JP2018151205A - Evaluation method of friction performance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for accurately evaluating a friction performance of the vulcanized rubber.SOLUTION: First, a test piece 14 having a first specimen 2 having a first measurement surface 6, a second specimen 4 having a second measurement surface 8, a first thin film 10, a second thin film 12, and a test surface 16 is prepared. The first specimen 2 and the second specimen 4 are made of the vulcanized rubbers of the same compositions. The first thin film 10 and the second thin film 12 are characterized in that the refraction index or the transparency are changed by the load. Next, the first measurement surface 6 is treated for the friction. The first thin film 10 is arranged and loaded between the first measurement surface 6 and the test surface 16 after being treated for the friction. The second thin film 12 is arranged and loaded between the second measurement surface 8 and the test surface 16. Subsequently, the real contact surface S1 per unit area of the first measurement surface 6 and the real contact surface S2 per unit area of the second measurement surface 8 are comparatively calculated from the areas of the change areas of the first thin film 10 and the second thin film 12. Finally, the friction performance of the vulcanized rubber is evaluated as the index of real contact surfaces S1 and S2.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a method for evaluating the friction performance of vulcanized rubber.

  In recent years, vulcanized rubber has been used for various purposes. For example, vulcanized rubber is used for tire treads. When a vehicle equipped with tires travels on the road surface, a tread made of vulcanized rubber comes into contact with the road surface. The friction performance of the vulcanized rubber against the road surface affects the grip performance of the tire. In tire development, there is a need for a method for accurately and simply evaluating the friction performance of vulcanized rubber.

  Regarding the friction performance of vulcanized rubber, conventionally, the contribution of hysteresis friction and adhesive friction is known. Hysteresis friction is defined as the energy loss that occurs with periodic deformation and recovery of vulcanized rubber. Adhesive friction is friction generated by adhesion and shear between vulcanized rubber and a road surface.

  Until now, it has been considered that the contribution of hysteresis friction to the friction performance of vulcanized rubber on the road surface on which the vehicle travels (hereinafter referred to as the actual road surface) is particularly large. As a method for evaluating the contribution of this hysteresis friction, for example, a method using the loss tangent (tan δ) of vulcanized rubber as an index has been proposed. However, the evaluation result of the friction performance by this loss tangent (tan δ) does not necessarily correlate with the evaluation result on the actual road surface. The contribution of adhesive friction to the friction performance of vulcanized rubber on the actual road surface is considered to be so large that it cannot be ignored in some cases.

  Both hysteresis friction and adhesive friction are caused by contact between the vulcanized rubber and the road surface. The contact state between the vulcanized rubber and the road surface affects the hysteresis friction and the adhesion friction. Usually, there are many micron-sized irregularities on the actual road surface. On the micro scale, a large number of fine protrusions on the actual road surface actually come into contact with the vulcanized rubber and affect hysteresis friction and adhesive friction. In order to evaluate the friction performance of vulcanized rubber, it is important to grasp the contact state on the micro scale.

  Non-Patent Document 1 below discloses a method for examining the contact state between a transparent rubber flat plate and a glass hemisphere using an optical microscope. Non-Patent Document 2 below discloses a method of observing a true contact portion between transparent objects using a transmission optical system device, and a true contact portion between objects at least one of which is transparent using a reflection optical system device. A method of observing is disclosed.

Journal of Japan Rubber Association Vol. 88, No. 2, p. 43 (2015) The Japan Rubber Association Vol.85, No.10, p.313 (2012)

  The vulcanized rubber may be mixed with fillers such as carbon black, silica, aluminum hydroxide, calcium carbonate, and talc. As exemplified by the tire tread rubber, there are many vulcanized rubbers that are put to practical use due to the blended filler. Also, the road surface on which the tire made of vulcanized rubber travels is usually opaque. It is difficult to accurately grasp the contact state between the opaque vulcanized rubber and the opaque actual road surface by the methods disclosed in Non-Patent Documents 1 and 2.

  Further, the surface state of the vulcanized rubber may fluctuate due to friction with a road surface having a large number of fine irregularities. For example, in a running tire, an adhesive substance exudes from the inside of the tread rubber and adheres to the tread surface. The sticky substance on the tire surface affects the friction performance. The fluctuation of the surface condition of the vulcanized rubber is considered to be one of the causes of the discrepancy with the evaluation result on the actual road surface, but the evaluation that can reflect the influence of the fluctuation of the surface condition on the friction performance evaluation result of the vulcanized rubber A method has not yet been proposed.

  An object of the present invention is to provide an evaluation method capable of accurately evaluating the friction performance of vulcanized rubber.

Friction performance evaluation method according to the present invention,
(1) A first specimen comprising a vulcanized rubber and having a first measurement surface with a known area, and a second measurement surface comprising a vulcanized rubber having the same composition as the first specimen and having a known area. Preparation for preparing a second specimen having a first thin film and a second thin film made of a resin composition having a characteristic that its refractive index or transparency changes depending on a load, and a specimen having a test surface on its upper surface Process,
(2) A treatment process for friction-treating the first measurement surface,
(3) A first surface that is loaded on the first thin film by bringing one surface of the first thin film into contact with the test surface and pressing the first measurement surface subjected to the friction treatment against the other surface of the first thin film. Loading process,
(4) a second loading step of loading the second thin film by bringing one surface of the second thin film into contact with the test surface and pressing the second measurement surface against the other surface of the second thin film;
(5) Collecting the loaded first thin film and measuring the area of the region where the refractive index or transparency of the first thin film has changed, so that the actual contact between the first measurement surface subjected to the friction treatment and the test surface A first measurement step for calculating the area and (6) collecting the loaded second thin film and measuring the area of the region where the refractive index or transparency of the second thin film has changed, so that the first non-frictional process is performed. A second measurement step of calculating an actual contact area between the two measurement surfaces and the test surface; When the actual contact area per unit area of the first measurement surface subjected to the friction treatment is S1 and the actual contact area per unit area of the second measurement surface not subjected to the friction treatment is S2, The friction performance of the vulcanized rubber is evaluated using the contact areas S1 and S2 as indices. Preferably, this index is a ratio (S1 / S2) of the actual contact area S1 to the actual contact area S2.

  Preferably, the base resin of this resin composition is a polycarbonate resin. The 1st thin film and 2nd thin film which consist of this resin composition have the characteristic of whitening with a load. In the first measurement process and the second measurement process, the area of this whitened area is measured to calculate the actual contact area.

  Preferably, an adhesive substance is present on the first measurement surface subjected to the friction treatment.

  Preferably, the thickness of the first thin film is not less than 0.5 μm and not more than 2.0 μm. Preferably, the thickness of the second thin film is not less than 0.5 μm and not more than 2.0 μm. Preferably, the thickness of the first thin film and the thickness of the second thin film are the same.

  In the first loading step, the first thin film is preferably loaded with a pressure of 0.1 MPa or more and 1.0 MPa or less. In the second loading step, the second thin film is preferably loaded with a pressure of 0.1 MPa or more and 1.0 MPa or less. Preferably, the first thin film and the second thin film are loaded with the same pressure.

  Preferably, the test surface is a simulated road surface having a large number of fine irregularities on the surface.

  The evaluation method according to the present invention includes a step of accurately calculating the actual contact area between the vulcanized rubber and the road surface. In this evaluation method, the friction performance of the vulcanized rubber is evaluated using the ratio of the actual contact area of the vulcanized rubber subjected to the friction treatment to the actual contact area of the vulcanized rubber not subjected to the friction treatment as an index. The evaluation result obtained by this evaluation method correlates with the evaluation result on the actual road surface with high accuracy.

FIG. 1 is a flowchart of an evaluation method according to an embodiment of the present invention. FIG. 2 is a schematic view showing the processing steps of FIG. FIG. 3 is a schematic diagram illustrating the first loading process and the second loading process of FIG. FIG. 4 is a captured image of the first thin film obtained in the first measurement step of FIG. FIG. 5 is a photographed image of the second thin film obtained in the second measurement step of FIG.

  Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings. However, the present invention is not construed as being limited based on this description.

  FIG. 1 is a flowchart showing an evaluation method according to an embodiment of the present invention. This evaluation method includes a preparation process, a processing process, a first load process, a second load process, a first measurement process, and a second measurement process. In this evaluation method, after the preparatory process, through the processing process, the line A going from the first load process to the first measurement process, and after the preparatory process, from the second load process to the second measurement process without passing through the processing process. It consists of a line B that goes forward.

  The preparatory step is made of a vulcanized rubber, a first specimen having a first measurement surface with a known area, and a vulcanized rubber having the same composition as the first specimen, and a second measurement having a known area. Preparing a second specimen having a surface, a first thin film and a second thin film made of a resin composition having a characteristic that the refractive index or transparency changes depending on a load, and a specimen having a test surface on its upper surface It is a process. In this embodiment, the area of the first measurement surface is A1. The area of the second measurement surface is A2. The first specimen, the first thin film, and the specimen are provided on line A. The second specimen, the second thin film, and the specimen are provided on line B.

  In line A, first, the first measurement surface of the first specimen is subjected to friction processing in the processing step. FIG. 2 is a schematic diagram showing the processing steps of this embodiment. In detail, it is the schematic for demonstrating the process of friction-treating the 1st measurement surface 6 of the 1st specimen 2 using a friction test apparatus (not shown). In FIG. 2, the vertical direction on the paper is the vertical direction, and the horizontal direction on the paper is the horizontal direction.

  In this embodiment, first, a portable friction tester (PFT device) manufactured by HENTSCHEL is prepared as a friction test device including the friction surface 18. Next, the first specimen 2 is placed on the friction surface 18, and the friction surface 18 is brought into contact with the first measurement surface 6 of the first specimen 2. Subsequently, the first measurement surface 6 is subjected to friction treatment by applying a load to the first specimen 2 and moving the first measurement surface 6 against the friction surface 18. An arrow F1 shown in FIG. 2 is a direction in which the load is applied to the first specimen 2, and an arrow D is a moving direction of the first specimen 2.

  The first loading process is a process in which a first thin film is placed between the test surface of the test body and the first measurement surface 6 subjected to the friction treatment, and the first thin film is loaded. Hereinafter, the first loading process of this embodiment will be described using the schematic diagram shown in FIG. In FIG. 3, the vertical direction on the paper is the vertical direction, and the horizontal direction on the paper is the horizontal direction.

  In this embodiment, a test body 14 having a test surface 16 having a large number of fine irregularities on its surface is prepared. Next, the first thin film 10 is placed on the test surface 16. As shown in the drawing, on one surface of the first thin film 10 placed on the test surface 16, a region that contacts the test surface 16 and a region that does not contact are formed.

  Subsequently, the first specimen 2 is placed on the first thin film 10, and the first measurement surface 6 subjected to the friction treatment is brought into contact with the other surface of the first thin film 10. Thereafter, the load is applied to the first thin film 10 by applying a load in the direction indicated by the arrow F <b> 2 in FIG. 3 and pressing the friction-treated first measurement surface 6 against the first thin film 10. In this embodiment, the first thin film 10 is loaded mainly in the contact area with the test surface 16. As described above, the first thin film 10 is made of a resin composition having a characteristic that the refractive index or transparency changes depending on the load. In this embodiment, mainly the refractive index or transparency of the contact region between the first thin film 10 and the test surface 16 changes depending on the load.

  In this evaluation method, the contact area between the first thin film 10 and the test surface 16 corresponds to the contact area between the first measurement surface 6 and the test surface 16 subjected to friction processing (hereinafter referred to as an actual contact portion). That is, in the first thin film 10 that has undergone the first loading step, the region where the refractive index or transparency has changed due to the load (hereinafter, the changed region) is the actual contact portion between the first measurement surface 6 and the test surface 16 that have been subjected to the friction treatment. It is. In other words, the first loading step is to load the first thin film 10 at the actual contact portion between the friction-treated first measurement surface 6 and the test surface 16, and in the region corresponding to the actual contact portion. This is a step of changing the refractive index or transparency.

  The first measurement step measures the area of the first thin film 10 where the refractive index or transparency has changed due to the load, and calculates the actual contact area B1 between the test surface 16 and the friction-treated first measurement surface 6. It is a process to do. In this embodiment, the area of the change region is measured by image analysis using an optical microscope.

  FIG. 4 is a photographed image by the microscope of the first thin film 10 that has undergone the first loading step. A white part is an area | region where the refractive index or transparency changed with the load, and is an area | region corresponding to the actual contact part 20 of the test surface 16 and the 1st measurement surface 6 friction-treated. After binarizing the image of FIG. 4, the area of the white portion is measured as the actual contact area B1 between the test surface 16 and the first measurement surface 6 subjected to the friction processing. Subsequently, the actual contact area B1 is divided by the area A1 of the first measurement surface 6, and the actual contact area S1 per unit area of the friction-treated first measurement surface 6 with respect to the test surface 16 (= B1 / A1) is calculated.

  In line B, no processing step is performed. In this embodiment, in FIG. 3, the first specimen 2 is changed to the second specimen 4 and the first thin film 10 is changed to the second thin film 12. Perform the loading process.

  Specifically, first, the second thin film 12 is placed on the test surface 16, and a region in contact with the test surface 16 is formed on one surface of the second thin film 12. Subsequently, the second specimen 4 is placed on the second thin film 12, and the second measurement surface 8 that is not subjected to friction treatment is brought into contact with the other surface of the second thin film 12. Thereafter, a load is applied in the direction indicated by an arrow F2 in FIG. 3, and the second measurement surface 8 not subjected to the friction treatment is pressed against the second thin film 12. Thereby, the second thin film 12 is loaded mainly in the contact area with the test surface 16. In this embodiment, mainly the refractive index or transparency of the contact area between the second thin film 12 and the test surface 16 changes depending on the load.

  In this evaluation method, the contact area between the second thin film 12 and the test surface 16 corresponds to the actual contact portion between the second measurement surface 8 and the test surface 16 that is not subjected to friction treatment. That is, the change area in the second thin film 12 that has undergone the second loading step is an actual contact portion between the second measurement surface 8 and the test surface 16 that has not been subjected to the friction treatment. In other words, the second loading step is a region corresponding to the actual contact portion by loading the second thin film 12 at the actual contact portion between the second measurement surface 8 that is not subjected to the friction treatment and the test surface 16. This is a step of changing the refractive index or the transparency.

  The second measurement step is a step of measuring the area of the changed region of the second thin film 12 and calculating the actual contact area B2 between the test surface 16 and the second measurement surface 8 that has not been subjected to the friction treatment.

  FIG. 5 is a photographed image by the microscope of the second thin film 12 that has undergone the second loading step. A white part is an area | region where the refractive index or transparency changed with the load, and is an area | region corresponding to the actual contact part 20 of the test surface 16 and the 2nd measurement surface 8 which is not friction-processed. After binarizing the image of FIG. 5, the area of the white portion is measured as the actual contact area B2 between the test surface 16 and the second measurement surface 8 that has not been subjected to friction processing. Subsequently, the actual contact area B2 is divided by the area A2 of the second measurement surface 8, and the actual contact area S2 (= B2) per unit area of the second measurement surface 8 that is not subjected to the friction treatment with respect to the test surface 16. / A2) is calculated.

  In this embodiment, the ratio (S1 / S2) of the actual contact area S1 per unit area of the first measurement surface 6 subjected to friction processing to the actual contact area S2 per unit area of the second measurement surface 8 not subjected to friction processing. ) As an index, the friction performance of the vulcanized rubber forming the first specimen 2 and the second specimen 4 is evaluated. The evaluation result obtained using this ratio (S1 / S2) as an index correlates with high accuracy with the friction performance of the vulcanized rubber on the actual road surface.

  In this evaluation method, the method for preparing the first specimen 2 and the second specimen 4 made of vulcanized rubber is not particularly limited. For example, according to a predetermined composition, base rubber and various additives are put into an open roll, a Banbury mixer, etc., and kneaded to make an unvulcanized rubber, and the unvulcanized rubber is heated in a mold having a predetermined shape. The first specimen 2 and the second specimen 4 may be prepared by applying pressure to produce a sheet of vulcanized rubber and cutting the vulcanized rubber sheet into a predetermined shape. In addition, after extruding unvulcanized rubber into a shape such as a tread, a tire is manufactured by heating and pressing in a vulcanizer together with other tire members, and the tire forming the tread surface is added. The first specimen 2 and the second specimen 4 may be prepared by cutting the vulcanized rubber into a predetermined shape. It is also possible to prepare vulcanized rubber collected from a tread of a commercially available tire as the first specimen 2 and the second specimen 4.

  In this evaluation method, the first specimen 2 and the second specimen 4 are made of vulcanized rubber having the same composition. The types of base rubber and various additives that are blended in the vulcanized rubber forming the first specimen 2 and the second specimen 4 are not particularly limited. For example, natural rubber, polybutadiene, styrene-butadiene copolymer, polyisoprene, ethylene-propylene-diene terpolymer, polychloroprene, acrylonitrile-butadiene copolymer, and isobutylene-isoprene copolymer are used as the base rubber. Can be mentioned. Additives include fillers, stearic acid, oil, wax, zinc oxide, plasticizers, sulfur, vulcanization accelerators and anti-aging agents. Specific examples of the vulcanized rubber composition include a composition for a tire tread rubber.

  Preferably, the shape of the first specimen 2 and the second specimen 4 is a plate shape or a sheet shape having a predetermined thickness. Preferably, the first measurement surface 6 included in the first specimen 2 and the second measurement surface 8 included in the second specimen 4 are substantially flat. When the first specimen 2 is plate-shaped or sheet-shaped, the upper surface or the lower surface is the first measurement surface 6. When the second specimen 4 is plate-shaped or sheet-shaped, the upper surface or the lower surface is the second measurement surface 8. In this evaluation method, there is no particular limitation on the planar view shape and the size of the first specimen 2 and the second specimen 4. From the viewpoint of accuracy improvement and work efficiency, it is preferable that the planar view shape of the first specimen 2 and the planar view shape of the second specimen 4 are substantially the same. From the same viewpoint, it is preferable that the area of the first measurement surface 6 and the area of the second measurement surface 8 are substantially the same.

  From the viewpoint of accuracy improvement and workability, the thickness of the first specimen 2 is preferably 5 mm or more, and more preferably 6 mm or more. The thickness of the first specimen 2 is preferably 20 mm or less. From the same viewpoint, the thickness of the second specimen 4 is preferably 5 mm or more, and more preferably 6 mm or more. The thickness of the second specimen 4 is preferably 20 mm or less. Preferably, the thickness of the first specimen 2 and the thickness of the second specimen 4 are the same. In addition, about the 1st specimen 2, after passing through a process process, it is also possible to adjust the shape and thickness by cutting etc.

  The kind of the resin composition which makes the 1st thin film 10 and the 2nd thin film 12 is not specifically limited, The resin composition which has the characteristic in which the refractive index or transparency changes with a load is selected suitably, and is used. As the base resin of this resin composition, for example, polyester resin such as polycarbonate resin, polyethylene terephthalate, polybutylene terephthalate, polyethylene resin, polypropylene resin, polystyrene, styrene resin such as poly (acrylonitrile-styrene) copolymer, Examples thereof include acrylic resins such as polymethyl methacrylate. Two or more kinds may be used in combination.

  A preferred base resin is a polycarbonate resin. The 1st thin film 10 and the 2nd thin film 12 which consist of a resin composition whose base resin is polycarbonate resin have high transparency, and are whitened with a load. As long as the object of the present invention is achieved, the base resin of the resin composition forming the first thin film 10 and the second thin film 12 may contain a polycarbonate resin and another resin. A resin composition in which the main component of the base resin is a polycarbonate resin is preferable. As long as the effects of the present invention are not inhibited, the resin composition may further contain additives such as an antioxidant, a surfactant, and an antistatic agent. The resin composition forming the first thin film 10 and the resin composition forming the second thin film 12 are preferably the same.

  In this evaluation method, the thicknesses of the first thin film 10 and the second thin film 12 can be appropriately selected depending on the type of resin composition and its characteristics. Preferably, the thicknesses of the first thin film 10 and the second thin film 12 are set so that the refractive index or transparency of at least a part of the region changes when loaded with a pressure of 0.1 MPa or more and 1.0 MPa or less. It is preferable that the thickness of the 1st thin film 10 and the thickness of the 2nd thin film 12 are the same.

  When the base resin of the resin composition forming the first thin film 10 is a polycarbonate resin, the thickness of the first thin film 10 is preferably 2.0 μm or less and more preferably 1.8 μm or less from the viewpoint of whitening due to load. From the viewpoint of durability, a preferable thickness of the first thin film 10 is 0.5 μm or more. Similarly, when the base resin of the resin composition forming the second thin film 12 is a polycarbonate resin, the thickness of the second thin film 12 is preferably 2.0 μm or less, and preferably 1.8 μm or less from the viewpoint of whitening due to load. More preferred. From the viewpoint of durability, the preferable thickness of the second thin film 12 is 0.5 μm or more.

  About the 1st thin film 10 and the 2nd thin film 12, the planar view shape and magnitude | size are not specifically limited. Preferably, the first thin film 10 and the second thin film 12 have the same shape in plan view. Preferably, the first thin film 10 is larger than the first measurement surface 6 and the second thin film 12 is larger than the second measurement surface 8.

  In this evaluation method, the method for preparing the first thin film 10 and the second thin film 12 is not particularly limited, and depending on the type and physical properties of the selected resin composition, a solution casting method (casting method), a melt extrusion molding method. A hot press method or the like is appropriately selected and used. For example, when the base resin of the resin composition is a polycarbonate resin, a solution casting method is suitable as a method for forming the first thin film 10 and the second thin film 12 with high transparency and uniform thickness.

  In this evaluation method, the shape and size of the test body 14 are not particularly limited. Preferably, the test body 14 includes a substantially flat test surface 16 on the upper surface thereof. Preferably, the test surface 16 is a pseudo road surface having a large number of fine irregularities on the surface. Examples of the material of the simulated road surface include various asphalts, concrete, and a grindstone. The test surface 16 may be an actual road surface.

  The friction treatment conditions in the treatment step are not particularly limited, and are appropriately set according to the type of vulcanized rubber forming the first specimen 2, the shape of the first specimen 2, and the like. For example, when the above-described friction test apparatus is used, the friction surface 18 may be set in a wet state or a dry state. The first measurement surface 6 may be friction-treated by moving the first specimen 2 a plurality of times while pressing the first measurement surface 6 against the friction surface 18. As long as the object of the present invention is achieved, the first measurement surface 6 may be subjected to friction treatment by a method other than the friction test apparatus.

  Preferably, an adhesive substance is present on the surface of the first measurement surface 6 that has undergone the processing step. Although the details of this adhesive substance are not clear, some or various derivatives of various additives contained in the vulcanized rubber constituting the first specimen 2 are leached and accumulated on the first measurement surface 6 by friction treatment. Presumed to be a mixture. In this evaluation method, preferably, the first specimen 2 in a state where an adhesive substance is attached to the surface of the first measurement surface 6 is subjected to the first loading step.

  In the first loading process and the second loading process, the method for loading the first thin film 10 and the second thin film 12 is not particularly limited. For convenience, a method of placing a weight having a predetermined mass on the upper surface of the first specimen 2 or the second specimen 4 for a certain period of time is used. A method of applying a load by a pressure press machine or the like appropriately selected can also be used.

  Load conditions in the first loading process and the second loading process are appropriately set according to the type of resin composition forming the first thin film 10 and the second thin film 12. A load condition capable of forming a change region in at least a part of the first thin film 10 and at least a part of the second thin film 12 is preferable. It is preferable to load the first thin film 10 and the second thin film 12 under the same conditions.

  When the base resin of the resin composition forming the first thin film 10 is a polycarbonate resin, the first thin film 10 is preferably loaded with a pressure of 0.1 MPa or more, more preferably 0.2 MPa or more. Thereby, at least a part of the first thin film 10 is whitened to a detectable level. From the viewpoint of preventing deformation or breakage of the first thin film 10, it is preferable to apply a load at a pressure of 1.0 MPa or less.

  When the base resin of the resin composition forming the second thin film 12 is a polycarbonate resin, the second thin film 12 is preferably loaded with a pressure of 0.1 MPa or more, more preferably 0.2 MPa or more. Thereby, at least a part of the second thin film 12 is whitened to a detectable level. From the viewpoint of preventing deformation or breakage of the second thin film 12, it is preferable to apply a load at a pressure of 1.0 MPa or less.

  In the first measurement process and the second measurement process, the method for measuring the area of the change region is not particularly limited. Depending on the type and physical properties of the resin composition forming the first thin film 10 and the second thin film 12, image analysis using an optical microscope, absorbance measurement, transmittance measurement, turbidity measurement, refractive index measurement, whiteness measurement, optical density Measurement or the like is appropriately selected and used. When the base resin of the resin composition forming the first thin film 10 and the second thin film 12 is a polycarbonate resin, an image analysis method using an optical microscope is preferably used.

  In the evaluation method according to the present invention, the microscale contact state between the test surface 16 and the friction-treated first measurement surface 6 is grasped through the processing step, the first load step, and the first measurement step. be able to. In this evaluation method, the contact state on the microscale between the test surface 16 and the second measurement surface 8 that is not subjected to the friction treatment can be grasped by passing through the second load step and the second measurement step.

  According to the evaluation method of the present invention, the actual contact area S1 per unit area of the first measurement surface 6 subjected to the friction treatment with respect to the test surface 16 and the actual per unit area of the second measurement surface 8 not subjected to the friction treatment. By using the contact area S2 as an index, preferably, by using the ratio (S1 / S2) of the actual contact area S1 per unit area and the actual contact area S2 per unit area as an index, An evaluation result reflecting the contact state on the microscale with the test surface is obtained. Furthermore, the evaluation result can also reflect changes in the surface state of the vulcanized rubber due to friction. The evaluation result of the friction performance of the vulcanized rubber obtained by this evaluation method correlates well with the evaluation result on the actual road surface.

  Hereinafter, the effects of the present invention will be clarified by examples. However, the present invention should not be construed in a limited manner based on the description of the examples.

[Example 1]
The base rubber (styrene butadiene rubber, “Toughden 4850” manufactured by Asahi Kasei Co., Ltd.), carbon black (“Niteron # 55S” manufactured by Nippon Kayaku Co., Ltd.), silica (“Ultrazil VN3” manufactured by Degussa) ), Anti-aging agent 1 (“NOCRACK 6C” manufactured by Ouchi Shinsei Chemical Co., Ltd.), anti-aging agent 2 (“NOCRACK 224” manufactured by Flexis Co.), stearic acid (“paulownia” manufactured by NOF Corporation), oxidation Zinc (manufactured by Mitsui Kinzoku Mining Co., Ltd.), coupling agent (“Si69” manufactured by Degussa), wax (“Sannok N” manufactured by Ouchi Shinsei Chemical) and oil (“Process X-260” manufactured by Japan Energy) ) And kneaded at 150 ° C. for 5 minutes. In the obtained kneaded material, sulfur (powder sulfur manufactured by Tsurumi Chemical Co., Ltd.), vulcanization accelerator DPG (Noxeller D manufactured by Ouchi Shinsei Chemical Co., Ltd.) and vulcanization accelerator CZ (Soxinol CZ manufactured by Sumitomo Chemical Co., Ltd.) Was added and kneaded for 3 minutes at 100 ° C. using an open roll to obtain an unvulcanized rubber. The obtained unvulcanized rubber was put into a mold and press vulcanized at 170 ° C. for 12 minutes to prepare a rubber sheet made of the vulcanized rubber of Formulation A.

  Vulcanized rubber sheets of Formulation B and Formulation C were prepared in the same manner except that a predetermined amount of aluminum hydroxide (“Hijilite H-43” manufactured by Showa Denko KK) was added. The amount of aluminum hydroxide added to 100 parts by mass of the base rubber is shown in Table 1 below.

  First, a vulcanized rubber sheet of compound A was cut to obtain a first specimen having a width of 25 mm × a length of 33 mm × a thickness of 8 mm, and a second specimen having a width of 20 mm × length of 30 mm × thickness of 6 mm. Got ready.

  Next, a polycarbonate resin (manufactured by ACROS ORGANICS) was dissolved in chloroform (manufactured by Wako Pure Chemicals, reagent special grade) to obtain a casting solution having a concentration of 5% by mass. After dripping 5 ml of this cast solution on a glass plate and applying it uniformly with a spin coater (rotation speed 2000 rpm, rotation time 30 seconds), drying at 60 ° C. for 2 hours, and repeatedly peeling from the glass plate, A first thin film and a second thin film having a thickness of 30 mm and a thickness of 1 μm were prepared.

The bottom surface of the prepared first specimen was subjected to friction treatment using a portable friction tester (PFT apparatus) manufactured by HENTSCHEL. The friction processing conditions are as follows.
Road surface condition: wet asphalt road surface Treatment temperature: 23 ° C
Moving speed: 2000 mm / sec. Number of repetitions: 8 times A small amount of adhesive substance adhering to the friction-treated bottom surface was visually confirmed. Thereafter, the first specimen was cut so as to leave a friction-treated bottom surface, and processed into a width of 20 mm, a length of 30 mm, and a thickness of 6 mm.

  Subsequently, a dry asphalt road surface (temperature 23 ° C.) was prepared, and a first thin film was placed on the road surface. The first specimen was placed on the first thin film, and the bottom surface of the first specimen subjected to the friction treatment was brought into contact with the first thin film. Thereafter, a weight of 12 kg was left on the first specimen for 60 seconds, and the first thin film was loaded with a pressure of 0.2 MPa.

After loading, the first thin film was collected and photographed with a microscope to obtain the image of FIG. This image was binarized using image analysis software attached to the microscope, and the area of the white region was measured. The actual contact area S1 per unit area was calculated by dividing the area of the white region by the bottom surface area 600 mm ² (20 mm × 30 mm) of the first specimen.

The second thin film was placed on the above-mentioned asphalt road surface, the second specimen was placed on the second thin film, and the bottom surface of the second specimen and the second thin film were brought into contact with each other. Thereafter, a weight of 12 kg was allowed to stand for 60 seconds on the second specimen, and the second thin film was loaded with a pressure of 0.2 MPa. An image obtained by photographing the second thin film collected after loading with a microscope is shown in FIG. The area of the white region of this image was measured and divided by the area of the bottom surface of the second specimen 600 mm ² (20 mm × 30 mm) to calculate the actual contact area S2 per unit area.

  The actual contact areas S1 and S2 per unit area were calculated in the same manner except that the vulcanized rubber sheets of Formulation B and Formulation C were used instead of the vulcanized rubber sheet of Formulation A, respectively.

  Thereafter, the ratio of the actual contact area S1 to the actual contact area S2 (S1 / S2) was calculated for each of the vulcanized rubbers of Formulation AC, and the friction performance of the vulcanized rubber was evaluated. The index when the ratio (S1 / S2) obtained for the vulcanized rubber of Formulation A is 100 is shown in Table 1 below as INDEX (S1 / S2). The higher the number, the higher the evaluation.

[Comparative Example 1]
In Comparative Example 1, the friction performance was evaluated using the loss tangent (tan δ) of the vulcanized rubber as an index. First, each vulcanized rubber was sampled from the vulcanized rubber sheet of Formulation A-C prepared in Example 1, and a test piece was prepared according to JIS K6394. Then, using a viscoelastic spectrometer (manufactured by Iwamoto Seisakusho), viscoelasticity measurement was performed under conditions of a temperature of 0 ° C., an initial strain of 10%, a dynamic strain of 0.5%, and a frequency of 10 Hz. The loss tangent (tan δ) of the vulcanized rubber was obtained. The index when the loss tangent (tan δ) of the vulcanized rubber of Formulation A is set to 100 is shown in Table 1 below as INDEX (tan δ). The higher the number, the higher the evaluation.

[Comparative Example 2]
In Comparative Example 2, the friction performance of the vulcanized rubber was evaluated using the actual contact area S2 per unit area calculated in Example 1 as an index. The index when the actual contact area S2 obtained for the vulcanized rubber of Formulation A is taken as 100 is shown in Table 1 below as INDEX (S2). The higher the number, the higher the evaluation.

[Reference example]
A trial tire A (size: 195 / 65R15) in which the vulcanized rubber of the blend A described in Example 1 was a tread rubber was produced. After the prototype tire A was incorporated into a regular rim, it was filled with air at an internal pressure of 180 kPa and mounted on a test vehicle. The test vehicle was run at a speed of 80 km / h on a wet asphalt road surface, and the maximum coefficient of friction μ from braking to stopping was measured. Similarly, a trial tire B in which the vulcanized rubber of the blend B is a tread rubber and a trial tire C in which the vulcanized rubber of the blend C is a tread rubber are manufactured, and the maximum friction coefficient μ of each trial tire is measured. . The index when the measured value of the prototype tire A is 100 is shown in Table 1 below as INDEX (μ).

  As shown in Table 1, the evaluation result of Example 1 correlates with the evaluation result of the reference example. The evaluation results of Comparative Examples 1 and 2 are not correlated with the evaluation results of the reference examples. From this evaluation result, the superiority of the present invention is clear.

  The method described above can be applied to the evaluation of the friction performance of various polymer materials.

2 ... 1st specimen 4 ... 2nd specimen 6 ... 1st measurement surface 8 ... 2nd measurement surface 10 ... 1st thin film 12 ... 2nd thin film 14 ... Specimen 16 ... Test surface 18 ... Friction surface 20 ... Real contact part

Claims (7)

A first specimen made of vulcanized rubber and having a first measurement surface with a known area and a vulcanized rubber having the same composition as the first specimen, and having a second measurement surface with a known area. A preparatory step of preparing two specimens, a first thin film and a second thin film made of a resin composition having a characteristic that the refractive index or transparency changes depending on a load, and a test body provided with a test surface on the upper surface;
A treatment process for friction-treating the first measurement surface;
A first surface of the first thin film is brought into contact with the test surface, and the first measurement surface subjected to the friction treatment is pressed against the other surface of the first thin film to load the first thin film. One load process,
A second loading step of loading the second thin film by bringing one surface of the second thin film into contact with the test surface and pressing the second measurement surface against the other surface of the second thin film; ,
Collecting the loaded first thin film and measuring the area of the first thin film where the refractive index or transparency of the first thin film is measured, thereby making an actual contact between the first measurement surface subjected to the friction treatment and the test surface. A first measuring step for calculating an area;
By collecting the loaded second thin film and measuring the area of the region where the refractive index or transparency of the second thin film has changed, the actual measurement between the second measurement surface not subjected to the friction treatment and the test surface is performed. A second measuring step for calculating a contact area,
When the actual contact area per unit area of the first measurement surface subjected to the friction treatment is S1 and the actual contact area per unit area of the second measurement surface not subjected to the friction treatment is S2, S1 and S2 An evaluation method for evaluating the friction performance of the vulcanized rubber using as a parameter.   The evaluation method according to claim 1, wherein the index is a ratio (S1 / S2) of the actual contact area S1 per unit area to the actual contact area S2 per unit area.   The base resin of the resin composition is a polycarbonate resin, and the first thin film and the second thin film made of the resin composition have a property of whitening due to a load. The first measurement step and the second measurement The evaluation method according to claim 1 or 2, wherein in the step, the actual contact area is calculated by measuring an area of the whitened region.   The evaluation method according to claim 1, wherein an adhesive substance is present on the first measurement surface subjected to the friction treatment. The thickness of the first thin film is 0.5 μm or more and 2.0 μm or less,
The thickness of the second thin film is 0.5 μm or more and 2.0 μm or less,
The evaluation method according to any one of claims 1 to 4, wherein the thickness of the first thin film and the thickness of the second thin film are the same. In the first loading step, the first thin film is loaded at a pressure of 0.1 MPa to 1.0 MPa,
In the second loading step, the second thin film is loaded at a pressure of 0.1 MPa to 1.0 MPa,
The evaluation method according to claim 1, wherein the first thin film and the second thin film are loaded with the same pressure.   The evaluation method according to claim 1, wherein the test surface is a pseudo road surface having a large number of fine irregularities on the surface.

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