Freeze-thaw-resistant and salt-corrosion-resistant polymer modified EPDM safety brick and preparation method thereof

Abstract

The invention provides a freeze-thaw-resistant and salt-corrosion-resistant polymer modified EPDM safety brick and a preparation method thereof, and belongs to the technical field of building materials, the freeze-thaw-resistant and salt-corrosion-resistant polymer modified EPDM safety brick is prepared from the following components by mass: 80-120 parts of pre-vulcanized EPDM particles, 30-50 parts of polyolefin elastomer (POE), 3-8 parts of a compatilizer, 20-40 parts of modified red brick powder, 1-3 parts of an antioxidant, 3-5 parts of a foaming agent, 1.5-3.5 parts of a lubricant, and 3-5 parts of tackifying resin. The pre-vulcanized EPDM particles and the modified red brick powder are introduced, and a hot-pressing foaming process is combined, so that the freeze-thaw resistance, the salt corrosion resistance and the mechanical property of the material are remarkably improved; the wear resistance, the skid resistance and the rainwater diversion effect are further enhanced through the surface strengthening layer and the micro-texture design, and the pavement is suitable for pavement of roads and squares in severe cold and high-salt corrosion environments.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a polymer-modified EPDM safety brick that is resistant to freeze-thaw cycles and salt corrosion, and its preparation method. It is particularly suitable for road paving environments in cold regions, coastal areas, and areas where de-icing salt is used. Background Technology

[0002] In cold-region engineering construction and urban paving, conventional paving materials such as ceramic bricks and concrete bricks face the dual challenges of freeze-thaw cycles and salt corrosion. Freeze-thaw cycles cause repeated freezing and expansion of internal moisture and thawing and contraction, generating internal stress that leads to cracking and peeling. Salt corrosion accelerates material aging, especially in road environments using de-icing salt, where chloride ion penetration causes structural damage and performance degradation. Therefore, developing a new type of paving material with excellent mechanical properties, freeze-thaw resistance, and salt corrosion resistance to meet the special requirements of cold and salt-corrosion environments has become an urgent technical problem to be solved.

[0003] Currently, commonly used paving materials on the market mainly include ceramic tiles, concrete bricks, and natural stone. These materials have significant shortcomings in terms of weather resistance: ceramic tiles are prone to cracking in freeze-thaw environments, while concrete bricks are porous and easily absorb water, resulting in poor durability in salt-corrosion environments. Although increasing the material density or adding air-entraining agents can improve freeze-thaw resistance to some extent, it often leads to a decline in other properties, such as reduced abrasion resistance or weakened flexural strength.

[0004] Ethylene propylene diene monomer (EPDM) rubber, as a synthetic rubber, has attracted attention for its excellent weather resistance, ozone resistance, and temperature adaptability. Its saturated backbone in its molecular structure gives it outstanding resistance to ultraviolet radiation, ozone, and extreme temperatures. However, traditional EPDM materials also have some limitations when used in paving materials: firstly, its resistance to compression set is insufficient, especially in high humidity or water-based environments; secondly, unmodified EPDM has limited resistance to salt corrosion; and thirdly, EPDM materials have low rigidity, making them unsuitable for direct use as paving materials.

[0005] Several studies have been conducted in the prior art attempting to improve the performance of EPDM. Patent CN119081300A discloses a modified EPDM rubber material with high resilience and low compression set resistant to seawater erosion, along with its preparation method and applications. By adding components such as zinc methacrylate and p-benzoquinone dioxime, the high-temperature thermo-oxidative aging resistance, hydrothermal aging resistance, and compression set resistance in high-concentration seawater environments of EPDM are improved. Patent CN119859355A discloses a EPDM rubber foam material based on modified red brick powder and its preparation method. By surface-modifying the red brick powder, its dispersibility, compatibility, and mechanical reinforcement effect in the EPDM matrix are improved. Then, it is uniformly dispersed in the EPDM matrix. Through optimized foaming processes, high strength, low density, and excellent cell structure are achieved in the foam material. The invented EPDM foam material exhibits excellent mechanical properties, flame retardancy, and cell structure. In addition, patent CN105017674A discloses a low-temperature frost-resistant double-wall corrugated PVC pipe modified by composite toughening of EPDM and CPE and its production method, which uses EPDM and CPE composite toughening to improve low-temperature frost resistance.

[0006] However, these technologies each have their limitations: simple rubber-modified materials lack sufficient rigidity and are unsuitable as paving materials; while overly rigid composite materials often have poor impact resistance and lack sufficient freeze-thaw resistance and salt corrosion resistance. Therefore, it is necessary to develop a new type of paving material that combines excellent mechanical properties, freeze-thaw resistance, and salt corrosion resistance to meet the special requirements of cold regions and salt-corrosion environments. Summary of the Invention

[0007] This invention provides a polymer-modified EPDM safety brick that is resistant to freeze-thaw cycles and salt corrosion, and its preparation method. It is particularly suitable for paving scenarios such as roads and squares in extremely cold regions and high-salt corrosion environments. By introducing pre-vulcanized EPDM rubber particles, modified red brick powder, and a surface reinforcement layer, combined with low-temperature dry mixing, hot-pressing foaming molding, and micro-texturing processing technology, the freeze-thaw resistance, salt corrosion resistance, and comprehensive mechanical properties of the material are significantly improved.

[0008] The technical solution of the present invention is as follows: A polymer-modified EPDM safety brick resistant to freeze-thaw cycles and salt corrosion, comprising the following components by weight: 80-120 parts of pre-vulcanized EPDM rubber granules (20-80 mesh); 30-50 parts of polyolefin elastomer (POE); 3-8 parts compatibilizer 20-40 parts of modified red brick powder; Antioxidant 1-3 parts; 3-5 parts of foaming agent; 1.5 to 3.5 parts of lubricant; 3-5 parts of tackifying resin; The method for preparing the modified red brick powder includes crushing waste red bricks and treating them alternately with hydrochloric acid solution and sodium hydroxide solution, then mixing them with polyacrylamide and hydroxypropyl distarch phosphate for surface modification, with the particle size controlled at 200-300 mesh. The polymer-modified EPDM safety brick has a nano-SiO2-silane coupling agent composite reinforcement layer on its surface, and the density of the nano-SiO2 is 2-5 g / m³. 2 .

[0009] Preferably, the compatibilizer is maleic anhydride-grafted EPDM (EPDM-g-MAH), which forms a physical entanglement with the hydrophilic film on the surface of the modified red brick powder through its polar groups, thereby further optimizing the dispersibility and interfacial compatibility of the filler in the matrix.

[0010] Preferably, the foaming agent is a composite system of azodicarbonamide and sodium bicarbonate, with a mass ratio of 2-3:1.

[0011] Preferably, the tackifying resin is C5 petroleum resin or C9 petroleum resin. A method for preparing a polymer-modified EPDM safety brick resistant to freeze-thaw cycles and salt corrosion includes the following steps: Step S1: Raw material pretreatment and surface modification; Step S2: Low-temperature dry mixing; Step S3: Material spreading and hot-press foaming molding; Step S4: Cooling and setting; Step S5: Surface strengthening and microtexturing.

[0012] Preferably, the raw material pretreatment and surface modification include surface activation of pre-vulcanized EPDM rubber particles and preparation of modified red brick powder; the surface activation of the pre-vulcanized EPDM rubber particles is selected from either mild ozone treatment or plasma treatment, and the surface activation of the pre-vulcanized EPDM rubber particles forms oxygen-containing functional groups through ozone or plasma treatment, thereby improving the interfacial bonding strength between the particles and the polyolefin elastomer matrix; the preparation of modified red brick powder includes the following steps: crushing waste red bricks and then sequentially performing acid washing and alkali treatment. For the washing treatment, first soak the brick powder in a 5%-10% hydrochloric acid solution for 2-4 hours, then rinse it with deionized water until neutral, and then soak it in an 8%-12% sodium hydroxide solution for 1-2 hours, and wash it again until neutral. Mix the treated brick powder with polyacrylamide and hydroxypropyl distarch phosphate, and stir it in a high-speed mixer at a speed of 1000-1500 rpm for 30-60 minutes to complete the surface modification, and finally obtain modified brick powder with a particle size of 200-300 mesh.

[0013] The introduction of modified red brick powder significantly improves its interfacial compatibility with the EPDM rubber matrix and the polymer binder phase (POE), avoiding the mechanical property degradation problem caused by poor dispersibility of traditional fillers. The role of polyacrylamide and hydroxypropyl distarch phosphate is to form a hydrophilic film on the surface of the red brick powder through chemical bonding, further enhancing its interfacial compatibility with POE and improving its dispersibility and binding force in the composite material.

[0014] Preferably, the low-temperature dry mixing includes the following steps: pre-vulcanized EPDM rubber granules, polyolefin elastomer, and maleic anhydride-grafted EPDM are put into a high-speed mixer and thoroughly mixed at a temperature below 60°C. Then, modified red brick powder, antioxidant, foaming agent, lubricant, tackifying resin, and all other components are added and thoroughly mixed at a temperature below 60°C to ensure that each component is uniformly dispersed and a uniform dry mix is ​​obtained.

[0015] Ethylene propylene diene monomer (EPDM) rubber provides excellent weather resistance and temperature adaptability as a base material, while the introduction of polyolefin elastomers enhances the overall rigidity and impact resistance of the material.

[0016] Preferably, the spreading and hot-press foaming molding process includes the following steps: weighing the mixed dry material and spreading it evenly in a preheated mold cavity; closing the mold, rapidly applying a pressure of 10-15 MPa and heating to 160-180°C, under these conditions, the POE particles rapidly melt into a viscous flow state, encapsulating and impregnating the EPDM particles and fillers. Simultaneously, the foaming agent decomposes to generate gas, forming cells in the molten POE matrix. Maintaining pressure and time allows the material to be fully "plasticized" and foamed.

[0017] Azodicarbonamide decomposes at high temperatures to produce nitrogen gas, while sodium bicarbonate releases carbon dioxide. The synergistic effect of these two gases results in a more uniform cell distribution. Precise control of molding pressure during the foaming process prevents excessive cell expansion or collapse, thus forming a foamed structure with excellent mechanical properties.

[0018] Preferably, the cooling and shaping includes the following steps: rapidly cooling the entire mold to below 60°C using a cooling water system, causing the POE melt to recrystallize and solidify, fixing the EPDM particles and foam structure together to form the final product shape; depressurizing, opening the mold, and removing the brick blank.

[0019] Preferably, the surface strengthening and microtexturing process includes the following steps: glazing the surface of the formed brick; uniformly coating the surface of the brick with a surface treatment liquid prepared by mixing a silane coupling agent and nano-silica using a spraying method; and then curing at 100-120℃ for 30-60 minutes. After curing, a microtexture pattern with a depth of 0.1-0.3 mm is processed on the surface of the brick using a laser engraving device.

[0020] The synergistic effect of silane coupling agents and nano-silica forms a dense protective film on the brick surface, significantly improving the material's wear resistance and salt corrosion resistance. Microtexturing not only enhances the brick's anti-slip properties but also improves rainwater drainage by increasing surface roughness.

[0021] This invention addresses the environmental challenges and high energy consumption associated with traditional vulcanization processes through systematic improvements in substrate composition control, composite material microstructure optimization, and integrated functionalization and substrate bonding processes. Simultaneously, a unique composite material design enables the product to meet paving material standards for freeze-thaw resistance, salt corrosion resistance, and sufficient mechanical strength without vulcanization. The introduction of modified red brick powder significantly enhances the material's rigidity and mechanical properties, while the foaming process imparts lightweight and high-strength characteristics. Surface strengthening further ensures the stability and durability of the material's properties.

[0022] The technical advantages of this invention are reflected in the following aspects: In terms of composition: By selecting a variety of high-performance raw materials and combining them with surface modification treatment, the interfacial compatibility between different components is significantly improved, avoiding the performance degradation problem caused by poor dispersibility in traditional composite materials. At the same time, the introduction of silane coupling agents and nano-silica achieves a high degree of unity between surface strengthening and salt corrosion resistance.

[0023] In terms of technology: the complex "vulcanization process" that relies on precise chemical reactions has been transformed into a simple "thermoplastic molding process" based on physical changes, resulting in a significant increase in production efficiency, a substantial reduction in energy consumption, simplified process control, and improved environmental friendliness. Through the innovative application of surface strengthening technology, the damage to material properties caused by traditional high-temperature and high-pressure conditions is avoided, while ensuring a strong bond between the functional layer and the substrate, significantly improving the material's durability.

[0024] In summary, this invention, through the systematic design of substrate components, composite material microstructure, and functionalization processes, solves the problems of insufficient mechanical properties, mutual constraints between freeze-thaw resistance and salt corrosion resistance, and long-term performance degradation in existing technologies, providing a novel solution for paving materials in cold and salt-corrosion environments. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] General Implementation Examples A polymer-modified EPDM safety brick resistant to freeze-thaw cycles and salt corrosion, comprising the following components by weight: 80-120 parts of pre-vulcanized EPDM rubber granules (20-80 mesh); 30-50 parts of polyolefin elastomer (POE); 3-8 parts compatibilizer 20-40 parts of modified red brick powder; Antioxidant (2,6-di-tert-butyl-4-methylphenol) 1-3 parts; Foaming agent (azodicarbonamide: sodium bicarbonate = 2~3:1) 3~5 parts; 1.5 to 3.5 parts of lubricant; 3 to 5 parts of tackifying resin (C5 or C9 petroleum resin).

[0027] A method for preparing a polymer-modified EPDM safety brick resistant to freeze-thaw cycles and salt corrosion includes the following steps: S1. Raw material pretreatment and surface modification Construction waste red bricks are initially crushed by a jaw crusher, then ground in a ball mill and passed through a 100-mesh sieve to obtain coarse red brick powder. The coarse red brick powder is then added to a 5%-10% hydrochloric acid solution (solid-liquid ratio 1:5) and stirred at 75℃ for 2-4 hours. After the reaction is complete, the mixture is allowed to settle, the supernatant is discarded, and the powder is repeatedly washed with deionized water until the filtrate is neutral (pH≈7). The acid-washed red brick powder is then transferred to an 8%-12% sodium hydroxide solution (solid-liquid ratio 1:5) and stirred at 80℃. Stir for 1-2 hours. After the reaction is complete, wash until neutral. Place the washed red brick powder in a 110℃ forced-air drying oven and dry to constant weight. Add the dried red brick powder, 6% by weight of polyacrylamide (PAM), and 4% by weight of hydroxypropyl distarch phosphate (HPDSP) into a high-speed mixer and stir at 1000-1500 rpm at 85℃ for 30-60 minutes. Pass the modified powder through a 250-mesh sieve to obtain the final modified red brick powder, and seal for later use.

[0028] Surface activation of pre-cured EPDM rubber granules is performed using either mild ozone treatment or plasma treatment. Specifically, the mild ozone treatment involves placing the pre-cured EPDM rubber granules in an ozone treatment device and introducing ozone at a concentration of 20–50 mg / m³. 3 The ozone-air mixture was prepared with a flow rate controlled between 0.5 and 1.5 m³ / s. 3 The plasma treatment process involves treating the particles at 20–30°C for 5–15 minutes, intermittently turning them to ensure uniformity. After treatment, the particles are ventilated for 10–20 minutes to allow residual ozone to decompose naturally. The specific steps of the plasma treatment are as follows: Pre-vulcanized EPDM rubber granules (20–80 mesh) are evenly spread on the vacuum chamber tray of the low-temperature plasma treatment equipment, with a thickness not exceeding 10 mm. The vacuum chamber is closed and evacuated to a pressure of 10–50 Pa. Then, a treatment gas is introduced into the vacuum chamber. The treatment gas can be air, oxygen, or argon, with a gas flow rate maintained at 20–50 sccm and a working pressure maintained at 50–100 Pa. The plasma generator is started, and the treatment is carried out at a power of 100–300 W for 30 seconds to 3 minutes.

[0029] S2, Low-temperature dry mixing Weigh the pre-cured EPDM rubber granules, polyolefin elastomer granules, and maleic anhydride-grafted EPDM as a compatibilizer, and put them into a high-speed mixer. Start the mixer and run it at 200-400 rpm for 2-4 minutes to achieve initial dispersion and mixing of polymer particles of different sizes and densities. During this stage, control the temperature of the mixer jacket or the material temperature to always be below 60℃. Without stopping the mixer, add the modified red brick powder, antioxidant, foaming agent, lubricant, and tackifying resin, and all other components to the initially uniformly mixed polymer mixture in sequence. Increase the mixer speed to 600-800 rpm and continue mixing for 5-8 minutes. After mixing is complete, discharge the uniform dry mixture from the outlet and transfer it to a sealed container for later use.

[0030] S3, Material spreading and hot-press foaming molding After cleaning the molding mold and applying an appropriate amount of release agent, place it in a hot press and preheat it to 160-180℃. Then, weigh the prepared dry mixture and spread it evenly in the preheated mold cavity, ensuring that the material layer is flat and without accumulation or gaps. Quickly complete the mold closing operation and immediately apply an initial pressure of 10-15MPa to the mold. Under the condition of maintaining the above pressure, use the preheating and continuous heating of the mold to stabilize the material temperature in the mold cavity within the set range of 160-180℃, and hold the pressure for 3-5 minutes.

[0031] S4, Cooling and Shaping After hot pressing and foaming, maintain the mold closed and keep the pressure at 5-10 MPa. At the same time, turn on the mold's cooling water circulation system to quickly and evenly cool the mold. By controlling the cooling water flow and temperature, the temperature of the mold cavity and the internal blank is quickly reduced from the hot pressing temperature to below 60°C. Once the mold temperature is confirmed to be stable below 60°C, the pressure inside the mold is slowly released to atmospheric pressure. Then, the mold is opened. Using a part removal tool or robot, the formed brick blank is carefully removed from the mold and placed on a turnover rack to cool naturally to room temperature.

[0032] S5, Surface Strengthening and Microtexturing Dissolve 3-5 parts of silane coupling agent (KH-570) and 2-3 parts of nano-silica (particle size 20nm) in 100 parts of 90% anhydrous ethanol by volume, and ultrasonically disperse for 30 minutes to prepare a surface treatment solution. Blow the surface of the vulcanized brick with compressed air to remove dust and debris. Use a spray gun to evenly spray the prepared surface treatment solution onto the upper and lower main working surfaces of the brick, ensuring the formation of a continuous, moist film. Transfer the sprayed brick to an oven at 100-120℃ and cure for 30-60 minutes. The density of the sprayed nano-SiO2 should be 2-5 g / m³. 2 During this process, ethanol evaporates, and the silane coupling agent undergoes a hydrolysis-condensation reaction, forming a strong -Si-O-Si- network structure with the hydroxyl groups on the brick surface and nano-SiO2 particles. This creates an ultra-wear-resistant and corrosion-resistant inorganic-organic hybrid protective layer on the brick surface. The cured brick is then fixed on the worktable of a laser marking machine. Using a 20W fiber laser, a 0.2mm deep, staggered diamond-shaped raised texture is engraved on the brick surface according to a preset program. This microstructure effectively disrupts the continuity of the water film, greatly improving the wet anti-slip performance of the brick surface.

[0033] Example 1 A polymer-modified EPDM safety brick resistant to freeze-thaw cycles and salt corrosion, comprising the following components by weight: Pre-cured EPDM rubber granules (40 mesh): 100 parts; Polyolefin elastomer: 40 parts; Maleic anhydride-grafted EPDM: 5 parts Modified red brick powder: 30 parts; 2,6-Di-tert-butyl-4-methylphenol: 2 parts; Foaming agent (azodicarbonamide: sodium bicarbonate = 2.5:1): 4 parts; Lubricant: 2.5 parts; Tackifying resin (C5 petroleum resin): 4 parts.

[0034] A method for preparing a polymer-modified EPDM safety brick resistant to freeze-thaw cycles and salt corrosion includes the following steps: S1. Raw material pretreatment and surface modification Construction waste red bricks were initially crushed by a jaw crusher, then ground in a ball mill and passed through a 100-mesh sieve to obtain coarse red brick powder. The coarse red brick powder was then added to a 7.5% hydrochloric acid solution (solid-liquid ratio 1:5) and stirred at 75°C for 3 hours. After the reaction was complete, the mixture was allowed to settle, the supernatant was discarded, and the powder was repeatedly washed with deionized water until the filtrate was neutral. The acid-washed red brick powder was then transferred to a 10% sodium hydroxide solution (solid-liquid ratio 1:5) and stirred at 80°C for 1 hour. After 0.5 hours of reaction, wash until neutral; place the washed red brick powder in a 110℃ forced-air drying oven and dry to constant weight; put the dried red brick powder, 6% by weight of polyacrylamide (PAM) and 4% by weight of hydroxypropyl distarch phosphate (HPDSP) into a high-speed mixer and stir at 1300 rpm and 85℃ for 45 minutes; pass the modified powder through a 250-mesh sieve to obtain the final modified red brick powder, and seal for later use.

[0035] The surface activation of pre-cured EPDM rubber granules was achieved through mild ozone treatment. The pre-cured EPDM rubber granules were placed in an ozone treatment device, and an ozone concentration of 35 mg / m³ was introduced. 3 The ozone-air mixture was controlled at a flow rate of 1 m³ / h. 3 / h, treat at 25℃ for 10 minutes, turning intermittently during treatment to ensure uniformity, and ventilate for 10-20 minutes after treatment to allow residual ozone to decompose naturally.

[0036] S2, Low-temperature dry mixing Weigh the pre-cured EPDM rubber granules, polyolefin elastomer granules, and maleic anhydride-grafted EPDM as a compatibilizer, and put them into a high-speed mixer. Start the mixer and run it at 300 rpm for 3 minutes to achieve initial dispersion and mixing of polymer particles of different sizes and densities. During this stage, control the temperature of the mixer jacket or the material temperature to always be below 60°C. Without stopping the mixer, add the modified red brick powder, antioxidant, foaming agent, lubricant, and tackifying resin, and all other components in sequence to the initially uniformly mixed polymer mixture. Increase the mixer speed to 700 rpm and continue mixing for 6 minutes. After mixing is complete, discharge the uniform dry mixture from the outlet and transfer it to a sealed container for later use.

[0037] S3, Material spreading and hot-press foaming molding After cleaning the molding mold and applying an appropriate amount of release agent, place it in a hot press and preheat it to 165°C. Then, weigh the prepared dry mixture and spread it evenly in the preheated mold cavity, ensuring that the material layer is flat and without accumulation or gaps. Quickly complete the mold closing operation and immediately apply an initial pressure of 12MPa to the mold. Under the condition of maintaining the above pressure, use the preheating of the mold and continuous heating to stabilize the material temperature in the mold cavity at 165°C for 4 minutes.

[0038] S4, Cooling and Shaping After hot pressing and foaming, the mold is kept closed and a pressure of 7.5 MPa is maintained. At the same time, the cooling water circulation system of the mold is turned on to quickly and evenly force-cool the mold. By controlling the flow rate and temperature of the cooling water, the temperature of the mold cavity and the internal blank is quickly reduced from the hot pressing temperature to below 50°C. Once the mold temperature is confirmed to be stable below 50°C, the pressure inside the mold is slowly released to atmospheric pressure. Then, the mold is opened. Using a part removal tool or a robot, the formed brick blank is carefully removed from the mold and placed on a turnover rack to cool naturally to room temperature.

[0039] S5, Surface Strengthening and Microtexturing Four parts of silane coupling agent (KH-570) and 2.5 parts of nano-silica (particle size 20nm) were dissolved in 100 parts of 90% anhydrous ethanol by volume, and ultrasonically dispersed for 30 minutes to prepare a surface treatment solution. The surface of the vulcanized brick was blown with compressed air to remove dust and debris. The prepared surface treatment solution was evenly sprayed onto the upper and lower main working surfaces of the brick using a spray gun, ensuring the formation of a continuous, moist film. The sprayed brick was then transferred to an oven at 110℃ and cured for 45 minutes, achieving a nano-SiO2 density of 3.5 g / m³. 2 During this process, ethanol evaporates, and the silane coupling agent undergoes a hydrolysis-condensation reaction, forming a strong -Si-O-Si- network structure with the hydroxyl groups on the brick surface and nano-SiO2 particles, thus constructing an ultra-wear-resistant and corrosion-resistant inorganic-organic hybrid protective layer on the brick surface. The cured brick is then fixed on the worktable of a laser marking machine, and a 20W fiber laser is used to carve a 0.2mm deep, staggered diamond-shaped raised texture on the brick surface according to a preset program, resulting in a polymer-modified EPDM safety brick that is resistant to freeze-thaw cycles and salt corrosion. Example 2

[0040] A polymer-modified EPDM safety brick resistant to freeze-thaw cycles and salt corrosion, comprising the following components by weight: Pre-cured EPDM rubber granules (60 mesh): 90 parts; Polyolefin elastomer: 45 parts; Maleic anhydride-grafted EPDM: 6 parts Modified red brick powder: 25 parts; 2,6-Di-tert-butyl-4-methylphenol: 1.5 parts; Foaming agent (azodicarbonamide: sodium bicarbonate = 2.5:1): 3.5 parts; Lubricant: 2 parts; Tackifying resin (C5 petroleum resin): 3.5 parts.

[0041] A method for preparing a polymer-modified EPDM safety brick resistant to freeze-thaw cycles and salt corrosion includes the following steps: S1. Raw material pretreatment and surface modification Construction waste red bricks were initially crushed by a jaw crusher, then ground in a ball mill and passed through a 100-mesh sieve to obtain coarse red brick powder. The coarse red brick powder was then added to a 7.5% hydrochloric acid solution (solid-liquid ratio 1:5) and stirred at 75°C for 3 hours. After the reaction was complete, the mixture was allowed to settle, the supernatant was discarded, and the powder was repeatedly washed with deionized water until the filtrate was neutral. The acid-washed red brick powder was then transferred to a 10% sodium hydroxide solution (solid-liquid ratio 1:5) and stirred at 80°C for 1 hour. After 0.5 hours of reaction, wash until neutral; place the washed red brick powder in a 110℃ forced-air drying oven and dry to constant weight; put the dried red brick powder, 6% by weight of polyacrylamide (PAM) and 4% by weight of hydroxypropyl distarch phosphate (HPDSP) into a high-speed mixer and stir at 1300 rpm and 85℃ for 45 minutes; pass the modified powder through a 250-mesh sieve to obtain the final modified red brick powder, and seal for later use.

[0042] The surface activation of pre-vulcanized EPDM rubber granules was performed using plasma treatment. The pre-vulcanized EPDM rubber granules were evenly spread on the vacuum chamber tray of the low-temperature plasma treatment equipment, with a thickness not exceeding 10 mm. The vacuum chamber was closed and evacuated to a pressure of 30 Pa. Then, a treatment gas, oxygen, was introduced into the vacuum chamber at a flow rate of 35 sccm and a working pressure of 75 Pa. The plasma generator was started, and the treatment was performed for 90 seconds at a power of 200 W.

[0043] S2, Low-temperature dry mixing Weigh the pre-cured EPDM rubber granules, polyolefin elastomer granules, and maleic anhydride-grafted EPDM as a compatibilizer, and put them into a high-speed mixer. Start the mixer and run it at 300 rpm for 3 minutes to achieve initial dispersion and mixing of polymer particles of different sizes and densities. During this stage, control the temperature of the mixer jacket or the material temperature to always be below 60°C. Without stopping the mixer, add the modified red brick powder, antioxidant, foaming agent, lubricant, and tackifying resin, and all other components in sequence to the initially uniformly mixed polymer mixture. Increase the mixer speed to 700 rpm and continue mixing for 7 minutes. After mixing is complete, discharge the uniform dry mixture from the outlet and transfer it to a sealed container for later use.

[0044] S3, Material spreading and hot-press foaming molding After cleaning the molding mold and applying an appropriate amount of release agent, place it in a hot press and preheat it to 170°C. Then, weigh the prepared dry mixture and spread it evenly in the preheated mold cavity, ensuring that the material layer is flat and without accumulation or gaps. Quickly complete the mold closing operation and immediately apply an initial pressure of 13MPa to the mold. Under the condition of maintaining the above pressure, use the preheating of the mold and continuous heating to stabilize the material temperature in the mold cavity at 170°C for 3.5 minutes.

[0045] S4, Cooling and Shaping After hot pressing and foaming, maintain the mold closed and keep the pressure at 7MPa. At the same time, turn on the mold's cooling water circulation system to quickly and evenly cool the mold. By controlling the cooling water flow and temperature, the temperature of the mold cavity and the internal blank is quickly reduced from the hot pressing temperature to below 60℃. Once the mold temperature is confirmed to be stable below 60℃, the pressure inside the mold is slowly released to normal pressure. Then, the mold is opened. Using a part removal tool or robot, the formed brick blank is carefully removed from the mold and placed on a turnover rack to cool naturally to room temperature.

[0046] S5, Surface Strengthening and Microtexturing Four parts of silane coupling agent (KH-570) and two parts of nano-silica (particle size 20nm) were dissolved in 100 parts of anhydrous ethanol (90% by volume) and ultrasonically dispersed for 30 minutes to prepare a surface treatment solution. The surface of the vulcanized brick was blown with compressed air to remove dust and debris. The prepared surface treatment solution was evenly sprayed onto the upper and lower main working surfaces of the brick using a spray gun, ensuring the formation of a continuous, moist film. The sprayed brick was then transferred to a 100℃ oven and cured for 30 minutes. The density of the sprayed nano-SiO2 was 2g / m³. 2During this process, ethanol evaporates, and the silane coupling agent undergoes a hydrolysis-condensation reaction, forming a strong -Si-O-Si- network structure with the hydroxyl groups on the brick surface and nano-SiO2 particles, thus constructing an ultra-wear-resistant and corrosion-resistant inorganic-organic hybrid protective layer on the brick surface. The cured brick is then fixed on the worktable of a laser marking machine, and a 20W fiber laser is used to carve a 0.2mm deep, staggered diamond-shaped raised texture on the brick surface according to a preset program, resulting in a polymer-modified EPDM safety brick that is resistant to freeze-thaw cycles and salt corrosion.

[0047] Example 3 A polymer-modified EPDM safety brick resistant to freeze-thaw cycles and salt corrosion, comprising the following components by weight: Pre-cured EPDM rubber granules (20 mesh): 110 parts; Polyolefin elastomer: 35 parts; Maleic anhydride-grafted EPDM: 7 parts Modified red brick powder: 35 parts; 2,6-Di-tert-butyl-4-methylphenol: 2.5 parts; Foaming agent (azodicarbonamide: sodium bicarbonate = 2.5:1): 4.5 parts; Lubricant: 3 parts; Tackifying resin (C9 petroleum resin): 5 parts.

[0048] A method for preparing a polymer-modified EPDM safety brick resistant to freeze-thaw cycles and salt corrosion includes the following steps: S1. Raw material pretreatment and surface modification Construction waste red bricks were initially crushed by a jaw crusher, then ground in a ball mill and passed through a 100-mesh sieve to obtain coarse red brick powder. The coarse red brick powder was then added to a 7.5% hydrochloric acid solution (solid-liquid ratio 1:5) and stirred at 75°C for 3 hours. After the reaction was complete, the mixture was allowed to settle, the supernatant was discarded, and the powder was repeatedly washed with deionized water until the filtrate was neutral. The acid-washed red brick powder was then transferred to a 10% sodium hydroxide solution (solid-liquid ratio 1:5) and stirred at 80°C for 1 hour. After 0.5 hours of reaction, wash until neutral; place the washed red brick powder in a 110℃ forced-air drying oven and dry to constant weight; put the dried red brick powder, 6% by weight of polyacrylamide (PAM) and 4% by weight of hydroxypropyl distarch phosphate (HPDSP) into a high-speed mixer and stir at 1300 rpm and 85℃ for 45 minutes; pass the modified powder through a 250-mesh sieve to obtain the final modified red brick powder, and seal for later use.

[0049] The surface activation of pre-cured EPDM rubber granules was achieved through mild ozone treatment. The pre-cured EPDM rubber granules were placed in an ozone treatment device, and an ozone-air mixture with an ozone concentration of 35 mg / m³ was introduced. The gas flow rate was controlled at 1 m³ / h, and the treatment was carried out at 25°C for 10 minutes. During the treatment, the granules were intermittently turned to ensure uniformity. After treatment, the granules were ventilated and left to stand for 10–20 minutes to allow the residual ozone to decompose naturally.

[0050] S2, Low-temperature dry mixing Weigh the pre-cured EPDM rubber granules, polyolefin elastomer granules, and maleic anhydride-grafted EPDM as a compatibilizer, and put them into a high-speed mixer. Start the mixer and run it at 400 rpm for 4 minutes to achieve initial dispersion and mixing of polymer particles of different sizes and densities. During this stage, control the temperature of the mixer jacket or the material temperature to always be below 60°C. Without stopping the mixer, add the modified red brick powder, antioxidant, foaming agent, lubricant, and tackifying resin, and all other components in sequence to the initially uniformly mixed polymer mixture. Increase the mixer speed to 800 rpm and continue mixing for 8 minutes. After mixing is complete, discharge the uniform dry mixture from the outlet and transfer it to a sealed container for later use.

[0051] S3, Material spreading and hot-press foaming molding After cleaning the molding mold and applying an appropriate amount of release agent, place it in a hot press and preheat it to 175°C. Then, weigh the prepared dry mixture and spread it evenly in the preheated mold cavity, ensuring that the material layer is flat and without accumulation or gaps. Quickly complete the mold closing operation and immediately apply an initial pressure of 14MPa to the mold. Under the condition of maintaining the above pressure, use the preheating of the mold and continuous heating to stabilize the material temperature in the mold cavity at 175°C for 4.5 minutes.

[0052] S4, Cooling and Shaping After hot pressing and foaming, maintain the mold closed and keep the pressure at 10MPa. At the same time, turn on the cooling water circulation system of the mold to quickly and evenly cool the mold. By controlling the flow rate and temperature of the cooling water, the temperature of the mold cavity and the internal blank is quickly reduced from the hot pressing temperature to below 60℃. When the mold temperature is confirmed to be stable below 60℃, the pressure inside the mold is slowly released to normal pressure. Then, the mold opening operation is carried out. Use a part removal tool or robot to carefully remove the formed brick blank from the mold and place it on a turnover rack to cool naturally to room temperature.

[0053] S5, Surface Strengthening and Microtexturing Four parts of silane coupling agent (KH-570) and 2.5 parts of nano-silica (particle size 20nm) were dissolved in 100 parts of anhydrous ethanol (90% by volume) and ultrasonically dispersed for 30 minutes to prepare a surface treatment solution. The surface of the vulcanized brick was blown with compressed air to remove dust and debris. The prepared surface treatment solution was evenly sprayed onto the upper and lower main working surfaces of the brick using a spray gun, ensuring the formation of a continuous, moist film. The sprayed brick was then transferred to a 120℃ oven and cured for 60 minutes, achieving a nano-SiO2 density of 5g / m³. 2. During this process, ethanol evaporates, and the silane coupling agent undergoes a hydrolysis-condensation reaction, forming a strong -Si-O-Si- network structure with the hydroxyl groups on the brick surface and nano-SiO2 particles, thus constructing an ultra-wear-resistant and corrosion-resistant inorganic-organic hybrid protective layer on the brick surface. The cured brick is then fixed on the worktable of a laser marking machine, and a 20W fiber laser is used to carve a 0.2mm deep, staggered diamond-shaped raised texture on the brick surface according to a preset program, resulting in a polymer-modified EPDM safety brick that is resistant to freeze-thaw cycles and salt corrosion.

[0054] Comparative Example 1 The difference from Example 1 is that unvulcanized EPDM raw rubber was used and a conventional vulcanization process was employed; Comparative Example 2 The difference from Example 1 is that the formulation does not contain maleic anhydride-grafted EPDM as a compatibilizer; Comparative Example 3 The difference from Example 1 is that the pre-vulcanized particles were not surface activated; Comparative Example 4 The difference from Example 1 is that the formulation does not contain POE as a binder; Comparative Example 5 The difference from Example 1 is that the modified red brick powder is 0 parts, and an equal amount (30 parts) of light calcium carbonate is used as filler; Comparative Example 6 The difference from Example 1 is that the foaming agent is only 4 parts azodicarbonamide and the sodium bicarbonate is 0 parts; Comparative Example 7 The difference from Example 1 is that the hot pressing temperature of S3 is set to 140°C; Comparative Example 8 The difference from Example 1 is that after hot pressing in S3, the brick blank is directly opened and taken out, omitting the pressure holding, cooling and shaping step in S4; Comparative Example 9 The difference from Example 1 is that step S5 is completely omitted.

[0055] Comparative Example 10 The difference from Example 1 is that there is no antioxidant.

[0056] The detection methods are shown in Table 1: Table 1 Detection Methods detection indicators Testing standards Tensile strength Refer to GB / T 528-2009 Determination of Tensile Stress-Strain Properties of Vulcanized Rubber or Thermoplastic Rubber Freeze-thaw resistance and salt corrosion resistance Referring to the single-sided freeze-thaw method (salt freezing method) in GB / T 50082-2009: After the specimen is immersed in 10% NaCl solution for 48 hours, it is subjected to rapid freeze-thaw cycles from -20℃ to 20℃. The retention rate (%) of dynamic elastic modulus after 50 cycles is recorded. The closer this value is to 100%, the better the freeze-thaw resistance and salt corrosion resistance. Compression permanent deformation GB / T 7759.1-2015: Deformation rate after testing at 70℃ for 24 hours abrasion resistance GB / T 9867-2008: Rotary roller abrasion test method for determining wear amount wet anti-slip coefficient GB / T 26542-2011: Determination of the average inclination angle using the slope method, and calculation of its tangent value as the anti-skid coefficient. Tensile strength change rate after hot air aging test GB / T 3512-2014: Accelerated aging and heat resistance tests of vulcanized rubber or thermoplastic rubber in hot air—Determination of the rate of change of tensile strength. Table 2 Performance data for examples and comparative examples sample Does the production process generate sulfide waste gas? Tensile strength (MPa) Salt freeze dynamic elastic modulus retention rate (%) Deformation rate (%) Wear amount (mm³) wet anti-slip coefficient Change rate of tensile strength (%) Example 1 none 12.5 95 28 85 0.78 -4.5 Example 2 none 13.1 93 26 81 0.76 -3.8 Example 3 none 11.8 96 30 89 0.79 -5.2 Comparative Example 1 have 8.2 75 45 145 0.72 -15 Comparative Example 2 none 9.5 82 38 120 0.74 -8 Comparative Example 3 none 10.3 85 35 110 0.75 -7 Comparative Example 4 none 7.1 70 33 180 0.7 -12.5 Comparative Example 5 none 10 78 32 105 0.65 -18 Comparative Example 6 none 11 88 40 95 0.77 -5 Comparative Example 7 none 9 80 50 130 0.73 -6.5 Comparative Example 8 none 11.8 65 29 100 0.77 -5.5 Comparative Example 9 none 12 92 30 165 0.55 -4.8 Comparative Example 10 none 11 90 28 90 0.77 -25 In the background, traditional paving materials such as ceramic tiles and concrete bricks generally face problems of poor freeze-thaw resistance and weak salt corrosion resistance. Although EPDM rubber has excellent weather resistance, it suffers from insufficient rigidity, poor resistance to compression set, and limited resistance to salt corrosion. This embodiment utilizes the bonding effect of POE, the compatibility effect of maleic anhydride-grafted EPDM, and the surface activation of pre-vulcanized particles to form a robust three-dimensional network structure, achieving high tensile strength. The modified red brick powder bonds well with the polymer matrix, reducing moisture penetration channels. The closed-cell structure formed by the composite foaming agent effectively resists frost heave stress, and the surface hybrid protective layer acts as a barrier, achieving excellent freeze-thaw resistance and salt corrosion resistance. Pre-vulcanized EPDM particles and POE jointly contribute to high resilience. The laser-engraved microtextures and nano-SiO2 reinforcement layer work together to achieve excellent wear resistance and anti-slip properties. Antioxidants and a stable cross-linked network structure effectively delay material aging.

[0057] Compared to Example 1, Comparative Example 1, using uncured EPDM and a traditional curing process, showed a comprehensive deterioration in all properties. Uncured rubber requires prolonged high-temperature curing, which is difficult to match with the foaming process, resulting in uneven internal structure, large bubbles, and poor mechanical properties. Comparative Example 2 lacked maleic anhydride-grafted EPDM, resulting in weak interfacial bonding and decreased tensile strength, freeze-thaw resistance, and abrasion resistance. Comparative Example 3's pre-cured EPDM particles were not activated, weakening the bonding between polymers and between polymers and fillers, leading to a general slight decrease in performance. Comparative Example 4 lacked PO. The E binder material lacks sufficient continuous phase bonding, resulting in a sharp decline in strength, elasticity, and durability. Comparative Example 5 uses lightweight calcium carbonate instead of modified red brick powder. The interfacial bonding ability between calcium carbonate and the polymer matrix is ​​far weaker than that of modified red brick powder, and it lacks the synergistic reinforcing effect between the modified red brick powder and the matrix. The material's internal structural support is insufficient, making it susceptible to damage during freeze-thaw cycles due to its porous structure. Its wear resistance and anti-aging properties also significantly decrease due to the failure of the reinforcing system. Comparative Example 6 uses only azodicarbonamide as a single foaming agent, which cannot achieve the same level of performance as azodicarbonamide. The dimethylformamide and sodium bicarbonate composite system achieves a uniform and dense distribution of cells. However, defects or uneven cell size in the cell structure lead to water accumulation and freezing at these defects during freeze-thaw cycles, generating expansion stress and resulting in a decrease in the dynamic elastic modulus retention rate. Wear resistance is also weakened due to the uneven surface cell structure. Comparative Example 7, with its excessively low hot-pressing temperature, resulted in insufficient melting and plasticization of POE and incomplete decomposition of the foaming agent, leading to poor material fusion, low strength, and reduced durability. Comparative Example 8, lacking pressure holding and cooling, exhibited high internal stress in the product, causing the cell structure to rebound or rupture under internal pressure, resulting in severe damage. Comparative Example 9 exhibits deformation and extremely poor freeze-thaw resistance. It completely omits surface strengthening and micro-texturing, losing the dense protective layer constructed from silane coupling agent and nano-silica. This makes the surface susceptible to salt corrosion and significantly reduces wear resistance. Furthermore, the lack of micro-texturing to disrupt the water film results in a significant decrease in the wet anti-slip coefficient. During freeze-thaw cycles, the surface is also prone to structural damage due to water absorption and freezing. Comparative Example 9, lacking antioxidants, exhibits extremely poor heat aging resistance and significant tensile strength loss, indicating that the material is highly degraded in a hot and oxygen-rich environment. Antioxidants are crucial for long-term durability.

Claims

1. A polymer-modified EPDM safety brick resistant to freeze-thaw cycles and salt corrosion, characterized in that, By weight, it includes the following components: 80-120 parts of 20-80 mesh pre-vulcanized EPDM rubber granules; 30-50 parts of polyolefin elastomer; 3-8 parts compatibilizer; 20-40 parts of modified red brick powder; Antioxidant 1-3 parts; 3-5 parts of foaming agent; 1.5 to 3.5 parts of lubricant; 3-5 parts of tackifying resin; The method for preparing the modified red brick powder includes: crushing waste red bricks, treating them sequentially with hydrochloric acid solution and sodium hydroxide solution, and then mixing them with polyacrylamide and hydroxypropyl distarch phosphate for surface modification, with the particle size controlled at 200-300 mesh. The polymer-modified EPDM safety brick has a nano-SiO2-silane coupling agent composite reinforcement layer on its surface, and the density of the nano-SiO2 is 2-5 g / m³. 2 .

2. The polymer-modified EPDM safety brick resistant to freeze-thaw cycles and salt corrosion according to claim 1, characterized in that, The compatibilizer is maleic anhydride-grafted EPDM.

3. The polymer-modified EPDM safety brick resistant to freeze-thaw cycles and salt corrosion according to claim 1, characterized in that, The foaming agent is a composite system of azodicarbonamide and sodium bicarbonate, with a mass ratio ranging from 2 to 3:

1.

4. The polymer-modified EPDM safety brick resistant to freeze-thaw cycles and salt corrosion according to claim 1, characterized in that, The antioxidant is 2,6-di-tert-butyl-4-methylphenol.

5. The polymer-modified EPDM safety brick resistant to freeze-thaw cycles and salt corrosion according to claim 1, characterized in that, The tackifying resin is C5 petroleum resin or C9 petroleum resin.

6. A method for preparing a polymer-modified EPDM safety brick resistant to freeze-thaw cycles and salt corrosion as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Raw material pretreatment and surface modification; S2, Low-temperature dry mixing; S3, Material spreading and hot-press foaming molding; S4, Cooling and Shaping; S5. Surface strengthening and micro-texturing: The surface of the brick is sprayed with a surface treatment liquid and cured, followed by laser micro-texturing to obtain polymer-modified EPDM safety bricks that are resistant to freeze-thaw cycles and salt corrosion.

7. The method for preparing the freeze-thaw resistant and salt-corrosion resistant polymer-modified EPDM safety brick according to claim 6, characterized in that, In step S2, the specific process of low-temperature dry mixing is as follows: pre-vulcanized EPDM rubber granules, polyolefin elastomer, and maleic anhydride-grafted EPDM are put into a high-speed mixer and mixed at 200-400 rpm for 2-4 minutes at a temperature below 60°C. Then, modified red brick powder, antioxidant, foaming agent, lubricant, tackifying resin, and all other components are added, and the speed is increased to 600-800 rpm, and mixing continues for 5-8 minutes.

8. The method for preparing the freeze-thaw resistant and salt-corrosion resistant polymer-modified EPDM safety brick according to claim 6, characterized in that, In step S3, the hot pressing conditions are: temperature 160-180℃, pressure 10-15MPa, and time 3-5min.

9. The method for preparing the freeze-thaw resistant and salt-corrosion resistant polymer-modified EPDM safety brick according to claim 6, characterized in that, In step S5, the surface treatment liquid is prepared by dissolving 3-5 parts of silane coupling agent and 2-3 parts of nano-silica in 100 parts of anhydrous ethanol with a volume ratio of 90%; the pattern depth of the microtexture processing is 0.1-0.3 mm.

10. The method for preparing the freeze-thaw resistant and salt-corrosion resistant polymer-modified EPDM safety brick according to claim 6, characterized in that, In step S5, the surface curing conditions are curing at 100-120℃ for 30-60 minutes.