Rotomolded antistatic and flame-retarded graphite nanocomposites

Abstract

Graphite nanoplatelets with an average particle size of 13 μm and an estimated flake thickness of about 76 nm were prepared by microwave exfoliation, followed by ultrasonication-assisted liquid-phase delamination, of an expandable graphite. This nanoadditive was used to fabricate linear low-density polyethylene (LLDPE) and poly(ethylene-co-vinyl acetate) (EVA)-based nanocomposite sheets using rotational molding. The dry blending approach yielded surface resistivities within the static dissipation range at filler loadings as low as 0.25 wt.% (0.1 vol.%). However, even at this low graphite content, impact properties were significantly reduced compared to the neat polymers. Bilayer moldings via the double dumping method proved to be a feasible approach to achieve both acceptable mechanical properties and antistatic properties. This was achieved by rotomolding nanocomposite sheets with a 1-mm outer layer containing the filler and a 2-mm inner layer of neat LLDPE. Excellent fire resistance, in terms of cone calorimeter testing, was achieved when the outer layer also contained 10 wt.% expandable graphite.