JP6852538B2 - Mechanical property measurement method - Google Patents

Description

The present invention relates to a method for measuring mechanical characteristics of a polymer composite material including a structure such as a filler and a cross-linking material.

In order to meet the market demands and safety of polymer composite materials in recent years, it is necessary to highly control the mechanical properties. For that purpose, it is very important to measure the mechanical properties, especially on the nano to micro scale.

Atomic force microscopy and the like have been proposed as a method for evaluating mechanical properties on a nano to micro scale. However, various mechanical properties such as fillers such as silica and carbon black present in the polymer composite material, hardness of structures such as sulfur, vulcanization accelerator, and cross-linking material (cross-linking agent) such as zinc oxide can be accurately obtained. The reality is that it is difficult to measure.

The present invention solves the above problems and provides a method for measuring mechanical characteristics of a polymer composite material including a structure such as a filler and a cross-linking material, which can accurately measure the mechanical properties such as the hardness of the structure. With the goal.

The present invention is a method for measuring mechanical characteristics of a polymer composite material including a structure, and is characterized in that measurement is performed using a sample having a thickness determined based on the size of the structure in the polymer composite material. Regarding the method for measuring mechanical properties.

The structure is preferably at least one of a filler and a cross-linking material.
The size of the structure is preferably measured using a transmission electron microscope, a scanning electron microscope, or a scanning transmission X-ray microscope.

The sample is preferably adjusted to have a thickness comparable to the size of the structure in the polymer composite material.
It is preferable to measure the mechanical properties of the nano- to micro-scale polymer composite material in contact with the sample surface.

According to the present invention, it is a method for measuring mechanical physical characteristics of a polymer composite material including a structure, and the measurement is performed using a sample having a thickness determined based on the size of the structure in the polymer composite material. Therefore, it is possible to accurately measure the mechanical physical characteristics such as the hardness of the structure in the polymer composite material including the structure such as the filler and the cross-linking material.

An example of a schematic diagram of a measurement sample in the prior art and in the present invention. An example of a mapping image of the nitrogen K shell absorption edge obtained in the sample of the example. An example of the AFM image obtained in Examples 1 and 2.

The present invention is a method for measuring mechanical characteristics of a polymer composite material including a structure, and is characterized in that measurement is performed using a sample having a thickness determined based on the size of the structure in the polymer composite material. This is a method for measuring mechanical properties.

For example, when measuring a polymer composite material containing a structure such as a filler or a crosslinked material using an atomic force microscope, a smooth surface cut by a microtome or the like is observed. The sample) will be pushed in. Therefore, as shown in FIG. 1A, when the structure in the polymer composite material is smaller than the sample thickness, even if the non-deformable structure is pushed in, the height is softer than the structure existing on the back side thereof. Since the molecular material is deformed, it is not possible to accurately measure mechanical properties such as the hardness of the structure.

On the other hand, in the present invention, for example, a sample having a thickness determined based on the size of the structure in the polymer composite material, such as a method of making the sample thickness comparable to the size of the structure, is used for measuring the mechanical characteristics. Then, as shown in FIG. 1 (b), it is possible to measure in a state where there is no polymer material softer than the structure on the inner side of the structure pushed by the cantilever. Therefore, it is possible to accurately and accurately measure various mechanical properties such as hardness of the structure existing in the polymer composite material.

The polymer composite material used in the method of the present invention is a composite material containing a structure.
The structure is a cluster of about 1 nm to 100 μm formed by aggregating the filler, vulcanized material, etc. contained in the polymer composite material. There is no problem if the size of the structure can be determined by various methods such as a transmission electron microscope (TEM), a scanning electron microscope (SEM), and a scanning transmission X-ray microscope (STXM). Not only a material that does not dissolve, but also a material that dissolves in a polymer such as zinc oxide, a sulfide accelerator, and sulfur may be used.

Specific examples of the structure include a filler and a cross-linking material.
As the filler, carbon black, silica; mM ₂ · xSiO _{y · zH 2} O (in the formula, M ₂ is at least one metal selected from the group consisting of aluminum, calcium, magnesium, titanium and zirconium, or the same. Indicates a metal oxide, hydroxide, hydrate or carbonate, where m is 1 to 5, x is 0 to 10, y is 2 to 5, and z is a value in the range of 0 to 10.), And so on.

Specific examples of fillers represented by _{mM 2 · xSiO y · zH 2} O is aluminum hydroxide (Al _(OH) 3), alumina _{(Al 2 O 3, Al 2} O 3 · 3H 2 O ( water hydrate)), clay _{(Al 2 O 3 · 2SiO 2} ), kaolin _{(Al 2 O 3 · 2SiO 2} · 2H 2 O), pyrophyllite _{(Al 2 O 3 · 4SiO 2} · H 2 O), bentonite ( _{Al 2 O 3 · 4SiO 2 ·} 2H 2 O), aluminum silicate _{(Al 2 SiO 5, Al 4} (SiO 2) 3 · 5H 2 O , etc.), aluminum silicate calcium _{(Al 2 O 3 · CaO ·} 2SiO 2 ), Calcium hydroxide (Ca (OH) ₂ ), Calcium oxide (CaO), Calcium silicate (Ca ₂ SiO ₄ ), Calcium silicate (CaMgSiO ₄ ), Magnesium oxide (Mg (OH) ₂ ), Oxidation magnesium (MgO), talc _{(MgO · 4SiO 2 · H 2} O), attapulgite _{(5MgO · 8SiO 2 · 9H 2} O), magnesium aluminum oxide _{(MgO · Al 2 O 3)} , titanium white _(TiO 2), titanium black (Ti _n O _2n-1 ) and the like. In the polymer material containing such a filler, clusters in which the filler is aggregated are formed. The blending amount of the filler is preferably 10 to 200 parts by mass with respect to 100 parts by mass of the polymer component in the polymer material.

The cross-linking material is a material involved in cross-linking of the rubber composition, and examples thereof include various vulcanizing agents (cross-linking agents), vulcanization accelerators, zinc oxide, and the like.

As the vulcanizing agent, those commonly used in the tire industry can be used. Sulfur vulcanizing agent (vulcanizing agent consisting of sulfur such as powdered sulfur); 1,6-hexamethylene-sodium dithiosulfate / dihydrate, Sulfur-containing vulcanizing agents such as 1,6-bis (N, N'-dibenzylthiocarbamoyldithio) hexane: and the like.

Examples of the vulcanization accelerator include various vulcanization accelerators known in the tire industry, such as guanidines, sulfenamides, thiazoles, thiurams, dithiocarbamates, thioureas, and xanthogenates. The blending amount of each crosslinked material is preferably 0.1 to 15 parts by mass with respect to 100 parts by mass of the polymer component in the polymer material.

The polymer material constituting the polymer composite material is not particularly limited, and conventionally known ones can be mentioned. For example, a rubber material obtained by using one or more kinds of conjugated diene compounds, and a composite material in which the rubber material and one or more kinds of resins are composited can be applied. The conjugated diene compound is not particularly limited, and examples thereof include known compounds such as isoprene and butadiene.

As rubber materials, natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), halogenated Examples thereof include polymers having a double bond such as butyl rubber (X-IIR) and styrene isoprene butadiene rubber (SIBR). Further, the polymer material such as the rubber material and the composite material may contain one or more modifying groups such as a hydroxyl group and an amino group.

The resin is not particularly limited, and examples thereof include those widely used in the rubber industry, and examples thereof include petroleum resins such as C5-based aliphatic petroleum resins and cyclopentadiene-based petroleum resins.

The polymer composite material may contain other compounding agents (silane coupling agents, stearic acid, various antiaging agents, oils, waxes, etc.) widely used in the rubber industry, such as tire materials. The polymer composite material can be produced by using a known kneading method or the like.

Hereinafter, an example of the method for measuring mechanical physical characteristics of the present invention will be specifically described.
For example, first, the size of the structure in the polymer composite material is measured by measuring the amount of X-ray absorption, and then the thickness of the sample is determined based on the obtained size, and the prepared sample (polymer composite material). ), Such as a method of measuring various mechanical properties using various devices.

Examples of the method for measuring the amount of X-ray absorption include micro XAFS (X-ray Absorption Fine Structure), which is a method for measuring the X-ray absorption spectrum in a minute region of a sample using high-intensity X-rays. Since ordinary XAFS does not have spatial resolution, it detects the absorption amount of the entire sample, whereas micro XAFS is a measurement method for measuring the X-ray absorption spectrum in a minute region of a sample, and is usually about 100 nm or less. Has a spatial resolution of. Therefore, by adopting Micro XAFS, the absorption of each cross-linking material, filler, etc. contained in the sample is detected, and the absorption amount of each material such as sulfur vulcanizer, vulcanization accelerator, filler, etc. The difference can be detected.

From the viewpoint of excellent spatial resolution, the method of measuring in the soft X-ray region (micro NEXAFS) is preferable for the micro XAFS, and the scanning transmission X-ray microscope (STXM) method or the X-ray photoemission electron microscope (XPEEM) is preferable. : X-ray Photoemission electron microscope) method, and the like can be mentioned.

Since the sulfur vulcanizer and vulcanization accelerator in the polymer are easily damaged by X-rays, it is desirable to measure by a method that does not easily cause X-ray damage. From this point, the STXM method, which is less likely to cause X-ray damage, is preferable. is there. Further, it is more preferable to prevent X-ray damage by cooling the sample at the time of measurement.

The STXM method measures the amount of X-ray absorption in a minute region by irradiating a minute region of the sample with high-intensity X-rays focused by a Fresnel zone plate and measuring the light that has passed through the sample (transmitted light) and the incident light. it can. Instead of the Fresnel zone plate, a Kirkpatrick-Baez (KB) condensing system using an X-ray reflecting mirror may be used to condense high-intensity X-rays.

A continuous X-ray generator is required for the light source to scan with X-ray energy, and it is necessary to measure X-ray absorption spectra with high S / N ratio and S / B ratio in order to analyze detailed chemical states. .. Therefore, X-rays emitted from the synchrotron, since at least ^{10 10 (photons / s / mrad} 2 / mm 2 /0.1%bw) has more brightness, a and continuous X-ray source, the measurement Is optimal. Note that bw indicates the band width of X-rays emitted from the synchrotron.

High-intensity X-ray intensity ^{(photons / s / mrad 2 /} mm 2 /0.1%bw) is preferably ^{10 10} or more, more preferably ^{10 11} or more, more preferably ^{10 12} or more. The upper limit is not particularly limited, but it is preferable to use an X-ray intensity of a degree or less that does not cause radiation damage.

Further, the photon number of the high intensity X-ray (photons / s) is preferably 10 ⁷ or more, more preferably 10 ⁹ or more. The upper limit is not particularly limited, but it is preferable to use an X-ray intensity of not more than a degree that does not cause radiation damage.

The energy range scanned using high-intensity X-rays is preferably 4000 eV or less, more preferably 1500 eV or less, and even more preferably 1000 eV or less. If it exceeds 4000 eV, the target polymer composite material may not be analyzed. The lower limit is not particularly limited.

Using the above micro XAFS method, the X-ray absorption spectrum of the polymer composite material including the structure such as filler and cross-linking material is measured, and then the mapping image (image by two-dimensional mapping of the obtained X-ray absorption spectrum). ), The standard spectrum of each material, etc., it is possible to identify the chemical state of each structure contained in the sample and observe its size and dispersion state.

The size of the structure in the present invention is an average value of the sizes of the structures observed by STXM or the like. That is, it is an average value of the sizes of each structure existing in the sample (polymer composite material) used for STXM or the like. If the shape of the structure is spherical, the diameter of the sphere is the size of the structure, if it is needle-shaped or rod-shaped, the minor diameter is the size of the structure, and if it is indefinite, the average from the center. The particle size is the size of the structure.

Then, based on the measured size of the structure (filler, cross-linking material, etc.) in the sample, a method of making the sample thickness comparable to the size of the structure as shown in FIG. 1 (b). The thickness of the sample is determined based on the size of the structure.

The thickness of the sample may be appropriately set within a range in which the mechanical properties of the structure can be measured with high accuracy, but (structure size) × 0.5 ≦ sample thickness ≦ (structure size) × 2.0. It is preferable to adjust to a range, and it is more preferable to adjust to a range of (structure size) × 0.7 ≦ sample thickness ≦ (structure size) × 1.7.

For the preparation of the sample, a method capable of preparing a sample of the above size may be appropriately selected. For example, it can be produced by cutting out small pieces with a knife, scissors, a razor or the like, and cutting the cut out small pieces with a cryomicrotome or the like to form a smooth surface.

Subsequently, the mechanical characteristics of the sample adjusted to a predetermined thickness and having a smooth surface formed are measured. The method for measuring the mechanical characteristics is not particularly limited, but a method for measuring the mechanical characteristics by contacting with the sample surface is desirable, and examples thereof include not only an atomic force microscope but also a scanning force microscope and a nanoindenter. .. By making the sample surfaces in contact with each other in this way, measurement can be performed on a nano to micro scale.

Atomic force microscope (AFM) is equipped with a cantilever with a probe attached to the tip, and when the sample is observed by AFM, the probe scans the surface of the sample. The probe moves along the surface of the sample. The movement of the probe is detected by the cantilever. An AFM image is obtained by imaging the movement of the probe detected by the cantilever. The AFM detects the three-dimensional shape of the surface of the sample. With AFM, mechanical properties such as hardness and frictional force on the surface of the sample can be further measured.

Examples of AFMs that can be used include Bruker AXS MultiMode 8 and Hitachi High-Tech Science E-sweep, but the AFM is not limited to these models. The AFM measurement conditions are appropriately selected according to the type and surface condition of the sample. For example, a probe made of tungsten, iridium, silicon nitride or the like can be used. 3 (a) and 3 (b). (C) is an example of an AFM image (Examples described later, Comparative Examples 1 and 2).

In the present invention, the mechanical properties can be measured in any mode of AFM, and an appropriate measurement mode may be appropriately selected and observed. The appropriate measurement mode is selected depending on the type of polymer and the surface condition of the sample to be subjected to AFM observation. For example, a force modulation mode in which the hardness of the surface (microregion) of the sample is measured, a force volume mode in which the distribution of elastic modulus and Young's modulus on the surface of the sample can be measured, and a force curve measurement can be mentioned. In addition, a contact mode, a tapping mode, and a non-contact mode can also be mentioned.

In the method of the present invention, for example, the hardness of the structure in the polymer composite material is a mechanical property that can be measured by AFM. Young's modulus can be calculated by fitting the force curve obtained by the force volume measurement with a mechanical model such as Hertz, DMT, or JKR.

As described above, according to the method of the present invention, it is possible to measure mechanical properties such as hardness of a structure such as a filler and a crosslinked material contained in a polymer composite material (sample).

The present invention will be specifically described with reference to Examples, but the present invention is not limited thereto.

(Sample preparation method)
According to the following formulation, fill the 1.7L Banbury mixer manufactured by Kobe Steel, Ltd. with materials other than sulfur and vulcanization accelerator so that the filling rate is 58%, and reach 140 ° C at 80 rpm. Kneaded (step 1). A rubber sample was obtained by adding sulfur and a vulcanization accelerator to the kneaded product obtained in step 1 with the following composition and vulcanizing at 160 ° C. for 20 minutes (step 2).

(Mixing)
50 parts by mass of natural rubber, 50 parts by mass of butadiene rubber, 3 parts by mass of zinc oxide, 2 parts by mass of stearic acid, 1.2 parts by mass of powdered sulfur, 1 part by mass of vulcanization accelerator CZ, 0.5 parts by mass of vulcanization accelerator DPG.

The materials used are as follows.
Natural rubber: TSR20
Butadiene rubber: BR150B manufactured by Ube Industries, Ltd.
Zinc oxide: Ginmine R manufactured by Toho Zinc Co., Ltd.
Stearic acid: Tsubaki powdered sulfur manufactured by NOF Corporation (containing 5% oil): 5% oil-treated powdered sulfur manufactured by Tsurumi Chemical Industry Co., Ltd. (soluble sulfur containing 5% by mass of oil)
Vulcanization accelerator CZ: Noxeller CZ (N-cyclohexyl-2-benzothiazil sulfenamide) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
Vulcanization accelerator DPG: Noxeller D (1,3-diphenylguanidine) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.

[Comparative Examples 1 and 2]
Small pieces were cut out from the vulcanized rubber sheet using a razor or the like. The cut small pieces were further cut using a cryomicrotome to prepare a smooth surface, which was mounted on a mica plate.
(Comparative Example 1) Sample thickness: 2 mm
(Comparative Example 2) Sample thickness: 500 nm

〔Example〕
Similar to the comparative example, a small piece cut out from the vulcanized rubber sheet was further cut using a cryomicrotome to prepare a smooth surface, and mounted on a mica plate.
Sample thickness: 1 μm from the size of the vulcanization accelerator measured using the STXM method (Fig. 2: An example of a mapping image of the nitrogen K shell absorption edge obtained by performing two-dimensional mapping of NEXAFS).

<AFM measurement>
The smooth surface of the sample prepared in Examples and Comparative Examples was measured in force volume mode to obtain a distribution image (elastic modulus image) of elastic modulus (FIG. 3 (a): Example, FIG. 3 (b): Comparative Example. 1. FIG. 3 (c): Comparative example 2).
Equipment: Bruker AXS MultiMode8
Measurement range: 10 μm x 10 μm
Cantilever: 0.5N / m
Frequency: 5Hz

In the elastic modulus images of Examples 1 and 2 of FIG. 3, the sea-island structure is observed, but it can be seen that the number of islands is considerably different. In the elastic modulus image of the example of FIG. 3A, the island portion has a size of 1 to 2 μm, and the dispersed state is close to the dispersed state of the vulcanization accelerator observed by the STXM method. The island part is as hard as 20 MPa or more, and the sea part is as soft as 2 to 3 MPa. From this, it is considered that the island part is mainly a vulcanization accelerator and the sea part is mainly a polymer. From the above results, it is considered that the elastic modulus mapping measurement was performed accurately.

On the other hand, in Comparative Example 1, it can be seen that the number of islands is small. This is because the sample thickness is considerably larger than the structure size, so it is considered that the structure is pushed into the polymer and the hardness cannot be measured accurately. In addition, Comparative Example 2 also has a small number of islands. It is considered that this is because the thickness of the sample was reduced, so that the structure was also thinned, and the elastic modulus could not be measured correctly, or the structure fell off when cut with a microtome.

Further, in the case of carrying out according to the size of sulfur and zinc oxide instead of the vulcanization accelerator, and the case of carrying out according to the size of the filler of the sample to which silica and carbon black are added, the same as in the examples. The elastic modulus mapping measurement could be performed accurately.

Claims (5)

A method for measuring mechanical properties of polymer composite materials including structures.
Measured using a sample with a thickness determined based on the size of the structure in the polymer composite .
The sample is adjusted to have a thickness similar to the size of the structure in the polymer composite material, and is characterized by containing at least one selected from the group consisting of a filler and a cross-linking material. Measuring method. The method for measuring mechanical characteristics according to claim 1, wherein the structure is at least one of a filler and a cross-linking material. The method for measuring mechanical characteristics according to claim 1 or 2, wherein the size of the structure is measured using a transmission electron microscope, a scanning electron microscope, or a scanning transmission X-ray microscope. The method for measuring mechanical characteristics according to any one of claims 1 to 3, wherein the thickness of the sample is adjusted within the range of the following formula.
(Structure size) x 0.5 ≤ Sample thickness ≤ (Structure size) x 2.0 The method for measuring mechanical characteristics according to any one of claims 1 to 4, wherein the mechanical properties of the nano- to micro-scale polymer composite material are measured by contacting with the sample surface.

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