Phenolic resin-based friction material as well as preparation method and application thereof

Abstract

The invention relates to the field of phenolic resin-based friction materials, in particular to a phenolic resin-based friction material and a preparation method and application thereof. Comprising the following components: 20-30 wt% of phenolic resin, 8-18 wt% of a halogen-free composite flame-retardant system, 8-12 wt% of a cardanol derivative curing agent and reinforced fibers, 15-20 wt% of a metal filler, and 25-35 wt% of an auxiliary filler. Through a specific compounding ratio of a halogen-free composite flame-retardant system, a cardanol derivative curing agent and a vacuum gradient hot pressing process of magnesium oxide whiskers to expandable graphite of 1: (1.5-2.5), the oxygen index is greater than or equal to 34% under the condition of low addition amount of 8-18wt%, and the oxygen index is increased by 13% compared with that of a traditional single halogen-free flame-retardant material; the bio-based cardanol derivative curing agent is adopted to replace hexamethylenetetramine, so that the VOC emission is reduced to 3.2 g / L from 10g / L in the traditional process.

Description

A phenolic resin-based friction material, its preparation method and application Technical Field

[0001] This invention relates to the field of phenolic resin-based friction materials, specifically to a phenolic resin-based friction material, its preparation method, and its application. Background Technology

[0002] Specialty phenolic resin materials, such as phenolic resin-based friction materials, are widely used in rail transportation, automotive braking systems, and other fields due to their excellent mechanical properties, friction stability, and temperature resistance. With increasingly stringent global environmental regulations, especially the EU REACH regulation and third-party certification requirements such as the Railway Environmental Directive 2024 / 897 / EU, clear and strict mandatory indicators have been set for friction materials, including halogen-free production, low VOC emissions, heavy metal restrictions, and energy consumption control.

[0003] Existing nano-modification methods suffer from problems such as uneven particle size, poor dispersibility, and weak bonding with the matrix. For example, patent CN202411250480.7 uses a nano-silica composite system modified with amino and double bonds. Although it can reduce the free phenol content by participating in the cross-linking reaction, the nanoparticles are prone to agglomeration, resulting in unstable friction interface repair effects and a wear rate reduction of only 15%.

[0004] Meanwhile, existing phenolic resin-based friction materials also have the following key drawbacks:

[0005] Traditional halogenated flame retardants (such as decabromodiphenyl ether) have high flame retardant efficiency, but they decompose at high temperatures to produce toxic gases such as hydrogen bromide. Single halogen-free flame retardants (such as magnesium hydroxide or expandable graphite) need to be added in amounts exceeding 20 wt% to meet the UL94 V-0 flame retardant standard, which leads to a decrease in material impact strength of more than 30%, making it impossible to meet the mechanical performance requirements of braking systems.

[0006] Commonly used hexamethylenetetramine curing agents decompose to produce formaldehyde at temperatures above 160°C, resulting in VOC emissions exceeding 10 g / L. Furthermore, its interfacial reaction with halogen-free flame retardants can cause friction coefficient fluctuations to exceed ±0.1, affecting braking stability.

[0007] Using constant temperature and high pressure processes (such as 170℃ / 10MPa / 120min), the unit energy consumption is as high as 800kJ / kg, and it is easy to cause internal stress concentration in the material, with a curing degree of only 85%-89%, which further aggravates the fluctuation of friction performance. Summary of the Invention

[0008] To address the problems in the prior art, this invention provides a phenolic resin-based friction material, its preparation method, and its application.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A phenolic resin-based friction material comprises the following components: 20-30 wt% phenolic resin, 8-18 wt% halogen-free composite flame retardant system, cashew nut phenol derivative curing agent, 8-12 wt% reinforcing fiber, 15-20 wt% metal filler, and 25-35 wt% auxiliary filler; wherein, the phenolic resin, as a binder, has good heat resistance, high thermal decomposition temperature, low thermal weight loss, and suitable curing speed, to ensure the stable performance of the material under high-temperature conditions.

[0011] The halogen-free composite flame retardant system is composed of magnesium hydroxide whiskers and expandable graphite in a mass ratio of 1:1.5-2.5, wherein the amount of magnesium hydroxide whiskers added is 3-8 wt% and the amount of expandable graphite added is 5-10 wt%.

[0012] The cashew phenol derivative curing agent is 3-pentadecanylphenol, and the addition amount is 4-6 wt% of the phenolic resin. The cashew phenol derivative curing agent is purchased from Zhejiang Wansheng Co., Ltd., with a purity of ≥98% and a renewability of ≥90%.

[0013] The reinforcing fiber is bamboo fiber;

[0014] The metal filler is copper powder;

[0015] The auxiliary filler includes one or more of talc powder, mica powder, and barium sulfate;

[0016] The friction material meets the following compliance indicators: total chlorine (Cl) + bromine (Br) content ≤ 900 ppm, total VOC content ≤ 5 g / L (test standard: GB / T 23984-2009), lead (Pb) and cadmium (Cd) content < 10 ppm, mercury (Hg) and hexavalent chromium (… Content < 5 ppm.

[0017] The magnesium hydroxide whiskers have a diameter of 50-100 nm and an aspect ratio of 20-30; the expandable graphite has an expansion ratio of 200-300 times.

[0018] The auxiliary filler is a compound system composed of talc powder, mica powder and barium sulfate, with a compounding ratio of 12:10:11.8.

[0019] A preparation process for a phenolic resin-based friction material includes the following steps:

[0020] Step 1, Raw material mixing: Phenolic resin, halogen-free composite flame retardant system, cashew phenol derivative curing agent, reinforcing fiber, metal filler and auxiliary filler are put into a high-speed mixer, the speed is set to 500 r / min, and the mixture is stirred for 20 min to obtain the mixture.

[0021] Step 2, Low-temperature pre-curing: Place the mixture in a mold and pre-cur it for 30-60 minutes at a temperature of 100-120℃ and a pressure of 1-2MPa.

[0022] Step 3, Vacuum Gradient Hot Pressing: Place the pre-cured material in a vacuum hot press, controlling the vacuum degree to ≤0.01MPa (control accuracy ±0.001MPa), and perform gradient hot pressing at a heating rate of 5-8℃ / min (control accuracy ±0.5℃ / min), sequentially passing through three stages: 140℃, pressure 4-6MPa, holding pressure for 20min; 145℃, pressure 6-8MPa, holding pressure for 30min; 150℃, pressure 8-10MPa, holding pressure for 20min.

[0023] Step 4, Post-curing: Place the hot-pressed blank in an environment of 160℃ for 8 hours, and demold it after it cools naturally to room temperature to obtain phenolic resin-based friction material.

[0024] The low-temperature pre-curing conditions are: temperature 110℃, pressure 1.5MPa, and time 45min.

[0025] During the vacuum gradient hot pressing process, the vacuum level is set to 0.008 MPa, the heating rate is 6℃ / min, and the pressures at each stage are 5 MPa, 7 MPa, and 9 MPa, respectively.

[0026] Compared with existing technologies, the beneficial effects of the invention are: by using a specific compounding ratio of magnesium oxide whiskers and expandable graphite of 1:1.5-2.5 in the "halogen-free composite flame retardant system - cashew nut shell extract curing agent - vacuum gradient hot pressing process", an oxygen index of ≥34% is achieved at a low addition amount of 8-18wt%, which is 13% higher than that of traditional single halogen-free flame retardant materials;

[0027] By replacing hexamethylenetetramine with a bio-based cashew phenol derivative curing agent (3-pentadecanophenol), VOC emissions are reduced from 10 g / L in the traditional process to 3.2 g / L. At the same time, the impact strength is improved to 4.2 kJ / m² through the long-chain alkyl structure, and there is no interfacial repulsion with the halogen-free flame retardant system.

[0028] The three-stage vacuum gradient hot pressing process is matched with the resin curing kinetics, reducing unit energy consumption from 800kJ / kg to 624kJ / kg, a reduction of 22%. In addition, by eliminating internal stress through gradient pressure increase, the fluctuation of the friction coefficient is controlled within ±0.02, improving stability by 75% compared with the traditional process. Attached Figure Description

[0030] Figure 1 shows the SEM characterization of the halogen-free composite flame retardant system of the present invention;

[0031] Figure 2 shows a comparison of the DSC curing curves of the material of the present invention and conventional materials;

[0032] Figure 3 shows a comparison of the thermogravimetric analysis curves of the material of the present invention and the conventional material;

[0033] Figure 4 shows the curve of the friction coefficient of the material of the present invention as a function of temperature;

[0034] Figure 5 illustrates a comparison of the wear rates of the material of the present invention and traditional materials. Detailed Implementation

[0035] The present invention will now be described in further detail with the aid of embodiments. It should be noted that the embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0036] A halogen-free, low-harm, energy-saving, and compliant phenolic resin-based friction material, based on 100% of the total mass of the friction material, comprises the following components: 20-30 wt% phenolic resin, 8-18 wt% halogen-free composite flame retardant system, cashew nut phenol derivative curing agent, 8-12 wt% reinforcing fiber, 15-20 wt% metal filler, and 25-35 wt% auxiliary filler;

[0037] The halogen-free composite flame retardant system is composed of magnesium hydroxide whiskers (50-100 nm in diameter, aspect ratio 20-30) and expandable graphite (expansion ratio 200-300 times) in a mass ratio of 1:1.5-2.5, wherein the amount of magnesium hydroxide whiskers added is 3-8 wt% and the amount of expandable graphite added is 5-10 wt%.

[0038] The amount of the cashew phenol derivative curing agent (3-pentadecanophenol) added is 4-6 wt% of the phenolic resin mass;

[0039] The friction material must meet the following compliance standards: the total content of chlorine (Cl) and bromine (Br) shall not exceed 900 ppm, the total VOC content shall not exceed 5 g / L, the content of lead (Pb) and cadmium (Cd) shall be less than 10 ppm, and the content of mercury (Hg) and hexavalent chromium (Cd) shall be less than 900 ppm. The content is less than 5 ppm.

[0040] The reinforcing fiber is bamboo fiber.

[0041] The metal filler is copper powder.

[0042] The auxiliary filler includes one or more of talc powder, mica powder, and barium sulfate.

[0043] Synergistic Flame Retardant and Performance Balance Effects of Halogen-Free Composite Flame Retardant System: Magnesium hydroxide whiskers, as an inorganic flame retardant, achieve physical flame retardancy through the endothermic decomposition of crystal water (decomposition temperature range 340-400℃). Their needle-like structure, with a diameter between 50-100 nm and an aspect ratio of 20-30, can form a "rigid support network" with the resin, thereby enhancing interfacial bonding. Expandable graphite (expansion ratio 200-300 times) forms a worm-like char layer at high temperatures, achieving synergistic chemical flame retardancy and thermal insulation. Experimental data show that when the mass ratio of magnesium hydroxide whiskers to expandable graphite is 1:1.5, the oxygen index reaches 32%, and the impact strength is 3.8 kJ / m²; when the mass ratio is 1:2, the oxygen index is 34%, and the impact strength increases to 4.2 kJ / m²; when the mass ratio is 1:2.5, the oxygen index is 33%, and the impact strength is 3.9 kJ / m². When deviating from this range (e.g., a mass ratio of 1:1 or 1:3), the oxygen index will fall below 30%, or the impact strength will decrease by more than 15%. This specific ratio achieves an optimal balance between flame retardancy and mechanical properties through a triple synergy of "physical heat absorption – charcoal layer barrier – structural reinforcement," which cannot be obtained through simple mixing. Performance comparison data for different ratios are shown in the table below:

[0044]

[0045] Experimental data show that deviations from the 1:1.5-2.5 ratio result in an oxygen index of <30% or a decrease in impact strength of >15%, proving that this ratio is the optimal solution obtained through systematic testing, achieving a balance between flame retardancy and mechanical properties.

[0046] Synergistic effect of cashew phenol derivative curing agent on environmental protection and toughening: 3-Pentadecylphenol (bio-based, renewable ≥90%) replaces hexamethylenetetramine. Through the condensation reaction between the phenolic hydroxyl groups and the hydroxymethyl groups of the phenolic resin, no formaldehyde is released during the curing process (no formaldehyde peak detected in VOC testing). Its C15 long-chain alkyl group can form "molecular-level lubrication units" in the cross-linking network, increasing the elongation at break of the material by 25%, effectively solving the brittleness problem caused by traditional curing agents. The performance comparison of different curing agents and their dosages is shown in the table below:

[0047]

[0048] Comparative tests show that when 4-6 wt% cashew phenol derivatives are added, the material has the best environmental friendliness and mechanical properties, and there is no interfacial repulsion with the halogen-free flame retardant system (the curing exothermic peak in DSC test is single and there are no impurity peaks), and the wear resistance is reduced by 18% compared with traditional curing agents.

[0049] The formulation of auxiliary fillers significantly affects the wear resistance and frictional stability of materials. The performance comparison of different formulations is shown in the table below:

[0050]

[0051] Data shows that the effect of compounding multiple auxiliary fillers is better than that of single fillers. The preferred compounding scheme of this invention can further improve the frictional stability and wear resistance of the material.

[0052] The preparation process of the phenolic resin-based friction material includes the following steps:

[0053] Step 1, Raw material mixing: Place phenolic resin, halogen-free composite flame retardant system, cashew phenol derivative curing agent, reinforcing fiber, metal filler and auxiliary filler in a mixing device and stir at 500 r / min for 20 min to make it uniformly mixed to obtain a mixture.

[0054] Step 2, Low-temperature pre-curing: Place the mixture in a mold and pre-cur it for 30-60 minutes at a temperature of 100-120℃ and a pressure of 1-2MPa. Thermogravimetric analysis (TG) test conditions: nitrogen atmosphere, heating rate 10℃ / min, test range 50-800℃. The results show that the volatile matter residue of the pre-cured material below 200℃ is <2%, which is significantly lower than that of the uncured material (volatile matter residue 15%-20%). This can avoid the formation of pores due to the violent release of volatile matter during subsequent high-temperature hot pressing, and at the same time, it allows the resin to initially cross-link and form a "gel network", providing a structural basis for gradient hot pressing.

[0055] Step 3, Vacuum Gradient Hot Pressing: Place the pre-cured material in a vacuum hot press, controlling the vacuum level to ≤0.01MPa (to eliminate interference from air on the curing reaction), and perform gradient hot pressing at a heating rate of 5-8℃ / min. This gradient parameter is designed based on simulating the resin curing kinetics curve (DSC testing shows the curing reaction is completed in three stages: 140℃ is the gel point, 145℃ is the reaction peak, and 150℃ is post-curing). The material undergoes three stages sequentially: 140℃ (rapid resin cross-linking period), pressure 4-6MPa (initial densification), holding pressure for 20min; 145℃ (peak curing reaction period), pressure 6-8MPa (promoting interfacial bonding), holding pressure for 30min; 150℃ (final curing period), pressure 8-10MPa (final densification), holding pressure for 20min. This avoids the "hard outside, soft inside" phenomenon caused by traditional constant temperature and high pressure methods, improving the material density uniformity to over 98%.

[0056] Step 4, Post-curing: The hot-pressed blank is kept at 160℃ for 8 hours, and then naturally cooled to room temperature before demolding to obtain phenolic resin-based friction material.

[0057] Comparative experiments verified that the unit energy consumption of the traditional constant temperature hot pressing process (170℃ / 10MPa / 120min) is... 800 kJ / kg, the unit energy consumption of the gradient hot pressing process (140-150℃ / 4-10MPa / 70min) in this scheme is E1=624 kJ / kg, and the energy consumption reduction rate η= =22%, and due to the 42% reduction in holding time, production efficiency increased by 35%.

[0058] The conditions for low-temperature pre-curing are: temperature 110℃, pressure 1.5MPa, and time 45min; while the conditions for vacuum gradient hot pressing are: vacuum degree 0.008MPa, heating rate 6℃ / min, and pressures at each stage are 5MPa, 7MPa, and 9MPa respectively.

[0059] Compliance control indicators:

[0060] Halogen-free index: Total chlorine (Cl) + bromine (Br) content ≤900ppm;

[0061] VOC index: Total volatile organic compounds ≤ 5g / L (Test standard: GB / T 23984-2009);

[0062] Heavy metal indicators: Lead (Pb) content <10ppm, Cadmium (Cd) content <10ppm, Mercury (Hg), Hexavalent Chromium (… Content < 5 ppm;

[0063] Energy consumption indicators: Compared with the traditional 160-170℃ constant temperature hot pressing process, the energy consumption of the unit product is reduced by ≥20%. This energy-saving effect is comparable to that of UVLED curing boxes, which consume only 30% of the power of traditional equipment, highlighting the energy-saving advantages of low temperature curing technology.

[0064] Regarding the synergistic energy saving and curing optimization of low-temperature pre-curing and gradient hot pressing: Low-temperature pre-curing can remove more than 80% of the volatiles in the raw materials in advance (thermogravimetric analysis shows that the residual volatiles are <2%), thus avoiding the formation of pores due to the violent release of volatiles during gradient hot pressing. The gradient heating and pressurization design matches the resin curing kinetics (DSC testing shows that the curing reaction is divided into three stages: 140℃ is the gel point, 145℃ is the reaction peak, and 150℃ is the post-curing stage), thereby achieving uniform curing. Experimental verification: When the temperature exceeds 150℃, cashew phenol derivatives may undergo oxidation side reactions, leading to an increase in VOC emissions; when the temperature is below 140℃, the degree of curing and impact strength may be affected. The 140-150℃ range is the only feasible window that balances environmental protection, degree of curing (≥96%), and energy consumption, shortening the holding time by 42% and reducing energy consumption by 22% compared to traditional processes.

[0065] Synergistic devolatification and densification effects of vacuum environment and gradient hot pressing: Under vacuum conditions (vacuum degree ≤0.01MPa), simultaneous operation with gradient hot pressing can further remove residual volatiles from the material, enhancing the low VOC effect. Simultaneously, the internal porosity of the material can be controlled to ≤8%, improving the material's density and wear resistance, and preventing fluctuations in the coefficient of friction due to porosity.

[0066] Low-temperature pre-curing can remove more than 80% of the volatile components in the raw material in advance, avoiding the formation of pores due to the violent release of volatile components during gradient hot pressing; the gradient temperature and pressure design can match the resin curing kinetics, thereby achieving uniform curing. The performance comparison of different temperature ranges is shown in the table below:

[0067]

[0068] Experimental verification showed that when the temperature exceeded 150℃, cashew phenol derivatives underwent an oxidation side reaction, with VOC rising to 6.5g / L (exceeding the standard by 30%); when the temperature was below 140℃, the degree of curing was only 85%, and the impact strength decreased to 2.8kJ / m². The 140-150℃ range is the only feasible window that balances environmental protection, degree of curing (≥96%), and energy consumption, shortening the holding time by 42% and reducing energy consumption by 22% compared to traditional processes.

[0069] Simultaneous gradient hot pressing under vacuum conditions (vacuum degree ≤ 0.01 MPa) can further remove residual volatiles from the material, enhancing the low-VOC effect. At the same time, it controls the internal porosity of the material to ≤ 8%, improving the material's density and wear resistance, and avoiding fluctuations in the coefficient of friction caused by porosity. Performance comparisons under different vacuum conditions are as follows:

[0070]

[0071] This invention achieves synergistic innovation through a ternary coupling design of "materials-process-indicators": 1) The halogen-free composite flame-retardant system (1:1.5-2.5 ratio) determines the flame-retardant performance and mechanical basis of the material. Its whisker structure needs to match the pressure parameters (4-10MPa) of gradient hot pressing to form an effective support network; 2) The cashew nut shell extract curing agent (4-6wt% addition) not only controls VOC emissions, but its long-chain alkyl structure also needs to be fully embedded in the resin network at a peak temperature of 145℃ to achieve a toughening effect; 3) The vacuum gradient hot pressing process solves the interfacial compatibility problem between the halogen-free system and the bio-based curing agent through precise temperature control (±2℃) and pressure gradient (4→10MPa). The three form a closed-loop control of "raw material ratio-process parameters-performance indicators".

[0072] Example:

[0073] This embodiment provides a halogen-free, low-harm, energy-saving, and compliant phenolic resin-based friction material, which is prepared according to the following components and process:

[0074] Raw material ratio (total mass 100kg)

[0075] 25 kg of phenolic resin, 4 kg of magnesium hydroxide whiskers Expandable graphite 8kg ( 1.2 kg of cashew phenol derivative (4.8 wt% based on the mass of phenolic resin), 10 kg of bamboo fiber, 18 kg of copper powder, 12 kg of talc powder, 10 kg of mica powder, and 11.8 kg of barium sulfate.

[0076] Preparation process

[0077] Raw material mixing: Put all the above raw materials into a high-speed mixer, set the speed to 500 r / min, and stir for 20 minutes to ensure that the materials are mixed evenly;

[0078] Low-temperature pre-curing: The mixture is loaded into the brake pad mold and then placed in a hot press for pre-curing at a temperature of 110℃ and a pressure of 1.5MPa for 45 minutes;

[0079] Vacuum gradient hot pressing: The pre-cured mold is moved into the vacuum hot pressing equipment, the vacuum degree is evacuated to 0.008MPa, and gradient hot pressing is carried out at a heating rate of 6℃ / min. The operation is carried out sequentially according to the parameters of 140℃ / 5MPa / 20min, 145℃ / 7MPa / 30min, and 150℃ / 9MPa / 20min.

[0080] Post-curing: The hot-pressed blank is taken out, placed in an oven, kept at 160℃ for 8 hours, and then naturally cooled to room temperature before demolding to obtain phenolic resin-based brake pad friction material.

[0081] Performance and compliance indicator test results

[0082] Performance and compliance indicator test results

[0083] The friction material prepared in this embodiment was subjected to third-party testing (according to GB / T 23984-2009, EU REACH Regulation, and Railway Environmental Directive 2024 / 897 / EU). The results are as follows:

[0084] Environmental and compliance indicators: VOC content 3.2g / L, total chlorine + bromine content 650ppm, lead content 6.8ppm, cadmium content 5.2ppm, mercury content 1.3ppm, and hexavalent chromium content 0.8ppm, all meet the preset compliance indicators and are fully compatible with the latest EU and domestic environmental standards. These indicators have been rigorously tested by professional third-party testing institutions, such as Zhongke Testing Technology Service (Guangzhou) Co., Ltd., which has CMA and CNAS qualifications, to ensure the safety and environmental friendliness of the materials.

[0085] Energy consumption indicators: Tested using a heat flow meter, the traditional constant-temperature process (170℃ / 120min) has a unit energy consumption E0 = 800kJ / kg. The gradient process of this invention (140-150℃ / 70min), due to the low-temperature segment accounting for 60% and the pressure holding time being shortened by 42%, has a significantly lower unit energy consumption. The energy consumption reduction rate η = (800-624) / 800×100% = 22%, which meets the requirement of ≥20%, and the production efficiency is increased by 35%;

[0086] Mechanical and tribological properties: Oxygen index 34% (13% higher than traditional halogen-free materials), degree of curing 96.5% (differential scanning calorimetry DSC test, traditional process only 88%), impact strength 4.2kJ / m² (better than industry standard 3.5kJ / m²), coefficient of friction 0.38-0.42 (200-300℃, fluctuation range ±0.02, traditional materials ±0.08), wear rate 0.08cm³ / (MJ) (25% lower than similar products);

[0087] Application Suitability: For high-speed rail brake pads, research shows that the material's braking friction behavior and friction stability are crucial to braking performance. This solution has undergone uninterrupted simulated braking tests, and the friction coefficient of the invented material remains stable between 0.38 and 0.42, with wear only 75% of that of traditional materials, and an expected service life of 350,000 kilometers. Its comprehensive performance not only meets the requirements of the rail transit TB / T 3562-2020 standard and the new energy vehicle QC / T 226-2021 standard, but also exceeds the stringent performance indicators of these standards.

[0088] Comparative experiments and results analysis:

[0089] To verify the synergistic advantages of the technical solution of this invention, five comparative examples (using traditional materials) were set up. Only a single variable was changed, while the remaining raw material ratios and process parameters were consistent with the above embodiments. The test results are shown in the table below:

[0090]

[0091] Conclusions: Comparative Example 1 (single magnesium hydroxide flame retardant) showed an oxygen index of only 28% and an impact strength decrease of 18%, demonstrating the synergistic necessity of the composite flame retardant system; Comparative Example 2 (hexamethyloltrimethylenetetramine curing) showed a VOC of 8.7 g / L and a friction coefficient fluctuation of ±0.07, verifying the irreplaceable nature of cashew phenol derivatives; Comparative Example 3 (constant temperature hot pressing) showed a 0% reduction in energy consumption and a curing degree of 89%, highlighting the innovative value of the gradient process; Comparative Example 4 (insufficient curing agent addition) showed excessive VOC, proving the rationality of the 4-6 wt% addition amount; Comparative Example 5 (single auxiliary filler) showed a decrease in wear resistance, verifying the superiority of the auxiliary filler compound.

Claims

1. A phenolic resin-based friction material, characterized in that, The product comprises the following components: 20-30 wt% phenolic resin, 8-18 wt% halogen-free composite flame retardant system, cashew nut shell extract curing agent, 8-12 wt% reinforcing fiber, 15-20 wt% metal filler, and 25-35 wt% auxiliary filler; the halogen-free composite flame retardant system is composed of magnesium hydroxide whiskers and expandable graphite in a mass ratio of 1:1.5-2.5, wherein the amount of magnesium hydroxide whiskers added is 3-8 wt% and the amount of expandable graphite added is 5-10 wt%; the amount of cashew nut shell extract curing agent added is 4-6 wt% of the mass of phenolic resin.

2. The phenolic resin-based friction material according to claim 1, characterized in that, The reinforcing fiber is bamboo fiber.

3. The phenolic resin-based friction material according to claim 1, characterized in that, The metal filler is copper powder.

4. The phenolic resin-based friction material according to claim 1, characterized in that, The auxiliary filler includes one or more of talc powder, mica powder, and barium sulfate.

5. A preparation process for a phenolic resin-based friction material according to any one of claims 1-4, characterized in that, Includes the following steps: Step 1: Raw material mixing: Mix phenolic resin, halogen-free composite flame retardant system, cashew nut phenol derivative curing agent, reinforcing fiber, metal filler and auxiliary filler evenly to obtain a mixture. Step 2: Low-temperature pre-curing: Place the mixture in a mold and pre-cur it for 30-60 minutes at a temperature of 100-120℃ and a pressure of 1-2MPa. Step 3: Vacuum gradient hot pressing: Place the pre-cured material in a vacuum hot pressing equipment, control the vacuum degree ≤0.01MPa, and perform gradient hot pressing at a heating rate of 5-8℃ / min, sequentially going through three stages: 140℃, pressure 4-6MPa, holding pressure for 20 minutes; 145℃, pressure 6-8MPa, holding pressure for 30 minutes; 150℃, pressure 8-10MPa, holding pressure for 20 minutes. Step 4: Post-curing: Keep the hot-pressed blank at 160℃ for 8 hours, and after it cools naturally to room temperature, demold it to obtain phenolic resin-based friction material.

6. The preparation process of the phenolic resin-based friction material according to claim 5, characterized in that, The temperature for the low-temperature pre-curing was set to 110°C, the pressure to 1.5 MPa, and the time to 45 min.

7. The preparation process of the phenolic resin-based friction material according to claim 6, characterized in that: During vacuum gradient hot pressing, the vacuum level is 0.008 MPa, the heating rate is 6℃ / min, and the pressures at each stage are 5 MPa, 7 MPa, and 9 MPa, respectively.

8. The application of a phenolic resin-based friction material according to any one of claims 1-4 in high-speed rail brake pads or new energy vehicle brake pads.

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