Work Hardening Effects in Gellan Gum Gels1
作者:
VictorJ. Morris,
Amalia Tsiami,
GeoffreyJ. Brownsey,
期刊:
Journal of Carbohydrate Chemistry
(Taylor Available online 1995)
卷期:
Volume 14,
issue 4-5
页码: 667-675
ISSN:0732-8303
年代: 1995
DOI:10.1080/07328309508005368
出版商: Taylor & Francis Group
数据来源: Taylor
摘要:
Gellan gum is a bacterial polysaccharide that is marketed as a broad spectrum gelling agent. The shear and Young's moduli, and the fracture strength of gellan gels increase with increasing ionic strength, pass through maxima and then decrease to zero at higher ionic strength. The position of the maxima depend on the valency of added counterions and are virtually independent of polymer concentration. At low ionic strength the measured rheological parameters show small variability but these values become increasingly variable with increasing ionic strength. Stress relaxation experiments were carried out in order to examine the mechanical behaviour of gellan gels and to explain these effects. At low ionic strength the gels approximate to elastic solids whereas at high ionic strength the increased stress relaxation is colloid-like in behaviour. However, unlike colloidal dispersions, the magnitude of the stress relaxation decreases on successive applications of stress and the relaxation modulus increases. The gels work harden. Such behaviour is attributed to a heterogeneous structure within the gel.
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