Thermoplastic polyurethane toughened polyacetal blends

Polyacetal/thermoplastic polyurethane blends at four different polyacetal w t% of 90, 80, 70 and 60 were made using a twin screw extruder. Mechanical, morphological and rheological properties of these blends were determined. T he addition of thermoplastic polyurethane (TPU) to polyacetal produces a de crease of tensile and flexural strength of the blend material as the TPU wt % increases. The notched impact strength increases with the increase of TPU wt% in the blends. Scanning electron micrographs of impact fractured surfa ces of these blends show droplet dispersion morphology. The melt flow curve s for these blends show lower melt viscosity than those of feedstocks in th e major range of experimental shear rates. The instrumented impact strength of these blends at 30 wt% TPU level are nearly nine times higher than that of polyacetal, and blends at 30 and 40 wt% TPU levels failed in a ductile manner, whereas the polyacetal failed in a brittle manner. (C) 1999 Elsevie r Science Ltd. All rights reserved.