Effect of the elongational flow on mechanical properties and thermal conductivity of polypropylene-boron nitride composite fibers

Polypropylene-based composites containing high loadings (up to 30 wt.%) of boron nitride (BN) were produced through melt compounding and then subjected to uniaxial elongational flow. The mechanical characterization of the obtained fibres indicated a progressive increase of their tensile properties with increasing the draw ratio. Furthermore, composites fibres exhibited enhanced thermal conductivity as compared to their isotropic counterparts. These results were ascribed to the effectiveness on the elongational flow in improving the filler dispersion; in fact, SEM observations pointed out the achievement of a more homogeneous morphology for the composites fibers, with the disappearance of BN agglomerates observed in the isotropic materials and some preferential orientation of the embedded fillers along the flow direction.