Synthesis and thermo-mechanical properties of novel spirobiindane based epoxy nanocomposites with tryptophan as a green hardener: Curing kinetics using model free approach

In this study, novel spirobiindane based tetrafunctional epoxy resin (SBIE) was synthesized using 3,3,3',3'-tetramethyl-1,1'-spirobiindane-5,5',6,6'-tetraol reacting with epichlorohydrin. The molecular structure of the synthesized resin was characterized by Fourier transform infrared spectra (FTIR) and H-1 and C-13 Nuclear magnetic resonance spectra (NMR). The blends of SBIE with different proportions (2, 4, 6, 8 and 10 wt%) of montmorrilonite nanoclay (MMT) were prepared using ultrasonication process. The quality of dispersion and intercalation/exfoliation of the cured epoxy nanocomposites were analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM) studies. The curing reactions between SBIE and tryptophan, as an environmentally friendly curing agent, in the presence of 2,4,5-triphenylimidazole together with their nanocomposites including MMT were examined. Curing kinetic studies of the SBIE epoxy matrix and nanocomposites were characterized by differential scanning calorimetry (DSC) at different heating rates (10, 20 and 30 degrees C/min). Flynn-Wall-Ozava (FWO) and Vyzovkin (VYZ) methods were used to calculate the activation energies (Ea). The thermal degradation behaviour of the cured nanocomposites was investigated by using a thermogravimetric analyser (TGA). Moreover, the lap joint shear bonding strengths of SBIE/MMT nanocomposites were investigated. It was found that a significant improvement in thermomechanical performance of the resultant epoxy nano composites was obtained when compared to those of the neat epoxy matrices. (C) 2019 Elsevier Ltd. All rights reserved.