STRUCTURE-PROPERTY RELATIONSHIPS IN ANNEALED BLENDS OF LINEAR LOW-DENSITY POLYETHYLENE WITH ISOTACTIC POLYPROPYLENE

Blends of isotactic polypropylene (PP) and linear low density polyethy lene (LLDPE) have been analysed by thermal analysis and wide-angle X-r ay scattering to determine the effect of thermal history on morphology and mechanical behaviour. The blends were quenched directly from the melt, slow cooled and annealed at 130-degrees-C. In all cases it was o bserved that the two components were insoluble and the crystallization behaviour was determined by the blend morphology, particularly in dis persed PP domains in which heterogeneous nucleation was the rate deter mining step. Slow cooled specimens with the higher degree of crystalli nity had the highest yield stresses, and the lowest elongation to brea k was achieved in the vicinity of 50% blends, characteristic of the ef fect of blend morphology on properties.