ISSN:
0021-8995
Schlagwort(e):
Chemistry
;
Polymer and Materials Science
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
,
Maschinenbau
,
Physik
Notizen:
Thermal analysis, solvent sorption, density measurement, and X-ray diffraction techniques were used to investigate structural changes in a variety of PVC compounds which were extruded or compression-molded at temperatures in the range 150-220°C. In all cases processing at lower temperatures in this range resulted in a disappearance of primary crystallinity and a concomitant development of secondary crystallinity, of lower order. In many cases processing above 190-200°C caused a small increase in crystallinity. It is believed that this is more ordered secondary crystallinity, which is therefore detectable by X-ray diffraction and also capable of influencing density and solvent sorption behavior. The observed structural behavior depends on shear as well as temperature. Primary crystallinity is higher in compression moldings, which have experienced lower shear levels, and the increase in crystallinity at higher temperatures is also greater. Equilibrium solvent sorption depends on the presence of primary and ordered secondary crystallinity. Diffusion is, however, unaffected as it occurs through amorphous and disordered crystalline regions only.
Zusätzliches Material:
10 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/app.1989.070370622
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