  Syntactic foams have found widespread usage in various applications
including, marine, aerospace, automotive, pipe insulation, electrical cable
sheathing, and shoe insoles. However, syntactic foams are often exposed to
moisture when used in these applications that potentially alter their
viscoelastic properties, which influences their long-term durability. Despite
their significance, previous research has mainly focused on experimental
studies concerning mechanical property changes resulting from filler loading
and different matrix materials, overlooking the fundamental mechanisms
resulting from moisture exposure. The current paper aims to bridge this gap in
knowledge by elucidating the impact of long-term moisture exposure on TPU and
TPU-based syntactic foam through multi-scale materials characterization
approaches. Here, we choose a flexible syntactic foam manufactured using
thermoplastic polyurethane elastomer (TPU) reinforced with glass microballoons
(GMB) through selective laser sintering. Specifically, the research
investigates the influence of moisture exposure time and the volume fraction of
GMB on chemical and microphase morphological changes, along with their
associated mechanisms. The study further examines how these microphase
morphological changes manifest in viscoelastic properties.
