Novel thermoplastic polyhydroxyurethane elastomers as effective damping materials over broad temperature ranges

Abstract

a b s t r a c tNon-isocyanate thermoplastic polyhydroxyurethane (PHU) elastomers were synthesized from cyclic carbonate aminolysis using polytetramethylene oxide (PTMO) as soft segment and divinylbenzene dicyclocarbonate and three diamine chain extenders as hard segment with a range of hard-segment content. Characterization was done via Fourier transform infrared spectroscopy, small-angle X-ray scattering (SAXS), uniaxial tensile testing, and dynamic mechanical analysis (DMA). SAXS reveals that these PHUs possess nanophaseseparated morphology with 10-20 nm interdomain spacings. These PHUs display elastomeric response and tunable tensile properties with Young's modulus ranging from 27 to 200 MPa, tensile strength from 0.3 to 9.7 MPa and elongation at break ranging up to greater than 2000%. DMA reveals that nanophase separation in these PHUs is accompanied by broad interphases having a wide range of local composition; this nanophase separation differs significantly from that manifested by thermoplastic polyurethane elastomer (TPU) due to hydrogen bonding of hydroxyl groups in the hard segments to the PTMO soft segment. These PHUs show very good damping performance with tan d P 0.30 over broad temperature ranges (P60°C), which are tunable through simple variation of hardsegment content and chain extender structures.

Tuning the properties of segmented polyhydroxyurethanes via chain extender structure

“…Most previous PHU studies have focused on the synthesis of cyclic carbonate monomers and their subsequent polymerization into single‐phase thermoplastics or crosslinked thermosets, or on catalysis of the cyclic carbonate aminolysis reaction . Few studies have investigated segmented, nanophase‐separated PHU and established an understanding of their structure–property relationships . Leitsch et al .…”

Non-isocyanate polyurethane/epoxy hybrid materials with different and controlled architectures prepared from a CO2-sourced monomer and epoxy via an environmentally-friendly route

“…The M n values vary with altered the amine ratio and amine type. The molecular mass of NIPU from ringopening reaction between cyclic carbonate and amine has been reported by many groups, [38][39][40] and low M n value is not completely resolved. One possible reason should be side reactions due to the high reaction temperature and mole ratio of the reactants.…”

Functionalization of hydroxyl groups in segmented polyhydroxyurethane eliminates nanophase separation

“…The T flow of PHU‐Ac is at least 50 °C below that of PHU‐O. The DMA results for PHU‐Ac reflect the characteristic of single‐phase polymeric material and show that hydroxyl group functionalization with an acetyl group results in loss of nanophase separation despite the absence of hydroxyl groups which participate significantly in intersegmental hydrogen bonding in PTMO‐based PHU . Thus, although elimination of intersegmental hydrogen bonding in PHU by using polybutadiene‐based soft segment leads to excellent nanophase separation with narrow interphase, the elimination of hydroxyl groups necessary for such intersegmental hydrogen bonding in PTMO‐based PHU by functionalization with acetic anhydride results in the loss of nanophase separation itself.…”

“…PHU‐O was synthesized according to the procedure outlined in ref. . Acetylation of PHU‐O to yield PHU‐Ac follows a similar procedure detailed in ref.…”

“…Providing steric hindrance to the oxygen atom via polypropylene oxide (PPO)‐based soft segment and dilution of oxygen atom content via polytetramethylene oxide (PTMO)‐based soft segment yield nanophase‐separated PHUs with elastomeric‐like properties at appropriate hard‐segment content. The nanophase separation in PTMO‐based PHU is accompanied with broad interphase, which is due to a significant level of intersegmental hydrogen bonding between the hydroxyl groups to the soft segment . When a soft segment with no potential for intersegmental hydrogen bonding is used, such as polybutadiene‐based soft segment, nanophase‐separated PHUs with a much sharper domain interphase like that exhibited by conventional thermoplastic PU elastomer are obtained .…”