Method for determining bonding strength of wet paper-based friction material

Abstract

The invention provides a wet-type paper-based friction material interlayer bonding strength determination method, and belongs to the technical field of paper-based friction material interlayer bonding strength determination, and the method comprises the following steps: vertically overlapping a first sample bonding block and a second sample bonding block, and smearing a binder on the vertical overlapping part, placing the wet-type paper-based friction material on the part coated with the binder, and carrying out hot-pressing vulcanization to obtain a sample to be detected; performing a tensile test on the to-be-detected sample until interlayer separation of the wet paper-based friction material sample to obtain a tensile load; and obtaining the interlayer bonding strength of the wet paper-based friction material according to the tensile load and the area of the wet paper-based friction material. According to the determination method, the interlayer bonding strength of the wet paper-based friction material can be rapidly and accurately determined, the repeatability is good, the precision is high, and a certain judgment basis is provided for the interlayer bonding strength of the wet paper-based friction material.

Description

Technical Field

[0001] The invention belongs to the technical field of measuring the interlayer bonding strength of paper-based friction materials, and in particular relates to a method for measuring the interlayer bonding strength of wet paper-based friction materials. Background Art

[0002] Wet paper-based friction material is a material with a reticular porous structure, which is made of fiber substrate and filler bonded by resin. The unique porous structure can store lubricating oil. As the friction material and the friction pair are compressed and deformed during operation, the lubricating oil inside the material is squeezed to the surface to form a lubricating oil film, which improves working efficiency. It is widely used in brakes, clutches and gearboxes of automobiles, engineering machinery, agricultural machinery and various industrial machinery.

[0003] At present, friction plates usually bond wet paper-based friction materials to linings to improve the friction coefficient of friction plates. Wet paper-based friction materials have a certain thickness, ranging from 0.6mm to 1.2mm, and their structure includes an upper fiber substrate layer and a lower filler and resin layer. During the long-term use of friction plates, due to the structural characteristics of wet paper-based friction materials, the upper fiber substrate layer and the lower filler and resin layer will separate, which will affect the service life of the wet paper-based friction materials. Therefore, it is necessary to measure the interlayer bonding force of wet paper-based friction materials.

[0004] Prior art CN113176203A discloses an interlayer bonding strength testing system, wherein the sample is installed in the mounting hole of the support plate, the axis of the sample is arranged in the horizontal direction, the driving plate of the driving seat is placed on the sample surface, and the sample is located in the driving groove, and the thrust meter is used to apply force to the limit plate, and the driving plate applies downward force to the sample to achieve separation of the two layers of the body. This interlayer detection method is mainly used to detect road concrete samples, and the thickness of the concrete sample is much greater than that of the wet paper-based friction material. Therefore, the existing interlayer bonding force detection method cannot detect the interlayer bonding force of the wet paper-based friction material.

[0005] Therefore, it is necessary to provide a method for measuring the interlayer bonding strength of wet test paper-based friction materials. Summary of the invention

[0006] In order to solve the problem that the method for measuring interlayer bonding force in the prior art cannot measure the interlayer bonding strength of wet paper-based friction materials, the present invention provides a method for measuring the bonding strength of wet paper-based friction materials.

[0007] In order to achieve the above-mentioned object of the invention, the technical solution of the present invention is as follows:

[0008] A method for determining the interlayer bonding strength of a wet paper-based friction material comprises the following steps:

[0009] The first adhesive sample block and the second adhesive sample block are arranged to overlap vertically to prevent the two adhesive blocks from generating a rotational force during the stretching process, and an adhesive is applied to the overlapping portion of the vertical overlap;

[0010] The wet paper-based friction material is placed on the part coated with the adhesive, and hot-pressed vulcanized to fix the wet paper-based friction material on the sticky sample block to prevent the wet paper-based friction material from falling off the sticky sample block during the tensile test, thereby affecting the test results, and obtaining the sample to be tested;

[0011] The sample to be tested is arranged in the drawing head chuck slot of the drawing head to fix the sample to be tested, and the drawing head chuck of the drawing head can improve the accuracy of the test, and the drawing head chuck with the sample to be tested is arranged on the tensile test equipment to perform the tensile test until the interlayers of the wet paper-based friction material are separated to obtain the tensile load; according to the tensile load and the area of ​​the wet paper-based friction material, the interlayer bonding strength of the wet paper-based friction material is obtained. Among them, the area of ​​the wet paper-based friction material specifically refers to the area of ​​the upper surface of the wet paper-based friction material.

[0012] In another preferred embodiment, the interlayer bonding strength of the wet paper-based friction material refers to the tensile load per unit area of ​​the wet paper-based friction material.

[0013] The specific calculation process of the interlayer bonding strength of the wet paper-based friction material is as follows:

[0014] Substituting the tensile load into the interlayer bonding strength calculation formula, the interlayer bonding strength of the wet paper-based friction material is obtained;

[0015] The interlayer bonding strength calculation formula is as follows:

[0016]

[0017] In the formula, A s It is the interlayer bonding strength of wet paper-based friction materials, in MPa;

[0018] L is the tensile load, in N;

[0019] A is the area of ​​the wet paper-based friction material, in mm 2 .

[0020] The interlayer bonding strength of the wet paper-based friction material refers to the maximum bonding force that the material layers per unit area can withstand when the wet paper-based friction material is subjected to a single tensile force.

[0021] In another preferred embodiment, the temperature of the hot press vulcanization is 170°C ± 10°C, the time is 900s, and the pressure is 1.0MPa-1.5MPa. Vulcanization under such conditions can effectively avoid the problem of the tensile test paper and the sticky sample block being peeled off due to poor vulcanization, resulting in the failure of the test data.

[0022] During the hot-pressing vulcanization process, if the hot-pressing temperature is too high, the thermosetting modified phenolic resin glue will be thermally degraded, resulting in the breakage of the resin molecules and affecting the bonding effect. If the time is too long, the resin will be over-cured, and cracks and breakages will easily occur in the bonding part, affecting the bonding effect. Excessive pressure will cause part of the thermosetting modified phenolic resin glue to flow out during the hot-pressing vulcanization process, resulting in poor bonding effect. Therefore, during the hot-pressing vulcanization process, it is necessary to accurately control the parameters of the hot-pressing vulcanization so that the wet paper-based friction material can be stably fixed to the sticky sample block to prevent the wet paper-based friction material from falling off the sticky sample block during the tensile test, thereby affecting the determination of the interlayer bonding force of the wet paper-based friction material.

[0023] In another preferred embodiment, the adhesive is a thermosetting modified phenolic resin adhesive, and the shear strength of the thermosetting modified phenolic resin adhesive is ≥15 MPa.

[0024] During the hot-press vulcanization process of thermosetting modified phenolic resin glue, the molecular chains in the resin undergo cross-linking reactions through heating and pressurization to form a three-dimensional network structure, thereby achieving curing and molding. The cured resin glue has higher cohesion and strength, and can more effectively bond the wet paper-based friction material and the sticky block together to form a solid structure.

[0025] In another preferred embodiment, the loading speed of the tensile test is 0.01 mm / min.

[0026] In another preferred embodiment, the vertically overlapping overlapping parts cover the upper and lower surfaces of the wet paper-based friction material to ensure uniform force distribution, thereby avoiding tearing from a certain corner due to uneven tensile force during testing, resulting in a smaller tensile load in the test and causing misjudgment.

[0027] In another preferred embodiment, the sample to be tested is further dried before the tensile test is performed; the drying temperature is 150° C. to 180° C., and the drying time is 1 hour to 2 hours.

[0028] In another preferred embodiment, the wet paper-based friction material is placed before the part coated with the adhesive and further comprises:

[0029] The surface of the wet paper-based friction material is polished and cut into a set size to obtain a pretreated wet paper-based friction material.

[0030] In another preferred embodiment, the polishing is performed by using sandpaper with a mesh size of 80 to 150 for surface polishing.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) In the present invention, the first adhesive block and the second adhesive block are arranged vertically to prevent the two adhesive blocks from generating rotational force during the tensile test, thereby avoiding deviations in the test results due to uneven force during the test. The wet paper-based friction material to be tested is stably fixed on the vertically overlapping overlapped portion of the two adhesive blocks by hot pressing vulcanization to prevent the wet paper-based friction material to be tested from falling off during the tensile test, thereby affecting the test results. The test method of the present invention can detect the interlayer bonding strength of wet paper-based friction materials of different thicknesses, and the test is fast and the test results are accurate.

[0033] (2) The method for determining the interlayer bonding strength of wet paper-based friction materials in the present invention can quickly and accurately determine the interlayer bonding strength of wet paper-based friction materials, providing a certain basis for determining the interlayer bonding strength of wet paper-based friction materials. In addition, the determination method of the present invention has good repeatability and high accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 2 is a structural diagram of a drawing head in an embodiment of the present invention.

[0035] Figure 2 Schematic diagram of a sample sticking block in an embodiment of the present invention.

[0036] Figure 3 It is a front view of the drawing head in the embodiment of the present invention.

[0037] Figure 4 1 is a top view of a drawing head in an embodiment of the present invention.

[0038] Figure 5 It is a schematic diagram of two sample sticking blocks vertically overlapping in an embodiment of the present invention.

[0039] Explanation of the reference numerals: 1 - pulling head chuck, 2 - pulling head slot, 3 - wet paper-based friction material bonding area, 4 - first sticking sample block, 5 - second sticking sample block. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0041] Unless otherwise specified, the experimental methods described in the following examples are all conventional methods; the reagents and materials described are all commercially available unless otherwise specified.

[0042] Usually, wet paper-based friction materials are bonded to the lining to increase the friction coefficient. The inventors of the present invention found that the wet paper-based friction materials will separate from each other during use. This is mainly because the wet paper-based friction materials have a certain thickness, wherein the fiber substrate is located in the upper layer, and the filler and resin are located in the lower layer. Therefore, during use, the fiber substrate layer located in the upper layer and the filler and resin layer located in the lower layer will separate, thereby affecting the service life of the wet paper-based friction materials. However, in the prior art, the bonding strength between the wet paper-based friction materials and the lining is usually tested, but the bonding strength between the layers of the wet paper-based friction materials is not tested.

[0043] The present invention uses two vertically arranged sample sticking blocks to prevent the two bonding blocks from generating a rotational force during the tensile test, thereby avoiding deviations in the test results due to uneven force during the test. The wet paper-based friction material to be tested can be stably fixed between the two sample sticking blocks by hot pressing vulcanization, thereby preventing the wet paper-based friction material from falling off the sample sticking blocks during the tensile test. The detection method of the present invention can detect the interlayer bonding strength of wet paper-based friction materials of different thicknesses, and the detection is fast and the detection results are accurate.

[0044] The following is a detailed description of a method for determining the interlayer bonding strength of a wet paper-based friction material.

[0045] The following examples of materials and instrument parameters are as follows:

[0046] Caliper: Measuring range is 0mm~200mm, accuracy is 0.02mm.

[0047] Parameters of the sample sticking block: a rectangular metal block with a size of 30mm×25mm and a thickness of 3mm±0.05mm; made of 50 steel, with a hardness of HRC35-45 and a flatness of 0.05mm; the surface is sandblasted and deburred, and wiped clean with a dust-free cloth dipped in anhydrous alcohol.

[0048] Pulling head, such as Figure 1 As shown, the drawing head comprises a drawing head chuck 1 and a drawing head slot 2;

[0049] A slot is provided on one side of the drawing slot 2, and the slot is used to configure a sample sticking block to fix the sample sticking block. The drawing head chuck 1 is fixedly connected to the drawing head slot 2 and is located on a side away from the slot; the drawing head chuck 1 is coaxially fixedly connected to the drawing head slot 2. The parameters of the drawing head chuck 1 and the drawing head slot 2 are as follows: Figure 3 and Figure 4 As shown, l1 is 25mm, l2 is 20mm±0.03mm, l3 is 38mm±0.05mm, l4 is 40mm, l5 is 26mm, l6 is 30mm, l7 is 3mm, l8 is 6mm, and the chamfer between the top circular surface and the side surface of the drawing head chuck 1 is C0.3. The drawing head in the present invention can ensure the coaxiality of the chuck as a whole during the detection process, thereby improving the accuracy of the detection.

[0050] The testing conditions of the tensile test are as follows: the ambient temperature is 23℃±2℃, the relative humidity is 50%±5%, and the circulating wind speed is not more than 0.2m / s.

[0051] Adhesive: Thermosetting modified phenolic resin adhesive purchased from Shanghai Xinguang Chemical Co., Ltd. Anchor Brand 204 model, with a shear strength greater than or equal to 15 MPa at room temperature.

[0052] The model of the blast drying oven is DHG-9145A, and the temperature control accuracy is ±3%.

[0053] The model of the universal tensile testing machine is WDW-50E, the measuring range is 0N~500N, the accuracy should be no more than 0.01N, the displacement resolution should be no more than 0.01mm, and the constant loading speed should be no more than 0.01mm / min.

[0054] Example 1

[0055] A method for determining the interlayer bonding strength of a wet paper-based friction material comprises the following steps:

[0056] S1. The bonding surface of the wet paper-based friction material to be tested is polished with 80-mesh sandpaper and then blown clean to obtain the wet paper-based friction material.

[0057] S2, such as Figure 2 and Figure 5 As shown, the first adhesive sample block 4 and the second adhesive sample block 5 are vertically overlapped to ensure that the angle α between the first adhesive sample block 4 and the second adhesive sample block 5 is 90°; the overlapping portion of the first adhesive sample block 4 and the second adhesive sample block 5 vertically overlaps is the wet paper-based friction material bonding area 3, and the thermosetting modified phenolic resin glue is applied to the wet paper-based friction material bonding area 3.

[0058] S3. Measure and cut the wet paper-based friction material in S1 according to the size of the bonding area 3 of the wet paper-based friction material in S2 with a caliper, and ensure that the cut part has no visible cracks, fallen edges, missing corners, protrusions, pits, holes and other defects. Calculate its area, which is recorded as A.

[0059] S4. Place the pretreated wet paper-based friction material cut in S3 in the bonding area 3 of the wet paper-based friction material, and perform hot pressing vulcanization for 900 seconds at a vulcanization temperature of 170° C. and a pressure of 1.0 MPa, so that the wet paper-based friction material can be stably fixed on the bonding area 3 of the wet paper-based friction material. After the hot pressing vulcanization is completed, place it in a 150° C. forced air drying oven for drying for 2 hours, cool it to room temperature with the furnace, and obtain a sample to be tested.

[0060] S5. Clamp the first sample block 4 and the second sample block 5 on the sample to be tested into the corresponding drawing head clamping slot 2 respectively, fix the drawing head chuck 1 on the universal tensile testing machine, start the universal tensile testing machine, load at a constant speed of 0.01 mm / min, and perform a tensile test until the layers of the wet paper-based friction material sample are separated. Record the maximum tensile force value when the layers are separated on the universal tensile testing machine, which is recorded as the tensile load L.

[0061] S6. Substitute the area A and the tensile load L into the interlayer bonding strength calculation formula to calculate the interlayer bonding strength of the wet paper-based friction material; wherein the interlayer bonding strength calculation formula is as follows:

[0062]

[0063] In the formula, A s is the interlayer bonding strength of the wet paper-based friction material, in MPa; L is the tensile load, in N; A is the area of ​​the wet paper-based friction material, in mm 2 .

[0064] In order to further demonstrate the effect of the method for determining the interlayer bonding strength of wet paper-based friction materials in the present invention, the following experiment was conducted.

[0065] 1. Determination of interlayer bonding strength of different wet paper-based friction materials

[0066] Two different wet paper-based friction materials were selected, with thicknesses of 0.6 mm and 1.2 mm, respectively, for interlayer bonding strength measurement. The measurement was performed according to the method in Example 1, wherein the dimensions of the two pre-treated wet paper-based friction materials were both (25 mm ± 0.5 mm) × (25 mm ± 0.5 mm). The test results are shown in Table 1.

[0067] Table 1 Interlayer bonding strength values ​​of different wet paper-based friction materials

[0068] Group Thickness of wet paper-based friction material Interlayer bonding strength (MPa) 1 0.6mm 0.2 2 1.2mm 0.3

[0069] From the results in Table 1, it can be seen that the interlayer bonding strength determination method of the wet paper-based friction material in the present invention can determine the interlayer bonding strength of wet paper-based friction materials of different thicknesses, and has a wide range of application effects. Since the detection of interlayer bonding strength in the prior art is mainly the detection of interlayer bonding strength of building materials, and the thickness of building materials is much greater than the thickness of 0.6mm to 1.2mm of the wet paper-based friction material in the present invention, it is impossible to detect the interlayer bonding strength of the wet paper-based friction material using the prior art. It can be seen that the method in the present invention is specifically for determining the interlayer bonding strength of wet paper-based friction materials.

[0070] 2. Repeatability

[0071] For a wet paper-based friction material with a thickness of 1.2 mm and a wet paper-based friction material with a thickness of 0.6 mm, the method in Example 1 was used to obtain five independent measurement results under repeatability conditions. The specific results are shown in Tables 2 and 3.

[0072] The absolute difference is calculated as follows:

[0073] Absolute difference = (detection value - average value) / average value * 100%

[0074] Table 2 Repeatability test results of wet paper-based friction materials with a thickness of 0.6 mm

[0075]

[0076]

[0077] Table 3 Repeatability test results of wet paper-based friction materials with a thickness of 1.2 mm

[0078] frequency Interlayer bonding strength (MPa) Absolute difference (%) 1 0.32 3.23％ 2 0.3 3.23％ 3 0.3 3.23％ 4 0.32 3.23％ 5 0.31 0.00％

[0079] It can be seen from the results in Table 2 and Table 3 that the method for determining the interlayer bonding strength of wet paper-based friction materials in the present invention has good repeatability, and the absolute difference is less than 10%. The absolute difference is determined by summarizing the repeatability and reproducibility of the test data and the material performance verification. That is, the absolute difference is less than 10%, which shows that the method for determining the interlayer bonding strength of wet paper-based friction materials in the present invention has good repeatability and can accurately determine the interlayer bonding strength of wet paper-based friction materials.

[0080] The interlayer bonding strength determination method of the wet paper-based friction material of the present invention can detect the interlayer bonding strength of wet paper-based friction materials of different thicknesses, and has good repeatability and high accuracy. The entire detection process is simple and easy to operate, and the interlayer bonding strength of the wet paper-based friction material can be quickly determined, providing a detection standard for judging the interlayer bonding strength of the wet paper-based friction material.

[0081] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for determining the interlayer bonding strength of a wet paper-based friction material, characterized in that: The following steps are involved: The first adhesive sample block and the second adhesive sample block are arranged to overlap vertically, and adhesive is applied to the overlapping portion of the vertical overlap; The wet paper-based friction material is placed on the part coated with the adhesive, and hot-pressed and vulcanized to obtain a sample to be tested; The sample to be tested is subjected to a tensile test until the wet paper-based friction material layers are separated to obtain a tensile load; based on the tensile load and the area of ​​the wet paper-based friction material, the interlayer bonding strength of the wet paper-based friction material is obtained.

2. The method for determining the interlayer bonding strength of wet paper-based friction materials according to claim 1, characterized in that: The interlayer bonding strength of the wet paper-based friction material refers to the tensile load per unit area of ​​the wet paper-based friction material.

3. The method for determining the interlayer bonding strength of wet paper-based friction materials according to claim 1, characterized in that: The specific conditions of the hot pressing vulcanization are as follows: The temperature is 170℃±10℃, the time is 900s, and the pressure is 1.0MPa~1.5Mpa.

4. The method for determining the interlayer bonding strength of wet paper-based friction materials according to claim 1, characterized in that: The adhesive is a thermosetting modified phenolic resin adhesive.

5. The method for determining the interlayer bonding strength of wet paper-based friction materials according to claim 1, characterized in that: The loading speed of the tensile test was 0.01 mm / min.

6. The method for determining the interlayer bonding strength of wet paper-based friction materials according to claim 1, characterized in that: The vertically overlapping overlapped portions cover the upper surface and the lower surface of the wet paper-based friction material.

7. The method for determining the interlayer bonding strength of wet paper-based friction materials according to claim 1, characterized in that: Before the tensile test of the sample to be tested is carried out, the method further comprises drying; The drying temperature is 150° C. to 180° C., and the drying time is 1 h to 2 h.

8. The method for determining the interlayer bonding strength of wet paper-based friction materials according to claim 7, characterized in that: The wet paper-based friction material is placed before the part coated with the binder and further comprises: The surface of the wet paper-based friction material is polished and cut into a set size to obtain a pretreated wet paper-based friction material.

9. The method for determining the interlayer bonding strength of wet paper-based friction materials according to claim 8, characterized in that: The grinding is performed by using sandpaper with a mesh number of 80 to 150 to perform surface grinding treatment.

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