ISSN:
0025-116X
Schlagwort(e):
Chemistry
;
Polymer and Materials Science
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
,
Physik
Notizen:
The polymerization and crystallization of polyoxymethylene obtained by sublimation of trioxane (1,3,5-trioxane) and tetroxane (1,3,5,7-tetroxocane) crystals was investigated. Electron microscopy techniques and thermal analysis were used to characterize the polymer crystals as produced and after annealing. The polyoxymethylene crystals resulting from tetroxane show a regular lamellar folded chain macroconformation similar to those previously reported by polymerization of tetroxane crystals chemically initiated. The polymerization follows a crystallization succeeding polymerization mechanism. Trioxane gives mainly fibrous crystals, showing well oriented electron diffraction diagrams and higher melting points, consisting mostly of extended chains. A “pseudolamellar” morphology was also observed, being established by annealing, that the chain directions are parallel to the edges of the crystals. The strange growing habit seems to be produced by disruption of the electrical field of the trioxane crystals by a water effect. The polymerization seems to follow mainly a simultaneous polymerization and crystallization mechanism. The initiation of the polymerization is in both cases due to the gaseous formaldehyde formed during sublimation.
Zusätzliches Material:
1 Tab.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/macp.1979.021800315
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