Preparation of thermally stable hydrophobic modified fly ash and application thereof in high-temperature-resistant conveyor belt

Abstract

The application discloses a kind of preparation of thermally stable hydrophobic modified fly ash and its application in high-temperature-resistant conveying belt, belong to solid waste high-value utilization and polymer composite cross field, the present application adopts medium resistance barrier discharge plasma to activate fly ash and then introduces phenyl trimethoxysilane to carry out in-situ graft modification, and constructs stable Si-O-Si and benzene ring π-π stacking covalent network coating layer, to obtain reinforcing agent with excellent thermal stability and superhydrophobicity.The modified fly ash can partially replace traditional precipitated silica, and improve the mechanical properties and anti-aging performance of high-temperature-resistant conveying belt.

Description

Technical Field

[0001] This invention relates to the interdisciplinary field of polymer composite materials and high-value utilization of solid waste, specifically to a method for preparing thermally stable hydrophobic modified fly ash, and the application of this fly ash as a reinforcing agent in high-temperature resistant rubber conveyor belts. Background Technology

[0002] Under complex working conditions, conveyor belts often face high-temperature environments, which places stringent requirements on the mechanical strength, interfacial bonding force, and thermal aging stability of the rubber matrix. The temperature of materials conveyed in industries such as coking, cement, and metallurgy is often between 200-500℃, and sometimes even above 800℃. Coupled with severe wear, impact, and flexural forces, high-temperature resistant conveyor belts are required.

[0003] Currently, carbon black and precipitated silica (PS) are the most important reinforcing fillers in the rubber industry. However, the surface of PS is rich in polar silanol groups, which easily form hard agglomerates through hydrogen bonding, making it difficult to disperse in non-polar rubber matrices. This necessitates energy-intensive mechanical mixing and complex surface modification treatments. Furthermore, the production process of PS is complex, energy-intensive, and involves high carbon emissions, which is inconsistent with the current trend of green and low-carbon industrial development.

[0004] Fly ash (CFA), a major industrial solid waste generated by coal-fired power plants, is mainly composed of silicon and aluminum oxides and quartz microspheres, possessing potential reinforcing value. However, the surface of virgin fly ash is highly hydrophilic, resulting in extremely poor interfacial compatibility with non-polar rubber matrices. Direct filling not only fails to provide reinforcement but also creates stress concentration points, leading to a sharp decline in the mechanical properties of composite materials. Furthermore, existing conveyor belt formulations are prone to "debonding" at the filler-rubber interface under long-term thermo-oxidative aging, resulting in a shortened service life.

[0005] Therefore, developing a simple, low-cost modification method that can impart thermal stability and superhydrophobic properties to the surface of fly ash and applying it to high-temperature conveyor belt formulations is a pressing technical challenge that needs to be addressed. Summary of the Invention

[0006] To address the shortcomings mentioned in the background art, the present invention aims to provide a method for preparing thermally stable hydrophobic modified fly ash and its application in high-temperature conveyor belts. By modifying the fly ash, the thermal stability, superhydrophobicity, interfacial compatibility and dispersibility, mechanical properties, and resistance to thermo-oxidative aging of the fly ash coating layer and composite material are improved.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] A method for preparing thermally stabilized hydrophobic modified fly ash, characterized by comprising the following steps:

[0009] S1. Dry the fly ash at 100-110℃ to constant weight to obtain dried fly ash;

[0010] S2. Place the dry fly ash in a dielectric barrier discharge reactor, introduce a mixed gas composed of argon and oxygen, and treat it with plasma at a power of 50-300W for 2-30 minutes to obtain plasma-activated fly ash.

[0011] S3. Dissolve phenyltrimethoxysilane in a mixed solvent consisting of acetone and deionized water, add acetic acid dropwise to adjust the pH to 3.0-5.0, stir at room temperature for 0.5-2 hours to obtain a hydrolysate;

[0012] S4. Add plasma-activated fly ash and hydrolysate to the reactor and stir the mixture in a constant temperature water bath at 60-90℃ for 30-120 minutes. After centrifugation and washing with deionized water, the mixture is dried in an oven at 80-120℃ until constant weight to obtain thermally stable hydrophobic modified fly ash.

[0013] More preferably, the fly ash in step S1 has a median particle size of 1-30 μm and a loss on ignition of less than 9%.

[0014] More preferably, the volume ratio of argon to oxygen in the mixed gas in step S2 is 1-4:1, and the gas flow rate is 50-150 mL / min.

[0015] More preferably, the amount of phenyltrimethoxysilane used in step S3 is 1-10% of the amount of dried fly ash used in step S2.

[0016] More preferably, in step S3, the volume ratio of acetone to water in the mixed solvent is 1:4-6.

[0017] More preferably, in step S4, the solid-liquid ratio of plasma-activated fly ash to hydrolysate is 1:5-20 g / mL.

[0018] The above-mentioned application of thermally stabilized hydrophobic modified fly ash in high-temperature conveyor belts, wherein the thermally stabilized hydrophobic modified fly ash is used as a reinforcing filler to prepare high-temperature conveyor belt rubber composite materials.

[0019] More preferably, a high-temperature resistant conveyor belt rubber composite material comprises the following raw materials in parts by weight:

[0020] Natural rubber 80-120 parts, synthetic rubber 5-20 parts, heat-stabilized hydrophobic modified fly ash 10-30 parts, carbon black 20-40 parts, zinc oxide 3-5 parts, stearic acid 1-3 parts, antioxidant 1-3 parts, softener 5-15 parts, sulfur 1.5-2.5 parts, accelerator 0.5-1.5 parts, precipitated silica 0-15 parts.

[0021] More preferably, the synthetic rubber is butadiene rubber or styrene-butadiene rubber, the carbon black is at least one of carbon black N330, carbon black N220, carbon black N234, carbon black N550 or carbon black N660, the antioxidant is at least one of antioxidant RD and antioxidant 4010NA, the softener is at least one of aromatic oil, naphthenic oil and paraffin oil, and the accelerator is at least one of accelerator CZ, accelerator NS and accelerator DZ.

[0022] More preferably, a method for preparing a high-temperature resistant conveyor belt rubber composite material includes the following steps:

[0023] After plasticizing natural rubber and synthetic rubber in an internal mixer, heat-stabilized hydrophobic modified fly ash, precipitated silica, carbon black, zinc oxide, stearic acid, antioxidant, and softener are added. The mixture is then mixed at 80-120℃ for 3-8 minutes. After discharge and cooling, the mixture is transferred to an open mill, where sulfur and accelerator are added. The mixture is then passed through a thin mill and formed into triangular swirls 6-10 times. Finally, it is vulcanized on a flat vulcanizing machine at 140-160℃ for 15-25 minutes and then pressed into shape to obtain a high-temperature resistant conveyor belt rubber composite material.

[0024] The beneficial effects of this invention are:

[0025] This invention utilizes dielectric barrier discharge plasma activation to generate numerous dangling bonds and active hydroxyl groups on the surface of fly ash. These hydroxyl groups can induce a condensation reaction between the hydrolysate of phenyltrimethoxysilane and the fly ash during subsequent grafting modification, constructing a large number of stable Si-O-Si covalent networks. This forms a dense and robust organic-inorganic hybrid coating layer on the fly ash surface, with numerous adjacent benzene ring structures forming π-π stacking interactions, significantly improving the thermal stability of the coating layer.

[0026] The phenyl organic segments introduced in this invention significantly reduce the surface energy of the filler, making it superhydrophobic and greatly improving its wettability and interfacial compatibility with nonpolar rubber matrices. The modified fly ash is uniformly dispersed in the rubber matrix, effectively transferring stress through physical entanglement and chemical bonding. Case studies show that, after partially replacing silica, the tensile strength and tear strength of the composite material are superior to those of traditional silica / carbon black reinforcing systems.

[0027] Based on the grafting process of plasma treatment, this invention forms a "benzene ring-SiOx" organic-inorganic hybrid coating layer on the surface of fly ash, which gives the modified fly ash extremely high thermal stability and effectively blocks the diffusion of oxygen and heat into the rubber matrix. This allows the composite material to maintain extremely high interfacial bonding strength even after high-temperature aging. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 These are schematic flowcharts of Embodiments 1-9 and Comparative Examples 1-3 of the present invention;

[0030] Figure 2 These are the X-ray diffraction patterns of thermally stable hydrophobic modified fly ash from Examples 1-3 and Comparative Example 1 of the present invention;

[0031] Figure 3 These are comparison images of the microstructure of thermally stabilized hydrophobic modified fly ash and original fly ash in Examples 1-3 of the present invention, where (a) is the original fly ash, (b) is 1P / CFA in Example 1, (c) is 2P / CFA in Example 2, and (d) is 4P / CFA in Example 3.

[0032] Figure 4 This is a comparison of the Fourier transform infrared spectra of thermally stable hydrophobic modified fly ash and phenyltrimethoxysilane in Examples 1-3 of the present invention and Comparative Example 1.

[0033] Figure 5 These are the thermogravimetric curves of thermally stable hydrophobic modified fly ash from Examples 1-3 of this invention and Comparative Example 1;

[0034] Figure 6 This is a comparison chart of the hydrophobicity changes of thermally stabilized hydrophobic modified fly ash in Examples 1-6 of the present invention at different calcination temperatures;

[0035] Figure 7 This is a comparison chart of the tensile strength and elongation at break of the rubber composite materials of Examples 7-9, Comparative Examples 2 and 3 of the present invention;

[0036] Figure 8 These are comparison diagrams of the bonding strength of steel wire ropes before and after aging of the rubber composite materials in Examples 7-9, Comparative Examples 2 and 3 of the present invention;

[0037] Figure 9This is a comparison diagram of the bonding strength of the rubber composite material of Embodiments 8 and 9 of the present invention at different aging temperatures for steel wire rope. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0040] Example 1 Figure 1 As shown, a method for preparing thermally stabilized hydrophobic modified fly ash includes the following steps:

[0041] S1. Fly ash with a median particle size of 4.97 μm and a loss on ignition of 5.8% was dried at 105 °C to constant weight to obtain dried fly ash.

[0042] S2. Place 10g of dry fly ash in a dielectric barrier discharge reactor, introduce a mixed gas of argon and oxygen in a volume ratio of 3:1 at a flow rate of 100 mL / min, and treat with plasma at 60W power for 5min to obtain plasma-activated fly ash.

[0043] S3. Dissolve 0.1g of phenyltrimethoxysilane in a mixed solvent consisting of 25mL acetone and 120mL deionized water, add acetic acid dropwise to adjust the pH to 4.0, stir at room temperature for 1h to obtain the hydrolysate;

[0044] S4. Take 10g of plasma-activated fly ash and 100mL of hydrolysate and add them to the reactor. Stir and react in an 80℃ constant temperature water bath for 60min. After centrifugation and washing with deionized water, the mixture is dried in an oven at 120℃ until constant weight to obtain thermally stable hydrophobic modified fly ash, labeled as 1P / CFA.

[0045] Example 2 Figure 1 As shown, a method for preparing thermally stabilized hydrophobic modified fly ash includes the following steps:

[0046] S1. Fly ash with a median particle size of 4.97 μm and a loss on ignition of 5.8% was dried at 105 °C to constant weight to obtain dried fly ash.

[0047] S2. Place 10g of dry fly ash in a dielectric barrier discharge reactor, introduce a mixed gas of argon and oxygen in a volume ratio of 3:1 at a flow rate of 100 mL / min, and treat with plasma at 60W power for 5min to obtain plasma-activated fly ash.

[0048] S3. Dissolve 0.2g of phenyltrimethoxysilane in a mixed solvent consisting of 25mL acetone and 120mL deionized water, add acetic acid dropwise to adjust the pH to 4.0, stir at room temperature for 1h to obtain the hydrolysate;

[0049] S4. Take 10g of plasma-activated fly ash and 100mL of hydrolysate and add them to the reactor. Stir the mixture in an 80℃ constant temperature water bath for 60min. After centrifugation and washing with deionized water, place the mixture in an oven at 120℃ and dry it to constant weight to obtain thermally stable hydrophobic modified fly ash, labeled as 2P / CFA.

[0050] Example 3 Figure 1 As shown, a method for preparing thermally stabilized hydrophobic modified fly ash includes the following steps:

[0051] S1. Fly ash with a median particle size of 4.97 μm and a loss on ignition of 5.8% was dried at 105 °C to constant weight to obtain dried fly ash.

[0052] S2. Place 10g of dry fly ash in a dielectric barrier discharge reactor, introduce a mixed gas of argon and oxygen in a volume ratio of 3:1 at a flow rate of 100 mL / min, and treat with plasma at 60W power for 5min to obtain plasma-activated fly ash.

[0053] S3. Dissolve 0.4g of phenyltrimethoxysilane in a mixed solvent consisting of 25mL acetone and 120mL deionized water, add acetic acid dropwise to adjust the pH to 4.0, stir at room temperature for 1h to obtain the hydrolysate;

[0054] S4. Take 10g of plasma-activated fly ash and 100mL of hydrolysate and add them to the reactor. Stir and react in an 80℃ constant temperature water bath for 60min. After centrifugation and washing with deionized water, the mixture is dried in an oven at 120℃ until constant weight to obtain thermally stable hydrophobic modified fly ash, labeled as 4P / CFA.

[0055] Example 4 Figure 1 As shown, a method for preparing thermally stabilized hydrophobic modified fly ash includes the following steps:

[0056] S1. Fly ash with a median particle size of 4.97 μm and a loss on ignition of 5.8% was dried at 105 °C to constant weight to obtain dried fly ash.

[0057] S2. Place 10g of dry fly ash in a dielectric barrier discharge reactor, introduce a mixed gas of argon and oxygen in a volume ratio of 3:1 at a flow rate of 100 mL / min, and treat with plasma at 60W power for 5min to obtain plasma-activated fly ash.

[0058] S3. Dissolve 0.6g of phenyltrimethoxysilane in a mixed solvent consisting of 25mL acetone and 120mL deionized water, add acetic acid dropwise to adjust the pH to 4.0, stir at room temperature for 1h to obtain the hydrolysate;

[0059] S4. Take 10g of plasma-activated fly ash and 100mL of hydrolysate and add them to the reactor. Stir the mixture in an 80℃ constant temperature water bath for 60min. After centrifugation and washing with deionized water, place the mixture in an oven at 120℃ and dry it to constant weight to obtain thermally stable hydrophobic modified fly ash, labeled as 6P / CFA.

[0060] Example 5 Figure 1 As shown, a method for preparing thermally stabilized hydrophobic modified fly ash includes the following steps:

[0061] S1. Fly ash with a median particle size of 4.97 μm and a loss on ignition of 5.8% was dried at 105 °C to constant weight to obtain dried fly ash.

[0062] S2. Place 10g of dry fly ash in a dielectric barrier discharge reactor, introduce a mixed gas of argon and oxygen in a volume ratio of 3:1 at a flow rate of 100 mL / min, and treat with plasma at 60W power for 5min to obtain plasma-activated fly ash.

[0063] S3. Dissolve 0.8g of phenyltrimethoxysilane in a mixed solvent consisting of 25mL acetone and 120mL deionized water, add acetic acid dropwise to adjust the pH to 4.0, stir at room temperature for 1h to obtain the hydrolysate;

[0064] S4. Take 10g of plasma-activated fly ash and 100mL of hydrolysate and add them to the reactor. Stir and react in a constant temperature water bath at 80℃ for 60min. After centrifugation and washing with deionized water, the mixture is dried in an oven at 120℃ until constant weight to obtain thermally stable hydrophobic modified fly ash, labeled as 8P / CFA.

[0065] Example 6 Figure 1As shown, a method for preparing thermally stabilized hydrophobic modified fly ash includes the following steps:

[0066] S1. Fly ash with a median particle size of 4.97 μm and a loss on ignition of 5.8% was dried at 105 °C to constant weight to obtain dried fly ash.

[0067] S2. Place 10g of dry fly ash in a dielectric barrier discharge reactor, introduce a mixed gas of argon and oxygen in a volume ratio of 3:1 at a flow rate of 100 mL / min, and treat with plasma at 60W power for 5min to obtain plasma-activated fly ash.

[0068] S3. Dissolve 1.0 g of phenyltrimethoxysilane in a mixed solvent consisting of 25 mL of acetone and 120 mL of deionized water, add acetic acid dropwise to adjust the pH to 4.0, stir at room temperature for 1 h to obtain the hydrolysate;

[0069] S4. Take 10g of plasma-activated fly ash and 100mL of hydrolysate and add them to the reactor. Stir the mixture in an 80℃ constant temperature water bath for 60min. After centrifugation and washing with deionized water, place the mixture in an oven at 120℃ and dry it to constant weight to obtain thermally stable hydrophobic modified fly ash, labeled as 10P / CFA.

[0070] Example 7 Figure 1 As shown, a high-temperature resistant conveyor belt rubber composite material comprises the following raw materials in parts by weight:

[0071] Natural rubber 90 parts, styrene-butadiene rubber 10 parts, precipitated silica 10 parts, heat-stabilized hydrophobic modified fly ash 15 parts, carbon black N330 25 parts, zinc oxide 4 parts, stearic acid 2 parts, antioxidant RD 1 part, antioxidant 4010NA 1 part, aromatic oil 8 parts, sulfur 2.5 parts, accelerator CZ 1.2 parts;

[0072] The preparation method of the above-mentioned high-temperature resistant conveyor belt rubber composite material includes the following steps:

[0073] After plasticizing 90g of natural rubber and 10g of styrene-butadiene rubber in a mixer, 10g of precipitated silica, 15g of heat-stabilized hydrophobic modified fly ash, 25g of carbon black N330, 4g of zinc oxide, 2g of stearic acid, 1g of antioxidant RD, 1g of antioxidant 4010NA and 8g of aromatic oil were added. The mixture was mixed at 100℃ for 5 minutes, discharged and cooled, and then transferred to an open mill. At the same time, 2.5g of sulfur and 1.2g of accelerator CZ were added. The mixture was then passed through a thin mill and formed into triangular slurries 8 times. Finally, it was vulcanized at 150℃ for 20 minutes on a flat vulcanizing machine and then pressed to obtain a high-temperature resistant conveyor belt rubber composite material. Test pieces with a thickness of 2mm and pull-out test samples with a 3.7mm diameter steel wire rope were made and marked as 1P / CFA-NR.

[0074] The preparation method of the above-mentioned thermally stable hydrophobic modified fly ash is the same as that in Example 1.

[0075] Example 8 Figure 1 As shown, a high-temperature resistant conveyor belt rubber composite material comprises the following raw materials in parts by weight:

[0076] Natural rubber 90 parts, styrene-butadiene rubber 10 parts, precipitated silica 10 parts, heat-stabilized hydrophobic modified fly ash 15 parts, carbon black N330 25 parts, zinc oxide 4 parts, stearic acid 2 parts, antioxidant RD 1 part, antioxidant 4010NA 1 part, aromatic oil 8 parts, sulfur 2.5 parts, accelerator CZ 1.2 parts, labeled as 2P / CFA-NR.

[0077] The preparation method of the above-mentioned thermally stable hydrophobic modified fly ash is the same as that in Example 2, and the preparation method of the high-temperature resistant conveyor belt rubber composite material is the same as that in Example 7.

[0078] Example 9 Figure 1 As shown, a high-temperature resistant conveyor belt rubber composite material comprises the following raw materials in parts by weight:

[0079] Natural rubber 90 parts, styrene-butadiene rubber 10 parts, precipitated silica 10 parts, heat-stabilized hydrophobic modified fly ash 15 parts, carbon black N330 25 parts, zinc oxide 4 parts, stearic acid 2 parts, antioxidant RD 1 part, antioxidant 4010NA 1 part, aromatic oil 8 parts, sulfur 2.5 parts, accelerator CZ 1.2 parts, labeled as 4P / CFA-NR.

[0080] The preparation method of the above-mentioned thermally stable hydrophobic modified fly ash is the same as that in Example 3, and the preparation method of the high-temperature resistant conveyor belt rubber composite material is the same as that in Example 7.

[0081] Comparative Example 1 Figure 1 As shown, a method for preparing fly ash includes the following steps:

[0082] S1. Fly ash with a median particle size of 4.97 μm and a loss on ignition of 5.8% was dried at 105 °C to constant weight to obtain dried fly ash.

[0083] S2. Place 10g of dry fly ash in a dielectric barrier discharge reactor, introduce a mixed gas of argon and oxygen in a volume ratio of 3:1 at a flow rate of 100 mL / min, and treat with plasma at 60W power for 5min to obtain plasma-activated fly ash.

[0084] S3. Mix 25 mL of acetone and 120 mL of deionized water, add acetic acid to adjust the pH to 4.0, stir at room temperature for 1 h to obtain a blank mixed solvent;

[0085] S4. Take 10g of plasma-activated fly ash and 100mL of blank mixed solvent and add them to the reactor. Stir the mixture in an 80℃ constant temperature water bath for 60min. After centrifugation and washing with deionized water, place the mixture in an oven at 120℃ and dry it to constant weight to obtain ungrafted silane fly ash, labeled as CFA.

[0086] The difference between this comparative example and Example 1 is that the fly ash is not loaded with phenyltrimethoxysilane, while the rest of the preparation process is the same as in Example 1.

[0087] Comparative Example 2 Figure 1 As shown, a high-temperature resistant conveyor belt rubber composite material comprises the following raw materials in parts by weight:

[0088] Natural rubber 90 parts, styrene-butadiene rubber 10 parts, precipitated silica 25 parts, carbon black N330 25 parts, zinc oxide 4 parts, stearic acid 2 parts, antioxidant RD 1 part, antioxidant 4010NA 1 part, aromatic oil 8 parts, sulfur 2.5 parts, accelerator CZ 1.2 parts;

[0089] The preparation method of the above-mentioned high-temperature resistant conveyor belt rubber composite material includes the following steps:

[0090] After plasticizing 90g of natural rubber and 10g of styrene-butadiene rubber in a mixer, 25g of precipitated silica, 25g of carbon black N330, 4g of zinc oxide, 2g of stearic acid, 1g of antioxidant RD, 1g of antioxidant 4010NA and 8g of aromatic oil were added. The mixture was then mixed at 100℃ for 5 minutes. After degassing and cooling, the mixture was transferred to an open mill, and 2.5g of sulfur and 1.2g of accelerator CZ were added. The mixture was then pulverized in a triangular pattern 8 times. Finally, it was vulcanized at 150℃ for 20 minutes on a flat vulcanizing machine and then pressed into shape to obtain a high-temperature resistant conveyor belt rubber composite material. Test pieces with a thickness of 2mm and pull-out samples with a 3.7mm diameter steel wire rope were made and marked as PS-NR.

[0091] The difference between this comparative example and Example 7 is that the thermally stabilized hydrophobic modified fly ash is replaced with precipitated silica, while the rest of the preparation process is the same as in Example 7.

[0092] Comparative Example 3 Figure 1 As shown, a high-temperature resistant conveyor belt rubber composite material comprises the following raw materials in parts by weight:

[0093] 90 parts natural rubber, 10 parts styrene-butadiene rubber, 25 parts ungrafted silane fly ash, 25 parts carbon black N330, 4 parts zinc oxide, 2 parts stearic acid, 1 part antioxidant RD, 1 part antioxidant 4010NA, 8 parts aromatic oil, 2.5 parts sulfur, 1.2 parts accelerator CZ;

[0094] The preparation method of the above-mentioned high-temperature resistant conveyor belt rubber composite material includes the following steps:

[0095] After plasticizing 90g of natural rubber and 10g of styrene-butadiene rubber in a mixer, 25g of ungrafted silane fly ash, 25g of carbon black N330, 4g of zinc oxide, 2g of stearic acid, 1g of antioxidant RD, 1g of antioxidant 4010NA and 8g of aromatic oil were added. The mixture was then mixed at 100℃ for 5 minutes. After degassing and cooling, the mixture was transferred to an open mill, and 2.5g of sulfur and 1.2g of accelerator CZ were added. The mixture was then pulverized in a triangular pattern 8 times. Finally, it was vulcanized at 150℃ for 20 minutes on a flat vulcanizing machine and then pressed into shape to obtain a high-temperature resistant conveyor belt rubber composite material. Test pieces with a thickness of 2mm and pull-out samples with a 3.7mm diameter steel wire rope were made and marked as CFA-NR.

[0096] The difference between this comparative example and Example 7 is that the thermally stable hydrophobic modified fly ash is replaced with ungrafted silane fly ash. The preparation process of the ungrafted silane fly ash is the same as that of Comparative Example 1, and the rest of the preparation process is the same as that of Example 7.

[0097] Performance testing

[0098] Structural characterization: The fly ash from Examples 1-3 and Comparative Example 1 was characterized structurally. X-ray diffraction was used to analyze the crystal structure of each group of fly ash. Scanning electron microscopy was used to observe the microstructure and elemental distribution of the fly ash from Examples 1-3 and the original fly ash. Fourier transform infrared spectroscopy was used to analyze the surface functional groups of the fly ash from Examples 1-3 and Comparative Example 1. The structural characterization results are as follows: Figure 2 , Figure 3 and Figure 4 As shown.

[0099] Depend on Figure 2 The X-ray diffraction pattern showed that the modified fly ash still maintained the original quartz and hematite crystal phase structure, and no impurity peaks were observed. However, as the loading of phenyltrimethoxysilane increased, the intensity of the characteristic diffraction peaks gradually decreased, and weak diffuse peaks appeared in the range of 20°-30°, proving that the amorphous organosilicon network was successfully coated on the surface of the fly ash.

[0100] Depend on Figure 3 The microstructure comparison images show that after grafting with phenyltrimethoxysilane (b, c, d), the surface of fly ash becomes rough and covered with a uniform organosilane network coating layer. This is beneficial to increasing its mechanical interlocking force with the rubber matrix. The morphology of different samples and EDS-mapping show that as the loading of phenyltrimethoxysilane increases, the surface silicon and aluminum content gradually decreases, while the carbon content gradually increases. This is because with the coverage of the benzene rings on the surface, the exposed SiAl elements on the surface are reduced, and the carbon-containing coating layer is more dense.

[0101] Figure 4 In the Fourier transform infrared spectrum, 3450 cm⁻¹ -1 The broad peak at 2840 cm⁻¹ corresponds to the stretching vibration of -OH groups on the fly ash surface. The hydroxyl peak is strongest in the plasma-treated fly ash sample, and its intensity decreases significantly with increasing phenyltrimethoxysilane loading. -1 and 2942 cm -1 A weak characteristic absorption peak attributable to the phenyl CH bond in phenyltrimethoxysilane was observed, indicating that after hydrolysis, phenyltrimethoxysilane underwent a condensation reaction with the active hydroxyl groups on the surface of fly ash, forming a chemical bond.

[0102] Thermal stability test: The thermal stability of the fly ash from Examples 1-3 and Comparative Example 1 was tested using a thermogravimetric analyzer in air at a heating rate of 10°C / min, with a temperature range of 30-800°C. The results are as follows: Figure 5 As shown.

[0103] Depend on Figure 5 It can be seen that as the loading of phenyltrimethoxysilane increases, the thermal decomposition temperature of the material shifts towards higher temperatures, proving that the dense organic coating layer it forms has good resistance to high-temperature decomposition. Modified fly ash, as a reinforcing agent, can improve the high-temperature stability of rubber composites.

[0104] Hydrophobicity test: The hydrophobicity of fly ash from Examples 1-6 at different calcination temperatures was determined using the activation degree method. The hydrophobicity test results are as follows: Figure 6 As shown.

[0105] Depend on Figure 6 It can be seen that when the loading of phenyltrimethoxysilane is greater than or equal to 4%, the modified fly ash can still maintain high hydrophobicity below 325℃, indicating that the coating layer has excellent thermal stability. As the loading increases further, the thermal stability only increases slightly, which is because the surface grafting sites have been exhausted, indicating that its optimal loading is 4%.

[0106] Mechanical property testing: The rubber composites of Examples 7-9, Comparative Examples 2 and 3 of this invention were subjected to mechanical property testing. The tensile strength and elongation at break of each group of rubber composites were tested according to GB / T 528-2009. The mechanical property test results are as follows: Figure 7 As shown.

[0107] Depend on Figure 7It can be seen that the tensile strength and elongation at break of 1P / CFA-NR, 2P / CFA-NR and 4P / CFA-NR with modified fly ash in Examples 7-9 are better than those of PS-NR and CFA-NR in Comparative Examples 2 and 3. This shows that the modified fly ash of the present invention exhibits excellent reinforcing effect.

[0108] Aging performance testing: Referring to GB / T 5755-2021, the steel wire rope bonding strength of the rubber composites in Examples 7-9, Comparative Examples 2 and 3 before and after aging at 145±5℃ for 168 hours was tested. The steel wire rope bonding strength of the rubber composites in Examples 8 and 9 was also tested at different aging temperatures (140-230℃) for 168 hours. The aging performance test results are as follows: Figure 8 and Figure 9 As shown.

[0109] Depend on Figure 8 It can be seen that with the increase of phenyltrimethoxysilane loading, the anti-aging ability of the material is significantly improved. The bonding strength of 1P / CFA-NR, 2P / CFA-NR and 4P / CFA-NR with modified fly ash in Examples 7-9 is better than that of PS-NR and CFA-NR in Comparative Examples 2 and 3, indicating that the bonding interface between the wire rope and the colloid is more stable after filling with the modified fly ash of the present invention.

[0110] Depend on Figure 9 It can be seen that as the heat aging temperature increases, the steel wire rope core sample filled with 2P / CFA in Example 8 can withstand a maximum of 180℃, while the sample filled with 4P / CFA in Example 9 can withstand a maximum of 215℃, showing a significant improvement in high temperature resistance. Both groups of samples reached the T4 level (heat-resistant conveyor belts are classified according to their heat resistance level: they are divided into 4 levels according to different test temperatures: T1 can withstand a test temperature of no more than 100℃; T2 can withstand a test temperature of no more than 125℃; T3 can withstand a test temperature of no more than 150℃; T4 can withstand a test temperature of no more than 175℃).

[0111] In summary, this invention, through plasma-induced grafting, can transform industrial solid waste fly ash into a rubber reinforcing filler with strong thermal stability and hydrophobicity. This not only solves the problem of high-value utilization of fly ash, but also endows rubber conveyor belts with excellent mechanical strength and high-temperature resistance and anti-aging properties, and has good prospects for industrial application.

[0112] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A method for preparing thermally stabilized hydrophobic modified fly ash, characterized in that, Includes the following steps: S1. Dry the fly ash at 100-110℃ to constant weight to obtain dried fly ash; S2. Place the dry fly ash in a dielectric barrier discharge reactor, introduce a mixed gas composed of argon and oxygen, and treat it with plasma at a power of 50-300W for 2-30 minutes to obtain plasma-activated fly ash. S3. Dissolve phenyltrimethoxysilane in a mixed solvent consisting of acetone and deionized water, add acetic acid dropwise to adjust the pH to 3.0-5.0, stir at room temperature for 0.5-2 hours to obtain a hydrolysate; S4. Add plasma-activated fly ash and hydrolysate to the reactor and stir the mixture in a constant temperature water bath at 60-90℃ for 30-120 minutes. After centrifugation and washing with deionized water, the mixture is dried in an oven at 80-120℃ until constant weight to obtain thermally stable hydrophobic modified fly ash.

2. The method for preparing thermally stabilized hydrophobic modified fly ash according to claim 1, characterized in that, The fly ash in step S1 has a median particle size of 1-30 μm and a loss on ignition of less than 9%.

3. The method for preparing thermally stabilized hydrophobic modified fly ash according to claim 1, characterized in that, In step S2, the volume ratio of argon to oxygen in the mixed gas is 1-4:1, and the gas flow rate is 50-150 mL / min.

4. The method for preparing thermally stabilized hydrophobic modified fly ash according to claim 1, characterized in that, In step S3, the amount of phenyltrimethoxysilane used is 1-10% of the amount of dried fly ash used in step S2, and the volume ratio of acetone to water in the mixed solvent is 1:4-6.

5. The method for preparing thermally stabilized hydrophobic modified fly ash according to claim 1, characterized in that, In step S4, the solid-liquid ratio of plasma-activated fly ash to hydrolysate is 1:5-20 g / mL.

6. A thermally stabilized hydrophobic modified fly ash, characterized in that, It is prepared by the preparation method described in any one of claims 1-5.

7. The application of the thermally stabilized hydrophobic modified fly ash according to claim 6 in high-temperature conveyor belts, characterized in that, The thermally stable hydrophobic modified fly ash is used as a reinforcing filler to prepare high-temperature resistant conveyor belt rubber composite materials.

8. The application of the thermally stabilized hydrophobic modified fly ash according to claim 7 in high-temperature conveyor belts, characterized in that, A high-temperature resistant conveyor belt rubber composite material, comprising the following raw materials in parts by weight: Natural rubber 80-120 parts, synthetic rubber 5-20 parts, heat-stabilized hydrophobic modified fly ash 10-30 parts, carbon black 20-40 parts, zinc oxide 3-5 parts, stearic acid 1-3 parts, antioxidant 1-3 parts, softener 5-15 parts, sulfur 1.5-2.5 parts, accelerator 0.5-1.5 parts, precipitated silica 0-15 parts.

9. The application of the thermally stabilized hydrophobic modified fly ash according to claim 7 in high-temperature conveyor belts, characterized in that, The synthetic rubber is butadiene rubber or styrene-butadiene rubber, the carbon black is at least one of carbon black N330, carbon black N220, carbon black N234, carbon black N550 or carbon black N660, the antioxidant is at least one of antioxidant RD and antioxidant 4010NA, the softener is at least one of aromatic oil, naphthenic oil and paraffin oil, and the accelerator is at least one of accelerator CZ, accelerator NS and accelerator DZ.

10. The application of the thermally stabilized hydrophobic modified fly ash according to claim 7 in high-temperature conveyor belts, characterized in that, A method for preparing a high-temperature resistant conveyor belt rubber composite material includes the following steps: After plasticizing natural rubber and synthetic rubber raw rubber in an internal mixer, heat-stabilized hydrophobic modified fly ash, precipitated silica, carbon black, zinc oxide, stearic acid, antioxidant and softener are added. The mixture is then mixed at 80-120℃ for 3-8 minutes. After discharge and cooling, the mixture is transferred to an open mill, where sulfur and accelerator are added. The mixture is then passed through a thin mill and formed into triangular swirls 6-10 times. Finally, it is vulcanized on a flat vulcanizing machine at 140-160℃ for 15-25 minutes and then pressed into shape to obtain a high-temperature resistant conveyor belt rubber composite material.

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