SUMMARY:This paper reviews several types of thermoplastic polyurethane elastomers, and the unique properties these polymers have. I n discussing the hydrolysis stability of thermoplastic polyurethane elastomers the suitability of these polymers for such study was pointed out. A relationship between poly(ester-urethane) composition in terms of methylene group concentration, hardness and chain stiffness, and hydrolysis stability was shown. The dominant role of polyurethane acid number in thermoplastic poly(est,er-urethane) hydrolysis stability was demonstrated and the origin of this unexpected acid number was discussed. The pronounced stabilizing action of added poly(carbodiimide) in thermoplastic poly(ester-urethane) hydrolysis was shown, as well as the severe destabilizing act.ion of a carboxylic acid, stearic acid. The hydrolysis st,abilities of thermoplastic poly(ester-urethane) elastomers based on poly(s-caprolactone) glycol and on poly(hexamethy1ene carbonate) glycol were also described. ZUSAMMENFASSUNG :Die Hydrolysestabilitat einiger thermoplastischer Poly(ester-urethan)-Elastomerer in Abhangigkeit vom molekularen Aufbau wird untersucht. Entscheidend fur den hydrolytischen Abbau dieser Polymeren ist das Auftreten von Carboxylgruppen. Es werden Moglichkeiten aufgezeigt, diesen Abbau zu verringern, $3 z . B. durch Zusatz von Poly(carbodiimiden). AbschlieBend werden die Hydrolyaestabilitat von thermoplastischen Poly(ester-urethan)-Elastomeren untersucht, die Poly-( E Caprolacton) und Poly(hexamethy1encarbonat) als Glykolkomponente enthalten.

Front dynamics in the frontal polymerization of two multifunctional acrylate monomers, 1,6-hexanediol diacrylate (HDDA) and trimethylolpropane ethoxylate triacrylate (TMPTA), with Lupersol 231 [1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane] as the initiator, are studied. In most frontal polymerization systems, the dynamics are associated with a planar front propagating through the sample. However, in some cases, front behavior can be altered: the front becomes nonplanar characterized by complex patterns like spin modes and pulsations. To determine how these periodic and aperiodic modes arise, reactant solutions consisting of HDDA diluted with diethyl phthalate (DEP) and TMPTA diluted with dimethyl sulfoxide (DMSO) were used in the study. In the study we reveal frontal behavior characteristic of period-doubling behavior, a doubling of spin heads that degenerate into an apparently chaotic mode. Also, a pulsating symmetric mode has been observed. These observations have a striking similarity to observations made in studies of self-propagating high-temperature synthesis (SHS) in which the addition of an inert diluent afforded a rich variety of dynamical behavior. The degree of cross-linking has also been found to be a bifurcation parameter. The energy of activation of multifunctional acrylate polymerization is a strong function of the degree of polymerization. By adding a monoacrylate (benzyl acrylate: BzAc), such that the front temperature was invariant, we observed a period-doubling bifurcation sequence through changes in the energy of activation, which has not been previously reported. (c) 1999 American Institute of Physics.

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This paper reviews several types of thermoplastic polyurethane elastomers, and the unique properties these polymers have. In discussing the hydrolysis stability of thermoplastic polyurethane elastomers the suitability of these polymers for such study was pointed out. A relationship between poly(ester‐urethane) composition in terms of methylene group concentration, hardness and chain stiffness, and hydrolysis stability was shown. The dominant role of polyurethane acid number in thermoplastic poly(ester‐urethane) hydrolysis stability was demonstrated and the origin of this unexpected acid number was discussed. The pronounced stabilizing action of added poly(carbodiimide) in thermoplastic poly(ester‐urethane) hydrolysis was shown, as well as the severe destabilizing action of a carboxylic acid, stearic acid. The hydrolysis stabilities of thermoplastic poly(ester‐urethane) elastomers based on poly(ϵ‐caprolactone) glycol and on poly(hexamethylene carbonate) glycol were also described.