ISSN:
0032-3888
Keywords:
Chemistry
;
Chemical Engineering
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
Pulsed nuclear magnetic resonance measurements have shown that segmented polyurethanes as well as block copolymers segregate into domains with distinct mobilities. The usefulness of this technique for investigating the importance of the domain interface and for studying the mixing/ demixing of domains has been demonstrated. By examining the percent rigid material as a function of temperature, a polystyrene/butadiene block copolymer showed little evidence of domain interface effects, while in a series of segmented polyurethanes, the interface was seen to be important. The domains of a polyester soft segment and diphenylmethane diisocyanate hard segment polyurethane were mixed by annealing at 170°C. Examination of the demixing process as a function of storage temperature enabled an activation energy for domain formation of 36 ± 5 kcal/mole to be calculated. In a series of polyurethanes with varying amounts of hard segments, the material with the least amount of hard segments showed evidence of soft segment crystallinity. The mixing proces in this series was interpreted in terms of shifting correlation frequency distributions.
Additional Material:
10 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pen.760170818
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