Dynamic self generation of hydrogen bonding and relaxation of polymer chain segment in stabilizing thermoplastic polyurethane microcellular foams. (September 2020)

• Record Type: Journal Article
• Authors: Lan, Bin; Li, Pengzhi; Yang, Qi; Gong, Pengjian
• Is Part Of: Materials today communications. Volume 24(2020)
• Publication Date: 2020-09
• Subjects: Thermoplastic polyurethane -- Supercritical CO2 foaming -- Cell stabilization; Materials science -- Periodicals; 620.11
• DOI: 10.1016/j.mtcomm.2020.101056
• Languages: English
• ISSNs: 2352-4928

Abstract

Graphical abstract: Highlights: This is the first report of focusing specially on the molecular mechanism of TPU foams' cell stabilization. TPU scCO2 foams' cell stabilization has been clarified at macromolecular scale using in-situ characterization techniques. Self-generation of hydrogen bonding and relaxation of polymer chain segment play significant roles on cell stabilization. Strategies from macromolecular viewpoint were proposed for thermoplastic elastomer foams' cell stabilization. Abstract: Cell stabilization of TPU foams made from supercritical CO2 (scCO2 ) foaming remains a huge challenge and significantly limits TPU foams' applications. One key point is the absence of molecular mechanism during TPU foam shrinkage and not to mention the solution. In this work, the interactions within/among TPU macromolecular chain(s) are investigated in-depth via several in-situ characterization methods, hence clarified the molecular mechanism during TPU foam shrinkage and uncovers the direction to achieve cell stabilization. It is revealed that dynamical self-generation of hydrogen bonding and polymer chain segments' relaxation after foaming play significant roles in cell stabilization. Base on this molecular mechanism, strategies of strengthening and accelerating hydrogen bonding, inducing another primary bonding besides hydrogen bonding among molecular chains, fixing hard segments while relaxing soft segments are proposed. Consequently, this work guides the direction to produce thermoplastic elastomer foams of large expansion ratio with less shrinkage via scCO2 foaming.