A method for evaluating the adsorption characteristics and reaction mechanism of rubber particles in rubber modified asphalt

Abstract

The application discloses a method for evaluating the adsorption characteristics and reaction mechanism of rubber particles in rubber modified asphalt, which comprises the following steps: 1) preparing rubber modified asphalt; 2) separating the rubber particles in the rubber modified asphalt from the asphalt liquid phase; 3) determining the adsorption preference of the rubber particles to the molecular weight of the asphalt according to a gel permeation chromatogram and determining the adsorption preference of the rubber particles to the functional groups in the asphalt according to a Fourier transform infrared spectrum; and 4) determining the composition change of the rubber particles before and after reaction with the asphalt according to thermogravimetric analysis data. The application can obtain the adsorption characteristics of the rubber particles in the rubber modified asphalt and the mutual reaction mechanism between the rubber particles and the asphalt, and is helpful for the formula optimization and mixing condition design of the rubber modified asphalt.

Description

Technical Field

[0001] This invention relates to the field of modified asphalt technology, and more specifically to a method for evaluating the adsorption characteristics and reaction mechanism of rubber particles in rubber-modified asphalt. Background Technology

[0002] Currently, approximately 1.4 billion waste tires are generated globally each year, and this annual generation continues to grow at a rate of 6% to 8% annually. Therefore, the disposal and treatment of waste tires has become an urgent problem. One common method to transform waste tires into usable materials is to grind them into rubber granules and use them as modifiers in asphalt paving materials. However, the adsorption characteristics and reaction mechanisms of rubber granules in asphalt are not yet fully understood, which significantly limits their application in asphalt.

[0003] Therefore, developing a method to evaluate the adsorption characteristics and reaction mechanism of rubber particles in rubber-modified asphalt is of great significance. Summary of the Invention

[0004] The purpose of this invention is to provide a method for evaluating the adsorption characteristics and reaction mechanism of rubber particles in rubber-modified asphalt.

[0005] The technical solution adopted in this invention is:

[0006] A method for evaluating the adsorption characteristics and reaction mechanism of rubber particles in rubber-modified asphalt includes the following steps:

[0007] 1) Disperse rubber particles in asphalt to obtain rubber-modified asphalt;

[0008] 2) Separate the rubber particles and the asphalt liquid phase in rubber-modified asphalt;

[0009] 3) The rubber particles separated in step 2) are soaked in tetrahydrofuran multiple times. The leachate obtained from each soaking and the asphalt separated in step 2) are then tested by gel permeation chromatography and Fourier transform infrared spectroscopy. The adsorption preference of rubber particles for the molecular weight of asphalt is determined based on the gel permeation chromatogram, and the adsorption preference of rubber particles for functional groups in asphalt is determined based on the Fourier transform infrared spectroscopy.

[0010] 4) Take the rubber granules from step 1) and the rubber granules from step 3) after the final soaking and perform thermogravimetric analysis.

[0011] Then, the compositional changes of the rubber particles before and after the reaction with asphalt were determined based on thermogravimetric analysis data.

[0012] Preferably, the mass ratio of rubber particles to asphalt in step 1) is 0.15 to 0.25:1.

[0013] Preferably, the rubber granules in step 1) are made from waste tires.

[0014] Preferably, the rubber-modified asphalt in step 1) is one of warm-mix asphalt and hot-mix asphalt.

[0015] Preferably, step 2) is performed as follows: the rubber-modified asphalt is poured onto a sieve in a sealed container and then allowed to stand, thus separating the rubber particles and the asphalt liquid phase.

[0016] Preferably, the mesh size of the sieve is 70μm to 80μm.

[0017] Preferably, the settling process is carried out at 160℃~170℃ for 50min~70min.

[0018] Preferably, the ratio of rubber particles to tetrahydrofuran in step 3) is 1g:5mL to 10mL.

[0019] Preferably, the soaking time in step 3) is 3 min to 5 min.

[0020] Preferably, the soaking in step 3) is performed 4 to 5 times.

[0021] The beneficial effects of this invention are as follows: This invention extracts the components in the interaction region between asphalt and rubber particles through a layer-by-layer separation method, and then determines the molecular weight distribution of asphalt adsorbed by rubber particles and the absorption preference of asphalt functional groups by gel permeation chromatography and Fourier transform infrared spectroscopy. Furthermore, thermogravimetric analysis is performed on the original rubber particles and the rubber particles after reacting with asphalt to determine the changes in the composition of the rubber particles before and after the reaction. This allows us to understand the adsorption characteristics of rubber particles in rubber-modified asphalt and the mutual reaction mechanism between rubber particles and asphalt, which is helpful for optimizing the formulation and designing the mixing conditions of rubber-modified asphalt. Attached Figure Description

[0022] Figure 1 The flowchart for step 3) in the embodiment is shown.

[0023] Figure 2 The images show gel permeation chromatograms of the asphalt liquid phase and leachate in the examples.

[0024] Figure 3 The image shows the Fourier transform infrared spectra of the asphalt liquid phase and leachate in the examples.

[0025] Figure 4 The images show the TG and DSC curves of the original rubber particles and the tetrahydrofuran-soaked rubber particles in the examples. Detailed Implementation

[0026] The present invention will be further explained and described below with reference to specific embodiments.

[0027] Example:

[0028] A method for evaluating the adsorption characteristics and reaction mechanism of rubber particles in rubber-modified asphalt, comprising the following steps:

[0029] 1) Rubber granules (made from waste tires and can pass through a 40-mesh sieve) and hot-mix asphalt with a permeability grade of 60 / 70 are mixed at a mass ratio of 0.2:1, and then sheared at a high speed of 6000 rpm at 176℃ for 60 min, and then allowed to stand to swell and develop for 30 min to obtain rubber-modified asphalt.

[0030] 2) Pour the rubber-modified asphalt onto a 200-mesh sieve in a sealed container, and let it stand at 165°C for 60 minutes to separate the rubber particles and the asphalt liquid phase.

[0031] 3) Wrap 12g of the rubber particles separated in step 2) with a 200-mesh sieve, and then immerse them sequentially into four beakers containing 60mL of tetrahydrofuran, each for 3 minutes, to obtain leachate (named beaker 1, beaker 2, beaker 3, and beaker 4 in the order of immersion; the operation flowchart is shown below). Figure 1 (as shown);

[0032] 4) The asphalt liquid phase separated in step 2) and the leachate obtained from each soaking in step 3) were tested using an Agilent HPLC 1260 gel permeation chromatography system (the asphalt liquid phase was first dissolved in tetrahydrofuran before testing, at a ratio of 1 mg asphalt liquid phase: 1 mL tetrahydrofuran, while the leachate was extracted with tetrahydrofuran, so it could be tested directly; all samples needed to be filtered through a 0.2 μm filter before injection). Tetrahydrofuran was used as the mobile phase, equipped with PLgel 3 μm Mixed-E and PLgel 5 μm gels. Two chromatographic columns were used, with the temperature of both columns set to 30℃, the flow rate set to 1 mL / min, and the injection volume set to 20 μL (only pitch molecules with diameters smaller than the pore size can enter the gel channels; among the pitch molecules that enter the channels, larger pitch molecules can pass through the gaps between gel particles and exit the column first. Therefore, the order in which pitch molecules exit the column is from largest to smallest). The concentration of the expelled molecules was recorded as a chromatogram using a refractive index differential detector. The resulting gel permeation chromatogram is shown below. Figure 2 As shown, by Figure 2It can be seen that: compared with the leachate from cups 1 to 4, the asphalt liquid phase has a higher curve in the range of 10 min to 14 min, but a lower peak at 15.7 min. This indicates that mixing rubber particles with the original asphalt will result in a higher content of macromolecules in the asphalt. However, the rubber particles do not uniformly absorb the components in the asphalt. On the contrary, during the reaction between the rubber particles and the asphalt, there is a certain absorption preference for components of different molecular sizes, and they tend to absorb components with smaller molecular sizes.

[0033] 5) Take 30 mL of the asphalt liquid phase separated in step 2) and the leachate obtained from each soaking in step 3) and place them in a 70°C water bath until the liquid becomes solid. Then place them in a vacuum oven at 80°C for 8 hours (to completely remove THF and water). Finally, use a Bruker VERTEX 70FTIR spectrometer to measure the Fourier transform infrared spectrum with a resolution of 4 cm⁻¹. -1 The scan was performed 16 times, and the scanning range was 4000cm. -1 ~400cm -1 The sample was evenly spread onto a potassium bromide (KBr) plate, which was then placed in the sample chamber to initiate spectral scanning. Simultaneously, the Fourier transform infrared spectrum of the asphalt liquid phase was plotted for comparison. The resulting Fourier transform infrared spectrum is shown below. Figure 3 As shown, by Figure 3 It is known that CH bonds are generally stable during the reaction between rubber particles and asphalt, so CH bonds are used as the reference peak, with a wavelength range of 840 cm⁻¹. -1 ~785cm -1 The integral area is denoted as Aera. 810 CO bonds were used as the contrast peak, with a wavelength range of 1290 cm⁻¹. -1 ~1235cm -1 The integral area is denoted as Aera. 1270 The liquid phase of the asphalt exhibits prominent CO bond peaks, while the CO bond peaks in the leachates of cups 1-4 are very blurred, indicating that the polymer containing CO bonds was not completely absorbed into the asphalt-rubber particle interaction region; furthermore, Aera 1270 With Aera 810 The ratio of the eluent from the asphalt liquid phase to the leachate in cup 1 decreased significantly, and then gradually decreased from the leachate in cup 1 to the leachate in cup 4, indicating that the rubber particles have a repulsive effect on the absorption of polymers containing CO bonds.

[0034] 6) The rubber granules from step 1) and the rubber granules after the final soaking in step 3) were subjected to thermogravimetric analysis using a Netzch TGA / DSC analyzer. The operating temperature range was 25℃~1500℃, the heating rate was controlled at 20℃ / min, and the maximum temperature was 600℃. High-purity nitrogen gas was applied at a flow rate of 500mL / min. 15mg of sample was used for each test. All samples were washed with water to remove impurities. The obtained TG and DSC curves are shown below. Figure 4 (a is the original rubber granule, b is the rubber granule soaked in tetrahydrofuran) as shown, by Figure 4 It can be seen that for the original rubber particles, the TG curve shows two main regions of mass loss at 100℃~130℃ and 300℃~500℃, while the DSC curve shows three main endothermic and one exothermic regions. These thermal characteristics are caused by changes in the composition of the rubber particle sample, including natural rubber, synthetic rubber, and minor components such as oil and water. The first mass loss and endothermic peak is due to the evaporation of water, followed by the decomposition of oil and other additives at lower temperatures (<300℃). As the temperature further increases to above 300℃, the two peaks in the DSC curves at 329℃ and 410℃ are due to the degradation of natural rubber and synthetic rubber, respectively. For the tetrahydrofuran-soaked rubber particles, the main weight loss still occurs at 300℃~500℃. However, the residual mass percentage of the tetrahydrofuran-soaked rubber particles (about 26%) is higher than that of the original rubber particles (17%), indicating that the interaction between the rubber particles and the base asphalt may consume some of the decomposable polymer.

[0035] In summary, this invention extracts components from the interaction region between asphalt and rubber particles through a layer-by-layer separation method. Then, gel permeation chromatography and Fourier transform infrared spectroscopy are used to determine the molecular weight distribution of asphalt adsorbed by the rubber particles and their absorption preference for asphalt functional groups. Furthermore, thermogravimetric analysis is performed on the original rubber particles and the rubber particles after reaction with asphalt to determine the changes in the composition of the rubber particles before and after the reaction. This allows us to understand the adsorption characteristics of rubber particles in rubber-modified asphalt and the interaction mechanism between rubber particles and asphalt, which is helpful for optimizing the formulation and designing mixing conditions for rubber-modified asphalt.

[0036] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for evaluating the adsorption characteristics and reaction mechanism of rubber particles in rubber-modified asphalt, characterized in that, Includes the following steps: 1) Disperse rubber particles in asphalt to obtain rubber-modified asphalt; 2) Separate the rubber particles and the asphalt liquid phase in rubber-modified asphalt; 3) Wrap the rubber particles separated in step 2) with a 200-mesh sieve, and then immerse them in four beakers containing tetrahydrofuran in sequence for 3 to 5 minutes each time to obtain leachate. Name the leachate beakers 1, 2, 3 and 4 in the order of immersion. Take the leachate obtained from each immersion and the asphalt liquid phase separated in step 2) for gel permeation chromatography and Fourier transform infrared spectroscopy analysis. Then, determine the adsorption preference of rubber particles for the molecular weight of asphalt based on the gel permeation chromatogram and the adsorption preference of rubber particles for functional groups in asphalt based on the Fourier transform infrared spectroscopy. 4) Take the rubber particles from step 1) and the rubber particles that have undergone the last soaking in step 3) for thermogravimetric analysis, and then determine the compositional changes of the rubber particles before and after the reaction with asphalt based on the thermogravimetric analysis data. Step 3) The ratio of rubber granules to tetrahydrofuran is 1g:5mL~10mL; The steps of the Fourier transform infrared spectroscopy analysis are as follows: The asphalt liquid phase separated in step 2) and the leachate obtained from each soaking in step 3) are placed in a 70°C water bath until the liquid becomes solid. Then, they are placed in a vacuum oven at 80°C for 8 hours to completely remove THF and water. The Fourier transform infrared spectra are then measured using a spectrometer. Simultaneously, the Fourier spectrum of the asphalt liquid phase is plotted for comparison, using the CH bond as a reference peak, with a wavelength range of 840 cm⁻¹. -1 ~785cm -1 The integral area is denoted as Aera810; the CO bond is used as the contrast peak, with a wavelength range of 1290 cm⁻¹. -1 ~1235cm -1 The integrated area is denoted as Aera1270: The asphalt liquid phase has a relatively prominent CO bond peak, while the CO bond peaks of the leachates from cups 1 to 4 are very blurry, indicating that the polymer containing CO bonds is not completely absorbed into the asphalt-rubber particle interaction region; The ratio of Aera1270 to Aera810 decreases significantly from the asphalt liquid phase to the leachate from cup 1, and then gradually decreases from the leachate from cup 1 to the leachate from cup 4, indicating the repulsion of rubber particles against the absorption of polymers containing CO bonds.

2. The method according to claim 1, characterized in that: In step 1), the mass ratio of rubber particles to asphalt is 0.15 to 0.25:

1.

3. The method according to claim 1 or 2, characterized in that: Step 1) The rubber granules are made from waste tires.

4. The method according to claim 1 or 2, characterized in that: Step 1) The rubber-modified asphalt is one of warm-mix asphalt and hot-mix asphalt.

5. The method according to claim 1, characterized in that: Step 2) involves pouring the rubber-modified asphalt onto a sieve in a sealed container and allowing it to stand, thus separating the rubber particles and the asphalt liquid phase.

6. The method according to claim 5, characterized in that: The mesh size of the sieve is 70μm to 80μm.

7. The method according to claim 5 or 6, characterized in that: The settling process is carried out at 160℃~170℃ for 50min~70min.

Images