Effect of sepiolite filler on mechanical behaviour of a bisphenol A-based epoxy system

Sepiolite/epoxy systems, characterised by an inorganic content from 2% to 10% by weight, were tested by using different experimental techniques in order to assess the effects thermo-mechanical and fracture behaviour. It was found that filler dispersion is independent on the type of sepiolite used, i.e. hydrated and de-hydrated, whereas the addition of hydrated sepiolite strongly increases the viscosity of the final suspension. Mechanical properties have been investigated and discussed. The conservative modulus of the sepiolite/epoxy system increases as much as 21% and 94% respectively, at 35 degrees C and 200 degrees C respect to the unfilled polymer, with the incorporation of 10 wt% of sepiolite, both hydrated and dehydrated, with a slightly increasing of the corresponding glass transition temperature. The effect of sepiolite on the coefficient of thermal expansion lead to a variation in both glassy and rubbery region, respectively of about 7-8% and 9%. Fracture toughness analysis revealed that the critical stress intensity factor negligibly changes by increasing the sepiolite content, whereas the critical strain energy release rate (G(IC)) reaches an noteworthy value around 30% higher than neat epoxy. (C) 2014 Elsevier Ltd. All rights reserved.