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Copyright of Journal of South China University of Technology (Natural Science Edition) is the property of South China University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Industrial solid waste M-resin (MR) contains high sulfur content which was difficult to be comprehensively utilized. According to the vulcanization reaction mechanism, MR was used as vulcanizing agent, nano zinc oxide (ZnO) as an activator, tetramethyl thiuram disulfide (TMTD) as an accelerator to produce M-resin-based stabilizer. MR (0.5, 1, 1.5, 2, 2.5), ZnO (0.1, 0.2, 0.3, 0.4, 0.5) and TMTD (0.06, 0.08, 0.1, 0.12, 0.14) were mixed with different contents, a three-factor and five-level orthogonal experiment was designed to test the penetration, ductility, softening point and 48 h softening point difference of SBS modified asphalt. Based on the four indexes, the basic formula of the stabilizer was obtained. The influence of kaolin, an auxiliary material, on the thermal stability was compared, and the formula were optimized, the appropriate dosage was determined. The microscopic morphology of the modified asphalt and SBS developmental fineness was analyzed with the fluorescent microscopy technology, and the SBS developmental fineness was studied with the generated binary graph and skeleton graph. DSR test was carried out to detect rheological properties of modified asphalt with different dosages of MR-based stabilizes. The results show that MR can significantly improve the thermal storage stability of modified asphalt. The ratio of MR:TMTD:ZnO:Kaolin is 1.5:0.5:0.08:12, and the appropriate dosage is 1.02 %. The stabilizer can reduce the 48 h softening point difference 33.6 ℃, increase the softening point 13.6 ℃, decrease the penetration degree 9.7 mm, but it has little effect on 5 ℃ ductility index. The microscopic images show that a cavity two-phase continuous network structure is formed inside the modified asphalt under the appropriate dosage of M-resin-based stabilizer. The SBS developmental fineness is 2.36 μm, and the uniformity is good. DSR test also shows that stabilizer can effectively improve the high temperature performance of SBS modified asphalt.

In the context of the global pandemic of COVID-19, the use and disposal of medical masks have created a series of ethical and environmental issues. The purpose of this paper is to study and evaluate the high temperature properties and thermal storage stability of discarded-mask (DM)-modified asphalt from a multi-scale perspective using molecular dynamics (MD) simulation and experimental methods. A series of tests was conducted to evaluate the physical, rheological, thermal storage stability and microscopic properties of the samples. These tests include softening point, rotational viscosity, dynamic shear rheology (DSR), Fourier transform infrared (FT-IR) spectroscopy and molecular dynamics simulation. The results showed that the DM modifier could improve the softening point, rotational viscosity and rutting factor of the asphalt. After thermal storage, the DM-modified asphalt produced segregation. The difference in the softening point between the top and bottom of the sample increased from 2.2 °C to 17.1 °C when the DM modifier admixture was increased from 1% to 4%. FT-IR test results showed that the main component of the DM modifier was polypropylene, and the DM-modified asphalt was mainly a physical co-blending process. MD simulation results show that the DM modifier can increase the cohesive energy density (CED) and reduce the fractional free volume (FFV) of asphalt and reduce the binding energy between base asphalt and DM modifier. Multi-scale characterization reveals that DM modifiers can improve the high temperature performance and reduce the thermal storage stability of asphalt. It is noteworthy that both macroscopic tests and microscopic simulations show that 1% is an acceptable dosage level. [ABSTRACT FROM AUTHOR]

Copyright of Coatings & Protection / Tuceng yu Fanghu is the property of Coating & Protection Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the context of the global pandemic of COVID-19, the use and disposal of medical masks have created a series of ethical and environmental issues. The purpose of this paper is to study and evaluate the high temperature properties and thermal storage stability of discarded-mask (DM)-modified asphalt from a multi-scale perspective using molecular dynamics (MD) simulation and experimental methods. A series of tests was conducted to evaluate the physical, rheological, thermal storage stability and microscopic properties of the samples. These tests include softening point, rotational viscosity, dynamic shear rheology (DSR), Fourier transform infrared (FT-IR) spectroscopy and molecular dynamics simulation. The results showed that the DM modifier could improve the softening point, rotational viscosity and rutting factor of the asphalt. After thermal storage, the DM-modified asphalt produced segregation. The difference in the softening point between the top and bottom of the sample increased from 2.2 °C to 17.1 °C when the DM modifier admixture was increased from 1% to 4%. FT-IR test results showed that the main component of the DM modifier was polypropylene, and the DM-modified asphalt was mainly a physical co-blending process. MD simulation results show that the DM modifier can increase the cohesive energy density (CED) and reduce the fractional free volume (FFV) of asphalt and reduce the binding energy between base asphalt and DM modifier. Multi-scale characterization reveals that DM modifiers can improve the high temperature performance and reduce the thermal storage stability of asphalt. It is noteworthy that both macroscopic tests and microscopic simulations show that 1% is an acceptable dosage level.

[Display omitted] • The R (–NCO/–OH) has a significant effect on the properties of PUMA. • High-temperature performance: MOCA > BDO, low-temperature performance: BDO > MOCA. • The performance of PUMA increased significantly within 5 h at 105 °C. • PU was successfully synthesized in-situ in asphalt. • Chain extenders can help PU form long chains in asphalt. To improve the performance of ordinary road asphalt, and overcome the problems of poor thermal storage stability, easy segregation, and high preparation temperature of polymer-modified asphalt such as SBS (styrene–butadienestyrene block copolymer) or rubber powder. Polyurethane-modified asphalt (PUMA) was synthesized in-situ by the one-shot process with varying dosages of polyurethane (PU) raw materials (2.86 wt% ∼ 11.94 wt%) and isocyanate index R (–NCO/–OH) values (2, 3, 5, and 7) for a total of 12 samples, in this study. The material composition, development time, and modification mechanism of PUMA were analyzed using the approach of "macro performance + micro mechanism". Firstly, the conventional properties, rotational viscosity, and rheological properties of PUMA samples were evaluated and compared to virgin asphalt. Secondly, under the optimal material composition scheme, the conventional performance and thermal storage stability differences between MOCA (3, 3′ -dichloro-4,4′ -diamino diphenyl methane) and BDO (1,4-butanediol) were compared. Comparing the performance of PUMA during the development times of 0 to 12 h, the oven temperature is 105 °C. Fourier transform infrared spectroscopy (FTIR) and fluorescence microscopy (FM) were used to analyze the chemical structure and spatial structure of PU in asphalt. The results indicate that: 1) the higher the R (–NCO/–OH), the higher the asphalt's high-temperature performance, elastic recovery performance, and viscosity, but the lower its low-temperature performance. 2) Under the same R (–NCO/–OH) condition, the increase in PU has little effect on the preceding performance. 3) MOCA is marginally superior to BDO in terms of high-temperature performance, whereas BDO has greater advantages in terms of low-temperature performance; compatibility is comparable. 4) At 105 °C, the performance continued to improve for 0 to 5 h, but after 5 to 12 h, the improvement was no longer noticeable. 5) Due to the reaction of the isocyanate group with the polyol and the active group in the asphalt, functional groups such as carbamate and urea are directly synthesized in the asphalt, allowing the PU molecular chain to expand and form a network structure within the asphalt. This procedure modifies the performance of the virgin asphalt. These findings not only improve our understanding of the effect of optimal material composition and development time on the properties of PUMA, but they also provide direction for future research. [ABSTRACT FROM AUTHOR]

[Display omitted] It has been reported that a novel multi-component styrene-butadienestyrene composite (SBSC) modifier composed of the SBS as the main content and additional components including ethyl-vinyl-acetate (EVA), maleic anhydride grafted with ethyl-vinyl-acetate (MAH-g-EVA), naphthenic oil, and antioxidant can be produced by melt blending. This SBSC modifier can be directly mixed with bitumen and aggregate to prepare bitumen mixture, thus thoroughly addressing inferior thermal storage stability of SBS-modified bitumen. However, it is necessary to explore the efficient utilization of the SBSC modifier due to its inadequate engineering application and poor dispersion when the SBSC modifier was added directly to the bitumen mixture. The objective of this research was to investigate the feasibility of using the SBSC modifier to obtain modified bitumen with acceptable thermal storage stability and other enhanced properties. Modified bitumens (SBSC-modified bitumens with 3, 4, 5, 6, 7 % SBSC modifier content, SBS-modified bitumen with 4.5 % SBS modifier content as the control sample) were prepared. The thermal storage stability of modified bitumen was investigated by the segregation test. Besides, the basic physical properties of modified bitumen were tested, including penetration, softening point, and ductility. The rheological properties were evaluated by temperature sweep test, multiple stress creep recovery (MSCR) test, rotational viscosity (RV) test and bending beam rheometer (BBR) test, respectively. Meanwhile, fluorescence microscopy and Fourier transform infrared (FTIR) spectrometer were also applied to characterize the microproperties of the modified bitumen. Results show that the difference in softening point of SBSC-modified bitumens with modifier contents ranging from 3 % to 7 % is less than 2.5 °C after 72 h of high temperature storage at 163 °C. The softening point and ductility of SBSC-modified bitumen increase considerably with the addition of the SBSC modifier but the decrements of penetration are not significant. Besides, with the increasing addition of the SBSC modifier, complex modulus, average percent recovery, and viscosity of modified bitumen all improve. Meanwhile, phase angle, non-recoverable creep compliance of modified bitumen decrease. The flexural creep stiffness also decreases with the increasing content of the SBS modifier. When the SBS content is the same, the SBSC-modified bitumen gets better thermal storage stability, high and low temperature properties than the SBS-modified bitumen. The microproperties show that the SBSC modifier can be uniformly dispersed in base bitumen and physically mixed with the base bitumen. The SBSC-modified bitumen obtains preferable thermal storage stability. The high and low temperature properties of the bitumen are also enhanced by the addition of the SBSC modifier. Meanwhile, the melt blending method does not restrict the role of the additional components in the SBSC modifier to improve the performance of bitumen. Based on the above findings, it can be considered that the use of SBSC modifier to prepare modified bitumen with enhanced performance is a promising practice. This research may shed light on the application of SBSC modifier to bitumen pavements. [ABSTRACT FROM AUTHOR]

The thermal storage stability of styrene–butadiene–styrene tri-block copolymer modified bitumen (SBSPMB) is the key to avoid performance attenuation during storage and transportation in pavement engineering. However, existing evaluation index softening point difference within 48 h (ΔSP48) cannot effectively distinguish this attenuation of SBSPMB. Thus, conventional physical indexes, rheological properties, and micro-structure characteristics of SBSPMB during a 10-day storage were investigated in this research. Results showed that during long-term thermal storage under 163 °C for 10 days, penetration, ductility, softening point, recovery rate (R%), and anti-rutting factor (G*/sinδ) were decayed with storage time increasing. This outcome was ascribed to the phase separation of SBS, which mainly occurred after a 4-day storage. However, ΔSP48 after a 6-day storage met the specification requirements (i.e., below 2.5 °C). Thus, the attenuation degree of asphalt performance in field storage was not effectively characterized by ΔSP48 alone. Results from network strength (I) and SBS swelling degree tests revealed that the primary cause was SBS degradation and base asphalt aging. Moreover, conventional indexes, including penetration, ductility, and softening point, were used to build a prediction model for rheological properties after long-term storage using partial least squares regression model, which can effectively predict I, R, Jnr, G*/sinδ, and SBS amount. Correlation coefficient is above 0.8. G*/sinδ and I at the top and bottom storage locations had high coefficient with SBS amount. Thus, phase separation of SBSPMB should be evaluated during thermal storage. [ABSTRACT FROM AUTHOR]