Foaming Poly(methyl methacrylate) with an Equilibrium Mixture of Carbon Dioxide and Isopropanol

In this study we examine the mixture carbon dioxide (CO2) and 2-propanol (PrOH) as foaming agents for poly(methyl methacrylate). Gaseous CO2 was dissolved in liquid PrOH, allowing for injection of a homogenous liquid mixture into the extruder. The advantage of such a system is that the CO2/PrOH ratio remains stable, and the mixture can easily be metered with a suitable pump. While the PMMA foamed with this equilibrium mixture was similar to foams prepared with separately injected CO2 and PrOH, there appears to be synergistic effects on the plasticization of PMMA. Furthermore, a delay in the onset of cell nucleation for the PFA mixtures in which CO2 was the main component was also observed.