Linear-Low Polyethylene Nanocomposite Fabrication Via Solid-State/ Melt Extrusion

Linear-Low Polyethylene Nanocomposite Fabrication via Solid-State/ Melt Extrusion

David A. Frey and Katsuyuki Wakabayashi

Department of Chemical Engineering

Bucknell University

Lewisburg, PA 17837

Combining a commercial polymer with an advanced filler material can yield a composite with a range of enhanced properties.  Nanocomposites have recently been of interest because the nano-scale of the filler can impart unique properties for very low loading percentage.  The production of these nanocomposites has been accomplished through several methods, but the knowledge about their differences is limited. 

The most common method in industry is twin-screw extrusion (TSE).  This method uses a heated extruder barrel to disperse the filler in a molten polymer matrix.  In contrast to this method, solid-state shear pulverization (SSSP) uses a chilled barrel to produce nanocomposites.  Shear and compressive forces pulverize and mix the two materials, yielding a powder product.  A recently developed process, solid-state/ melt extrusion (SSME), attempts to combine the benefits of both previous processes and uses a barrel split between cold and hot sections.

Due to the differences in nature of these processes, variations in the properties and performance of the resulting nanocomposite products are expected.  TSE is able to hold high production output while SSSP attempts to produce the most consistent and physically enhanced product throughout its powder producing processing.  SSME allows for an increase in production rate similar to TSE and emulates the pulverization section of the SSSP process.

This study compares the TSE, SSSP, and SSME processing on several model linear low-density polyethylene-based nanocomposites.  Various types of carbon-based fillers, namely graphite, carbon nanotubes, and carbon black, were employed as fillers to observe differences in the physical properties of the outputs.  Mechanical properties were determined via tensile-testing, while degradation behavior was examined via thermogravimetric analysis.  Interpreting these results leads to predictions about how different processing affects the morphology of nanocomposites.