ISSN:
0021-8995
Schlagwort(e):
Chemistry
;
Polymer and Materials Science
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
,
Maschinenbau
,
Physik
Notizen:
The influence of annealing on the supermolecular structure of commercial, thermostable fibers, spun from solutions of poly(p-phenylene-1,3,4-oxadiazole) (POD) in H2SO4, is examined. The crystalline α-modification of thermally treated POD fibers has an orthorhombic unit-cell probably of space group P212121. The symmetry of the single POD chain in these crystallites is 21. The unit-cell dimensions are a = 1.235 nm, b = 0.655 nm, c = 1.40···1.47 nm, where c depends on the annealing temperature Ta. The unit cell contains 4 chains of two monomers each. Annealing up to Ta of about 755 K causes increases in crystallite size, crystalline orientation, and linear degree of order, combined with an improved axial Young's modulus E. Thermal degradation at higher temperatures leads to the breaking of tie molecules in general, while UV-radiation selectively damages tie molecules that are not taut.
Zusätzliches Material:
3 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/app.1992.070460610
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