Abstract
Thermomechanical and NMR methods have been used to investigate the influence of “free” chains on the molecular mobility and structure of crosslinked polyester urethane elastomers. The temperature dependences of the spin-spin and spin-lattice relaxation times have been obtained for the polymers in the interval from +60 to −60°, and their glass transition temperatures have been determined by both methods. An analysis of the free induction decay has been carried out for specimens of varied compositions at different temperatures. It is shown that the free induction decay for crosslinked polyurethanes by a single exponent A( t) ∼exp(− βt) or by the sum of such exponents, or by an exponent of the type of A( t) ∼exp(− αt 2), depending on the composition and temperature of the polymer in question. Apparently the analysis of free induction decay provides a basis for estimating the extent to which micro regions having nonuniform molecular mobilities are present in polyurethanes.
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