The effect of strain rate on the toughening mechanisms of rubber‐modified plastics

Abstract

Abstract The impact modification mechanisms of polycarbonate (PC) blended with polyethylene (PE) and blends of polyxylenol ether (PXE)/high impact polystyrene (HIPS), were studied using a volume dilation technique. With two extensometers, measurements of volume change during tensile deformation were made on the plastics. Strain rates of 2 × 10 −5 s −1 to 4 s −1 were achieved with a MTS servo‐hydraulic testing machine. Analysis of both systems were supported with scanning and transmission electron microscopy. Results on the PC/PE system indicate that the impact modification mechanism is one of voiding and shear banding. The mechanism appeared to be rate sensitive: the amount of voiding increased with rate. The toughening mechanism in the PXE/HIPS blends is identified as a combination of crazing and shear banding. The amount of shear banding that occurs is proportional to the amount of PXE in the blends. The point of craze initiation was found to be delayed by increasing strain rate. The stress for craze initiation appears to be greater than for shear banding.