Poly (vinylidene fluoride) (PVDF)/graphite composites were prepared by
solution mixing technique then subjected to hot compression molding. Tensile
mechanical properties of prepared composites were studied at different
temperatures between 30 and 90 oC. The results indicated that, the elastic
modulus, tensile strength, and ultimate elongation achieved a significant
improvement with addition of graphite showing maxima around 3.9vol%
graphite, followed by a decrease with further increases of the graphite content.
This behaviour suggested the formation of a compact structure, and above a
content of 3.9vol% graphite, this compact structure became more loose. These
results were confirmed by both SEM and DSC measurements. DSC
measurement indicated that graphite content has significant influence on the
degree of crystallinity for PVDF composites. Also, study of the melting
behaviour suggested the presence of only α-crystalline phase in neat PVDF and
PVDF/G composites. The observed values of the elastic modulus of the
composites are in close agreement with those calculated by Halpin-Tsai's
model, taking into account the variation of the aspect ratio (αg) of the graphite
structure with the volume fraction of the graphite in the matrix. The elastic
modulus, tensile strength and yield stress were found to decrease with
increasing the working temperature, while the ultimate elongation exhibit
opposite trend.