Small-angle x-ray scattering (SAXS) and differential scattering calorimetry (DSC) were used to demonstrate distinct differences in domain size, phase separation, and hydrogen bonding in a series of segmented urethaneurea elastomers prepared from isocyanate-terminated prepolymers and aromatic diamine chain extenders. Two types of prepolymers were studied, the first exhibited a statistical distribution of high molecular weight oligomers and relatively high levels of free isocyanate monomer. The other type of prepolymer contained low levels of oligomer with greater than 90% of the two-to-one adduct of toluene diisocyanate (TDI) to polytetramethylene glycol (PTMEG). The residual unreacted diisocyanate was less than 0.1% in the second prepolymer. Two chain extenders, 4,4'-methylene bis-(2-chloroaniline)(Mboca) and 4,4'-methylene bis-(3-chloro-2,6-diethylaniline)(MCDEA) were evaluated. Materials prepared from the low oligomer prepolymers exhibited smaller hard segment domains with more ordered morphology, greater phase separation, and more hydrogen bonding than those with high oligomer content. These tendencies were enhanced in those elastomers chain extended with MCDEA compared to those chain extended with Mboca.
Citation: Journal of Polymer Science Part B-Polymer Physics
Pub Type: Journals
dsc, elastomer, mechanical properties, morphology, polyurethane, small-angle x-ray scattering