Peroxide modified polyolefin blends: Part I. Effects on ldpe/pp blends with components of similar initial viscosities

As part of a broader research effort to prepare polyolefin blends with controlled rheological and mechanical behavior, LDPE/PP blends were peroxide modified through reactive processing in intensive batch mixers. Polymers with similar initial viscosities and elasticities were first melt mixed and then simultaneously reacted and mixed to produce blends whose reaction‐modified components had very different molecular weights and molecular weight distributions. The rheological behavior of the blends in both shear and elongational flow were found to depend on composition, peroxide concentration, and, possibly, on the relative response rate of the individual components to peroxide attack. In general, the rheological properties of the reacted blends differed significantly from those of blends compounded in the absence of peroxide, and they were influenced by the presence of two components with vastly different structural and rheological characteristics: the degraded PP of low viscosity and elasticity, and a branched or crosslinked LDPE with increased viscosity and increased melt elasticity. Data from the batch experiments of this work are useful in defining process requirements for continuous reactive extrusion compounding, such as component characteristics, length of mixing/reaction zones, screw geometry, and sequence of feeding, as they relate to product characteristics.