Electrically conductive modified asphalt, method for its production and use

Abstract

The application provides a conductive modified asphalt and a preparation method and application thereof, which comprises the following components in parts by weight: 100-200 parts of base asphalt, 10-30 parts of dihydric alcohol, 5-25 parts of diisocyanate, 1-3 parts of chain extender and 5-10 parts of conductive filler; the conductive filler contains a polar functional group. The conductive modified asphalt is prepared by a method of in-situ polymerization of polyurethane and synchronous compounding of the polar conductive filler, which not only enhances the interfacial bonding force between the polyurethane and the asphalt, effectively improves the modulus and other mechanical properties of the modified asphalt, and improves the anti-rutting capacity, but also promotes the conductive filler to form a percolation network in the modified asphalt, improves the conductivity of the asphalt, and reduces the conductive percolation value. The conductive modified asphalt has good road performance and conductivity, and can be used for the construction of conductive road surfaces, and has a good application prospect in the fields of road surface self-sensing, self-detection, heating and deicing.

Description

Technical Field

[0001] This invention belongs to the field of road engineering material preparation technology, specifically relating to a conductive modified asphalt, its preparation method, and its application. Background Technology

[0002] Since the beginning of the 21st century, the development of smart mobility has placed new demands on road infrastructure. Smart highways, as a revolutionary product of the deep integration of next-generation information technology and transportation systems, are transforming human travel and have become a strategic high ground that countries are vying for. Conductive asphalt concrete, as the most typical self-sensing pavement material, can not only monitor traffic data and road performance in real time, improving road utilization and maintainability; it can also be heated to melt ice and snow, improving the road's anti-icing performance and increasing road safety; furthermore, it can participate in high-tech fields such as autonomous driving and intelligent vehicle technology integration, as well as energy harvesting. Therefore, the development of conductive asphalt technology has become a key core for promoting the construction of smart pavements. Thus, the research and development of conductive asphalt with stable conductivity is of great significance.

[0003] Ordinary asphalt concrete pavement has high resistivity and is a poor conductor of electricity. It is necessary to add conductive media such as graphite and carbon black to improve its conductivity. When the content of conductive media exceeds a certain critical value (percolation threshold), it can be linked into chains in the matrix. Electrons move through the chains to make the material conductive, and percolation transformation from insulator to conductor occurs. At present, research on conductive asphalt concrete usually takes the mixture of asphalt and aggregate as the research object. The conductive filler is directly incorporated into the insulating mixture. The rigid filler is mainly dispersed in the matrix asphalt phase, which serves as both a conductive medium and a road modifier for the matrix asphalt. This seemingly "two-in-one" material design may have the following main problems: (1) High percolation threshold. The surface chemical activity of the unmodified conductive filler is low. The conductive network is built only by the adsorption of the filler surface itself, which leads to a relatively high percolation threshold, resulting in unstable conductivity and high cost; (2) It leads to asphalt brittleness. In asphalt concrete, carbon-based fillers form a network structure. When added in large quantities, they can improve the strength of asphalt as an inorganic rigid material. However, when added in large quantities, the asphalt may become brittle, accelerating the formation of microcracks. This not only accelerates the deterioration of the asphalt's road performance, but the generation of a large number of cracks may also cut off the conductive path.

[0004] To address these issues, researchers have attempted to combine conductive fillers of different shapes to promote the formation of conductive networks. For example, graphite powder and steel fiber modified asphalt concrete. Graphite forms clusters through short-range contact, while the high aspect ratio of steel fibers constructs conductive pathways through long-range bridging and short-range loop effects. However, the lubricating effect of graphite weakens the adhesion of the asphalt, reducing the strength and durability of the asphalt concrete, leading to a severe deterioration in its road performance. When the particle size of graphite powder is less than 0.075 mm, it can partially function as a mineral filler, affecting the aggregate gradation and volumetric properties of the asphalt concrete. The difficulty in dispersing steel fibers during asphalt concrete preparation limits their incorporation amount, preventing the achievement of the required conductivity. For example, invention patent CN117024978A discloses a mesoporous carbon modified conductive asphalt and its preparation method. Although the method takes the asphalt phase as the research object, a large amount of water needs to be added during the preparation process to dilute the coupling agent and enhance the interfacial force between the conductive filler and the asphalt. However, a large amount of water is introduced during the preparation process, and the water is evaporated by mixing at a high temperature of 145-165°C, resulting in a high preparation temperature. In addition, if all the water cannot be effectively removed, it may lead to the deterioration of the mechanical properties of the asphalt. Moreover, compared with the comparative example, the conductivity of the embodiment only decreases by one order of magnitude, and the improvement effect on conductivity is not ideal. Summary of the Invention

[0005] To address the aforementioned problems in the existing technology, this invention provides a conductive modified asphalt mortar and its preparation method, solving the problems of unstable conductivity and brittle asphalt formation and accelerated microcrack formation caused by large amounts of carbon-based fillers in existing conductive asphalt.

[0006] To achieve the above objectives, the present invention adopts the following scheme: a conductive asphalt, comprising the following components in parts by weight: 100-200 parts of base asphalt, 10-30 parts of diol, 5-25 parts of diisocyanate, 1-3 parts of chain extender and 5-10 parts of conductive filler; wherein the conductive filler contains polar functional groups, and the conductive filler is divided into conductive filler 1 and conductive filler 2.

[0007] Preferably, the diol is polyethylene glycol, polytetrahydrofuran ether glycol, or polypropylene glycol; the diisocyanate is diphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, or dicyclohexylmethane diisocyanate; the chain extender is 4,4'-methylenebis(2-chloroaniline), 1,4-butanediol, or ethylene glycol; and the conductive filler 1 and conductive filler 2 can be independently selected from single-walled carbon nanotubes or multi-walled carbon nanotubes.

[0008] Another object of the present invention is to provide a method for preparing the above-mentioned conductive modified asphalt, comprising the following steps:

[0009] 1) Under an inert atmosphere, the diol and diisocyanate are stirred evenly and then subjected to a polymerization reaction to obtain a prepolymer.

[0010] 2) Add conductive filler 1 to the prepolymer obtained in step 1) and react for 10-20 min. Then add chain extender and mix for 30-60 s to obtain composite modifier.

[0011] 3) Heat the base asphalt to 100-130℃ to soften it, then add conductive filler 2 and stir evenly. Then add the composite modifier obtained in step 2) and let it react fully. Heat and solidify to obtain the conductive modified asphalt.

[0012] In this way, the numerous functional groups (including hydroxyl, carboxyl, and amino groups) contained in the polar conductive filler can chemically react with the isocyanate groups in the prepolymer (polyurethane) to obtain a composite modifier with high stability. The composite modifier is then blended with the base asphalt via in-situ polymerization. Unreacted diisocyanates further react with the polar functional groups in the base asphalt, allowing the composite modifier to be uniformly dispersed in the asphalt. Furthermore, due to the extremely high stability of the composite modifier, the polar conductive filler can be uniformly adsorbed onto the polyurethane in the modified asphalt, forming a conductive network structure within the asphalt and enhancing the conductivity of the modified asphalt.

[0013] Preferably, the inert atmosphere is nitrogen or argon.

[0014] Preferably, the polymerization reaction in step 1) is carried out at a temperature of 50–60°C for 10–30 min.

[0015] Preferably, the reaction temperature in step 2) is 50–60°C.

[0016] Preferably, in step 3), the mass ratio of the base asphalt to the composite modifier is 10:1 to 5; and the mass ratio of the conductive filler 1 to the conductive filler 2 is 1:2 to 10.

[0017] Preferably, the heating and curing temperature in step 3) is 50-100°C, and the curing time is 2-12 hours.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. This invention prepares conductive modified asphalt through a method of simultaneous compounding of polyurethane in situ polymerization and polar conductive fillers. First, the polar conductive filler participates in the in-situ polymerization of polyurethane monomers to obtain a conductive composite prepolymer. Then, this prepolymer is simultaneously compounded with the base asphalt, allowing unreacted diisocyanate to further react chemically with the polar functional groups in the base asphalt. Therefore, this invention forms a stable cross-linked network structure through the interaction between asphalt, polyurethane, and the polar conductive filler. On the one hand, this enhances the interfacial bonding force between polyurethane and asphalt, effectively improving the modulus and other mechanical properties of the modified asphalt, and improving rutting resistance and high-temperature performance. On the other hand, it promotes the formation of a percolation network in the modified asphalt by the conductive filler, increasing the conductivity of the asphalt and reducing the conductive percolation value. The conductive asphalt of this invention possesses both good road performance and conductivity, and can be used for the construction of conductive pavements, especially showing promising applications in pavement self-sensing, self-detection, and heating de-icing fields.

[0020] 2. This invention improves the compatibility of its components through synergistic effects, enabling the conductive filler to cross-link into a stable percolation network structure. This effectively reduces the percolation threshold of the conductive filler, and without adding water or dispersants, the amount of conductive filler incorporated is small. This solves the problems of unstable conductivity and asphalt brittleness caused by high carbon-based material content in existing conductive asphalt. The raw materials for this invention are widely available, the preparation process is simple, the production process has low energy consumption and reduces carbon emissions, making it easy for large-scale industrial production. It also provides a theoretical basis and technical support for promoting smart highways. Attached Figure Description

[0021] Figure 1 The graph shows the relationship between the complex modulus |G*|-frequency of different conductive modified asphalts prepared in this invention at 60℃.

[0022] Figure 2 The phase angle δ-frequency relationship of different conductive modified asphalts prepared in this invention at 60℃ is shown in the figure.

[0023] Figure 3 Infrared spectra of different conductive modified asphalts prepared according to the present invention.

[0024] Figure 4 The images show the microstructures of different conductive modified asphalts prepared according to this invention under an optical microscope.

[0025] Figure 5 Microstructure diagrams of different conductive modified asphalts prepared in this invention at 80℃ and 180℃. Detailed Implementation

[0026] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0027] I. A method for preparing conductive modified asphalt.

[0028] Example 1

[0029] A conductive modified asphalt is prepared by the following method:

[0030] (1) Under a nitrogen atmosphere, 30g of polyethylene glycol was poured into a four-necked flask and stirred at 200rpm for 15min. Then, 24g of diphenylmethane diisocyanate was added and stirred evenly. The polymerization reaction was carried out at a constant temperature of 50℃ for 10min to obtain the prepolymer.

[0031] (2) Add 0.38g of carbon nanotubes to the prepolymer obtained in step (1) and react for 5min. Then add 2.7g of 4,4'-methylenebis(2-chloroaniline) and mix evenly. After reacting for 30s, 57.08g of composite modifier is obtained.

[0032] (3) Place 50g of 70# base asphalt in an oil bath and heat it to 120°C to soften it. Stir continuously at a rate of 500rpm to make the base asphalt flow. Then add 2.5g of carbon nanotubes and stir for 5min. Then add 12.5g of the composite modifier obtained in step 2). Stir and react for 5min and then stop the reaction. Pour it into a polytetrafluoroethylene pan and place it in an 80°C vacuum oven to cure for 2h to obtain the conductive modified asphalt.

[0033] Example 2

[0034] A conductive modified asphalt is prepared by the following method:

[0035] (1) Under a nitrogen atmosphere, 30g of polyethylene glycol was poured into a four-necked flask and stirred at 200rpm for 15min. Then, 24g of diphenylmethane diisocyanate was added and stirred evenly. The polymerization reaction was carried out at a constant temperature of 50℃ for 10min to obtain the prepolymer.

[0036] (2) Add 0.76g of carbon nanotubes to the prepolymer obtained in step (1) and react for 5min. Then add 2.7g of 4,4'-methylenebis(2-chloroaniline) and mix evenly. After reacting for 30s, 57.46g of composite modifier is obtained.

[0037] (3) Place 50g of 70# base asphalt in an oil bath and heat it to 120°C to soften it. Stir continuously at a rate of 500rpm to make the base asphalt flow. Then add 2.5g of carbon nanotubes and stir for 5min. Then add 12.5g of the composite modifier obtained in step 2). Stir and react for 5min and then stop the reaction. Pour it into a polytetrafluoroethylene pan and place it in an 80°C vacuum oven to cure for 2h to obtain the conductive modified asphalt.

[0038] Comparative Example 1

[0039] No carbon nanotubes were added to the base asphalt or the composite modifier; the other steps were the same as in Example 1.

[0040] Comparative Example 2

[0041] Carbon nanotubes were not added to the composite modifier, and the other steps were the same as in Example 1.

[0042] II. Performance Testing

[0043] 1. The conductive modified asphalts prepared in Examples 1-2 and Comparative Examples 1-2 were subjected to rheological property testing using a dynamic shear rheometer (DSR). The temperature was maintained at 60°C, which is generally considered the highest temperature for asphalt pavements. The strain was fixed at 1%. Dynamic frequency scanning was used, with a frequency scanning range of 100-0.01Hz, scanning from high frequency to low frequency to determine the high-temperature rheological properties of the modified asphalt. The storage modulus G' reflects the asphalt material's resistance to elastic deformation, and the composite modulus |G*| reflects the asphalt material's resistance to rutting. The larger the |G*| value, the better the resistance to rutting. The phase angle δ reflects the viscoelasticity of the material, with a value between 0 and 90°. When δ = 0°, the material exhibits pure elasticity, and when δ = 90°, the material exhibits pure viscosity. For asphalt under high-temperature conditions, an excessively high δ value will lead to a sticky pavement and a decrease in rutting resistance. The lower the δ value, the better the elasticity, that is, the greater the deformation recovery ability, and the better the rutting resistance.

[0044] The complex modulus |G*| of different conductive modified asphalts varies with frequency as follows: Figure 1 As shown in the figure, compared with Comparative Example 1 and Comparative Example 2, the complex modulus |G*| of the modified asphalt after the addition of carbon nanotubes in this invention is improved, and the complex modulus |G*| also increases with the increase of carbon nanotube content, thus improving the rutting resistance of the modified asphalt. This is because this invention adopts a two-step method, firstly adding carbon nanotubes to the base asphalt and polyurethane prepolymer respectively, so that the polar conductive filler first forms a certain cross-linked network structure in the base asphalt and polyurethane prepolymer respectively, and then performing melt blending to further form a more stable percolation network, so that the modified asphalt exhibits better resistance to rutting.

[0045] The phase angle δ of different modified asphalts varies with frequency as follows: Figure 2 As shown in the figure, compared with Comparative Example 1 and Comparative Example 2, the rutting resistance of the modified asphalt after the addition of carbon nanotubes in this invention is significantly improved, and the rutting resistance of the modified asphalt gradually increases with the increase of carbon nanotube content.

[0046] 2. The conductive modified asphalt prepared in Examples 1-2 and Comparative Examples 1-2 were characterized for their characteristic functional groups using Fourier transform infrared spectroscopy (FTIR) in the wavenumber range of 400–4000 cm⁻¹. -1 The resolution is 4cm. -1 The result is as follows Figure 3 As shown.

[0047] As can be seen from the figure, at 1723cm -1 The absorption peak at 3328 cm⁻¹ is mainly due to the carbonyl vibration of the urethane group, indicating that the polyurethane-modified asphalt in the comparative and examples was successfully synthesized. -1 The absorption peak at [insert value here] is a hydroxyl vibration peak. No obvious hydroxyl vibration peak appeared in Comparative Example 1, while a weak hydroxyl vibration peak appeared in Comparative Example 2. Further investigation revealed that a significant hydroxyl vibration peak appeared in Example 1, indicating that the composite modifier contains a large amount of hydroxyl groups. This absorption peak is even more pronounced in Example 2, which is related to the further increase in the carbon nanotube content in the polyurethane. Infrared results confirm the presence of hydroxyl groups in the carbon nanotubes, leading to a strong interfacial force between the conductive filler and the polyurethane in the examples.

[0048] 3. The microstructure of the conductive modified asphalt film samples prepared in Comparative Examples 1-2 and Examples 1-2 was observed using an optical microscope in transmittance mode. The results are as follows: Figure 4 As shown.

[0049] As can be seen from the figures, Comparative Example 1 shows a uniform matrix without any network structure. When carbon nanotubes are directly added to the matrix asphalt (Comparative Example 2), the black carbon nanotubes exhibit independent, dispersed island phases and cannot form conductive network pathways. However, in Example 1, by adding a small amount of carbon nanotubes (0.4% of the matrix asphalt mass) during the polyurethane synthesis process, a large number of carbon nanotubes can be clearly observed, and they connect with each other to form a continuous network structure. Furthermore, increasing the amount of carbon nanotubes added during polyurethane synthesis (Example 2) results in a denser and more uniform conductive network pathway formed by the carbon nanotubes.

[0050] 4. To verify the high-temperature resistance of the material prepared according to this invention, the conductive modified asphalt prepared in Examples 1 and 2 was heated to 80°C and 180°C respectively, and its microstructure was observed under an optical microscope. The results are as follows: Figure 5 As shown.

[0051] As can be seen from the figure, the internal microstructure of the conductive modified asphalt prepared in this invention did not change significantly at 80℃ and 180℃. This indicates that the network structure of the conductive modified asphalt of this invention remained almost unchanged with increasing temperature, demonstrating that the conductive modified asphalt of this invention exhibits high-temperature stability.

[0052] 5. To verify the conductivity of the conductive modified asphalt prepared by the present invention, the conductive modified asphalt prepared in Examples 1-2 and Comparative Examples 1-2 were tested using a high resistance meter to form discs. The results are shown in Table 1.

[0053] Table 1

[0054]

[0055] As can be seen from Table 1, when no CNT conductive material is added to the asphalt (Comparative Example 1), its resistivity is on the order of 10. 12 However, simply adding a large amount of carbon nanotubes to the polyurethane prepolymer (Comparative Example 2) did not result in a significant decrease in resistance and resistivity; the order of magnitude remained unchanged. Furthermore, when carbon nanotubes formed a network structure of conductive pathways within the asphalt (Example 1), the resistivity of the conductive modified asphalt increased from the original 10... 12 dropped to 10 8 Further increasing the carbon nanotube content in asphalt (Example 2) has little effect on resistance and resistivity.

[0056] In summary, the conductive modified asphalt prepared by this invention not only improves its conductivity but also enhances its rutting resistance and high-temperature stability, thus meeting the requirements for the use of existing conductive asphalt.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the applicant has described the present invention in detail with reference to preferred embodiments, those skilled in the art should understand that any modifications or equivalent substitutions to the technical solutions of the present invention that do not depart from the spirit and scope of the technical solutions of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing conductive modified asphalt, characterized in that, The conductive modified asphalt comprises the following components in parts by weight: 100-200 parts of base asphalt, 10-30 parts of diol, 5-25 parts of diisocyanate, 1-3 parts of chain extender, and 5-10 parts of conductive filler; the conductive filler contains polar functional groups, and the conductive filler is divided into conductive filler 1 and conductive filler 2; the conductive filler 1 and conductive filler 2 can be independently selected from single-walled carbon nanotubes or multi-walled carbon nanotubes; The conductive modified asphalt is obtained through the following steps: 1) Under an inert atmosphere, the diol and diisocyanate are stirred evenly and then subjected to a polymerization reaction to obtain a prepolymer; 2) Add conductive filler 1 to the prepolymer obtained in step 1) and react for 10-20 min. Then add chain extender and mix and react for 30-60 s to obtain composite modifier. 3) Heat the base asphalt to 100~130℃ to soften it, then add conductive filler 2 and stir evenly. Then add the composite modifier obtained in step 2) and let it react fully. Heat and solidify to obtain the conductive modified asphalt.

2. The method for preparing conductive modified asphalt according to claim 1, characterized in that, The diol is polyethylene glycol, polytetrahydrofuran ether glycol, or polypropylene glycol; the diisocyanate is diphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, or dicyclohexylmethane diisocyanate; and the chain extender is 4,4'-methylenebis(2-chloroaniline), 1,4-butanediol, or ethylene glycol.

3. The method for preparing conductive modified asphalt according to claim 1, characterized in that, The inert atmosphere is nitrogen or argon.

4. The method for preparing conductive modified asphalt according to claim 1, characterized in that, The polymerization reaction in step 1) is carried out at a temperature of 50-60°C for 10-30 minutes.

5. The method for preparing conductive modified asphalt according to claim 1, characterized in that, The reaction temperature in step 2) is 50~60℃.

6. The method for preparing conductive modified asphalt according to claim 1, characterized in that, In step 3), the mass ratio of the base asphalt to the composite modifier is 10: (1~5); the mass ratio of the conductive filler 1 to the conductive filler 2 is 1: (2~10).

7. The method for preparing conductive modified asphalt according to claim 1, characterized in that, The heating and curing temperature in step 3) is 50~100℃, and the heating and curing time is 2~12h.

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