Synergistic reinforcement of a reversible Diels–Alder type network with nanocellulose

Abstract

Covalent adaptable networks are attractive intermediates between thermosets and thermoplastics. To achieve an optimal combination of dimensional stability at the temperature of use and macroscopic flow at elevated temperatures, materials that combine two reversible networks are highly sought after. We demonstrate that such a material can be created through the addition of cellulose microfibrils to a polymer matrix that can undergo thermoreversible Diels–Alder reactions. The cellulose microfibrils and crosslinked polymer form two independent reversible networks that display clear synergistic effects on the thermomechanical properties of the nanocomposite. Above the glass transition temperature of the polymer matrix the two networks work in tandem to reduce tensile creep by a factor of 40 at 80 °C, while increasing the storage modulus by a factor of 60 at the same temperature. The adaptability of the Diels–Alder network is not compromised by the addition of cellulose microfibrils, as shown by kinetic studies and repeated reprocessing. Further, the cellulose network significantly improves the dimensional stability at elevated temperatures where the Diels–Alder network dissociates.