Rheology of Low-Density Polyethylene plus Boehmite Composites

Polyethylene is already one of the most commonly used polymers due to its solvent resistance and easy processing. Low-density polyethylene (LDPE) also has excellent flexibility and resilience. However, the mechanical properties of LDPE are often poor. We added the inexpensive ceramic filler Boehmite to LDPE, simultaneously improving mechanical properties and reducing production cost as Boehmite is cheap and abundant while the filler reduces the amount of petroleum-derived polymer per unit weights of product. Additionally, less environmental contamination results at the end of service life since the Boehmite need not undergo degradation as the LOPE does. To aid adhesion between the matrix and filler, we introduced silane coupling agents (SCAs) to bond the hydrophobic LDPE to the hydrophilic Boehmite. Furthermore, since fillers ordinarily increase viscosity, it was essential to maintain a low viscosity for easy processability. We evaluated by rheometry the effect of the Boehmite on the melt viscosity of the LDPE Boehmite composites and determined that the addition of any type of Boehmite decreases the viscosity compared to that of neat LDPE. The effects were explained by fiber formation and enhanced rigidity while the allowance for a lower processing temperature results in further energy and therefore cost savings. We also show that high-temperature exposure of Boehmite during any part of the sample processing results in a decrease in the coupling efficiency of the matrix to filler and in a higher melt viscosity; yet the viscosity is still lower than for neat LOPE. POLYM. COMPOS., 31:1909-1913, 2010. (C) 2010 Society of Plastics Engineers