Viscoelastic behavior of highly filled HDPE/wood flour composites

Dynamic and steady shear viscoelastic properties of highly filled (50-70%) HDPE/Wood flour composites have been investigated by parallel-plate and capillary rheometers. The concentration effect of a new lubricant and coupling agent on the melt rheological properties of the composites was explored as well. The results showed that addition of both lubricant and coupling agent to the 70% filled HDPE composite considerably improved its flow behavior. An increase in the complex viscosity and storage modulus of the wood filled systems at low concentration of both modifiers was observed in case of 50% filler loading. Higher concentrations of modifiers resulted in a decrease of the complex viscosity. In capillary flow, it was observed that the lubricant improved the processability to a great extent. It was also found that all wood filled composites did not obey the Cox-Merz rule. It was concluded that dynamic and steady shear viscosity measurements by parallel plate rheometer did not correspond to capillary measurements at elevated wood flour loadings.