Effect of water on the glass transition temperature of hydrophilic polyurethanes

Autor:	Nathaniel S. Schneider, Frank E. Karasz, Joyce L. Illinger
Rok vydání:	1993
Předmět:	Polymers and Plastics Ethylene oxide Chemistry Analytical chemistry Concentration effect General Chemistry Thermal expansion Surfaces Coatings and Films chemistry.chemical_compound Volume (thermodynamics) Polymer chemistry Materials Chemistry Copolymer Bound water Propylene oxide Glass transition
Zdroj:	Journal of Applied Polymer Science. 48:1723-1729
ISSN:	1097-4628 0021-8995
DOI:	10.1002/app.1993.070481005
Popis:	The depression of the glass transition temperature by water was studied in a set of polyurethanes in which the soft segment consisted of polyethylene oxide (sample I) or a block copolymer of poly(propylene oxide) terminated with poly(ethylene oxide) in various proportions (sample set II). DSC measurements were made at two added water contents for each type of sample and at various temperatures. The Tg reduction appeared to be governed solely by the nonfreezing bound water and was much larger in sample I than in samples of set II. The more limited effect on the Tg of set II samples is attributed to restricted mobility arising from coupling of the short terminal poly(ethylene oxide) to rigid hard-segment units. Therefore, the data for sample I are preferred as a test of the predictive relations for the Tg depression. On this basis, it appears that the simple Fox mixing equation is more reliable than is the available free volume approach, which required unrealistically high values of the thermal expansion coefficient for water to fit the data for sample I. © 1993 John Wiley & Sons, Inc.
Databáze:	OpenAIRE
Externí odkaz:	https://explore.openaire.eu/search/publication?articleId=doi_________::2ba3fe16ad8e7ca9b6f83a7f7462fdce https://doi.org/10.1002/app.1993.070481005 Zobrazit plný text záznamu Plný text