Abstract
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. 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 scCO2 foaming behavior of PP in the presence of FKM.
Highlights
As a widely investigated commercial polymer, polypropylene (PP) foam has numerous desirable and beneficial properties, such as good chemical-resistance, outstanding mechanical properties, low electrical conductivity, low cost and a unique porous honeycomb structure [1,2,3,4]
It was found that nano-materials such as carbon nanotubes, carbon nanofibers, and graphene added in PP could enhance heterogeneous nucleation to increase cell density, reduce cell
Microcellular PP foam with fine cellular structure was fabricated in the presence
Summary
As a widely investigated commercial polymer, polypropylene (PP) foam has numerous desirable and beneficial properties, such as good chemical-resistance, outstanding mechanical properties, low electrical conductivity, low cost and a unique porous honeycomb structure [1,2,3,4]. PP foams have wide range of many industrial applications in the fields of packaging, aerospace, automobiles, acoustic absorbent, dielectric materials, energy storage materials, thermal insulators, as well as tissue engineering [1,2,5,6,7,8,9]. Due to their very low melt strength and high crystallinity, the fabrication of linear PP foams is not successful [10,11,12,13]. To improve the melt strength, considerable efforts have been made to optimize the process of PP foaming, enhance PP foam ability as well as improve cellular structure [12,14,15,16,17,18,19], such as long-chain branching, crosslinking [11,16,20,21], polymer blending [12,22], and compounding [23,24].
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