From trash to treasure: Turning waste polyethylene into catalytic-cracked wax and carbon nanotubes for enhancing properties of asphalt composites

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2024-10, Vol.498, p.155747, Article 155747
• Main Authors: Han, Yongfeng, Huang, Wei, Wang, Qin, Duan, Pengpeng, Zeng, Shaohua, Chen, Pengpeng, Xu, Ying, Nie, Wangyan, Liu, Hang, Zhou, Yifeng
• Format: Article
• Language: English
• Subjects: Asphalt; Carbon nanotubes; Low temperature properties; Montmorillonite; Waste plastic; Wax
• ISSN: 1385-8947
• DOI: 10.1016/j.cej.2024.155747

•Turning waste polyethylene into wax and CNTs-MMT was achieved.•CNTs-MMT provided mechanical interlocking and chemical bonding with asphalt matrix.•Wax improved CNTs-MMT’s dispersion and reduce asphalt’s viscosity.•Under a 1:2 mass ratio of wax:CNTs-MMT, asphalt composites’ high-/low-temperature properties were optimized. The transformation of waste plastics into high-value products is becoming increasingly common. Based on the catalytic cracking of waste polyethylene, one-dimensional carbon nanotubes (CNTs) were in-situ grown on two-dimensional montmorillonite (MMT) sheets for producing a carbon nanotubes-montmorillonite hybrid (CNTs-MMT), and the cracked waxes were also synthesized, both of which were further applied to reinforce asphalt composites. By just tuning mass ratios of wax:CNTs-MMT, the dispersion degree of CNTs-MMT and ultimately high-/low-temperature properties of resultant asphalt composites could be controlled. The effects of wax and CNTs-MMT on structure-property relationships of asphalt composites were investigated. It was found that CNTs-MMT could provide both mechanical interlocking and chemical bonding with the asphalt matrix, while the wax served not only as a dispersant to enhance the dispersion level of CNTs-MMT, but also imparted a viscosity-reducing effect on the asphalt. Under the optimal mass ratio of wax:CNTs-MMT (1:2), the maximum rutting factor values at 46 °C and −18 °C of asphalt composites increased by 38.0 % and 81.8 %, respectively; corresponding average irrecoverable creep rates at 0.1 kPa and 3.2 kPa decreased by 72.9 % and 76.3 %, respectively, indicating the synergistic effect of wax and CNTs-MMT.