Slit die rheology of HDPE and ABS based wood plastic composites

by 1980- Chastagner, Matthew Wayne

Chair: Michael P. Wolcott by Matthew Wayne Chastagner, M.S. Washington State University August 2005 As the use of wood plastic composite materials has continued to increase, the research into the rheology of these materials has taken a back seat to the characterization of the mechanical properties. However, for an accurate determination of the mechanical properties to occur, an understanding of the rheological behavior of the melt is needed, since changes in the melt can directly affect the final product properties. A rheological slit die was used to quantify the shear viscosity, shear stress and extruder motor current for acrylonitrile-butadiene-styrene (ABS)/ and high-density polyethylene (HDPE)/wood filled melts. Using a Carreau curve fit, the viscosity results indicate that there is a significant increase in the melt viscosity as the wood filler amount increased. In HDPE melts, when the wood filler size and wood species changed, there was little observed change in the viscosity. With the ABS based melts, when the temperature of the melt increased, the shear viscosity of the melt decreased. This change in melt temperature was then used to create master curves by reducing the viscosity and shear rate. Since the shifting factors used to create the master curves followed an Arrhenius curve fit, the melt activation energy of the ABS melts was also determined. In both the ABS and HDPE melts, the melt shear stress increased as the temperature decreased and the wood filler content increased. Similar trends were observed when the required motor current load iv was analyzed for the HDPE melts, but there was more variation in the data as compared to the observed shear stress and viscosity results. v