Effect of dynamical converging channels on fiber organization and damage during vane extrusion of sisal fiber-reinforced polypropylene composites

It is well known that converging channel can generate elongational deformation field. In this study, novel dynamical converging channels were successfully incorporated into plant fiber-reinforced thermoplastics composites processing. A dynamical elongational deformation field (DEDF) generated by these channels was studied. The fiber organization and damage in the DEDF has been investigated in terms of its relationship to changes in rotating speed of the channels. A vane extruder based on these channels was used to prepare sisal fiber-reinforced polypropylene composites. By investigating rapidly cooled samples in the vane extruder, sisal fiber in the center part of these channels has an orientation with an angle to the discharging direction. Rotating speed increases from 30 to 90 r/min result in 30.9942.7% decreases in average fiber length. The issues of fiber distribution and voids formation have been related to the mechanical properties of the composites, particularly tensile strength and modulus. Increased rotating speeds from 30 to 90 r/min results in tensile strength and modulus increases of about 21.3% and 11.6%, respectively. The majority of this change is caused by decreased voids formation with the increases of speed, which is in agreement with scanning electron microscopy of the composites. POLYM. COMPOS., 2012. (c) 2011 Society of Plastics Engineers