A Novel Approach to Microfibrillated Cellulose Modification for Use as a Filler in ENR-Based Compounds

In the last few years, the tyre industry has faced new sustainability challenges, mainly regarding the substitution of fossil-based ingredients with bio-based raw materials. In fact, most of the largest tyre companies worldwide have publicly declared the objective of producing tyres with 100% sustainable materials by 2050. The main ingredients in a tyre compound are the polymer matrix and the reinforcing filler, but while natural rubber (NR) already represents a well-established bio-based alternative to synthetic polymers, the replacement of conventional reinforcing fillers remains a significant challenge. In fact, carbon black (CB), a fossil-based raw material produced from petroleum-derived feedstock, is still the main filler used in rubber compounds worldwide. A promising candidate for its replacement could be Microfibrillated cellulose (MFC): a bio-based, biocompatible, renewable, and non-toxic material, also obtained from waste biomass, with a lower density and a higher surface reactivity with respect to CB. However, the polar functional groups on its surface make it extremely incompatible with the non-polar rubber matrices used for tyre formulations. To overcome this limitation, effective compatibility strategies are required to exploit and boost these surface functionalities and promote the formation of a novel filler-polymer network. In this work, a new approach for MFC functionalisation is developed, and the synthesis and characterisation of the modified material are reported. This strategy is further applied to develop innovative MFC-reinforced epoxidised natural rubber (ENR) compounds, whose properties are compared to conventional CB-filled systems.