Hybrid bio-based composites from blends of unsaturated polyester and soybean oil reinforced with nanoclay and natural fibers

Hybrid bio-based composites that exploit the synergy between natural fibers (industrial hemp) in a nano-reinforced bio-based polymer can lead to improved properties while maintaining environmental appeal. Bio-based resins obtained by partial substitution of unsaturated polyester (UPE) with epoxidized soybean oil (EMS) increase toughness but compromise stiffness and hygro-thermal proper-ties. Reinforcement of the bio-based resin with nanoclays permits to retain stiffness without sacrificing toughness, while also improving barrier and thermal properties. Characterization of different hybrid composites verified this synergistic behavior in which systems with 10% EMS and 1.5 wt.% nanoclay retained the original stiffness, strain to failure, and hygro-thermal properties of the original resin while improving toughness. Optimum designs that maximize the synergy of the constituents are thus possible and the presented results provide an initial benchmark to identify such balance, and thus increase the potential applications of bio-based composites. (C) 2008 Elsevier Ltd. All rights reserved.