Epoxidized castor oil toughened Diglycidyl Ether of Bisphenol A epoxy nanocomposites: structure and property relationships

The present study highlights the structure and property relationships of epoxidized castor oil (ECO) toughened Diglycidyl Ether of Bisphenol A (DGEBA) epoxy nanocomposites. Toughened epoxy systems have been prepared by an addition of 10–40 wt% ECO to the DGEBA epoxy resin. Nanocomposites were prepared by mixing small amounts of Cloisite 30B (C30B) clay and 3‐aminopropyltriethoxysilane to the DGEBA/ECO blends. The chemical structure of toughened systems was confirmed using proton nuclear magnetic resonance and fourier transform infrared spectroscopy. The triethylenetetraamine‐cured DGEBA/ECO/C30B (8:2:0.1) nanocomposites exhibited tensile strength (50 MPa), tensile modulus (1.7 GPa), flexural strength (120 MPa), flexural modulus (3.02 GPa), and elongation (19%). The fracture toughness (critical intensity factor, K IC ) and fracture energy (critical energy release rate, G IC ) of DGEBA/ECO/C30B (8:2:0.1) system found to be higher than the other systems (2.5 MPa.m 1/2 and 1.8 kJ/m 2 for K IC and G IC , respectively). The thermal stability and heat of reaction of DGEBA/ECO blends increase with the addition of C30B clays that were analyzed using thermogravimetric analysis and differential scanning calorimetry. Rheological characterizations of uncured samples revealed a pronounced effect of the C30B clay on the DGEBA/ECO blend systems that exhibited a shear‐thickening behavior. On the other hand, the dynamic mechanical properties also revealed that the addition of C30B clays to the DGEBA/ECO blend a significant enhancements in viscoelastic and cross linking density behavior. Scanning electron microscope analysis was used to study the fractured morphology of DGEBA, DGEBA/ECO, and its nanocomposite systems. Copyright © 2015 John Wiley & Sons, Ltd.