In this work, we investigated the microphase separation, mechanical, and
dynamic mechanical properties of thermoplastic polyurethane elastomers (TPUs)
with one-soft segment (polypropylene glycol, PPG, or hydroxyl-terminated polybutadiene,
HTPB) or bi-soft segment (PPG and HTPB) using FTIR, XRD, SAXS
and amplitude modulated-frequency modulated viscoelastic mode of AFM (AMFM
mode AFM) methods. The results showed that the microphase separation
process of hard and soft segments (HS and SS) in TPU containing PPG and HTPB
soft segments (PPG-HTPB-PU) was restricted by randomly alternated bi-soft segments,
which results in formation of a low content of irregular-shaped hard
domain (HD). In addition, the microphase separation of PPG-HTPB-PU induced
a triple-phased structure of HD, HTPB rich phase and mesophase. The mesophase
of PPG-HTPB-PU was formed of HS, PPG and HTPB segments which were
excluded out of HD and HPTB rich domains during microphase separation process.
The damping temperature range (at tan δ greater than 0.3) of PPG-HTPB-PU
was from ?14.6 to 32.1C (46.5C) which was more broad than that of TPU containing
HTPB soft segment (HTPB-PU). The broad damping temperature range of
PPG-HTPB-PU is mainly attributed to the enhanced energy consumption caused
by the frictional motions of mixed segments of mesophase.
