Morphological structure and mechanical properties of epoxy/polysulfone/cellulose nanofiber ternary nanocomposites

Despite some work on epoxy resin/cellulose nanofiber (CNF) system, it remains unclear how CNF affects microstructure and mechanical properties of epoxy/polysulfone (PSF) binary blends so far. We herein introduced CNF into the blends via a combination of solvent exchange and melt mixing. Results show that epoxy/PSF binary blends display three distinct types of phase separated structures but slightly affecting mechanical properties because of poor interfacial adhesion. However, only adding small amount of CNF can enhance impact toughness and tensile strength due to improved interfacial adhesion, probably arising from hydrogen bonding interactions between CNF surfaces and matrix polymers, and penetrating and bridging effects of CNF between different phases. For example, compared with the epoxy/PSF blends, adding 0.2 wt% of CNF can increase impact strength by ∼49%. Additionally, 0.3 wt% of CNF can increase the glass transition temperature by ∼18 °C relative to the epoxy resin.