Improving the Supercritical CO(2) Foaming of Polypropylene by the Addition of Fluoroelastomer as a Nucleation Agent

In this study, a small amount of fluoroelastomer (FKM) was used as a nucleating agent to prepare well-defined microporous PP foam by supercritical CO(2). It was observed that solid FKM was present as the nanoscale independent phase in PP matrix and the FKM could induce a mass of CO(2) aggregation, which significantly enhanced the diffusion rate of CO(2) in PP. The resultant PP/FKM foams exhibited much smaller cell size (~24 μm), and more than 16 times cell density (3.2 × 10(8) cells/cm(3)) as well as a much more uniform cell size distribution. PP/FKM foams possessed major concurrent enhancement in their tensile stress and compressive stress compared to neat PP foam. We believe that the added FKM played a key role in enhancing the heterogeneous nucleation, combined with the change of local strain in the multiple-phase system, which was responsible for the considerably improved cell morphology of PP foaming. This work provides a deep understanding of the scCO(2) foaming behavior of PP in the presence of FKM.