Preparation of novel bitumen nanocomposites out of polymer-modified montmorillonite nanoparticles

To extend the time of service of asphalt roads modified montmorillonite nanoparticles were incorporated into bitumen with the aim of creating a gas barrier inside the bitumen which slows down the diffusion of oxygen through the bitumen. For this purpose [montmorillonite/alkyl-quat-primer] adducts ([MMT/PEI(nkD)xQyR]) were fabricated in which single-montmorillonite platelets were coated by a ultrathin polymer film by reacting montmorillonite particles with poly(ethylenimine) based polycations. The alkyl-quat-primer polymers were synthesised by adding ammonium groups and alkyl chains to hyperbranched poly(ethylenimine)s in a solvent-free reaction. Adducts with fully intercalated polymers were obtained when the polymers were reacted with an aqueous solution of [MMT/CTAB] or by mixing the polymers with montmorillonite and CTAB in an aqueous solution. The polymers replaced the CTAB in an intermediate formed [MMT/CTAB] adduct and adhered strongly to the montmorillonite due to a cooperative electrostatic interaction between the positively charged ammonium moieties of the macromolecules and the negatively charged montmorillonite surface. [MMT/alkyl-quat-primer] and [MMT/CTAB] adducts were incorporated via a single screw extruder into polymer- and non-polymer-modified bitumina to create bitumen-nanocomposites. Composites prepared under optimised conditions exhibited an adduct network inside the bitumen at adduct concentrations larger 5 wt.% and when non-polymer modified bitumina were modified. The aspect ratio of the incorporated montmorillonite platelets depended strongly on the adduct composition and the used bitumen, and was with [MMT/PEI(10kD)10Q80R10] adducts were very high (~ 300 - 1000) but with [MMT/PEI(10kD)10Q60R14] and [MMT/CTAB] adducts considerably lower (~ 30 - 90)