Toughness improvement of epoxy networks by nanophase‐separating antiplasticizers

Abstract

International audienceTwo epoxy-amine networks were toughened by using a nanophase separating antiplasticizer at various contents ranging from 0 to 20 mol % with respect to the epoxide. These model networks were chosen to differ markedly by their glass transition temperature in the absence of additive, namely 180°C and 114°C. Net stress was measured as a function of crack opening displacement on single edge notch bending specimens. Analysis of the experimental data yielded both stiffness and fracture toughness. In addition, fracture surfaces were observed by scanning electron microscopy. Effect on both stiffness and toughness of network characteristics (nature of the hardener, amount of additive) were carefully examined. Conditions were found for which fracture energy at crack initiation substantially increases without any detrimental effect on stiffness

Fracture behavior of amorphous and semicrystalline blends of poly(vinylidene fluoride) and poly(methyl methacrylate)

“…Moreover, the fracture surfaces of broken specimens did not show any particular pattern, in accordance with their amorphous character. Their fracture energies are well related to the gap between the test temperature and the glass transition temperature, as already reported for other amorphous polymer series 14…”

“…Following Laiarinandrasana et al,14 both E i and E p were numerically integrated by using the experimental data. As mentioned above, they are expressed in kJ/m 2 unit.…”

“…In this first regime where χ = 0 the glass transition temperature T g (Table 1) decreases from % F = 0 to % F = 40. E i and E t were then plotted versus ( T test − T g ) as already proposed for epoxy networks 14 . T test = 20 °C is the test temperature.…”

New Phosphonate-Based Additives for Fortification in Model Epoxies

“…In recent work, phase separation of the added antiplasticizer has been considered to mediate the observed significant improvement of toughness of a model epoxy network . As reported earlier, possible clustering of fortifier molecules in DMMP fortified epoxy was investigated via a 31 P double quantum (DQ) filtered experiment.…”