An improved technique for dispersion of natural graphite particles in thermoplastic polyurethane by sub-critical gas-assisted processing

摘要

Dispersing fillers uniformly is the main technological challenge when considering nanocomposites. In this paper, a novel and efficient sub-critical gas-assisted processing (SGAP) technique is explored-an environmentally benign process that utilizes compressed CO2 to help effectively disperse aggregated natural graphite particles (NGPs) (3 wt%) in a thermoplastic polyurethane (TPU) matrix. A twin-screw extruder (TSE) equipped with a simple CO2 injection unit consisting of a standard gas cylinder, regulator, valve, and metal hose is employed for the melt mixing. Results from the structural, thermal, rheological, mechanical, microcellular injection molding, dielectric, and thermal conductive properties of the SGAP pellets, in addition to the resultant TPU/NGP nano composites, confirmed significantly improved dispersion compared to those obtained via conventional melt blending in the TSE. This technique offers a simple, cost-effective approach to the large-scale production of high-performance polymer nanocomposites without the requirement for complicated processing steps such as supercritical fluid (SCF) processes or chemical treatments.