The effect of graphene nanofiller on the crystallization behavior and mechanical properties of poly(vinyl alcohol)

The effect of graphene on the crystallization behavior of graphene/poly(vinyl alcohol) (PVA) nanocomposites is investigated in terms of the heterogeneous nucleation effect using Fourier transform infrared spectroscopy and differential scanning calorimetry. Nanometer-sized graphenes with disc-type shape are successfully fabricated by transversal cutting of platelet carbon nanofibers, and the graphene/PVA nanocomposites are prepared by varying the concentration of graphene using a solution-casting method. The graphene/PVA nanocomposites exhibit an enhanced degree of crystallization, increasing to 18.8% at a graphene concentration of 0.5 wt%. The graphene acts as an effective nucleating agent during the crystallization process, enhancing the degree and rate of crystallization. In addition, the graphene/PVA nanocomposites with a high graphene content have markedly improved mechanical properties. Mechanical properties, including hardness and elastic modulus, of the prepared graphene/PVA nanocomposites are analyzed using an atomic force microscopy nanoindentation method. The graphene plays a key role in increasing the crystallinity by acting as an effective nucleating agent at low concentrations (<1.0 wt%) and in enhancing the mechanical properties by acting as a nanofiller at high concentrations (>1.0 wt%).