Abstract
In this study epoxy/urethane (EP/PU) graft interpenetrating polymer networks (g-IPNs) nanocomposites were prepared by a simultaneous polymerization method and the effects of organophilic montmorillonite (Cloisite 30B) content on the mechanical, morphological and thermal properties of the nanocomposites were investigated. Cloisite 30B was dispersed in epoxy resin via a sonication method, after which g-IPN nanocomposites were prepared by thorough mixing of a synthesized isocyanate-terminated urethane pre-polymer with this epoxy resin (EP/PU weight ratio=75/25) followed by simultaneous curing of the resins. Polytetramethylene ether glycol (PTMEG) with molecular weight (Mw) of 3000 g/mol was used to prepare urethane prepolymers. Curing reactions were followed by Fourier Transform Infrared spectroscopy (FT–IR). Wide Angle X-ray diffraction (WAXD) was used to investigate the dispersion of Cloisite 30B in g-IPN nanocomposite specimens. Based on these results, an exfoliated morphology has been suggested for nano IPN specimens containing 1 and 3 wt.% of Cloisite 30B and an intercalated morphology for that with 5 wt.% of Cloisite 30B. Dynamic Mechanical Thermal Analysis (DMTA) was used to determine the glass transition temperature (Tg) of the IPNs. The maximum Tg was observed for the nanocomposite with 3 wt.% of Cloisite 30B. The storage modulus (E′) of nanocomposites increased with increasing clay content. Thermogravimetric Analysis (TGA), tensile measurements and Scanning Electron Microscopy (SEM) were used to study the thermal, mechanical and morphological properties of the prepared specimens. The maximum tensile properties were obtained at 3 wt.% of Cloisite 30B. Furthermore, with increasing clay content, the onset of the thermal degradation temperature was delayed.