MORPHOLOGY AND RHEOLOGICAL PROPERTIES OF PE/PP BLEND FIBERS

Blends af high density polyethylene (HDPE) and polypropylene (PP) were prepared by the melt mixing method. The morphology and the rheological properties of extrudates were measured and related with the physical properties of the melt spun fibers, such as X-ray diffraction patterns, tensile properties, and birefringence. From the SEM photographs of the fractured surfaces, it can be seen that PP forms a continuous phase in blends of 25% and 50% of HDPE. while HDPE formed in a 75% blend. In all cases, the discrete phases were finely distributed. The viscosity and the melt elasticity of HDPE were higher than those of PP and those of HDPE/PP blends were intermediate. The first normal stress difference of the extrudates increased with the increase of HDPE content, and thus the birefingence and the initial modulus of the spun fibers did with the HDPE content. However, the crystalline orientation did not show any dependence on the composition. Tenacity showed a deviation from linearity due to the incompatibility.