Effect of ultrasound on HDPE/clay nanocomposites: Rheology, structure and properties

High density polyethylene (HDPE)/organoclay nanocomposites of varying concentrations of clay were prepared by a single screw compounding extruder with the attached ultrasound die operating at various amplitudes. The die pressure and power consumption due to ultrasound were measured at different feed rates of nanocomposites of various clay concentrations. The structure and morphology of nanocomposites were studied by X-ray diffraction (XRD), transmission electron microscopy (TEM) and infrared spectroscopy. It was found that ultrasonic treatment enhanced the intercalation of HDPE into lattice layers of clay by increasing d-spacing up to 50%. Mechanical and rheological properties of these nanocomposites were investigated as a function of clay concentration and ultrasonic amplitude. Complex viscosity, storage and loss moduli of nanocomposites were increased after ultrasonic treatment. Mechanical properties such as the elongation at break, yield stress, toughness and impact strength of ultrasonically treated nanocomposites increased in comparison with the untreated nanocomposites. A reduction in oxygen permeability of nanocomposites was observed after ultrasonic treatment at an amplitude of 10 μm with the highest reduction by 20% at 2.5% clay concentration and a residence time of 21 s. This reduction in permeability was achieved even though results indicate that the crystallinity of ultrasonically treated nanocomposites was reduced.