Structural engineering of polyurethane coatings for high performance applications

Effect of the degree of soft and hard segment ordering on the morphology and mechanical behavior of semicrystalline segmented polyurethanes

Three types of amine-containing polyurethanes and poly(urethane−ureas), N-methyldiethanolamine (MDEA) and/or tetraethylenepentamine (TEPA) as the chain extender and poly(ethylene glycol) of MW 400 as the soft-segment component, have been studied by FTIR. The hydrogen bonding in hard and soft segments was examined for the extent of phase separation, and the microstructure was evidenced by differential scanning calorimetry (DSC). The temperature effects on the hydrogen bonding were also investigated. They show a significant amount of hydrogen bonding between the hard and soft segments. It indicates that there exists a large amount of partial phase mixing of hard and soft segments compared to the conventional polyurethanes. The bulky CH3 groups of MDEA in hard segments restrict the hydrogen bonding within the hard segments, while the TEPA-containing urethane−urea polymers have more distinct phase separation. However, all of the polymers studied are amorphous materials such that the dissolved soft segments in...

Fourier Transform Infrared Spectroscopy Study on Effects of Temperature on Hydrogen Bonding in Amine-Containing Polyurethanes and Poly(urethane−urea)s

FT-IR and XPS studies of polyurethane-urea-imide coatings

Two series of well-defined poly(urethane urea) multiblock copolymers were synthesized to investigate the phase-separated morphology of this family of materials. Series I copolymers were synthesized from 2000 g/mol poly(tetramethylene oxide) [PTMO], 4,4‘-methylene di(p-phenyl isocyanate) [MDI], and ethylenediamine (EDA), with hard segment contents ranging from 14 to 47 wt %. Series II copolymers (all with hard segment concentrations of 22 wt %) were prepared from the same PTMO and MDI and a diamine mixture of EDA and 1,4-diaminocyclohexane. The microdomain morphology was characterized using small-angle X-ray scattering, and the scattering data were analyzed using the approach of Bonart and Muller. The series I and II copolymers were found to have relatively low overall degrees of phase separation [ranging from ∼20% at the lowest hard segment contents to greater than 40%], contrary to the common notion that these copolymers are well phase separated materials. The introduction of the second diamine results i...

Microphase Separation of Segmented Poly(urethane urea) Block Copolymers

Model butanediol–MDI–polypropylene oxide polymers have been synthesized to explore the structure–property relationships in urethane/polyether polymers. The results of mechanical, thermal, and spectroscopic analyses agree remarkably well. The phase mixing in these polymers decreases with increasing hard-segment length, while the hard-segment stability increases with increasing hard-segment length. This is demonstrated clearly by dynamic mechanical, differential scanning calorimetry, infrared, and NMR studies. The importance of hydrogen bonding to the stability of the hard segment is strongly supported by the variable-temperature infrared experiments. The critical hard-segment size for phase segregation was shown to be two butanediols per hard segment. The temperature limit of the flatness of the storage modulus was tied to the thermal stability of the hard-segment hydrogen bonding which is controlled largely by the length of the hard segment and the extent of the hydrogen bonding.

Model MDI/butanediol polyurethanes: Molecular structure, morphology, physical and mechanical properties

Urethane elastomers consisting of 4,4'-methylene diisocyanate, 1,4-butanediol, and a 2000 molecular weight poly(oxypropylenediol) are examined. T 1 ρ c values were determined for the aromatic and butanediol carbons as a function of cross polarization field strength and temperature. The results for the aromatic carbons correlate well with observed high-temperature behavior of the elastomer as determined by dynamic mechanical spectroscopy. The biexponential decay of the butanediol resonances indicated that two types of motional populations can be associated with the phase-segregated portion of the hard segment

W. L. Howard

Papers

Model MDI/butanediol polyurethanes: Molecular structure, morphology, physical and mechanical properties

Solid-state carbon-13 NMR studies of model urethane elastomers