Fabrication and characterization of emulsified and freeze-dried epoxy/cellulose nanofibril nanocomposite foam

Utilization of cellulose nanofibril (CNF) material for light weight and high strength structural composites has attracted considerable attention in the recent years. CNF aerogels have a microporous structure that could have potential properties, such as ultra-low density, high porosity, high specific surface area, high flexibility, and low thermal conductivity. However, producing such a product is still somewhat problematic. In this study, an epoxy/CNF (EP/CNF) nanocomposite foam with micro-rib structures has been developed using emulsification combined with freeze-dried processes. The microstructures of these new EP/CNF composite foams were observed using a scanning electron microscope. The surface morphology showed that CNF fiber walls were uniformly sealed with epoxy resin after curing. Mechanical properties, water resistance, and thermal stability of the EP/CNF composites foams were tested using the compression test, water absorption test, and thermogravimetric analysis. The results showed that the CNFs played an important role in forming a skeleton like structure within these composite foams. The amount of EP in the EP/CNF emulsions had significant effect on the compressive properties and water resistance. Samples fabricated with higher epoxy content had higher compressive properties, better water resistance, and thermal stability. The epoxy/CNF nanocomposites properties were significantly improved as compared to pure CNF aerogel. The glass transition temperature (T_g) of the nanocomposites was influenced by the EP/CNF composition. The mechanical and physical properties of EP/CNF nanocomposite foams could be optimized via changing the weight ratio of epoxy resin in EP/CNF emulsion according to the demanding of specific application.