Miscibility and crystallization have been studied for polypropylene-polyethylene and polyethylene-polyethyleneblends. In the case of the polypropylene blends the composition of interest is 20% polypropylene. At this composition thepolypropylene has been found to be soluble in linear low density polyethylene but insoluble in high

low and very lowdensity polyethylenes. The miscibility has been concluded from the crystallization kinetics and polarised optical microscopywith a hot stage. Polyethylene-polyethylene blends have been formed from polymers with similar average branching content but where they have different melting temperatures.Important consequences are to introduce long branches into a polyethylene taht only has short branches

and to modify the morphology of a polyethylenes so that haze

gloss and strain hardening are improved.Polyethylene blends must be developed after careful consideration of the branch content and distribution within each of the constituents.It is not sufficient to simply blend polyethylenes

with the desired range of properties

without regard to the miscibility of the blend composition.