The effects of mixing rate on morphology and physical properties of bitumen/organo-modified montmorillonite nanocomposites

• Bitumen/Cloisite 15A (3%) nanocomposites were prepared by melt compounding at various mixing rates from 750 to 4500 rpm and their morphology and physical properties were investigated.
• An exfoliated structure was observed in the bitumen nanocomposites beyond 3000 rpm.
• The bitumen nanocomposite exhibited improved rutting resistance and lower creep stiffness.

The paper reports some experimental data on the effects of mixing rate on the morphology, carbonyl index (ICO), rheological and viscoelastic properties of nanocomposite materials based on bitumen/organo-modified montmorillonite (OMMT) incorporated at 3 wt.%. The melt compounding process was carried out at 140 °C under various mixing rates, i.e. 750, 1500, 2000, 3000 and 4500 rpm. The results indicated through Wide angle X-ray scattering (WAXS) that up to 2000 rpm, bitumen/OMMT nanocomposites exhibited an intercalated structure whereas at 3000 rpm and more, an exfoliated structure was observed. Atomic force microscopy (AFM) showed an homogeneous dispersion of OMMT in the bituminous matrix accompanied with a decrease in the “bee like” structure, being however more pronounced at higher mixing rate. Differential scanning calorimetry (DSC) data indicated a decrease in the crystalline index (Xc) for both neat bitumen and bitumen nanocomposites with increasing the mixing rate. Complex viscosity (η∗) and complex modulus (G∗) were significantly improved compared to those of neat bitumen. Fourier transform infrared spectroscopy (FTIR) analysis showed a slight increase in the ICO value of bitumen/OMMT nanocomposites, especially at 4500 rpm compared to that of neat bitumen, which remained almost constant.