  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.
