light irradiation and luminescence amount measurement, the luminescence amount (luminescence intensity) of chemiluminescence emitted from the surface of the deteriorated polymer material is measured.

[0045] When measuring the luminescence amount of chemiluminescence, it is preferable to place the polymer material in an oxygen atmosphere.

[0046] When measuring the luminescence amount of chemiluminescence, it is preferable to place the polymer material within a temperature range where surface reactions occur. For example, the measurement is performed while the polymer material is placed within a constant temperature range of 80°C to 200°C or during a temperature increase process.

[0047] As the temperature adjustment means, any device capable of heating the inside of the container storing the polymer material may be used. For example, it is a heater capable of heating to a temperature above the temperature at which surface reactions occur on the surface of the polymer material. The temperature conditions may be appropriately set, such as a constant temperature or a temperature increase process.

[0048] For example, the measuring device 20 arranges the polymer material under an oxygen gas atmosphere and at a constant temperature of 160°C, irradiates light for 1 minute from a light source with a wavelength of 300 nm to 400 nm and an ultraviolet radiation intensity of 60 W / m 2 then measures the luminescence amount for 20 seconds, and then repeats the process of setting an interval of 2 minutes.

[0049] Note that the light irradiation and luminescence amount measurement may be alternately repeated manually by the user.

[0050] (Step 3) By continuing the measurement with the measuring device 20, a luminescence curve regarding the luminescence amount of chemiluminescence is obtained. This luminescence curve is a spectrum obtained by measuring the luminescence amount when excited carbonyls and singlet oxygen generated due to oxygen deterioration on the surface of the polymer material return to the ground state.

[0051] As shown in Figure 3, the amount of chemiluminescence emitted shows a maximum peak at a specific time due to oxides on the surface of the polymer material, and then decreases to a constant value. The point where the tangent line at the point where the slope of the emission intensity curve (emission intensity curve) obtained from this relationship between time and emission amount is maximum intersects with the baseline of the time axis is the oxidation induction time. If this oxidation induction time is greater than a certain amount, it can be evaluated as having high weather resistance.

[0052] Therefore, in the evaluation device 30, the oxidation induction time is calculated using the amount of chemiluminescence light emitted until a certain value is reached. If the oxidation induction time is greater than or equal to a certain minute, the durability (weather resistance) of the polymer material being evaluated is determined to be high. If the oxidation induction time is shorter than a certain minute, the durability (weather resistance) of the polymer material being evaluated is determined to be low.

[0053] (Example of operation of the durability evaluation system) Figure 4 is a diagram showing an example of operation of the durability evaluation system according to the first embodiment.

[0054] The test apparatus 10 irradiates each polymer material test specimen with ultraviolet light emitted from a xenon lamp for 1000 hours (steps S101, S102).

[0055] The weathering test duration may be shorter than 1000 hours. Depending on the test specimen, due to the effects of weathering agents, etc., sufficient degradation may not begin after 1000 hours in terms of detecting chemiluminescence emission. Therefore, the duration should be set to a time sufficient for degradation to begin, depending on the material, size, shape, etc., of the test specimen.

[0056] Next, each test specimen is placed in the photo-oxidation degradation sample chamber. The measuring device 20 irradiates each test specimen with light for 1 minute, and then, under an oxygen gas atmosphere and a constant temperature of 160°C (JIS K7351), measures the amount of chemiluminescence emitted from the surface of each test specimen for 20 seconds, followed by a 2-minute interval (steps S103, S104).

[0057] Next, the evaluation device 30 determines whether a maximum peak appeared in the chemiluminescence emission amount and then decreased to a constant value (step S105).

[0058] If the above condition is not observed in the chemiluminescence emission, the process returns to step S103, and the measuring device 20 alternately repeats light irradiation and emission measurement until the condition appears. Note that the measurement temperature is not limited to 160°C, but is preferably below the melting point. If the test specimen contains additives such as antioxidants or light stabilizers, reactions that would not occur in reality may occur at high temperatures, so it is preferable to set the temperature as low as possible depending on the application.

[0059] If the above condition appears in the chemiluminescence emission amount, the evaluation device 30 calculates the oxidation induction time from the intersection of the tangent line at the point where the slope of the emission amount curve, which shows the relationship between time and emission amount obtained by measurement, is maximum, and the baseline of the time axis (step S106).

[0060] Next, the evaluation device 30 determines whether the oxidation induction time is 20 minutes or longer (step S107).

[0061] Finally, the evaluation device 30 determines that the degradation resistance is sufficient for test specimens whose oxidation induction time is 20 minutes or more (step S108), and that the degradation resistance is insufficient for test specimens whose oxidation induction time is less than 20 minutes (step S109).

[0062] Figure 5 shows the evaluation results of the degradation resistance performance of samples I to IV of the four test specimens. Sample I was judged to have insufficient degradation resistance because its oxidation induction time was less than 20 minutes. Samples II to IV were judged to have sufficient degradation resistance because their oxidation induction time was 20 minutes or longer.

[0063] (Effects of the First Embodiment) According to the first embodiment, the test apparatus 10 degrades the polymer material by applying an environmental load, the measuring device 20 measures the amount of chemiluminescence emitted from the degraded polymer material multiple times along the time axis, and the evaluation device 30 calculates the oxidation induction time from the emission curve along the multiple emission amounts, and calculates the durability of the polymer material based on the length of the oxidation induction time. This makes it possible to capture the initial stage of degradation of the polymer material and shorten the total test time for evaluating the durability of the polymer material.

[0064] Furthermore, according to the first embodiment, since the amount of chemiluminescence light emitted is measured, the degree of oxidation, durability, and degradation of the polymer material can be quantitatively evaluated.

[0065] [Second Embodiment] The chemiluminescence method for evaluating degradation resistance can be used not only for photo-oxidative degradation but also for degradation due to bending, etc. Therefore, in the second embodiment, a case in which a polymer material is degraded by applying stress load will be described.

[0066] The configuration of the durability evaluation system is the same as in the first embodiment. The test apparatus 10 is a device that applies stress load to a polymer material. For example, the test apparatus 10 is a device capable of performing tests in accordance with JIS P8115, JIS-K5600, JIS C 3005, etc.

[0067] For example, the test apparatus 10 bends the polymer material at a predetermined bending angle and number of bends. For example, for each polymer material, bending is performed at 0 degrees, 30 degrees, 50 degrees, 90 degrees, 120 degrees, 10 times, and 30 times. The bending angle is the angle formed when the two members 101 and 102 constituting the polymer material 100 are bent in a living hinge structure, as shown in Figure 6.

[0068] The measuring device 20 measures the amount of chemiluminescence emitted from a polymer material after it has been subjected to stress loading, by alternately performing light irradiation and emission measurement.

[0069] The evaluation device 30 calculates the oxidation induction time from the emission curves along the multiple measured emission amounts, and evaluates the durability of the polymer material based on the length of that oxidation induction time.

[0070] For example, the evaluation device 30 measures the amount of chemiluminescence emitted from multiple polymer materials that have been degraded by bending under the same conditions using the chemiluminescence method, calculates the oxidation induction time, and evaluates polymer materials with longer oxidation induction times as having higher degradation resistance.

[0071] The stress load may be applied manually by the user, rather than by the test device 10.

[0072] Figure 7 shows an example of operation of the durability evaluation system according to the second embodiment.

[0073] The test apparatus 10 bends each polymer material test specimen to 50 degrees 1000 times (step S201). The bending angle and number of bends are preferably set to conform to the usage environment of the polymer material.

[0074] Steps S202 to S208 shown in Figure 7 are the same as steps S103 to S109 shown in Figure 4.

[0075] Figure 8 shows the evaluation results of the degradation resistance performance of samples I to IV of the four test specimens. Sample II was judged to have insufficient degradation resistance because its oxidation induction time was shorter than 20 minutes. Samples I, III, and IV were judged to have sufficient degradation resistance because their oxidation induction time was 20 minutes or longer.

[0076] According to the second embodiment, the test apparatus 10 applies stress load to the polymer material to degrade it, the measuring device 20 measures the amount of chemiluminescence emitted from the degraded polymer material multiple times along the time axis, and the evaluation device 30 calculates the oxidation induction time from the emission curve along the multiple emission amounts, and calculates the durability of the polymer material based on the length of the oxidation induction time. This makes it possible to capture the initial stage of degradation of the polymer material and shorten the total test time for evaluating the durability of the polymer material.

[0077] Furthermore, according to the second embodiment, since the amount of chemiluminescence light emitted is measured, the degree of oxidation, durability, and degradation of the polymer material can be quantitatively evaluated.

[0078] [Third Embodiment] In the third embodiment, a case in which a polymer material is subjected to combined degradation due to environmental load and stress load will be described.

[0079] The configuration of the durability evaluation system is the same as in the first and second embodiments.

[0080] For example, the test apparatus 10 performs a process of subjecting the polymer material to photo-oxidative degradation and a process of repeatedly bending it. For example, photo-oxidative degradation is applied for 100 hours, and each polymer material is bent five times at 0 degrees, 30 degrees, 50 degrees, 90 degrees, and 120 degrees.

[0081] The two processes described above are repeated until, for example, the time of photo-oxidative degradation exceeds 1000 hours. At this point, the measuring device 20 alternately performs light irradiation and light emission measurement, measuring the amount of chemiluminescence emitted. The evaluation device 30 calculates the oxidation induction time from the light emission curves along the multiple measured light emission amounts, and evaluates the durability of the polymer material based on the length of this oxidation induction time.

[0082] For example, the evaluation device 30 measures the amount of chemiluminescence emitted from multiple polymer materials that have been degraded by photo-oxidation and bending under the same conditions using the chemiluminescence method, calculates the oxidation induction time, and evaluates polymer materials with longer oxidation induction times as having higher degradation resistance.

[0083] Figure 9 shows an example of operation of the durability evaluation system according to the third embodiment.

[0084] The test apparatus 10 irradiates each polymer material test specimen with ultraviolet light emitted from a xenon lamp for 100 hours (step S301).

[0085] Next, the test apparatus 10 bends each test specimen five times at a 50-degree angle (step S302).

[0086] Next, it is determined whether the test time has exceeded 1000 hours (step S303). If the test time has not exceeded 1000 hours, the process returns to step S301.

[0087] When the test time exceeds 1000 hours, proceed from step S304 onwards. Steps S304 to S310 shown in Figure 9 are the same as steps S103 to S109 shown in Figure 4.

[0088] Figure 10 shows the evaluation results of the degradation resistance performance of samples I to IV of the four test specimens. Sample I was judged to have insufficient degradation resistance because its oxidation induction time was less than 20 minutes. Samples II to IV were judged to have sufficient degradation resistance because their oxidation induction time was 20 minutes or longer.

[0089] According to the third embodiment, the test apparatus 10 degrades the polymer material by applying environmental and stress loads, the measuring device 20 measures the amount of chemiluminescence emitted from the degraded polymer material multiple times along the time axis, and the evaluation device 30 calculates the oxidation induction time from the emission curve along the multiple emission amounts, and calculates the durability of the polymer material based on the length of the oxidation induction time. This makes it possible to capture the initial stage of degradation of the polymer material and shorten the total test time for evaluating the durability of the polymer material.

[0090] Furthermore, according to the third embodiment, since the amount of chemiluminescence light emitted is measured, the degree of oxidation, durability, and degradation of the polymer material can be quantitatively evaluated.

[0091] [Fourth Embodiment] The first to third embodiments described cases where different types of loads were applied to the polymer material. The fourth embodiment describes a case where the evaluation index for degradation resistance is weighted. Specifically, the magnitude of the mechanical property value (degree of physical change due to stress) measured on the polymer material is also added to the evaluation index.

[0092] Figure 11 shows an example of the configuration of a durability evaluation system according to the fourth embodiment. The durability evaluation system 1 includes a second test apparatus 40 in addition to the configuration of the first to third embodiments.

[0093] The second test apparatus 40 is a device that applies mechanical stress to a polymer material and measures the resulting mechanical property values ​​of the polymer material. For example, the second test apparatus 40 is a device that can perform tests in accordance with ISO 527, JIS K7161, etc.

[0094] Specifically, the second testing apparatus 40 performs uniaxial monotonic tensile tests, bending tests, compression tests, Charpy impact tests, Vickers hardness tests, and viscoelasticity tests on polymer materials subjected to environmental loads and stress loads.

[0095] The evaluation device 30 also uses the magnitude of the mechanical property values ​​of the polymer material measured by the second test device 40 to evaluate the degradation resistance performance of the polymer material. For example, the evaluation device 30 evaluates that the degradation resistance performance is high if the elongation at break measured in a uniaxial monotonic tensile test is higher than a certain value compared to before composite degradation.

[0096] In the fourth embodiment, the third polymer material 100c shown in Figure 2(c) is used. The third polymer material 100c is a test specimen cut into a dumbbell shape (JIS K7161-2 5A) from an injection-molded product made of an olefin-based polymer material, including a living hinge structure. The specimen is cut in a direction in which the linear living hinge structure is perpendicular to the tensile direction of the test specimen (y-direction in Figure 2).

[0097] Figure 12 shows an example of operation of the durability evaluation system according to the fourth embodiment.

[0098] Two test specimens are prepared. These two specimens are made of the same material and are of similar size and shape. One specimen will be used for evaluation. The other specimen is used to pre-measure the elongation at break before degradation.

[0099] The test apparatus 10 irradiates a test specimen of the third polymer material 100c with ultraviolet light emitted from a xenon lamp for 100 hours (step S401).

[0100] Next, the test apparatus 10 bends the test specimen five times at a 50-degree angle (step S402).

[0101] Next, it is determined whether the test time has exceeded 1000 hours (step S403). If the test time has not exceeded 1000 hours, the process returns to step S401.

[0102] If the test time exceeds 1000 hours, the test specimen is placed in the photo-oxidation degradation sample chamber, and the measuring device 20 irradiates the test specimen with light for 1 minute, then measures the amount of chemiluminescence emitted from the surface of the test specimen for 20 seconds in an oxygen gas atmosphere and at a constant temperature of 160°C (JIS K7351), and then takes a 2-minute interval (steps S404, S405).

[0103] Next, the evaluation device 30 determines whether a maximum peak appeared in the chemiluminescence emission amount and then decreased to a constant value (step S406).

[0104] If the above condition is not observed in the chemiluminescence emission level, the process returns to step S404, and the measuring device 20 alternately repeats light irradiation and emission level measurement until the condition appears.

[0105] If the above condition appears in the chemiluminescence emission amount, the evaluation device 30 calculates the oxidation induction time from the intersection of the tangent line at the point where the slope of the emission amount curve, which shows the relationship between time and emission amount obtained by measurement, is maximum, and the baseline of the time axis (step S407).

[0106] Next, the evaluation device 30 determines whether the oxidation induction time is 20 minutes or longer (step S408).

[0107] If the oxidation induction time is 20 minutes or longer, the second test apparatus 40 performs a tensile test on the test specimen at a tensile speed of 20 mm / min (step S409).

[0108] If the oxidation induction time is shorter than 20 minutes, the evaluation device 30 determines that the degradation resistance is insufficient (step S410).

[0109] After step S409, the evaluation device 30 calculates the remaining elongation at fracture of the deteriorated specimen relative to the specimen before deterioration (= elongation at fracture after deterioration × 100 / elongation at fracture before deterioration), and determines whether the remaining elongation at fracture exceeds 75% (step S411).

[0110] Finally, the evaluation device 30 determines that the degradation resistance of the test specimen is sufficient if the remaining elongation at break exceeds 75% (step S412), and determines that the degradation resistance of the test specimen is insufficient if the remaining elongation at break is 75% or less (step S413).

[0111] Figure 13 shows the evaluation results of the degradation resistance performance of samples I to IV of the four test specimens. Sample I was not measured because the oxidation induction time was shorter than 20 minutes. Sample II had an oxidation induction time of 20 minutes or more, but the residual elongation at break was 75% or less, so its degradation resistance performance was judged to be generally sufficient. Samples III and IV had oxidation induction times of 20 minutes or more, and the residual elongation at break exceeded 75%, so their degradation resistance performance was judged to be sufficient.

[0112] According to the fourth embodiment, the test apparatus 10 applies environmental load and stress load to the polymer material, the measuring device 20 measures the amount of chemiluminescence emitted from the degraded polymer material multiple times along the time axis, the second test apparatus 40 applies mechanical stress to the polymer material, and the evaluation device 30 calculates the oxidation induction time from the emission curve along the multiple emission amounts, and calculates the durability of the polymer material based on the length of the oxidation induction time and the mechanical property values. This makes it possible to capture the initial stage of degradation of the polymer material and shorten the total test time for evaluating the durability of the polymer material.

[0113] Furthermore, according to the fourth embodiment, since the amount of chemiluminescence light emitted is measured, the degree of oxidation, durability, and degradation of the polymer material can be quantitatively evaluated.

[0114] [Modifications of Evaluation Indicators for Degradation Resistance] (Modification 1) As explained above, oxidation induction time and mechanical property values ​​can be considered as evaluation indicators for degradation resistance. In the fourth embodiment, the case in which these two types of evaluation indicators are used in that order was described, but they may also be used in combination at the same time.

[0115] For example, the evaluation device 30 measures multiple luminescence values ​​for multiple polymer materials that have been degraded by photo-oxidation or bending under the same conditions, by repeatedly measuring the luminescence value and irradiating them with light using the chemiluminescence method. The device calculates the oxidation induction time from the luminescence curves along these multiple luminescence values, and also measures the mechanical properties. If the oxidation induction time is x and the mechanical property value (e.g., tensile strength) is y, then materials with a small x and a large y may be evaluated as having higher degradation resistance.

[0116] For example, the evaluation device 30 may use an evaluation index value calculated by the formula ax + by (where a is a coefficient that adjusts the contribution rate of x, and b is a coefficient that adjusts the contribution rate of y) to evaluate that a higher ax + by value indicates higher degradation resistance. Note that the formula for calculating the evaluation index value from oxidation induction time and mechanical properties is not limited to by - ax, and may be another formula that can calculate a more appropriate index according to the actual degree of degradation.

[0117] For example, the evaluation device 30 may evaluate multiple polymer materials that have been degraded by photo-oxidation or bending under the same conditions, and determine that the degradation resistance is higher when x is the oxidation induction time, y is the mechanical property after degradation, and yi is the mechanical property value before degradation, and the value of y / yi (remaining strength) is larger for materials where x is small.

[0118] For example, the evaluation device 30 may use an evaluation index value calculated by the formula ax + b(y / yi), and evaluate that a higher value of ax + b(y / yi) indicates higher degradation resistance. Note that the formula for calculating the evaluation index value from oxidation induction time and mechanical properties is not limited to ax + b(y / yi), and another formula that can calculate a more appropriate index according to the actual degree of degradation may be used.

[0119] (Modification 2) Environmental load and stress load may be used as evaluation indicators for degradation resistance.

[0120] For example, the evaluation device 30 may evaluate multiple polymer materials that have been degraded to a similar oxidation induction time, and determine that polymer materials with higher light irradiation doses, more bending cycles, and higher mechanical properties after degradation have higher degradation resistance.

[0121] For example, the evaluation device 30 may evaluate multiple polymer materials that have been degraded to a similar oxidation induction time, and determine that polymer materials with a higher amount of light irradiation and a greater number of bending cycles, and with less decrease in mechanical properties before and after degradation, have higher degradation resistance.

[0122] In other words, the evaluation device 30 may calculate and compare an index of the degree of degradation based on the amount of light irradiation, the number of bending cycles, and the mechanical properties before or after degradation.

[0123] For example, the evaluation device 30 may evaluate multiple polymer materials that have been degraded to a similar degree of mechanical properties, and determine that polymer materials with a higher amount of light irradiation, a greater number of bending cycles, and a longer oxidation induction time have higher degradation resistance.

[0124] In other words, the evaluation device 30 may calculate and compare an index of the degree of degradation from the amount of light irradiation, the number of bending cycles, and the oxidation induction time.

[0125] [Other] This disclosure is not limited to the embodiments described above. This disclosure can be modified in numerous ways within the scope of its essence. For example, two or more embodiments from the first to fourth embodiments may be arbitrarily combined. Furthermore, it is preferable to set appropriate values ​​for the numerical values ​​used in each embodiment according to the installation environment, expected lifespan, and usage method of the polymer material.

[0126] The evaluation device 30 of this embodiment described above can be realized using a general-purpose computer system, for example, as shown in Figure 14, which includes a CPU 901, a memory 902, a storage 903, a communication device 904, an input device 905, and an output device 906. The memory 902 and the storage 903 are storage devices. In this computer system, the CPU 901 executes a predetermined program loaded onto the memory 902, thereby realizing each function of the evaluation device 30.

[0127] The evaluation device 30 may be implemented on a single computer. The evaluation device 30 may be implemented on multiple computers. The evaluation device 30 may also be a virtual machine implemented on a computer.

[0128] The program for the evaluation device 30 can be stored on a computer-readable recording medium such as an HDD, SSD, USB memory, CD, or DVD. A computer-readable recording medium is, for example, a non-transitory recording medium. The program for the evaluation device 30 can also be distributed via a communication network.

[0129] 1 Durability evaluation system 10 Test device 20 Measurement device 30 Evaluation device 31 Processing unit 32 Output unit 33 Storage unit 40 Second test device 100 Polymer material 100a First polymer material 100b Second polymer material 100c Third polymer material 901 CPU 902 Memory 903 Storage 904 Communication device 905 Input device 906 Output device

Claims

1. An evaluation method comprising: a first step in which a test device applies a load to a polymer material; a second step in which a measuring device measures multiple amounts of chemiluminescence emitted from the polymer material along a time axis; and a third step in which an evaluation device calculates the oxidation induction time from a chemiluminescence curve along the multiple amounts of chemiluminescence and calculates the durability of the polymer material based on the length of the oxidation induction time.

2. The evaluation method according to claim 1, wherein in the second step, the amount of chemiluminescence emitted from the polymer material, which is placed in an oxygen atmosphere and at a surface reaction temperature and irradiated with light, is measured multiple times along the time axis, and in the third step, the oxidation induction time is calculated from the chemiluminescence curve obtained by alternately performing the light irradiation and the measurement of the amount of chemiluminescence, and the durability of the polymer material is calculated based on the length of the oxidation induction time.

3. The evaluation method according to claim 1, wherein in the third step, the durability of the polymer material is calculated based on the length of the oxidation induction time and the degree of physical change due to stress on the polymer material.

4. The evaluation method according to claim 1, wherein the load is one or more of light, heat, water, and stress.

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