Abstract
The polypropylene (PP) pipes were prepared using a selfβmade electromagnetic dynamic plasticating extruder, which introduced a vibration force field into the whole plasticating and extrusion process by the axial vibration of the screw. The effects of the vibration frequency and the vibration amplitude on the mechanical properties and microstructure of PP pipes were investigated using bursting pressure testing, tensile testing, impact testing, differential scanning calorimetry (DSC), and wideβangle Xβray diffraction (WAXD). The mechanical properties testing showed that the circumferential strength of PP pipes increased significantly, and the biaxial selfβreinforcement pipes could be obtained. Also, the impact strength was improved. When compared with the conventional static extruded specimens, the maximum increase of bursting pressure, tensile yield strength, and impact strength were 27.03%, 7.3%, and 16.2%, respectively. DSC and WAXD analysis showed that the PP pipes obtained by vibration plasticating extrusion (VPE) had higher crystallinity, higher melting temperature, more perfect crystals, and smaller crystal sizes, but no new polymeric crystalline peak appeared. The improvement of mechanical properties of the PP pipes prepared by VPE was attributed to the higher crystallinity and the improvement of the molecular orientation and of the crystalline morphology under the action of the vibration force field. Β© 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009