EXTENSIONAL RHEOLOGY: A TOOL TO PREDICT THE FOAMABILITY OF COMPLEX SYSTEMS SUCH AS POLYMER BLENDS AND RECYCLED POLYMERS

摘要

The goal of this work is to use extensional rheology as a tool to predict the foamability of polymeric complex systems. A methodology has been established to perform the rheological measurements and to analyze the strain hardening in conditions which are useful to interpret the foaming tests. This methodology pays attention to aspects such as the previous thermo-mechanical history of the polymer, the expected foaming temperature, the linear expansion ratio and the cells growth rate that depends on the foaming technology. Once the methodology has been established, two polymeric systems have been analyzed: high melt strength and linear polypropylene blends and pure and recycled polystyrenes. The foaming of these materials have been performed employing different technologies and also different foam densities have been achieved. The results show that, for the studied systems, a clear relationship between the strain hardening and the final cellular structure has been obtained, indicating that a good knowledge of the extensional behavior is fundamental in order to analyze and understand the final cellular structure of polymeric complex systems.