Rheological Behavior of Low-density Polyethylene (LDPE)- Polydimethylsiloxane Rubber (PDMS) Blends

Abstract

The rheological behavior of different blends of low-density polyethylene (LDPE) and polydimethylsiloxane rubber (PDMS) has been investigated at different temperatures (160, 180, and 200 C) and shear rates (61.3-613.1 s 1) with varying proportions of ethylene methylacrylate copolymer (EMA) and silica filler loading by using a Monsanto Processability Tester (MPT). The EMA copolymer is used as a chemical compatibilizer for the blend systems. The melt viscosity increases with the increase in the PDMS proportion and the filler loading but decreases with the increasing proportion of the EMA. The melts of all the blends are pseudoplastic in nature. The flow behavior index (n)of the blends decreases with the increase in the PDMS proportion and the silica filler loading but increases with the increase in the EMA proportion and the temperature. The activation energy of flow for the blends decreases with an increase in the PDMS proportion and the silica filler loading. But it decreases initially with an increasing proportion of EMA, reaches a minimum value at 6 wt% and then increases. The die swell increases with an increase in the shear rate but decreases continuously with an increase in the PDMS proportion and the silica filler loading. But it becomes the maximum at 6 wt% of EMA for the compatibilized blends. The phase morphology studied by Scanning Electron Microscopy (SEM) shows an improved dispersion for a 50/50 blend of LDPE-PDMS and it further improves with the incorporation of 6 wt% of EMA as well as the blend containing 10 wt% of silica filler loading. The surface finish of the extrudate for the blend containing 10 wt% of silica filler is better compared to that with 20 wt% of silica filler.