Method for estimating mechanical properties of resin

Abstract

To provide a method for estimating the mechanical properties of a resin, which can nondestructively, stably and accurately inspect the mechanical properties of the resin.SOLUTION: Disclosed is a method for estimating the mechanical properties of a resin, which comprises: a correlation calculation step of irradiating a sample made of the same type of material as an object to be inspected with ultraviolet light, measuring a first physical property value and a first mechanical property value of the sample irradiated with ultraviolet light, and calculating a correlation between the first physical property value and the first mechanical property value; a measurement step of measuring a second physical property value of the object to be inspected; and an estimation step of estimating a second mechanical property value of the object to be inspected based on the second physical property value and the correlation, wherein the object to be inspected is a resin, and the first and second physical property values are values representing an external shape.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for predicting mechanical properties of a resin. [Background technology]

[0002] Conventionally, a method for testing the mechanical properties of resins by tensile testing has been known (see, for example, Patent Document 1). In Patent Document 1, the mechanical properties of PVC (polyvinyl chloride), silicone rubber, etc. are tested by a tensile test specified in JIS K6251 (1994). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2022-189649 Summary of the Invention [Problem to be solved by the invention]

[0004] Since testing mechanical properties using tensile tests is a destructive test (resulting in plastic deformation), it is impossible to confirm the reproducibility of the test. Furthermore, when conducting tensile tests on soft resins, it is difficult to fix the sample with the same force for each test, making it difficult to test mechanical properties stably and accurately.

[0005] An object of the present invention is to provide a method for estimating the mechanical properties of a resin, which is capable of non-destructively, stably and accurately testing the mechanical properties of a resin. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, the present invention provides a method for estimating the mechanical properties of a resin, comprising: a correlation calculation step of irradiating ultraviolet light onto a sample made of the same material as an object to be inspected, measuring a first physical property value and a first mechanical property value of the ultraviolet-irradiated sample, and calculating the correlation between the first physical property value and the value of the first mechanical property; a measurement step of measuring a second physical property value of the object to be inspected; and an estimation step of estimating the value of the second mechanical property of the object to be inspected based on the second physical property value and the correlation, wherein the object to be inspected is a resin, and the first and second physical property values ​​are values ​​representing the external shape. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a method for estimating the mechanical properties of a resin, which is capable of non-destructively, stably and accurately testing the mechanical properties of a resin. [Brief explanation of the drawings]

[0008] [Figure 1] 1(a), (b), and (c) are graphs showing the relationship between the average curvature of samples S1 to S3 and TS, the relationship between the average curvature of samples S1 to S3 and TE, and the relationship between the average curvature of samples S1 to S3 and 100%M, respectively. [Figure 2] 2(a) and (b) are graphs showing the relationship between UV-C irradiation energy and the average curvature of samples S1 to S3, and the relationship between UV-C irradiation energy and the average residual stress of samples S1 to S3, respectively. [Figure 3] Fig. 3(a) is a graph showing the curvatures and their average values ​​of samples S1 to S3 after UV-C irradiation, and Fig. 3(b) is a graph showing the residual stresses and their average values ​​of samples S1 to S3 after UV-C irradiation. [Figure 4] 4(a) and (b) are image data showing the surface shape of the sample S1 measured by a confocal laser microscope. [Figure 5] Figures 5(a) and (b) are images showing the process of measuring the radius of curvature of sample S1 irradiated with UV-C at an irradiation energy of 1500 J / cm2. [Figure 6]Figures 6(a) and (b) are images showing the process of measuring the radius of curvature of sample S1 irradiated with UV-C at an irradiation energy of 750 J / cm2. DETAILED DESCRIPTION OF THE INVENTION

[0009] (Method for predicting the mechanical properties of resin) According to the method for estimating the mechanical properties of a resin in accordance with an embodiment of the present invention, the mechanical properties of an object to be inspected are estimated using physical property values ​​that represent the external shape of the object to be inspected, which are measured non-destructively using a confocal laser microscope or the like.

[0010] The object to be inspected in the method for estimating the mechanical properties of a resin according to an embodiment of the present invention is a resin (plastic or rubber), such as a resin containing a plasticizer. Plasticizers are added to resins to improve their flexibility, but when the resin is exposed to ultraviolet light, the plasticizer is released from the surface exposed to the ultraviolet light. Numerous fine depressions (traces of plasticizer release) appear on the surface from which the plasticizer has been released, and planar shrinkage occurs near the surface, causing warping of the plasticizer-containing resin. Warping is particularly significant when the plasticizer-containing resin is in a sheet form.

[0011] Therefore, the object to be inspected in the method for estimating the mechanical properties of a resin according to an embodiment of the present invention is typically a resin that is resistant to ultraviolet light and is used in an environment exposed to ultraviolet light, such as PVC (polyvinyl chloride) containing plasticizers, which is used as a material for medical cable sheaths, medical tubes, catheters, etc. that are sterilized by ultraviolet light irradiation.

[0012] The physical property value representing the external shape is, for example, the radius of curvature of the surface of the object to be inspected or a physical property value uniquely determined based on the radius of curvature, or the area occupancy of the region where depressions are formed on the surface of the resin that is the object to be inspected, and is dependent on the amount of plasticizer desorbed from the surface of the resin. The radius of curvature of the surface of the object to be inspected or a physical property uniquely determined based on the radius of curvature represents the state of warping of the object to be inspected due to the desorption of the plasticizer. The physical property uniquely determined based on the radius of curvature is, for example, the curvature expressed as the reciprocal of the radius of curvature, or the Young's modulus of the resin, thickness, and residual stress determined from the radius of curvature.

[0013] The mechanical properties described above change when the test object is exposed to ultraviolet light, for example, the tensile stress at break in a tensile test, the elongation at break, or the modulus of elasticity at 100% elongation, which deteriorate due to the deterioration of the resin caused by ultraviolet light exposure. In other words, the external shape and mechanical properties of the resin being the test object depend on the amount of the plasticizer that has been detached from the surface of the resin due to ultraviolet light exposure.

[0014] Below is an example of the procedure for measuring physical property values ​​that represent the external shape using a confocal laser microscope. First, the surface of the object to be measured is scanned with a laser while keeping the height of the objective lens constant. At this time, two-dimensional data is obtained in which the amount of reflected light for each objective lens height and horizontal position is recorded. Next, the height of the objective lens is changed and the surface of the object to be measured is scanned in the same way. By repeating this process, multiple two-dimensional data with different recorded values ​​of the objective lens height are obtained.

[0015] The amount of reflected light is greatest when the laser is focused on the surface of the object being measured. Therefore, by extracting and stitching together the height of the objective lens at which the amount of reflected light is greatest for each horizontal position from the multiple two-dimensional data obtained, three-dimensional data representing the surface shape of the object being measured can be obtained. From this three-dimensional data, physical property values ​​representing the above-mentioned external shape can be obtained.

[0016] Confocal laser microscopes allow for non-contact, non-destructive measurement of the physical properties that represent the above-mentioned external shapes. In addition, because the laser spot can be narrowed (for example, to φ0.5-0.6 μm), they can measure the finer surface shapes of objects more precisely than other measurement methods, such as the stylus method.

[0017] A method for estimating the mechanical properties of a resin according to an embodiment of the present invention includes a correlation calculation step of irradiating ultraviolet light onto a sample made of the same material as an object to be inspected, measuring a first physical property value and a first mechanical property value of the ultraviolet-irradiated sample, and calculating the correlation between the first physical property value and the first mechanical property value; a measurement step of measuring a second physical property value of the object to be inspected; and an estimation step of estimating the value of the second mechanical property of the object to be inspected based on the second physical property value and the correlation.

[0018] The correlation between the physical property values ​​representing the external shape and the mechanical property values ​​can be obtained by measuring the physical property values ​​representing the external shape and the mechanical property values ​​of multiple samples irradiated with ultraviolet light under different conditions. Below, we will show examples of the method for measuring the physical property values ​​representing the external shape and the mechanical property values ​​to obtain the correlation, as well as examples of the measurement results.

[0019] (Example of measurement of physical properties and mechanical properties that represent the external shape) In this measurement, polyvinyl chloride containing a polyester-based plasticizer was used as the measurement target. Three samples (referred to as samples S1 to S3) for measuring physical property values ​​(first physical property values) representing the external shape of a single sheet of polyvinyl chloride containing a plasticizer, each approximately 1 mm thick, were cut out, and one sample (referred to as sample S0) for measuring mechanical property values ​​(first mechanical property values) was cut out. Furthermore, multiple rectangular sheets each about the size of a thumb were cut out from each of samples S1 to S3, and multiple dumbbell-shaped sheets were cut out from sample S0.

[0020] For each of samples S1, S2, and S3, ultraviolet light with a wavelength of 253.7 nm (hereinafter referred to as UV-C) was irradiated at an energy of 750 J / cm. 2A rectangular sheet irradiated on one side with UV-C at an energy of 1500 J / cm 2 A rectangular sheet was prepared, one side of which was irradiated with UV-C at an irradiation energy of 750 J / cm, and a rectangular sheet was prepared that was not irradiated with UV-C, and various tests were carried out to measure the physical properties that represent the appearance of the sheet. 2 Dumbbell-shaped sheet irradiated on one side with UV-C at an energy of 1500 J / cm 2 Dumbbell-shaped sheets were prepared, one side of which was irradiated with UV-C, and the other was not irradiated with UV-C, and various tests were carried out to measure the mechanical properties. UV-C irradiation was carried out using a storage cabinet with a germicidal lamp (Daishin Kogyo Co., Ltd. DM-5, Lamp GL-10) at an internal temperature of 25-40°C, an internal humidity of 28-65%, an internal pressure of 1 atmosphere (atmospheric pressure), and an illuminance of 1.3 mW / cm. 2 , irradiation time 160 hours (750J / cm 2 ) and 320 hours (1500J / cm 2 ) conditions.

[0021] The radius of curvature, a physical property that represents the warpage value, was measured using a confocal laser microscope (Keyence Corporation VK-X3000 (laser wavelength 661 nm)), and the curvature and residual stress were calculated from the obtained radius of curvature value. Residual stress was assumed from the deformation of a one-dimensional beam shape and calculated using the following equation 1. Here, σ is the residual stress, E is Young's modulus, t is thickness, and R is the radius of curvature. For Young's modulus, the Young's modulus of Soft-PVC (E = 35 MPa) was used.

[0022]

number

[0023] The size of the measurement area of ​​the sample surface using the confocal laser microscope (the range scanned horizontally with the laser) was 18,000 μm × 17,000 μm. In addition, 70 images of two-dimensional data obtained from one horizontal scan were acquired by changing the height of the objective lens, and these were combined to obtain three-dimensional data.

[0024] In addition, the mechanical properties, TS (tensile stress at break), TE (elongation (strain) at break), and 100%M (elastic modulus at 100% elongation) were measured by the tensile test specified in JIS K6251 (1994).

[0025] The following Table 1 shows the measurement results of the physical property values ​​(first physical property values) that represent the external shape and the mechanical property values ​​(first mechanical property values). The "curvature change rate" and "residual stress change rate" shown in Table 1 are 750 to 1500 J / cm 2 The curvature and residual stress change rates are the rate of change with respect to the UV-C irradiation energy between 1000 and 1000 s. The "average" is the average value of the physical properties of samples S1 to S3. The mechanical property values ​​obtained by testing sample S0 are also listed as the mechanical property values ​​of samples S1 to S3.

[0026] [Table 1]

[0027] Table 1 shows that as the UV irradiation energy increases, the warping of the sample increases and the mechanical properties deteriorate. This is thought to be because as the UV irradiation energy increases, the amount of plasticizer that desorbs from the surface of the sample (the surface irradiated by UV rays) increases, and the degree of resin deterioration increases, causing the sample to harden.

[0028] Figures 1(a), (b), and (c) are graphs showing the relationship between the average curvature and TS of samples S1 to S3, the relationship between the average curvature and TE of samples S1 to S3, and the relationship between the average curvature and 100%M of samples S1 to S3, respectively, using the physical property values ​​shown in Table 1.

[0029] 1(a), (b), and (c) show that there is a correlation between the mean curvature (first physical property value) and the mechanical properties (values ​​of the first mechanical property) of samples S1 to S3. Such a correlation, for example, a calibration curve obtained as an approximation line shown by the dotted line in FIG. 1, can be used as the "correlation between the physical property value representing the external shape and the value of the mechanical property" in the method for predicting the mechanical properties of a resin according to the embodiment of the present invention. Note that the calibration curves exemplified in FIGS. 1(a), (b), and (c) are approximate straight lines obtained by linear approximation, but when the number of data is sufficiently large, an approximate curve obtained by polynomial approximation or the like may also be used as the calibration curve.

[0030] The physical property values ​​(second physical property values) representing the external shape of the test object are measured in the same manner as the physical property values ​​(first physical property values) of samples S1 to S3. Based on the physical property values ​​(second physical property values) of the test object and the correlation (calibration curve), the mechanical property values ​​(second mechanical property values) of the test object can be estimated.

[0031] The correlations between the physical property values ​​representing the external shape and the mechanical property values ​​shown in Table 1 and Figures 1(a) to (c) are just examples, and a more accurate correlation can be obtained by increasing the number of samples measured (number of samples) and the number of UV-C irradiation energy conditions.

[0032] Figures 2(a) and (b) show graphs of the relationship between UV-C irradiation energy and the average curvature of samples S1 to S3, and the relationship between UV-C irradiation energy and the average residual stress of samples S1 to S3, respectively, using the physical properties shown in Table 1. Figure 3(a) shows a graph of the curvature of samples S1 to S3 after UV-C irradiation and their average values. Figure 3(b) shows a graph of the residual stress of samples S1 to S3 after UV-C irradiation and their average values. Figures 2(a), (b) and 3(a), (b) show that exposure to UV light increases the warpage of the samples.

[0033] 4(a) and (b) are image data showing the shape of the surface (ultraviolet irradiated surface) of sample S1 measured by a confocal laser microscope. The image data shown in FIG. 4(a) was obtained by irradiating UV-C at an energy of 1500 J / cm. 2 The image data shown in Figure 4(b) is from a sample irradiated with UV-C at an irradiation energy of 750 J / cm. 2 The results are from samples irradiated at 1000 kJ / cm².

[0034] The image data shown in Figures 4(a) and (b) shows the surface of the sample as viewed from the front, with each pixel in the horizontal direction (parallel to the paper surface of Figure 4) having a color corresponding to its position in the vertical direction (perpendicular to the paper surface of Figure 4), as indicated by the bar-shaped color palette on the right.

[0035] These image data show that the specimen has warped, with the surface height increasing from the center to the outside, and that the UV-C irradiation energy was 1500 J / cm 2 The sample irradiated with UV-C at an irradiation energy of 750 J / cm 2 This shows that the warpage is larger than that of the sample irradiated with 1000 kJ / cm2.

[0036] Figure 5(a) and (b) show UV-C irradiation energy of 1500 J / cm 2 5(a) and 5(b) are images showing the process of measuring the radius of curvature of sample S1 irradiated with laser light. As shown in Figure 5(a), 10 scanning lines were drawn at equal angles within a perfect circle centered on the center of the image data obtained by the confocal laser microscope. Next, a curve representing the surface shape was obtained on each scanning line. Then, a fitting analysis using a circular equation was performed on these curves to determine the radius of curvature for each. The average value of the 10 radius of curvature values ​​obtained from the curves on the 10 scanning lines was adopted as the radius of curvature of the sample.

[0037] Figures 6(a) and (b) show UV-C irradiation energy of 750 J / cm 26(a) and 6(b) are images showing the process of measuring the radius of curvature of sample S1 irradiated with laser light. As shown in Figure 6(a), 10 scanning lines were drawn at equal angles within a perfect circle centered on the center of the image data obtained by the confocal laser microscope. Next, a curve representing the surface shape was obtained on each scanning line. Then, a fitting analysis using a circular equation was performed on these curves to determine the radius of curvature for each. The average value of the 10 radius of curvature values ​​obtained from the curves on the 10 scanning lines was adopted as the radius of curvature of the sample.

[0038] Figures 5(b) and 6(b) show the curves obtained on one of the scan lines shown in Figures 5(a) and 6(a), respectively, and their fitting curves. The horizontal axis of the graphs in Figures 5(b) and 6(b) indicates the horizontal position of the sample surface, and the vertical axis indicates the height position of the sample surface. The graphs in Figures 5(b) and 6(b) show that, like the image data shown in Figures 4(a) and (b), the sample warps so that the surface height increases from the center to the outside, and that the UV-C irradiation energy was 750 J / cm. 2 The sample irradiated with UV-C at an irradiation energy of 750 J / cm 2 The number of scanning lines within the above circle can be freely set.

[0039] From the image data shown in Figures 5(a) and 6(a), the area occupancy rate of the region where depressions are formed on the surface of the sample can also be determined. The black regions scattered on the surface of the sample shown in these image data are regions where depressions were formed due to the desorption of plasticizer. Therefore, for example, by measuring the area of ​​the black regions within a specific range (called the measurement range) from the image data and calculating the ratio to the area of ​​the measurement range, i.e., the area occupancy rate, the area occupancy rate of the region where depressions are formed on the surface of the sample can be determined. The area occupancy rate of the region where depressions are formed on the surface of the sample can also be determined from images observed using an optical microscope.

[0040] (Effects of the embodiment) According to the method for estimating the mechanical properties of a resin according to the embodiment of the present invention, by using a confocal laser microscope or the like, it is possible to obtain physical property values ​​representing the external shape, such as warpage, of a resin containing a plasticizer in a non-contact and non-destructive manner, and the mechanical properties can be estimated using a correlation between the physical property values ​​representing the external shape that has been obtained in advance and the mechanical property values ​​(for example, a calibration curve such as that shown in Figures 1(a) to 1(c)).

[0041] Once the correlation between the physical property values ​​that represent the external shape and the mechanical property values ​​is obtained, the mechanical properties of the resin can be inspected without using tensile tests, allowing for stable, accurate, and nondestructive inspection of the resin's mechanical properties. For example, the inherent mechanical properties of stress-free resins can be accurately evaluated without being affected by plastic deformation and other alterations that occur during tensile tests. Furthermore, because the pretreatment process required for tensile tests is no longer necessary, mechanical properties can be inspected in a shorter time. Furthermore, confocal laser microscopes can narrow the laser spot diameter to the micrometer level, allowing for the inspection of very small samples.

[0042] (Summary of the embodiment) Next, the technical concept grasped from the above-described embodiment will be described.

[0043] [1] A method for estimating mechanical properties of a resin, comprising: a correlation calculation step of irradiating ultraviolet light onto a sample made of the same material as an object to be inspected, measuring a first physical property value and a first mechanical property value of the ultraviolet-irradiated sample, and calculating a correlation between the first physical property value and the value of the first mechanical property; a measurement step of measuring a second physical property value of the object to be inspected; and an estimation step of estimating the value of the second mechanical property of the object to be inspected based on the second physical property value and the correlation, wherein the object to be inspected is a resin, and the first and second physical property values ​​are values ​​representing the external shape.

[0044] [2] A method for estimating the mechanical properties of a resin described in [1] above, wherein the second physical property value is the radius of curvature of the surface of the object to be inspected or a physical property value that can be uniquely determined based on the radius of curvature, or the area occupancy rate of the region in which a depression is formed on the surface of the object to be inspected.

[0045] [3] The method for predicting the mechanical properties of a resin according to [1] above, wherein the resin is polyvinyl chloride containing a plasticizer.

[0046] [4] The method for estimating the mechanical properties of a resin described in [1] above, wherein the first and second mechanical properties are the tensile stress at break in a tensile test, the elongation at break, or the modulus of elasticity at 100% elongation.

[0047] [5] A method for estimating the mechanical properties of a resin according to any one of [1] to [4] above, wherein the correlation is obtained by measuring the first physical property value and the first mechanical property value of a plurality of samples irradiated with ultraviolet light under different conditions.

[0048] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and various modifications can be made without departing from the spirit of the invention. Furthermore, the above-described embodiments do not limit the scope of the invention according to the claims. It should be noted that not all of the combinations of features described in the embodiments are necessarily essential to the means for solving the problems of the invention.

Claims

1. a correlation calculation step of irradiating ultraviolet light onto a sample made of the same material as the inspection target, measuring a first physical property value and a first mechanical property value of the ultraviolet-irradiated sample, and calculating a correlation between the first physical property value and the first mechanical property value; a measuring step of measuring a second physical property value of the inspection object; an estimation step of estimating a value of a second mechanical property of the test object based on the second physical property value and the correlation; Including, the inspection object is a resin, The first and second physical property values ​​are values ​​representing an external shape. A method for predicting the mechanical properties of resins.

2. the second physical property value is a radius of curvature of the surface of the inspection object, a value of a physical property that can be uniquely determined based on the radius of curvature, or an area occupancy rate of a region in which a depression is formed on the surface of the inspection object; The method for predicting mechanical properties of a resin according to claim 1.

3. The resin is polyvinyl chloride containing a plasticizer. The method for predicting mechanical properties of a resin according to claim 1.

4. The first and second mechanical properties are a tensile stress at break, an elongation at break, or an elastic modulus at 100% elongation in a tensile test. The method for predicting mechanical properties of a resin according to claim 1.

5. the correlation is obtained by measuring the first physical property value and the first mechanical property value of a plurality of samples irradiated with ultraviolet light under different conditions; The method for predicting mechanical properties of a resin according to any one of claims 1 to 4.

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