JP2960588B2 - Observation method of silica dispersion in silicone rubber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a method for observing the dispersion state of silica compounded in silicone rubber with an electron microscope.

[0002]

2. Description of the Related Art Conventionally, a transmission electron microscope has been used as a method for observing a dispersion state of silica or the like mixed in a rubber-like material. In the case of rubber having a double bond such as natural rubber, a rubber-like material sample to be provided to such a transmission electron microscope is hardened into an ebonite shape by vulcanization treatment, and then is subjected to a microtome blade such as diamond. It is prepared as a thin film having a thickness of about 0.1 μm by sectioning. In the case of silicone rubber, it does not harden so much even when it is vulcanized, so that it is frozen with liquid nitrogen, and then a thin film is similarly made with a microtome blade.

[0003]

However, when silicone rubber is used as a sample in a transmission electron microscope as described above, sufficient hardness can be obtained even if the silicone rubber is frozen using liquid nitrogen. Therefore, there is a problem that it is difficult to produce a thin film having a desired thickness using a microtome blade. In addition, since observation with a low magnification is difficult with a transmission electron microscope, there is a problem that the dispersion state of silica in rubber cannot be observed over a wide range.

[0004]

Means for Solving the Problems In view of the above-mentioned problems, the present inventors have made intensive studies especially on the development of a simple method for observing the dispersion state of silica in silicone rubber. As a result, they have found a good method for observing with a scanning electron microscope, and have provided the present invention.

That is, according to the present invention, a silicone rubber molded article containing silica is frozen and cured, and then cut to prepare a sample, and the sample is cut at a low acceleration voltage of 10 kV or less. And a method for observing silica dispersion in silicone rubber, characterized by observing with a scanning electron microscope set in (1). The present invention also provides a silicone rubber molded article containing silica, filled in a gelatin capsule together with water, frozen and cured, and then cut to prepare a sample. Then, the cut surface of the sample is reduced to 10 kV or less. The present invention also provides a method for observing silica dispersion in silicone rubber, characterized by observing with a scanning electron microscope set at a low acceleration voltage.

The silicone rubber containing silica in the present invention is a silicone rubber to which silica is added as a usual reinforcing filler. Examples of the silica include a dry method of silicic acid (fumed silica) produced by burning and pyrolyzing silicon tetrachloride and the like, and a wet method of reacting sodium silicate with a mineral acid in an aqueous solution. Hydrous silicate (white carbon) is used. When silica is highly dispersed in such a silicone rubber, an excellent reinforcing effect is exhibited. Therefore, it is necessary to observe the dispersion state of the silica.

[0007] In the present invention, a silicone rubber compounded with silica is preliminarily formed into a shape that is easily cleaved, frozen and cured, and then cleaved to obtain a cleaved surface suitable for a scanning electron microscope. It is extremely important to produce a sample having That is, a silicone rubber compounded with a predetermined silica can be generally cut by hand into a shape such as a rod having a diameter of 1 to 2 mm × a length of 20 to 50 mm (FIG. 1) or a thickness of 1 to 3 mm × a width of 2 mm. ~ 4mm x length 20 ~ 5
After a 0 mm plate (FIG. 2) is formed in advance, it is frozen and hardened with liquid nitrogen. Next, the molded body frozen in liquid nitrogen is cleaved with tweezers or the like, or the molded body is taken out of liquid nitrogen and broken by hand before thawing. 1 (A), (B), (C) and FIG.
-As shown in (A) and (B), by providing the cut portion 1 on the outer periphery of the molded body in advance, not only the cutting is facilitated but also the thickness (diameter) is increased in advance to obtain a wide split section. It is preferred because it can be. Further, in order to obtain a sample having a smooth fractured surface, the following method is particularly recommended in the present invention. That is, a silicone rubber molded body as shown in FIGS. 1 and 2 is filled in a gelatin capsule, filled with water, and frozen by liquid nitrogen and cured. It is not appropriate to use alcohol instead of water, since the melting point is low and the dissolution when taken out from liquid nitrogen is fast. Next, the capsule is taken out of the liquid nitrogen and cut with a hard object such as a hammer. When cutting, the cutting may be performed by sandwiching between pliers. The cleaved molded body may be adjusted to an appropriate shape having a cleaved section that can be used as a sample for a scanning electron microscope.

In the present invention, it is very important to set the accelerating voltage to 10 kV or less, especially 4 to 6 kV, in order to provide the prepared sample to a scanning electron microscope to obtain good observation results. It is. That is, when a sample of the silicone rubber compounded with the silica of the present invention is subjected to a scanning electron microscope and an acceleration voltage higher than 10 kV is set, an electron beam enters the inside of the sample and information on a fractured surface is obtained. As a result, the dispersion state of silica existing in the fractured surface is not accurately observed. In the scanning electron microscope of the present invention, if the acceleration voltage is set too low, it is not appropriate because the resolution at the fractured surface of the sample decreases.

[0009]

According to the present invention, a sample having a fractured surface which can be observed with a scanning electron microscope by using means of molding, freezing, and fracture of a silicone rubber containing silica is provided. It is very easy. Further, the present invention employs a scanning electron microscope, which enables observation at a low magnification, which was difficult with a transmission electron microscope, and as a result, has an advantage that the dispersion state of silica in silicone rubber can be observed over a wide range. Having. Therefore, according to the present invention, as a result of accurately observing the aggregation state of silica dispersed in the silicone rubber, it is possible to judge the performance of the obtained silicone rubber, for example, the quality of physical properties such as plasticization return.

[0010]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples.

[0011]

Example 1 To 150 g of silicone rubber, 60 g of silica (hydrous silicic acid) manufactured by Tokuyama Soda Co., Ltd. manufactured by a wet method was blended and kneaded at 25 ° C. with a 4-inch roll. Further, the primary vulcanization is carried out using
Secondary vulcanization was carried out at 200 ° C. for 4 hours at 10 ° C.

The obtained silicone rubber was molded into a rod having a size of 2 × 2 × 30 mm as shown in FIG. 1-C, and a molded article having cuts on all sides was prepared. Next, the molded body was frozen in liquid nitrogen until it became hard enough to be broken, and then taken out and cut by hand. Further, a molded body having a shape of a rod of 2 × 2 × 30 mm as shown in FIG. 1-A and having a cut in one side was produced. Next, the capsule was filled with water in a gelatin capsule (manufactured by Lilly), frozen in liquid nitrogen until it became hard enough to be broken, then taken out and cut on a table with a hammer.

[0013] Each of these molded bodies having a fractured surface is cut out to a thickness of about 1 mm, and fixed on a sample stage of a scanning electron microscope using a carbon double-sided tape. A sample was obtained by coating to a thickness of 15 nm.

Scanning electron microscope (manufactured by JEOL Ltd., JS
M-5400) set the acceleration voltage to 5.0 kV and observed the sample at a magnification of 350 times. As a result, as shown in FIG. 3, dispersion (aggregation) of silica in the silicone rubber
The condition could be observed extensively and clearly. In addition, the sample cut using the gelatin capsule had a wider observable flat surface as shown in FIG. 4 (350 times) and FIG. 5 (1000 times).

[Brief description of the drawings]

FIG. 1 shows the form of a rod (A, B, C) according to a representative example of a molded article in the present invention.

FIG. 2 shows a form of a plate-like body (A, B) which is a typical example of a molded body in the present invention.

FIG. 3 is an electron micrograph (× 350) instead of a drawing showing the result of observing a silicone rubber sample obtained by cutting without using a gelatin capsule in Example 1.

FIG. 4 is an electron micrograph (× 350) instead of a drawing showing the result of observing a silicone rubber sample obtained by cutting using a gelatin capsule in Example 1.

FIG. 5 is an electron micrograph (× 1000) instead of a drawing showing the result of observation of a silicone rubber sample obtained by cutting using a gelatin capsule in Example 1.

[Explanation of symbols]

 1 Notch of molded body

Continuation of front page (58) Fields surveyed (Int.Cl. ⁶ , DB name) G01N 1/28 G01N 23/22

Claims (2)

(57) [Claims] Claims: 1. A silicone rubber molded product containing silica is frozen and cured, and then cut to form a sample.
A method for observing dispersion of silica in silicone rubber, wherein a cross section of the sample is observed with a scanning electron microscope set at a low acceleration voltage of 10 kV or less. 2. A silicone rubber molded article containing silica is filled into a gelatin capsule together with water, frozen and cured, and then cut to prepare a sample.
A method for observing dispersion of silica in silicone rubber by a scanning electron microscope equivalent to that described above.