Bifunctional, trifunctional, and tetrafunctional epoxy (EP) resins were hardened with stoichiometric amount of 4,4'-diaminodiphenyl methane in presence and absence of benzoxazine (BOX). The EP/BOX ratio of the hybrid systems was constant, viz. 50/50 wt %. For the bifunctional EP, the EP/BOX range covered the ratios 75/25 and 25/75 wt %, as well. Epoxy-terminated liquid nitrile rubber (ETBN) was incorporated in 10 wt % in the systems with trifunctional and tetrafunctional EP, and in 10, 15, and 20 wt % in the EP/BOX with bifunctional EP to improve their toughness. Information on the structure and morphology of the hybrid systems was received from differential scanning calorimetric, dynamic-mechanical thermal analysis, atomic force microscopic, and scanning electron microscopic studies. The flexural, fracture mechanical properties, thermal degradation, and fire resistance of the EP/BOX and EP/BOX/ETBN hybrids were determined. It was found that some homopolymerized BOX was built in the EP/BOX conetwork in form of nanoscale inclusions, whereas ETBN formed micron scaled droplets of sea-island structure. Incorporation of BOX improved the charring and fire resistance, enhanced the flexural modulus and strength, reduced the glass transition (T g ), the fracture toughness, and energy. Additional modification with ETBN decreased the charring, fire resistance, flexural modulus and strength, as well as T g, however, improved the fracture toughness and especially the fracture energy.

The present work was aimed at studying the effects of incorporation of epoxidized soybean oil (ESO) in a standard bisphenol A-type epoxy resin (EP) cured by anhydride hardener. The EP/ESO ratio was set for 100/0, 75/25, 50/50, 25/75 and 0/100 (wt.%/wt.%). The investigations performed covered the curing, rheology (gelling), thermomechanical (TMA) and thermogravimetric analysis (TGA) of the EP/ESO compositions. The results showed that the dilution of EP with ESO was accompanied with marked changes in the curing, gelling behavior and final properties. Differential scanning calorimetry (DSC) revealed that the crosslinking of EP/ESO≥50/50 occurred in two steps. This has been considered for the cure schedule set. The gel time of EP/ESO, determined at T=100, 120, 140 o C, respectively, increased with increasing ESO content. The activation energy of gelling increased with increasing ESO content. The glass transition temperature decreased with increasing ESO content of the transparent samples. According to TMA the coefficient of thermal expansion in the glassy state increased with increasing ESO content but was independent of the latter in the rubbery stage. TGA indicated that with increasing ESO content the thermal degradation started earlier and the char yield decreased. The Ozawa, Flynn and Wall (OFW) approach was adapted to TGA tests to calculate 2 the activation energy of thermal degradation. The activation energy depended on the ESO content of the EP/ESO blends and also on their actual decomposition stage. The latter means a limitation for the OFW approach.

Vinylester nanocomposites with graphene and carbon nanotubes were investigated regarding thermal and viscoelastic behaviour, flexural properties, hardness, scratch resistance and electrical conductivity. The latter showed a percolation threshold for the graphene nanocomposites at y2 wt-%, whereas the nanotube system exhibited this transition at 0?03 wt-%. Investigations (SEM) by charge contrast imaging demonstrated a high degree of dispersion of both fillers, with the formation of a continuous percolation network. Quantitative tests regarding the corrosion resistance revealed that the conductive hybrid composites, applied as a coating to a metal substrate, exhibited a better performance than the neat vinylester.