Epoxy resin/phosphonium ionic liquid/carbon nanofiller systems: Chemorheology and properties.

Epoxy nanocomposites with commercial carbon nanotubes (CNT) or graphene (GN) have been prepared using phosphonium ionic liquid [trihexyltetradecylphosphonium bis(2,4,4-trimethylpentyl) phosphinate, IL-f]. IL-f served simultaneously as nanofiller dispersing medium and epoxy resin catalytic curing agent. An influence of IL-f/epoxy weight ratio (3, 6 and 9/100, phr), carbon nanofiller type and content on viscosity of epoxy compositions during storage at ambient temperature was evaluated. Curing process was controlled for neat and CNT or GN modified epoxy compositions (0.25- 1.0 wt% load) using differential scanning calorimetry and rheometry. Epoxy nanocomposites exhibited slightly increased glass transition temperature values (146 to 149°C) whereas tan δ and storage modulus decreased (0.30 to 0.27 and 2087 to 1070 MPa, respectively) as compared to reference material. Crosslink density regularly decreased for composites with increasing CNT content (11 094 to 7020 mol/m3). Electrical volume resistivity of the nanocomposites was improved in case of CNT to 4 ∙ 101 Ω ∙ m and GN to 2 ∙ 105 Ω ∙ m (nanofiller content 1 wt%). Flame retardancy was found for modified epoxy materials with as low GN and phosphorus content as 0.25 and 0.7 wt%, respectively (increase of limiting oxygen index to 26.5%). [ABSTRACT FROM AUTHOR]