Evaluation method

Abstract

To provide an evaluation method enabling evaluation of stress applied to bonding, which is hardly detected through Raman spectroscopy.SOLUTION: The evaluation method is provided comprising: using, for a rubber test piece, an infrared absorption spectrum obtained in a condition in which tensile force is not applied to the rubber test piece and an infrared absorption spectrum obtained in a condition in which tensile force is applied to the rubber test piece and calculating a shift quantity of a peak in the condition in which the tensile force is applied to the rubber test piece; and evaluating stress in the rubber test piece from the shift quantity of the peak.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for evaluating a rubber test piece. [Background technology]

[0002] A method for evaluating stress in the micro region of a polymer by Raman spectroscopy is known (see, for example, Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 15640 / 1983 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-145148 [Patent Document 3] Japanese Patent Application Laid-Open No. 2009-168562 Summary of the Invention [Problem to be solved by the invention]

[0004] When evaluating the stress on rubber test specimens, Raman spectroscopy can strongly detect highly symmetric bonds such as C=C bonds and SS bonds, but it is difficult to detect bonds with large charge imbalances such as C=O bonds and CH bonds. Therefore, it has been difficult to evaluate the stress on the latter bonds using Raman spectroscopy.

[0005] The present invention aims to solve the above problems and to provide an evaluation method that can evaluate the stress on a bond that is difficult to detect by Raman spectroscopy. [Means for solving the problem]

[0006] The present invention relates to an evaluation method for evaluating stress in a rubber test piece by calculating a peak shift amount when a tensile force is applied using an infrared absorption spectrum obtained with no tensile force applied to the rubber test piece and an infrared absorption spectrum obtained with a tensile force applied to the rubber test piece, and then evaluating the stress in the rubber test piece from the peak shift amount.

[0007] In the evaluation method, it is preferable to estimate a location where stress occurs in the rubber test piece from the amount of shift of the peak.

[0008] In the evaluation method, it is preferable to estimate the magnitude of the stress generated in the rubber test piece from the amount of shift of the peak.

[0009] The infrared absorption spectrum is preferably obtained by transmission Fourier transform infrared spectroscopy.

[0010] The thickness of the rubber test piece is preferably 20 μm or less. [Effects of the Invention]

[0011] According to the present invention, an infrared absorption spectrum obtained when no tensile force is applied to a rubber test piece and an infrared absorption spectrum obtained when a tensile force is applied to the rubber test piece are used to calculate the amount of peak shift when a tensile force is applied, and the stress in the rubber test piece is evaluated from the amount of peak shift.Therefore, this evaluation method makes it possible to evaluate the stress applied to bonds, which is difficult to detect by Raman spectroscopy. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a graph showing the relationship between the peak position of vinyl bonds in a rubber test piece 1 and strain. [Figure 2] 1 is a graph showing the relationship between the peak position of the trans coupling and strain in a rubber test piece 1. [Figure 3] 1 is a graph showing the relationship between the peak position of cis bonds in rubber test piece 1 and strain. [Figure 4]2 is a graph showing the relationship between the peak position of the aromatic ring portion of styrene in the rubber test piece 1 and strain. [Figure 5] 1 is a graph showing the relationship between the peak position of vinyl bonds in rubber test piece 2 and strain. [Figure 6] 1 is a graph showing the relationship between the peak position of the trans bond and strain in a rubber test piece 2. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention provides an evaluation method in which an infrared absorption spectrum obtained by measuring a rubber test piece with no tensile force applied thereto and an infrared absorption spectrum obtained by measuring a rubber test piece with a tensile force applied thereto are used to calculate the amount of peak shift when a tensile force is applied thereto, and the stress in the rubber test piece is evaluated from the amount of peak shift.

[0014] As shown in Figures 1 to 6, when infrared absorption spectra are measured under tensile stress, specific peaks shift. This shift can be used in the evaluation method described above to evaluate the stress of a rubber test piece. Furthermore, because the evaluation method uses infrared absorption spectra obtained by infrared spectroscopy, it can evaluate the stress on bonds, which is difficult to detect using Raman spectroscopy.

[0015] Furthermore, as shown in Figures 1 to 6, when tensile force is applied, there are bonds that cause a large peak shift and bonds that cause a small peak shift. Therefore, with the above evaluation method, it is possible to estimate the location of stress generation in a rubber test piece and the magnitude of stress in the rubber test piece from the peak shift. It is expected that utilizing these methods will contribute to the development of rubber materials that are less susceptible to stress concentration, i.e., less susceptible to fracture.

[0016] Furthermore, the peak shift caused by the application of tensile force basically occurs on the higher wavenumber side, as shown in Figure 1. This is thought to be due to the steric or electronic constraints on molecular vibration caused by the unraveling of polymer chains and changes in the bond dihedral angles. When the bond distance between atoms in a polymer is extended by a tensile force, the spring constant decreases, causing a peak shift to the lower wavenumber side.

[0017] The infrared absorption spectrum can be measured by, for example, Fourier transform infrared spectroscopy (FT-IR). The infrared absorption spectrum is preferably a second derivative spectrum, since this allows for sharper peaks.

[0018] FT-IR is roughly divided into transmission type and reflection type, but transmission type is preferred from the viewpoint of high measurement accuracy. In other words, it is preferable that the infrared absorption spectrum is obtained by transmission type FT-IR.

[0019] The measurement conditions for FT-IR are not particularly limited, but the measurement range is usually 4000 to 400 cm -1 The measurement temperature is 15 to 25° C., and the number of integration times is 8 to 128 (preferably 8 to 64).

[0020] The tensile force applied to the rubber test piece may be uniaxial or biaxial, but is preferably uniaxial. A uniaxial tensile force can be applied, for example, by a method in which the rubber test piece is clamped between a pair of opposing tensile jigs and pulled in opposite directions by each of the tensile jigs, or by a method in which the rubber test piece is clamped between a pair of opposing tensile jigs and one of the tensile jigs is fixed and the other tensile jig pulls the rubber test piece.

[0021] The shape of the rubber test piece is not particularly limited, but a plate shape or a dumbbell shape as defined in JIS K6251 is preferred in terms of facilitating the application of a uniform tensile force.

[0022] The thickness of the rubber test piece is preferably a thickness that allows transmission FT-IR to be performed, specifically, preferably 20 μm or less, more preferably 15 μm or less, and preferably 1 μm or more, more preferably 5 μm or more.

[0023] Examples of rubber components contained in the rubber test piece include diene rubbers such as isoprene rubber, styrene butadiene rubber (SBR), butadiene rubber (BR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), styrene-isoprene-butadiene copolymer rubber (SIBR), etc. These may be used alone or in combination of two or more.

[0024] The rubber test piece may contain fillers, stearic acid, zinc oxide, sulfur, vulcanization accelerators, etc. in addition to the rubber component.

[0025] The rubber test piece can be produced by a common method, such as by kneading the compounding materials in a kneading machine such as a Banbury mixer or an open roll mixer, followed by vulcanization. [Example]

[0026] The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

[0027] The various chemicals used in the examples will be explained below. SBR: NS616 manufactured by Zeon Corporation BR: BR1250H manufactured by Nippon Zeon Co., Ltd. Stearic acid: Tsubaki (NOF Corporation) Zinc oxide: Two types of zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: 5% oil-treated powder sulfur manufactured by Tsurumi Chemical Industry Co., Ltd. Vulcanization accelerator: Noccela NS (Nt-butyl-2-benzothiazole sulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0028] <Preparation of rubber test specimens> According to the formulation shown in the table below, materials other than sulfur and vulcanization accelerator were kneaded for 5 minutes at 150°C using an open roll mill to obtain a kneaded mixture. Sulfur and vulcanization accelerator were added to the kneaded mixture, and the mixture was kneaded for 5 minutes at 80°C using an open roll mill to obtain an unvulcanized rubber composition. The unvulcanized rubber composition was vulcanized at 170°C to obtain a vulcanized rubber composition. Plate-shaped rubber test pieces 1 and 2 were cut from the vulcanized rubber composition. A cryostat was used for cutting rubber test piece 1, and a microtome was used for cutting rubber test piece 2. The vulcanization time and dimensions (length x width x thickness) of rubber test pieces 1 and 2 are as follows. The vulcanization time was defined as t95 hours. (Rubber test piece 1) Vulcanization time: 35 minutes Size: 1cm x 2cm x 12μm (Rubber test piece 2) Vulcanization time: 20 minutes Size: 1cm x 1.5cm x 10μm

[0029] [Table 1]

[0030] [Table 2]

[0031] <Measurement of infrared absorption spectrum> FT-IR was performed on rubber test pieces 1 and 2 under the following conditions to measure the infrared absorption spectrum. The measurements were performed with and without tensile force applied. The measurements with tensile force applied were also performed multiple times, changing the tensile force. (Conditions) Infrared spectrophotometer: PerkinElmer Frontier Mode: Transmission measurement Measurement range: 4000~400cm -1 Accumulation count: 32 times Temperature: 23℃

[0032] The relationship between tensile force (strain) and peak position was graphed using infrared absorption spectra obtained with and without tensile force applied to the rubber test specimen. Graphs based on the results for rubber test specimen 1 are shown in Figures 1 to 4, and graphs based on the results for rubber test specimen 2 are shown in Figures 5 to 6.

[0033] Fig. 1 is a graph showing the relationship between the peak position of vinyl bonds and strain in rubber test piece 1, and Fig. 2 is a graph showing the relationship between the peak position of trans bonds and strain in rubber test piece 1. From these graphs, it can be seen that the peak positions of vinyl bonds and trans bonds shift to the high frequency side as strain increases.

[0034] 3 is a graph showing the relationship between the peak position of the cis bond in the rubber test piece 1 and strain, and FIG. 4 is a graph showing the relationship between the peak position of the aromatic ring portion of styrene in the rubber test piece 1 and strain. These graphs show that the peak positions of the cis bond and the styrene do not change much even when strain increases.

[0035] From the above results, it is believed that when a tensile force is applied to the rubber test piece 1, stress is generated mainly in the vinyl bond and trans bond portions.

[0036] Figure 5 is a graph showing the relationship between the peak position of vinyl bonds and strain in rubber test piece 2, and Figure 6 is a graph showing the relationship between the peak position of trans bonds and strain in rubber test piece 2. These graphs show that the peak position of vinyl bonds does not change much even when strain increases, and that the peak position of trans bonds shifts to the higher frequency side as strain increases.

[0037] From the above results, it is considered that when a tensile force is applied to the rubber test piece 2, stress is generated mainly in the transformer bond portion.

[0038] In addition, in the case of specimens in which the peak position shifts as the strain increases, as in Figures 1, 2, and 6, the relationship between strain and stress is determined, and then the relationship between the amount of peak shift and strain is determined. From this, the relationship between the amount of peak shift and stress can be determined, and the stress can be estimated.

Claims

1. An evaluation method in which an infrared absorption spectrum obtained with no tensile force applied to a rubber test piece and an infrared absorption spectrum obtained with tensile force applied to the rubber test piece are used to calculate the amount of peak shift when tensile force is applied, and the stress in the rubber test piece is evaluated from the amount of peak shift.

2. 2. The evaluation method according to claim 1, wherein a location where stress occurs in the rubber test piece is estimated from the amount of shift of the peak.

3. 2. The evaluation method according to claim 1, wherein the magnitude of the stress generated in the rubber test piece is estimated from the amount of shift of the peak.

4. 4. The evaluation method according to claim 1, wherein the infrared absorption spectrum is obtained by transmission Fourier transform infrared spectroscopy.

5. The evaluation method according to any one of claims 1 to 4, wherein the rubber test piece has a thickness of 20 µm or less.

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