Influence of fiber orientation and length distribution on the rheological characterization of glass-fiber-filled polypropylene

We report on the characterization of glass-fiber-filled polypropylene compounds identified by means of rotational rheometry in parallel plate mode. The small gap between the plates and the length of the glass fibers cause considerable wall and initial orientation effects, which we minimized by applying various degrees of pre-shearing, optimizing both duration and level of shear deformation. The results were verified using X-ray computed tomography to investigate the dispersion of glass fibers in the melt. In addition, extrusion experiments confirm the validity of our results. (C) 2013 Elsevier Ltd. All rights reserved.