Capillary flow properties and dissolved state of segmented poly(urethane-urea)/N,N-dimethylacetamide solution as a function of temperature
✍ Scribed by Yasuhiro Nakano; Akiko Nakashima; Hiroyuki Hanahata; Kunihiko Okajima
- Book ID
- 104164413
- Publisher
- Elsevier Science
- Year
- 1997
- Tongue
- English
- Weight
- 1014 KB
- Volume
- 38
- Category
- Article
- ISSN
- 0032-3861
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✦ Synopsis
Capillary flow properties of a concentrated NJGdimethylacetamide (DMAc) solution of segmented poly(urethane-urea) (PUR) prepared from 4,4'-diphenylmethanediisocyanate (MDI), polytetramethlyleneoxide (PTMO), and ethylenediamine (EDA) (polymer concentration, 30.0wt%; hereafter referred to as 'PUR-solution') as well as the dissolved state was investigated as functions of solution temperature (T,,,) and shear rate (j): non-Newtonian index n in the equation r,, = k+-" decreased remarkably with increase in T,,, in the range more than about 90°C. The logarithmic shear viscosity (log 7]s) of the PUR-solution as a function of l/T,,,, gave two linear regions below and above 90°C suggesting that the activation energy of flow of the PUR-solution estimated in the Tsol range from 90 to 130°C (A E h) was higher than that (A El ) in the T,,, range of 40-80°C. The A E ,,--A El value was proved to become somewhat smaller as + increased, indicating that the shear stress might control the dissolved state of PUR to some extent but this contribution is much smaller than that by T,,,. 'H and 13C n.m.r. analysis on the dissolved states of PUR in the solution revealed existence of some hydrogen bondings mainly between N-H and C=O of urea groups, and suggested that the sudden decrease in n s of the PUR-solution at more than about 90°C is associated with a steep decrease in the average strength of the hydrogen bondings.