Performance evaluation method for elastic materials

Abstract

To provide a method capable of evaluating performance of an elastic material.SOLUTION: A performance evaluation method for elastic material including rubber or elastomer, includes: step S2 of applying a strain to a test piece made of an elastic material to form at least one low-density portion inside the test piece; after forming the low-density portion, step S3 of obtaining projected images of the test piece by irradiating the test piece with X-rays at a predetermined first time and at a second time after the first time; step S4 of identifying the low-density portion based on the projected images at the first time; step S5 of identifying the low-density portion based on the projected images at the second time; step S6 of identifying a volume change of the at least one low-density portion between the first time and the second time; and step S7 of outputting the volume change as one of indicators of performance of the elastic material.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] BACKGROUND ART Conventionally, a method for evaluating the performance (for example, wear-related performance) of an elastic material is known in which the elastic material is subjected to abrasion using an indoor abrasion tester such as a Lambourn abrasion tester (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-308447 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 an elastic material.

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

[0006] The present disclosure provides 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 low-density rubber portion inside the test piece; after forming the low-density rubber portion, irradiating the test piece with X-rays to obtain projection images at a predetermined first time and at a second time that is a predetermined time after the first time; identifying the low-density rubber portion based on the projection image at the first time; identifying the low-density rubber portion based on the projection image at the second time; identifying a volume change between the low-density rubber portion at the first time and the low-density rubber portion at the second time; and outputting the volume change as one of the performance indicators. [Effects of the Invention]

[0007] The method for evaluating the performance of an elastic material according to the present disclosure employs the above steps, making it possible to evaluate the performance of an elastic material. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view of an apparatus for evaluating the performance of an elastic material according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram of a computer according to the present embodiment. [Figure 3] 1 is a flowchart showing a processing procedure of a performance evaluation method for an elastic material according to an embodiment of the present invention. [Figure 4] The figures show tomographic images of a strained specimen, where (a) is a tomographic image of the specimen acquired at a first time, and (b) is a tomographic image of the specimen acquired at a second time. [Figure 5] 10 is a flowchart showing a procedure of a first rubber portion identifying step. [Figure 6] 10 is a flowchart showing a procedure of a second rubber portion identifying step. [Figure 7] This is a tomographic image virtually divided into multiple regions. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. It should be understood that the drawings include exaggerated representations and representations that differ from the dimensional ratios of actual structures in order to facilitate understanding of the contents of the disclosure. Furthermore, identical or common elements are designated by the same reference numerals throughout the embodiments, and redundant explanations will be omitted. Furthermore, the specific configurations shown in the embodiments and drawings are intended to facilitate understanding of the contents of the present disclosure, and the present disclosure is not limited to the specific configurations shown in the drawings.

[0010] In the method for evaluating the performance of an elastic material 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.

[0011] [Elastic material] The elastic material is not particularly limited as long as it contains rubber or elastomer. An example of the elastic material of this embodiment is rubber obtained using one or more conjugated diene compounds. However, the elastic material is not limited to such rubber. Furthermore, an example of rubber (elastic material) is rubber for tires. An example of the performance evaluated by the method of this embodiment is performance related to wear (wear resistance).

[0012] [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.

[0013] The performance evaluation device 1 is for evaluating the performance of an elastic material 15. The performance evaluation device 1 of this embodiment includes a distortion applying unit 2, an imaging unit 3, a low-density rubber specifying unit 4, a volume change specifying unit 5, a volume change output unit 6, and an evaluation unit 7.

[0014] [Distortion section] The strain applying unit 2 of this embodiment is for applying strain to a test piece 10 made of an elastic material 15. The strain applying unit 2 of this embodiment has a pair of jigs 21 and 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.

[0015] While fixing one jig 21, the driving unit 23 moves the other jig 22 in a direction in which the jigs 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.

[0016] 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 able to rotate the test piece 10 and the jigs 21 and 22 around the axis of the test piece 10.

[0017] [Image capture unit] The imaging unit 3 of this embodiment is configured to irradiate the strained test piece 10 with X-rays 9 (shown by a dashed line in FIG. 1 ) 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 the X-rays 9 and a detector 32 that detects the X-rays 9 and converts them into an electrical signal. The detector 32 has a phosphor 32a that converts the X-rays 9 into visible light. The imaging unit 3 can obtain projection images of the entire circumference of the test piece 10 by capturing multiple projection images while the test piece 10 is rotated around its axis.

[0018] [Volume change identification and evaluation unit] The low-density rubber specifying unit 4, the volume change specifying unit 5, the volume change output unit 6, and the evaluation unit 7 of this embodiment are configured by a computer 8. Fig. 2 is a block diagram of the computer 8 of this embodiment.

[0019] As shown in FIGS. 1 and 2, a computer 8 of this embodiment includes an input unit 11 as an input device, an output unit 12 as an output device, and an arithmetic processing unit 13.

[0020] 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. As shown in Fig. 2, 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.

[0021] 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 unit 16 and a program unit 17.

[0022] The data section 16 of this embodiment includes a projection image input section 16A, a low-density rubber section input section 16B, and a volume change input section 16C. The data input to these sections will be explained in the processing procedure of the performance evaluation method described later.

[0023] The program unit 17 of this embodiment is configured as a computer program. The program unit 17 of this embodiment includes a low-density rubber specifying program 17A, a volume change specifying program 17B, a volume change output program 17C, and an evaluation program 17D. These program units 17A to 17D are executed by the calculation unit 13A, causing the computer 8 to function as the low-density rubber specifying unit 4, the volume change specifying unit 5, the volume change output unit 6, and the evaluation unit 7. These functions will be explained in the processing procedure of the performance evaluation method described later.

[0024] [Method for evaluating the performance of elastic materials (first embodiment)] Next, the processing procedure of the method for evaluating the performance of an elastic material according to this embodiment will be described with reference to Fig. 3, which is a flowchart showing the processing procedure of the method for evaluating the performance of an elastic material according to this embodiment.

[0025] [Fix the specimen] In the performance evaluation method of this embodiment, first, as shown in Fig. 1, a test piece 10 made of an elastic material 15 is fixed to jigs 21 and 22 (step S1). The test piece 10 of this embodiment uses the above-mentioned elastic material 15 having a uniform density distribution, and is formed into a cylindrical shape, for example, as in Patent Document (JP 2017-83182 A). 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 Patent Document (JP 2017-83182 A).

[0026] [Low density rubber part] Next, in the performance evaluation method of this embodiment, as shown in FIG. 3, strain is applied to the test piece 10 (shown in FIG. 1) to form at least one low-density rubber portion inside the test piece 10 (step S2).

[0027] In step S2 of this embodiment, as shown in FIG. 1, the driving unit 23 of the strain imparting unit 2 relatively moves the jigs 21 and 22 of the strain imparting unit 2 in a direction in which the jigs 21 and 22 move away from each other in the axial direction of the cylindrical test piece 10. As a result, in step S2, the test piece 10 can be stretched, and an tensile strain can be imparted to the test piece 10. FIG. 4 shows a tomographic image 33 of the test piece 10 to which strain has been imparted. FIG. 4(a) is the tomographic image 33 of the test piece 10 acquired at a first time. FIG. 4(b) is the tomographic image 33 of the test piece 10 acquired at a second time.

[0028] In step S2 of this embodiment, strain is applied to the test piece 10, causing local stress concentration inside the test piece 10, and the polymer (not shown) that constitutes the elastic material 15 moves to avoid the stress concentration. As a result, at least one low-density rubber portion 35 can be formed inside the test piece 10, as shown in Fig. 4. Here, the low-density rubber portion 35 is defined as a portion where the density of the elastic material 15 when strain is applied to the test piece 10 is 0.1 or more and less than 0.8, assuming that the average density of the elastic material 15 before strain is 1.0.

[0029] In step S2 of this embodiment, an elongation strain is applied to the test piece 10, and therefore, a low-density rubber portion 35 can be generated more efficiently inside the elastic material 15 (test piece 10) than when, for example, other strains (e.g., compressive strain, shear strain, etc.) are applied.

[0030] In step S2, it is desirable to allow the strain applied to the test piece 10 to reach a predetermined first threshold. This allows a constant strain (first threshold strain) to be applied to the test piece 10, enabling quantitative performance evaluation. In this embodiment, after the strain reaches the first threshold in step S2, the strain (first threshold) is maintained in step S3 (obtaining a projection image of the test piece 10), which is performed thereafter.

[0031] In this embodiment, the strain (first threshold value) is determined by the ratio obtained by dividing the deformation length (change in the elongation direction from before the strain was applied) of the test piece 10 (shown in Figure 1) after the strain was applied by the height (length in the elongation direction) of the test piece 10 before the strain was applied.

[0032] The first threshold is preferably set to 0.2 or greater. Setting the first threshold to 0.2 or greater makes it possible to efficiently form the low-density rubber portions 35 necessary for evaluating the performance of the elastic material 15, as shown in FIG. 4 . On the other hand, if the first threshold is set to an unnecessarily large value, the strain applied to the test piece 10 increases, and many of the low-density rubber portions 35 may develop (break) into voids 36. In such cases, the low-density rubber portions 35 may disappear, making it difficult to evaluate the performance of the elastic material 15 based on the low-density rubber portions 35. From this perspective, the first threshold is preferably set to 1.0 or less. Here, voids 36 are defined as portions where the density of the elastic material 15 when strain is applied to the test piece 10 is greater than 0.0 and less than 0.1, assuming that the average density of the elastic material 15 before strain is 1.0.

[0033] [Image of test piece] Next, in the performance evaluation method of this embodiment, as shown in FIG. 3, X-rays 9 are irradiated onto the test piece 10 (shown in FIG. 1) to obtain a projection image of the test piece 10 (step S3). In step S3 of this embodiment, after forming the low-density rubber portion 35 (shown in FIG. 4), projection images of the test piece 10 are obtained at a predetermined first time and at a second time a predetermined time after the first time. Note that the time at which the projection images are obtained is not particularly limited as long as it includes the first and second times. For example, projection images may be obtained at a plurality of times including the first and second times. In this embodiment, the projection images are obtained by computer tomography.

[0034] In step S3 of this embodiment, first, as shown in FIG. 1, X-rays 9 are irradiated onto the test piece 10 from the X-ray tube 31. The X-rays 9 pass through the test piece 10 and are detected by the detector 32. The detected X-rays 9 are converted into an electrical signal. The electrical signal is output to the computer 8. The electrical signal is processed by the computer 8 to obtain a projection image of the test piece 10.

[0035] In step S3 of this embodiment, multiple projection images (rotational series images) are acquired by rotating the test piece 10 around its axis. These multiple projection images (rotational series images) are reconstructed by computer tomography, and three-dimensional tomographic images 33 of the test piece 10 can be acquired, as shown in FIG. 4. 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 FIG. 1. In FIGS. 4(a) and (b), the voids 36 are displayed in black. Meanwhile, the low-density rubber portions 35 are displayed in a lighter black (gray) color than the voids 36.

[0036] The brightness of the X-rays 9 can be set appropriately. The brightness of the X-rays 9 is closely related to the S / N ratio of the X-ray scattering data. If the brightness of the X-rays 9 is low, the signal strength tends to be weaker than the statistical error of the X-rays 9, 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 9 (photons / s / mrad) 2 / mm 2 / 0.1%bw) is preferably 10 10 More preferably, 10 12 That's all.

[0037] The decay time of the phosphor 32a (shown in FIG. 1) for converting the X-rays 9 into visible light can be set to, for example, a range similar to that of a patent document (JP 2017-83182 A). Note that the decay time can be set appropriately according to, for example, the shutter interval time of the imaging unit 3.

[0038] In step S3 of the present embodiment, after the low-density rubber portion 35 (shown in FIG. 4) is formed in step S2, projection images of the test piece 10 are acquired at a first time and a second time (in this example, a plurality of times including the first and second times). As a result, in step S3, projection images of the test piece 10 in which the size (volume) of the low-density rubber portion 35 changes as the movement of the polymer (not shown) that constitutes the elastic material 15 progresses can be acquired at the first time and the second time, respectively.

[0039] The first time can be set as appropriate as long as it is a time after the low-density rubber portion 35 is formed on the test piece 10. The first time is preferably set to the time when the strain applied to the test piece 10 reaches the first threshold value. This makes it possible to acquire a projection image of the test piece 10 immediately after a certain strain (strain maintained at the first threshold value) is applied (in this example, the low-density rubber portion 35 required for performance evaluation is formed) in step S3.

[0040] The second time can be set as appropriate as long as it is a time a predetermined time has elapsed since the first time. The second time is preferably set to a time 0.1 to 1200 seconds after the first time. By setting the second time to a time 0.1 second or more after the first time, the volume of the low-density rubber portion 35 (shown in FIG. 4(b)) at the second time can be reliably changed (increased) from the volume of the low-density rubber portion 35 (shown in FIG. 4(a)) at the first time. On the other hand, by setting the second time to a time 1200 seconds or less after the first time, the time required to acquire the projection image at the second time can be prevented from being unnecessarily long. From this perspective, the second time is preferably a time 1.0 second or more after the first time, and more preferably a time 800 seconds or less after the first time.

[0041] In this embodiment, the strain applied to the test piece 10 is maintained at a first threshold value at a plurality of times including a first time and a second time. As a result, projection images of the test piece 10 in which the volume of the low-density rubber portion 35 has changed based on the constant strain can be acquired at the first time and the second time, respectively. The projection images of the test piece 10 are input to a projection image input unit 16A (shown in FIG. 2) of the computer 8.

[0042] [Identifying the low-density rubber part at the first time] Next, in the performance evaluation method of this embodiment, as shown in FIG. 3, the low-density rubber portion 35 is identified based on the projected image of the test piece 10 (shown in FIG. 1) at the first time (first rubber portion identification step S4).

[0043] In the first rubber portion identifying step S4 of this embodiment, first, as shown in Fig. 2, a projection image (not shown) of the test piece 10 at a first time input to the projection image input unit 16A and a low-density rubber identifying program 17A are read into the working memory 13C. Then, the low-density rubber identifying program 17A is executed by the calculation unit 13A, causing the computer 8 to function as the low-density rubber identifying unit 4 for identifying the low-density rubber portion 35 (shown in Fig. 4(a)) at the first time. Fig. 5 is a flowchart showing the processing procedure of the first rubber portion identifying step S4.

[0044] [Compose a tomographic image] In the first rubber portion identifying step S4 of this embodiment, first, a tomographic image 33 (shown in FIG. 4(a)) of the test piece 10 (shown in FIG. 1) is constructed using a projection image of the test piece 10 at a first time (step S41). In step S41 of this embodiment, a plurality of tomographic images 33 obtained by cutting the test piece 10 along any plane that intersects perpendicularly with the axial direction of the test piece 10 are obtained using the projection image of the test piece 10.

[0045] In this embodiment, the tomographic images 33 are acquired at arbitrary intervals between one end (not shown) and the other end 10b in the axial direction of the test piece 10 shown in FIG. 1. The intervals in this embodiment are set to 2 to 10 μm (5 μm in this example). The number of tomographic images 33 can be set appropriately. In this embodiment, the number is 5 to 20 (10 in this example). FIG. 4(a) shows one tomographic image 33 composed of projection images acquired at a first time as a representative example.

[0046] [Measure density distribution] Next, in the first rubber portion identifying step S4 of this embodiment, the density distribution of the elastic material 15 is measured from the multiple tomographic images 33 (shown in FIG. 4(a)) (step S42). In step S42 of this embodiment, first, in the region of the test piece 10 displayed in each tomographic image 33, the brightness values ​​of the minute regions (pixels in this example) constituting each tomographic image 33 are acquired.

[0047] In this embodiment, the higher the brightness value, the greater the density of the elastic material 15, and for example, the brightness value of the minute region representing the void portion 36 is the lowest. Therefore, a proportional relationship is established between the brightness value and the density.

[0048] Next, in step S42 of this embodiment, the ratio of brightness values ​​is calculated for each micro-region (pixel in this example) constituting the tomographic image 33. In this embodiment, the brightness value of the elastic material 15 before strain is applied (i.e., when there are no low-density rubber portions 35 or void portions 36) is set to 1.0, and the brightness value (lowest brightness value) when no elastic material 15 is present is set to 0.0, and the ratio of brightness values ​​for each micro-region is calculated. Such a brightness value ratio is defined as a normalized density (i.e., a ratio to the density of the elastic material 15 before strain is applied). By calculating the brightness value ratio in each micro-region of each tomographic image 33, the density distribution of the elastic material 15 can be measured.

[0049] Next, in a first rubber portion identification step S4 of this embodiment, a low-density rubber portion 35 at a first time is identified based on the density distribution of the elastic material 15 (step S43). As described above, the low-density rubber portion 35 is a portion where the density of the elastic material 15 when strain is applied is 0.1 or more and less than 0.8, assuming that the density of the elastic material 15 before strain is 1.0. Therefore, in step S43 of this embodiment, a minute region (pixel) in each tomographic image 33 (shown in FIG. 4(a) as an example) where the ratio of brightness values ​​(normalized density) is 0.1 or more and less than 0.8 is identified as the low-density rubber portion 35.

[0050] For example, commercially available image processing software (for example, Photoshop (registered trademark) manufactured by Adobe Systems Incorporated) may be used to detect the low-density rubber portion 35. The identified low-density rubber portion 35 at the first time (i.e., a minute region where the ratio of brightness values ​​is equal to or greater than 0.1 and less than 0.8) is input to a low-density rubber portion input unit 16B (shown in FIG. 2) of the computer 8.

[0051] [Identifying the low-density rubber part at time 2] Next, in the performance evaluation method of this embodiment, as shown in Figure 3, the low-density rubber portion 35 (shown in Figure 4(b)) is identified based on the projected image of the test piece 10 (shown in Figure 1) at a second time (second rubber portion identification step S5).

[0052] In the second rubber portion identifying step S5 of this embodiment, first, as shown in Fig. 2, a projection image (not shown) of the test piece 10 at a second time input to the projection image input unit 16A and a low-density rubber identifying program 17A are read into the working memory 13C. Then, the low-density rubber identifying program 17A is executed by the calculation unit 13A, causing the computer 8 to function as the low-density rubber identifying unit 4 for identifying the low-density rubber portion 35 at the second time. Fig. 6 is a flowchart showing the processing procedure of the second rubber portion identifying step S5.

[0053] In the second rubber portion identifying step S5 of this embodiment, similarly to the first rubber portion identifying step S4 shown in FIG. 5, first, a plurality of tomographic images 33 (shown in FIG. 4(b)) of the test piece 10 are constructed using projected images of the test piece 10 at a second time (step S51). Next, in the second rubber portion identifying step S5, the density distribution of the elastic material 15 is measured from the plurality of tomographic images 33 (shown in FIG. 4(b) as an example) (step S52), and a low-density rubber portion 35 at the second time is identified based on the identified density distribution of the elastic material 15 (step S53). The identified low-density rubber portion 35 at the second time (i.e., a minute region where the ratio of brightness values ​​is equal to or greater than 0.1 and less than 0.8) is input to the low-density rubber portion input unit 16B (shown in FIG. 2) of the computer 8.

[0054] [Volume change determination process] Next, in the performance evaluation method of this embodiment, as shown in Figure 3, the volume change between the low-density rubber portion 35 at the first time (shown in Figure 4(a)) and the low-density rubber portion 35 at the second time (shown in Figure 4(b)) is identified (step S6).

[0055] 2, in step S6 of the present embodiment, first, the low-density rubber portion 35 at the first time and the low-density rubber portion 35 at the second time, which are input to the low-density rubber portion input unit 16B, are loaded into the working memory 13C. Furthermore, the volume change specifying program 17B is loaded into the working memory 13C. Then, the volume change specifying program 17B is executed by the calculation unit 13A, thereby causing the computer 8 to function as the volume change specifying unit 5 for specifying a volume change.

[0056] In step S6 of this embodiment, first, the volume of the low-density rubber portion 35 at the first time is acquired. In this embodiment, in each tomographic image 33 (shown in FIG. 4(a)) at the first time, the product of the total area of ​​the low-density rubber portion 35 and the interval (5 μm in this example) at which the tomographic image 33 is acquired is acquired as the volume of the low-density rubber portion 35 in each tomographic image 33. Then, the volumes of the low-density rubber portion 35 in these tomographic images 33 are added together to acquire the volume V0 of the low-density rubber portion 35 at the first time.

[0057] Next, in step S6 of this embodiment, the volume of the low-density rubber portion 35 at the second time is acquired. In this embodiment, in each tomographic image 33 (shown in FIG. 4(b)) at the second time, the product of the total area of ​​the low-density rubber portion 35 and the interval (5 μm in this example) at which the tomographic image 33 is acquired is acquired as the volume of the low-density rubber portion 35 in each tomographic image 33. Then, the volumes of the low-density rubber portion 35 in these tomographic images 33 are added together to obtain the volume V of the low-density rubber portion 35 at the second time. t is obtained.

[0058] Next, in step S6 of this embodiment, the volume change between the low-density rubber portion 35 at the first time (shown in FIG. 4(a)) and the low-density rubber portion 35 at the second time (shown in FIG. 4(b)) is determined. In this embodiment, the volume V0 of the low-density rubber portion 35 at the first time and the volume V t Relative to V t / V0 is obtained. This ratio V t / V0 is specified as the volume change of the low density rubber portion 35.

[0059] The volume change (relative V t / V0) indicates the increase (growth) in the volume of the low-density rubber portion 35 between the first time and the second time. As a result of extensive research, the present inventors have found that as the volume of the low-density rubber portion 35 increases, the low-density rubber portion 35 turns into a void portion (destruction) 36, and that the volume change (ratio V t It has been found that there is a certain correlation between the volume change (ratio V t In the elastic material 15 having a small value of tensile strength / V0, destruction of the internal structure (polymer bonds not shown) is less likely to progress, and the performance of the elastic material 15 tends to be good.

[0060] In the performance evaluation method of this embodiment, the volume change (ratio V t / V0), it becomes possible to evaluate the performance of the elastic material 15. Furthermore, in the performance evaluation method of this embodiment, when evaluating the performance of an elastic material 15 in which the low-density rubber portion 35 tends to be formed at an earlier stage than the void portion 36, for example, the performance can be evaluated based on the low-density rubber portion 35, so there is no need to take a long time to form the void portion 36. Therefore, in the performance evaluation method of this embodiment, it becomes possible to evaluate the performance of the elastic material 15 in a short time. The volume change of the low-density rubber portion 35 (ratio V t / V0) is input to the volume change input unit 16C of the computer 8 shown in FIG.

[0061] [Output low density rubber part] Next, in the performance evaluation method of this embodiment, as shown in FIG. 3, the volume change of the low-density rubber portion 35 (ratio V t / V0) is output as one of the properties of the elastic material 15 (step S7).

[0062] In step S7 of this embodiment, first, as shown in FIG. 2, the volume change (ratio Vt / V0) and the volume change output program 17C are loaded into the working memory 13C. Then, the volume change output program 17C is executed by the calculation unit 13A, and the computer 8 is configured to calculate the volume change (ratio V t / V0).

[0063] Volume change of low density rubber part 35 (relative V t / V0) can be output appropriately. t / V0) may be displayed on a display device constituting the output unit 12, or may be printed on a printer or the like. t / V0) to the operator. t / V0), cross-sectional images of the test piece at the first time and the second time (FIGS. 4(a) and 4(b)) may also be output.

[0064] As described above, the volume change of the low-density rubber portion 35 (relative V t / V0) indicates the increase (growth) in the volume of the low-density rubber portion 35 between the first time and the second time, and the volume change (ratio V t The smaller the volume change (ratio V t / V0) is output as an index of the performance of the elastic material 15, making it possible to evaluate the performance of the elastic material 15. [Evaluation process] Next, in the performance evaluation method of this embodiment, as shown in FIG. 3, the volume change of the low-density rubber portion 35 (ratio V t / V0), the performance of the elastic material 15 (shown in FIG. 1) is evaluated (step S8).

[0065] In step S8 of this embodiment, first, as shown in FIG. 2, the volume change (ratio V t / V0) and the evaluation program 17D are loaded into the working memory 13C. Then, the evaluation program 17D is executed by the calculation unit 13A, whereby the computer 8 can function as the evaluation unit 7 for evaluating the performance of the elastic material 15.

[0066] In step S8 of this embodiment, the volume change of the low-density rubber portion 35 (relative V t / V0) is compared with a second predetermined threshold value. t The elastic material 15 having a small ratio V t / V0) is equal to or less than the second threshold value, the performance of the elastic material 15 is evaluated as good.

[0067] The second threshold value can be set appropriately depending on, for example, the performance (in this example, performance related to wear) required of the elastic material 15. In this embodiment, the second threshold value is set to 1.0 to 3.0 (in this example, 2.0).

[0068] In step S8, the volume change (ratio V t If the value of V / V0 is equal to or less than the second threshold value (2.0 in this example) ("Yes" in step S8), the performance of the elastic material 15 is evaluated as good. In this case, a product (e.g., a tire) using the elastic material 15 (rubber) is designed and manufactured (step S9). This ensures that a product with excellent performance (in this example, performance related to wear) can be manufactured.

[0069] On the other hand, in step S8, the volume change of the low-density rubber portion 35 (ratio V t If the difference (V / V0) is greater than the second threshold (2.0 in this example) ("No" in step S8), the performance of the elastic material 15 is evaluated as not being good. In this case, a new elastic material 15 with a modified formulation is produced (step S10), and steps S1 to S8 are performed again. This ensures that an elastic material 15 with excellent performance (wear-related performance in this example) is produced.

[0070] [Method for evaluating the performance of elastic materials (second embodiment)] In the above embodiments, the performance related to wear (wear resistance) is evaluated, but the present invention is not limited to this. For example, the tear resistance or crack resistance of the elastic material 15 may be evaluated based on the volume change of the low-density rubber portion 35.

[0071] [Method for evaluating performance of elastic material (third embodiment)] In the embodiments described above, the low-density rubber portion 35 is identified for each minute region (pixel) of the tomographic image 33 shown in Figures 4(a) and (b), but the present invention is not limited to such an embodiment. For example, the tomographic image 33 may be virtually divided into a plurality of regions larger than the minute region (pixel), and the low-density rubber portion 35 may be identified for each of these regions. Figure 7 shows the tomographic image 33 virtually divided into a plurality of regions 40. In Figure 7, the background of the tomographic image 33 is omitted.

[0072] In this embodiment, the regions 40 are divided into a grid pattern, but are not limited to this. In the first rubber portion identifying step S4 and the second rubber portion identifying step S5 of this embodiment, the average value of the ratio of brightness values ​​of minute regions (pixels) constituting each region 40 is identified. Then, among the plurality of regions 40, a region 40 in which the average value of the ratio of minute regions (pixels) is equal to or greater than 0.1 and less than 0.8 is identified as a low-density rubber portion 35.

[0073] As the number of minute regions (images) where the ratio of brightness values ​​is equal to or greater than 0.1 and less than 0.8 increases from the first time to the second time, the number of regions 40 identified as the low-density rubber portion 35 also increases. Therefore, in the process S6 of identifying a volume change, the volume (total volume) V0 of the regions 40 identified as the low-density rubber portion 35 at the first time and the volume (total volume) V t Relative to V t / V0 is obtained.

[0074] In this embodiment, the tomographic image 33 is virtually divided into regions 40 larger than a minute region (pixel), so that, for example, the tendency of occurrence of low-density rubber portions 35 can be evaluated for each region 40. This makes it possible to easily identify the portions (regions 40) of the test piece 10 where low-density rubber portions 35 are likely to occur.

[0075] Although particularly preferred embodiments of the present disclosure have been described in detail above, the present disclosure is not limited to the illustrated embodiments and can be modified and implemented in various forms. [Example]

[0076] For elastic materials A to C, the wear performance (wear resistance performance) was evaluated based on the volume change of the low-density rubber portion obtained by the method of the present disclosure. Furthermore, pneumatic tires having tread portions made of the above elastic materials A to C were fabricated, and the wear resistance performance was evaluated by an actual vehicle running test. Then, the correlation between the wear resistance performance evaluation according to the present disclosure and the wear resistance performance evaluation by the actual vehicle running test was verified (Example).

[0077] 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 abrasion resistance in an actual vehicle running test was verified (Comparative Example).

[0078] The reagents used are as follows: 1. Polymer (1): (One modifying group; polymer polymerized according to JP 2010-116554 A) 2. Polymer (2): (2 modified groups; different amount of monomer from polymer (1)) 3. Polymer (3): (3 modified groups; different amount of monomer from polymer (1)) 4. SBR: STYRON SPRINTAN SLR6430 5.BR: BR150B manufactured by Ube Industries, Ltd. 6. Modifier: 3-(N,N-dimethylaminopropyl)trimethoxysilane manufactured by AZMAX Corporation 7. Antioxidant: 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. Aroma 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): Noccela 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: 84 m2 / g) manufactured by Mitsubishi Chemical Corporation

[0079] Monomers and polymers (1) to (3) were synthesized by the same procedure as described in the "Examples" of Patent Document (JP 2017-83182 A). The test methods were as follows.

[0080] <Volume change of low-density rubber part> For elastic materials A to C, cylindrical test pieces with a diameter of 20 mm and an axial length of 1 mm were prepared. Then, according to the procedure shown in Figure 3, strain (extension strain) was applied to the test pieces, and projection images of the test pieces were acquired at the first time when the strain reached a first threshold value (0.6) and at the second time after a predetermined time (0.2 seconds) had elapsed from the first time. Then, the volume V0 of the low-density rubber portion at the first time and the volume V of the low-density rubber portion at the second time were calculated. t Relative to V t / V0 was obtained as the volume change of the low density rubber part. t The smaller the value of V0 / V, the better the wear resistance.

[0081] <Lambourn test> For elastic materials A to C, the amount of wear was measured using a Lambourn abrasion tester under conditions of room temperature, a load of 1.0 kgf, and a slip ratio of 30%, and the reciprocal of the measured amount was calculated. The results are expressed as an index with elastic material A being 100, and the larger the value, the better the abrasion resistance.

[0082] <Actual vehicle driving test> Pneumatic tires of size 195 / 65R15 were fabricated with tread portions made of elastic materials A to C. Each pneumatic tire was then mounted on a domestically produced front-wheel drive vehicle, and the groove depth of the tread portion was measured after a driving distance of 8,000 km, and the driving distance per 1 mm of tread wear was calculated. The results were expressed as an index, with elastic material A being 100, and a higher index value indicates better wear resistance. The test results are shown in Table 1.

[0083] [Table 1]

[0084] As a result of the test, as is clear from Table 1, the method of the example had a better correlation with the actual vehicle running test than the comparative example, and was able to predict (evaluate) various performances of the elastic material. Furthermore, in the example, elastic materials B and C, whose volume change in the low-density rubber portion was equal to or less than the second threshold value (1.2), were evaluated significantly better in the actual vehicle running test than elastic material A, whose volume change in the low-density rubber portion was greater than the second threshold value, and various performances of the elastic material were able to be predicted with high accuracy.

[0085] [Note] The present disclosure includes the following aspects.

[0086] [Disclosure 1] 1. A method for evaluating the performance of elastic materials, including rubbers or elastomers, comprising: applying a strain to the test piece made of the elastic material to form at least one low-density rubber portion inside the test piece; a step of irradiating the test piece with X-rays and acquiring projection images at a predetermined first time and a second time that is a predetermined time after the first time, after forming the low-density rubber portion; identifying the low-density rubber portion based on the projection image at the first time; identifying the low-density rubber portion based on the projection image at the second time; determining a volume change between the low-density rubber portion at the first time and the low-density rubber portion at the second time; and outputting the volume change as one of the performance indicators. Performance evaluation method. [Disclosure 2] The performance evaluation method according to Disclosure 1, wherein the first time is the time when the distortion reaches a predetermined first threshold value. [Disclosure 3] The performance evaluation method according to Disclosure 2, wherein the first threshold is 0.2 or greater. [Disclosure 4] The performance evaluation method according to any one of Disclosures 1 to 3, wherein the second time is a time after 0.1 to 1200 seconds have elapsed since the first time. [Disclosure 5] The step of specifying the volume change includes determining a volume V0 of the low-density rubber portion at the first time and a volume V of the low-density rubber portion at the second time. t Relative to V t The performance evaluation method according to any one of Disclosures 1 to 4, wherein / V0 is specified as the volume change. [Disclosure 6] The ratio V t The performance evaluation method according to the present disclosure 5, comprising the step of evaluating the performance as good when / V0 is equal to or less than a predetermined second threshold. [Disclosure 7] The performance evaluation method according to the present disclosure 6, wherein the second threshold is 1.0 to 3.0. [Disclosure 8] The performance evaluation method according to any one of Disclosures 1 to 7, wherein the strain is tensile strain. [Disclosure 9] The performance evaluation method according to any one of Disclosures 1 to 8, wherein the elastic material is a rubber obtained using one or more conjugated diene compounds. [Disclosure 10] The performance evaluation method according to Disclosure 9, wherein the rubber is rubber for tires. [Disclosure 11] The brightness of the X-ray (photons / s / mrad 2 / mm 2 / 0.1%bw) is 10 10 The performance evaluation method according to any one of Disclosures 1 to 10 above. [Explanation of symbols]

[0087] S2: Process for forming low density rubber part S3: Obtaining a projection image of the test piece S4: A step of identifying a low-density rubber portion at a first time S5: A step of identifying a low-density rubber portion at a second time S6: Process for identifying the volume change of the low density rubber part S7: Process for outputting the volume change of the low-density rubber part

Claims

1. 1. A method for evaluating the performance of elastic materials, including rubbers or elastomers, comprising: applying a strain to the test piece made of the elastic material to form at least one low-density rubber portion inside the test piece; a step of irradiating the test piece with X-rays and acquiring projection images at a predetermined first time and a second time that is a predetermined time after the first time, after forming the low-density rubber portion; identifying the low-density rubber portion based on the projection image at the first time; identifying the low-density rubber portion based on the projection image at the second time; determining a volume change between the low-density rubber portion at the first time and the low-density rubber portion at the second time; and outputting the volume change as one of the performance indicators. Performance evaluation method.

2. The performance evaluation method according to claim 1 , wherein the first time is a time when the distortion reaches a predetermined first threshold value.

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

2.

4. 3. The performance evaluation method according to claim 1, wherein the second time is a time after 0.1 to 1200 seconds have elapsed since the first time.

5. The step of specifying the volume change includes determining the volume V of the low-density rubber portion at the first time. 0 and the volume V of the low-density rubber portion at the second time. t Relative to V t / V 0 The performance evaluation method according to claim 1 or 2, wherein the volume change is specified as:

6. The ratio V t / V 0 The performance evaluation method according to claim 5 , further comprising the step of evaluating the performance as good when the difference is equal to or less than a second predetermined threshold value.

7. 7. The performance evaluation method according to claim 6, wherein the second threshold is 1.0 to 3.

0.

8. The performance evaluation method according to claim 1 or 2, wherein the strain is an extensional strain.

9. 3. The performance evaluation method according to claim 1, wherein the elastic material is a rubber obtained by using one or more conjugated diene compounds.

10. The performance evaluation method according to claim 9, wherein the rubber is rubber for tires.

11. The brightness of the X-ray (photons / s / mrad 2 / mm 2 / 0.1%bw) is 10 10 The performance evaluation method according to claim 1 or 2, wherein:

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