A brake pad capable of reducing brake disc wear and a preparation process thereof

Abstract

The present application relates to the technical field of brake pad, and particularly relates to a brake pad capable of reducing brake disc wear and a preparation process thereof, the brake pad is composed of the following components in percentage by weight: reinforcing fiber 20-32%, binder 12-18%, friction modifier 22-34%, filler and functional additive 24-38%, and the reinforcing fiber is at least one of titanium carbide coated carbon fiber, steel fiber and aluminum silicate ceramic fiber. In the present application, the reinforcing fiber constructs a high-strength heat conduction network, disperses heat quickly to reduce thermal stress concentration; the binder guarantees structural stability under high temperature; the friction modifier optimizes the friction coefficient curve through lubrication and synergistic effect of friction increasing, and avoids high temperature fluctuation; the filler and functional additive enhance the heat absorption and buffering capacity, and adjust the porosity to relieve thermal shock. The synergistic effect of the components can reduce brake disc thermal cracks, and improve the crack resistance and braking stability under extreme working conditions.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of brake pads, in particular to a brake pad capable of reducing brake disc wear and a preparation process thereof. BACKGROUND

[0002] In the field of high-performance braking, especially in track driving, heavy commercial and extreme mountain working conditions, the brake disc is prone to thermal stress concentration due to frequent braking, which easily causes thermal cracks, seriously affecting braking safety and service life. Although the traditional brake pad can meet the basic braking requirements, it has obvious shortcomings in heat management capability, friction stability and material compatibility. For example, the local hotspot temperature rises sharply during friction, causing fatigue cracks in the brake disc due to thermal expansion and contraction; the friction coefficient fluctuates sharply with temperature, which easily causes thermal shock; at the same time, some brake pads contain hard abrasives, which aggravate the wear of the brake disc and further shorten its service life.

[0003] At present, in order to improve the performance of the brake pad, carbon fiber is often used to enhance heat conduction, graphite is used to improve lubrication, or a composite binder is used to enhance high-temperature stability, but single optimization is difficult to balance multi-dimensional requirements. For example, although increasing the content of carbon fiber can improve the heat conduction, the fiber itself is not wear-resistant, which easily produces free abrasion and destroys the stability of the friction film. Using a single lubricant cannot cover the lubrication requirements in a wide temperature range, and the friction coefficient rises sharply at high temperatures. And ordinary binders are easily softened at extreme temperatures, causing deformation of the brake pad structure and further aggravating the decay of braking performance.

[0004] Therefore, it is the key to solve the problem of brake disc thermal cracks to develop and design a brake pad that can optimize heat management, stabilize friction performance and be friendly to the brake disc. SUMMARY

[0005] In view of the problems in the prior art, the present application provides a brake pad capable of reducing brake disc wear and a preparation process thereof, so that the prepared brake pad has good heat conduction and heat dissipation, wear resistance and stable friction film, high temperature resistance, small thermal deformation, low expansion coefficient, balanced lubrication and friction without damaging the brake disc, and other comprehensive performances.

[0006] To achieve the above purpose, the present application realizes the following technical scheme:

[0007] The present application discloses a brake pad capable of reducing brake disc wear, the composition of the brake pad is as follows in terms of weight percentage: reinforcing fiber 20-32%, binder 12-18%, friction modifier 22-34%, filler and functional additive 24-38%, and the reinforcing fiber is at least one of titanium carbide coated carbon fiber, steel fiber and aluminum silicate ceramic fiber.

[0008] By setting the above technical scheme, the reinforcing fibers construct a high-strength heat-conducting network, quickly disperse heat to reduce thermal stress concentration; the binder ensures the stability of the structure at high temperature; the friction modifier optimizes the friction coefficient curve through the synergistic effect of lubrication and friction increase, avoiding high-temperature fluctuations; the filler and functional additives enhance the heat absorption and buffering capacity, adjust the porosity to relieve thermal shock. The synergistic effect of various components can reduce brake disc thermal cracks, improve the crack resistance and braking stability under extreme conditions.

[0009] Preferably, the composition of the reinforcing fibers is as follows, in terms of weight percentage of the total components: titanium carbide coated carbon fiber 10%-15%, tin-plated steel fiber 8%-12%, and aluminum silicate ceramic fiber 2%-5%.

[0010] By setting the above technical scheme, the carbon fibers in the titanium carbide coated carbon fibers provide high thermal conductivity, quickly disperse friction heat, and the titanium carbide coating layer improves wear resistance, avoiding unstable friction film caused by fiber wear. The tin-plated steel fiber (thermal conductivity 50 W / (m·K)) constructs the main heat channel. The aluminum silicate ceramic fiber is resistant to high temperature, inhibits thermal deformation of the material at high temperature, and reduces the overall thermal expansion coefficient. The three components synergistically reduce thermal stress concentration and thermal deformation, helping to reduce brake disc thermal cracks and improve braking stability.

[0011] Preferably, the preparation method of the titanium carbide coated carbon fiber is as follows: immerse PAN-based carbon fibers in a 8%-12% titanium tetrachloride ethanol solution, ultrasonic dispersion for 20-30 min, take out and dry in an 80-100℃ oven for 1-2 h, then heat to 800-900℃ at a rate of 5℃ / min under nitrogen protection, keep for 2-3 h, naturally cool, and cut to 3-5 mm long titanium carbide coated carbon fibers.

[0012] By setting the above technical scheme, this preparation method uses titanium tetrachloride ethanol solution immersion and ultrasonic dispersion to make titanium tetrachloride uniformly adhere to the surface of PAN-based carbon fibers; 80-100℃ drying removes the solvent, ensuring sufficient subsequent reaction; calcination at 800-900℃ under nitrogen protection forms a 50-100 nm titanium carbide coating layer, balancing high thermal conductivity and wear resistance, and cutting to 3-5 mm facilitates subsequent mixing, so that the titanium carbide coated carbon fiber has excellent properties of efficient heat dissipation and stable friction film.

[0013] Preferably, the composition of the friction modifier is as follows, in terms of weight percentage of the total components: high crystallinity flake graphite 12%-16%, tungsten disulfide-boron nitride composite lubricant 5%-8%, tin sulfide-iron oxide composite friction modifier 4%-7%, and potassium titanate whisker 1%-3%, wherein the high crystallinity flake graphite has a particle size of 50-100 μm, and the tin sulfide-iron oxide composite friction modifier is a particle with a particle size of 1-5 μm, which is obtained by mixing tin sulfide and iron oxide at a mass ratio of 1:1.

[0014] By setting the above technical scheme, high crystallinity flake graphite (particle size 50-100 μm) can form a continuous lubricating film at high temperature, reduce the fluctuation of friction coefficient and assist transverse heat conduction. The tungsten disulfide-boron nitride composite lubricant can provide stable lubrication performance; the tin sulfide-iron oxide composite friction modifier can provide a mild friction effect and avoid scratching the brake disc by hard particles. The tin sulfide-iron oxide composite friction modifier (mass ratio 1:1, particle size 1-5 μm) can stabilize the medium-high temperature friction coefficient, and the mild friction of iron oxide avoids scratching the brake disc.

[0015] Preferably, the preparation method of the tungsten disulfide-boron nitride composite lubricant is as follows: tungsten disulfide and hexagonal boron nitride are weighed according to a mass ratio of 2:1, put into a ball mill, 99.5% anhydrous ethanol is added according to a liquid-solid ratio of 3:1, and ball milling is carried out at a speed of 300-400 r / min for 2-4 h, followed by vacuum drying and sieving through a 200-mesh screen to obtain the tungsten disulfide-boron nitride composite lubricant.

[0016] By setting the above technical scheme, the tungsten disulfide and hexagonal boron nitride are uniformly dispersed in anhydrous ethanol, and vacuum drying and sieving ensure uniform particle size. The obtained tungsten disulfide-boron nitride composite lubricant can form a gradient lubrication system at 300-800℃, stabilize the friction coefficient, reduce the wear on the brake disc, and improve the high-temperature lubrication performance.

[0017] Preferably, the particle size of the tungsten disulfide is 1-3 μm, the particle size of the hexagonal boron nitride is 50-100 nm, the vacuum drying temperature is 60-80℃, and the vacuum drying time is 8-10 h.

[0018] By setting the above technical scheme, the particle size of the tungsten disulfide and hexagonal boron nitride is matched to form a "particle-flake" synergistic structure and enhance the continuity of lubrication; vacuum drying at 60-80℃ can completely remove ethanol without damaging the structure of the components, and sufficient drying can avoid solvent residues affecting the lubrication performance, thereby ultimately improving the lubrication stability and durability of the composite lubricant in a wide temperature range.

[0019] Preferably, the composition of the fillers and functional additives is as follows, based on the weight percentage of the total components: nano-zinc tin alloy powder 3%-6%, porous silica supported magnesium microspheres 4%-8%, silane coupling agent modified barium sulfate 15%-20%, and magnesium carbonate-titanate composite pore agent 2%-4%.

[0020] The preparation method of the porous magnesium oxide-loaded silica microspheres is as follows: porous silica microspheres are prepared by a template method, the microspheres are immersed in a magnesium nitrate solution with a concentration of 5%-8%, ultrasonic treatment is performed for 15-20 min, then drying is performed at 100-120 ℃ for 4-6 h, and then calcination is performed at 500-600 ℃ for 2-3 h, and after natural cooling, the product is gently ground with a corundum mortar and sieved through a 100-mesh sieve, to obtain porous magnesium oxide-loaded silica microspheres with a magnesium oxide loading of 8%-12% of the mass of the microspheres.

[0021] By setting the above technical solution, the porous structure of the porous magnesium oxide-loaded silica microspheres can buffer thermal stress (reduce thermal shock by 30%), and magnesium oxide is released at high temperature and reacts with friction products to form a stable magnesium-iron oxide friction film; so that the brake pad has good heat conduction and heat dissipation, is wear-resistant and has a stable friction film. The method prepares porous silica microspheres by a template method, magnesium ions are uniformly introduced into the pores by magnesium nitrate immersion and ultrasonic treatment, and after drying and calcination, magnesium oxide-loaded microspheres are formed. The porous structure can buffer thermal stress, and magnesium oxide is released at high temperature and reacts with friction products to form a stable friction film, thereby ensuring the heat shock resistance and friction stability of the brake pad.

[0022] Preferably, the nano zinc-tin alloy powder is prepared by mixing zinc and tin at a mass ratio of 3:1 to form particles with a particle size of 50-100 nm; and the porous silica microspheres have a particle size of 5-10 μm and a pore size of 100-200 nm.

[0023] By setting the above technical solution, the particle size and pore size of the porous silica microspheres are designed to ensure that they are uniformly dispersed in the brake pad matrix and provide sufficient pore volume to load magnesium oxide. A suitable pore size facilitates the uniform entry and stable loading of magnesium ions, the porous structure can effectively buffer thermal stress and reduce thermal shock, and at the same time provides space for the reaction of magnesium oxide with friction products, thereby assisting the formation of a stable friction film and improving the thermal fatigue resistance and friction stability of the brake pad.

[0024] Preferably, the adhesive is composed of cashew nut shell oil-silicon rubber modified phenolic resin 10%-14% and polyimide resin 2%-4%, and in the cashew nut shell oil-silicon rubber modified phenolic resin, cashew nut shell oil accounts for 15%-20% and silicon rubber accounts for 5%-8%.

[0025] By setting the above technical solution, the cashew nut shell oil-silicon rubber modified phenolic resin can provide room temperature toughness and medium temperature adhesion, and the polyimide resin (Tg>300 ℃) ensures the structural stability at high temperature, and the residual carbon rate is >60%. The cashew nut shell oil-silicon rubber modified phenolic resin and the polyimide resin are compounded as the adhesive, and the adhesive has good room temperature toughness and medium temperature adhesion.

[0026] The application also discloses a preparation process of a brake pad capable of reducing brake disc wear.

[0027] S1, the cashew shell oil-silicon rubber modified phenolic resin is broken into 5-10mm particles, mixed with polyimide resin in proportion, preheated in an oven at 60-80 DEG C for 1-2h, and standby;

[0028] S2, the titanium carbide coated carbon fiber, tinned steel fiber, aluminum silicate ceramic fiber, silane coupling agent modified barium sulfate, potassium titanate whisker are added into a high-speed mixer, and pre-mixed at a speed of 600-900r / min for 8-12min;

[0029] S3, the high crystallinity flake graphite, tungsten disulfide-boron nitride composite lubricant, tin sulfide-iron oxide composite friction modifier and nano zinc tin alloy powder are added into the mixture obtained in S2, and continue to mix at a speed of 600-900r / min for 5-8min;

[0030] S4, the porous silica magnesium microspheres, magnesium carbonate-titanate composite pore agent and the binder preheated in S1 are added into the mixture obtained in S3, mixed at 900-1000r / min for 12-15min, and then the mixture is added into a brake pad making mold preheated to 80 DEG C, and pre-pressed at a pressure of 15-25MPa for 60-80s, to obtain a preform;

[0031] S5, the preform is placed in a hot-pressing mold, and hot-pressed at 160-190 DEG C and 35-55MPa for 8-12min, and then demoulded after pressure holding and cooling to 70 DEG C;

[0032] S6, the molded brake pad is placed in an oven, heated to 200-240 DEG C at a rate of 5-8 DEG C / min, and then cooled to room temperature after heat preservation for 5-7h, and then subjected to grinding processing, cleaning and brushing of rust-proof oil.

[0033] By setting the above technical scheme, the process ensures uniform dispersion of each component through step-by-step mixing, and the preheating of the binder can enhance the compatibility; the combination of pre-pressing and hot-pressing guarantees the density of the material, and the hot-pressing and heat treatment parameters promote the full crosslinking of the resin, improve the structural strength and high-temperature stability; the post-processing guarantees the dimensional accuracy and rust-proof performance, and finally obtains a brake pad with good heat dissipation, stable friction, wear resistance and crack resistance, etc. The mold is preheated to 80 DEG C, which can avoid the premature curing of the binder caused by the sudden temperature drop when the mixture contacts the low-temperature mold, ensure the good fluidity of the material during the pre-pressing process, facilitate the material to fully fill the mold cavity, and improve the density and structural uniformity of the preform, laying a foundation for the stability of subsequent hot-pressing and the consistency of brake pad performance.

[0034] The beneficial effects of the present application are:

[0035] The carbon fiber in the titanium carbide coated carbon fiber provides high thermal conductivity, quickly disperses friction heat, and the titanium carbide coating layer improves wear resistance to avoid unstable friction film caused by fiber self-wear; steel fiber (thermal conductivity 50 W / (m·K)) constructs a main heat conduction channel; aluminum silicate ceramic fiber is high-temperature resistant, inhibits thermal deformation of the material at high temperature, and reduces the overall thermal expansion coefficient; modified phenolic resin and polyimide resin are compounded as a binder, which has good room temperature toughness and medium temperature bonding force; flake graphite forms a continuous lubricating film at high temperature; tungsten disulfide-boron nitride composite lubricant can provide stable lubrication performance; composite friction modifier can provide a mild friction effect to avoid scratching the brake disc by hard particles; the porous structure of magnesium-loaded porous silica microspheres can buffer thermal stress (reduce thermal shock by 30%), and magnesium oxide is released at high temperature to react with the friction product to form a stable magnesium-iron oxide friction film; so that the brake pad has good heat conduction and heat dissipation, is wear-resistant and has a stable friction film, is high-temperature resistant, has small thermal deformation, has a low expansion coefficient, is balanced in lubrication and friction, does not damage the brake disc, and can buffer thermal stress and form a stable friction film.

[0036] Steel fiber constructs a main heat conduction channel, a tin plating layer (melting point 232℃) melts to form a lubricating film at high temperature, reducing scratches on the brake disc. High-crystallinity flake graphite can form a continuous lubricating film at high temperature, reducing the fluctuation of the friction coefficient, while assisting in lateral heat conduction. Tin sulfide stabilizes the medium and high temperature friction coefficient (200-500℃), and iron oxide (Mohs hardness 5-6) provides a mild friction effect to avoid scratching the brake disc by hard particles. Cashew nut shell oil-silicon rubber modified phenolic resin can provide room temperature toughness and medium temperature bonding force, and polyimide resin (Tg>300℃) ensures the structural stability at high temperature, with a residual carbon rate of >60%. The combined action of each component makes the brake pad have the advantages of high heat dissipation, stable friction, mild friction performance, high toughness, and stable structure.

[0037] Titanium carbide coated carbon fiber, tin plated steel fiber, and flake graphite form a three-dimensional heat conduction network, which, in combination with the endothermic action of silane coupling agent modified barium sulfate (heat capacity 1.2 kJ / (kg·K)), increases the diffusion area of friction heat by >50% within 1s, and reduces the local maximum temperature by 150-200℃.

[0038] The basic lubricating film of flake graphite, the high-temperature lubricating phase of tungsten disulfide-boron nitride, and the friction phase of tin sulfide-iron oxide cooperate to form a dynamic balance system of lubrication and friction, so that the friction coefficient is stable at 0.35-0.45 (fluctuation rate <8%) in the range of 100-600℃, avoiding thermal shock caused by sudden rise of μ value. The microporous structure (porosity 5-8%) formed by magnesium carbonate-titanate can buffer thermal expansion stress and reduce the risk of thermal fatigue cracks. DETAILED DESCRIPTION

[0039] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0040] Embodiment 1: This embodiment discloses a brake pad capable of reducing brake disc wear, and the composition of the brake pad is as follows in terms of weight percentage: titanium carbide coated carbon fiber 15%, tinned steel fiber 8%, aluminum silicate ceramic fiber 5%, cashew nut shell oil-silicon rubber modified phenolic resin 10%, polyimide resin 2%, high crystallinity flake graphite 12%, tungsten disulfide-boron nitride composite lubricant 8%, tin sulfide-iron oxide composite friction modifier 6%, nano zinc-tin alloy powder 3%, porous silica supported magnesium microsphere 8%, silane coupling agent modified barium sulfate 20%, magnesium carbonate-titanate composite pore agent 2% and potassium titanate whisker 1%.

[0041] In the cashew nut shell oil-silicon rubber modified phenolic resin, the cashew nut shell oil accounts for 15%, and the silicon rubber accounts for 5%. The high crystallinity flake graphite has a particle size of 50 μm. The composite friction modifier is a particle material with a particle size of 1 μm, which is formed by mixing tin sulfide and iron oxide at a mass ratio of 1:1. The nano zinc-tin alloy powder is a particle material with a particle size of 50 nm, which is formed by mixing zinc and tin at a mass ratio of 3:1.

[0042] The preparation method of the titanium carbide coated carbon fiber is as follows: PAN-based carbon fiber is immersed in a 8% titanium tetrachloride ethanol solution, ultrasonic dispersion is performed for 20 min, then the carbon fiber is taken out and dried in an 80℃ oven for 1 h, then the temperature is raised to 800℃ at a rate of 5℃ / min under nitrogen protection, and the temperature is kept for 2 h, and then the titanium carbide coated carbon fiber is cut to a length of 3 mm after natural cooling.

[0043] The preparation method of the tungsten disulfide-boron nitride composite lubricant is as follows: tungsten disulfide with a particle size of 1 μm and hexagonal boron nitride with a particle size of 50 μm are weighed at a mass ratio of 2:1, put into a ball mill, 99.5% anhydrous ethanol is added at a liquid-solid ratio of 3:1, and ball milling is performed at a speed of 300 r / min for 2 h, then drying is performed at 60℃ under vacuum conditions for 8 h, and then the tungsten disulfide-boron nitride composite lubricant is obtained by passing through a 200 mesh sieve.

[0044] The preparation method of the porous magnesium-loaded silica microspheres is as follows: porous silica microspheres with a particle size of 5 μm and a pore size of 100 nm are prepared by a template method, the microspheres are immersed in a magnesium nitrate solution with a concentration of 5%, ultrasonic treatment is performed for 15 min, then the microspheres are dried at 100 ℃ for 4 h and calcined at 500 ℃ for 2 h, and after natural cooling, the microspheres are gently ground with an agate mortar and sieved through a 100-mesh sieve, to obtain porous magnesium-loaded silica microspheres with a magnesium oxide loading of 8% of the mass of the microspheres.

[0045] The preparation process of the brake pad capable of reducing brake disc wear is also disclosed in the embodiment, which comprises the following steps:

[0046] S1, the cashew nut shell oil-silicone rubber modified phenolic resin is broken into 5 mm particles, mixed with polyimide resin in proportion, preheated in a 60℃ oven for 1 h, and reserved;

[0047] S2, the titanium carbide coated carbon fiber, tinned steel fiber, aluminum silicate ceramic fiber, silane coupling agent modified barium sulfate and potassium titanate whisker are added into a high-speed mixer and pre-mixed at a speed of 600 r / min for 8 min;

[0048] S3, the high crystallinity flake graphite, tungsten disulfide-boron nitride composite lubricant, tin sulfide-iron oxide composite friction modifier and nano zinc tin alloy powder are added into the mixture obtained in S2, and the mixture is continuously mixed at a speed of 600 r / min for 5 min;

[0049] S4, the porous magnesium-loaded silica microspheres, magnesium carbonate-titanate composite pore agent and the binder preheated in S1 are added into the mixture obtained in S3, and the mixture is mixed at a speed of 900 r / min for 12 min, then the mixture is added into a brake pad manufacturing mold preheated to 80℃, and pre-pressed at a pressure of 15 MPa for 60 s to obtain a preformed blank;

[0050] S5, the preformed blank is placed in a hot-pressing mold and hot-pressed at 160℃ and 35 MPa for 8 min, and demolded after pressure holding and cooling to 70℃;

[0051] S6, the formed brake pad is placed in an oven, heated to 200℃ at a rate of 5℃ / min, and cooled to room temperature after heat preservation for 5 h, then the brake pad is subjected to grinding processing, cleaning and brushing of anti-rust oil.

[0052] Example 2: This example discloses a brake pad capable of reducing brake disc wear, the composition of the brake pad is as follows in percentage by weight: titanium carbide coated carbon fiber 10%, tinned steel fiber 10%, aluminum silicate ceramic fiber 5%, cashew nut shell oil-silicon rubber modified phenolic resin 14%, polyimide resin 4%, high crystallinity flake graphite 12%, tungsten disulfide-boron nitride composite lubricant 8%, tin sulfide-iron oxide composite friction modifier 5%, nano zinc-tin alloy powder 6%, porous silica supported magnesium microspheres 4%, silane coupling agent modified barium sulfate 15%, magnesium carbonate-titanate composite pore agent 4% and potassium titanate whisker 3%.

[0053] In the cashew nut shell oil-silicon rubber modified phenolic resin, cashew nut shell oil accounts for 20%, and silicon rubber accounts for 8%. The particle size of the high crystallinity flake graphite is 100 μm, the composite friction modifier is a particle size of 5 μm of a mixture of tin sulfide and iron oxide in a mass ratio of 1:1, and the nano zinc-tin alloy powder is a particle size of 100 nm of a mixture of zinc and tin in a mass ratio of 3:1.

[0054] The preparation method of the titanium carbide coated carbon fiber is as follows: PAN-based carbon fiber is immersed in a 12% titanium tetrachloride ethanol solution, ultrasonic dispersion is performed for 30 min, then it is taken out and dried in an oven at 100℃ for 2h, then it is heated to 900℃ at a rate of 5℃ / min under nitrogen protection, and kept for 3h, and then naturally cooled and cut into 5mm long titanium carbide coated carbon fibers.

[0055] The preparation method of the tungsten disulfide-boron nitride composite lubricant is as follows: 3 μm particle size tungsten disulfide and 100 nm particle size hexagonal boron nitride are weighed in a mass ratio of 2:1, put into a ball mill, 99.5% anhydrous ethanol is added in a liquid-solid ratio of 3:1, ball milling is performed at a speed of 400 r / min for 4h, then dried at 80℃ under vacuum conditions for 10h, and then sieved through a 200 mesh sieve to obtain the tungsten disulfide-boron nitride composite lubricant.

[0056] The preparation method of the porous silica supported magnesium microspheres is as follows: porous silica microspheres with a particle size of 10 μm and a pore size of 200 nm are prepared by a template method, the microspheres are immersed in an 8% magnesium nitrate solution, ultrasonic treatment is performed for 20 min, then dried at 120℃ for 6h, calcined at 600℃ for 3h, naturally cooled, gently ground with a agate mortar, and sieved through a 100 mesh sieve to obtain the porous silica supported magnesium microspheres with a magnesium oxide loading of 12% of the mass of the microspheres.

[0057] This example also discloses a preparation process of a brake pad capable of reducing brake disc wear, which comprises the following steps:

[0058] S1, crush the cashew nut shell oil-silicon rubber modified phenolic resin into 10 mm particles, mix with the polyimide resin in proportion, preheat in an oven at 80℃ for 2h, and reserve;

[0059] S2, the titanium carbide coated carbon fiber, tinned steel fiber, aluminum silicate ceramic fiber, silane coupling agent modified barium sulfate, potassium titanate whisker is added into the high-speed mixer, and is premixed at a rotating speed of 900 r / min for 12 min;

[0060] S3, the high crystallinity flake graphite, tungsten disulfide-boron nitride composite lubricant, tin sulfide-iron oxide composite friction modifier and nano zinc tin alloy powder are added into the mixture obtained in S2, and the mixing is continued at a rotating speed of 900 r / min for 8 min;

[0061] S4, the porous silica supported magnesium microspheres, magnesium carbonate-titanate composite pore agent and the binder after the preheating treatment in S1 are added into the mixture obtained in S3, and the mixing is carried out at 1000 r / min for 15 min, and then the mixture is added into a brake pad manufacturing mold which is preheated to 80℃, and is pre-pressed at a pressure of 25 MPa for 80 s to obtain a preformed blank;

[0062] S5, the preformed blank is placed in a hot pressing mold, and is hot pressed at 190℃ and 55 MPa for 12 min, and is demolded after the pressure holding and cooling to 70℃;

[0063] S6, the molded brake pad is placed in an oven, and is heated to 240℃ at a rate of 8℃ / min, and is kept at the temperature for 7 h, and is cooled to room temperature, and then is subjected to grinding processing, cleaning and brushing of rust-proof oil.

[0064] In the example 3, the composition of the brake pad capable of reducing the wear of the brake disc is as follows in terms of weight percentage: titanium carbide coated carbon fiber 12%, tinned steel fiber 12%, aluminum silicate ceramic fiber 2%, cashew nut shell oil-silicon rubber modified phenolic resin 11%, polyimide resin 3%, high crystallinity flake graphite 13%, tungsten disulfide-boron nitride composite lubricant 6%, tin sulfide-iron oxide composite friction modifier 7%, nano zinc tin alloy powder 4%, porous silica supported magnesium microspheres 5%, silane coupling agent modified barium sulfate 20%, magnesium carbonate-titanate composite pore agent 3% and potassium titanate whisker 2%.

[0065] In the cashew nut shell oil-silicon rubber modified phenolic resin, the cashew nut shell oil accounts for 17%, and the silicon rubber accounts for 6%. The high crystallinity flake graphite has a particle size of 75 μm, the composite friction modifier is a particle material with a particle size of 3 μm which is obtained by mixing tin sulfide and iron oxide at a mass ratio of 1:1, and the nano zinc tin alloy powder is a particle material with a particle size of 75 nm which is obtained by mixing zinc and tin at a mass ratio of 3:1.

[0066] The preparation method of the titanium carbide coated carbon fiber is as follows: the PAN-based carbon fiber is immersed in a 10% titanium tetrachloride ethanol solution, ultrasonic dispersion is performed for 25 min, then the carbon fiber is taken out and dried in an oven at 90℃ for 1.5 h, then the temperature is raised to 850℃ at a rate of 5℃ / min under nitrogen protection, and the temperature is kept for 2.5 h, and then the titanium carbide coated carbon fiber with a length of 4 mm is obtained after natural cooling and shearing.

[0067] The preparation method of the tungsten disulfide-boron nitride composite lubricant is as follows: 2 μm tungsten disulfide and 75 nm hexagonal boron nitride are weighed according to a mass ratio of 2:1, put into a ball mill, 99.5% anhydrous ethanol is added according to a liquid-solid ratio of 3:1, ball milling is performed at a speed of 350 r / min for 3 h, then drying is performed at 70℃ under vacuum for 9 h, and the tungsten disulfide-boron nitride composite lubricant is obtained after being sieved through a 200 mesh screen.

[0068] The preparation method of the porous magnesium-loaded silica microsphere is as follows: the porous silica microsphere with a particle size of 7 μm and a pore size of 150 nm is prepared by a template method, the microsphere is immersed in a 6% magnesium nitrate solution, ultrasonic treatment is performed for 17 min, then drying is performed at 110℃ for 5 h, calcination is performed at 550℃ for 2.5 h, the magnesium oxide-loaded porous silica microsphere with a magnesium oxide loading amount of 10% of the mass of the microsphere is obtained after natural cooling and gentle grinding with a jasper mortar and sieving through a 100 mesh screen.

[0069] The embodiment also discloses a preparation process of the brake pad capable of reducing brake disc wear.

[0070] S1, the cashew nut shell oil-silicon rubber modified phenolic resin is broken into 7 mm particles, mixed with the polyimide resin according to a proportion, preheated in an oven at 70℃ for 1.5 h, and used as needed;

[0071] S2, the titanium carbide coated carbon fiber, tinned steel fiber, aluminum silicate ceramic fiber, silane coupling agent modified barium sulfate, and potassium titanate whisker are added into a high-speed mixer, and pre-mixed at a speed of 750 r / min for 10 min;

[0072] S3, the high crystallinity flake graphite, tungsten disulfide-boron nitride composite lubricant, tin sulfide-iron oxide composite friction modifier, and nano zinc-tin alloy powder are added into the mixture obtained in S2, and the mixture is continuously mixed at a speed of 750 r / min for 6 min;

[0073] S4, the porous magnesium-loaded silica microsphere, magnesium carbonate-titanate composite pore agent, and the binder preheated in S1 are added into the mixture obtained in S3, and the mixture is mixed at a speed of 950 r / min for 14 min, then the mixture is added into a brake pad manufacturing mold preheated to 80℃, and pre-pressed at a pressure of 20 MPa for 70 s, so as to obtain a preformed blank.

[0074] S5, the preform is placed in a hot pressing mold, hot pressed at 180℃, 45MPa for 10min, pressure holding and cooling to 70℃, then demolding;

[0075] S6, the molded brake pad is placed in an oven, heated to 220℃ at a rate of 6℃ / min, kept for 6h, then cooled to room temperature, followed by grinding processing, cleaning and brushing anti-rust oil.

[0076] Comparative Example 1:

[0077] A brake pad capable of reducing brake disc wear, the difference between the brake pad and Example 3 is only that no titanium carbide coated carbon fiber is added, and the rest of the components are proportionally expanded to a total component content of 100%.

[0078] Comparative Example 2:

[0079] A brake pad capable of reducing brake disc wear, the difference between the brake pad and Example 3 is only that no tungsten disulfide-boron nitride composite lubricant is added, and the rest of the components are proportionally expanded to a total component content of 100%.

[0080] Comparative Example 3:

[0081] A brake pad capable of reducing brake disc wear, the difference between the brake pad and Example 3 is only that no porous silica magnesium-loaded microspheres are added, and the rest of the components are proportionally expanded to a total component content of 100%.

[0082] Comparative Example 4:

[0083] A brake pad capable of reducing brake disc wear, the difference between the brake pad and Example 3 is only that ordinary carbon fiber is directly used instead of titanium carbide coated carbon fiber.

[0084] Comparative Example 5:

[0085] A brake pad capable of reducing brake disc wear, the difference between the brake pad and Example 3 is only that the polyimide resin is replaced with cashew nut shell oil-silicon rubber modified phenolic resin.

[0086] Comparative Example 6:

[0087] A brake pad capable of reducing brake disc wear, the difference between the brake pad and Example 3 is only that ordinary graphite is directly used instead of high crystallinity flaky graphite.

[0088] Comparative Example 7:

[0089] A brake pad capable of reducing brake disc wear, the difference between the brake pad and Example 3 is only that the tin sulfide-iron oxide composite friction modifier is replaced with antimony sulfide.

[0090] Comparative Example 8:

[0091] A brake pad capable of reducing brake disc wear, the difference between the brake pad and Example 3 is only that no potassium titanate whiskers are added, and the rest of the components are proportionally expanded to a total component content of 100%.

[0092] Comparative Example 9:

[0093] A brake pad capable of reducing brake disc wear, the difference between the brake pad and Example 3 is only that aluminum oxide is directly used to replace potassium titanate whiskers.

[0094] Comparative Example 10:

[0095] A brake pad capable of reducing brake disc wear, the difference between the brake pad and Example 3 is only that ordinary barium sulfate is directly used to replace silane coupling agent modified barium sulfate.

[0096] The brake pads obtained in Examples 1-3 and Comparative Examples 1-10 are subjected to performance tests of braking inertia qualified times, thermal conductivity, thermal expansion coefficient, friction coefficient, and brake disc wear amount, wherein:

[0097] (I) Inertia bench test (reference SAE J3080 standard)

[0098] Equipment: Inertia brake test bench (equipped with infrared temperature measuring instrument, crack detector);

[0099] Sample: Brake pad (size 150x50x10mm), gray cast iron brake disc (diameter 300mm, thickness 20mm);

[0100] Steps:

[0101] Set the braking inertia to 1300 and 1600, the initial speed to 100km / h, and the deceleration to 0.6g;

[0102] Each braking is 30s apart, and the cumulative braking is 1000 times (1300 inertia) or 700 times (1600 inertia);

[0103] Measure the brake disc surface crack length / quantity every 100 times, and when a single crack is >10mm or the total area ratio is >75%, it is judged to be unqualified, and the qualified times are recorded.

[0104] (II) Thermal conductivity test (reference GB / T22588-2008)

[0105] Equipment: Hot-wire method thermal conductivity instrument (precision ±3%);

[0106] Sample: 10mmx10mmx5mm brake pad;

[0107] Steps:

[0108] Hot-wire probe (diameter 0.5mm) was vertically embedded in the center of the sample, and a constant heat flow of 10W / m was applied;

[0109] The temperature change curve within 10-60s was recorded, and the formula λ=Q / (4πΔT) x ln(t2 / t1) was used to calculate (λ is the thermal conductivity, Q is the heat flux density, ΔT is the temperature difference, and t is the time).

[0110] (Three) thermal expansion coefficient test (reference GB / T1036-2008)

[0111] Equipment: thermal mechanical analyzer (TMA, heating rate 10℃ / min);

[0112] Sample: 20mm x 5mm x 5mm brake pad;

[0113] Steps:

[0114] In the range of room temperature to 300℃, the length change ΔL was measured;

[0115] The formula α=ΔL / (L0 x ΔT) was used to calculate (α is the thermal expansion coefficient, L0 is the initial length, and ΔT is the temperature change).

[0116] (Four) friction coefficient test (reference GB5763-2018)

[0117] Equipment: constant speed friction tester (rotation speed 1000-3000r / min);

[0118] Steps:

[0119] The temperature was raised from 100℃ to 600℃ (5min constant temperature per 100℃);

[0120] The friction force F at different temperatures was recorded, and the formula μ=F / N was used to calculate (μ is the friction coefficient, F is the friction force, and N is the normal pressure 500N);

[0121] Friction coefficient stability=(1-|μ_max-μ_min| / μ_avg) x 100% (wherein μ_max is the maximum friction coefficient, μ_min is the minimum friction coefficient, and μ_avg is the average friction coefficient).

[0122] (Five) brake disc wear amount test

[0123] Equipment: laser profilometer (accuracy 0.1μm);

[0124] Steps:

[0125] The roughness Ra of the brake disc surface in 3 regions was measured before and after the brake test;

[0126] Wear = Ra average after test - Ra average before test.

[0127] The results are shown in Table 1.

[0128] Table 1 Performance parameters of brake pads obtained in Examples 1-3 and Comparative Examples 1-10

[0129]

[0130] From Table 1, relative to Example 3:

[0131] In Comparative Example 1, the number of qualified times of 1300 braking inertia decreased by 390 times, the thermal conductivity decreased by 50%, and the wear of the brake disc increased by 176%. It may be because: titanium carbide coated carbon fiber has high thermal conductivity and wear resistance, and after the loss of three-dimensional thermal conduction network, the friction heat cannot be quickly dispersed, the local hotspot temperature rises sharply, resulting in dense cracks on the brake disc due to thermal stress concentration; at the same time, without the protection of the titanium carbide coating layer, the fiber directly rubs with the brake disc, which aggravates the mechanical wear of the disc surface, resulting in a large increase in wear.

[0132] In Comparative Example 2, the number of qualified times of 1600 braking inertia decreased by 44.3%, the friction coefficient stability decreased from 96% to 77%, and the wear of the brake disc increased by 190%. It may be because: molybdenum disulfide provides stable lubrication at medium-high temperature (300-600°C), and boron nitride provides stable lubrication at ultra-high temperature (>800°C), and the two cooperate to maintain the stability of the friction coefficient. After the loss, the friction coefficient fluctuates violently at high temperature, a large amount of heat is generated instantaneously, causing thermal shock and accelerating the formation of cracks on the brake disc; at the same time, the discontinuous lubricating film causes the brake pad to directly engage with the brake disc, resulting in irregular wear on the friction interface, which greatly increases the wear of the brake disc.

[0133] In Comparative Example 3, the number of qualified times of 1300 braking inertia decreased by 410 times, and the thermal expansion coefficient increased from 6.1 to 9.5 x 10 -6 / ℃. It may be because: the porous structure of the porous silica loaded with magnesium microspheres can buffer thermal stress, and the loaded magnesium oxide can react with the friction products to form a stable friction film. After the loss, the stress of the material cannot be effectively released during the thermal cycle, and the brake disc produces fatigue cracks due to repeated thermal expansion and cold contraction; at the same time, the continuity of the friction film is destroyed, resulting in uneven wear of the brake disc, and the number of qualified times decreases significantly.

[0134] In Comparative Example 4, the qualified number of 1600 braking inertia was reduced by 47.1%, and the brake disc wear increased by 204%. It may be because: the ordinary carbon fiber lacks a titanium carbide coating layer, not only the thermal conductivity decreases, but also the wear resistance is insufficient, and it is easy to wear and produce free abrasive dust in the friction process. These abrasive dust can scratch the surface of the brake disc and form crack initiation points; at the same time, the reduction of thermal conductivity leads to heat accumulation, further aggravating the thermal damage of the brake disc, resulting in a decrease in the qualified number and an increase in wear.

[0135] In Comparative Example 5, the qualified number of 1300 braking inertia was reduced by 500 times, and the high-temperature structural stability decreased by 30%. It may be because: in the composite binder, the polyimide resin can maintain structural stability at high temperature (> 250℃), and cooperates with the modified phenolic resin to provide good bonding force. The single cashew nut shell oil-silicon rubber modified phenolic resin is easy to soften at high temperature, resulting in deformation of the brake pad structure and damage to the integrity of the friction film; at the same time, the insufficient bonding strength makes the material prone to delamination during repeated braking, further reducing the braking performance and resulting in a significant decrease in the qualified number.

[0136] In Comparative Example 6, the qualified number of 1300 braking inertia was reduced by 460 times, the thermal conductivity decreased from 38.8 to 24.2 W / (m·K), and the brake disc wear increased by 216%. It may be because: high crystallinity flake graphite has excellent lubricity and thermal conductivity, and can form a continuous and stable lubricating film on the friction interface and assist heat conduction. The low crystallinity of ordinary graphite makes the lubricating film prone to breakage, resulting in an increase in friction coefficient fluctuations and an inability to diffuse the generated heat in time; at the same time, the decrease in lubrication effect increases the direct friction between the brake pad and the brake disc, aggravating the wear of the brake disc and reducing the qualified number.

[0137] In Comparative Example 7, the brake disc wear increased by 250%, and the friction coefficient stability decreased by 25%. It may be because: the tin sulfide-iron oxide composite friction modifier can moderately and stably increase the friction coefficient, avoiding friction fluctuations. Although antimony sulfide can increase friction, it is prone to decomposition at high temperatures to produce hard particles that can scratch the surface of the brake disc and form a large number of micro-cracks; at the same time, its friction-increasing effect is unstable, resulting in an increase in friction coefficient fluctuations and further accelerating the damage to the brake disc, resulting in a significant increase in wear.

[0138] In Comparative Example 8, the qualified number of 1300 braking inertia was reduced by 480 times, and the brake disc wear increased by 230%. It may be because: potassium titanate whiskers can enhance the bending strength of the material and improve the continuity of the friction film. Without them, the structural strength of the material decreases, and deformation occurs during braking, damaging the stability of the friction film; the discontinuity of the friction film leads to uneven stress on the surface of the brake disc, resulting in local severe wear and further producing cracks, significantly reducing the qualified number.

[0139] In the comparative example 9, the brake disc wear increased by 264%, and the friction coefficient stability decreased to 70%. It may be because: the hardness of alumina is high (Mohs hardness 9), which can seriously scratch the surface of the brake disc and form a large number of crack initiation points; at the same time, its friction increasing effect is too violent, which leads to the increase of friction coefficient fluctuation, and the generated heat cannot be evenly dispersed, further aggravating the thermal damage and mechanical wear of the brake disc, so that all performance indicators are greatly reduced.

[0140] In the comparative example 10, the number of qualified times of 1300 braking inertia decreased by 450 times, and the thermal conductivity decreased from 38.8 to 26.5 W / (m·K). It may be because: the silane coupling agent modified barium sulfate has higher heat capacity and thermal conductivity, which can effectively absorb and conduct friction heat. The performance of ordinary barium sulfate is poor, which cannot absorb transient heat in time, resulting in local temperature being too high, and the brake disc is easy to produce thermal cracks; at the same time, the lack of heat conduction ability makes heat accumulation, further reduces the crack resistance of the material, resulting in a decrease in the number of qualified times.

[0141] In summary, the present application significantly improves the thermal conductivity and friction stability of the brake pad by the synergistic effect of titanium carbide coated carbon fiber, tungsten disulfide-boron nitride composite lubricant and other key components, and greatly reduces the wear and crack risk of the brake disc. Each comparative example shows that the performance is greatly reduced if any core component is missing, which proves that the formula is crucial for realizing the synergy of "low wear and high crack resistance".

[0142] The above examples are only used to illustrate the technical solutions of the present application, but not limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A brake pad capable of reducing brake disc wear, characterized in that, The brake pads are composed of the following components by weight percentage: 10%-15% titanium carbide-coated carbon fiber, 8%-12% tin-plated steel fiber, 2%-5% aluminum silicate ceramic fiber, 12%-18% binder, 12%-16% highly crystalline flake graphite, 5%-8% tungsten disulfide-boron nitride composite lubricant, 4%-7% tin sulfide-iron oxide composite friction enhancer, 1%-3% potassium titanate whiskers, 3%-6% nano zinc-tin alloy powder, 4%-8% porous silica-supported magnesium microspheres, 15%-20% silane coupling agent-modified barium sulfate, and 2%-4% magnesium carbonate-titanium ester composite pore agent.

2. The brake pads that reduce brake disc wear according to claim 1, characterized in that, The preparation method of titanium carbide coated carbon fiber is as follows: PAN-based carbon fiber is immersed in a titanium tetrachloride ethanol solution with a concentration of 8%-12%, ultrasonically dispersed for 20-30 minutes, taken out, and dried in an oven at 80-100℃ for 1-2 hours. Then, under nitrogen protection, the temperature is raised to 800-900℃ at a rate of 5℃ / min and held for 2-3 hours. After natural cooling, it is cut into titanium carbide coated carbon fibers with a length of 3-5 mm.

3. The brake pads that reduce brake disc wear according to claim 1, characterized in that, The highly crystalline flake graphite has a particle size of 50-100μm, and the tin sulfide-iron oxide composite friction modifier is made by mixing tin sulfide and iron oxide in a mass ratio of 1:1 to form particles with a particle size of 1-5μm.

4. The brake pads that reduce brake disc wear according to claim 1, characterized in that, The preparation method of tungsten disulfide-boron nitride composite lubricant is as follows: Weigh tungsten disulfide and hexagonal boron nitride at a mass ratio of 2:1, put them into a ball mill, add 99.5% anhydrous ethanol at a liquid-solid ratio of 3:1, ball mill at a speed of 300-400 r / min for 2-4 h, then vacuum dry, and pass through a 200 mesh sieve to obtain tungsten disulfide-boron nitride composite lubricant.

5. The brake pads capable of reducing brake disc wear according to claim 4, characterized in that, The particle size of tungsten disulfide is 1-3 μm, and the particle size of hexagonal boron nitride is 50-100 nm. The vacuum drying temperature is 60-80℃ and the time is 8-10 h.

6. The brake pads capable of reducing brake disc wear according to claim 1, characterized in that, The preparation method of porous silica magnesium-loaded microspheres is as follows: porous silica microspheres are prepared by template method. The microspheres are immersed in a 5%-8% magnesium nitrate solution, ultrasonically treated for 15-20 min, dried at 100-120℃ for 4-6 h, calcined at 500-600℃ for 2-3 h, and naturally cooled. They are then gently ground with an agate mortar and passed through a 100-mesh sieve to obtain porous silica magnesium-loaded microspheres with a magnesium oxide loading of 8%-12% of the microsphere mass.

7. The brake pads capable of reducing brake disc wear according to claim 6, characterized in that, Nano zinc-tin alloy powder is made by mixing zinc and tin in a mass ratio of 3:1, resulting in particles with a diameter of 50-100nm; porous silica microspheres have a particle size of 5-10μm and a pore size of 100-200nm.

8. The brake pads capable of reducing brake disc wear according to claim 6, characterized in that, The adhesive composition is as follows, based on the weight percentage of the total components: 10%-14% cashew nut shell oil-silicone rubber modified phenolic resin and 2%-4% polyimide resin; in the cashew nut shell oil-silicone rubber modified phenolic resin, cashew nut shell oil accounts for 15%-20% and silicone rubber accounts for 5%-8%.

9. A manufacturing process for brake pads capable of reducing brake disc wear based on claim 8, characterized in that, It includes the following steps: S1. Crush cashew shell oil-silicone rubber modified phenolic resin into 5-10mm particles, mix with polyimide resin in a certain proportion, and preheat in an oven at 60-80℃ for 1-2 hours for later use. S2. Add titanium carbide-coated carbon fiber, tin-plated steel fiber, aluminum silicate ceramic fiber, silane coupling agent modified barium sulfate, and potassium titanate whiskers to a high-speed mixer and premix for 8-12 minutes at a speed of 600-900 r / min. S3. Add highly crystalline flake graphite, tungsten disulfide-boron nitride composite lubricant, tin sulfide-iron oxide composite friction modifier and nano zinc-tin alloy powder to the mixture obtained in S2, and continue to mix at a speed of 600-900 r / min for 5-8 min. S4. Add porous silica magnesium microspheres, magnesium carbonate-titanium ester composite pore agent and binder preheated in S1 to the mixture obtained in S3. Mix at 900-1000 r / min for 12-15 min. Then add the mixture to a brake pad manufacturing mold preheated to 80℃ and pre-press it under 15-25 MPa pressure for 60-80 s to obtain a preform. S5. Place the preform in a hot press mold and hot press for 8-12 minutes at 160-190℃ and 35-55MPa. After holding the pressure and cooling down to 70℃, demold. S6. Place the molded brake pads in an oven and heat them to 200-240℃ at a rate of 5-8℃ / min. After holding at this temperature for 5-7 hours, cool them to room temperature in the oven. Then, grind, clean, and coat the brake pads with anti-rust oil to obtain the final product.

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