Method for observing surface of resin molding

Abstract

To easily observe a surface condition of a resin molding.SOLUTION: In a method for observing a surface of a resin molding, a halogenated solution containing a halogen element is coated on the surface of the resin molding, so that a halide ion contained in the applied halogenated solution impregnates according to a surface condition of the resin molding, in order to evaluate a surface condition of the resin molding on the basis of observation results of a coloring density distribution due to colored trihalide ions, pentahalide ions and / or the halogen element, and a luminescence distribution in an X-ray image according to the halogen element which can serve as a contrast medium.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] This invention relates to a method for observing the surface of a resin molded body. More specifically, it analyzes the surface state of the resin molded body and the cause of fracture on the fracture surface, and relates to a method for observing the surface of a resin molded body.

Background Art

[0002] Conventionally, when a resin part composed of a resin molded body is damaged, fracture surface observation has been performed to investigate the cause. Fracture surface observation is a method widely used mainly in the metal field to estimate the fracture mechanism or the cause of fracture from the characteristics of the fracture surface pattern. However, since various fracture surface patterns are shown depending on the fracture mechanism in resin materials as well as in metal materials, similar analysis methods have been adopted. Generally, confirmation of the starting point of fracture on the fracture surface of a resin molded body is performed using a stereomicroscope or a scanning electron microscope (SEM).

[0003] On the other hand, a method for observing the fracture surface of a resin molded body has been disclosed, which uses a contrast agent containing iodine or the like by X-ray CT to observe the penetration behavior of the contrast agent and visualize it based on information regarding density, crystallinity, orientation, etc. (see Patent Document 1). In addition, there is a penetration flaw detection method as a method for detecting the position and size of surface defects. This is a method for detecting defects such as cracks by infiltrating a liquid using capillary action, and it has been disclosed that it can also be applied to resins (see Patent Document 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] When confirming the fracture origin on the fracture surface of a resin molded product using a stereomicroscope or SEM, the amount of data to observe becomes enormous for samples with a large fracture surface area. Furthermore, molded products containing inorganic fillers such as glass fiber reinforcement are difficult to detect because the ductile fracture region that serves as the fracture origin is minute, requiring a lot of time for observation. In addition, while penetrant testing can easily identify open defects on the surface of molded products such as cracks in resin parts, identifying the fracture origin deep within cracks requires further sample cutting and observation with an SEM or stereomicroscope. Moreover, observation using X-ray CT with contrast agents containing iodine requires preparation such as sample cutting and image processing, making it not a convenient method of investigation.

[0006] This invention is proposed in view of the above-mentioned circumstances, and aims to provide a method for observing the surface condition of a resin molded article that can be easily performed without requiring much effort for observation or preparation. [Means for solving the problem]

[0007] To solve the above-mentioned problems, the surface observation method for a resin molded article according to this application includes the steps of applying a halogenated solution containing halogen elements to the surface of the resin molded article, and determining the surface state of the resin molded article based on observation results in the visible light and radiation regions regarding the distribution of halogen elements contained in the applied halogenated solution on the surface of the resin molded article.

[0008] In the process of determining the surface state of a resin molded article, the observation area of ​​the surface of the resin molded article may be determined as a ductile fracture region if the distribution of halogen elements is relatively dense, resulting in a relatively dark color in the visible light region and relatively high absorption in the radiation region, and as a brittle fracture region if the distribution of halogen elements is relatively sparse, resulting in a relatively light color in the visible light region and relatively low absorption in the radiation region.

[0009] In the step of determining the surface state of the resin molded article, the ductile fracture region may be determined as the starting point of the fracture surface, with respect to the adjacent ductile fracture region and brittle fracture region on the fracture surface of the resin molded article.

[0010] The halogenation solution may be an alkali metal halide salt solution. The alkali metal may be sodium or potassium in the halogen compound salt. The halogenation solution may also contain iodine and potassium iodide. [Effects of the Invention]

[0011] According to this invention, the surface state of a resin molded article, particularly the ductile fracture region, can be easily observed. [Brief explanation of the drawing]

[0012] [Figure 1] This is a perspective view illustrating a first embodiment in which a test specimen breaks upon three-point bending. [Figure 2] This photograph illustrates the coloring caused by dilute iodine tincture applied to the fracture surface of a test specimen. [Figure 3] This is a perspective view illustrating a second embodiment in which a test specimen breaks upon three-point bending. [Figure 4] This diagram illustrates the relationship between photographs of the fracture surface of a specimen coated with dilute iodine tincture and microscopic images of ductile and brittle fracture. [Figure 5] This figure shows a photograph of the fracture surface of a test specimen coated with dilute iodine tincture, along with a CT image. [Figure 6] This is a photograph of a potassium iodide solution. [Figure 7] This is a photograph of the fracture surface of a test specimen coated with potassium iodide. [Figure 8] This is a photograph of the fracture surface of a test specimen coated with iodotoluene. [Figure 9] This figure shows a CT image of a test specimen coated with iodinetoluene. [Modes for carrying out the invention]

[0013] Hereinafter, the method for observing the surface of the resin molded body according to the present application will be described in detail with reference to the drawings. The method for observing the surface of the resin molded body of the present embodiment assumes observing the surface of a resin molded body formed from a resin such as polyacetal (POM), but regardless of this, the resin molded body may be formed from other types of resins. In addition to scratches and sliding marks on the surface of the resin molded body to be observed, jetting and flow marks generated during molding, cracks generated by residual stress, ductile fracture regions such as crazing, and in the case of a fracture surface, the ductile fracture region near the origin of the fracture can be specified.

[0014] In the present embodiment, as the halogen element, bromine (Br2) and iodine (I2) are preferable, and iodine (I2) which is easy to handle is particularly preferable. The halogenated solution contains the above-mentioned bromine (Br2) or iodine (I2) and dissociates in the solution to contain a halide that becomes Br - , I - ions. The halogenated solution may be any solution as long as the halogen ions can be colored and used as a contrast agent for imaging by radiation, and may be an alkali metal halide solution. The alkali metal of the alkali metal salt solution may be sodium or potassium.

[0015] An example of a halogenated solution containing a halogen element that can be easily obtained is dilute iodine tincture used for medical purposes. Dilute iodine tincture is a solution containing iodine (I2) and potassium iodide (KI) as halogen elements, and is obtained by dissolving iodine and potassium iodide in an aqueous ethanol solution. In dilute iodine tincture, iodine is dissolved in the aqueous ethanol solution due to the intervention of potassium iodide, and iodine-based dyes such as I3 - and I5 - are generated, resulting in a brown color. In addition, iodine has a large atomic weight and can be used as a contrast agent for imaging by X-rays.

[0016] Furthermore, in the present embodiment, as the observation in the radiation region, X-ray observation is assumed. The X-ray observation may use not only X-ray images obtained by simple imaging with X-rays but also X-ray CT images using computed tomography (CT) technology. Note that the radiation used for observation is not limited to electromagnetic waves such as X-rays, and may be charged particles such as electron beams and ion beams, for example.

[0017] In the surface observation method of the present embodiment, in the first step, a halogenated solution containing a halogen element is applied to the surface of the resin molded body to be observed. For example, a cotton swab is impregnated with a halogenated solution containing a halogen element and applied to the entire surface of the resin molded body or the region to be observed at a specific site. The application of the halogenated solution containing a halogen element to the resin molded body is not limited to application with a cotton swab or the like, and may be by spraying the halogenated solution containing a halogen element, or the resin molded body may be impregnated with the halogenated solution containing a halogen element. In this specification, the application of the halogenated solution containing a halogen element includes modes such as spraying and impregnation of the halogenated solution containing a halogen element onto the resin molded body.

[0018] The halogenated solution containing a halogen element applied to the resin molded body is distributed according to the surface state of the application surface. When the application surface is a fracture surface, it is observed that a brittle fracture region is adjacent to a ductile fracture region in the ductile fracture region. It is known that the formation of a fracture surface due to fracture occurs when ductile fracture generated from the starting point of the fracture surface converts to brittle fracture halfway as the fracture progresses, and a brittle fracture region is formed adjacent to the ductile fracture region.

[0019] The surface area per unit area of ​​a fracture surface differs depending on the surface condition. In the ductile fracture region, the resin is stretched, causing minute elongation, fine cracks, and crazing on the fracture surface, resulting in a relatively large surface area. In the brittle fracture region, minute elongation is not observed, resulting in a relatively small surface area. Therefore, in the ductile fracture region, a large amount of halide ions penetrate into the fine cracks and crazing, leading to a relatively high distribution of halogen elements after solution drying. In the brittle fracture region, minute elongation is not observed, fewer halide ions penetrate the surface, and the distribution of halogen elements after solution drying is relatively low.

[0020] In this embodiment, the surface observation method involves observing the distribution of halogen elements on the coated surface of the resin molded body in the visible light region and the radiation region in the following steps. Here, the visible light region is the electromagnetic wave with a wavelength of approximately 360 to 700 nm, which can be observed by human vision. The radiation region is assumed to be observed using X-rays, as described above.

[0021] In the visible light region, halogen elements in a halogenation solution become trihalide ions and pentahalide ions, which penetrate the coated surface. Since the penetrated halide ions are colored, the surface becomes intensely colored. Upon drying, the trihalide ions and pentahalide ions revert to halogen elements and halogen compounds. However, because halogen elements are also colored, the density of halogen element distribution on the coated surface can be observed by visually observing the distribution of color intensity. Therefore, this method allows surface observation regardless of whether the halogenation solution is dried or not.

[0022] For example, if the coloring in a certain observation area of ​​the coated surface is relatively darker than in other areas, it can be determined that the distribution of halogen elements in this observation area is relatively dense. Conversely, if the coloring in a certain observation area is relatively lighter than in other areas, it can be determined that the distribution of halogen elements in this observation area is relatively sparse. When observing fracture surfaces, if there are multiple dark areas on the coated surface, or if the pattern is dotted, mesh-like, mottled, or gradient-like, the darkest area may be determined to be the ductile fracture region at the initial fracture point. If the resin molded body does not contain inorganic fillers, a brittle fracture region may not be observed in fracture surfaces such as creep fracture or fatigue fracture. In such cases, a particularly darkly colored area within the ductile fracture region can be determined to be the fracture point.

[0023] As mentioned above, in the ductile fracture region of the fracture surface, trihalide ions and pentahalide ions penetrate and revert to halogen elements upon drying, but in either state, the distribution of halogen elements is relatively high. In the brittle fracture region, the penetration of halide ions is low, so the distribution of halogen elements is relatively low, and the overall distribution of halogen elements is also low. Of the halogen elements contained in the halogenation solution, those that are not ionized do not penetrate into the resin molded product. Therefore, the intensity of coloring in the coated area is influenced by the amount of halide ion penetration.

[0024] In the field of radiography, halogen elements have a larger atomic weight than other elements that make up resin molded bodies, making them suitable as contrast agents. The distribution of halogen elements can be observed by the brightness distribution in the X-ray image of the coated surface. For example, if the brightness of a certain observation area on the coated surface is relatively high compared to other areas, it can be determined that the distribution of halogen elements in this observation area is relatively dense. Conversely, if the brightness of a certain observation area is relatively low compared to other areas, it can be determined that the distribution of halogen elements in this observation area is relatively sparse. Furthermore, by using X-ray CT images, not just simple X-ray images, it is possible to determine the distribution of halogen elements in the depth direction of fracture surfaces and within the resin molded body.

[0025] When observing X-ray images, if the absorption in a pixel in a certain observation area of ​​the coated surface is relatively large compared to pixels in other areas, for example, if the brightness of that pixel is relatively high, then the distribution of halogen elements in that observation area is relatively dense, and it can be determined to be a ductile fracture region. Conversely, if the coated surface is a fracture surface, and the absorption in a pixel in the observation area is relatively small compared to other areas, for example, if the brightness of that pixel is relatively low, then the distribution of halogen elements in that observation area is relatively sparse, and it can be determined to be a brittle fracture region.

[0026] When the observation area is a fracture surface, whether observed in the visible light region or the radiation region, if a brittle fracture region is observed to be adjacent to a ductile fracture region, the ductile fracture region can be determined to be the fracture initiation point. Such determination of the fracture initiation point can be performed separately in the visible light region and the radiation region. Therefore, by comparing the results determined in the visible light region and the radiation region, the accuracy of the fracture initiation point determination can be improved.

[0027] According to the surface observation method of this embodiment, when observing a coated surface in the visible light region, the distribution of the intensity of colored trihalide ions, pentahalide ions, or halogen elements distributed on the coated surface can be observed visually. Since no equipment or measurement preparation is required, the time required for observation can be shortened. Furthermore, while scanning electron microscopes (SEMs) and X-ray imaging devices have limitations on the size of the sample placed in the chamber, this method allows for visual observation of a fractured surface coated with a halogenated solution containing halogen elements, and there are no size limitations.

[0028] When organic colorants such as dyes or pigments are applied to a resin molded body instead of a halogenated solution containing halogen elements, differences between ductile and brittle fracture regions can sometimes be observed in the visible light range due to differences in dye penetration (dye penetration) and pigment penetration (pigmentation due to layering on the resin molded body surface). However, because organic colorants do not act as contrast agents, it is not possible to determine the depth direction of the fracture surface or the ductile fracture region inside the resin molded body, which cannot be confirmed visually, using X-ray images. Therefore, halogenated solutions containing halogen elements are superior in determining the ductile fracture region inside the resin molded body.

[0029] When observing metal-compound samples with an X-ray imaging device, halation may occur, but visual observation in the visible light range can also be applied to metal-compound samples. Furthermore, in cases of complex fracture surfaces, it can be difficult to distinguish between ductile and brittle fracture when a halogenated solution containing halogen elements is applied to the fracture surface and observed with X-rays. However, by visually observing the distribution of color intensity of trihalide ions, pentahalide ions, or halogen elements applied to the fracture surface, ductile and brittle fracture can be easily distinguished.

[0030] Furthermore, according to the surface observation method of this embodiment, when observing fracture surfaces with X-rays, it is possible to observe the surface condition even for samples that are difficult to distinguish visually, such as black samples. In addition, it is possible to observe fracture surfaces in the depth direction and fracture surfaces inside the sample, which are difficult to observe visually. [Examples]

[0031] An example of applying the surface observation method of this embodiment will be described. In this example, as evaluation materials, Duracon® POM·M90-44 (hereinafter sometimes referred to as M90-44 (unfilled material)) manufactured by Polyplastics was prepared as a polyacetal (POM) without fillers, and Duracon® POM·GH-25 (hereinafter sometimes referred to as GH-25 (GF reinforced material)) manufactured by Polyplastics was prepared as a polyacetal containing glass fiber reinforcement. Test specimens with dimensions of 80 mm × 10 mm × 4 mm were prepared using M90-44 (unfilled material) and GH-25 (GF reinforced material), respectively. Here, in the POM·M90-44 (unfilled material), a notch was formed along one of the short sides forming a rectangular cross-section approximately perpendicular to the longitudinal direction, approximately in the center of the longitudinal direction of the test specimen, in order to make the fracture initiation point easier to see. The notch was cut to a depth of 2 mm and at a 45° angle.

[0032] (Experimental Example 1) Figure 1 is a perspective view illustrating the first mode of fracture of a test specimen in a three-point bending test. As shown in the figure, in a roughly rectangular parallelepiped-shaped test specimen formed from M90-44 (unfilled material), the surface containing the short side with a notch formed approximately in the center in the longitudinal direction is designated as the bottom surface, and the surface opposite the bottom surface is designated as the top surface. The bottom surface is supported near both ends in the longitudinal direction by two support stands, and an indenter is pressed down on the top surface at a position opposite the notch approximately in the center in the longitudinal direction. Here, the indenter is pressed down at a normal test speed of 2 mm / min in accordance with ISO 178, and the pressing is continued until the test specimen fractures starting from the notch. Upon fracture, a fracture surface is formed on the test specimen extending along the cross-section starting from the notch, and the test specimen separates into two individual pieces. For convenience, the individual pieces of the test specimen may also be referred to as the test specimen below.

[0033] A dilute iodine tincture was applied to the fracture surface of one of the test specimens obtained by breakage. The dilute iodine tincture contained iodine I2 (3 g), potassium iodide KI (2 g), ethanol (73.4 ml), and purified water (appropriate amount). This dilute iodine tincture was impregnated into a cotton swab and applied to the fracture surface of the test specimen.

[0034] Figure 2 is a photograph illustrating the coloration caused by the application of dilute iodine tincture to the fracture surface of the test specimen. Figure 2(a) is a photograph showing the fracture surface before the application of dilute iodine tincture. On the fracture surface, the side where the notch is formed is the tension side, and the side pressed down by the indenter is the compression side. The fracture surface is formed starting from the notch on the tension side, and a whitened region is observed following the notch on the tension side. Here, it is thought that ductile fracture occurs at the starting point of fracture surface formation, and as the fracture surface formation progresses, the ductile fracture is converted to brittle fracture. Therefore, it is thought that the whitened region following the notch contains ductile fracture.

[0035] Figure 2(b) is a photograph showing the fracture surface after application of dilute iodine tincture. The fracture surface is stained brownish-red by the colored iodide ions, but there are variations in the intensity of the coloring. Some areas following the notch are relatively darker, while the other areas are relatively lighter. Therefore, as mentioned above, the areas with relatively dark coloring are determined to be ductile fracture regions where the iodine distribution is relatively dense. The other areas with relatively light coloring are determined to be brittle fracture regions where the iodine distribution is relatively sparse.

[0036] (Experimental Example 2) Figure 3 is a perspective view illustrating a second mode of fracture of a test specimen in a three-point bending test. As shown in the figure, in a roughly rectangular parallelepiped-shaped test specimen made of GH-25 (GF reinforced material), the surface containing one of the long sides of a rectangle with a cross-section roughly perpendicular to the longitudinal direction, approximately in the center of the longitudinal direction, is designated as the first side surface, and the surface opposite the first side surface is designated as the second side surface. The first side surface is supported near both ends in the longitudinal direction by two support stands, and pressure is applied with an indenter at approximately the center in the longitudinal direction of the second side surface. Here, the indenter is advanced at a normal test speed of 2 mm / min in accordance with ISO 178 until the test specimen fractures. Upon fracture, a fracture surface extending along the cross-section is formed on the test specimen, and the test specimen separates into two individual pieces. Dilute iodine tincture was applied to the fracture surface of one of the individual pieces obtained by fracture. The same dilute iodine tincture as in Experimental Example 1 was used.

[0037] Figure 4 illustrates the relationship between photographs of the fracture surface of a specimen coated with dilute iodine tincture and micrographs of ductile and brittle fracture. Figure 4(a) is a photograph showing the fracture surface coated with dilute iodine tincture. In the fracture surface, which is colored brown by the colored iodide ions, the region containing the vertex formed by the intersection of one end of the edge formed by the first side surface and the edge forming the short side of the roughly rectangular fracture surface is observed to be relatively darker in color than other regions.

[0038] Figure 4(b) is a SEM micrograph of a region where relatively dark coloration was observed. In this region, minute elongation of the resin is observed, and it is determined to be a ductile fracture region. Glass fibers added to the resin are also visible in the micrograph. Figure 4(c) is a SEM micrograph of a region where relatively light coloration was observed, unlike the region where relatively dark coloration was observed. In this region, minute elongation is not observed on the fracture surface, and it is determined to be a brittle fracture region. Glass fibers added to the resin are also visible in the micrograph.

[0039] Microscopic examination of Figures 4(b) and 4(c) confirmed that the areas with relatively darker coloration were ductile fracture regions, while the other areas with relatively lighter coloration were brittle fracture regions. Therefore, it was confirmed that ductile fracture originated from the first side surface on the tensile side, which was supported by the support structure, and that the ductile fracture converted to brittle fracture, with the formation of the fracture surface due to brittle fracture progressing to the second side surface on the compression side.

[0040] (Experimental Example 3) Similar to Experimental Example 1, a test specimen formed with M90-44 (unfilled material) was fractured according to a three-point test in the first configuration shown in Figure 1. The indenter was pressed at a normal test speed of 2 mm / min in accordance with ISO 178, and dilute iodine tincture was applied to the fracture surface of one of the individual pieces obtained by fracture. The same dilute iodine tincture as in Experimental Example 1 was used.

[0041] Figure 5 shows a photograph and CT image of the fracture surface of one of the specimens fractured in Experiment 3, to which dilute iodine tincture was applied. Figure 5(a) is a photograph showing the fracture surface to which dilute iodine tincture was applied. As mentioned above, in the fracture surface, the area with relatively darker coloration following the tensile notch is determined to be a ductile fracture region. Conversely, the area with relatively lighter coloration is determined to be a brittle fracture region.

[0042] Figure 5(b) shows cross-sectional images from three directions obtained by X-ray CT, and Figure 5(c) shows a volume rendering image constructed from the X-ray CT images. In the cross-sectional image in Figure 5(b) and the volume rendering image in Figure 5(c), a region of high brightness is observed only on the outermost surface of the fracture. The regions of high brightness in the X-ray CT images in Figures 5(a) and 5(b) almost coincide with the regions where the coloring by dilute iodine tincture is concentrated when observed in visible light, as in Figure 5(a). Therefore, the regions of high brightness are thought to be ductile fracture regions, where iodine, which has high absorption, is densely distributed.

[0043] (Comparative Example 1) Figure 6 shows photographs of potassium iodide solutions. The left side of the figure shows a potassium iodide solution with water as the solvent, and the right side shows a potassium iodide solution with ethanol as the solvent. Both are colorless and transparent solutions.

[0044] Figure 7 shows photographs of the fracture surfaces of test specimens coated with potassium iodide solution. Figure 7(a) shows the fracture surface of M90-44 (unfilled material) coated with potassium iodide solution, and Figure 7(b) shows the fracture surface of GH-25 (GF-reinforced material) coated with potassium iodide solution. The test specimens with fracture surfaces of M90-44 (unfilled material) and GH-25 (GF-reinforced material) were prepared in the same manner as in Experimental Example 1 and Experimental Example 2, respectively. A potassium iodide solution with ethanol as the solvent was used. As shown in Figure 6, the potassium iodide solution is colorless. No discoloration was observed on the fracture surfaces in either Figure 7(a) or Figure 7(b). Therefore, surface observation by visually observing the distribution of color intensity on the fracture surface in the visible light region was not possible.

[0045] (Comparative Example 2) Figure 8 is a photograph of the fracture surface of a specimen coated with iodotoluene. Figure 8(a) shows the fracture surface of a specimen coated with iodotoluene. This specimen was formed using M90-44 (unfilled material) as in Experimental Example 3, and fractured by pressing it at the normal test speed of 2 mm / min. Iodotoluene is colorless, and no discoloration was observed on the fracture surface coated with iodotoluene. Therefore, it was not possible to observe the surface by visually checking the distribution of color intensity on the fracture surface in the visible light region.

[0046] Figure 8(b) shows the fracture surface of a specimen coated with dilute iodine tincture for comparison. The specimen in Figure 8(b) was prepared in the same manner as in Figure 8(a), and the same dilute iodine tincture as in Experimental Example 1 was used. A brownish-red coloration is observed on the fracture surface coated with dilute iodine tincture, and the distribution of color intensity can be visually observed in the visible light region. In the figure, a ductile fracture region with darker coloration is observed in the area following the notch on the tensile side.

[0047] Figure 9 shows a CT image of a specimen coated with iodotoluene. Figure 9(a) is a reproduction of the photograph of the iodotoluene-coated specimen shown in Figure 8(a). Here, the photograph in Figure 8(a) has been rotated so that the longitudinal direction of the fracture surface extends in the direction of the transverse of the paper, allowing for comparison with the CT image in Figure 9.

[0048] Figure 9(b) shows X-ray CT images acquired from three directions. If Figure 9(a) is a top view of the fracture surface, then the CT images corresponding to the top view are shown in the upper left of Figure 9(b), the front view in the lower left, and the right side view in the lower right. Figure 9(c) is a volume rendering image constructed from the CT images. In the X-ray CT images of Figures 9(b) and 9(c), high brightness can be observed in the areas where fine cracks and crazes were observed on the fracture surface in the photograph in Figure 9(a). [Industrial applicability]

[0049] This invention can be used to observe the surface condition of resin parts made from molded resin.

Claims

1. A method for observing the surface of a resin molded body, comprising: a step of applying a halogenated solution containing a halogen element to a surface of a resin molded body; a step of determining the surface condition of the resin molded body based on the results of observation of the distribution of halogen elements contained in the applied halogenated solution on the surface of the resin molded body in the visible light and radiation regions; A method comprising:

2. The method of claim 1, wherein the process of determining the surface condition of the resin molding comprises determining, for the observation area on the surface of the resin molding, an observation area in which the distribution of halogen elements is relatively dense, such that the distribution is relatively dark in the visible light region and the absorption is relatively large in the radiation region, as a ductile fracture area, and determining, for the observation area in which the distribution of halogen elements is relatively sparse, such that the distribution is relatively light in the visible light region and the absorption is relatively small in the radiation region, as a brittle fracture area.

3. The method according to claim 2, wherein the step of determining the surface condition of the resin molding comprises determining that the ductile fracture region and the brittle fracture region adjacent to each other on the fracture surface of the resin molding are the origin of the fracture surface.

4. 4. The method according to claim 1, wherein the halogenation solution is an alkali metal halide salt solution.

5. 5. The method of claim 4, wherein the alkali metal is a halide salt of sodium or potassium.

6. 6. The method of claim 5, wherein the halogenation solution comprises iodine and potassium iodide.

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