Rheological Investigation of the Influence of Short Chain Branching and Mw of LDPE on the Melt Miscibility of LDPE/PP Blends

The influences of short chain branching (SCB) and molecular weight (Mw) of low density polyethylene (LDPE) on its melt miscibility with polypropylene (PP) were investigated by rheological techniques. Rheological meas- urement and different data-treatment techniques as well as rheological models suggest that blends of PP with LDPE of high SCB (22 CH3/1000 C) are miscible at all compositions. However, blends of LDPE with low SCB (8.3 CH3/1000 C) are immiscible in the LDPE-rich and miscible in PP-rich regimes. It was suggested that matching the conformations of PP and LDPE and matching the Mw of LDPE and PP is a key to the melt miscibility of PP/LDPE blends. The experimental results are in agreement with theoretical predictions on the miscibility of polyolefin blends.