Background
The paper-based friction material mainly comprises fibers, a binder, a filler, a regulator with friction performance and the like, wherein the paper-based friction material raw paper is manufactured by a papermaking method, and then the paper-based friction material is produced by resin impregnation. The paper-based friction material has been developed into a more and more important wet friction material which gradually replaces resin-based and metal-based friction materials due to the advantages of low production cost, stable dynamic friction factor, approximate dynamic/static friction factor ratio, stable bonding performance, low wear rate, long service life, low noise, capability of protecting dual materials and the like, and is applied to clutches in automobile transmission systems and brake pads in braking systems.
In order to improve the mechanical strength of the paper-based friction material and meet the requirement of high porosity of the paper-based friction material, the heat generated in the friction process can be taken away in time through pores by improving the thermal conductivity in the friction process, so that the heat loss of the friction material is reduced, and meanwhile, the friction performance is improved and the wear rate is reduced. The conventional friction performance fillers such as diatomite, carbon black and graphite are widely applied to the preparation of paper-based friction materials, but the porosity of the fillers is low and the fillers are easy to agglomerate, so that the performance of the friction materials is influenced.
The common paper-based friction material has the advantages that the reinforcing fiber is aramid fiber, and although the long-term stability is the most important characteristic of the aramid fiber, the aramid fiber has poor ultraviolet resistance; the aramid fiber contains amide groups, has strong polarity and is easy to absorb water, and when H in the amide groups is replaced by hydrophilic groups in certain solvents, the aramid fiber can more easily absorb water. Therefore, in the aramid fiber friction material, part of aramid fibers are exposed out of the upper surface and the lower surface of the material, so that the material has extremely strong water absorption capacity, and the material often has the problem of water seepage due to the damage of a surface layer and the generation of fine cracks. In addition, in a low-temperature environment, water absorbed by the aramid fiber friction material expands after being frozen, so that the bonding between the reinforcement and the matrix is damaged, and the performance of the paper-based friction material is greatly reduced.
The polyether-ether-ketone fiber (PEEK fiber) is a wholly aromatic fiber, has ether bonds and ketone bonds, has the moisture regain of only 0.1 percent, so that the high-temperature resistance, friction resistance and corrosion resistance of the fiber are obviously higher than those of aramid fiber, has extremely excellent comprehensive performance, is suitable for the forming and processing process of the traditional thermoplastic plastics, and becomes an ideal material in the fields of aerospace, energy and chemical industry, transportation, food processing, medical treatment, health care and the like. Under the condition of higher temperature, the polyether-ether-ketone fiber still has good friction and excellent self-lubricating property, and keeps outstanding wear rate and lower friction coefficient; in addition, the tensile strength can reach 700MPa, the modulus is 3-6 GPa, and due to the excellent performances of friction resistance, high temperature resistance, easy processing and the like, in the automobile industry, the composite material can be used for engine inner covers, automobile bearings, sealing elements, brake pads and the like.
Because the PEEK fiber has excellent performances such as friction resistance, high temperature resistance, corrosion resistance and the like, the PEEK fiber is applied in many fields, but still has some defects, because a PEEK molecular chain is rigid and nonpolar, the PEEK molecular chain has poor wettability with the fiber as a base material, the bonding force with the fiber is weak, for example, the average length of the fiber, the fiber content and the fiber distribution in a composite material obtained by adopting an injection molding process are uneven, or the friction resistance is poor, and the performance of the composite material is improved by adding a material for enhancing the strength in the prior art; CN105504670A discloses preparation of a polyimide fiber reinforced polyether-ether-ketone resin-based composite material, but the polyether-ether-ketone resin has poor wettability to polyimide fibers and weak binding force to fiber wrapping, so that the problems of insufficient interlayer strength, easy falling and the like of the composite material are caused; CN107245898A proposes that carbon fiber, polyether-ether-ketone fiber and plant fiber are mixed for papermaking of a resin-based friction material, but the fiber is not modified, the surface of the fiber is smooth, and the bonding strength is low; CN104927298A discloses a polyether imide (PEI) -coated carbon fiber reinforced polyether ether ketone resin-based wear-resistant composite material, but due to the surface inertness of the carbon fiber, the PEI is not much in coating amount on the surface and is easy to agglomerate, the PEI is unevenly distributed on the surface of the fiber, and the uniformity and the friction uniformity of the prepared wear-resistant material are poor. The prior patents have the problems of insufficient binding force between the friction filler and fiber and resin base materials, uneven pores and the like, and the mechanical property and the friction property of the material are reduced.
Therefore, the development of a polyetheretherketone fiber-based composite paper-based friction material with high porosity, good heat conductivity and excellent friction performance is required.
Disclosure of Invention
In order to solve the problems of low porosity, poor friction performance and the like in the existing patent, the invention provides a 3D-doped layered porous graphene sheet paper-based friction material and a preparation method thereof, the method provided by the invention is characterized in that polyether-ether-ketone fibers (PEEK fibers) are subjected to modification treatment, and the mechanical engagement or chemical combination among the fibers, friction fillers and resin is enhanced, so that the mechanical strength and the friction performance of the friction material are improved; the graphene serving as a novel filler has the advantages of high porosity, high mechanical strength and the like, and the three-dimensional (3D) layered porous graphene serving as an expression form of the graphene has many excellent characteristics of single-layer graphene, the specific self-supporting structure of the graphene can obviously reduce the agglomeration effect of the single-layer graphene, and the graphene is porous in the graphene, high in mechanical strength, large in specific surface area and very good in heat conduction performance, so that the 3D layered porous graphene can be widely applied to the fields of energy, materials, environment, sensing, capacitance and the like. The 3D layered porous graphene sheet is doped, and the polyetheretherketone fiber composite paper-based friction material is prepared by a papermaking process, has good friction resistance and stability, improves the porosity of the material, and retains the excellent high temperature resistance and mechanical properties of the paper-based material.
The first object of the invention is to provide a method for preparing a 3D-doped layered porous graphene sheet paper-based friction material, which comprises the following steps:
(1) Pretreating polyether-ether-ketone fibers, mixing the pretreated polyether-ether-ketone fibers with aramid pulp, defibering the mixture, adding a dispersing agent, a retention and filtration aid, a filler and a 3D layered porous graphene sheet, and stirring the mixture to obtain mixed slurry, wherein the addition amount of the 3D layered porous graphene sheet accounts for 0-1.0% of the mass of the mixed slurry, but is not 0;
(2) Carrying out wet forming, dewatering and drying treatment on the mixed slurry obtained in the step (1) to obtain raw paper of the friction material;
(3) And (3) dipping the base paper obtained in the step (2) in a resin solution, drying and hot-pressing to obtain the 3D-doped layered porous graphene sheet paper-based friction material.
In one embodiment of the invention, the 3D layered porous graphene sheets are added in an amount of 0.2% to 0.5% by mass of the mixed slurry.
In one embodiment of the invention, the 3D layered holey graphene sheets are added in an amount of 0.3% by mass of the mixed slurry.
In one embodiment of the present invention, the pretreatment of the polyetheretherketone fiber in step (1) is one of a coupling agent modification, an acid-base modification or a low-temperature plasma modification.
In one embodiment of the invention, the coupling agent is modified to: preparing a coupling agent solution with the solid content of 10-20%, adding polyether-ether-ketone fibers, sealing, standing for 0.5-3.0h, taking out, washing with water for 4-6 times, standing in water for 0.5-2 h, taking out, and drying at 60-90 ℃ for 10-12 h.
In one embodiment of the invention, the coupling agent is one of Y-aminopropyltriethoxysilane (KH 550), N-beta (aminoethyl) -Y-aminopropyltrimethoxysilane and anilinomethyltriethoxysilane.
In one embodiment of the present invention, the water is preferably deionized water.
In one embodiment of the present invention, the acid-base modification is: mixing polyether-ether-ketone fiber and 65% concentrated sulfuric acid according to the mass ratio of 1:4, uniformly stirring, treating for 10-30 min, then carrying out vacuum filtration to remove acid liquor, washing with water to be neutral, then drying at 90-110 ℃, and uniformly stirring.
In one embodiment of the present invention, the low temperature plasma is modified by: modifying the polyether-ether-ketone fiber by adopting a low-temperature plasma instrument and taking air as reaction gas, and setting and adjusting parameters under the conditions of temperature of 180-220 ℃ and relative humidity of 65% to: the pressure is 15-25 Pa, the time is 3-5 min, the power is 50-250W, and the polyether-ether-ketone fiber is processed.
In one embodiment of the invention, the mass ratio of the polyether-ether-ketone fibers to the aramid pulp in the step (1) is (2-6) to (8-4).
In one embodiment of the invention, the dispersant in step (1) is one or more of polyethylene oxide, carboxymethyl cellulose or tween; the reinforcing agent is one or more of styrene-butadiene latex, modified starch or resin adhesive; the retention and drainage aid is one or more of cationic polyacrylamide, chitosan or guar gum; the filler is graphite or a friction performance regulator, wherein the friction performance regulator comprises one or more of barium sulfate, kaolin or diatomite.
In one embodiment of the present invention, the resin in step (3) is a polyimide resin, a phenolic resin or an epoxy resin; the diluting reagent adopted in the resin solution is any one of N, N-dimethylacetamide, acetone, ethanol, toluene or xylene; the concentration of the resin solution is 2wt% -20 wt%.
In one embodiment of the present invention, the hot pressing in step (3) is roller hot pressing, and the process is as follows: 280-320 ℃, 0.3-1.0 MPa and the vehicle speed is 4-15 m/min. In one embodiment of the present invention, the preparation method specifically comprises:
(1) Fiber pretreatment: carrying out acid-base treatment modification, coupling agent treatment modification or low-temperature plasma treatment modification on the polyether-ether-ketone fiber;
(2) Mixing modified polyether-ether-ketone fibers and aramid pulp, wherein the mass ratio of the polyether-ether-ketone fibers to the aramid pulp is (2-6) to (8-4), defibering the mixture by using a defibering device for 10-30 min after mixing, adding a dispersing agent, a retention and filtration aid, a filler and a 3D layered porous graphene sheet, and stirring the mixture for 10-120 s to obtain mixed slurry, wherein the addition amounts of the dispersing agent, the retention and filtration aid and the filler respectively account for 0.05-1% of the mass of the mixed slurry, and the addition amount of the 3D layered porous graphene sheet accounts for 0-1.0% but is not 0% of the mass of the mixed slurry;
(3) And carrying out wet forming, dewatering and drying treatment on the mixed slurry to obtain the raw paper of the friction material.
(4) Diluting resin with a diluent to form a resin solution, dipping base paper in the resin solution, drying and hot-pressing to obtain the 3D-doped layered porous graphene sheet paper-based friction material.
The second purpose of the invention is to obtain the 3D-doped layered porous graphene sheet paper-based friction material prepared by the method.
The third purpose of the invention is to apply the doped 3D layered porous graphene sheet paper-based friction material in an engine inner cover, an automobile bearing, a sealing element or a brake pad.
The invention has the beneficial effects that:
(1) The novel doped 3D layered porous graphene sheet paper-based friction material is prepared by adopting a method combining wet papermaking forming and hot pressing treatment, and has the advantages of simple process flow, easiness in operation, controllable product quality and the like.
(2) The invention carries out chemical modification treatment on the surface of the adopted polyether-ether-ketone fiber, enhances the chemical activity and the surface performance of the polyether-ether-ketone fiber, enhances the binding capacity with resin, and enhances the wear resistance and the mechanical strength of the friction material.
(3) According to the invention, a mode of adding the 3D layered porous graphene sheet into the slurry is adopted, so that the wear resistance, the mechanical property and the thermal property are obviously enhanced while the cost is reduced.
(4) According to the invention, the modified polyether-ether-ketone fiber and the aramid pulp are uniformly mixed and dispersed, and the friction material base paper is manufactured by adding the 3D layered porous graphene sheet and using a wet papermaking method. The paper-based friction material with good friction performance is obtained by dipping in a resin solution, a three-dimensional porous network structure is formed, so that the friction resistance and stability are improved, and the excellent high-temperature resistance, mechanical property, flexibility and corrosion resistance of the paper-based material are retained.
Detailed Description
The test method comprises the following steps:
(1) The method for measuring the tensile index is measured according to the national standard GB/T2914-2008.
(2) The burst index is determined according to the national standard GB/T454-2002.
(3) The tear index is determined according to the national standard GB/T455-2002.
(4) According to the requirements of QC/T583-1999 method for testing the apparent porosity of the automobile brake lining, an oil absorption method is adopted to test the porosity of the sample, and the porosity is calculated according to the formula:
in the formula: p- -porosity,%;
G 1 -dry sample weight, g;
G 2 -weight in oil of saturated oil sample, g;
G 3 weight of saturated sample in air, g.
(5) And (3) measuring the friction coefficient:
the coefficient of dynamic friction is expressed by the following formula
Wherein: mu.s d -coefficient of dynamic friction;
M d moment of kinetic friction, nxm
P- -load of friction pair end face, N
R CP - -effective radius of the sample, cm
The coefficient of static friction is expressed by the following formula
Wherein: mu.s j -coefficient of static friction;
M j - -moment of static friction, nxm
P- -load of friction pair end face, N
R CP - -effective radius of the sample, cm
R 1 And R 2 Respectively is the excircle and the inner circle radius of the sample friction material, the unit: and cm.
(6) Formula for calculating wear rate:
Wherein: v- -wear rate, cm 3 /J;
A- -area of contact of sample, cm 2 ;
Delta h- -thickness difference, cm, before and after wear of friction material
n- -number of brake clutching
I 0 -total inertia of the tester, kg x m 2 ,I 0 Calculated by the following formula:
I 0 =I 1 +I 2
I 1 tester spindle inertia, I 1 =0.035kg×m 2
I 2 Tester configuration inertia, I 2 =0.2kg×m 2 。
Omega- -initial braking angular velocity, rad/s.
Example 1
A preparation method of a 3D-doped layered porous graphene sheet paper-based friction material is shown in figure 2 and comprises the following steps:
(1) Coupling agent modified pretreated polyether-ether-ketone fiber: preparing a coupling agent KH550 solution with the solid content of 20%, adding polyether-ether-ketone fibers, sealing a beaker by using a preservative film, placing the beaker in a fume hood for 1.5h, taking out the treated polyether-ether-ketone fibers, washing the treated polyether-ether-ketone fibers for 2 times by using tap water, standing the treated polyether-ether-ketone fibers in water for 0.5h, then placing the treated polyether-ether-ketone fibers in an electric heating constant-temperature drum type drying box for drying at the temperature of 80 ℃ for 12h, and placing the dried polyether-ether-ketone fibers in a sample bag for storage;
(2) Mixing the treated polyether-ether-ketone fibers with aramid pulp, adding 3D layered porous graphene sheets into the pulp, wherein the adding amount of the 3D layered porous graphene sheets accounts for 0.3% of the mass of the mixed pulp, and then preparing raw paper of the friction material by using a wet papermaking method;
(3) Preparing a polyimide resin solution with the concentration of 10% by using an N, N-dimethylacetamide solution, and stirring at a high speed to uniformly disperse; fully soaking raw paper of the friction material in a polyimide resin solution, drying and hot-pressing, wherein the hot-pressing process comprises the following steps: the temperature is 290 ℃, the pressure is 0.8MPa, and the vehicle speed is 5m/min, so that the 3D-doped layered porous graphene sheet paper-based friction material is obtained.
Example 2
A preparation method of a 3D-doped layered porous graphene sheet paper-based friction material comprises the following steps:
(1) Coupling agent modified pretreated polyether-ether-ketone fiber: preparing a coupling agent KH550 solution with the solid content of 20%, adding polyether-ether-ketone fibers, sealing a beaker by using a preservative film, placing the beaker in a fume hood for 1.5h, taking out the treated polyether-ether-ketone fibers, washing the treated polyether-ether-ketone fibers for 2 times by using tap water, standing the treated polyether-ether-ketone fibers in water for 0.5h, then placing the treated polyether-ether-ketone fibers in an electric heating constant-temperature drum type drying box for drying at the temperature of 80 ℃ for 12h, and placing the dried polyether-ether-ketone fibers in a sample bag for storage;
(2) Mixing the treated polyether-ether-ketone fibers with aramid pulp, adding 3D layered porous graphene sheets into the pulp, wherein the adding amount of the 3D layered porous graphene sheets accounts for 0.2% of the mass of the mixed pulp, and then preparing raw paper of the friction material by a wet papermaking method;
(3) Preparing a polyimide resin solution with the concentration of 10% by using an N, N-dimethylacetamide solution, and stirring at a high speed to uniformly disperse; fully soaking raw paper of the friction material in a polyimide resin solution, drying and hot-pressing, wherein the hot-pressing process comprises the following steps: the temperature is 290 ℃, the pressure is 0.8MPa, and the vehicle speed is 5m/min, so that the 3D-doped layered porous graphene sheet paper-based friction material is obtained.
Example 3
A preparation method of a 3D-doped layered porous graphene sheet paper-based friction material comprises the following steps:
(1) Coupling agent modified pretreated polyether-ether-ketone fiber: preparing a coupling agent KH550 solution with the solid content of 20%, adding polyether-ether-ketone fibers, sealing a beaker by using a preservative film, placing the beaker in a fume hood for 1.5h, taking out the treated polyether-ether-ketone fibers, washing the treated polyether-ether-ketone fibers for 2 times by using tap water, standing the treated polyether-ether-ketone fibers in water for 0.5h, then placing the treated polyether-ether-ketone fibers in an electric heating constant-temperature drum type drying box for drying at the temperature of 80 ℃ for 12h, and placing the dried polyether-ether-ketone fibers in a sample bag for storage;
(2) Mixing the treated polyether-ether-ketone fibers with aramid pulp, adding 3D layered porous graphene sheets into the pulp, wherein the adding amount of the 3D layered porous graphene sheets accounts for 0.4% of the mass of the mixed pulp, and then preparing raw paper of the friction material by a wet papermaking method;
(3) Preparing a polyimide resin solution with the concentration of 10% by using an N, N-dimethylacetamide solution, and stirring at a high speed to uniformly disperse; fully soaking raw paper of the friction material in a polyimide resin solution, drying and hot-pressing, wherein the hot-pressing process comprises the following steps: the temperature is 290 ℃, the pressure is 0.8MPa, and the vehicle speed is 5m/min, so that the 3D-doped layered porous graphene sheet paper-based friction material is obtained.
Example 4
A preparation method of a 3D-doped layered porous graphene sheet paper-based friction material comprises the following steps:
(1) Coupling agent modified pretreated polyether-ether-ketone fiber: preparing a coupling agent KH550 solution with the solid content of 20%, adding polyether-ether-ketone fibers, sealing a beaker by using a preservative film, placing the beaker in a fume hood for 1.5h, taking out the treated polyether-ether-ketone fibers, washing the treated polyether-ether-ketone fibers for 2 times by using tap water, standing the treated polyether-ether-ketone fibers in water for 0.5h, then placing the treated polyether-ether-ketone fibers in an electric heating constant-temperature drum type drying box for drying at the temperature of 80 ℃ for 12h, and placing the dried polyether-ether-ketone fibers in a sample bag for storage;
(2) Mixing the treated polyether-ether-ketone fibers with aramid pulp, adding 3D layered porous graphene sheets into the pulp, wherein the adding amount of the 3D layered porous graphene sheets accounts for 0.5% of the mass of the mixed pulp, and then preparing raw paper of the friction material by a wet papermaking method;
(3) Preparing a polyimide resin solution with the concentration of 10% by using an N, N-dimethylacetamide solution, and stirring at a high speed to uniformly disperse; fully soaking raw paper of the friction material in a polyimide resin solution, drying and hot-pressing, wherein the hot-pressing process comprises the following steps: the temperature is 290 ℃, the pressure is 0.8MPa, and the vehicle speed is 5m/min, so that the 3D-doped layered porous graphene sheet paper-based friction material is obtained.
Comparative example 1
A preparation method of an undoped 3D layered porous graphene sheet paper-based friction material comprises the following steps:
(1) Coupling agent modified pretreated polyether-ether-ketone fiber: preparing a coupling agent KH550 solution with the solid content of 20%, adding polyether-ether-ketone fibers, sealing a beaker by using a preservative film, placing the beaker in a fume hood for 1.5h, taking out the treated polyether-ether-ketone fibers, washing the treated polyether-ether-ketone fibers for 2 times by using tap water, standing the treated polyether-ether-ketone fibers in water for 0.5h, then placing the treated polyether-ether-ketone fibers in an electric heating constant-temperature drum type drying box for drying at the temperature of 80 ℃ for 12h, and placing the dried polyether-ether-ketone fibers in a sample bag for storage;
(2) Mixing the treated polyether-ether-ketone fiber with aramid pulp, and preparing raw paper of the friction material by a wet papermaking method;
(3) Preparing a polyimide resin solution with the concentration of 10wt% by using an N, N-dimethylacetamide solution, and stirring at a high speed to uniformly disperse; fully soaking raw paper of the friction material in a polyimide resin solution, drying and hot-pressing, wherein the hot-pressing process comprises the following steps: the temperature is 290 ℃, the pressure is 0.8MPa, and the vehicle speed is 5m/min, so that the undoped 3D layered porous graphene sheet paper-based friction material is obtained.
Comparative example 2
A preparation method of an undoped 3D layered porous graphene sheet paper-based friction material comprises the following steps:
(1) Acid-base modification pretreatment of polyether-ether-ketone fibers: mixing polyether-ether-ketone fibers and 65% concentrated sulfuric acid according to the mass ratio of 1:4, uniformly stirring, treating for 30min, then carrying out vacuum filtration to remove acid liquor, washing with deionized water to be neutral, then drying at 105 ℃, and uniformly stirring for later use;
(2) Mixing the treated polyether-ether-ketone fiber with aramid pulp, and preparing raw paper of the friction material by a wet papermaking method;
(3) Preparing a polyimide resin solution with the concentration of 10% by using an N, N-dimethylacetamide solution, and stirring at a high speed to uniformly disperse; fully soaking raw paper of the friction material in a polyimide resin solution, drying and hot-pressing, wherein the hot-pressing process comprises the following steps: the temperature is 290 ℃, the pressure is 0.8MPa, and the vehicle speed is 5m/min, so that the undoped 3D layered porous graphene sheet paper-based friction material is obtained.
Comparative example 3
A preparation method of an undoped 3D layered porous graphene sheet paper-based friction material comprises the following steps:
(1) Modification at low-temperature plasma: modifying the polyether-ether-ketone fibers by using a low-temperature plasma instrument and taking air as reaction gas, and setting and adjusting parameters to the following values under the conditions of temperature of 200 ℃ and relative humidity of 65%: processing the sample at the air pressure of 20Pa, the time of 3min and the power of 100W for later use;
(2) Mixing the treated polyether-ether-ketone fiber with aramid pulp, and preparing raw paper of the friction material by a wet papermaking method;
(3) Preparing a polyimide resin solution with the concentration of 5% by using an N, N-dimethylacetamide solution, and stirring at a high speed to uniformly disperse; fully soaking base paper of the poly friction material in a polyimide resin solution, drying and hot-pressing, wherein the hot-pressing process comprises the following steps: the temperature is 290 ℃, the pressure is 0.8MPa, and the vehicle speed is 5m/min, so that the undoped 3D layered porous graphene sheet paper-based friction material is obtained.
Example 5
A preparation method of a 3D-doped layered porous graphene sheet paper-based friction material comprises the following steps:
(1) Coupling agent modified pretreated polyether-ether-ketone fiber: preparing a coupling agent KH550 solution with the solid content of 20%, adding polyether-ether-ketone fibers, sealing a beaker by using a preservative film, placing the beaker in a fume hood for 1.5h, taking out the treated polyether-ether-ketone fibers, washing the treated polyether-ether-ketone fibers for 2 times by using tap water, standing the treated polyether-ether-ketone fibers in water for 0.5h, then placing the treated polyether-ether-ketone fibers in an electric heating constant-temperature drum type drying box for drying at the temperature of 80 ℃ for 12h, and placing the dried polyether-ether-ketone fibers in a sample bag for storage;
(2) Mixing the treated polyether-ether-ketone fibers with aramid pulp, adding 3D layered porous graphene sheets into the pulp, wherein the adding amount of the 3D layered porous graphene sheets accounts for 0.1% of the mass of the mixed pulp, and then preparing raw paper of the friction material by a wet papermaking method;
(3) Preparing a polyimide resin solution with the concentration of 10% by using an N, N-dimethylacetamide solution, and stirring at a high speed to uniformly disperse; fully soaking raw paper of the friction material in a polyimide resin solution, drying and hot-pressing, wherein the hot-pressing process comprises the following steps: the temperature is 290 ℃, the pressure is 0.8MPa, and the vehicle speed is 5m/min, so that the 3D-doped layered porous graphene sheet paper-based friction material is obtained.
Comparative example 4
A preparation method of a doped diatomite paper-based friction material comprises the following steps:
(1) Coupling agent modified pretreated polyether-ether-ketone fiber: preparing a coupling agent KH550 solution with the solid content of 20%, adding polyether-ether-ketone fibers, sealing a beaker by using a preservative film, placing the beaker in a fume hood for 1.5h, taking out the treated polyether-ether-ketone fibers, washing the treated polyether-ether-ketone fibers for 2 times by using tap water, standing the treated polyether-ether-ketone fibers in water for 0.5h, then placing the treated polyether-ether-ketone fibers in an electric heating constant-temperature drum type drying box for drying at the temperature of 80 ℃ for 12h, and placing the dried polyether-ether-ketone fibers in a sample bag for storage;
(2) Mixing the treated polyether-ether-ketone fiber with aramid pulp, adding diatomite powder into the pulp, wherein the addition amount of the diatomite accounts for 0.3% of the mass of the mixed pulp, and preparing raw paper of the friction material by a wet papermaking method;
(3) Preparing a polyimide resin solution with the concentration of 10% by using an N, N-dimethylacetamide solution, and stirring at a high speed to uniformly disperse; fully soaking raw paper of the friction material in a polyimide resin solution, drying and hot-pressing, wherein the hot-pressing process comprises the following steps: the temperature is 290 ℃, the pressure is 0.8MPa, and the vehicle speed is 5m/min, thus obtaining the doped diatomite paper-based friction material.
Comparative example 5
A preparation method of a doped graphite paper-based friction material comprises the following steps:
(1) Coupling agent modified pretreated polyether-ether-ketone fiber: preparing a coupling agent KH550 solution with the solid content of 20%, adding polyether-ether-ketone fibers, sealing a beaker by using a preservative film, placing the beaker in a fume hood for 1.5h, taking out the treated polyether-ether-ketone fibers, washing the treated polyether-ether-ketone fibers for 2 times by using tap water, standing the treated polyether-ether-ketone fibers in water for 0.5h, then placing the treated polyether-ether-ketone fibers in an electric heating constant-temperature drum type drying box for drying at the temperature of 80 ℃ for 12h, and placing the dried polyether-ether-ketone fibers in a sample bag for storage;
(2) Mixing the treated polyether-ether-ketone fiber with aramid pulp, adding graphite powder into the pulp, wherein the adding amount of 3 graphite accounts for 0.3% of the mass of the mixed pulp, and preparing raw paper of the friction material by a wet papermaking method;
(3) Preparing a polyimide resin solution with the concentration of 10% by using an N, N-dimethylacetamide solution, and stirring at a high speed to uniformly disperse; fully soaking raw paper of the friction material in a polyimide resin solution, drying and hot-pressing, wherein the hot-pressing process comprises the following steps: the temperature is 290 ℃, the pressure is 0.8MPa, and the vehicle speed is 5m/min, thus obtaining the doped graphite paper base friction material.
The properties of the (non-) doped 3D layered porous graphene sheet paper-based friction materials prepared according to the methods of examples 1-5 and comparative examples 1-5 are shown in table 1 below, and the paper-based friction materials prepared according to examples 1-5 are doped with different concentrations of 3D layered porous graphene sheet paper-based friction materials, and the properties of the paper-based friction materials are the best when the concentration is 0.3%. When the doping concentration is too high, the friction performance may be reduced due to uneven dispersion of graphene. Comparative examples 1 to 3 show that different modification methods have different influences on the performance of the friction material, wherein the amino coupling agent modification has the most obvious improvement on the performance of the undoped 3D layered porous graphene sheet paper-based friction material.
TABLE 1 data of performance test of (non) doped 3D layered porous graphene sheet paper-based friction material prepared in examples and comparative examples
Although the present invention has been described with reference to the preferred embodiments, it should be understood that various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.