Rheological Properties of Thermoplastic Polymers with Dissolved Gases for Foaming Applications

Understanding the concept of rheology in polymer melts with dissolved gases like CO2 is crucial in development of high quality polymer foams which are commonly manufactured by foam extrusion processes. The crystallization and rheological properties of the melt are significantly affected by the dissolved gas, which acts as a blowing agent and at the same time as a plasticizer. Moreover, the rheological properties of gas-loaded polymer melts influence on the efficient design of extrusion dies toward production of popular homogenous lightweight foams. This chapter will discuss common methods to measure these rheological properties with the example of a long-chain branched Polypropylene as a case study. To take into account the role of crystallization behavior under gas-loading into the process design, we describe a method to measure both rheology and crystallization in one experimental setup.