The MoS₂ powder (MS, 99.0 wt%) in 1250 mesh was provided by Liaoning Zhonglian Industrial Group Co., Ltd., Liaoning, China. Naphthenic oil (NO) was purchased from Karamay Company, Karamay, China, and linear SBS was purchased from China Petroleum and Chemical Corporation Limited, Beijing, China, as shown in Fig. 1. The matrix asphalt (70#) was supplied by Qilu Petrochemical Company, Zibo, Shandong, China, and the main physical properties are illustrated in Table 1. PPA was obtained from Sigma Aldrich, Shanghai, China, which had a P₂O₅ content exceeding 90%.

After drying at 100°C in an oven for 24 h, 60 g MoS₂ was ground in a planetary ball mill with 150 g NO. Then, 10 g PPA was added to the mixture and mixed. The planetary ball mill was equipped with an appropriate gradation to utilize agate balls (10:8:5 mm) as the grinding medium. After 40 min, the modified MoS₂ was obtained and separated from the slurry, which was then referred to as OMS-PPA. Samples with different weights of PPA (0, 10, 20, and 30 g) were called OMS, 1-OMS-PPA, 2-OMS-PPA, and 3-OMS-PPA, as shown in Table 2. The composite modified asphalt was created by mixing SA (with 5 percent SBS) and 5 wt% OMS, 1-OMS-PPA, 2-OMS-PPA, and 3-OMS-PPA at 170°C and designated SA-OMS, 1-OMS-PPA, 2-OMS-PPA, and 3-OMS-PPA. Both modified asphalts were sheared at a speed of 3000 RPM for 30 min. Then, the asphalt swelled and grew at 130°C for another 30 min. Table 3 shows the various ratios of materials for modified asphalts.

The chemical groups on the surfaces of NO, MS, OMS, and OMS-PPA were analyzed using a Fourier transform infrared spectra (FTIR) spectrometer (Thermo Fisher Nicolet IS50, USA) from 400 to 4000 cm⁻¹ at room temperature. The X-ray diffraction (XRD) patterns of MS, OMS, and OMS-PPA were recorded by a high-resolution powder X-ray diffractometer (Empyrean, Almelo, Netherlands) with a copper target. The morphology of MS, OMS, and OMS-PPA was investigated on a scanning electron microscope (SEM, JEOL JSM6390LV, Tokyo, Japan) with an acceleration voltage range from 0.1 to 30 kV. The basic properties of SA, SA-OMS, and SA-OMS-PPA were analyzed based on the standards (ASTM D36, ASTM D113, and ASTM D5), which included its penetration, softening point, and ductility. A rotational viscometer (Brookfield, Massachusetts, USA) was used to test the viscosity values of SA, SA-OMS, and SA-OMS-PPA at temperatures between 130°C to 180°C with a 10°C span. A dynamic shear rheometer (DSR, Anton Paar Smartpave102, Austria) was utilized to test the rheological behavior of SA, SA-OMS, and SA-OMS-PPA. DSR values were maintained by operating at a fixed frequency of 10 rad·s⁻¹ at 45°C to 90°C per 5°C. A fluorescence microscope (Leica M205FA, Germany) was used to observe the particle dispersion of SA, SA-OMS, and SA-OMS-PPA. The thin film oven test (TFOT) was used in this experiment to evaluate the short-term aging behavior of SA, SA-OMS, and SA-OMS-PPA in compliance with ASTM-D1754 standards. The SA, SA-OMS, and SA-OMS-PPA were subjected to heating at 163°C for 5 h during this artificial simulation aging procedure. The spectral method used to evaluate the carbonyl index of SA, SA-OMS, and SA-OMS-PPA involved the use of an attracted total refraction model (ATR-FTIR) on a Thermo Fisher Nicolet IS50, which is from the USA. The surficial micromechanical properties of SA, SA-OMS, and SA-OMS-PPA were tested using a nanoindentation instrument (NANOVEA CB500, USA) with a maximum load of 0.12 mN.

The FTIR spectra of NO, MS, OMS, and OMS-PPA were shown in Fig. 2. Approximately 480 cm⁻¹ was observed with identical peaks due to the stretching vibration of the Mo-S bond from the spectra of MS, OMS, and OMS-PPA [31]. The OMS spectra showed peaks at 2923 and 2852 cm⁻¹ that were much more clearly, along with 1456 and 1375 cm⁻¹. The surface or interlayer of MS had NO adsorbing causing these peaks. OMS was activated by the milling balls while grinding the rotating planetary mill. The stretching vibration of P-O is found in the molecule structure of PPA and is represented by new peaks at 1131 and 985 cm⁻¹ when compared to OMS. The stretching vibration of O-H can be identified by the peak at 3500 cm⁻¹. The evidence showed that PPA grafted and created many hydrogen bonds between OMS.

The (002) plane of MS was reflected in both peaks on 2θ = 14.44° in the XRD patterns of MS, OMS, and OMS-PPA shown in Fig. 3. The interlayer distances of MS were estimated using Bragg’s equation. Both the interlayer spaces of MS, OMS, and OMS-PPA were 0.613 nm, as determined by the formula. XRD patterns did not influence the differences between MS, OMS, and OMS-PPA. MS has adapted a layered crystalline structure that consists of a Mo atomic layer sandwiched between S atomic layers by bonds [24]. MS, OMS, and OMS-PPA’s XRD intensity values changed from decreasing to increasing during the first peak. The contour of the OMS-PPA in Fig. 4 was characterized by a peeled layered structure, which was more noticeable than MS and OMS. Partial loading of NO molecules caused contrast changes in the SEM image of OMS-PPA. Under the influence of mechanical force, a large number of active sites on OMS-PPA could be generated.

To estimate their basic properties, Fig. 5 shows the testing of SA, SA-OMS, and SA-OMS-PPA’s ductility, softening point, and penetration. SA-OMS and 1-SA-OMS-PPA had a 111.6% and 30.2% increase in ductility when compared to SA. OMS enhanced the asphalt’s ability to resist displacement. The interaction between asphalt molecules and OMS particles was increased by PPA, which resulted in a reduction in resistance effects between them. As the amount of PPA used in OMS-PPA increased, the ductility of modified asphalt decreased sharply The basic requirements of modified asphalt were not met by 2-SA-OMS-PPA and 3-SA-OMS-PPA, even though the added OMS-PPA was 5 wt%. The surface of MS was activated by NO, causing SA-OMS-PPA to have a lower softening point than SA. The dispersibility of OMS particles in asphalt was superior to that of common layered materials. When compared to SA, 1-SA-OMS-PPA had a softening point that was 1.1% higher. The interaction between asphalt molecules and particles led to a higher softening point of SA-OMS-PPA compared to SA after being modified by OMS and PPA. A growing trend was observed in the softening points of 1-SA-OMS-PPA, 2-SA-OMS-PPA, and 3-SA-OMS-PPA when the amount of PPA grew. Additionally, the penetration of 1-SA-OMS-PPA exceeded SA by 61.3%. The potential reaction between PPA and asphalt resulted in a boost in 1-SA-OMS-PPA’s ductility and softening point.

The temperature sensitivity and colloidal structure of modified asphalts can be characterized by the penetration temperature coefficient and penetration factor [32]. Linear fitting was used to calculate the penetration-temperature coefficients of different modified asphalts with penetration values between 15°C and 30°C, as shown in Fig. 6. As demonstrated in Fig. 7, the penetration factors of various modified asphalts can be further calculated. In Fig. 6, the penetration-temperature coefficient of SA-OMS decreased by 3.7% compared to SA. The dispersion of OMS particles was optimized by OMS’s surface being able to bring in a small number of lightweight components. The modified asphalt and the integrity of the asphalt system became stronger thanks to the enhanced role of OMS. Compared to SA, 1-OMS-PPA, 2-OMS-PPA, and 3-OMS-PPA experienced a decrease of 7.1%, 9.5%, and 11.2% in their penetration temperature coefficient. The penetration temperature coefficients of modified asphalts decreased as PPA levels increased. The stability of modified asphalts could be improved by PPA’s interaction with the asphalt molecules. The temperature sensitivity of modified asphalt is significantly reduced by PPA’s effects [33]. According to Fig. 7, the increase in penetration factors was correlated with the decrease in penetration-temperature coefficient. The temperature sensitivity of modified asphalt was reduced by the OMS and PPA due to its penetration factors. The combination of Figs. 6 and 7 resulted in OMS-PPA’s critical role in optimizing the stability of modified asphalt, and it could strengthen the gel structure of modified asphalt. The findings showed that PPA molecules had a substantial effect on the consolidation of modified asphalt.

In Fig. 8, the modified asphalts showed good dispersion under fluorescence irradiation, as evidenced by fluorescence microscopy images. The luminescent groups present in SBS molecules allow for the observation of bright light spots of modified asphalt during fluorescence microscopy images [34]. The fact that SBS dispersed evenly at a combined treatment temperature of 170°C in SA is indicative of its good dispersion at lower stirring temperatures, as seen in Fig. 8a. The uniformity of the dispersed spots of the modified asphalt was achieved when OMS mixed with SA under similar conditions. In SA-OMS, OMS and SBS could interact, which improved the dispersion and compatibility of SBS in SA-OMS in Fig. 8b. The distribution of OMS was difficult to observe due to its weak fluorescence. As demonstrated in Fig. 8c–e, there was an increase in the dispersion of spots in the SA-OMS-PPA. The distribution of SBS modified asphalt by 1-SA-OMS-PPA was superior to that of SA-OMS. Following PPA’s adjustments, OMS grafted additional functional groups, which could potentially interact with the asphalt molecules in 1-SA-OMS-PPA. The clustering of spots is observed in Fig. 8d,e. The mixing ratios of materials during experiments resulted in a gradual increase in PPA compared to 1-SA-OMS-PPA, 2-SA-OMS-PPA, and 3-SA-OMS-PPA. PPA molecules had a significant potential reactivity with asphalt molecules [35]. When combined with Figs. 6–8, the results showed that OMS-PPA had a significant strengthening effect on optimizing the modified asphalt.

By analyzing the melting processing of asphalt in Fig. 9, it tested the viscosity of modified asphalt with a fixed torque and shear rate. The viscosity of SA at 130°C was 11.08 Pa·s, as shown in Fig. 9. SA-OMS had a viscosity decrease of 47.65% compared to SA. By facilitating the use of lightweight components, it improved the flow of molecules in modified asphalt [36]. Ultimately, it decreased the viscosity values of asphalt in the Newtonian region. At 130°C, SA-OMS showed a 23.47% decrease in viscosity, while 1-SA-OMS-PPA experienced a 46.2% increase. SA-OMS-PPA had a 13.33% increase in viscosity at 180°C, while the viscosity at SA-OMS-PPA decreased by 34.78% more than SA-OMS. The viscosity of SA-OMS-PPA increased in comparison to 1-SA-OMS-PPA, 2-SA-OMS-PPA, and 3-SA-OMS-PPA. More potential cross-linking points were created with the asphalt molecules in SA-OMS-PPA due to the interaction between PPA molecules on the OMS surface and the asphalt molecules in SA-OMS-PPA. Thermal shearing can lead to the disintegration and reconstruction of this approximate spatial network structure, while the viscosity of modified asphalt continues to increase. The modified asphalt with higher PPA content had more cross-linking points, which led to a higher shearing viscosity value of SA-OMS-PPA. In Fig. 10, the thermal stability of SA-OMS-PPA can be examined by combining the rheological properties of asphalt at different temperatures and the Arrhenius equation. Linear fitting of viscosity values can be used to estimate the activation energy of modified asphalts between 130°C and 180°C. The fitted lines had R² values that were more significant than 0.98, indicating a higher degree of fitting reliability. To overcome obstacles caused by internal cross-linking, modified asphalt requires the force represented by activation energy. The difficulty of flowing molten asphalt and its sensitivity to temperature are visually illustrated. It was revealed that PPA could increase the temperature sensitivity of asphalt. Excessive PPA could cause the asphalt system to be unstable and decrease its reinforcing effect on the asphalt. PPA is likely to react with water molecules in the air and cause side reactions in asphalt systems due to its potential reactivity.

Fig. 11 was used to analyze the rheological properties of modified asphalt at different temperatures, using the principle of time-temperature equivalence. As shown in Fig. 11a, SA-OMS’s storage modulus (G’) at 45°C reduced by 41.52% compared to SA. The storage modulus value of 1-SA-OMS-PPA was higher by 21.49% compared to SA-OMS. The activation of NO molecules on the surface of MoS₂ resulted in asphalt molecules being prone to movement between them. The elastic behavior of 1-SA-OMS-PPA was enhanced by many groups of PPA’s potential interactions with asphalt molecules after further modification by PPA. The increase in PPA caused a sharp increase in the elastic modulus of modified asphalt [21]. The internal interaction and elastic behavior of modified asphalts were enhanced due to its improvement. Asphalt lost its elastic behavior as the temperature rose, turning it from viscoelastic to flowing liquid. SA-OMS’ loss modulus (G′′) decreased by 45.266% at 45°C when compared to SA, while 1-SA-OMS-PPA’s storage modulus increased by 13.18% more than SA-OMS, as seen in Fig. 11b. The elastic modulus and the loss modulus had similar trends. The elastic behavior of asphalt could be optimized by combining both asphalts modified with OMS and OMS-PPA with Fig. 11a,b. The storage modulus value of 1-SA-OMS-PPA was 17.56% higher than SA-OMS, while the tanδ at 45°C of SA-OMS decreased by 43.4% more compared to SA. Modified asphalts’ tanδ exhibited an increasing trend as the temperature increased, but the degree was not the same. The molecular motion of the modified asphalt increased in activity as temperature increased, leading to a gradual transition into a fluid state. SA-OMS had a decrease in elastic properties, while modified asphalt had an increase in viscous properties. Despite the decrease in viscous properties of modified asphalt, the elastic properties of 1-SA-OMS-PPA increased more than SA-OMS. As demonstrated in Fig. 11d, the temperature had a negative impact on the rutting factors (G*/sinδ) of modified asphalts. The G*/sinδ at 45°C of SA-OMS and 1-SA-OMS-PPA were both less than SA, but the G*/sinδ of 1-SA-OMS-PPA was more significant than that of SA-OMS. Modified asphalts experienced a significant increase in G*/sinδ as the amount of PPA increased. OMS-PPA was found to have a significant impact on the viscoelastic behavior of modified asphalts.

The main substance of asphalt was hydrocarbons, which would form new carbonyl groups when the molecule chain breaks down during irradiation or oxidation conditions [37,38]. In Fig. 12, the functional group changes of modified asphalt were analyzed using ATR-FTIR. Absorption peaks were found in the unaged modified asphalt at 2960 and 2870 cm⁻¹, which are associated with the -CH₂ groups, and a peak at 1380 cm⁻¹, which is associated with the -C-CH₃ groups. Carbonyl peaks did not occur on the curves of unaged asphalts, including SA, SA-OMS, and SA-OMS-PPA, when modified asphalts were unaged. A carbonyl peak of 1699 cm⁻¹ was observed in modified asphalts after the RTFO test. The peaks at 1699 cm⁻¹ were quite distinct from those of SA, SA-OMS, and 1-SA-OMS-PPA. By comparing the curves in Fig. 13, it is possible to estimate the percentage of carbonyl groups in aged asphalts. Short-term aging resulted in a 5.93% increase in the carboxyl groups (C=O, 1699 cm⁻¹) generated in SA. SA-OMS and 1-SA-OMS-PPA experienced a 1.36% and 0.93% increase in their carboxyl groups, respectively. The amount of carboxyl groups in 2-SA-OMS-PPA was 1.45%, while that of 3-SA-OMS-PPA was 1.52%. Both OMS and OMS-PPA were shown to be capable of delaying the aging of modified asphalt. The effects of 1-SA-OMS-PPA were superior compared to other modified asphalts. The oil grinding process resulted in a reduction in MS particle size and an increase in its specific surface area. Certain aromatic compounds and polymers can be absorbed from asphalt using this method. Additionally, NO is capable of compensating for the volatilization and oxidation of light components in asphalt during the aging process. The dosage of PPA led to a gradual decrease in the aging resistance performance of modified asphalts, but an increase in the dosage of OMS.

By pressing an indenter into the sample shown in Fig. 14, it is possible to record the load data and analyze the depth and hardness parameters on the surface of modified asphalts through nanoindentation [39]. Modified asphalt’s mechanical properties could be optimized by obtaining the aging degrees and optimization effect after short-term treatment. The maximum depth of modified asphalt will decrease and its hardness will increase as the age degree increases [40]. Different modified asphalts had their maximum depth and hardness distribution listed. The color changed from blue to red, indicating either a gradual increase in hardness value or a gradual decrease in depth. The depth of SA-OMS was higher than SA, while the hardness of SA-OMS was lower. The penetration and G*/sinδ of asphalts were altered in a consistent manner. The asphalt would undergo a transformation from gel structure to sol structure by introducing small molecules of OMS. The depth of 1-SA-OMS-PPA decreased when compared to SA-OMS and 1-SA-OMS-PPA, but it increased in hardness when compared to SA-OMS. The composite system could be transformed into a gel structure by PPA’s interaction with asphalt molecules. The RTFO test resulted in a 38.98% decrease in the depth of SA, while the hardness increased by 51.72%. SA-OMS had a depth decrease of 14.28%, but its hardness increased by 29.44%. SA experienced a 15% decrease in depth, but its hardness increased by 18.02%. The depth change ratio of SA was decreased by 63.37% for SA-OMS, and by 61.52% for 1-SA-OMS-PPA. The hardness changing ratio of SA decreased by 43.08%, while 1-SA-OMS-PPA decreased by 65.16%. With the addition of PPA, the aging resistance performance of modified asphalts gradually deteriorated. The instability in its system could be due to the excessive reaction between PPA and asphalt molecules. OMS and OMS-PPA were proven to have aided in optimizing the structure of asphalts and improving their aging resistance performance.

The primary benefit was the enhancement of the dispersibility of MS oil milled by PPA in asphalt and the optimization of temperature sensitivity and aging resistance of modified asphalt. It contributed to the design and preparation of long-lasting asphalt pavements and decreased maintenance costs. Additionally, it may decrease the use of asphalt materials and lessen the impact on the environment.