Client Achievements | 《Polym. Degrad. Stab.》Interfacial evolution and phase stability of waste polyethylene-modified bitumen with ethylene-vinyl acetate compatibilizer under long-term oxidative aging
Release time:
2026-04-15
Recently, Guangzhou Maritime University, Tiangong University, together with TRUTH INSTRUMENTS and other institutions, have made important progress in the field of interfacial evolution and phase stability of waste polyethylene-modified bitumen under long-term oxidative aging. The research was published in Polymer Degradation and Stability, a top journal in the field of polymer degradation and stability, under the title “Interfacial evolution and phase stability of waste polyethylene-modified bitumen with ethylene-vinyl acetate compatibilizer under long-term oxidative aging”. The research team used the AtomEdge Pro Atomic Force Microscope independently developed by TRUTH INSTRUMENTS, confirming that after EVA compatibilization, a fused and homogeneous structure formed at the interface between WPE and bitumen, providing key evidence for clarifying the core mechanism of inhibiting phase separation and improving long-term aging resistance.
As the core bonding material in road engineering, base bitumen possesses viscoelasticity adaptable to traffic loads and environmental fluctuations, but defects such as high-temperature permanent deformation and low-temperature fatigue cracking limit pavement durability. Combining the global environmental problem of waste plastic accumulation with the demand for bitumen modification, the incorporation of waste polyethylene (WPE) into bitumen has become an important direction for both performance improvement and resource recycling. However, WPE and bitumen exhibit severe thermodynamic incompatibility, which easily leads to phase separation, weak interfacial bonding and other problems, resulting in the deterioration of modified bitumen performance. Ethylene-vinyl acetate (EVA) has become a potential high-efficiency compatibilizer due to its non-polar ethylene segment compatible with WPE and polar vinyl acetate groups interacting with bitumen. Nevertheless, there is still a lack of systematic research on its mechanism regulating the interfacial evolution of WPE-modified bitumen under long-term oxidative aging, which constitutes the core entry point of this study.
The research team prepared modified bitumen samples with different WPE/EVA ratios (bitumen accounts for 94 wt%, total content of WPE and EVA is 6 wt%) using 60/70 base bitumen, waste low-density polyethylene (WPE) from shopping bags, and EVA with 28 wt% vinyl acetate content as raw materials. WPE/EVA blends were prepared through a premixing process, followed by high-temperature and high-shear stirring to obtain modified bitumen. The rolling thin film oven test (RTFOT) combined with the pressure aging vessel (PAV) was adopted to simulate short-term and long-term oxidative aging (20 h, 40 h, 60 h). Multi-scale characterization methods such as atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FT-IR) were used to systematically analyze the microstructure, chemical changes, rheological properties and mechanical properties of the system.
Analysis of microstructure, chemical and rheological properties shows that EVA plays a key regulatory role in the interfacial compatibility between WPE and bitumen, significantly improving the long-term aging resistance of modified bitumen. Electron microscopy and fluorescence microscopy observations reveal that EVA transforms WPE and bitumen from a coarse two-phase structure into an interpenetrating homogeneous system by forming a nanoscale transitional interfacial phase, and maintains uniform dispersion of the polymer phase even after 60 h of PAV aging. Further chemical and thermal performance analysis confirms that the carbonyl growth rate in the EVA compatibilized system slows down significantly, and the thermal degradation curves merge into a single broadened peak, reflecting strong interfacial interaction and thermal behavior coupling. Rheological and mechanical performance tests show that after aging, the complex modulus (G*) of the compatibilized sample increases by only 83%, the phase angle (δ) remains at 34.5°, the fatigue life retention rate reaches 64%, the m-value at -18 °C maintains 0.278, and the softening point difference (ΔT) is only 1.2 °C. In contrast, the G* of the uncompatibilized sample increases by nearly 900%, δ drops sharply to 12°, fatigue life loss exceeds 90%, m-value decreases to 0.215, and ΔT is as high as 5.7 °C.
In this study, the AtomEdge Pro multifunctional atomic force microscope from TRUTH INSTRUMENTS provided key visual evidence for analyzing the compatibilization mechanism of EVA. Using tapping mode, AFM accurately characterized the morphology, phase state and three-dimensional topological structure of WPE/EVA blends and modified bitumen at different scanning scales. With the increase of EVA content, the system evolves from a coarse two-phase structure to a homogeneous and finely dispersed structure. When the WPE/EVA ratio is 5:1, the sample surface shows obvious protrusions and high-contrast phase boundaries; after adjusting the ratio to 3:3, the surface becomes smooth, the phase boundaries are blurred, and a typical compatibilized interfacial phase is formed. AFM not only accurately distinguishes WPE phase, EVA phase and bitumen matrix, but also intuitively verifies that EVA realizes the dispersion and stabilization of WPE by forming a nanoscale interfacial phase. This nanoscale structural evolution provides direct support for understanding the compatibilization mechanism of EVA and establishing the correlation between microstructure and macroscopic properties.
In summary, EVA effectively improves the compatibility between WPE and bitumen by constructing an interfacial phase where “ethylene segments anchor WPE and vinyl acetate groups interact with bitumen”, enabling modified bitumen to maintain excellent rheological properties, low-temperature crack resistance and fatigue durability after long-term oxidative aging. This study provides a scientific basis for the high-value utilization of waste plastics in road engineering and a new idea for the interfacial engineering design of polymer-modified bitumen.
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