| Abstract: | Two types of ultralow density polyethylene (ULDPE) of different melt viscosities were blended with a polypropylene (PP) in a twin screw extruder. Morphology, thermal, rheological, and mechanical properties of the blends were determined. Morphological observation from SEM showed a clean phase separation of PP/ULDPE blends. However, depending on the viscosity ratio, a significant difference in the extent of phase separation, as well as in the phase inversion composition, was demonstrated. The melting temperature of PP and ULDPE were respectively increased and decreased in the blend. Crystallization rate and the, crystallinity of PP and ULDPE were first increased and then decreased as the other component was increased. Yield at low frequencies was observed with 30 wt% ULDPE in PP. In ULDPE-rich compositions, complex viscosities of the blends gave negative deviation from the additive rule of mixing. Mechanical properties such as flexural modulus, elongation at break and Vicat softening point were closely relatable to the morphology. The impact strength of PP is significantly improved by ULDPE addition. |
