Preparation and Properties Evaluation of Thermoplastic Modified Epoxy Nanocomposites

Poly(methyl methacrylate) (PMMA) and montmorillonite (MMT) were used as modifiers for diglycidyl ether of bisphenol A epoxy (DGEBA). The impact strength (IS), critical stress intensity factor (KC), flexural strength, and strain at break were measured as a function of modifiers content. Scanning electron microscopy (SEM) and infrared spectroscopy were employed for the structure and morphology analysis. It was found that the maximum improvement of IS and KC was obtained for compositions containing 1% MMT or 2.5% PMMA. Moreover, the epoxy nanocomposite containing 1% MMT and 2.5% PMMA exhibited the maximum IS improvement, being approximately 175% in relation with neat epoxy resin and 55% in comparison with the nanocomposite containing only 1% MMT. However, the hybrid composition based on 1% MMT and 5% PMMA exhibited the maximum resistance to crack propagation expressed by the highest value of the KC parameter. Fourier transform infrared (FTIR) spectra showed a decrease of hydroxyl group peak intensity in all modified epoxy samples in comparison to neat epoxy resin. This decay can be explained by the formation of hydrogen bonding between the hydroxyl groups of epoxy resin and carbonyl groups of the polymeric modifier. Scanning electron microscope micrographs of ternary epoxy nanocomposites revealed the presence of a regular, homogenous, rough surface, with the latter due to, plastic yielding of the epoxy matrix.