Method for accurate determination of barium sulfate content in automobile brake pad

Abstract

The application provides an accurate determination method of barium sulfate content in a brake pad for an automobile, S1: XRF element of a sample to be measured is preliminarily screened to check whether Ba and S elements exist, if yes, step S3 is performed, and if not, the test is ended; S2: the sample is ashed, inorganic fillers are extracted, and then are acid-dissolved and filtered to collect inorganic fillers insoluble in acid; S3: the inorganic fillers insoluble in acid in step S2 are subjected to semi-melting reaction to obtain a salt solution, and leaching of sulfate is performed; S4: soluble barium salt is added, and a precipitate is obtained through filtration; S5: the precipitate obtained in step S4 is calcined to obtain an experimental product, and is weighed; and S6: the barium sulfate content in the pad is obtained through calculation. The accurate determination method of barium sulfate content in the brake pad for the automobile is accurate in quantification, good in data repeatability, simple and convenient to operate, and provides a test method reference for quality control, formula upgrading and improvement.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of chemistry, and particularly relates to a method for accurately determining the content of barium sulfate in a brake pad for an automobile. BACKGROUND

[0002] The brake system is an important part of an automobile, and directly affects the safety performance of the automobile. According to the investigation results of relevant departments, the brake system failure accounts for 45% in the traffic accidents caused by the problems of the automobile itself, and the brake pad is the core of the brake system. It can be said that the quality of the brake pad determines the performance of the brake system.

[0003] There are many types of brake pads on the market, and the focuses of the formulations and processes of various manufacturers are different. There are NAO type, ceramic type, semi-metal type, low metal type and metal type, etc., and the prices are different, and the qualities are uneven. Barium sulfate is widely used in most brake pads as a main inorganic filler in recent years due to its good friction performance, chemical stability and non-pollution. At the same time, the addition of barium sulfate in the brake pad also improves the density of the pad, and improves the anti-aging performance and weather resistance of the pad. Since barium sulfate is insoluble in acid and alkali, it is not easy to be dissolved into a liquid for accurate testing by using some element analysis equipment. At the same time, some element direct testing equipment cannot give accurate determination results.

[0004] For the brake pad of barium sulfate type, the proportion control of the content is of great significance to improve the wear resistance and stability of the pad. The development of the method for accurately testing the content of barium sulfate has important guiding significance for the upgrading of the brake pad formulation process, quality control, market sampling and the like. SUMMARY

[0005] Therefore, the present application aims to provide a method for accurately determining the content of barium sulfate in a brake pad for an automobile, which effectively solves the problem of whether the amount of theoretically added barium sulfate in the industrial production of the brake pad is consistent with the amount of barium sulfate in the actual product.

[0006] To achieve the above object, the technical scheme of the present application is as follows:

[0007] A method for accurately determining the content of barium sulfate in a brake pad for an automobile, comprising the following steps:

[0008] S1: preliminarily screening the XRF elements of the sample to be tested to check whether there are Ba and S elements, and if yes, performing step S3, and if not, ending the test;

[0009] S2: sampling the pad, ashing the sample to be tested, extracting inorganic fillers, and then acid dissolving and filtering to collect inorganic fillers insoluble in acid;

[0010] S3: Semi-melting reaction is performed on the inorganic filler insoluble in acid in step S2 to obtain a salt solution, and leaching of sulfate is performed;

[0011] S4: A soluble barium salt is added, and a precipitate is obtained by filtration;

[0012] S5: The precipitate obtained in step S4 is calcined to obtain an experimental product, and the weight is measured;

[0013] S6: The content of barium sulfate in the lining is obtained by calculation.

[0014] The XRF element preliminary screening of the sample to be tested in step S1 is to directly test the sample to be tested by using an X-ray fluorescence spectrometer, and to check whether the sample to be tested contains Ba and S elements.

[0015] The lining sampling in step S2 is to wipe the sample to be tested with a water-absorbing paper, place the sample at the bottom of a large sample bag, fix it on the drill bed table with a clamp to ensure the stability of the sample and the levelness of the friction surface, avoid drilling in the area within 6 mm from the edge of the friction material, and place the collected drillings in a clean sealed bag, and make a mark for later use.

[0016] In step S2, the drill bed table is rotated, a hard alloy drill bit with a diameter of 2-4 mm is used, and the stopping point of the drill bit is adjusted to 1 / 2 of the lining friction layer. The drill bed table is adjusted, the drill bed spindle speed is set to 400±100 rpm, the sample bag is pulled up to a position just covering the drill bit, and when the drill bit contacts the friction surface, the descending speed of the drill bit is kept at 0.15-0.25 mm / s.

[0017] The ashing in step S2 includes the following steps: after the crucible is burned to a constant weight, the sample is placed in the crucible, and the crucible is placed in a muffle furnace without covering, and ashing is performed at 850°C for 5h. After the crucible is cooled, it is placed on an electronic balance to weigh and record. The crucible with the sample to be tested after weighing is placed in a muffle furnace and heated at 850°C for 30 min. After the crucible is fully cooled, it is placed on an electronic balance to weigh and record. Repeat the operation until the mass of the ash of the sample to be tested is obtained, calculate the ash, and collect it in a sample bag for later use. The ash calculation formula is as follows:

[0018]

[0019] Where m0 is the mass of the empty crucible, m1 is the mass of the crucible with the sample, and m2 is the mass of the crucible with the ash burned to a constant weight.

[0020] The acid dissolution filtration in step S2 includes boiling the hydrochloric acid solution at 200℃ for 30min, boiling the nitric acid for 20min, collecting the filter residue after sufficient cooling, taking the ceramic crucible, putting it into the filter paper containing the filter residue, cutting the part above the crucible with scissors into small pieces and putting them into the crucible, half covering the crucible and putting it into the muffle furnace, setting the temperature to 500-550℃, and ashing for 90min.

[0021] The semi-melting reaction in step 3 includes putting the sample treated in step 2 into the crucible, adding the sodium carbonate-zinc oxide mixed flux into the crucible, the sodium carbonate-zinc oxide mixed flux is a molten solution of sodium carbonate and zinc oxide in a mass ratio of 3:2, the mass ratio of the sodium carbonate-zinc oxide mixed flux to the sample is 5:1.5-3, putting the crucible into the muffle furnace, and heating the sample,

[0022] The sulfate leaching includes adjusting the hot plate to 280-320℃, immersing the cooled crucible in hot 15%-25% sodium carbonate solution and hot 15-25g / L sodium carbonate solution, immersing the cooled crucible in hot water for multiple times, immersing it in hot sodium carbonate solution again, collecting the leaching solution in a beaker, and collecting the precipitate in a watch glass;

[0023] In the sulfate leaching process, whether the hot plate is heated and the temperature setting is adjusted at any time according to the leaching condition, in order to improve the recovery rate of sulfate, the beaker collecting the leaching solution can be placed on the hot plate for heat preservation;

[0024] The barium salt adding includes heating and boiling to remove carbon dioxide, adjusting the solution to be neutral, and adding barium chloride solution.

[0025] The burning of the experimental product in step S5 includes burning the crucible to a constant temperature, putting the crucible containing the experimental product after weighing into the muffle furnace, continuing to heat at 850-900℃ for 30-40min, fully cooling, weighing and recording it on the electronic balance, and repeating the operation until the constant weight of the barium sulfate in the ash sample is obtained, calculating the content of barium sulfate in the ash sample, and then obtaining the content of barium sulfate in the brake pad for automobile. The calculation formula is as follows:

[0026]

[0027] Wherein m3 is the mass of the ash sample to be measured, m4 is the mass of the 100ml empty crucible, and m5 is the mass of the crucible plus the barium sulfate in the ash sample after burning to a constant weight.

[0028] After step S5, the product is tested by infrared, and the infrared spectrum is obtained. The infrared spectrum is qualitatively analyzed to verify whether the experimental product is barium sulfate.

[0029] Compared with the prior art, the method for accurately determining the barium sulfate content in the automobile brake pad has the following beneficial effects:

[0030] The method realizes accurate determination of the barium sulfate content in the automobile brake pad, effectively solves the problem of whether the amount of theoretically added barium sulfate in the industrial production of the brake pad is consistent with the amount of barium sulfate in the actual product, is quantitative and accurate, has good data repeatability, is simple and convenient to operate, and provides a test method reference for quality control, formula upgrading and improvement of enterprises. BRIEF DESCRIPTION OF DRAWINGS

[0031] The drawings that form a part of this application provide further understanding of the present application, and the illustrative embodiments of the present application and their description serve to explain the present application. The present application is not limited by the improper limitation. In the drawings:

[0032] Figure 1 A flowchart of the method for accurately determining the barium sulfate content in the automobile brake pad according to the embodiment of the present application is shown in the figure.

[0033] Figure 2 The infrared spectrum of the experimental product according to the embodiment of the present application is shown in the figure.

[0034] Figure 3 The infrared spectrum matching diagram of the experimental product according to the embodiment of the present application is shown in the figure. DETAILED DESCRIPTION

[0035] Unless defined, the technical terms used in the following examples have the same meaning as generally understood by those skilled in the art to which the present application belongs. Unless otherwise specified, the test reagents used in the following examples are conventional biochemical reagents; and the experimental methods described are conventional methods.

[0036] The present application will be described in detail below with reference to the examples and drawings.

[0037] First, the XRF element preliminary screening of the sample to be tested is performed.

[0038] The brake pad sample to be tested is directly tested by using an X-ray fluorescence spectrometer to test whether it contains Ba and S elements. If it exists, the experiment is performed according to the following scheme. If it does not exist, the subsequent experiment is not needed.

[0039] Experimental reagents and materials:

[0040] 1. Unless otherwise specified, only analytical pure reagents and third grade water meeting the requirements of GB / T 6682 are used in the analysis process.

[0041] 2. Sodium carbonate-zinc oxide mixed solvent: sodium carbonate is ground in a agate mortar and then passed through a 100 micron metal wire sieve (about 150 mesh) and mixed with zinc oxide at a mass ratio of 3:2.

[0042] 3. Hydrochloric acid (1+1) solution, 10% nitric acid solution.

[0043] 4. 20% sodium carbonate solution, 20 g / L sodium carbonate solution, 100 g / L barium chloride solution.

[0044] 5. Methyl orange / methyl red indicator.

[0045] 6. Slow quantitative filter paper: φ 11 cm, φ 15 cm.

[0046] Experimental equipment and tools:

[0047] 1. Multifunctional drilling and milling machine, 3 mm diameter hard alloy drill bit.

[0048] 2. Energy-saving electric furnace (muffle furnace): can accurately control the temperature within 600-800°C, and the temperature deviation is maintained within ±25°C; crucible tongs.

[0049] 3. Electronic balance: graduation value is 0.1 mg.

[0050] 4. Graphite electric heating plate: can accurately control the temperature within 200-300°C.

[0051] 5. Agate mortar, 100 micron metal wire sieve (about 150 mesh).

[0052] 6. Dryer: silica gel desiccant inside.

[0053] Preparation of experimental vessels:

[0054] 1. 50 ml, 100 ml, 200 ml ceramic crucibles: wash the crucibles and place them in the muffle furnace at 550°C to heat to constant weight, then cool thoroughly and place in the dryer for standby.

[0055] 2. All available glassware: beaker, graduated cylinder, volumetric flask, funnel, dropper, watch glass, etc. are washed and dried and placed in the dryer for standby.

[0056] Experimental specific steps:

[0057] First: preparation of test samples

[0058] Clean the brake pad sample to be tested with a piece of absorbent paper to ensure that the friction material portion is free of any dust and foreign matter. Place the sample at the bottom of a large sample bag (to collect the drillings) and secure it to the drill press table with a clamp to ensure the stability of the sample and the levelness of the friction surface (at this time, make sure that the sample bag does not break when the sample is clamped). Rotate the drill press table, use a 3mm diameter carbide drill bit, and adjust the stopping point of the drill bit to be at 1 / 2 of the friction layer of the pad. Adjust the drill press table, set the drill press spindle speed to (400 ± 100) rpm, and pull the sample bag up to a position just covering the drill bit (at this time, make sure that the edge of the sample bag does not interfere with the rotation of the spindle to avoid accidents). When drilling, maintain the descent speed of the drill bit at 0.15-0.25 mm / s after the drill bit contacts the friction surface, and adjust the descent speed of the drill bit at any time according to the shape of the drillings (faster speed will produce a mixture of coarse particles, thus changing the chemical composition of the measured sample), and drill symmetrically and uniformly on both friction surfaces of the pad. Since the edges of most pads on both sides have a certain slope, which will affect drilling, avoid drilling in the area within 6mm of the edge of the friction material.

[0059] Place the collected drillings in a clean sealed bag and label it for future use.

[0060] Second: ashing of the sample to be tested

[0061] Place a 200ml ceramic crucible that has been previously ignited to a constant weight on an electronic balance and record it to the nearest 0.1mg, then weigh 2.0000g of the drilled sample in the crucible and record it to the nearest 0.1mg. Place it in a muffle furnace without a lid, set the temperature to 850°C and ash for 5h. After the crucible cools, place it on an electronic balance and record it to the nearest 0.1mg, then place the weighed crucible containing the sample to be tested in the muffle furnace and continue heating at 850°C for 30min. After the crucible cools completely, place it on an electronic balance and record it to the nearest 0.1mg, and repeat this operation until a constant weight of the ash of the sample to be tested is obtained (after each ashing is complete, the crucible needs to be removed and placed in a desiccator to cool slightly with tongs). Calculate the ash content and collect it in a sample bag for future use. The ash content calculation formula is as follows:

[0062]

[0063] Where m0 is the mass of the 200ml empty crucible, m1 is the mass of the crucible plus the sample, and m2 is the mass of the crucible plus the ashed sample to a constant weight.

[0064] Third: acid dissolution of impurities

[0065] The hot plate was set to 200°C. 0.2500 g of the ashed sample prepared in the previous stage was weighed on an electronic balance in a 50 ml beaker and recorded to the nearest 0.1 mg. The beaker was placed on the hot plate, 15 ml of hydrochloric acid (1 + 1) solution was added and heated to a gentle boil for 30 min, then 15 ml of 10% nitric acid solution was added and heated to a gentle boil for 20 min (the temperature was increased as necessary depending on the heating conditions) and then removed. After cooling, the residue was collected by filtering through two layers of φ 11 cm slow quantitative filter paper.

[0066] Fourth: ashing of the residue

[0067] A 50 ml ceramic crucible was taken and the filter paper containing the residue was placed in it. The part of the filter paper that was above the edge of the crucible was cut into small pieces with scissors and placed in the crucible together. The crucible was placed in a muffle furnace with half a lid. The temperature was set to 500-550°C and the ashing was carried out for 90 min.

[0068] Fifth: preliminary preparation for the semi-fusion reaction

[0069] After the crucible had cooled, it was placed on an electronic balance and 5 g of the mixed solvent was added to the crucible. A small stick made from a 1 / 4 φ 11 cm slow quantitative filter paper was used to stir the sample until it was evenly distributed. The stick was not removed. Another 2 g of the mixed solvent was added on top of the sample and the lid was placed on the crucible.

[0070] Sixth: semi-fusion reaction

[0071] The crucible was placed in a muffle furnace and the temperature program was set as follows:

[0072]

[0073] Seventh: leaching of sulfate

[0074] The hot plate was adjusted to 300°C and hot triple distilled water, hot 20% sodium carbonate solution and hot 20 g / L sodium carbonate solution were prepared. The cooled crucible was placed on the hot plate and leached with 100 ml of hot water in small amounts (each time the solution was boiled for 5-6 min and the amount of leaching solution added each time should not be too small to prevent droplets from splashing during boiling). The leaching solution was collected in a 250 ml beaker. Then 30 ml of hot 20% sodium carbonate solution was added and leached in small amounts (each time the solution was boiled for 5-6 min and the amount of leaching solution added each time should not be too small to prevent droplets from splashing during boiling). The leaching solution was collected in a 250 ml beaker. While hot, the leaching solution was filtered using a φ 15 cm slow quantitative filter paper into a 500 ml beaker. The beaker and the precipitate were washed with 30 ml of hot 20 g / L sodium carbonate solution in small amounts and the precipitate was collected in a watch glass.

[0075] During the leaching of sulfate, the heating of the hot plate and the temperature setting were adjusted at any time according to the leaching conditions. To improve the recovery rate of sulfate, the beaker collecting the leaching solution can be placed on the hot plate for heat preservation.

[0076] Eighth: Precipitation of sulphate

[0077] Adjust the hot plate to 250°C. After the filtrate has cooled, add 1-2 drops of methyl orange / red indicator to it. Start adding hydrochloric acid (1+1) solution to neutralize the filtrate. Continue adding while slowly shaking the beaker until no bubbles are produced. Continue adding while slowly shaking the beaker until the solution turns red, with an excess of 5 ml. Adjust the volume of the filtrate to 300 ml with triple distilled water. Place the beaker on the hot plate and heat to boil off the carbon dioxide. After a few minutes, remove the beaker from the hot plate and add 1 ml of hydrochloric acid (1+1) solution to verify that there are no bubbles. Slowly add 25 ml of 100 g / L barium chloride solution and shake gently. Continue heating to boil for 5-6 minutes. Turn off the heat and allow the residual heat to keep the beaker warm. After it has cooled, remove it and allow it to stand overnight.

[0078] Ninth: Filtration of the barium sulphate precipitate

[0079] Filter the precipitate in the beaker using a φ 15 cm slow-speed quantitative filter paper and wash the beaker and precipitate with triple distilled water in small amounts and several times. Place a 100 ml porcelain crucible, which has been previously ignited to a constant weight, on an electronic balance and weigh and record it to the nearest 0.1 mg. Place the filter paper with the precipitate in the crucible, half-covering it.

[0080] Tenth: Ignition of the barium sulphate precipitate

[0081] Place the crucible in a muffle furnace and set the temperature program as follows:

[0082]

[0083] After the crucible has cooled, place it on an electronic balance and weigh and record it to the nearest 0.1 mg. Then place the weighed crucible containing the experimental product in the muffle furnace and continue heating at 850°C for 30 minutes. After it has cooled completely, place it on an electronic balance and weigh and record it to the nearest 0.1 mg. Repeat this operation until a constant weight is obtained, which gives the mass of the barium sulphate in the ash sample (after each heating is completed, the crucible is removed and placed in a desiccator to cool slightly before being removed again). Calculate the content of barium sulphate in the ash sample and, consequently, the content of barium sulphate in the brake pad for automobiles. The calculation formula is as follows:

[0084]

[0085] where m3 is the mass of the ash sample to be tested, m4 is the mass of the 100 ml empty crucible, and m5 is the mass of the crucible plus the barium sulphate in the ash sample after ignition to a constant weight.

[0086] Eleventh: Analysis of experimental data

[0087] Table 1 Experimental data

[0088]

[0089] According to the experimental data results, the parallelism of the lining-1 and the lining-2 data is good, and the recovery rate of the pure barium sulfate prepared together with the experiment is close to 100%, which indicates that the accuracy of the experimental method is good.

[0090] Experimental product verification

[0091] 1. Experimental instrument: Fourier infrared spectrometer (FTIR), model Nicolet iS50, produced by Thermo Fisher Scientific Corporation of the United States; transmission mode sample stage.

[0092] 2. Experimental tools and reagents: infrared lamp, tablet press, agate mortar, potassium bromide for infrared spectroscopy.

[0093] 3. FTIR analysis conditions: KBr tablet transmission method (parameter file is transmission E.S.P.), scanning range is 40-4000cm -1 , scanning times are 32 times, and the resolution is 4cm -1 .

[0094] 4. Experimental method: the instrument is turned on and connected with the software, preheated for more than 30min, and the potassium bromide for infrared spectroscopy is baked under the infrared lamp for standby. A small amount of experimental product is taken in the agate mortar, ground into powder, mixed with potassium bromide (the weight ratio of sample to potassium bromide is 1:100), and grinded uniformly (the whole sample preparation process needs to be carried out under the infrared lamp), and the tablet press is used to press into transparent tablets under normal pressure, and the machine is tested.

[0095] 5. Test spectrum analysis

[0096] As Figure 1 and Figure 2 The three experimental products all reflect the information of barium sulfate, and the experimental products are identified as barium sulfate by comprehensive analysis of the characteristic absorption peaks of the barium sulfate standard.

[0097] The method realizes the accurate determination of the content of barium sulfate in the brake lining of the automobile, effectively solves the problem whether the theoretical amount of added barium sulfate in the industrial production of the brake lining is consistent with the amount of barium sulfate in the actual product, and provides a test method reference for quality control, formula upgrading and improvement for enterprises.

[0098] The above only describes the preferred embodiments of the present application, and does not limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. An accurate method for determining the barium sulfate content in automotive brake pads, characterized in that: Includes the following steps: S1: Perform preliminary XRF element screening on the sample to be tested to check for the presence of Ba and S elements. If Ba and S are present, proceed to step S2; otherwise, end the test. S2: Liner sampling, ashing of the sample to be tested, extraction of inorganic filler, followed by acid dissolution and filtration, collection of inorganic filler insoluble in acid; S3: The inorganic filler that is insoluble in acid in step S2 is subjected to a semi-melting reaction to obtain a salt solution, which is then used for sulfate leaching. S4: Add soluble barium salt, filter to obtain precipitate; S5: The precipitate obtained in step S4 is calcined to obtain the experimental product, and then weighed. S6: The content of barium sulfate in the lining was calculated; In step S1, the preliminary screening of XRF elements of the sample to be tested involves directly testing the brake pad sample to be tested using an X-ray fluorescence spectrometer to check whether it contains Ba and S elements. In step S2, the lining sample is cleaned by wiping the brake lining sample to be tested with absorbent paper, placing the sample at the bottom of a large sample bag, and fixing it on the drilling table with a clamp to ensure the stability of the sample and the horizontality of the friction surface. Avoid drilling in the area within 6 mm of the edge of the friction material. Place the collected drill cuttings in a clean sealed bag and mark it for later use. The ashing process in step S2 includes: igniting the crucible to a constant weight, placing the sample in the crucible, placing it uncovered in a muffle furnace, setting the temperature to 850℃ for 5 hours, weighing the crucible on an electronic balance after cooling, and recording the weight; then placing the weighed crucible containing the sample in the muffle furnace and heating it at 850℃ for another 30 minutes; after the crucible has cooled sufficiently, weighing it on an electronic balance and recording the weight; repeating this operation until a constant weight is obtained to obtain the mass of the ash content of the sample, calculating the ash content, and collecting it in a sample bag for later use. The ash content calculation formula is as follows: ； Where m0 is the mass of the empty crucible, m1 is the mass of the crucible with the sample, and m2 is the mass of the crucible with ash added and ignited to constant weight; The acid dissolution filtration in step S2 includes heating the ashed sample at a constant temperature of 200℃, first boiling it in hydrochloric acid solution for 30 minutes, then adding nitric acid and boiling it for 20 minutes. After fully cooling, the filter residue is collected. A ceramic crucible is taken, and filter paper containing the filter residue is placed in it. The part that protrudes above the rim of the crucible is cut into small pieces with scissors and placed into the crucible together. The crucible is then partially covered and placed in a muffle furnace. The temperature is set to 500℃~550℃ and ashed for 90 minutes. The semi-melting reaction in step S3 includes placing the sample processed in step S2 into a crucible, adding a sodium carbonate-zinc oxide mixed flux to the crucible, the sodium carbonate-zinc oxide mixed flux being a molten solution of sodium carbonate and zinc oxide in a mass ratio of 3:2, and the mass ratio of the sodium carbonate-zinc oxide mixed flux to the sample being 5:1.5-3, placing the crucible into a muffle furnace, and heating the sample. The sulfate leaching process involves adjusting the heating plate to 280-320°C, placing the cooled crucible on the heating plate, leaching with hot water in small amounts multiple times, followed by leaching with a hot 15%-25% sodium carbonate solution, collecting the leaching solution in a beaker, and collecting the precipitate in a watch glass. During the sulfate leaching process, whether the heating plate is heated and the temperature setting are adjusted at any time depending on the leaching situation. In order to improve the sulfate recovery rate, the beaker collecting the leaching solution is placed on the heating plate for heat preservation.

2. The method for accurately determining the barium sulfate content in automotive brake pads according to claim 1, characterized in that: In step S2, rotate the drill table, use a carbide drill bit with a diameter of 2-4mm, and adjust the stop point of the drill bit descent to 1 / 2 of the friction layer of the liner. Adjust the drill table, set the drill spindle speed to 400±100rpm, and pull the sample bag up to a position that just covers the drill bit. When drilling, after the drill bit contacts the friction surface, maintain the descent speed of the drill bit at 0.15~0.25mm / s.

3. The method for accurately determining the barium sulfate content in automotive brake pads according to claim 1, characterized in that: The addition of soluble barium salt in step S4 includes heating and boiling to remove carbon dioxide, adjusting the solution to neutral, and adding barium chloride solution.

4. The method for accurately determining the barium sulfate content in automotive brake pads according to claim 1, characterized in that: The ignition of the experimental product in step S5 includes igniting the crucible to a constant temperature, then placing the weighed crucible containing the experimental product in a muffle furnace and continuing to heat it at 850-900℃ for 30-40 minutes. After sufficient cooling, it is weighed on an electronic balance and the weight is recorded. This operation is repeated until a constant weight is obtained to obtain the mass of barium sulfate in the ash sample. The content of barium sulfate in the ash sample is calculated, and then the content of barium sulfate in the automotive brake pads is obtained. The calculation formula is as follows: Where m3 is the mass of the ash sample to be tested, m4 is the mass of the 100ml empty crucible, and m5 is the mass of the barium sulfate in the ash sample added to the crucible after being ignited to constant weight.

5. The method for accurately determining the barium sulfate content in automotive brake pads according to claim 1, characterized in that: After step S5, the product is subjected to infrared testing to obtain an infrared spectrum. The infrared spectrum is then used for qualitative analysis to verify whether the experimental product is barium sulfate.

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