Preparation method of aramid phenolic resin composite material

Abstract

The application belongs to the technical field of composite materials, and particularly relates to a preparation method of aramid fiber / phenolic resin composite material. The aramid fiber is modified by plasma, two-component treatment of silane coupling agent polysulfane alcohol, sol-gel method coating of titanium dioxide, and then butyronitrile rubber and aluminum hydroxide are added to prepare modified phenolic resin. The modified aramid fiber, the modified phenolic resin and other components are mixed and then subjected to mold pressing and heating treatment, so that the aramid fiber / phenolic resin composite material has excellent mechanical properties, friction coefficient and wear resistance, and has outstanding industrial application value.

Description

Technical Field

[0001] This invention belongs to the field of composite material technology, and specifically relates to a method for preparing aramid phenolic resin composite materials. Background Technology

[0002] Phenolic resin-based friction materials are widely used in automotive braking systems due to their excellent mechanical strength and cost advantages. However, they have inherent defects under high-temperature conditions. When the temperature is above 250℃, the hydroxymethyl groups in the resin molecular chain undergo oxidative cracking, leading to severe thermal degradation; the rigid aromatic ring structure in the cured network results in generally low shear strength and high brittleness; and resin carbonization at high temperatures leads to interfacial failure and high wear rate.

[0003] Aramid fiber, as a fiber filler with high chemical stability, thermal stability, high mechanical properties and wear resistance, can improve the high-temperature mechanical properties and wear resistance of the prepared friction material when added to a phenolic resin matrix, thereby increasing the service life of the friction material.

[0004] Chinese patent document with publication number CN119683903A discloses a low-metal friction material for racing cars, its preparation method, brake pads, and applications. The method involves mechanically blending phenolic resin-modified stainless steel, composite rubber, lubricating materials, friction-enhancing materials, and fillers, followed by cold pressing to obtain the friction material. However, this method only modifies fibers through a single-component silane coupling agent, resulting in poor interfacial bonding between the fibers and the phenolic resin. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing aramid-phenolic resin composite materials. This method can significantly optimize the bonding between aramid fibers and phenolic resin and the interface, as well as the dispersibility of other components, thereby achieving a comprehensive improvement in the mechanical properties, friction coefficient, and wear resistance of the composite material, and possessing outstanding industrial application value.

[0006] To achieve this objective, the present invention provides a method for preparing an aramid phenolic resin composite material, comprising the following steps:

[0007] (1) The aramid fiber was subjected to plasma treatment and then immersed in an ethanol aqueous solution containing silane coupling agent and polythiol for 10-30 min to obtain modified aramid fiber.

[0008] (2) Tetrabutyl titanate, ethanol, water and acetylacetone are mixed to obtain a gel. Modified aramid fibers are placed in the gel and ultrasonically oscillated to obtain modified aramid fibers with titanium dioxide loaded on the surface.

[0009] (3) Cashew oil modified phenolic resin, nitrile rubber, and nano aluminum hydroxide are mixed and extruded into granules to obtain modified phenolic resin;

[0010] (4) Modified aramid fiber, steel fiber, barium sulfate, flake graphite and surface-aminated nanodiamond are blended in one stage; then modified phenolic resin is added and the temperature and speed are increased for a second stage of blending; then the temperature and speed are increased for a third stage of blending to obtain a composite matrix; the temperature and speed increase refers to increasing the mixing temperature and the speed of the mixer.

[0011] (5) The composite matrix is ​​molded, cured, and heated to obtain an aramid phenolic resin composite material.

[0012] Preferably, in step (1), the plasma atmosphere is argon, the gas flow rate is 50~80 sccm, the cavity pressure is 30~50 Pa, the power is 200~500 W, and the processing time is 1~3 min.

[0013] Preferably, in step (1), the silane coupling agent is one of silane coupling agent KH-560 or silane coupling agent A-187, and the polythiol is one of pentaerythritol tetra(3-mercaptopropionate) or trimethylolpropane tri(3-mercaptopropionate); the pH of the ethanol aqueous solution is 3~4; the mass ratio of ethanol, water, silane coupling agent and polythiol in the ethanol aqueous solution containing silane coupling agent and polythiol is 150~240:100:4~7.5:1.25~3; and the immersion time in the ethanol aqueous solution containing silane coupling agent and polythiol is 10~30 min.

[0014] Preferably, in step (2), the mass ratio of tetrabutyl titanate, ethanol, water and acetylacetone is 10:15~25:0.3~0.7:0.2~0.4; the oscillation treatment temperature is 70~90℃ and the oscillation treatment time is 25~35min.

[0015] Preferably, in step (3), the mass ratio of cashew oil modified phenolic resin, nitrile rubber, and nano aluminum hydroxide is 1:0.25~0.667:0.05~0.1.

[0016] Preferably, in step (4), the mass ratio of modified aramid fiber, modified phenolic resin, steel fiber, barium sulfate, flake graphite, and surface-aminated nanodiamond is 0.75~0.857:1:0.5~0.57:0.25~0.428:0.15~0.214:0.083~0.1; the first-stage blending temperature is 40~50℃, the rotation speed is 800~1000rpm, and the time is 3~5min; the second-stage blending temperature is 55~65℃, the rotation speed is 1200~1500rpm, and the time is 2~3min; the third-stage blending temperature is 65~75℃, the rotation speed is 1800~2200rpm, and the time is 4~6min.

[0017] Preferably, in step (5), the conditions for the mold curing are 4-6 min of molding at 110-130℃, 8-12 MPa, followed by 10-20 min of molding at 160-180℃, 25-35 MPa.

[0018] Preferably, in step (5), the heat treatment is a step heat treatment, which is first heating at 190-210℃ for 1.5-2.5 h, and then heating at 220-240℃ for 0.75-1.25 h.

[0019] The beneficial effects of the present application are as follows:

[0020] (1) The present application modifies aramid fibers by argon plasma treatment, silane coupling agent and polythiol impregnation, and sol-gel method loading titanium dioxide. The argon plasma treatment generates -COOH / -NH2 active groups on the surface of aramid fibers, and forms micro-etching grooves, which increases the specific surface area of the aramid fiber surface, and improves the coverage of silane coupling agent and polythiol. The epoxy group of silane coupling agent and the mercapto group of polythiol can form double reactive sites, which increases the surface energy of aramid fibers, so that more TiO2 coating prepared by sol-gel method can be covered on the aramid fibers. The TiO2 coating is converted into rutile phase by heat treatment in step (5), and forms Ti-O-C chemical bond with the resin, which increases the interfacial bonding force between aramid fibers and phenolic resin. In addition, rutile TiO2 can block the contact between air and phenolic resin, and inhibit the oxidative cracking of phenolic resin, which improves the mechanical strength of the composite material and reduces the thermal degradation rate of the composite material.

[0021] (2) The present application mixes cashew oil modified phenolic resin, nitrile rubber and nano aluminum hydroxide, and extrudes and granulates to obtain modified phenolic resin. The cashew nut shell oil modified phenolic resin serves as a rigid skeleton, the nitrile rubber forms an "island-in-sea" structure with the rigid skeleton in the double screw shearing field, and the nitrile rubber serves as a flexible region, which can absorb the energy of silver streak expansion, reduce the crack propagation rate, and increase the mechanical strength of the composite material. At the same time, the nano aluminum hydroxide fills the interface and plays a role of crack deflection and bridging between phenolic resin and nitrile rubber. The long fatty chain structure of cashew nut shell oil can be inserted into the aromatic ring network of phenolic resin, promote molecular chain slipping, improve the shear strength of the modified phenolic resin matrix, and further increase the mechanical strength of the composite material. The energy of external force acting on the composite material is absorbed through the deformation of the rubber phase and the crack deflection of the nano particles, which can improve the mechanical strength and wear resistance of the composite material.

[0022] (3) The present application adds flaky graphite and surface aminated nanodiamond as a friction modifier, the surface amino of the aminated nanodiamond reacts with the resin hydroxymethyl to form a C-N-C network as a protective film to improve the friction coefficient of the composite material when the temperature is greater than 250 DEG C; meanwhile, the flaky graphite and nanodiamond generate a diamond-like carbon film during the friction process, and the surface silanized steel fiber constructs a three-dimensional heat conduction path to make the friction heat quickly spread and improve the heat decay resistance of the composite material.

[0023] (4) The present application triggers deep reaction and promotes interface bonding through step heat treatment; at 190~210 DEG C, the resin beta relaxation movement rearranges the molecular chain to release the mold residual stress; at 220~240 DEG C, the aramid macromolecular chain segment slips to fill the microcracks; meanwhile, the phenolic resin is secondarily cured at high temperature and the interface reaction between aramid and phenolic resin occurs; and the TiO2 coating is converted from amorphous phase to rutile phase during heat treatment, and forms Ti-O-C chemical bond with the resin to improve the mechanical strength of the composite material; single temperature cannot achieve all the above goals; if only low temperature is used, the interface reaction and TiO2 phase change cannot be completed, and the material high temperature performance is insufficient; if high temperature is directly used, the internal residual stress and unreacted small molecules of the material will cause the product to foam, deform or even crack due to rapid reaction; the step heating follows the kinetics of material reaction, and gradually stimulates the performance of the material, which is an essential process to ensure the high stability of the composite material. It needs to be further explained that the titanium dioxide synthesized by the "soft chemistry" method such as hydrothermal method and sol-gel method sometimes grows in "metastable state", which is more sensitive to phase change; under the action of acetylacetone, it guides the ordered condensation and forms a stable complex with titanium ions; by controlling the ratio of ethanol / water, a porous gel with high specific surface area is formed, and the generated anatase phase system of titanium dioxide is at a local energy minimum value but not at a global minimum value, so it can be reorganized into a more stable rutile phase by overcoming a small energy barrier; and its initial particle size is at the nanometer level, the nanoparticles have extremely high specific surface area and surface energy, and the atomic arrangement is extremely unstable, so the phase change driving force is large, and therefore the thermodynamic potential barrier required for phase change is greatly weakened; therefore, part of the anatase phase titanium dioxide is converted into rutile phase titanium dioxide during the subsequent heat treatment process.

[0024] (5) The present application uniformly mixes each component with different morphology, density and surface properties by adjusting the time, temperature and rotation speed of blending in step (4), realizes good impregnation of resin on the reinforcing fiber and filler, and lays a foundation for subsequent molding. In the dry mixing stage (blending at 40-50 DEG C, 800-1000 rpm for 3-5 min), the temperature prevents aramid fibers from sticking due to high temperature, wrapping other particles, resulting in mixing failure, and the stirring speed is sufficient to provide the necessary shear force to dissociate steel fiber groups, disperse aramid fiber bundles and separate agglomerates of flake graphite and nano-diamond, and the fiber will not be excessively sheared and broken due to high stirring speed. This time ensures that all dry components are uniformly distributed macroscopically; in the resin impregnation stage (blending at 55-65 DEG C, 1200-1500 rpm for 2-3 min), the resin starts to melt at this temperature, the viscosity decreases significantly, and the fluidity increases, so that it can effectively flow and wrap the surface of each fiber and each particle, forming a good interfacial bond, and higher speed provides stronger shear force, which can quickly impregnate and coat other components with molten resin, preventing the resin from agglomerating itself; in the homogenization stage (blending at 65-75 DEG C, 1800-2200 rpm for 4-6 min), the temperature can meet the final mixing in the state of complete resin melting and lowest viscosity, and the best fluidity and dispersion effect are obtained, and at this speed, high shear force completely disperses residual small agglomerates, especially nano-sized fillers, further peeling and dispersing fibers, ensuring that each fiber is fully isolated and coated with resin, so that the material reaches a highly homogeneous state, avoiding uneven performance of subsequent products; three-stage mixing is a progressive process; if only one stage of mixing is used, either uniform dispersion cannot be achieved, or resin degradation or fiber damage occurs due to high temperature and high speed too early; this process ensures that the composite matrix has a uniform microstructure before molding, ensuring that the composite material has excellent performance. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 XRD pattern of aramid phenolic resin composite material prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0026] In the description of the present application, it is necessary to note that the specific conditions are not indicated in the examples, which are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The plasma equipment used in the present application is a Pico low pressure oxygen plasma equipment manufactured by Diener Electronic, Germany, with a radio frequency power of 0-1000 W, a vacuum degree of 1-100 Pa, and a gas flow of 0-100 sccm; the double screw extruder is a ZSK18 MEGALab double screw extruder manufactured by Coperion, Germany, with a screw diameter of 18 mm, a length-diameter ratio (L / D) of 40:1, a maximum temperature of 450℃, a screw rotation speed of 0-1200 rpm, and a torque of ≥20 Nm; the paddle mixer is a Littleford MGT-200 paddle mixer manufactured by Littleford, USA, with a rotation speed of 0-2200 rpm. Other reagents or instruments not indicated by the manufacturer are conventional products that can be purchased on the market.

[0027] The technical solutions provided by the present application will be described clearly and completely in combination with the specific embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application. Example 1

[0028] The aramid fiber was placed in an argon plasma equipment, the power was adjusted to 300 W, the cavity pressure was 40 Pa, and the gas flow was 65 sccm, and the treatment time was 2 min; then it was immersed in a two-component treatment liquid composed of 650 g of ethanol, 350 g of deionized water, 20 g of silane coupling agent A187, and 10.5 g of PETMP, with nitric acid to adjust the pH to 3.5, for 20 min; then it was placed in a sol composed of 10 g of tetrabutyl titanate, 20 g of ethanol, 0.5 g of deionized water, and 0.3 g of acetylacetone, and was treated by ultrasonic oscillation at 80℃ for 30 min to obtain modified aramid fiber;

[0029] 50 g of nitrile rubber and 7.5 g of nano-aluminum hydroxide were placed in the side feed port of the double screw extruder, and 100 g of cashew oil modified phenolic resin was placed in the main feed port of the double screw extruder, the temperature was controlled at 95℃, the screw rotation speed was 200 rpm, and 157.1 g of modified phenolic resin was obtained by extrusion;

[0030] Put 25 g of modified aramid fiber, 15 g of steel fiber, 10 g of barium sulfate, 5 g of flake graphite, and 2.5 g of surface-aminated nanodiamond into a paddle mixer, control the temperature at 45°C and the speed at 900 rpm, mix for 4 min; then add 30 g of modified phenolic resin, control the temperature at 60°C and the speed at 1400 rpm, mix for 2.5 min; then adjust the temperature to 70°C and the speed to 2000 rpm, mix for 5 min to obtain a composite matrix;

[0031] Mold the composite matrix at 120°C and 10 MPa for 5 min, then at 170°C and 30 MPa for 15 min; after taking out, put it into a box-type atmosphere furnace, heat at 200°C for 2 h under nitrogen atmosphere, then increase to 230°C at a rate of 2°C / min, continue to heat for 1 h, and take out to obtain an aramid-phenolic resin composite material. Example 2

[0032] Put the aramid fiber into an argon plasma device, adjust the power to 200 W, the cavity pressure to 30 Pa, and the gas flow to 50 sccm, and treat for 3 min; then soak in a two-component treatment liquid composed of 600 g of ethanol, 400 g of deionized water, 30 g of silane coupling agent A187, and 5 g of PETMP, with nitric acid adjusted to pH = 3, for 20 min; then put it into a sol composed of 10 g of tetrabutyl titanate, 15 g of ethanol, 0.3 g of deionized water, and 0.2 g of acetylacetone, and treat it with ultrasonic oscillation at 70°C for 35 min to obtain modified aramid fiber.

[0033] Put 50 g of nitrile rubber and 7.5 g of nano-aluminum hydroxide into the side feed port of a twin-screw extruder, and 100 g of cashew oil modified phenolic resin into the main feed port of the twin-screw extruder, control the temperature at 105°C and the screw speed at 150 rpm, and extrude to obtain 156.9 g of modified phenolic resin.

[0034] Put 25 g of modified aramid fiber, 15 g of steel fiber, 10 g of barium sulfate, 5 g of flake graphite, and 2.5 g of surface-aminated nanodiamond into a paddle mixer, control the temperature at 40°C and the speed at 800 rpm, mix for 5 min; then add 30 g of modified phenolic resin, control the temperature at 55°C and the speed at 1200 rpm, mix for 3 min; then adjust the temperature to 65°C and the speed to 1800 rpm, mix for 6 min to obtain a composite matrix.

[0035] Mold the composite matrix at 110°C and 12 MPa for 5 min, then at 160°C and 35 MPa for 15 min; after taking out, put it into a box-type atmosphere furnace, heat at 190°C for 2.5 h under nitrogen atmosphere, then increase to 220°C at a rate of 2°C / min, continue to heat for 1.25 h, and take out to obtain an aramid-phenolic resin composite material. Example 3

[0036] Aramid fibers were placed in an argon plasma device with a power of 500W, a chamber pressure of 50Pa, and a gas flow rate of 80sccm for 1 min. Then, they were immersed in a two-component treatment solution consisting of 720g ethanol, 300g deionized water, 12g silane coupling agent A187, and 6g PETMP, with the pH adjusted to 4 by nitric acid, for 20 min. Finally, they were immersed in a sol consisting of 10g tetrabutyl titanate, 25g ethanol, 0.7g deionized water, and 0.4g acetylacetone, and ultrasonically vibrated at 90℃ for 25 min to obtain modified aramid fibers.

[0037] 50g of nitrile rubber and 7.5g of nano aluminum hydroxide were placed in the side feed inlet of a twin-screw extruder, and 100g of cashew oil modified phenolic resin was placed in the main feed inlet of a twin-screw extruder. The temperature was controlled at 85℃ and the screw speed was 250rpm. 157g of modified phenolic resin was obtained by extrusion.

[0038] 25g of modified aramid fiber, 15g of steel fiber, 10g of barium sulfate, 5g of flake graphite, and 2.5g of surface-aminated nanodiamond were placed into a paddle mixer. The temperature was controlled at 50℃ and the speed at 1000rpm, and the mixture was mixed for 3 minutes. Then, 30g of modified phenolic resin was added, and the temperature was controlled at 65℃ and the speed at 1500rpm, and the mixture was mixed for 2 minutes. Finally, the temperature was adjusted to 75℃ and the speed at 2200rpm, and the mixture was mixed for 4 minutes to obtain the composite matrix.

[0039] The composite matrix was molded at 130℃ and 8MPa for 5 minutes, and then at 180℃ and 25MPa for 15 minutes. After removal, it was placed in a box-type atmosphere furnace and heated at 210℃ for 1.5 hours under a nitrogen atmosphere. Then, the temperature was increased to 240℃ at a rate of 2℃ / min and heated for another 0.75 hours. The resulting aramid phenolic resin composite material was then obtained. Example 4

[0040] Aramid fibers were placed in an argon plasma device with a power of 300W, a chamber pressure of 40Pa, and a gas flow rate of 65sccm for 2 minutes. Then, they were immersed in a two-component treatment solution consisting of 650g ethanol, 350g deionized water, 20g silane coupling agent KH-560, and 10.5g PETMP, with the pH adjusted to 3.5 by nitric acid, for 20 minutes. Finally, they were immersed in a sol consisting of 10g tetrabutyl titanate, 20g ethanol, 0.5g deionized water, and 0.3g acetylacetone, and ultrasonically vibrated at 80℃ for 30 minutes to obtain modified aramid fibers.

[0041] 25g of nitrile rubber and 5g of nano aluminum hydroxide were placed in the side feed inlet of a twin-screw extruder, and 100g of cashew oil-modified phenolic resin was placed in the main feed inlet of a twin-screw extruder. The temperature was controlled at 95℃ and the screw speed was 200rpm. 128.7g of modified phenolic resin was obtained by extrusion.

[0042] 15g of modified aramid fiber, 10g of steel fiber, 5g of barium sulfate, 3g of flake graphite, and 2g of surface-aminated nanodiamond were placed into a paddle mixer. The temperature was controlled at 45℃ and the speed at 900 rpm, and the mixture was mixed for 4 minutes. Then, 20g of modified phenolic resin was added, and the temperature was controlled at 60℃ and the speed at 1400 rpm, and the mixture was mixed for 2.5 minutes. Finally, the temperature was adjusted to 70℃ and the speed at 2000 rpm, and the mixture was mixed for 5 minutes to obtain the composite matrix.

[0043] The composite matrix was molded at 120℃ and 10MPa for 4 minutes, and then at 170℃ and 30MPa for 20 minutes. After removal, it was placed in a box-type atmosphere furnace and heated at 200℃ for 2 hours under a nitrogen atmosphere. Then, the temperature was increased to 230℃ at a rate of 2℃ / min and heated for another hour. The resulting aramid phenolic resin composite material was obtained. Example 5

[0044] Aramid fibers were placed in an argon plasma device with a power of 300W, a chamber pressure of 40Pa, and a gas flow rate of 65sccm for 2 minutes. Then, they were immersed in a two-component treatment solution consisting of 650g ethanol, 350g deionized water, 20g silane coupling agent A187, and 10g TMPMP, with the pH adjusted to 3.5 by nitric acid, for 20 minutes. Finally, they were immersed in a sol consisting of 10g tetrabutyl titanate, 20g ethanol, 0.5g deionized water, and 0.3g acetylacetone, and ultrasonically vibrated at 80℃ for 30 minutes to obtain modified aramid fibers.

[0045] 66.7g of nitrile rubber and 10g of nano aluminum hydroxide were placed in the side feed inlet of a twin-screw extruder, and 100g of cashew oil modified phenolic resin was placed in the main feed inlet of a twin-screw extruder. The temperature was controlled at 95℃ and the screw speed was 200rpm. 175.9g of modified phenolic resin was obtained by extrusion.

[0046] 30g of modified aramid fiber, 20g of steel fiber, 15g of barium sulfate, 7.5g of flake graphite, and 3g of surface-aminated nanodiamond were placed into a paddle mixer. The temperature was controlled at 45℃ and the speed at 900 rpm, and the mixture was mixed for 4 minutes. Then, 35g of modified phenolic resin was added, and the temperature was controlled at 60℃ and the speed at 1400 rpm, and the mixture was mixed for 2.5 minutes. Finally, the temperature was adjusted to 70℃ and the speed to 2000 rpm, and the mixture was mixed for 5 minutes to obtain the composite matrix.

[0047] The composite matrix was molded at 120℃ and 10MPa for 6 minutes, and then at 170℃ and 30MPa for 10 minutes. After removal, it was placed in a box-type atmosphere furnace and heated at 200℃ for 2 hours under nitrogen atmosphere. Then, the temperature was increased to 230℃ at 2℃ / min and heated for another hour. The resulting aramid phenolic resin composite material was obtained. Comparative Example 1

[0048] The difference from Example 1 is that the aramid fibers in this comparative example were not subjected to plasma treatment.

[0049] Aramid fibers were immersed in a two-component treatment solution consisting of 650g ethanol, 350g deionized water, 20g silane coupling agent A187, and 10g PETMP, with the pH adjusted to 3.5 by nitric acid, for 20 minutes. Then, they were immersed in a sol consisting of 10g tetrabutyl titanate, 20g ethanol, 0.5g deionized water, and 0.3g acetylacetone, and ultrasonically vibrated at 80°C for 30 minutes to obtain modified aramid fibers.

[0050] 50g of nitrile rubber and 7.5g of nano aluminum hydroxide were placed in the side feed inlet of a twin-screw extruder, and 100g of cashew oil modified phenolic resin was placed in the main feed inlet of a twin-screw extruder. The temperature was controlled at 95℃ and the screw speed was 200rpm. 157g of modified phenolic resin was obtained by extrusion.

[0051] 25g of modified aramid fiber, 15g of steel fiber, 10g of barium sulfate, 5g of flake graphite, and 2.5g of surface-aminated nanodiamond were placed into a paddle mixer. The temperature was controlled at 45℃ and the speed at 900 rpm, and the mixture was mixed for 4 minutes. Then, 30g of modified phenolic resin was added, and the temperature was controlled at 60℃ and the speed at 1400 rpm, and the mixture was mixed for 2.5 minutes. Then, the temperature was adjusted to 70℃ and the speed at 2000 rpm, and the mixture was mixed for 5 minutes to obtain the composite matrix.

[0052] The composite matrix was molded at 120℃ and 10MPa for 5 minutes, and then at 170℃ and 30MPa for 15 minutes. After removal, it was placed in a box-type atmosphere furnace and heated at 200℃ for 2 hours under nitrogen atmosphere. Then, the temperature was increased to 230℃ at 2℃ / min and heated for another hour. The resulting aramid phenolic resin composite material was obtained.

[0053] Comparative Example 2: Treatment with no two-component solution

[0054] The difference from Example 1 is that this comparative example did not treat the aramid fibers with a two-component treatment solution of silane coupling agent and polythiol.

[0055] Aramid fibers were placed in an argon plasma device with a power of 300W, a cavity pressure of 40Pa, and a gas flow rate of 65sccm for 2 minutes. Then, they were placed in a sol composed of 10g tetrabutyl titanate, 20g ethanol, 0.5g deionized water, and 0.3g acetylacetone and ultrasonically oscillated at 80℃ for 30 minutes to obtain modified aramid fibers.

[0056] 50g of nitrile rubber and 7.5g of nano aluminum hydroxide were placed in the side feed inlet of a twin-screw extruder, and 100g of cashew oil modified phenolic resin was placed in the main feed inlet of a twin-screw extruder. The temperature was controlled at 95℃ and the screw speed was 200rpm. 157g of modified phenolic resin was obtained by extrusion.

[0057] 25g of modified aramid fiber, 15g of steel fiber, 10g of barium sulfate, 5g of flake graphite, and 2.5g of surface-aminated nanodiamond were placed into a paddle mixer. The temperature was controlled at 45℃ and the speed at 900 rpm, and the mixture was mixed for 4 minutes. Then, 30g of modified phenolic resin was added, and the temperature was controlled at 60℃ and the speed at 1400 rpm, and the mixture was mixed for 2.5 minutes. Then, the temperature was adjusted to 70℃ and the speed at 2000 rpm, and the mixture was mixed for 5 minutes to obtain the composite matrix.

[0058] The composite matrix was molded at 120℃ and 10MPa for 5 minutes, and then at 170℃ and 30MPa for 15 minutes. After removal, it was placed in a box-type atmosphere furnace and heated at 200℃ for 2 hours under nitrogen atmosphere. Then, the temperature was increased to 230℃ at 2℃ / min and heated for another hour. The resulting aramid phenolic resin composite material was obtained.

[0059] Comparative Example 3: Titanium Dioxide-Free

[0060] The difference from Example 1 is that the aramid fibers in this comparative example were not subjected to sol treatment.

[0061] Aramid fibers were placed in an argon plasma device with a power of 300W, a chamber pressure of 40Pa, and a gas flow rate of 65sccm for 2 minutes. Then, they were immersed in a two-component treatment solution consisting of 650g ethanol, 350g deionized water, 20g silane coupling agent A187, and 10g PETMP, with the pH adjusted to 3.5 by nitric acid, for 20 minutes to obtain modified aramid fibers.

[0062] 50g of nitrile rubber and 7.5g of nano aluminum hydroxide were placed in the side feed inlet of a twin-screw extruder, and 100g of cashew oil modified phenolic resin was placed in the main feed inlet of a twin-screw extruder. The temperature was controlled at 95℃ and the screw speed was 200rpm. 157g of modified phenolic resin was obtained by extrusion.

[0063] 25g of modified aramid fiber, 15g of steel fiber, 10g of barium sulfate, 5g of flake graphite, and 2.5g of surface-aminated nanodiamond were placed into a paddle mixer. The temperature was controlled at 45℃ and the speed at 900 rpm, and the mixture was mixed for 4 minutes. Then, 30g of modified phenolic resin was added, and the temperature was controlled at 60℃ and the speed at 1400 rpm, and the mixture was mixed for 2.5 minutes. Then, the temperature was adjusted to 70℃ and the speed at 2000 rpm, and the mixture was mixed for 5 minutes to obtain the composite matrix.

[0064] The composite matrix was molded at 120℃ and 10MPa for 5 minutes, and then at 170℃ and 30MPa for 15 minutes. After removal, it was placed in a box-type atmosphere furnace and heated at 200℃ for 2 hours under nitrogen atmosphere. Then, the temperature was increased to 230℃ at 2℃ / min and heated for another hour. The resulting aramid phenolic resin composite material was obtained.

[0065] Comparative Example 4: Phenolic Resin-Free Treatment

[0066] The difference from Example 1 is that the phenolic resin in this comparative example was not modified.

[0067] Aramid fibers were placed in an argon plasma device with a power of 300W, a chamber pressure of 40Pa, and a gas flow rate of 65sccm for 2 minutes. Then, they were immersed in a two-component treatment solution consisting of 650g ethanol, 350g deionized water, 20g silane coupling agent A187, and 10g PETMP, with the pH adjusted to 3.5 by nitric acid, for 20 minutes. Finally, they were immersed in a sol consisting of 10g tetrabutyl titanate, 20g ethanol, 0.5g deionized water, and 0.3g acetylacetone, and ultrasonically vibrated at 80℃ for 30 minutes to obtain modified aramid fibers.

[0068] 25g of modified aramid fiber, 15g of steel fiber, 10g of barium sulfate, 5g of flake graphite, and 2.5g of surface-aminated nanodiamond were placed into a paddle mixer. The temperature was controlled at 45℃ and the speed at 900 rpm, and the mixture was mixed for 4 minutes. Then, 30g of cashew oil-modified phenolic resin was added, and the temperature was controlled at 60℃ and the speed at 1400 rpm, and the mixture was mixed for 2.5 minutes. Then, the temperature was adjusted to 70℃ and the speed at 2000 rpm, and the mixture was mixed for 5 minutes to obtain the composite matrix.

[0069] The composite matrix was molded at 120℃ and 10MPa for 5 minutes, and then at 170℃ and 30MPa for 15 minutes. After removal, it was placed in a box-type atmosphere furnace and heated at 200℃ for 2 hours under nitrogen atmosphere. Then, the temperature was increased to 230℃ at 2℃ / min and heated for another hour. The resulting aramid phenolic resin composite material was obtained.

[0070] Comparative Example 5: Friction-Free Modifier

[0071] The difference from Example 1 is that no flake graphite and surface-aminated nanodiamonds were added to the composite material prepared in this comparative example.

[0072] Aramid fibers were placed in an argon plasma device with a power of 300W, a chamber pressure of 40Pa, and a gas flow rate of 65sccm for 2 minutes. Then, they were immersed in a two-component treatment solution consisting of 650g ethanol, 350g deionized water, 20g silane coupling agent A187, and 10g PETMP, with the pH adjusted to 3.5 by nitric acid, for 20 minutes. Finally, they were immersed in a sol consisting of 10g tetrabutyl titanate, 20g ethanol, 0.5g deionized water, and 0.3g acetylacetone, and ultrasonically vibrated at 80℃ for 30 minutes to obtain modified aramid fibers.

[0073] 50g of nitrile rubber and 7.5g of nano aluminum hydroxide were placed in the side feed inlet of a twin-screw extruder, and 100g of cashew oil modified phenolic resin was placed in the main feed inlet of a twin-screw extruder. The temperature was controlled at 95℃ and the screw speed was 200rpm. 157g of modified phenolic resin was obtained by extrusion.

[0074] 25g of modified aramid fiber, 15g of steel fiber, and 10g of barium sulfate were placed into a paddle mixer and mixed for 4 minutes at a temperature of 45℃ and a speed of 900 rpm. Then, 30g of modified phenolic resin was added and mixed for 2.5 minutes at a temperature of 60℃ and a speed of 1400 rpm. The temperature was then adjusted to 70℃ and the speed to 2000 rpm, and the mixture was mixed for 5 minutes to obtain the composite matrix.

[0075] The composite matrix was molded at 120℃ and 10MPa for 5 minutes, and then at 170℃ and 30MPa for 15 minutes. After removal, it was placed in a box-type atmosphere furnace and heated at 200℃ for 2 hours under nitrogen atmosphere. Then, the temperature was increased to 230℃ at 2℃ / min and heated for another hour. The resulting aramid phenolic resin composite material was obtained.

[0076] Comparative Example 6: No Heating Stabilization Treatment

[0077] The difference from Example 1 is that this comparative example did not subject the molded and cured composite material to heat treatment.

[0078] Aramid fibers were placed in an argon plasma device with a power of 300W, a chamber pressure of 40Pa, and a gas flow rate of 65sccm for 2 minutes. Then, they were immersed in a two-component treatment solution consisting of 650g ethanol, 350g deionized water, 20g silane coupling agent A187, and 10g PETMP, with the pH adjusted to 3.5 by nitric acid, for 20 minutes. Finally, they were immersed in a sol consisting of 10g tetrabutyl titanate, 20g ethanol, 0.5g deionized water, and 0.3g acetylacetone, and ultrasonically vibrated at 80℃ for 30 minutes to obtain modified aramid fibers.

[0079] 50g of nitrile rubber and 7.5g of nano aluminum hydroxide were placed in the side feed inlet of a twin-screw extruder, and 100g of cashew oil modified phenolic resin was placed in the main feed inlet of a twin-screw extruder. The temperature was controlled at 95℃ and the screw speed was 200rpm. 157g of modified phenolic resin was obtained by extrusion.

[0080] 25g of modified aramid fiber, 15g of steel fiber, 10g of barium sulfate, 5g of flake graphite, and 2.5g of surface-aminated nanodiamond were placed into a paddle mixer. The temperature was controlled at 45℃ and the speed at 900 rpm, and the mixture was mixed for 4 minutes. Then, 30g of modified phenolic resin was added, and the temperature was controlled at 60℃ and the speed at 1400 rpm, and the mixture was mixed for 2.5 minutes. Then, the temperature was adjusted to 70℃ and the speed at 2000 rpm, and the mixture was mixed for 5 minutes to obtain the composite matrix.

[0081] The composite matrix was molded at 120℃ and 10MPa for 5 minutes, and then at 170℃ and 30MPa for 15 minutes to obtain the aramid phenolic resin composite material.

[0082] Experimental Example 1

[0083] The shear strength was tested at 25°C according to ASTM D2344, "Standard Test Method for Shear Strength of Polymer-Based Composite Materials and Laminates for Short Beams".

[0084] Experimental Example 2

[0085] According to the GB5763-2018 standard "Automotive Brake Liners", the coefficient of friction was tested at 100℃ and 350℃, and the wear rate was tested at 25℃.

[0086] Table 1 is a performance comparison table of Examples 1-5 and each comparative example.

[0087]

[0088] As shown in Table 1, the friction materials prepared in Examples 1-5 exhibit significantly improved shear strength, thermal degradation performance, and wear resistance compared to Comparative Examples 1-6. The following discussion uses Example 1 as an example, combined with...Figure 1 Comparative analysis:

[0089] Compared to Comparative Example 1, which did not undergo plasma modification, Example 1 showed a 56.6% increase in shear strength, a 63.9% increase in heat fading resistance, and a 53.3% increase in abrasion resistance. This is because the present invention modifies aramid fibers using argon plasma, silane coupling agent and polythiol impregnation, and sol-gel loading of titanium dioxide. Argon plasma treatment generates -COOH / -NH2 active groups on the aramid surface and forms micro-etched grooves, increasing the specific surface area of ​​the aramid fiber surface and improving the coverage of silane coupling agent and polythiol.

[0090] from Figure 1 As can be seen from the data: In Example 1, the peak with diffraction angle values ​​of 25~25.5 on the horizontal axis represents anatase TiO2; the peaks at 27.1~27.6, 35.9~36.4, 41~41.5, and 54~54.5 represent rutile TiO2, indicating that at 230℃, a small portion of the TiO2 coating transforms from an amorphous phase to the rutile phase during heat treatment; the peak at 28.6~29.1 represents BaSO4; and the peak at 44~44.5 represents α-Fe introduced by steel fibers. The peak positions all coincide with the peak positions of the standard material cards for anatase TiO2, rutile TiO2, BaSO4, and α-Fe.

[0091] Compared to Comparative Example 2, which did not immerse the aramid fibers in the two-component treatment solution, the shear strength can be increased by 39.7%, the heat fading resistance can be increased by 59.9%, and the wear resistance can be increased by 52.3%. This is because the epoxy groups of the silane coupling agent and the thiol groups of the polythiol can form dual reaction sites, which increases the surface energy of the aramid fibers, thereby allowing the aramid fibers to be covered with more TiO2 coating prepared by the sol-gel method.

[0092] Compared with Comparative Example 3, which did not perform sol-gel oscillation treatment on aramid fibers, its shear strength can be increased by 25.5%, its heat fading resistance can be increased by 56.8%, and its wear resistance can be increased by 44.7%. This is because the TiO2 coating prepared by the sol-gel method is transformed into rutile phase through heating treatment in step (5), forming Ti-OC chemical bonds with the resin, which increases the interfacial bonding force between aramid fibers and phenolic resin. Furthermore, the rutile phase TiO2 can block air from contacting phenolic resin, inhibit the oxidative cracking of phenolic resin, and reduce the heat fading rate of composite materials while improving the mechanical strength of composite materials.

[0093] Compared to Comparative Example 4 without modification of the phenolic resin, its shear strength can be increased by 72.7%, its heat fading resistance by 66.3%, and its wear resistance by 62.5%. This is because the present invention mixes and extrudes cashew oil-modified phenolic resin, nitrile rubber, and nano-aluminum hydroxide to obtain modified phenolic resin. The cashew oil-modified phenolic resin acts as a rigid skeleton, and the nitrile rubber forms a "sea-island" structure with it in the twin-screw shear field. The nitrile rubber, as a flexible region, can absorb the energy of crazing, reduce the crack propagation rate, and increase the mechanical strength of the composite material. At the same time, the nano-aluminum hydroxide fills the phase interface, playing a role in crack deflection and bridging the phenolic resin and nitrile rubber. The long fatty chain structure of cashew oil can interpenetrate the aromatic ring network of the phenolic resin, promote molecular chain slip, improve the shear strength of the modified phenolic resin matrix, and thus increase the mechanical strength of the composite material. The energy of external force acting on the composite material is absorbed through the dual mechanisms of rubber phase deformation dissipation and nanoparticle crack deflection, which can improve the mechanical strength and wear resistance of the composite material.

[0094] Compared to Comparative Example 5, which uses no friction modifier (flake graphite and surface-aminated nanodiamonds), the shear strength can be increased by 18.3%, the heat fading resistance can be increased by 60.9%, and the wear resistance can be increased by 34.4%. This is because the present invention uses flake graphite and surface-aminated nanodiamonds as friction modifiers. When the temperature is >250℃, the surface amino groups of the aminated nanodiamonds react with the hydroxymethyl groups of the resin to form a CNC network, which acts as a protective film and improves the friction coefficient of the composite material. At the same time, the friction process between flake graphite and nanodiamonds generates a diamond-like carbon film, which, combined with the surface-silanized steel fibers, constructs a three-dimensional heat conduction pathway, allowing the frictional heat to diffuse rapidly and improving the heat fading resistance of the composite material.

[0095] Compared to Comparative Example 6, which did not undergo subsequent heat treatment, its shear strength can be increased by 10.0%, its heat fading resistance by 51.3%, and its wear resistance by 32.2%. This is because the present invention triggers a deep reaction and promotes interfacial bonding through stepped heat treatment; at 190~210℃, the resin β relaxes, the molecular chain rearranges, and the residual stress of molding is released; at 220~240℃, the aramid macromolecular chain segments slip and fill the microcracks; at the same time, the phenolic resin is cured twice at high temperature and the aramid and phenolic resin undergo an interfacial reaction; and the TiO2 coating is heated... The process involves the transformation of the amorphous phase into the rutile phase, forming Ti-OC chemical bonds with the resin, thereby improving the mechanical strength of the composite material. A single-temperature heat treatment cannot simultaneously achieve all of the above objectives. If only low temperature is used, the interfacial reaction and TiO2 phase transformation cannot be completed, resulting in insufficient high-temperature performance of the material. If high temperature is used directly, the residual stress inside the material and unreacted small molecules will cause blistering, deformation, or even cracking of the product due to rapid reaction. Stepwise heating follows the kinetic law of material reaction, gradually stimulating the performance of the material, and is an essential process to ensure the high stability of the composite material.

[0096] The specific embodiments described above provide a further detailed explanation of the present invention; however, these descriptions should not be construed as limiting the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing an aramid phenolic resin composite material, characterized in that, Includes the following steps: (1) Aramid fibers are subjected to plasma treatment and then immersed in an aqueous ethanol solution containing silane coupling agent and polythiol to obtain modified aramid fibers. (2) Tetrabutyl titanate, ethanol, water and acetylacetone are mixed to obtain a gel. Modified aramid fibers are placed in the gel and ultrasonically oscillated to obtain modified aramid fibers with titanium dioxide loaded on the surface. (3) Cashew oil modified phenolic resin, nitrile rubber, and nano aluminum hydroxide are mixed and extruded into granules to obtain modified phenolic resin; (4) Modified aramid fiber, steel fiber, barium sulfate, flake graphite and surface-aminated nanodiamond are blended in one stage; then modified phenolic resin is added and the temperature and speed are increased for a second stage of blending; then the temperature and speed are increased again for a third stage of blending to obtain a composite matrix. (5) The composite matrix is ​​molded, cured, and heated to obtain an aramid phenolic resin composite material; the heating treatment is a stepped heat treatment, which is to first heat at 190~210℃ for 1.5~2.5h, and then heat at 220~240℃ for 0.75~1.25h. In step (1), the silane coupling agent is silane coupling agent KH-560, and the polythiol is one of pentaerythritol tetra(3-mercaptopropionate) or trimethylolpropane tri(3-mercaptopropionate). In step (3), the mass ratio of cashew oil-modified phenolic resin, nitrile rubber, and nano aluminum hydroxide is 1:0.25~0.667:0.05~0.1; In step (4), the mass ratio of modified aramid fiber, modified phenolic resin, steel fiber, barium sulfate, flake graphite, and surface-aminated nanodiamond is 0.75~0.857:1:0.5~0.57:0.25~0.428:0.15~0.214:0.083~0.1; the first-stage blending temperature is 40~50℃, the rotation speed is 800~1000rpm, and the time is 3~5min; the second-stage blending temperature is 55~65℃, the rotation speed is 1200~1500rpm, and the time is 2~3min; the third-stage blending temperature is 65~75℃, the rotation speed is 1800~2200rpm, and the time is 4~6min.

2. The method for preparing the aramid phenolic resin composite material according to claim 1, characterized in that, In step (1), the plasma atmosphere is argon, the gas flow rate is 50~80 sccm, the cavity pressure is 30~50 Pa, the power is 200~500 W, and the processing time is 1~3 min.

3. The method for preparing the aramid phenolic resin composite material according to claim 1, characterized in that, In step (1), the pH of the ethanol aqueous solution is 3-4; the mass ratio of ethanol, water, silane coupling agent and polythiol in the ethanol aqueous solution containing silane coupling agent and polythiol is 150-240:100:4-7.5:1.25-3; and the immersion time in the ethanol aqueous solution containing silane coupling agent and polythiol is 10-30 min.

4. The method for preparing the aramid phenolic resin composite material according to claim 1, characterized in that, In step (2), the mass ratio of tetrabutyl titanate, ethanol, water and acetylacetone is 10:15~25:0.3~0.7:0.2~0.4; the oscillation treatment temperature is 70~90℃ and the oscillation treatment time is 25~35min.

5. The method for preparing the aramid phenolic resin composite material according to claim 1, characterized in that, In step (5), the molding curing conditions are: molding at 110~130℃ and 8~12MPa for 4~6min, and then molding at 160~180℃ and 25~35MPa for 10~20min.

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