The effect of fibre concentration on the α to β-phase transformation, degree of crystallinity and electrical properties of vapour grown carbon nanofibre/poly(vinylidene fluoride) composites

Vapour growth carbon nanofibres/poly(vinilidene fluoride) - VGCNF/PVDF - composites prepared by solution casting were studied. The spherulitic crystallisation morphology of the pure polymer is maintained for the composites. Mechanical stretching of the composite films induces the alpha to beta-phase transformation within the polymer matrix. This phase transition is accompanied by the destruction of the spherulitic microstructure in favour of a microfibrillar one. The incorporation of the VGCNF in the PVDF matrix increases the degree of crystallinity of the polymer composites for concentrations lower than similar to 1%, remaining stable for higher VGCNF concentrations. With respect to the electrical properties, the stretching associated to the phase transformation induces a change in the conduction mechanism: the alpha-phase composite demonstrates a percolative behaviour on the measured conductivity whereas the beta-phase demonstrates typical ionic conduction behaviour. Dielectric measurements in conjunction with the the two exponent percolation phenomenological equation demonstrates that in the beta-phase an effective reduction in the ratio VGCNF length/domain length could induce the observed percolation behaviour. (C) 2009 Elsevier Ltd. All rights reserved.