Phosphogypsum whisker reinforced resin-based friction material, preparation method and application

Abstract

The invention discloses a phosphogypsum whisker reinforced resin-based friction material as well as a preparation method and application thereof, and relates to the field of friction materials. The friction material comprises the following components in percentage by mass: 10%-25% of a resin matrix, 15%-30% of reinforced fibers, 5%-20% of a friction performance regulator, 25%-50% of filler and 5%-25% of ardealite whiskers, the length-diameter ratio of the ardealite whisker is greater than 40: 1, and the ardealite whisker is obtained by purification and crystallization treatment of industrial byproduct ardealite and is subjected to surface modification by a coupling agent; a three-dimensional interpenetrating network framework formed by mutually lapping and interweaving ardealite whiskers is arranged in the ardealite whisker composite material, and the preparation method comprises the following steps: slurry preparation and whisker network preforming, in-situ curing and framework locking, compounding and final forming. The ardealite whisker is introduced as a core functional filler, the unique morphology and interface characteristics of the ardealite whisker are utilized, the mechanical strength, friction heat stability and wear resistance of the material are improved, meanwhile, industrial solid waste resource utilization is achieved, and the ardealite whisker is suitable for automobile disc type or drum type brake friction plates.

Description

Technical Field

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

[0002] As the automotive industry moves towards lightweighting, electrification, and high power density, and as global regulations on braking safety and environmental protection become increasingly stringent, resin-based friction materials face unprecedented high-performance challenges. Materials need to maintain a stable coefficient of friction and low wear rate across the entire temperature range, while also possessing excellent mechanical strength. Simultaneously, the industry consensus is to promote copper-free production and the use of environmentally friendly raw materials, driving an urgent need for novel, sustainable reinforcing components.

[0003] Currently, the industry commonly uses multi-component compound fillers, such as various fibers, lubricants, and friction modifiers, to balance performance. However, this technical approach has significant limitations: First, most fillers have a single function, often falling into a "performance seesaw" dilemma; for example, improving high-temperature frictional stability may lead to increased wear or decreased strength. Second, material properties are temperature-sensitive; the effectiveness of different fillers changes with temperature and can even reverse, making it extremely difficult to achieve balanced performance across all operating conditions. More importantly, the interfacial interactions and synergistic mechanisms between complex multi-component components are unclear, leading to a high reliance on trial and error in research and development, and a lack of rational design principles, which restricts performance breakthroughs.

[0004] Therefore, the industry urgently needs an innovative solution that can fundamentally overcome the limitations of traditional fillers, namely, to simultaneously achieve high mechanical strength, excellent frictional stability, low wear, and green sustainability in friction materials without complex compounding or performance compromises. Converting bulk industrial solid waste phosphogypsum into high-performance phosphogypsum whiskers for reinforcing resin matrices offers a highly promising new approach to simultaneously resolve the aforementioned technical contradictions and achieve a leap in the overall performance of materials. Summary of the Invention

[0005] In order to overcome the above-mentioned defects of the prior art, the present invention provides a phosphogypsum whisker-reinforced resin-based friction material, its preparation method and application, to solve the problems mentioned in the background art.

[0006] In a first aspect, embodiments of this application provide a phosphogypsum whisker-reinforced resin-based friction material, comprising the following components by mass percentage: Resin matrix: 10%-25%; Reinforcing fiber: 15%-30%; Friction modifier: 5%-20%; Filler: 25%-50%; Phosphogypsum whiskers: 5%-25%; The internal structure of the phosphogypsum whisker-reinforced resin-based friction material is a three-dimensional interpenetrating network skeleton composed of overlapping and interwoven phosphogypsum whiskers. The three-dimensional interpenetrating network framework has a multi-level porous structure with a porosity between 15% and 35%, and pores with a diameter in the range of 0.5μm to 5μm account for more than 60% of the total pore volume. The aspect ratio of phosphogypsum whiskers is greater than 40:1, and there are secondary crystallization bridging points formed by hydration reaction on the surface. The resin matrix, reinforcing fibers, and other components are filled and encapsulated within a three-dimensional network skeleton.

[0007] In some embodiments of this application, the resin matrix is ​​selected from one or more mixtures of phenolic resin, modified phenolic resin, and epoxy resin.

[0008] In some embodiments of this application, the reinforcing fiber is a mixture of carbon fiber and basalt fiber, wherein the mass ratio of carbon fiber to basalt fiber is 1:1 to 1:4.

[0009] In some embodiments of this application, the friction performance modifier includes graphite, lanthanum oxide, and nano-titanium oxide; wherein, based on the total mass of the friction material, the content of lanthanum oxide is 2%-10%, and the content of nano-titanium oxide is 1%-5%.

[0010] In some embodiments of this application, the filler is selected from at least one of barite, calcium carbonate, kaolin, wollastonite, vermiculite, and tire powder.

[0011] In some embodiments of this application, the aspect ratio of phosphogypsum whiskers is 20:1-50:1, and their surface is modified with silane coupling agents KH550, KH560 or KH792, with the amount of coupling agent added being 0.8%-1.5% of the mass of the phosphogypsum whiskers.

[0012] Secondly, embodiments of this application provide a method for preparing a phosphogypsum whisker-reinforced resin-based friction material, comprising the following steps: S1. Slurry preparation and whisker network preforming: Disperse phosphogypsum whiskers in an aqueous or alcoholic solution containing a resin matrix to form a uniform slurry with a solid content of 30%-50%; Inject the slurry into a mold and perform vacuum filtration or pressure filtration at a pressure of 0.5MPa-2MPa and a temperature of 40℃-60℃ to remove some liquid, so that the whiskers are pre-arranged in the mold and form a wet porous network preform; S2. In-situ curing and skeleton locking: The wet preform obtained in step S1, together with the mold, is placed in a controlled humidity environment and treated for 2-4 hours at 65℃-85℃ and relative humidity of 70%-90% to pre-cur the resin and promote local dissolution and recrystallization on the surface of phosphogypsum whiskers, forming bridging points between whiskers and locking the three-dimensional network structure. S3. Composite and final molding: In the pores of the preform treated in step S2, reinforcing fibers, friction modifiers and fillers are sequentially filled, and then final hot pressing and curing are carried out; the hot pressing conditions are: temperature 150℃-170℃, pressure 15MPa-25MPa, and the holding time is calculated as 60-90 seconds per millimeter of product thickness.

[0013] In some embodiments of this application, the slurry also contains a dispersant comprising 0.1%-0.5% of the mass of phosphogypsum whiskers.

[0014] In some embodiments of this application, after final hot-press curing, a step-curing step is also included, specifically: the product is kept at 120°C, 160°C and 180°C for 1-2 hours each.

[0015] Thirdly, embodiments of this application provide the application of phosphogypsum whisker-reinforced resin-based friction materials in the preparation of automotive brake friction pads.

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. By introducing 5%-25% of phosphogypsum whiskers with a specific aspect ratio (>20) as the core functional phase into the formulation system, its unique microstructure and mechanical properties achieve simultaneous optimization of multiple properties: On the one hand, the whiskers play a significant role in rigid load bearing and bridging in the matrix, effectively transferring and dispersing stress, thereby improving the mechanical strength (such as shear strength) of the material; on the other hand, its moderate hardness and thermal stability can participate in the formation of a stable and moderate friction interface during braking in a wide temperature range, which not only inhibits the thermal decay of the friction coefficient, but also significantly reduces the wear rate by reducing the brittle spalling of the surface material, thus taking into account the key properties that are traditionally inversely related in a single modification.

[0017] 2. As a multifunctional integrated filler, phosphogypsum whiskers, after surface purification and optional coupling agent treatment, exhibit good compatibility with the resin matrix. They can be uniformly dispersed in conventional high-speed dry mixing processes, avoiding the complex compounding designs and stringent mixing processes required in traditional methods to harmonize the properties of multiple fillers. This reduces reliance on specialized mixing equipment and precise temperature control, making the production process easier to control and improving batch-to-batch consistency. Thus, cost reduction and efficiency improvement are achieved from both material design and manufacturing process perspectives.

[0018] 3. The core component, phosphogypsum whiskers, is derived from the deep processing of bulk industrial solid waste phosphogypsum, achieving high-value utilization of waste resources and aligning with environmental protection trends. This solution starts from the source of raw materials, improving the overall performance of the material while avoiding the use of potentially environmentally controversial components (such as some metal fillers) found in traditional friction materials. It responds to the industry's urgent need for copper-free and green manufacturing, achieving a balance between environmental benefits and product performance.

[0019] 4. Based on the reinforcing and interface regulation effects of phosphogypsum whiskers, the prepared material exhibits a smoother coefficient of friction-temperature curve. This means that the frictional performance changes more evenly during braking from low to high temperatures, and the resistance to thermal fading and recovery are improved. This stable frictional behavior directly translates into more reliable braking performance, lower braking noise and vibration tendency, and longer service life, thereby comprehensively improving the safety, comfort, and reliability of the braking system. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0021] Figure 1 The bending strength comparison bar chart provided for this invention; Figure 2 A comparison chart of friction coefficient-temperature change curves provided for this invention; Figure 3 A scatter plot showing the correlation between wear rate and overall performance provided by this invention; Figure 4 A comprehensive radar chart comparing key performance indicators provided for this invention. Detailed Implementation

[0022] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] To enable those skilled in the art to better understand the present application, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] In terms of raw material proportions, the embodiments of this application, by weight percentage, consist of the following components: 10%-25% resin matrix, 15%-30% reinforcing fiber, 5%-20% friction modifier, 25%-50% filler, and 5%-25% phosphogypsum whiskers. The phosphogypsum whiskers have an aspect ratio greater than 40:1, an average diameter of 1-10 μm, and an average length of 50-300 μm. A key feature of the material of this invention is its internal three-dimensional interpenetrating network skeleton, formed by the overlapping and interwoven phosphogypsum whiskers locked through secondary crystallization bridging points. This specific morphology and structure enable the phosphogypsum whiskers not only to serve as a highly efficient reinforcing phase, constructing a rigid load-bearing network in the matrix to significantly improve mechanical strength, but also, with their moderate hardness and excellent thermal stability, to directly participate in and stabilize the friction interface, thereby synergistically optimizing the friction coefficient stability and wear resistance of the material over a wide temperature range.

[0025] In terms of process, the embodiments of this application employ a specially designed preparation method to construct the aforementioned three-dimensional interpenetrating network skeleton. This process abandons the simple blending approach and actively constructs and locks the micro-network structure of phosphogypsum whiskers through slurry preforming and controlled curing steps. Specifically, it includes: firstly, dispersing surface-modified phosphogypsum whiskers in an aqueous or alcoholic solution containing a resin matrix to form a uniform slurry, followed by vacuum filtration / pressure filtration to dehydrate and form a wet network preform; then, in-situ curing is performed under precisely controlled temperature and humidity conditions to induce a dissolution-recrystallization reaction on the whisker surface, forming bridging points, thereby permanently locking the three-dimensional network skeleton; finally, reinforcing fibers, friction modifiers, and fillers are composited into this skeleton, and the final product is obtained through hot pressing and post-curing treatment.

[0026] The complete process steps of this application are as follows: S1. Slurry preparation and whisker network preforming: Surface-modified phosphogypsum whiskers are dispersed in an aqueous solution containing a resin matrix (such as phenolic resin) to form a uniform slurry with a solid content of 30%-50%; the slurry is injected into a mold and vacuum filtered or pressure filtered at a pressure of 0.5MPa-2MPa and a temperature of 40℃-60℃ to remove some liquid, so that the whiskers are pre-arranged in the mold and form a wet porous network preform.

[0027] S2. In-situ curing and skeleton locking: The wet preform obtained in step S1, together with the mold, is placed in a controlled humidity environment and treated for 2-4 hours at 65℃-85℃ and relative humidity of 70%-90% to pre-cur the resin and promote local dissolution and recrystallization on the surface of phosphogypsum whiskers, forming bridging points between whiskers, thereby locking the three-dimensional network structure.

[0028] S3. Composite and final molding: In the pores of the preform treated in step S2, reinforcing fibers, friction modifiers and fillers are sequentially filled, and then final hot pressing and curing are carried out; the hot pressing conditions are: temperature 150℃-170℃, pressure 15MPa-25MPa, and the holding time is calculated as 60-90 seconds per millimeter of product thickness.

[0029] In this application, the phosphogypsum whiskers have an aspect ratio greater than 40:1, an average diameter of 1-10 μm, and an average length of 50-300 μm, preferably an aspect ratio greater than 50:1, an average diameter of 2-5 μm, and an average length of 80-200 μm. This specific elongated morphology is the geometric basis for its uniform dispersion and interlocking in the slurry to form a three-dimensional interpenetrating network skeleton. This morphology ensures that the whiskers can exert the optimal "bridging" reinforcement effect in the final composite material, effectively transferring and dispersing stress; at the same time, as micro-protrusions on the friction surface, they help to form and maintain a stable friction interface, thereby synergistically improving the mechanical strength and tribological properties of the material.

[0030] In this application, the resin matrix is ​​selected from one or more mixtures of phenolic resin, modified phenolic resin, and epoxy resin. Specifically, in step S1, a water-soluble or water-dispersible phenolic resin (such as methyl phenolic resin) is preferably used to ensure that it can be uniformly dissolved or dispersed in an aqueous solution and blended with phosphogypsum whiskers to form a stable slurry. The reinforcing fiber is a mixture of carbon fiber and basalt fiber, wherein the mass ratio of carbon fiber to basalt fiber is 1:1 to 1:4. This hybrid fiber system, after finally filling the pores of the three-dimensional network skeleton, can provide a macroscopic reinforcement effect that combines rigidity and flexibility. The friction modifier includes graphite, lanthanum oxide, and nano-titanium oxide. This combination aims to provide lubrication through graphite and enhance high-temperature interfacial stability through lanthanum oxide and nano-titanium oxide, jointly ensuring the stability of the friction coefficient of the material over a wide temperature range. The filler is selected from at least one of barite, calcium carbonate, kaolin, wollastonite, vermiculite, and tire powder, and its main function is to adjust the material density, cost, and processability. Before preparing the slurry, phosphogypsum whiskers must be surface modified with silane coupling agents (such as KH550, KH560 or KH792) to significantly improve their interfacial compatibility and bonding force with the resin matrix. This is a key prerequisite for constructing a robust three-dimensional network structure.

[0031] In some embodiments of this application, the slurry preparation in step S1 is a crucial starting point. The drying pretreatment of phosphogypsum whiskers needs strict control, typically involving drying at 150°C for 4 hours to fully remove adsorbed water without damaging the whisker structure. For subsequent coupling agent modification, a water-based or water-alcohol mixture of silane coupling agent solutions is recommended, with a concentration of 1-2 wt%, to ensure effective action on the whisker surface in a water-based slurry system. The solid content of the slurry must be precisely controlled between 30% and 50%. Too low a solid content results in poor strength after skeleton formation and a long dehydration time; too high a solid content leads to poor slurry fluidity, making it difficult to uniformly disperse and achieve good pre-alignment of the whiskers. Uniform dispersion requires the use of high-speed shearing equipment.

[0032] In some embodiments of this application, the pressure (0.5-2 MPa) and temperature (40-60°C) conditions of the vacuum filtration or pressure filtration molding process in step S1 are crucial for forming a wet preform with a reasonable porosity structure. Appropriate pressure promotes the close bonding of whiskers during dehydration, forming a preliminary network; while a suitable temperature maintains the resin in a dissolved state, which is beneficial for subsequent steps. The porous network preform formed at this stage is the foundation for all subsequent functions.

[0033] In some embodiments of this application, the in-situ curing and framework locking in step S2 are central to forming a permanent three-dimensional network. The wet preform is carefully treated in a controlled environment of 65°C-85°C and 70%-90% relative humidity for 2-4 hours. Under this mild heat and humidity environment, the resin pre-cures, giving the preform initial strength; simultaneously, a controlled local dissolution-recrystallization process occurs on the surface of the phosphogypsum whiskers, forming strong secondary crystallization bridging points at the contact points between the whiskers, thereby "locking" the physically bonded network into a chemically bonded and stable framework. Insufficient humidity results in incomplete bridging reaction, while excessive humidity or prolonged treatment may lead to excessive dissolution and structural damage.

[0034] In some embodiments of this application, the composite and final molding in step S3 determine the final material properties. When filling the pre-locked network skeleton with a mixture of reinforcing fibers, friction modifiers, and fillers, vibration-assisted methods can be used to ensure dense filling. Subsequent hot-pressing curing requires a temperature (150-170°C) that ensures the resin is completely melted and wets all components, a pressure (15-25 MPa) sufficient to expel residual gas and achieve high material density, and a holding time (60-90 seconds per millimeter of thickness) to ensure full cross-linking and curing of the resin. This hot-pressing process is not simply compaction, but rather a final impregnation, bonding, and fixation of the pre-formed skeleton and its pores by the resin melt under high pressure and high temperature.

[0035] In some embodiments of this application, after the final hot-press curing, a stepped post-curing step may be included (e.g., holding at 120°C, 160°C, and 180°C for 1-2 hours each). This step aims to promote complete curing of the resin, eliminate internal stress, and further improve the heat resistance, dimensional stability, and thermal stability of the frictional properties of the material, which is particularly important for components such as automotive brake pads that need to withstand extreme operating conditions.

[0036] The following detailed description of the phosphogypsum whisker-reinforced resin-based friction material and its preparation method, with reference to specific embodiments, illustrates this application in detail. In each embodiment, raw materials are expressed as a percentage by weight, and the process steps are the same as the aforementioned complete process steps, although some parameters may differ.

[0037] Example 1 This embodiment aims to verify the overall reinforcing effect of phosphogypsum whiskers at a medium content (10%) and to establish basic process parameters.

[0038] S1: Pretreatment and Slurry Preparation Phosphogypsum whiskers, obtained through purification and crystallization of industrial by-product phosphogypsum, had an average diameter of approximately 3 μm, an average length of approximately 120 μm, and an aspect ratio of approximately 40. These whiskers were dried at 150 °C for 4 hours, cooled, and then surface-modified using a silane coupling agent, KH550, at an addition rate of 1.0% of the whisker's mass. The modified whiskers were dispersed in an aqueous solution containing 20% ​​phenolic resin and stirred to form a homogeneous slurry with a solid content of 40%.

[0039] S2: Network Preforming and Locking The slurry is injected into a flat mold and vacuum filtered at 1.0 MPa pressure and 50°C to form a wet network preform. The preform is then transferred to a humidity control chamber and treated at 75°C and 80% relative humidity for 3 hours to pre-cure the resin. Simultaneously, secondary crystallization bridging points are formed on the whisker surface, locking in the three-dimensional network.

[0040] S3: Component filling and thermosetting curing The pores of the network preform were sequentially filled with carbon fiber (8%), basalt fiber (7%), graphite (8%), lanthanum oxide (2%), nano-titanium oxide (2%), barite (32%), and calcium carbonate (10%). The mold was closed and hot-pressed at 160℃ and 20MPa, with the holding time calculated based on the thickness. After demolding, a stepped post-curing process was performed: holding at 120℃, 160℃, and 180℃ for 1.5 hours each.

[0041] Example 2 This embodiment aims to explore the influence trend of high phosphogypsum whiskers (20%) on material properties, especially the upper limit of its reinforcing effect and potential interface problems.

[0042] Formulation and process adjustments: The content of phosphogypsum whiskers in the formulation was increased to 20%. To ensure 100% total formulation quality, the amount of inert filler barite was reduced proportionally (from 32% to 22%). All other component ratios, whisker pretreatment parameters, mixing sequence and time, hot pressing and post-curing temperature regimes were strictly maintained as in Example 1.

[0043] Performance expectations and concerns: Doubling the whisker content is expected to further improve the material's rigidity (flexural strength, hardness) and high-temperature stability, but it may also lead to increased brittleness, changes in wear rate, or a decrease in the recovery coefficient due to the dramatic increase in interface area, insufficient resin coating of whiskers, or increased risk of whisker agglomeration. By comparing with Example 1, the optimal addition range can be clearly defined.

[0044] Comparative Example 1 This comparative example serves as a benchmark for traditional whisker-free reinforced systems, employing a simple compounding approach common in the industry. The formulation in this comparative example is completely free of phosphogypsum whiskers; the missing 10% volume is replaced by an equal amount of barite (increasing the total barite content to 42%). This is a typical design of "resin + fiber + lubricant / friction enhancer + inexpensive filler." Except for the pretreatment step that does not involve whiskers, all process parameters for mixing, hot pressing, and post-curing are identical to those in Example 1. This ensures that performance differences are entirely attributable to changes in formulation composition, rather than process variations.

[0045] The specific formulations of Examples 1, 2 and Comparative Example 1 are shown in Table 1.

[0046] Table 1 ; The friction materials prepared in Examples 1 and 2 and Comparative Example 1 were subjected to performance testing. The test indicators included: flexural strength (MPa), Rockwell hardness (HRM), coefficient of friction (μ) at different temperatures, and wear rate (10). -7 cm 3 The results of the coefficient of frictional decay at 350℃ and the coefficient of recovery are shown in Table 2.

[0047] Table 2 ; Combining the data in Tables 1 and 2, the influence of each parameter and raw material on performance can be derived, and the specific analysis is as follows: 1. Elucidation of the mechanical property enhancement mechanism based on three-dimensional network skeleton Reference Figure 1The flexural strength comparison bar chart shows that the test results of Examples 1 and 2 are significantly higher than those of Comparative Example 1. This is not due to simple filler addition, but rather to the core structural reinforcement effect directly contributed by the three-dimensional interpenetrating network skeleton of phosphogypsum whiskers constructed in this invention. The core mechanism lies in the fact that, through slurry molding and moisture locking, phosphogypsum whiskers pre-form a continuous, interconnected, and rigid network reinforced by secondary crystallization bridging points. This network acts as the main load-bearing skeleton throughout the material. When the material is subjected to external forces (such as flexural stress), the load is efficiently transferred and distributed to this continuous rigid network through the resin matrix. The network skeleton, through its internally interconnected whisker "beams" and strong bridging "nodes," rapidly disperses local stress, effectively suppressing the initiation of microcracks and hindering crack propagation paths. The higher strength of Example 2 compared to Example 1 demonstrates that under the described process, the increased density (whisker content) of the network skeleton further enhances its load-bearing and force-transfer capabilities, proving the effectiveness and controllability of this structural reinforcement mechanism.

[0048] 2. Structural reasons for improved frictional performance and thermal stability Reference Figure 2 The friction coefficient-temperature curves shown in Examples 1 and 2 are much flatter and show only slight decay in the high-temperature range (200-350℃) compared to Comparative Example 1. This excellent resistance to thermal degradation is mainly attributed to the high-temperature interfacial stability provided by this structure. In traditional materials, high temperatures lead to resin softening, lubricant failure, and interfacial support collapse. However, in this invention, the phosphogypsum whisker three-dimensional network framework constructed by the S1-S3 process exhibits excellent thermal stability. It not only maintains structural integrity at high temperatures but also acts as a durable micro-protrusion support phase in the friction interface, continuously providing mechanical engagement and micro-cutting effects, compensating for the negative impact of high-temperature failure of organic components. Simultaneously, the functional friction modifiers (lanthanum oxide and nano-titanium oxide) uniformly dispersed and embedded in the network pores work synergistically at high temperatures, further stabilizing the tribochemical reaction film. Therefore, the friction coefficient remains highly stable over a wide temperature range.

[0049] 3. Structural safeguards that synergistically optimize wear resistance and frictional stability Reference Figure 3The wear rate-friction stability correlation diagram shown focuses on the "low wear, low fluctuation" region. This demonstrates the dual inhibitory effect of the three-dimensional network skeleton on wear behavior. First, the skeleton significantly improves the overall rigidity and strength of the material (as mentioned above), making the material surface less prone to plastic deformation and flaking under frictional shear. Second, and more importantly, the continuous network structure itself effectively hinders the propagation of subsurface cracks during friction. When microcracks are generated at the friction interface, their propagation paths are repeatedly deflected and blocked by the interwoven whisker network, consuming a large amount of energy, thus making it difficult for cracks to merge and develop into macroscopic damage leading to the shedding of large particles. In addition, the stable friction interface reduces adhesive wear and vibration. The synergy of these three factors allows the wear process to proceed in a gentler and more uniform manner, achieving a balance between low wear rate and high frictional stability.

[0050] 4. Balanced improvement in overall performance and integrated structural-functional value Reference Figure 4 The radar chart showing the overall performance demonstrates that the embodiment outperforms the comparative embodiment across multiple dimensions, exhibiting a fuller and more balanced profile. This directly confirms that the present invention achieves an integrated design of material structure enhancement, interface stability, and wear protection through the construction of a three-dimensional network framework. This framework is not a single functional component but simultaneously serves as a "load-bearing structure," a "thermally stable interface support," and a "crack propagation barrier," synergistically enhancing various key performance aspects through a physical mechanism. From an environmental perspective, the core raw material of this framework, phosphogypsum whiskers, originates from industrial solid waste, and its high-value application gives this high-performance material outstanding green attributes.

[0051] 5. Summary of the innovative points of this invention (1) Structural Innovation and Performance Breakthrough: This invention transcends the traditional approach of simple physical blending of fillers, actively constructing a three-dimensional interpenetrating network framework with phosphogypsum whiskers within the resin-based friction material. This framework is a stable structure with multi-level porosity and chemical bridging points, achieving for the first time in friction materials a three-in-one integration of "load-bearing framework," "thermally stable phase," and "wear-resistant barrier." Experimental data show that this structural innovation fundamentally solves the performance synergy problem: while maintaining the coefficient of friction at 300℃ above 0.40, the wear rate is reduced by approximately 29% compared to traditional materials, and the room temperature flexural strength is increased by more than 13%.

[0052] (2) Process Innovation and Industrial Integration: In line with the above-mentioned structural innovation, this invention provides a complete and controllable dedicated preparation method. The core of this method lies in first constructing and locking the inorganic whisker network through a wet process, and then compounding it with other organic and powder components (S3). This process path is clear, and the parameters are well-defined (such as solid content, humidity, pressure, and temperature range), perfectly reproducing the claimed microstructure and ensuring the repeatability and reliability of the patented technology. Although this method is designed to obtain a special structure, the equipment used (dispersion, filtration, temperature and humidity control, hot pressing) are all general-purpose or easily upgraded industrial equipment, possessing good potential for industrialization.

[0053] (3) Thorough verification and clear objectives: Through a systematic comparison of Examples 1 and 2 with Comparative Example 1, this invention clearly verifies the decisive influence of the presence or absence of a three-dimensional network skeleton on the final performance, and clarifies the performance control window of key process parameters (such as whisker content). All performance advantages are supported by solid experimental data, forming a complete logical closed loop from "special structure design" to "dedicated process implementation" and then to "superior performance verification". This invention not only provides a high-performance product, but also a new method for preparing functional composite materials with specific reinforcement structures. The technology is highly portable and has broad application prospects.

[0054] In conclusion, the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A phosphogypsum whisker-reinforced resin-based friction material, characterized in that, It consists of the following components by mass percentage: Resin matrix: 10%-25%; Reinforcing fiber: 15%-30%; Friction modifier: 5%-20%; Filler: 25%-50%; Phosphogypsum whiskers: 5%-25%; The phosphogypsum whisker-reinforced resin-based friction material has a three-dimensional interpenetrating network skeleton formed by the overlapping and interweaving of phosphogypsum whiskers. The three-dimensional interpenetrating network skeleton has a multi-level porous structure with a porosity between 15% and 35%, and pores with a diameter in the range of 0.5μm to 5μm account for more than 60% of the total pore volume. The phosphogypsum whiskers have an aspect ratio greater than 40:1 and have secondary crystallization bridging points formed by hydration reaction on their surface. The resin matrix, reinforcing fibers, and other components are filled and encapsulated within the three-dimensional network skeleton.

2. The phosphogypsum whisker-reinforced resin-based friction material according to claim 1, characterized in that, The resin matrix is ​​selected from one or more mixtures of phenolic resin, modified phenolic resin, and epoxy resin.

3. The phosphogypsum whisker-reinforced resin-based friction material according to claim 1, characterized in that, The reinforcing fiber is a mixture of carbon fiber and basalt fiber, wherein the mass ratio of carbon fiber to basalt fiber is 1:1 to 1:

4.

4. The phosphogypsum whisker-reinforced resin-based friction material according to claim 1, characterized in that, The friction performance modifier includes graphite, lanthanum oxide, and nano-titanium oxide; wherein, based on the total mass of the friction material, the content of lanthanum oxide is 2%-10%, and the content of nano-titanium oxide is 1%-5%.

5. The phosphogypsum whisker-reinforced resin-based friction material according to claim 1, characterized in that, The filler is selected from at least one of barite, calcium carbonate, kaolin, wollastonite, vermiculite, and tire powder.

6. The phosphogypsum whisker-reinforced resin-based friction material according to claim 1, characterized in that, The phosphogypsum whiskers have an aspect ratio of 20:1-50:1, and their surface is modified with silane coupling agents KH550, KH560 or KH792, with the amount of coupling agent added being 0.8%-1.5% of the mass of the phosphogypsum whiskers.

7. A method for preparing a phosphogypsum whisker-reinforced resin-based friction material, characterized in that, Includes the following steps: S1. Slurry preparation and whisker network preforming: Disperse phosphogypsum whiskers in an aqueous or alcoholic solution containing the resin matrix to form a uniform slurry with a solid content of 30%-50%; Inject the slurry into a mold and perform vacuum filtration or pressure filtration at a pressure of 0.5MPa-2MPa and a temperature of 40℃-60℃ to remove some liquid, so that the whiskers are pre-arranged in the mold and form a wet porous network preform; S2. In-situ curing and skeleton locking: The wet preform obtained in step S1, together with the mold, is placed in a controlled humidity environment and treated for 2-4 hours at 65℃-85℃ and relative humidity of 70%-90% to pre-cur the resin and promote local dissolution and recrystallization on the surface of phosphogypsum whiskers, forming bridging points between whiskers and locking the three-dimensional network structure. S3. Composite and final molding: In the pores of the preform treated in step S2, reinforcing fibers, friction modifiers and fillers are sequentially filled, and then final hot pressing and curing are carried out; the hot pressing conditions are: temperature 150℃-170℃, pressure 15MPa-25MPa, and the holding time is calculated as 60-90 seconds per millimeter of product thickness.

8. The method for preparing a phosphogypsum whisker-reinforced resin-based friction material according to claim 7, characterized in that, The slurry also contains a dispersant comprising 0.1%-0.5% of the mass of phosphogypsum whiskers.

9. The method for preparing a phosphogypsum whisker-reinforced resin-based friction material according to claim 7, characterized in that, After the final hot-press curing, a stepped post-curing step is also included, specifically: the product is kept at 120℃, 160℃, and 180℃ for 1-2 hours each.

10. The application of a phosphogypsum whisker-reinforced resin-based friction material according to any one of claims 1 to 7 in the preparation of automotive brake friction pads.

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