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

• Main Authors: Chenguang Yang, Quan Zhao, Zhe Xing, Wenli Zhang, Maojiang Zhang, Hairong Tan, Jixiang Wang, Guozhong Wu
• Format: Article
• Language: English
• Published: MDPI AG 2019-02-01
• Series: Polymers
• Subjects: polypropylene; fluoelastomer; scCO₂ foaming; heterogeneous nucleation
• Online Access: https://www.mdpi.com/2073-4360/11/2/226
• ISSN: 2073-4360

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.