Effect of Nano-Particles on Cellular Structure of Foamed PP-HDPE Blend Using Supercritical Fluid

Microcellular foaming of general polypropylene (PP) is a hot subject, but there are some difficulties in its foaming due to its low melt strength, narrow foaming temperature window, and so on. This work attempted to the improvement of PP microcellular foaming by adding nano-montmorillonite and nano-calcium carbonate into PP-high-density polyethylene (HDPE) blend. The nanocomposites were prepared using a twin-screw extruder. The foaming was carried out by a batch process with supercritical carbon dioxide as a blowing agent. Microstructure of the nanocomposites was examined using transmission electron microscopy. The cellular structure of foams was examined using a scanning electron microscope. The effects of nano-particle concentration and type on the cellular structure, cell density, cell diameter, and sample density were investigated. The results showed that the main factor controlling the cellular structure of foamed nanocomposites is the distribution of nano-particles.