Elastic material performance evaluation method

Abstract

To provide a method of performance evaluation capable of predicting the performance of an elastic material.SOLUTION: There is provided a method for evaluating the performance of elastic materials including rubbers or elastomers. The method includes: a step S2 of forming at least one air gap inside a specimen made of an elastic material by applying a strain to the specimen; a step S3 of acquiring a projected image of the specimen by irradiating the specimen with X-rays at multiple times after forming the air gap; and a step S4 of identifying the volume change of the air gap between multiple times from the projected image as one of the performance indicators.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a method for evaluating the performance of an elastic material. [Background technology]

[0002] 2. Description of the Related Art Conventionally, as a method for evaluating the performance (for example, performance related to abrasion) of an elastic material, for example, a method in which the elastic material is abraded by an indoor abrasion tester such as a Lambourn abrasion tester is known (for example, see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-308447 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, there has been a problem in that the results of performance evaluation using the above method do not match the results of performance of an actual product using the elastic material.

[0005] The present invention has been devised in view of the above circumstances, and has as its main object to provide a method capable of predicting the performance of an elastic material. [Means for solving the problem]

[0006] The present invention is a method for evaluating the performance of an elastic material including rubber or an elastomer, comprising the steps of: applying strain to a test piece made of the elastic material to form at least one void inside the test piece; irradiating the test piece with X-rays at multiple times after the formation of the void to obtain projection images of the test piece; and identifying a volume change of the void between the multiple times from the projection images as one of the indexes of the performance.

[0007] In the performance evaluation method of the present invention, the multiple times may include a first time at which the strain applied to the test piece reaches a predetermined first threshold value, and a second time after a predetermined time has elapsed from the first time.

[0008] In the performance evaluation method according to the present invention, the time period may be 100 to 1200 seconds.

[0009] In the performance evaluation method according to the present invention, the first threshold value may be equal to or greater than 0.2.

[0010] In the performance evaluation method according to the present invention, the step of specifying the volume change includes: determining a volume V0 of the void at the first time and a volume V of the void at the second time; t V t / V0 may be specified as the volume change.

[0011] The performance evaluation method according to the present invention may include a step of evaluating the performance based on the volume change.

[0012] In the performance evaluation method according to the present invention, the evaluating step may evaluate the performance as good when the volume change is equal to or less than a predetermined second threshold value.

[0013] In the performance evaluation method according to the present invention, the second threshold value may be in the range of 1.0 to 3.0.

[0014] In the performance evaluation method according to the present invention, the strain may be an extensional strain.

[0015] In the performance evaluation method according to the present invention, the decay time of the phosphor for converting the X-rays into visible light may be 100 ms or less.

[0016] In the performance evaluation method according to the present invention, the elastic material may be a rubber obtained by using one or more kinds of conjugated diene compounds.

[0017] In the performance evaluation method according to the present invention, the rubber may be rubber for tires.

[0018] In the performance evaluation method according to the present invention, the luminance (photons / s / mrad) of the X-rays is 2 / mm 2 / 0.1%bw) is 10 10 It may be more than that. Effect of the Invention

[0019] The method for evaluating the performance of an elastic material of the present invention employs the above steps, making it possible to predict the performance of the elastic material. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a perspective view of an apparatus for evaluating the performance of elastic materials. [Diagram 2] FIG. 1 is a block diagram of a computer. [Diagram 3] 1 is a flowchart showing a processing procedure of a performance evaluation method for an elastic material. [Figure 4] (a) is a tomographic image of the test piece acquired at a first time, and (b) is a tomographic image of the test piece acquired at a second time. [Diagram 5] 13 is a flowchart showing a processing procedure of a volume change specifying step. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. It should be understood that the drawings include exaggerated expressions and expressions different from the dimensional ratio of the actual structure in order to help understand the contents of the invention. Furthermore, the same or common elements are given the same reference numerals throughout the embodiments, and duplicated explanations are omitted. Furthermore, the specific configurations shown in the embodiments and drawings are for understanding the contents of the present invention, and the present invention is not limited to the specific configurations shown in the drawings.

[0022] In the elastic material performance evaluation method of this embodiment (hereinafter sometimes simply referred to as the "performance evaluation method"), the performance of an elastic material containing rubber or elastomer is evaluated.

[0023] [Elastic material] The elastic material can be appropriately adopted. The elastic material of the present embodiment can be rubber obtained by using one or more conjugated diene compounds. The rubber (elastic material) can be, for example, rubber for tires. An example of the performance evaluated by the method of the present embodiment can be performance related to wear (wear resistance).

[0024] [Elastic material performance evaluation device] The performance evaluation method of this embodiment uses an elastic material performance evaluation device (hereinafter, sometimes simply referred to as "performance evaluation device") 1. Fig. 1 is a perspective view of the elastic material performance evaluation device 1 of this embodiment.

[0025] The performance evaluation device 1 is for evaluating the performance of an elastic material. The performance evaluation device 1 of this embodiment includes a distortion applying unit 2, an imaging unit 3, a volume change specifying unit 4, and an evaluation unit 5.

[0026] [Distortion section] The strain applying unit 2 of this embodiment is for applying strain to the test piece 10 made of an elastic material. The strain applying unit 2 of this embodiment has a pair of jigs 21, 22 to which the test piece 10 is fixed, and a drive unit 23 that applies strain to the test piece 10 by moving the jigs 21 and 22 relatively to each other.

[0027] While fixing one jig 21, the driving unit 23 moves the other jig 22 in a direction in which the other jig 21 and 22 move away from each other. The driving unit 23 in this embodiment moves the other jig 22 in the axial direction of the cylindrical test piece 10. As a result, the test piece 10 is stretched in its axial direction, and strain is applied to it.

[0028] The strain or load applied to the test piece 10 is detected by a load cell (not shown) or the like. The position and type of the load cell are arbitrary. A predetermined strain or load is applied to the test piece 10 by such a strain applying unit 2. The driving unit 23 of this embodiment is configured to be capable of rotating the test piece 10 and the jigs 21, 22 around the axis of the test piece 10.

[0029] [Imaging section] The imaging unit 3 of this embodiment is for irradiating the strained test piece 10 with X-rays to obtain a projection image of the test piece 10. The imaging unit 3 of this embodiment is configured to include an X-ray tube 31 that irradiates X-rays and a detector 32 that detects the X-rays and converts them into an electrical signal. The detector 32 has a phosphor 32a that converts the X-rays into visible light. The imaging unit 3 can obtain projection images of the test piece 10 over the entire circumference by capturing multiple projection images while the test piece 10 is rotated around its axis.

[0030] [Volume change identification and evaluation unit] The volume change identifying unit 4 and the evaluating unit 5 of this embodiment are configured by a computer 8. Fig. 2 is a block diagram of the computer 8 of this embodiment.

[0031] The computer 8 of this embodiment is configured to include an input unit 11 as an input device, an output unit 12 as an output device, and an arithmetic processing unit 13.

[0032] The input unit 11 may be, for example, a keyboard or a mouse. The output unit 12 may be, for example, a display device or a printer. The arithmetic processing device 13 includes a calculation unit (CPU) 13A that performs various calculations, a storage unit 13B that stores data, programs, etc., and a working memory 13C.

[0033] The storage unit 13B is a non-volatile information storage device formed of, for example, a magnetic disk, an optical disk, an SSD, etc. The storage unit 13B includes a data section 16 and a program section 17.

[0034] The data section 16 of this embodiment includes a projection image input section 16A and a volume change input section 16B. The data input to these sections will be explained in the processing procedure of the performance evaluation method described later.

[0035] The program section 17 of this embodiment is configured as a computer program. The program section 17 of this embodiment includes a volume change specifying program 17A and an evaluation program 17B. The volume change specifying program 17A and the evaluation program 17B are executed by the calculation section 13A, whereby the computer 8 can function as the volume change specifying section 4 and the evaluation section 5. These functions will be explained in the processing procedure of the performance evaluation method described later.

[0036] [Method of evaluating the performance of elastic materials] Next, the procedure of the performance evaluation method of this embodiment will be described with reference to Fig. 3, which is a flow chart showing the procedure of the performance evaluation method of this embodiment.

[0037] [Fix the test specimen] In the performance evaluation method of this embodiment, first, as shown in FIG. 1, a test piece 10 is fixed to jigs 21 and 22 (step S1). The above-mentioned elastic material having a uniform density distribution is used for the test piece 10 of this embodiment. The test piece 10 is formed in a cylindrical shape, for example, as in a patent document (JP Patent Publication No. 2017-83182). Details of the test piece 10 and the procedure for fixing the test piece 10 to the jigs 21 and 22 are as described in the patent document (JP Patent Publication No. 2017-83182).

[0038] [Forming a gap] Next, in the performance evaluation method of this embodiment, strain is applied to the test piece 10, and at least one void is formed inside the test piece 10 (step S2). In step S2 of this embodiment, the driving unit 23 of the strain applying unit 2 relatively moves the jigs 21 and 22 of the strain applying unit 2 in directions in which the jigs move away from each other in the axial direction of the cylindrical test piece 10. Thereby, in step S2, the test piece 10 can be elongated, and an elongation strain can be applied to the test piece 10.

[0039] In step S2 of the present embodiment, strain is applied to the test piece 10, which causes local stress concentration inside the test piece 10 and partially destroys the internal structure (bonding of molecular chains) of the elastic material. As a result, at least one void 15 (shown in FIGS. 4(a) and 4(b)) is formed inside the test piece 10. Here, a "void" is defined as a portion where the density of the elastic material when the test piece 10 is strained is 0.0 to 0.1, assuming that the average density of the elastic material before strain is 1.0.

[0040] In step S2 of this embodiment, an tensile strain is applied to the test piece 10, and therefore, voids 15 can be generated more efficiently inside the elastic material (test piece 10) than when, for example, other strains (e.g., compressive strain or shear strain) are applied.

[0041] In step S2, it is desirable to make the strain applied to the test piece 10 reach a predetermined first threshold value. This allows a constant strain (first threshold value) to be applied to the test piece 10, enabling quantitative performance evaluation. The first threshold value (strain) is expressed as a ratio obtained by dividing the deformation length of the test piece 10 after the strain is applied (the change in the elongation direction from before the strain is applied) by the height of the test piece 10 before the strain is applied (the length in the elongation direction). In this embodiment, the first threshold value is set to 0.2.

[0042] The first threshold value can be set appropriately depending on the stiffness of the elastic material, the performance to be evaluated, etc. The first threshold value is preferably 0.2 or more. By setting the first threshold value to 0.2 or more, voids 15 (shown in Figs. 4(a) and (b)) necessary for evaluating the performance of the elastic material can be formed inside the test piece 10 (elastic material). On the other hand, if the first threshold value is large, a new void (not shown) formed by connecting adjacent voids 15, 15 may become larger than necessary, which may make it difficult to evaluate the performance of the elastic material. From this viewpoint, the first threshold value is preferably 1.0 or less.

[0043] In this embodiment, after the distortion reaches the first threshold value in step S2, the distortion (first threshold value) is maintained in step S3 which is performed thereafter.

[0044] [Image of test piece] Next, in the performance evaluation method of this embodiment, as shown in Fig. 1, the test piece 10 is irradiated with X-rays to obtain a projection image of the test piece 10 (step S3). In step S3 of this embodiment, projection images of the test piece 10 are obtained at multiple times after the formation of the void 15. The projection images are obtained by computer tomography.

[0045] In step S3 of this embodiment, first, as shown in FIG. 1, X-rays are irradiated from the X-ray tube 31 to the test piece 10. The X-rays pass through the test piece 10 and are detected by the detector 32. The detected X-rays are converted into an electric signal. The electric signal is output to the computer 8. The electric signal is processed by the computer 8 to obtain a projection image of the test piece 10.

[0046] In step S3 of this embodiment, a plurality of projection images (rotation series images) are obtained by rotating the test piece 10 around the axis. Such a plurality of projection images (rotation series images) are reconstructed by a computer tomography method in step S41 for constructing a tomographic image, which will be described later, to obtain a three-dimensional tomographic image of the test piece 10. Figures 4(a) and (b) show tomographic images 33 of the test piece 10. These tomographic images 33 show cross sections of the test piece 10 cut along any plane perpendicular to the axial direction of the test piece 10 shown in Figure 1. The voids 15 are shown in black.

[0047] The brightness of the X-rays can be set appropriately. The brightness of the X-rays is closely related to the S / N ratio of the X-ray scattering data. If the brightness of the X-rays is low, the signal strength tends to be weaker than the statistical error of the X-rays, and it may be difficult to obtain data with a sufficiently good S / N ratio even if the measurement time is extended. From this perspective, the brightness of the X-rays (photons / s / mrad) 2 / mm 2 / 0.1%bw) is preferably 10 10 More preferably, it is 10 12 That's all.

[0048] The decay time of the phosphor 32a for converting X-rays into visible light can be appropriately set. As in the patent document (JP 2017-83182 A), the decay time is preferably 100 ms or less, more preferably 50 ms or less, and even more preferably 10 ms or less, from the viewpoint of preventing the afterimage of a previously captured projection image from affecting a subsequently captured projection image, similarly to the patent document (JP 2017-83182 A).

[0049] In step S3 of the present embodiment, projection images of the test piece 10 are acquired at a plurality of times after the voids 15 are formed (in this example, after step S2 of forming the voids 15). As a result, in step S3, projection images of the test piece 10 in which the size (volume) of the voids 15 changes from moment to moment as the destruction of the internal structure (bonds of molecular chains) of the elastic material progresses can be acquired at each time.

[0050] The multiple times can be set as appropriate. The multiple times in this embodiment include a first time when the strain applied to the test piece 10 reaches a first threshold value. This allows a projection image of the test piece 10 immediately after a certain strain (first threshold value) is applied (when the voids 15 required for performance evaluation are formed) to be acquired in step S3.

[0051] The multiple times in this embodiment include a second time after a predetermined time has elapsed from the first time. The predetermined time (hereinafter, sometimes referred to as "elapsed time") is not particularly limited as long as a projection image of the test piece 10 in which the size (volume) of the void 15 has changed since the first time is acquired, but is desirably set to 100 to 1200 seconds. By setting the elapsed time to 100 seconds or more, the volume of the void 15 at the second time can be reliably changed (enlarged) from the volume of the void 15 at the first time. On the other hand, by setting the elapsed time to 1200 seconds or less, the time required to acquire the projection image can be prevented from becoming unnecessarily large. From this viewpoint, the elapsed time is preferably 400 seconds or more and preferably 800 seconds or less. FIG. 4(a) shows a tomographic image 33 of the test piece 10 acquired at the first time. FIG. 4(b) shows a tomographic image 33 of the test piece 10 acquired at the second time.

[0052] In this embodiment, the strain applied to the test piece 10 is maintained at a first threshold value at the multiple times at which the projection images are acquired. This allows projection images of the test piece 10 in which the volume of the void 15 has changed based on a constant strain to be acquired at the multiple times. The projection images of the test piece 10 acquired at the multiple times (e.g., the first time and the second time) are input to a projection image input unit 16A (shown in FIG. 2) of the computer 8.

[0053] [Specify volume change] Next, in the performance evaluation method of the present embodiment, the volume change of the voids 15 between a plurality of times is identified from the projected image of the test piece 10 as one of the performance indexes (volume change identifying step S4).

[0054] In the volume change specifying step S4 of this embodiment, first, as shown in Fig. 2, a projection image (not shown) of the test piece 10 inputted to the projection image input unit 16A and a volume change specifying program 17A are read into the working memory 13C. Then, the volume change specifying program 17A is executed by the calculation unit 13A, whereby the computer 8 can function as the volume change specifying unit 4 for specifying the volume change of the voids 15 between a plurality of times. Fig. 5 is a flowchart showing the processing procedure of the volume change specifying step S4 of this embodiment.

[0055] [Compose the tomographic image] In the volume change determination step S4 of this embodiment, first, a tomographic image 33 (shown in FIGS. 4(a) and 4(b) as an example) of the test piece 10 is constructed (step S41) using a projection image of the test piece 10. As described above, in step S41 of this embodiment, a plurality of tomographic images 33 obtained by cutting the test piece 10 at any plane that intersects perpendicularly to the axial direction of the test piece 10 are obtained using the projection image of the test piece 10.

[0056] The tomographic images 33 in this embodiment are acquired at any interval (for example, 5 to 30 μm) between one end (not shown) and the other end 10b in the axial direction of the test piece 10 shown in FIG. 1. The number of tomographic images 33 can be set appropriately. In this embodiment, the number is 150 to 300.

[0057] In step S41 of this embodiment, a plurality of tomographic images 33 are constructed for each of the projection images acquired at a plurality of times (in this example, a first time and a second time). Fig. 4(a) shows one tomographic image 33 constructed from the projection images acquired at the first time as a representative. Fig. 4(b) shows one tomographic image 33 constructed from the projection images acquired at the second time as a representative.

[0058] [Measure density distribution] Next, in the volume change determination step S4 of this embodiment, the density distribution of the elastic material is measured from a plurality of tomographic images 33 (as an example, shown in Figures 4(a) and (b)) (step S42). In step S42 of this embodiment, first, in the area of ​​the test piece 10 displayed in each tomographic image 33, the brightness values ​​of the minute areas (pixels in this example) constituting each tomographic image 33 are obtained. In this embodiment, the brightness value is the lowest in the minute area of ​​the void 15. Furthermore, the higher the brightness value, the greater the density of the elastic material. In this way, a proportional relationship is established between the brightness value and the density.

[0059] Next, in step S42 of this embodiment, the luminance value of the elastic material before strain is applied (i.e., the portion without voids 15) is set to 1.0, and the luminance value where no elastic material is present (the lowest luminance value) is set to 0.0, and the luminance value ratio of each micro-region (pixel in this example) is calculated. Such a luminance value ratio is defined as a normalized density (i.e., the ratio to the density of the elastic material before strain is applied). By calculating the luminance value ratio in each micro-region of each tomographic image 33, the density distribution of the elastic material can be measured.

[0060] [Get volume of void] Next, in the volume change determination step S4 of this embodiment, the volume of the voids 15 is acquired based on the density distribution of the elastic material (step S43). As described above, the voids 15 are portions where the density of the elastic material when strain is applied is 0.0 to 0.1 when the density of the elastic material before strain is taken as 1.0. Therefore, in step S43, in the minute regions (pixels) of each tomographic image 33 (shown in Figs. 4(a) and 4(b) as an example), the minute regions (pixels) where the brightness value ratio (normalized density) is 0.0 to 0.1 are detected as the voids 15. To detect the voids 15, commercially available image processing software (for example, Photoshop (registered trademark) manufactured by Adobe) or the like is used.

[0061] In step S43 of this embodiment, for the multiple tomographic images 33 at the first time, the product of the area of ​​the void 15 detected in each tomographic image 33 and the interval at which the tomographic images 33 were acquired (for example, 5 to 30 μm) is added together to obtain the volume V0 of the void 15 at the first time. Furthermore, in step S43, for the multiple tomographic images 33 at the second time, the product of the area of ​​the void 15 detected in each tomographic image 33 and the interval at which the tomographic images 33 were acquired is added together to obtain the volume V t is obtained.

[0062] [Get void change] Next, in the volume change determination step S4 of this embodiment, the volume change of the void 15 between multiple times is acquired (step S44). In step S44 of this embodiment, the volume V0 of the void 15 at the first time and the volume V t V t / V0 is identified as the volume change of the void 15.

[0063] The volume change of the voids 15 indicates the increase (growth) in the volume of the voids 15 between a plurality of times (between the first time and the second time in this example). According to the experiments of the inventors, it was found that there is a certain correlation between the volume change between a plurality of times and the performance of the elastic material (in this example, the performance related to wear). In other words, it was found that an elastic material with a small volume change is less likely to undergo destruction of the internal structure (bonds of molecular chains) and has good performance. Therefore, in the performance evaluation method of this embodiment, the volume change of the voids is obtained as one of the indexes of the performance of the elastic material, and it becomes possible to predict the performance of the elastic material.

[0064] In this embodiment, when the volume of void 15 at a time (e.g., a third time, etc.) different from the first time and the second time is acquired, the volume change between those times (e.g., between the second time and the third time, etc.) may be acquired. The volume change of void 15 is input to volume change input unit 16B (shown in FIG. 2).

[0065] [Evaluation process] Next, as shown in FIG. 3, in the performance evaluation method of the present embodiment, the performance of the elastic material is evaluated based on the volume change of the voids 15 (step S5).

[0066] In step S5 of this embodiment, first, the volume change of the voids 15 inputted in the volume change input section 16B and the evaluation program 17B are read into the working memory 13C as shown in Fig. 2. Then, the evaluation program 17B is executed by the calculation section 13A, whereby the computer 8 can function as the evaluation section 5 that evaluates the performance of the elastic material.

[0067] In step S5 of the present embodiment, the volume change of the voids 15 is compared with a second threshold value determined in advance. As described above, an elastic material with a small volume change has good performance (in this example, performance related to wear) of the elastic material. From this perspective, in step S5 of the present embodiment, when the volume change of the voids 15 is equal to or less than the second threshold value, the performance of the elastic material is evaluated as good.

[0068] The second threshold value can be set appropriately depending on the performance required for the elastic material (in this example, performance related to wear). The second threshold value in this embodiment is set to 1.0 to 3.0 (in this example, 2.0).

[0069] In step S5, if the volume change of the voids 15 is equal to or less than the second threshold value (2.0 in this example) ("Yes" in step S5), the performance of the elastic material is evaluated as good. In this case, a product (e.g., a tire) using the elastic material (rubber) is designed and manufactured (step S6). This ensures that a product with excellent performance (in this example, performance related to wear) can be manufactured.

[0070] On the other hand, in step S5, if the change in volume of the voids 15 is greater than the second threshold value (2.0 in this example) ("No" in step S5), the performance of the elastic material is evaluated as not good. In this case, a new elastic material with a changed composition is produced (step S7), and steps S1 to S5 are carried out again. This makes it possible to reliably produce an elastic material with excellent performance (in this example, performance related to wear).

[0071] In the present embodiment, the performance related to wear (wear resistance performance) is evaluated, but the present invention is not limited to such an embodiment. For example, the tear resistance or crack resistance of the elastic material may be evaluated based on the volume change of the voids 15.

[0072] Although a particularly preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the illustrated embodiment and can be modified and carried out in various forms. EXAMPLES

[0073] For the elastic materials A to C, the wear-related performance (wear resistance performance) was evaluated based on the change in void volume determined by the method of the present invention. Furthermore, pneumatic tires having tread portions made of the elastic materials A to C were produced, respectively, and the wear resistance performance was evaluated by an actual vehicle running test. Then, the correlation between the evaluation of the wear resistance performance according to the present invention and the evaluation of the wear resistance performance by the actual vehicle running test was verified (Example).

[0074] For comparison, the abrasion resistance of the elastic materials A to C was evaluated using a Lambourn tester, and the correlation with the evaluation of the abrasion resistance by an actual vehicle running test was verified (Comparative Example).

[0075] The reagents used are as follows: 1. Polymer (1): (1 modifying group) 2. Polymer (2): (2 modified groups; different amount of monomer from polymer (1)) 3. Polymer (3): (3 modified groups; different monomer amounts from polymer (1)) 4. SBR: SPRINTAN SLR6430 made by STYRON 5.BR: BR150B manufactured by Ube Industries, Ltd. 6. Modifier: 3-(N,N-dimethylaminopropyl)trimethoxysilane manufactured by Azumax Corporation 7. Anti-aging agent: Nocrac 6C (N-1,3-dimethylbutyl-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. 8. Stearic acid: Stearin manufactured by Nippon Oil & Fats Co., Ltd. 9. Zinc oxide: Ginrei R manufactured by Toho Zinc Co., Ltd. 10. Aromatherapy oil: Diana Process AH-24 manufactured by Idemitsu Kosan Co., Ltd. 11. Wax: Sunnock Wax manufactured by Ouchi Shinko Chemical Industry Co., Ltd. 12. Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Co., Ltd. 13. Vulcanization accelerator (1): Noccela CZ manufactured by Ouchi Shinko Chemical Industry Co., Ltd. 14. Vulcanization accelerator (2): Noccelaer D manufactured by Ouchi Shinko Chemical Industry Co., Ltd. 15. Silica: Degussa Ultrasil VN3 16. Silane coupling agent: Degussa Si69 17. Carbon black: Diablack LH (N326, N2SA:84m) manufactured by Mitsubishi Chemical Corporation 2 / g)

[0076] Monomers and polymers (1) to (3) were synthesized in the same manner as described in the "Examples" of the patent document (JP 2017-83182 A). The test methods were as follows.

[0077] <Change in void volume> For each of the elastic materials A to C, a cylindrical test piece having a diameter of 20 mm and an axial length of 1 mm was prepared. Then, according to the procedure shown in FIG. 3, a strain (extension strain) was applied to the test piece, and a projection image of the test piece was acquired at a first time when the strain reached a first threshold value (0.2) and at a second time after a predetermined time (500 seconds) had elapsed from the first time. Then, according to the procedure shown in FIG. 5, the volume V0 of the void at the first time and the volume V of the void at the second time were acquired. tV t / V0 was obtained as the void volume change. The void volume change (ratio V t / V0) is smaller, the wear resistance is better.

[0078] <Lambourn test> For elastic materials A to C, the amount of wear was measured using a Lambourn abrasion tester under the conditions of room temperature, a load of 1.0 kgf, and a slip ratio of 30%, and the reciprocal was calculated. The results are expressed as an index with elastic material A being 100, and the larger the value, the more excellent the abrasion resistance.

[0079] <Actual vehicle driving test> Pneumatic tires of size 195 / 65R15 were made with treads made of elastic materials A to C. Each pneumatic tire was then mounted on a domestically produced FF vehicle, and the groove depth of the tread was measured after a mileage of 8,000 km, and the mileage per 1 mm of tread wear was calculated. The results are expressed as an index with elastic material A being 100, and the higher the value, the better the wear resistance. The test results are shown in Table 1.

[0080] [Table 1]

[0081] As a result of the test, as is clear from Table 1, the method of the embodiment had a good correlation with the actual vehicle running test compared to the comparative example, and various performances of the elastic material could be predicted (evaluated). Furthermore, in the embodiment, elastic materials B and C, whose void volume change was equal to or less than the second threshold value (1.5), were evaluated significantly better in the actual vehicle running test compared to elastic material A, whose void volume change was greater than the second threshold value, and various performances of the elastic material could be predicted with high accuracy. [Explanation of symbols]

[0082] S2: Process for forming voids S3: A process for acquiring a projection image of the test piece S4: A process for determining the change in void volume

Claims

1. 1. A method for evaluating the performance of elastic materials, including rubbers or elastomers, comprising: applying a strain to a test specimen of the elastic material to form at least one void within the test specimen; irradiating the test piece with X-rays at a plurality of times after the formation of the void, and acquiring projection images of the test piece; determining a change in volume of the void between the plurality of times from the projection image as one of the indicators of performance; and evaluating the performance based on the volume change; The elastic material is a rubber obtained by using one or more conjugated diene compounds, The rubber is a tire rubber, The performance is wear resistance performance, In the evaluating step, the performance is evaluated as being good when the volume change is 1.5 or less. Performance evaluation method.

2. A method for evaluating the performance of an elastic material, including a rubber or elastomer, comprising: applying a strain to a test specimen of the elastic material to form at least one void within the test specimen; irradiating the test piece with X-rays at a plurality of times after the formation of the void, and acquiring projection images of the test piece; and determining a change in volume of the void between the plurality of times from the projection image as one of the performance indicators; The plurality of times include a first time when the strain applied to the test piece reaches a predetermined first threshold value, and a second time after a predetermined time has elapsed from the first time. Performance evaluation method.

3. The performance evaluation method according to claim 2 , wherein the time is 100 to 1200 seconds.

4. The performance evaluation method according to claim 2 , wherein the first threshold is equal to or greater than 0.

2.

5. The step of determining the volume change includes determining the volume V of the void at the first time. 0 and the volume V of the void at the second time t Relative to V t / V 0 The performance evaluation method according to claim 2 , wherein the change in volume is specified as:

6. The performance evaluation method according to claim 2 , further comprising the step of evaluating the performance based on the volume change.

7. The performance evaluation method according to claim 6 , wherein the evaluating step evaluates the performance as good when the volume change is equal to or smaller than a second predetermined threshold value.

8. The performance evaluation method according to claim 7 , wherein the second threshold value is between 1.0 and 3.

0.

9. The performance evaluation method described in any one of claims 2 to 8, wherein the elastic material is a rubber obtained using one or more types of conjugated diene compounds.

10. The performance evaluation method described in claim 9, wherein the rubber is rubber for tires.

11. A performance evaluation method described in any one of claims 1 to 10, wherein the strain is an extensional strain.

12. The performance evaluation method according to claim 1, wherein the decay time of the phosphor for converting the X-rays into visible light is 100 ms or less.

13. The brightness of the X-rays (photons / s / mrad 2 / mm 2 / 0.1%bw) is 10 10 The performance evaluation method according to any one of claims 1 to 12, wherein

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