Thermoplastic Polyurethane Hydrolysis Stability

Abstract

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.

Kinetics of Hydrolytic Aging of Polyester Urethane Elastomers

“…Qualitative analysis [5] showed that the polyester urethanes contained 1,4-butarediol, p,p' diphenylmethane diisocyanate, and either an adipate or caprolactone polyester. Infrared spectra showed no bands attributable to carbodiimides, which have been used to stabilize polyester urethanes to moisture (4]. Weight fractions of diisocyanate were calculated from the nitrogen contents, which were determined in duplicate by a commercial laboratory.…”

“…More reliable tests based on specific molecular mechanisms are therefore desirable for critical uses of these materials. Schollenberger and Stewart showed that the degradation involved the acid catalyzed hydrolysis of the ester linkage [4].…”

Crystallinity in Hydrolytically Aged Polyester Polyurethane Elastomers

“…Consequently, aged and unaged polyether types show the same relative moduli at 25 and 600 C. , Larger acid numbers in the polyester diol from which the polyurethane is made increase the degradation rate of the polyurethane [5]. Polyester polyurethanes can also be attacked by fungi [2].…”

Solvent free synthesis and structural evaluation of polyurethane films based on poly(ethylene glycol) and poly(caprolactone)

“…Other compositions containing PCL did not show complete decomposition even over a period of one year. The expected bonds that undergo hydrolysis are ester and urethane ones, where esters are expected to be most unstable [16,26]. Sample PU PEG contained from the two mentioned only urethane ones and those are expected to be hydrolyzed yielding shorter PU chains.…”