Test piece, making method for test piece, method for identifying stress relaxation temperature area of thermoplastic resin, prediction method for deformation and / or generation of fragile part of molded body, and prediction method for residual stress and / or strain of molded body

Abstract

To provide a test piece capable of sealing a molded piece with a simple method to prevent a thermoplastic resin composition of the melted molded piece from leaking to the outside.SOLUTION: A test piece of an embodiment is used for measuring dynamic viscoelasticity. The test piece includes: a molded piece composed of a thermoplastic resin composition (A); and a coating material composed of a thermoplastic resin composition (B) having a melting point or a glass-transition temperature higher than a temperature of one of a melting point or a glass-transition temperature of the thermoplastic resin composition (A), for coating the molded piece. The coating material includes: a transmission material composed of a thermoplastic resin composition (B1) that coats a surface of a part of the molded piece and transmits laser light; and an absorption material composed of a thermoplastic resin composition (B2) that coats a surface of the molded piece, which is different from the surface coated with the transmission material, and absorbs the laser light. The molded piece is sealed by bonding the transmission material and the absorption material with each other.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a test piece for measuring dynamic viscoelasticity and a method for producing the same, as well as a technique for identifying the stress relaxation temperature range of a thermoplastic resin composition based on the results of measuring dynamic viscoelasticity. [Background technology]

[0002] Insert moldings, which are composites of metal parts and resin, are used in automobiles, electrical and electronic parts, and other applications for various purposes, such as reducing the weight of electrical and electronic control parts and metal parts. When such insert-molded products are used in environments with large temperature changes, heat shock cracking, which occurs due to the difference in the linear expansion coefficient between the resin and the metal, is often an issue, and various resin materials and processing methods have been developed to address this issue. For example, adding various elastomers to resin materials is one way to improve heat shock resistance. However, because the effects of various additives cannot be determined without actual evaluation, selecting a resin material requires a huge amount of work.

[0003] On the other hand, a method has been proposed for obtaining a resin composition with excellent stress relaxation properties from the results of dynamic viscoelasticity measured by dynamic mechanical analysis (DMA). A resin composition with excellent stress relaxation properties is thought to be less prone to the accumulation of internal strain and to have excellent heat shock resistance. For example, Patent Document 1 states that a resin composition with a tan δ peak temperature of 0 to 60°C and a peak value of 0.8 to 5 or less, obtained by dynamic viscoelasticity measurement at a temperature range of -40 to 150°C and a frequency of 10 rad / s (1.6 Hz), is considered to have excellent stress relaxation properties. According to Patent Document 2, an automotive molded article molded from a thermoplastic resin composition containing a cross-copolymerized olefin-aromatic vinyl compound-diene copolymer is considered to have excellent stress relaxation properties when the maximum and minimum values ​​of tan δ in the temperature range of 0 to 30°C are 0.5 or more and 0.05 or more, respectively, and the difference between the maximum and minimum values ​​is 2.0 or less. These documents disclose the dynamic viscoelastic properties of resin compositions that are said to have excellent stress relaxation properties, but it is unclear which temperature range is most effective for stress relaxation in the resin compositions.

[0004] Patent Document 3 describes a method for determining the stress relaxation temperature range of a thermoplastic resin composition based on the results of dynamic viscoelasticity measurements using a test piece formed from a thermoplastic resin composition and completely coated with a coating resin having a temperature higher than the melting point or glass transition temperature of the composition. This method is said to enable easy determination of the temperature range most effective for stress relaxation of the resin composition. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2021 / 095683 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-265544 [Patent Document 3] Japanese Patent Application Publication No. 2023-044928 Summary of the Invention [Problem to be solved by the invention]

[0006] The test piece described in Patent Document 3 preferably has good adhesion between the molded piece and the coating resin. Patent Document 3 also describes roughening the surface of the molded piece by irradiating it with a laser or forming grooves to improve adhesion between the molded piece and the coating resin. However, to achieve sufficient adhesion between the molded piece and the coating resin, it is not enough to simply roughen the surface of the molded piece; for example, it is necessary to use a thermoplastic resin composition containing glass fibers as the molded piece. Glass fibers transmit laser light and are exposed on the surface of the molded piece after laser treatment, so they can penetrate between the glass fibers in the coating resin, improving adhesion between the molded piece and the molded piece.

[0007] Another possible method for producing the test specimen in Patent Document 3 is to perform insert molding of a coating resin using a molded specimen as an insert member, and then coat the molded specimen with the coating resin (overmolding). In this method, it is desirable to perform laser treatment and insert molding on each of the six sides of the rectangular parallelepiped molded specimen to improve adhesion with the coating resin and ensure appropriate coating on all surfaces. However, it has been found that it is practically difficult to coat all surfaces of the molded specimen using this method, and it is difficult to produce a test specimen with a completely coated molded specimen. If the molded specimen is not completely coated with the coating resin, the composition of the molded specimen that melts inside the test specimen at a high temperature will leak out during dynamic viscoelasticity measurement.

[0008] Therefore, an object of the present invention is to provide a test piece and a method for producing the same that can easily seal a molded piece and prevent leakage of the molten thermoplastic resin composition from the molded piece. Another object of the present invention is to use such a test piece to easily determine which temperature range is most effective for stress relaxation of a thermoplastic resin composition. [Means for solving the problem]

[0009] A first aspect of the present invention is a test piece used in dynamic viscoelasticity measurement for identifying the stress relaxation temperature range of a thermoplastic resin composition. This test piece is a molded piece made of the thermoplastic resin composition; and a covering material that covers the molded piece and is made of a thermoplastic resin composition having a melting point or glass transition temperature higher than the melting point or glass transition temperature of the thermoplastic resin composition, whichever is higher. The coating material is a transmitting material made of a thermoplastic resin composition that transmits laser light and covers a surface of a portion of the molded piece; and an absorbing material made of a thermoplastic resin composition that absorbs laser light, which covers a surface of the molded piece that is different from the surface covered by the transmitting material. The molded piece is sealed by bonding the transparent material and the absorbent material together.

[0010] A second aspect of the present invention is a test piece used in dynamic viscoelasticity measurement carried out to identify the stress relaxation temperature range of a thermoplastic resin composition. This test piece is a molded piece made of the thermoplastic resin composition; and a covering material that covers the molded piece and is made of a thermoplastic resin composition having a melting point or glass transition temperature higher than the melting point or glass transition temperature of the thermoplastic resin composition, whichever is higher. The coating material is a plate-shaped absorber made of a thermoplastic resin composition that absorbs laser light, the absorber having a hole that penetrates in the plate thickness direction and in which the molded piece is to be placed; The device comprises a pair of plate-shaped transmissive materials made of a thermoplastic resin composition that transmits laser light, the pair of transmissive materials being placed on top of the absorbing material so as to sandwich the molded piece placed in the hole from both sides in the plate thickness direction of the absorbing material. The transmissive material and the absorbing material are bonded to each other in a circumferential region surrounding the hole at each interface between the absorbing material and the pair of transmissive materials.

[0011] A third aspect of the present invention is a method for preparing a test piece used in dynamic viscoelasticity measurement carried out to identify the stress relaxation temperature range of a thermoplastic resin composition. This method is a plate-shaped absorber blank made of a thermoplastic resin composition that absorbs laser light and has a melting point or glass transition temperature higher than the higher of the melting point or glass transition temperature of the thermoplastic resin composition, wherein a step of filling the thermoplastic resin composition, which has a specified stress relaxation temperature range, into holes that penetrate the plate thickness direction and are provided in an absorber-intended region of the absorber blank that will become an absorber constituting part of the test piece; a step of stacking a pair of plate-shaped transparent materials made of a thermoplastic resin composition that transmits laser light and has a melting point or glass transition temperature higher than the higher of the melting point or glass transition temperature of the thermoplastic resin composition filled in the holes, on the absorber-intended region so as to sandwich the thermoplastic resin composition filled in the holes from both sides in the plate thickness direction of the absorber-intended region; and irradiating a laser beam from the side of the transparent material toward the intended absorbent material area in a peripheral area surrounding the hole at each interface between the intended absorbent material area and the pair of plate-shaped transparent materials to heat and melt the intended absorbent material area, thereby joining the transparent material and the intended absorbent material area.

[0012] A fourth aspect of the present invention is a method for identifying the stress relaxation temperature range of a thermoplastic resin composition. This method is the temperature of the test piece is lowered to a temperature equal to or lower than the glass transition temperature of the thermoplastic resin composition of the molded piece, and then a temperature-raising process is performed so that the temperature is raised to a temperature lower than the higher of the melting point or the glass transition temperature of the thermoplastic resin composition of the transmitting material and the lower of the higher of the melting point or the glass transition temperature of the thermoplastic resin composition of the absorbing material, and a temperature-lowering process is performed so that the temperature is lowered to a temperature equal to or lower than the glass transition temperature of the thermoplastic resin composition of the molded piece, and dynamic viscoelasticity of the test piece is measured; The stress relaxation temperature range of the thermoplastic resin composition of the molded piece is identified based on the difference between the dynamic viscoelasticity of the test piece measured during the temperature increase process and the temperature decrease process.

[0013] A fifth aspect of the present invention is a method for predicting deformation and / or occurrence of a fragile part in a molded body. This method is calculating a relaxation modulus of the thermoplastic resin composition of the molded piece based on the storage modulus and loss modulus of the thermoplastic resin composition of the molded piece during the temperature decrease process, which are obtained by a method for identifying a stress relaxation temperature range of a thermoplastic resin composition; and a step of modeling the relaxation modulus of the thermoplastic resin composition of the molded piece, and predicting, based on the modeled relaxation modulus of the thermoplastic resin composition, deformation and / or occurrence of fragile parts in the molded body when the molded body contains, as a main component, a thermoplastic resin composition that is configured in the same way as the thermoplastic resin composition of the molded piece.

[0014] A sixth aspect of the present invention is a method for predicting residual stress and / or distortion of a molded body. This method is calculating a relaxation modulus of the thermoplastic resin composition of the molded piece based on the storage modulus and loss modulus of the thermoplastic resin composition of the molded piece during the temperature decrease process, which are obtained by a method for identifying a stress relaxation temperature range of a thermoplastic resin composition; and a step of modeling the relaxation modulus of the thermoplastic resin composition of the molded piece, and predicting the residual stress and / or strain of the molded body when the molded body contains, as a main component, a thermoplastic resin composition that is configured in the same way as the thermoplastic resin composition of the molded piece, based on the modeled relaxation modulus of the thermoplastic resin composition. [Effects of the Invention]

[0015] According to the above-mentioned aspect, a test piece can be obtained in which the molded piece can be sealed in a simple manner and the thermoplastic resin composition of the molten molded piece can be prevented from leaking out. Furthermore, according to the above-mentioned aspect, the test piece can be used to simply determine which temperature range is most effective for stress relaxation of the thermoplastic resin composition. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 10 is an external view showing a test piece according to a second embodiment. [Figure 2] FIG. 10 is a view showing a cross section in the plate thickness direction of a test piece according to a second embodiment. [Figure 3] 1A to 1C are diagrams illustrating a method for producing a test piece according to an embodiment. [Figure 4]FIG. 10 is a diagram showing the results of DMA measurement using a sample of a test piece according to an embodiment. [Figure 5] FIG. 10 is a diagram showing the results of DMA measurements using comparative test piece samples. [Figure 6] FIG. 1 is a diagram showing the DMA measurement results of a test piece sample according to an embodiment and a comparative sample, superimposed on one another. DETAILED DESCRIPTION OF THE INVENTION

[0017] (First embodiment) The test piece of the first embodiment is a test piece used in dynamic viscoelasticity measurement (DMA measurement) performed to identify the stress relaxation temperature range of a thermoplastic resin composition. The thermoplastic resin composition whose stress relaxation temperature range is to be identified is hereinafter referred to as thermoplastic resin composition (A). In this specification, the stress relaxation temperature range refers to a temperature range or temperature range that is effective for stress relaxation of the thermoplastic resin composition (A) (stress relaxation is likely to proceed).

[0018] The thermoplastic resin composition (A) contains a thermoplastic crystalline resin or a thermoplastic amorphous resin. The thermoplastic crystalline resin is not limited, but examples thereof include polyacetal (POM), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyphenylene sulfide (PPS), and liquid crystal polymers (LCPs) such as condensation polymers of p-hydroxybenzoic acid and 2,6-hydroxynaphthoic acid. The thermoplastic amorphous resin is not limited, but examples thereof include polycarbonate (PC), cyclic polyolefin (COP), and cyclic polyolefin copolymer (COC).

[0019] In addition to the thermoplastic crystalline resin and the thermoplastic amorphous resin, the thermoplastic resin composition (A) may contain additives such as elastomers, fillers such as glass fibers and inorganic powders, nucleating agents, colorants such as dyes and pigments, antioxidants, stabilizers, plasticizers, lubricants, mold release agents, and flame retardants. Examples of elastomers include olefin polymers such as ethylene-ethyl acrylate copolymers, polyester elastomers, styrene elastomers, polyamide elastomers, silicone elastomers, and urethane elastomers.

[0020] The test piece of the first embodiment includes a molded piece and a covering material. The molded piece is formed by molding the thermoplastic resin composition (A). The coating material is made of a thermoplastic resin composition (hereinafter referred to as thermoplastic resin composition (B)) having a melting point or glass transition temperature higher than the higher of the melting point or glass transition temperature of the thermoplastic resin composition (A), and covers the molded piece. By coating the molded piece with such a coating material, even if the molded piece melts inside the test piece heated to a high temperature, the molten thermoplastic resin composition (A) is retained inside the coating material.

[0021] The thermoplastic resin composition (B) contains a thermoplastic crystalline resin or a thermoplastic amorphous resin. The thermoplastic crystalline resin is not limited, but examples thereof include polyacetal (POM), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyphenylene sulfide (PPS), and liquid crystal polymers (LCPs) such as condensation polymers of p-hydroxybenzoic acid and 2,6-hydroxynaphthoic acid. The thermoplastic amorphous resin is not limited, but examples thereof include polycarbonate (PC), cyclic polyolefin (COP), and cyclic polyolefin copolymer (COC).

[0022] The covering material includes a transmitting material and an absorbing material.

[0023] The transmitting material is made of a thermoplastic resin composition (hereinafter referred to as thermoplastic resin composition (B1)) that transmits laser light, and coats a portion of the surface of the molded piece. The thermoplastic resin composition (B1) is a thermoplastic resin composition that transmits laser light, among the compositions that fall under the category of thermoplastic resin composition (B). Because the transmitting material is made of the thermoplastic resin composition (B1), it can transmit laser light when laser welding (described later) is performed between the transmitting material and the absorbing material.

[0024] The thermoplastic resin composition (B1) may further contain additives such as fillers such as glass fibers and inorganic powders, nucleating agents, antioxidants, stabilizers, plasticizers, lubricants, release agents, and flame retardants, within the range that does not impair the function of the transmitting material that transmits laser light. On the other hand, it is preferable that the thermoplastic resin composition (B1) does not contain an absorbent, which will be described later.

[0025] The absorbent is made of a thermoplastic resin composition that absorbs laser light (hereinafter referred to as thermoplastic resin composition (B2)), and covers a surface of the molded piece that is different from the surface covered by the transparent material. The absorbent covers all surfaces of the molded piece that are not covered by the transparent material. The thermoplastic resin composition (B2) is a thermoplastic resin composition that absorbs laser light, among compositions that fall under the category of thermoplastic resin composition (B). Since the absorbent is made of the thermoplastic resin composition (B2), it can absorb laser light, generate heat, and melt when laser welding is performed between the transparent material and the absorbent. Therefore, the thermoplastic resin composition (B2) contains an absorbent that absorbs laser light, in addition to a thermoplastic crystalline resin and a thermoplastic amorphous resin.

[0026] The absorbent can be selected depending on the wavelength of the laser light, and inorganic or organic pigments can be used. Examples of inorganic pigments include black pigments such as carbon black (e.g., acetylene black, lamp black, thermal black, furnace black, channel black, ketjen black, etc.), red pigments such as iron oxide red, orange pigments such as molybdate orange, and white pigments such as titanium oxide. Examples of organic pigments include azo-based, phthalocyanine-based, quinacridone-based, dioxazine-based, isoindoline-based, and anthraquinone-based pigments. These absorbents can be used alone or in combination of two or more.

[0027] The content of the absorbent in the thermoplastic resin composition (B2) is preferably 0.01 parts by mass or more, more preferably 0.03 parts by mass or more, relative to 100 parts by mass of the thermoplastic crystalline resin or thermoplastic amorphous resin in the thermoplastic resin composition (B2), in order to ensure the effect of the absorbent absorbing laser light and generating heat. On the other hand, the content of the absorbent in the thermoplastic resin composition (B2) is preferably 0.6 parts by mass or less, more preferably 0.3 parts by mass or less, relative to 100 parts by mass of the thermoplastic crystalline resin or thermoplastic amorphous resin in the thermoplastic resin composition (B2).

[0028] The thermoplastic resin composition (B2) may further contain additives such as fillers such as glass fibers and inorganic powders, nucleating agents, antioxidants, stabilizers, plasticizers, lubricants, release agents, and flame retardants, within the range that does not impair the function of the absorbent that absorbs laser light.

[0029] The thermoplastic resins contained in the thermoplastic resin composition (B1) and the thermoplastic resin composition (B2) may be different from each other, but are preferably the same. If the thermoplastic resins contained in the two compositions are different, the bond strength between the laser-welded transmitting material and absorbing material is likely to be weak, and there is a risk of peeling during DMA measurement. Furthermore, if the coating material contains multiple types of thermoplastic resins, the number of temperature ranges in which the viscoelastic properties change significantly during DMA measurement increases, making it difficult to evaluate the viscoelastic properties of the thermoplastic resin composition (A).

[0030] In the test piece of the first embodiment, the molded piece is sealed by bonding the transmitting material and the absorbing material together. This prevents the thermoplastic resin composition (A) from molten in the molded piece from leaking out when the temperature of the test piece rises during DMA measurement. By performing DMA measurement using such a test piece, it is possible to measure the viscoelastic properties of the thermoplastic resin composition (A) during the solidification process, in which the thermoplastic resin composition (A) changes from a liquid to a solid, and to determine the temperature range that is most effective for stress relaxation of the thermoplastic resin composition (A).

[0031] Furthermore, with the test piece of the first embodiment, the transmitting material and the absorbing material can be joined by laser welding to seal the molded piece. Therefore, there is no need to perform insert molding using the molded piece as an insert member, cover (overmold) the molded piece with a coating resin that serves as a coating material, and then seal the molded piece. Furthermore, there is no need to perform surface treatment to improve adhesion between the molded piece and the coating material, nor is there a need to fill the coating resin with a filler such as glass fiber, which is necessary for surface treatment. Examples of surface treatments include irradiating the surface of the molded piece with laser light to roughen the surface or form grooves, or irradiating the surface of the molded piece with vacuum ultraviolet light in an oxygen atmosphere to generate polar functional groups such as carboxyl groups and hydroxyl groups on the surface of the molded piece and activate the surface.

[0032] Therefore, according to the test piece of the first embodiment, the molded piece can be sealed in a simple manner, and the thermoplastic resin composition (A) in the molten molded piece can be prevented from leaking out.

[0033] The transmitting material may be disposed on each of a plurality of surfaces of the molded piece, separated by surfaces of the molded piece that are covered by an absorbing material, as in the second embodiment described below.

[0034] (Second embodiment) Fig. 1 is an external view showing a test piece of the second embodiment. Fig. 2 is a view showing a cross section of the test piece of the second embodiment in the plate thickness direction. The cross section shown in Fig. 2 is a cross section along a plane perpendicular to the longitudinal direction of the test piece 1 (the Y direction shown in Fig. 1).

[0035] The test piece 1 of the second embodiment is used for DMA measurement to identify the stress relaxation temperature range of a thermoplastic resin composition. The thermoplastic resin composition has the same constitution as the thermoplastic resin composition (A) described in the first embodiment.

[0036] The test piece 1 includes a molded piece 3 and a covering material 5 .

[0037] The molded piece 3 is formed by molding the thermoplastic resin composition (A). The molded piece 3 in the illustrated example has a flat plate shape.

[0038] The covering material 5 is made of a thermoplastic resin composition (B) and covers the molded piece 3. The thermoplastic resin composition (B) has the same structure as the thermoplastic resin composition (B) described in the first embodiment.

[0039] The covering material 5 has an absorbing material 13 and a pair of transmitting materials 11, 11.

[0040] The absorbent 13 is a plate-shaped member made of a thermoplastic resin composition (B2) and has a hole 13a penetrating in the plate thickness direction (Z direction) in which the molded piece 3 is placed. The thermoplastic resin composition (B2) is configured in the same manner as the thermoplastic resin composition (B2) described in the first embodiment. The shape of the hole 13a in the illustrated example is rectangular when viewed in the plate thickness direction. It is preferable that the molded piece 3 is placed in the hole 13a without leaving a gap between it and the absorbent 13. Note that the length of the test piece 1 in the short side direction (X direction) is shown longer in FIG. 2 than the length shown in FIG. 1.

[0041] The pair of transmitting materials 11, 11 are plate-like members made of a thermoplastic resin composition (B1), and are placed on top of the absorbing material 13 so as to sandwich the molded piece 3 placed in the hole 13a from both sides in the plate thickness direction of the absorbing material 13. The thermoplastic resin composition (B1) has the same structure as the thermoplastic resin composition (B1) described in the first embodiment.

[0042] In the test piece 1 of the second embodiment, the transmitting material 11 and the absorbing material 13 are bonded to each other in the circumferential regions 12a, 12a surrounding the holes 13a at the interfaces 12, 12 between the absorbing material 13 and the pair of transmitting materials 11, 11. The circumferential region 12a surrounds the holes 13a without interruption. Therefore, the holes 13a are blocked by the transmitting material 11 from both sides in the thickness direction, and the molded piece 3 within the holes 13a is sealed. This prevents the thermoplastic resin composition (A) of the molded piece 3 from leaking out due to the temperature rise of the test piece 1 during DMA measurement. The bonding between the transmitting material 11 and the absorbing material 13 in the circumferential region 12a can be performed by laser welding, as described below.

[0043] The circumferential region 12a may be the entire region of the interface 12, or may be only a portion of the region. In the example shown in Fig. 2, the circumferential region 12a is the entire region of the interface 12. When the circumferential region 12a is only a portion of the interface 12, it preferably includes the edge region of the absorbent material 13 that contacts the hole 13a. If the thermoplastic resin composition (A) of the molten molded piece 3 penetrates the interface 12, the transmitting material 11 and the absorbent material 13 may peel off during DMA measurement.

[0044] According to the test piece 1 of the second embodiment, the molded piece 3 can be sealed by a simple method, and it is possible to prevent leakage of the thermoplastic resin composition (A) from the molten molded piece 3. The test piece 1 of the second embodiment is a plate-like body having a structure in which a pair of plate-like transmitting material 11 and absorbing material 13 are stacked, and therefore is suitable for applying bending vibration in a three-point bending mode during DMA measurement.

[0045] The absorbent material 13 and the transmitting material 11 are preferably plate-like bodies stacked on top of each other, as in the example shown in Figures 1 and 2. The thickness of the absorbent material 13 in the thickness direction is preferably greater than the thickness of the transmitting material 11 stacked on one side of the absorbent material 13 in the thickness direction. This increases the volume of the holes 13a in the absorbent material 13, allowing for a larger amount of thermoplastic resin composition (A) in the test piece 1, resulting in accurate DMA measurement results that significantly reflect the viscoelastic properties of the molded piece 3. The thickness of the absorbent material 13 in the thickness direction is preferably 1.5 mm or more, more preferably 2 mm or more. On the other hand, the thickness of the absorbent material 13 in the thickness direction is preferably 3 mm or less so that the test piece 1 does not become too thick in the thickness direction.

[0046] The thickness of the transparent material 11 in the plate thickness direction is preferably a thickness that provides a transmittance of 20% or more for laser light irradiated from the transparent material 11 side toward the absorbing material 13, and more preferably a thickness that provides a transmittance of 30% or more. When the transmittance of laser light passing through the transparent material 11 is within the above range, sufficient bonding strength can be obtained between the laser-welded transparent material 11 and the absorbing material 13. The transmittance of laser light is expressed as the ratio of the intensity of laser light having a wavelength of 940 nm irradiated onto the transparent material 11 in the plate thickness direction to the intensity of the laser light after the laser light has passed through the transparent material 11 before the laser light is incident on the transparent material 11. The intensity of the laser light is measured using a spectrophotometer. The thickness of the transparent material 11 in the plate thickness direction is preferably less than 1.5 mm, and more preferably 1.3 mm or less. The upper limit of the transmittance of the laser light passing through the transparent material 11 is not particularly limited, but is, for example, 90%.

[0047] The thickness of the test piece 1 in the thickness direction is preferably 5 mm or less, more preferably 4.5 mm or less, in order to perform DMA measurement without any problems. If the thickness of the test piece 1 exceeds the above range, it becomes difficult to apply bending vibration at an appropriate frequency, which may hinder the DMA measurement and its accuracy. On the other hand, the thickness of the molded piece 3 in the thickness direction is preferably 1.5 mm or more, more preferably 2 mm or more, in order to ensure a sufficient amount of thermoplastic resin composition (A) in the test piece 1.

[0048] The shape of the test piece 1 is preferably rectangular when viewed in the plate thickness direction (Z). A test piece 1 of this shape is suitable for applying bending vibration in a three-point bending mode during DMA measurement. The length of the test piece 1 in the longitudinal direction (Y direction) is preferably 10 to 50 mm. The length of the test piece 1 in the lateral direction (X direction) is preferably 10 to 12.5 mm.

[0049] In the test piece described above, if the temperature region around the glass transition temperature TgB of the thermoplastic resin composition (B) (herein referred to as the TgB region) overlaps with the temperature region around the melting point TmA of the thermoplastic resin composition (A) (herein referred to as the TmA region), the viscoelastic properties of the test piece 1 during DMA measurement will change significantly, making it difficult to evaluate the viscoelastic properties of the thermoplastic resin composition (A). The TgB region of the thermoplastic resin composition (B) is, for example, a temperature region of 85°C to 90°C when the resin contained in the thermoplastic resin composition (B) is polyphenylene sulfide (PPS). The TmA region of the thermoplastic resin composition (A) is, for example, a temperature region of 155°C to 175°C when the resin contained in the thermoplastic resin composition (A) is polyacetal (POM). Thus, when the thermoplastic resin composition (A) contains a thermoplastic crystalline resin, it is preferable that the TgB region of the thermoplastic resin composition (B) and the TmA region of the thermoplastic resin composition (A) do not overlap. Furthermore, the TgB region of the thermoplastic resin composition (B) is more preferably higher than the temperature region between the glass transition temperature TgA and the melting point TmA of the thermoplastic resin composition (A) (herein referred to as the TgA-TmA region). For example, the TgA-TmA region of the thermoplastic resin composition (A) is a temperature region of -50 to 70°C, where TgA is -50°C and TmA is 70°C, and the TgB region of the thermoplastic resin composition (B) is a temperature region of 85 to 90°C. With a test piece that satisfies this relationship, for example, when the thermoplastic resin composition (A) is in a rubbery state, the thermoplastic resin composition (B) is in a glassy state. This prevents significant changes in the viscoelastic properties of the test piece 1 during DMA measurement, making it easier to evaluate the viscoelastic properties of the thermoplastic resin composition (A).

[0050] (Method of preparing test specimens) Next, a method for producing a test piece according to one embodiment will be described with reference to Fig. 3. Fig. 3 is a diagram for explaining a method for producing a test piece according to one embodiment. The method of this embodiment is a method for producing the test piece 1 of the second embodiment, and includes a filling step ST1, a stacking step ST2, and a joining step ST3.

[0051] In the method of this embodiment, prior to the filling step ST1, an absorber plate 20 as shown in FIG. 3(a) is prepared. The absorber plate 20 is a plate-shaped member made of a thermoplastic resin composition (B2) that has a melting point or glass transition temperature higher than the higher of the melting point or glass transition temperature of the thermoplastic resin composition (A) and absorbs laser light. The absorber plate 20 has an absorber-intended region 23 (the region between two dashed lines in FIG. 3(b)) that will become the absorber 13 that constitutes part of the test piece 1. As shown in FIG. 3(b), the absorber-intended region 23 has holes 23a that penetrate through it in the plate thickness direction. The holes 23a are the portions that will become the holes 13a of the absorber 13. The holes 23a may be formed using, for example, a drill press or a jigsaw, or by machining.

[0052] The filling step ST1 is a step of filling the thermoplastic resin composition (A) into the holes 23a of the absorbent base plate 20. The filling step can be performed, for example, by the method shown in Fig. 3(c) (hot pressing, which will be described later).

[0053] In the example shown in Figure 3, after the filling step ST1 of the absorbent base plate 20 in which the thermoplastic resin composition (A) is filled into the holes 23a, the absorbent planned area portion 23 is cut out by cutting or the like (see Figure 3(d)), but the cutting out of the absorbent planned area portion 23 may also be performed, for example, after the joining step ST3.

[0054] The stacking step ST2 is a step of stacking a pair of plate-shaped transmissive materials 11, 11 on the absorber-intended region 23 so as to sandwich the thermoplastic resin composition (A) filled in the holes 23a from both sides in the plate thickness direction of the absorber-intended region 23. The pair of plate-shaped transmissive materials 11, 11 are configured in the same manner as the pair of transmissive materials 11, 11 of the test piece 1 described above.

[0055] In the joining step ST3, a peripheral region surrounding the hole 23a at the interface between the absorber-intended region 23 and the pair of plate-like transparent materials 11 is irradiated with laser light L from the side of the transparent materials 11 toward the absorber-intended region 23 to heat and melt the absorber-intended region 23, thereby joining the transparent materials 11 and the absorber-intended region 23. In the example shown in FIG. 3(e), the peripheral region is represented by a hatched frame-like region and is the edge region (inner peripheral region) of the absorber-intended region 23 that contacts the hole 23a. The laser light source is not particularly limited, and examples that can be used include a dye laser, a gas laser (excimer laser, argon laser, krypton laser, helium-neon laser, etc.), a solid-state laser (YAG laser, etc.), and a semiconductor laser. A pulsed laser is typically used as the laser light. The laser light L irradiated toward the absorber-intended region 23 moves along the longitudinal direction of the hole 23a, thereby irradiating the entire circumferential region. As a result, the portion of the absorber-intended region 23 that absorbs the laser light in the circumferential region generates heat and melts, and the heat propagates to the transmitting material 11, melting the transmitting material 11. The melted portions of the absorber-intended region 23 and the transmitting material 11 cool and become tightly adhered, thereby bonding them together. This type of laser welding is performed on each side of the absorber-intended region 23. In this manner, the test piece is produced.

[0056] According to the method of this embodiment, a test piece can be produced by joining the absorber-designated region 23 and the transmissive material 11 by laser welding. At this time, by joining the absorber-designated region 23 and the transmissive material 11 in a circumferential region, the holes 23a in the absorber-designated region 23 are blocked and the thermoplastic resin composition (A) filled in the holes 23a is sealed. In this way, according to the method of this embodiment, the thermoplastic resin composition (A) can be sealed in a simple manner.

[0057] In the filling step ST1, a pair of plates 30, 30 made of a thermoplastic resin composition (A) are placed on the absorber-designated region 23 so as to block the holes 23a from both sides in the thickness direction of the absorber base plate 20. The plates 30, 30 are then pressed against the absorber-designated region 23 (heat pressing) while being heated at a temperature (heat pressing temperature) higher than the higher of the melting point or glass transition temperature of the thermoplastic resin composition (A) but lower than the higher of the melting point or glass transition temperature of the thermoplastic resin composition (B2). This melts the thermoplastic resin composition (A) and fills the holes 23a. This reduces the likelihood of air bubbles remaining in the holes 23a, increases the amount of thermoplastic resin composition (A) in the test piece 1, and results in more accurate DMA measurement results. The thermoplastic resin composition (A) fills the holes 23a and solidifies within the holes 23a to form a molded piece 3, which is formed using the absorber-designated region 23 as a mold.

[0058] The heat pressing is performed by placing a pair of metal plates (not shown) on the pair of plate materials 30, 30 placed on the absorber-intended region 23 so as to sandwich the pair of plate materials 30, 30 from both sides in the plate thickness direction, and pressing them against the absorber-intended region 23. At this time, the metal plates are heated to the above-mentioned heat pressing temperature. The sizes of the plate materials 30, 30 are set so that the amount of thermoplastic resin composition (A) that melts and fills the holes 23a is greater than the volume of the holes 23a.

[0059] On the other hand, in the filling step ST1, instead of using the plate material 30, pellets (not shown) of the thermoplastic resin composition (A) may be laid in the holes 23a and hot-pressed to melt and solidify the pellets, thereby filling the holes 23a with the thermoplastic resin composition (A).

[0060] (Method for identifying the stress relaxation temperature range of a thermoplastic resin composition) One embodiment is a method for identifying the stress relaxation temperature range of a thermoplastic resin composition. The thermoplastic resin composition has the same structure as the thermoplastic resin composition (A) described above. In this method, a test piece (hereinafter also referred to as test piece 1) of the above embodiment is cooled to a temperature equal to or lower than the glass transition temperature of the thermoplastic resin composition (A), and then the temperature is changed so that a heating process (heating process) and a cooling process (cooling process) of the test piece 1 are successively performed, and the dynamic viscoelasticity of the test piece 1 is measured. The stress relaxation temperature range of the thermoplastic resin composition (A) is identified based on the difference between the dynamic viscoelasticity of the test piece 1 measured during the heating process and the cooling process. During the temperature increase process, the test piece 1 is heated to a temperature below the lower of the higher of the melting point or glass transition temperature of the thermoplastic resin composition (B1) of the transmitting material 11 and the higher of the melting point or glass transition temperature of the thermoplastic resin composition (B2) of the absorbing material 13. During the temperature decrease process, the test piece 1 is cooled to a temperature below the glass transition temperature of the thermoplastic resin composition (A). The thermoplastic resin composition (B1) and the thermoplastic resin composition (B2) are configured in the same manner as the thermoplastic resin composition (B1) and the thermoplastic resin composition (B2) described above. The difference in dynamic viscoelasticity is not limited, but may be, for example, the ratio or difference of the loss tangent (tanδ) between the temperature increase process and the temperature decrease process of the test piece 1. The larger the tanδ ratio or difference, the greater the proportion of viscous components in the thermoplastic resin composition (A), and it is thought that stress relaxation of the thermoplastic resin composition (A) is more likely to proceed in this region.

[0061] As described above, the molded piece 3 of the test piece 1 can prevent the molten thermoplastic resin composition (A) from leaking out of the molded piece 3 during DMA measurement due to the temperature increase of the test piece, and therefore the viscoelastic properties of the thermoplastic resin composition (A) can be measured during the solidification process. Therefore, during the temperature increase process, it is preferable to increase the temperature of the test piece 1 to a temperature higher than the melting point or glass transition temperature of the thermoplastic resin composition (A), whichever is higher.

[0062] (Experimental example) Test pieces of the above embodiment were prepared as prototypes, and DMA measurements were carried out to identify the stress relaxation temperature range of the thermoplastic resin composition (A). A sample of the test piece 1 was prepared according to the test piece preparation method of the above embodiment. First, a 1.5 mm thick flat absorber blank made of thermoplastic resin composition (B2) was prepared, and a through-hole measuring 34 mm in the longitudinal direction (Y direction) and 4 mm in the lateral direction (X direction) was drilled in the thickness direction (Z direction) by machining. The thermoplastic resin composition (B2) used was a polyphenylene sulfide resin composition (Durafide (registered trademark) PPS 0220A9 HD9100 (containing 0.5% by mass of carbon black), melting point: approximately 280°C) manufactured by Polyplastics Co., Ltd. Next, a pair of plates made of the thermoplastic resin composition (A) were placed on the absorbent base plate so as to block the through-holes from both sides, and a pair of metal plates heated to 200°C were used for heat pressing to fill the through-holes with the thermoplastic resin composition (A). The thermoplastic resin composition (A) was a polyacetal resin composition (DURACON (registered trademark) POM M90-44 (unfilled) (melting point: approximately 165°C, glass transition temperature: -60°C)) manufactured by Polyplastics Co., Ltd. After heat pressing, a 12 mm absorbent region was cut out of the absorbent base plate by cutting. Next, two 1 mm-thick plate-shaped transparent materials made of thermoplastic resin composition (B1) were stacked on top of the absorber-designated region, sandwiching the thermoplastic resin composition (A) filled in the through-hole. Laser welding was performed on each side using a laser welding device (manufactured by Fine Devices Co., Ltd., product name "FD-2430") to bond the absorber-designated region and the transparent material in the area surrounding the through-hole and the edge of the absorber-designated region that contacts the through-hole (a 2 mm area away from the hole). The absorber-designated region was then cut to a length of 50 mm in the longitudinal direction (Y direction), producing a sample of Test Piece 1. The total length of both sides of the through-hole in the longitudinal direction (Y direction) of the test piece 1 sample was 16 mm. The thermoplastic resin composition (B1) was a resin composition with the same composition as the polyphenylene sulfide resin composition used for the thermoplastic resin composition (B2), except that it did not contain carbon black. A semiconductor laser was used as the laser light source. Before laser welding, the transmittance of the transmitting material was measured using a spectrophotometer (manufactured by JASCO Corporation, product name "V770") and was found to be 45%.

[0063] Next, the DMA measurement of the prepared sample of test piece 1 was carried out according to the specific method of the above embodiment under the following conditions. The temperature-raising process was a process in which the temperature of the sample of Test Piece 1 was raised from 25°C to 200°C at a heating rate of 3°C / min. The temperature-lowering process was a process in which the temperature of the sample of Test Piece 1 was lowered from 200°C to 25°C at a heating rate of -3°C / min. During this heating and lowering process, the sample of Test Piece 1 was set in a DMA tester and DMA measurement specified in ISO6721 (JIS K7244) was performed. The DMA tester used was an RSA-III manufactured by TA Instruments. The DMA measurement was performed in a three-point bending mode (load strain: 0.02%) and the frequency was fixed at 1 Hz. After the measurement was completed, the sample of Test Piece 1 was visually inspected and no leakage of the thermoplastic resin composition (A) was confirmed.

[0064] Based on the measurement results, Fig. 4 plots the storage modulus E' (E' during the temperature rise process and E' during the temperature fall process) and tan δ (tan δ during the temperature rise process and tan δ during the temperature fall process) measured during the temperature rise process and the temperature fall process.

[0065] Figure 5 shows the storage modulus E' (E' during the temperature rise and E' during the temperature fall) and tan δ (tan δ during the temperature rise and tan δ during the temperature fall) based on the test results for a comparative specimen, which is different from the specimen 1. The comparative specimen had the same structure as the absorber region used for the specimen 1, except that no through holes were drilled in the thickness direction (Z direction). The DMA measurement conditions were the same as those for Figure 4. Figure 6 shows the temperature-lowering process E' and the temperature-lowering process tanδ superimposed on each other from the test results shown in Figures 4 and 5. Sample 1 refers to the comparative sample, and Sample 2 refers to the sample of Test Piece 1.

[0066] As shown in Figure 4, the difference between tan δ during the temperature rise and temperature fall is large in the temperature range of 140°C to 200°C, and in the temperature range below the melting point of polyacetal resin (POM), the tan δ ratio is largest in the temperature range of approximately 150°C to 160°C. The tan δ ratio is the ratio of tan δ during the temperature fall to tan δ during the temperature rise (tan δ during the temperature fall / tan δ during the temperature rise). On the other hand, when polyacetal resin (POM) is not included, the difference between tan δ during the temperature rise and tan δ during the temperature fall is small across the entire temperature range, as shown in Figure 5. From this, it can be seen that the reason for the large difference between tan δ during the temperature rise and tan δ during the temperature fall in Figure 4 is the influence of the inclusion of polyacetal resin (POM) in the sample of test piece 1. As mentioned above, the melting point of polyacetal resin (POM) is approximately 165°C, and in the temperature range below this where the tan δ ratio is largest, polyacetal resin (POM) undergoes a phase transition from a liquid state to a solid state during the temperature drop process, whereas it remains in a nearly solid state during the temperature rise process. Therefore, it is thought that the tan δ ratio became largest in the temperature range of approximately 150 to 160°C, below the melting point of polyacetal resin (POM).

[0067] As shown in Figure 6, the temperature drop process E' of specimen 1 (sample 2) is smaller across the entire temperature range than the comparison sample (sample 1). This is thought to be due to the fact that it is filled with polyacetal resin (POM) (flexural modulus: 2500 MPa), which has a lower elastic modulus than polyphenylene sulfide (PPS) (flexural modulus: 3800 MPa). Furthermore, in the temperature range near the melting point of polyacetal resin (POM) (melting temperature range), tan δ is larger than that of the comparison sample (sample 1), which suggests that the solidification behavior of polyacetal resin (POM) can be detected.

[0068] From the above test results, it is estimated that the temperature range (stress relaxation temperature range) effective for stress relaxation caused by polyacetal resin (POM) contained in the sample of test piece 1, which forms the basis of the test results shown in Figure 4, is approximately 150 to 160°C. In Figure 4, in the temperature range of 140 to 200°C, where a difference occurs between tan δ during the heating process and tan δ during the cooling process, it is thought that stress relaxation of polyacetal resin (POM) can be efficiently achieved by ensuring the time spent on stress relaxation limited to approximately 150 to 160°C, where the tan δ ratio is largest in the temperature range below the melting point of polyacetal resin (POM).

[0069] According to the method of this embodiment, DMA measurement is performed using the test piece 1, and the dynamic viscoelasticity of the test piece 1 measured during the temperature increase and decrease processes is compared, thereby making it possible to evaluate the viscoelastic properties that occur during the solidification process of the thermoplastic resin composition (A). Therefore, it is possible to determine which temperature range is most effective for stress relaxation for the thermoplastic resin composition (A), and for example, the number of steps required for material selection for the thermoplastic resin composition (A) to be used in an insert-molded product with a metal member can be significantly reduced.

[0070] Furthermore, by controlling the cooling temperature and time during injection molding of an insert-molded article in which a metal member and the thermoplastic resin composition (A) are combined, or the annealing conditions of the insert-molded article, based on the stress relaxation temperature range of the thermoplastic resin composition (A) identified by the method of this embodiment, stress relaxation can be efficiently performed and the product life can be extended. Furthermore, when a product is manufactured by welding the thermoplastic resin composition (A), residual stress can be reduced and the product life can be extended by controlling the temperature and time of the cooling step of the thermoplastic resin composition (A).

[0071] In the method of this embodiment, when the test piece 1 of the above embodiment is referred to as test piece A, a method for identifying the stress relaxation temperature range of the thermoplastic resin composition (A) preferably further comprises using test piece B, which is configured similarly to test piece A except that it does not include a molded piece of test piece A, instead of test piece A, performing DMA measurement on test piece B, and comparing the measured dynamic viscoelasticity of test piece A and test piece B. Test piece B is prepared, for example, by the same method as the preparation method of the above embodiment, except that the step of filling with the thermoplastic resin composition (A) is not performed. By performing DMA measurement on such test piece B and comparing the measurement result with that of test piece A, it is possible to consider the effect of voids present in the test piece on the dynamic viscoelasticity.

[0072] (Method for predicting deformation and / or occurrence of fragile parts in molded body) One embodiment is a method for predicting deformation and / or occurrence of a weakened portion in a molded body, comprising the steps of calculating a relaxation modulus and predicting. In the step of calculating the relaxation modulus, the relaxation modulus of the thermoplastic resin composition (A) is calculated based on the storage modulus and loss modulus of the thermoplastic resin composition (A) during the temperature decrease process, which are obtained by the method for identifying the stress relaxation temperature range of the thermoplastic resin composition described above. By using the relaxation modulus, it becomes possible to evaluate or predict the residual stress, etc. during the solidification process of the thermoplastic resin composition (A).

[0073] Specifically, the relaxation modulus of the thermoplastic resin composition (A) is determined by the following procedure. (i) DMA measurements are performed at different temperatures (at least three points including the reference temperature) over a specified range of time or frequency to determine the relationship between temperature and the storage modulus and loss modulus (or tan δ). Hereinafter, the storage modulus and loss modulus (or tan δ) are referred to as "viscoelastic characteristic values." DMA measurements are performed during the temperature drop process.

[0074] (ii) A time-temperature conversion rule is known in which the curves of viscoelastic characteristic values ​​against time or frequency (log-log plotted curves; hereafter referred to as "viscoelastic curves") measured at different temperatures overlap with a viscoelastic curve at a single reference temperature (called a "master curve") by horizontal shift. Therefore, a master curve at the reference temperature is created from the measurement results of (i), and the relationship between the shift factor a(T) and temperature is determined by applying the WLF (Williams-Landel-Ferry) formula in formula (1). In formula (1), T S is the reference temperature, and C1 and C2 are constants. Note that the Arrhenius equation may be applied instead of the WLF equation.

[0075]

number

[0076] Then, the horizontal shift of the viscoelastic curve measured at a temperature T other than the reference temperature is calculated by log(a(T)). SThe constants C1 and C2 in equation (1) are determined (fitted) so that the viscoelastic curve overlaps with the viscoelastic curve measured in (i). Once the constants C1 and C2 are determined, the shift factor at any temperature (any temperature other than the temperature measured in (i)) can be estimated.

[0077] (iii) Finally, the relaxation modulus of the thermoplastic resin composition (A) to be evaluated is determined from the results of (i) and (ii). By determining the relaxation modulus during the solidification process of the thermoplastic resin composition (A) and modeling it using CAE as described below, it becomes possible to evaluate or predict the behavior of the thermoplastic resin composition (A) during the solidification process, etc.

[0078] In the prediction step, the relaxation modulus of the thermoplastic resin composition (A) is modeled, and based on the modeled relaxation modulus of the thermoplastic resin composition (A), deformation and / or occurrence of fragile parts in a molded body (not shown) containing, as a main component, a thermoplastic resin composition (A) having the same composition as the thermoplastic resin composition (A) of the molded piece is predicted when the molded body is molded. For example, equation (2) is determined from the relaxation modulus calculated in (iii) above. Equation (2) is the spring element (elastic modulus E e and E i (i=1~N)) and dashpot element (viscosity coefficient τ i (i=1 to N)) is a series approximation of the relaxation modulus E(t) using a generalized Maxwell model.

[0079]

number

[0080] As an example of CAE analysis, for a structural analysis model of a resin molded product, for example, the CAE analysis software "ANSYS Mechanical" by ANSYS, Inc. is known. By inputting the relaxation modulus modeled by Equation (2) into this analysis software, it becomes possible to accurately predict, for example, the shrinkage behavior and the occurrence of voids (weak parts) during the solidification process of the thermoplastic resin composition (A).

[0081] (Method for predicting residual stress and / or strain in a molded body) One embodiment is a method for predicting residual stress and / or strain in a molded body, comprising the steps of calculating a relaxation modulus and predicting. The step of calculating the relaxation modulus is similar to the step of calculating the relaxation modulus described above. The prediction step involves modeling the relaxation modulus of the thermoplastic resin composition (A) calculated by the above steps (i) to (iii), and predicting the residual stress and / or strain of a molded article when it is molded into a molded article containing, as a main component, a thermoplastic resin composition having the same constitution as the thermoplastic resin composition (A) of the molded piece, based on the modeled relaxation modulus of the thermoplastic resin composition (A). By inputting the relaxation modulus modeled by Equation (2) into the above analysis software, the accuracy of the analysis of the residual stress and strain of the molded article can be improved.

[0082] The test piece and the method for producing the same, the method for identifying the stress relaxation temperature range of a thermoplastic resin composition, the method for predicting deformation and / or the occurrence of brittle parts in a molded body, and the method for predicting residual stress and / or strain in a molded body of the present invention have been described in detail above. However, the present invention is not limited to the above-described embodiments, and various improvements and modifications may be made without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0083] 1 test piece 2 Board material 3 Molded piece 5 Covering material 11 Transparent material 12 Interface 12a Circumferential area 13 Absorbent material 13a hole 20 Absorbent material board 23 Absorbing material area 23a hole 30 Board material

Claims

1. A test piece used in dynamic viscoelasticity measurement to identify the stress relaxation temperature range of a thermoplastic resin composition, a molded piece made of the thermoplastic resin composition; a coating material that coats the molded piece and is made of a thermoplastic resin composition having a melting point or a glass transition temperature higher than the higher of the melting point or the glass transition temperature of the thermoplastic resin composition; The coating material is a transmitting material made of a thermoplastic resin composition that transmits laser light and covers a surface of a portion of the molded piece; an absorbing material made of a thermoplastic resin composition that absorbs laser light, which covers a surface of the molded piece that is different from the surface covered by the transmitting material; A test specimen, wherein the molded piece is sealed by bonding the transmissive material and the absorbent material to each other.

2. A test piece used in dynamic viscoelasticity measurement to identify the stress relaxation temperature range of a thermoplastic resin composition, a molded piece made of the thermoplastic resin composition; a coating material that coats the molded piece and is made of a thermoplastic resin composition having a melting point or a glass transition temperature higher than the higher of the melting point or the glass transition temperature of the thermoplastic resin composition; The coating material is a plate-shaped absorber made of a thermoplastic resin composition that absorbs laser light, the absorber having a hole that penetrates in the plate thickness direction and in which the molded piece is to be placed; a pair of plate-shaped transmitting materials made of a thermoplastic resin composition that transmits laser light, the pair of transmitting materials being placed on top of the absorbing material so as to sandwich the molded piece placed in the hole from both sides in the plate thickness direction of the absorbing material; A test piece, wherein the transmissive material and the absorbent material are bonded to each other in a circumferential region surrounding the hole at each interface between the absorbent material and the pair of transmissive materials.

3. the absorbing material and the transmitting material are plate-like bodies stacked on top of each other, The test piece according to claim 1 or 2, wherein the thickness of the absorbent material in the thickness direction is greater than the thickness of the transmitting material in the thickness direction.

4. 4. The test piece according to claim 3, wherein the thickness of the transmitting material in the plate thickness direction is such that the transmittance of laser light irradiated from the transmitting material side toward the absorbing material is 20% or more.

5. The test piece according to claim 3, wherein the thickness of the test piece in the thickness direction is 5 mm or less.

6. A method for preparing a test piece used in dynamic viscoelasticity measurement performed to identify the stress relaxation temperature range of a thermoplastic resin composition, comprising: a plate-shaped absorber blank made of a thermoplastic resin composition that absorbs laser light and has a melting point or glass transition temperature higher than the higher of the melting point or glass transition temperature of the thermoplastic resin composition, wherein a step of filling the thermoplastic resin composition, which has a specified stress relaxation temperature range, into holes that penetrate the plate thickness direction and are provided in an absorber-intended region of the absorber blank that will become an absorber constituting part of the test piece; a step of stacking a pair of plate-shaped transparent materials made of a thermoplastic resin composition that transmits laser light and has a melting point or glass transition temperature higher than the higher of the melting point or glass transition temperature of the thermoplastic resin composition filled in the holes, on the absorber-intended region so as to sandwich the thermoplastic resin composition filled in the holes from both sides in the plate thickness direction of the absorber-intended region; a step of irradiating a laser beam from the side of the transparent material toward the intended absorbent material area in a peripheral area surrounding the hole at each interface between the intended absorbent material area and the pair of plate-shaped transparent materials to heat and melt the intended absorbent material area, thereby joining the transparent material and the intended absorbent material area.

7. 7. A method for producing a test piece as described in claim 6, wherein in the filling step, a pair of plates made of the thermoplastic resin composition having a specified stress relaxation temperature range are stacked on the absorbent intended area portion so as to block the hole from both sides in the thickness direction of the absorbent base plate, and the plate is pressed against the absorbent intended area portion while heating the plate at a temperature higher than the higher of the melting point or glass transition temperature of the thermoplastic resin composition of the plate and lower than the higher of the melting point or glass transition temperature of the thermoplastic resin composition that absorbs the laser light, thereby filling the hole with the thermoplastic resin composition having a specified stress relaxation temperature range.

8. a temperature-raising process in which the test piece according to claim 1 or 2 is cooled to a temperature below the glass transition temperature of the thermoplastic resin composition of the molded piece, and then the temperature is changed so as to be successively increased to a temperature below the higher of the melting point or the glass transition temperature of the thermoplastic resin composition of the transmitting material and the lower of the higher of the melting point or the glass transition temperature of the thermoplastic resin composition of the absorbing material, and a temperature-reducing process in which the test piece is cooled to a temperature below the glass transition temperature of the thermoplastic resin composition of the molded piece, and dynamic viscoelasticity measurement of the test piece is performed; The method for identifying a stress relaxation temperature range of a thermoplastic resin composition includes identifying the stress relaxation temperature range of the thermoplastic resin composition of the molded specimen based on the difference in dynamic viscoelasticity of the test specimen measured during the temperature increase process and the temperature decrease process.

9. When the test piece is referred to as test piece A, the method further comprises: A test piece B having the same structure as the test piece A except that the test piece A does not have a molded piece of the test piece A is used instead of the test piece A, and the dynamic viscoelasticity of the test piece B is measured. The method of claim 8 , wherein the measured dynamic viscoelastic properties of the test piece A and the test piece B are compared.

10. Calculating the relaxation modulus of the thermoplastic resin composition of the molded piece based on the storage modulus and loss modulus of the thermoplastic resin composition of the molded piece during the temperature decrease process obtained by the method according to claim 8; a step of modeling the relaxation modulus of the thermoplastic resin composition of the molded piece, and predicting, based on the modeled relaxation modulus of the thermoplastic resin composition, the deformation and / or occurrence of a fragile part of the molded piece when the molded piece is molded, the molded piece containing, as a main component, a thermoplastic resin composition having the same constitution as the thermoplastic resin composition of the molded piece.

11. Calculating the relaxation modulus of the thermoplastic resin composition of the molded piece based on the storage modulus and loss modulus of the thermoplastic resin composition of the molded piece during the temperature decrease process obtained by the method according to claim 8; a step of modeling the relaxation modulus of the thermoplastic resin composition of the molded piece, and predicting the residual stress and / or strain of the molded piece when the molded piece is molded, the molded piece containing, as a main component, a thermoplastic resin composition having the same constitution as the thermoplastic resin composition of the molded piece, based on the modeled relaxation modulus of the thermoplastic resin composition.

Images