Evaluation method

Abstract

To provide an evaluation method capable of simply evaluating a percentage of voids in a rubber material.SOLUTION: An evaluation method comprises evaluating a percentage of voids in a strained rubber material based on φvoid calculated from the following formula (1), using the transmittance and thickness of the rubber material to which no strain is applied and the transmittance and thickness of the rubber material to which strain is applied.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This disclosure relates to a method for evaluating rubber materials. [Background technology]

[0002] It is known that when strain is applied to rubber materials, tiny voids (air pockets) are formed (see, for example, Non-Patent Documents 1 and 2). [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Macromolecules 2012,45,1529-1543 [Non-Patent Document 2] Macromolecules 2013,46,900-913 [Overview of the project] [Problems that the invention aims to solve]

[0004] Non-patent documents 1 and 2 quantitatively evaluate voids by measuring the change in scattering intensity of rubber materials associated with void formation using small-angle X-ray scattering (SAXS) measurements. While this method requires measurements over a wide wavenumber range, in practice, the observation surface of the detector is finite, resulting in measurements being limited to a specific wavenumber range. Therefore, there was room for improvement in that voids exist in regions that cannot be observed.

[0005] This disclosure aims to solve the aforementioned problems and provide an evaluation method that can easily evaluate the proportion of voids in a rubber material. [Means for solving the problem]

[0006] This disclosure relates to an evaluation method for evaluating the proportion of voids in a strained rubber material based on φvoid calculated from the following formula (1), using the transmittance and thickness of a rubber material without strain and the transmittance and thickness of a rubber material with strain applied.

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[0007] According to this disclosure, the proportion of voids in a strained rubber material can be easily evaluated by using the transmittance and thickness of a rubber material without strain applied and the transmittance and thickness of a rubber material with strain applied, and by φvoid calculated from equation (1). [Modes for carrying out the invention]

[0008] This disclosure provides an evaluation method for evaluating the proportion of voids in a strained rubber material based on φvoid calculated from the following formula (1), using the transmittance and thickness of a rubber material without strain and the transmittance and thickness of a rubber material with strain applied.

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[0009] When voids are formed in the rubber material, usually, while maintaining the mass, the volume increases, so the density decreases (ρ s <ρ0). Therefore, for a rubber material with a large void ratio, φvoid calculated by "1 - ρ s / ρ0" increases. Utilizing this relationship, the void ratio can be evaluated (quantitatively evaluated) from φvoid. Also, since φvoid can be calculated only from the transmittance and thickness of the rubber material, the void ratio can be easily evaluated. Furthermore, in the present disclosure, since voids in the X-ray irradiation volume can be evaluated, by irradiating the entire rubber material with X-rays, it becomes possible to evaluate the voids in the entire rubber material.

[0010] Here, the transmittance (I / I0) of the material is generally determined by the composition of the material and is expressed by the following formula (2). Therefore, by formula (2), "1 - ρ s / ρ0" can be transformed into an expression of transmittance and thickness.

Equation

[0011] In equation (1), the thickness (t) of the rubber material to which strain is applied. s The thickness may be measured by the actual thickness, or it may be calculated using the following formula (3).

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[0012] Assuming that the rubber material deforms with a Poisson's ratio of 0.5, there is no volume change, and therefore it can be treated as deforming at the same ratio in the direction perpendicular to the strain. Thus, from equation (3), the thickness (t) of the rubber material to which strain is applied can be calculated. s ) can be calculated. By using equation (3), the proportion of voids in the rubber material can be evaluated more easily.

[0013] Furthermore, φvoid can evaluate voids of all sizes that occupy the X-ray irradiation volume. There is no lower limit to the size that can be evaluated; the upper limit is the X-ray irradiation volume.

[0014] Examples of beams used to irradiate the rubber material include X-rays and light, with X-rays being preferred.

[0015] When using X-rays as the beam, the transmittance and scattering intensity of the rubber material may be measured by SAXS measurement. The scattering angle for SAXS measurement is usually 10 degrees or less.

[0016] SAXS measurements are typically performed in the region of q, which is expressed by the following formula.

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[0017] The region of q is 0.001 <q<0.05Å-1 It is preferable to include it.

[0018] In SAXS measurement, scattered X-rays are detected by an X-ray detector, and an image is generated by an image processing device or the like using the X-ray detection data from the X-ray detector.

[0019] For X-ray detection devices, for example, two-dimensional detectors (X-ray film, nuclear emulsion plates, X-ray imaging tubes, X-ray image intensifiers, X-ray imaging plates, X-ray CCDs, X-ray amorphous materials, etc.) and line sensor one-dimensional detectors can be used. The appropriate X-ray detection device should be selected depending on the type and state of the polymer material to be analyzed.

[0020] As an image processing device, one that can generate a normal X-ray scattering image based on X-ray detection data from an X-ray detection device can be used as appropriate.

[0021] The strain applied to the rubber material is preferably tensile strain, and more preferably uniaxial tensile strain. Uniaxial tensile strain can be applied, for example, by clamping the rubber material with a pair of opposing fixtures and stretching the rubber material in opposite directions with each fixture, or by clamping the rubber material with a pair of opposing fixtures, fixing one fixture and stretching the rubber material with the other fixture. The elongation rate when applying tensile strain to rubber materials is typically between 100 mm / min and 500 mm / min.

[0022] The shape of the rubber material is not particularly limited, but a plate shape or a dumbbell shape as described in JIS K6251 is preferred because it is easier to apply tensile strain uniformly.

[0023] The thickness of rubber material when no strain is applied is typically 1 mm to 2 mm.

[0024] Examples of rubber components included in rubber materials include isoprene rubber, styrene-butadiene rubber (SBR), butadiene rubber (BR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), and diene rubbers such as styrene-isoprene-butadiene copolymer rubber (SIBR). These may be used individually or in combination of two or more types.

[0025] The rubber material may contain fillers. Examples of fillers include silica, carbon black, calcium carbonate, talc, alumina, clay, aluminum hydroxide, aluminum oxide, and mica. Among these, silica and carbon black are preferred.

[0026] The rubber material may contain, in addition to rubber components and fillers, stearic acid, zinc oxide, sulfur, vulcanization accelerators, etc.

[0027] Rubber materials are manufactured using conventional methods. Specifically, they can be produced by mixing the compounding materials in a kneader such as a Banbury mixer or open roll, followed by vulcanization. [Examples]

[0028] The present disclosure will be described in detail based on examples, but the present disclosure is not limited to these examples.

[0029] <Composition of rubber material> 100 units of styrene-butadiene rubber (HPR850, manufactured by JSR) Silica (VN3 manufactured by Evonik) 53 parts Silane coupling agent (Si266 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Evonik) 4.26 parts Sulfur (powdered sulfur manufactured by Tsurumi Chemical Co., Ltd.) 1.5 parts Vulcanization accelerator 1 (Noxellar NS (N-tert--butyl-2-benzothiadylsulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) 2.0 parts Vulcanization accelerator 2 (Noxellar D (1,3-diphenylguanidine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) 2.3 parts

[0030] <Manufacturing method for rubber materials> According to the formulation instructions, the ingredients, excluding sulfur and vulcanization accelerator, were mixed in a 1.77-liter sealed Banbury mixer for 3 to 5 minutes until the temperature reached 150°C to obtain a base rubber mixture. Next, the base rubber mixture, sulfur, and vulcanization accelerator were mixed in an open roll mixer, and the resulting mixture was vulcanized to obtain a rubber material. The obtained rubber material was sliced ​​to a thickness of 1 mm, and then punched out into a dumbbell shape as described in JIS K6251. This was used as a sample for the following measurements.

[0031] <Examples> (SAXS measurement) The experiment was conducted at SPring-8 BL20XU. Ion chambers were placed before and after the sample, and the sample was irradiated with X-rays at 2-second intervals with 1-second exposures to obtain scattering intensity and transmittance. Furthermore, the same procedure was performed while uniaxial stretching strain was applied to the sample to obtain scattering intensity and transmittance. The stretching rate of the sample was set to 50 mm / min. Other conditions are as follows. X-ray brightness (8 keV): 9.5 × 10⁻¹⁴ 15 photons / s / mrad 2 / mm 2 / 0.1%bw X-ray photon count: 10 9 ~10 10 photons / s Distance from sample to detector: 2.58m Detector: PILATUS 100K (manufactured by Dectris) (Data processing) The φvoid was calculated using equation (1). The results are shown in Table 1. Note, s This was calculated from the strain amount (%) using equation (3).

[0032] [Table 1]

[0033] Table 1 shows that in the examples, φvoid increases as the amount of strain increases. Therefore, it was confirmed that quantitative evaluation of voids is possible by comparing φvoid.

[0034] <Comparative Example> Noise and background were subtracted from the scattering intensity measured in the examples, and φvoid was calculated using equations (1) to (3) from Non-Patent Document 2. The change in sample thickness due to stretching was corrected using the thickness obtained from the transmittance. In the comparative example, because the observable wavenumber range was narrow, quantitative data could not be obtained in the unobserved region.

[0035] This disclosure (1) is an evaluation method for evaluating the proportion of voids in a strained rubber material based on φvoid calculated from the following formula (1), using the transmittance and thickness of a rubber material to which no strain has been applied and the transmittance and thickness of a rubber material to which strain has been applied.

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[0036] Disclosure (2) is the evaluation method described in Disclosure (1) for calculating the thickness of a rubber material to which strain has been applied, assuming that the rubber material deforms with a Poisson's ratio of 0.5.

[0037] Disclosure (3) is the evaluation method described in Disclosure (1) or (2), wherein the strain is extensional strain.

[0038] Disclosure (4) is an evaluation method for any combination of the beam being X-rays as described in Disclosures (1) to (3).

[0039] Disclosure (5) is the evaluation method described in Disclosure (4) for measuring the transmittance and scattering intensity of a rubber material by small-angle X-ray scattering measurement.

[0040] Disclosure (6) is a method for evaluating a rubber material in any combination of any of Disclosures (1) to (5), including a filler.

Claims

1. An evaluation method for evaluating the proportion of voids in a rubber material to which strain has been applied, using the transmittance and thickness of a rubber material without strain applied and the transmittance and thickness of a rubber material to which strain has been applied, and utilizing the relationship that a rubber material with a larger proportion of voids has a larger φvoid, calculated from the following formula (1). [Math 1] ρ ０ Density of rubber material without applied strain ρ ｓ Density of rubber material under strain I / I ０ : Transmittance of rubber material without applied strain I ｓ / I ０ : Transmittance of strained rubber material I ０ : Intensity of the beam incident on the rubber material I: Intensity of a beam passing through a rubber material without strain applied. I ｓ The intensity of a beam passing through a strained rubber material. t ０ : Thickness of rubber material without applied strain t ｓ : Thickness of the rubber material to which strain is applied

2. The evaluation method according to claim 1, which calculates the thickness of a rubber material to which strain has been applied, assuming that the rubber material deforms with a Poisson's ratio of 0.

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

4. The evaluation method according to any one of claims 1 to 3, wherein the beam is X-rays.

5. The evaluation method according to claim 4, which measures the transmittance and scattering intensity of a rubber material by small-angle X-ray scattering measurement.

6. The evaluation method according to any one of claims 1 to 5, wherein the rubber material includes a filler.

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