Doctor of Philosophy Polymers, colloquially referred to as plastics, are used as the materials to generate foams like the sole of a tennis shoe or the Styrofoam coffee cup on your desk. Currently, these materials are made using environmentally damaging and potentially health hazardous chemicals that are gradually being phased out by global regulations. Producing polymer foams, or foaming, using compressed carbon dioxide is a more environmentally favorable process to generate porous or "foamed" materials. It is crucial to understand how the polymer behaves in a high-pressure environment with gases such as carbon dioxide to manufacture these materials. Several unique instruments were developed to understand polymer behavior in carbon dioxide, allowing for insights into polymer material behavior at high pressure. This information can then be translated into selecting temperature, pressure, and saturation conditions from which to generate polymer foams. The polymers of interest are rubbers that display elastic behavior like a classic rubber band. They are of interest in athletic equipment, tennis shoes, or other areas where repetitive compression and recovery properties are essential. In the first part of this study blending of two polymer systems was explored to see how blending alters foaming outcomes. In the second part, foaming was explored in relationship to the material behavior of the polymer in the presence of carbon dioxide. Specifically, this part involves the study of foaming near the melting transition, which is the transition where the polymer material loses its ordered structure. Studying foaming outcomes near the melting transition allows rational windows for foaming exploration to be evaluated to generate foams that display more favorable bulk foam densities and minimal foam collapse. The third part explores the foaming of polymers with carbon dioxide under batch confined foaming conditions where the foam expansion is restricted to control the foaming outcomes again and prevent foam collapse. A practical question is the scale-up of batch foaming processes which likely will be conducted with injection molding or extrusion type processes. Studying batch foaming in confinement allows for a better understanding of the factors that may affect foam development that may be more readily translated to industrial practice. The fourth part examines a series of polymers that display different degrees of elasticity. This study allows for understanding how elasticity may impact foaming outcomes like the collapse observed after the foam is generated.