Improving the Supercritical CO₂ Foaming of Polypropylene by the Addition of Fluoroelastomer as a Nucleation Agent

Abstract

Polypropylene (PP) foam has a great deal of application since it normally exhibits non-uniform cell size distribution, low cell density, and cracked cells. In this study, a small amount of fluoroelastomer (FKM) was used as a nucleating agent to prepare well-defined microporous PP foam by supercritical CO2. It was observed that solid FKM was present as the nanoscale independent phase in PP matrix and the FKM could induce a mass of CO2 aggregation, which significantly enhanced the diffusion rate of CO2 in PP. The resultant PP/FKM foams exhibited much smaller cell size (～24 μm), and more than 16 times cell density (3.2×108 cells/cm3) as well as a much more uniform cell size distribution than that of the neat PP foam. PP/FKM foams possessed major concurrent enhancement in their tensile stress and compressive stress compared to neat PP foam. We believed that the added FKM played a key role in enhancing the heterogeneous nucleation, combined with the local strain field variation in the multiple-phase system, which was responsible for the considerably improved cell morphology of PP foaming. This paper provides a deep understanding of the scCO2 foaming behavior of PP in the presence of FKM.

Polyetherimide Foams Filled with Low Content of Graphene Nanoplatelets Prepared by scCO2 Dissolution

“…Furthermore, studies have suggested that the addition of nano-sized particles, such as carbon nanotubes and graphene, to foams prepared by CO 2 dissolution could improve cellular structure homogeneity, increase cell density, reduce cell size and, at the same time, reinforce the matrix [ 23 , 24 ].…”