PHASE SEGREGATION IN MELTS OF BLENDS OF LINEAR AND BRANCHED POLYETHYLENE

A linear polyethylene (LPE) has been blended with a branched polyethylene (BPE) in a range of concentrations. Using several experimental methods in combination, the full phase diagram for this polymer pair has been mapped out. In particular, the polymers are shown to be conditionally miscible in the melt; the melt segregated region occurs at low LPE content and is of a closed loop shape. It is, however, impossible to reach parts of the region due to crystallization. Considerable co-crystallization takes place whenever any of the blends are crystallized isothermally; crystals commonly include LPE and BPE in the ratio 6:4 and in an extreme case have been found to contain LPE to BPE in the ratio 1:3. Attention is drawn to the wide range of morphologies (and, by implication, properties) which can be obtained from this system.