In this study, the synthesis, structure and physical properties of two series
of thermoplastic polyurethanes based on hydroxypropyl terminated
poly(dimethylsiloxane) (HP-PDMS) or hydroxyethoxy propyl terminated
poly(dimethylsiloxane) (EO-PDMS) as a soft segment, and
4,4?-methylenediphenyl diisocyanate and 1,4-butanediol as a hard segment were
investigated. Each series is composed of samples prepared with a different
soft segment. The polyurethanes were synthesized by two-step polyaddition in
solution. The effects of the type and content of PDMS segments on the
structure, thermal and surface properties of copolymers were studied by 1H
NMR, 13C NMR and two-dimensional NMR (HMBC and ROESY) spectroscopy, GPC, DSC,
TGA, WAXS, SEM, water contact angle and water absorption measurements.
Thermal properties investigated by DSC indicated that the presence of soft
PDMS segments lowers the glass transition and melting temperatures of the
hard phase as well as the degree of crystallinity. SEM analysis of copolymers
with a lower soft segment content confirmed the presence of spherulite
superstructures, which arise from the crystallization of the hard segments.
When compared with polyurethanes prepared from HP-PDMS, copolymers
synthesized from EO-PDMS with the same content of the soft segments have
higher degree of crystallinity, better thermal stability and less hydrophobic
surface. Our results show that the synthesized polyurethanes have good
thermal and surface properties, which could be further modified by changing
the type or content of the soft segments.
Structural and Viscoelastic Properties of Thermoplastic Polyurethanes Containing Mixed Soft Segments with Potential Application as Pressure Sensitive Adhesives
