The disclosure generally relates to a dispersion of nanoparticles in a liquid medium. The liquid medium is suitably water-based and further includes an ionic liquid-based stabilizer in the liquid medium to stabilize the dispersion of nanoparticles therein. The stabilizer can be polymeric or monomeric and generally includes a moiety with at least one quaternary ammonium cation from a corresponding ionic liquid. The dispersion suitably can be formed by shearing or otherwise mixing a mixture/combination of its components. The dispersions can be used to form nanoparticle composite films upon drying or otherwise removing the liquid medium carrier, with the stabilizer providing a nanoparticle binder in the composite film. The films can be formed on essentially any desired substrate and can impart improved electrical conductivity and/or thermal conductivity properties to the substrate.

The polyethylene powder satisfies (requirements 1 and 2). (Requirement 1): an intrinsic viscosity (IV) is 1.5 dL/g or more and 34.0 dL/g or less, and (requirement 2): a ratio γ.sub.0/γ.sub.1 of an elastic limit strain γ.sub.0 at a swelling time t (h) of 0 hours to an elastic limit strain γ.sub.1 at a swelling time t (h) of 1 hour is 0.80 or more and 0.95 or less, wherein the ratio is obtained from a strain dependence test .