Sustainable materials for tyres. 1. Natural rubber compounds with better mechanical properties thanks to functionalized nanosized graphite

Natural rubber (NR), consisting in poly(1,4-cis-isoprene), is a highly stereoregular polymer. Its structure and properties actually make it the most important rubber, with a worldwide consumption of more than 12 million tons/year. The energy consumption required for the production of NR is much lower than the one required for producing a synthetic rubber: 8 vs 110 (MJ/kg) respectively. Also, the carbon footprint is lower for natural rubber: 0.4 vs 5 (kg CO2/kg). Nowadays it is clear that to have more sustainable materials for tyres, renewable sources should be preferred and therefore NR remains a material of primary importance. This work was aimed at promoting better mechanical properties for NR - based compounds by using a carbon nanofiller, a high surface area nanosized graphite (HSAG) in particular. Nanocomposites were prepared with NR and HSAG where HSAG was either pristine or functionalized with a bio based janus molecule, 2-(2,5-dimethyl-1H-pyrrol-1-yl)-1,3-propanediol (SP), commonly named serinol pyrrole (HSAG-SP) Pristine HSAG nanocomposites were prepared through melt blending while those containing HSAG-SP were prepared through latex blending. Three levels of filler, 5.2, 15 and 24 phr, were used. HSAG-SP lead to the following properties: a lower viscosity, a comparable vulcanization kinetics, a lower Payne effect according to shear strain sweep tests, better tensile ultimate properties and an improved fracture behavior. TEM analyses revealed that HSAG-SP allowed a better dispersion of the nanofiller in the rubber matrix. Such better dispersion was probably obtained thanks to the synergistic effect of the functionalization of HSAG and the preparation of the composite through latex blending. Functionalization therefore appears to be a promising tool for the reduction of the amount of filler in a rubber composite, allowing the design of lighter materials, which are required for a lower impact on the environment.