ISSN:
0032-3888
Schlagwort(e):
Chemistry
;
Chemical Engineering
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
,
Maschinenbau
,
Physik
Notizen:
Most aromatic polyimides and copolyimides show a β relaxation process below their α relaxation processes in dynamic mechanical and dielectric measurements. The origin of this β relaxation has been under active discussion. In order to gain a better understanding of the origin of the β relaxation process, the dynamic mechanical behavior of a series of segmented rigid-rod polyimide and copolyimide films with different dianhydrides and diamines has been systematically studied. For some of the polymers, crystallinity and orientation effects on the β relaxation process were also investigated. It is found that the β relaxation process in the unoriented films can mainly be attributed to a relatively noncooperative motion in uncrystallized diamines. However, this noncooperative nature may be gradually lost by increasing the crystallinity and orientation. Molecular modeling and computation have led to a discussion of possible diamine motion in the β relaxation process.
Zusätzliches Material:
11 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/pen.760332102
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