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THE ROLE OF DOUBLE-HELIX FORMATION IN WATER DIFFUSION AND AGING OF INJECTION-MOLDED STARCH*

Authors :
Fernando Ania
M. E. Cagiao
S. Lindemann
M. Dunkel
R. K. Bayer
Source :
Journal of Macromolecular Science, Part B. 40:733-747
Publication Year :
2001
Publisher :
Informa UK Limited, 2001.

Abstract

Native potato starch has been processed without the use of any additive. Moldings of initial high strength and ductility have been achieved. However, mechanical properties change with time. Thermogravimetric experiments at different temperatures show that aging takes place in three different steps. The first is characterized by a strong formation of double helices (as revealed by wide-angle X-ray scattering [WAXS]) in parallel with strong water loss. Hardness, strength, and elongation at break increase in this time range: Double helices act as reinforcing elements. When the yield elongation is surpassed, double helices are unraveled, providing a higher elongation at break. With further aging (drying), due to a shrinking process, a temporary reduction of double helices, causing a resoftening, seems to take place. In a third step, the starch moldings become quite brittle due to the lack of molecular mobility. At room conditions, it takes approximately 1 year (beginning of range 3) to lose the good mechanica...

Details

ISSN :
1525609X and 00222348
Volume :
40
Database :
OpenAIRE
Journal :
Journal of Macromolecular Science, Part B
Accession number :
edsair.doi...........294d2277c8d063f956280e64ef9f70ba
Full Text :
https://doi.org/10.1081/mb-100107558