3 years ago

Tuning the properties of segmented polyhydroxyurethanes via chain extender structure

Tuning the properties of segmented polyhydroxyurethanes via chain extender structure
John M. Torkelson, Junho Jeon, William H. Heath, Goliath Beniah
The influence of chain extender structure on the properties of segmented polyhydroxyurethane (PHU) was investigated with four diamine molecules: 1,4-diaminobutane, isophorone diamine, methylene bis(cyclohexyl amine), and bis(aminomethyl) norbornane. These nonisocyanate polyurethanes were synthesized with polytetramethylene oxide-based soft segment and divinyl benzene dicyclocarbonate (DVBDCC) as hard segment. They were characterized with small-angle X-ray scattering (SAXS), dynamic mechanical analysis (DMA), and tensile testing. All PHUs possess nanophase-separated morphology with interdomain spacings of 12 to 16 nm via SAXS. DMA shows that the nanophase separation is accompanied with broad interphases having a wide range of local compositions. These PHUs exhibit tan δ ≥ 0.30 over broad temperature ranges, indicating their potential as effective damping materials. The flow temperature (Tflow), the temperature range with tan δ ≥ 0.30, and the tensile properties of these PHUs are strongly affected by the molecular structure of the chain extender used in synthesis. At 50 wt % hard-segment content, values of Tflow, tensile strength, and elongation-at-break can be tuned via chain extender from 57 to 105 °C, 1.6 to 22.4 MPa, and 70 to 500%, respectively. Notably, PHU at 50 wt % hard-segment content, synthesized with norbornane-based chain extender exhibits the best thermal and mechanical properties with Tflow of 105 °C, tensile strength of 22.4 MPa, elongation-at-break of 500%, and tan δ ≥ 0.30 over 74 °C in breadth. By varying hard-segment content between 30 and 50 wt %, norbornane-based PHUs afford broad tunability in tensile strength from 0.5 to 22.4 MPa with tan δ ≥ 0.30 spanning temperature range as large as 85 °C. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44942.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/app.44942

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