ISSN:
0887-6266
Keywords:
rubber crystallinity
;
plasticizers
;
syneresis
;
NMR
;
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
We prepared polycaprolactone networks plasticized (60 wt%) with triacetin, with and without filler particles to model high-energy solid rocket propellants. Under strain and at lower temperatures these materials partially crystallize but also undesirably exude plasticizer (syneresis). We measured both properties isothermally (30°C) on the basis of molecular mobility: crystallinity with rapid-passage cw proton nuclear magnetic resonance (NMR), and syneresis with pulsed-gradient spin-echo NMR diffusion techniques, as a function of strain and time. In the gumstocks crystallinity and syneresis increase monotonically with strain and asymptotically with time. In a given specimen syneresis lags behind crystallinity but they approach the same value, suggesting that syneresis originates in expulsion of plasticizer from crystallizing regions. In the composites, crystallinity results resemble those in gum, but our diffusion data suggest that most syneresis is internal, with plasticizer accumulating in strain-debonded void regions near filler particles. © 1994 John Wiley & Sons, Inc.
Additional Material:
7 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/polb.1994.090320805
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