Visualization of CO2 Content Effect on Expansion Behaviour of HMS PP Extruded Foam

It is worthwhile to study the process ability of recyclable polypropylene for foaming applications. Due to the outstanding functional characteristics and low material costs, polypropylene (PP) foams have been considered as a promising substitute for other thermoplastic foams in industrial applications.This paper investigates the effect of blowing agent (CO2) on expansion behaviours of non-crosslinked high-melt-strength (HMS) polypropylene (PP) extruded foam. The shape of the extruded polypropylene foam at the die exit carefully monitored using a charge coupling device (CCD) camera. The expansion behaviour of HMS PP was observed and visualized by using varying amounts of supercritical carbon dioxide (CO2), varying amounts of talc and different die geometries. Experimental results indicated that as the gas content increased, the maximum expansion ratio did not always increase. Results also indicated that an optimum temperature exists for maximum expansion. In other word the expansion ratios of PP foams blown with CO2 exhibited mountain-shaped curves. However, this typical mountain-shaped expansion curves were not observed for some cases.

کلیدواژه ها:

Visualization ، Expansion behaviour ، PP foams ، Blowing agent ، CO2