Synthesis and characterization of nano-SiO2 hybrid poly(methyl methacrylate) nanocomposites as novel wax inhibitor of asphalt binder

Wax crystals may continuously precipitate from the asphalt binder during the cooling process, which seriously damages the low-temperature cracking resistance of the pavement. At present, few researchers have developed wax inhibitors (WIs) to hinder wax crystallization of the asphalt binders. In this paper, a novel wax Inhibitor was synthesized by the hybridization of organically modified Nano-SiO2 to the poly (methyl methacrylate) (PMMA), and the modification effect was validated by the ninhydrin chromogenic method and thermogravimetric anal-ysis. The optimum content and composition of the organic nano-SiO2 hybrid PMMA WIs were also determined by the rheological tests, including viscosity measurement, wax precipitation temperature (WPT), and yield stress tests. Moreover, the wax inhibition mechanism was predicted by the combination of differential scanning calorimetry (DSC) and polarized optical microscopy (POM) tests. According to the obtained results, the suc-cessful modification of nano-SiO2 and PMMA were represented by the blue-violet precipitation and improved high temperature stability of PMMA, respectively. The optimal content and composition of nano-SiO2 hybrid PMMA was determined as 200 ppm and mass ratio of 1:4 (nano-SiO2 to PMMA), respectively. Compared with the co-crystallization between PMMA and wax crystals, the introduction of nano-SiO2 provided an additional and more stable heterogeneous nucleation template, which further reduced the size, and increased the dispersion of the wax crystals. Consequently, it is promising to develop the nanocomposites as WIs in the asphalt binder.