Affiliation:
1. Department of Fiber and Polymer Technology Polymeric Materials Division School of Engineering Sciences in Chemistry Biotechnology and Health KTH Royal Institute of Technology Stockholm 10044 Sweden
2. Deutsches Elektronen‐Synchrotron DESY Notkestraße 85 D‐22607 Hamburg Germany
3. Department of Plant Breeding Swedish University of Agricultural Sciences P.O. Box 190 Lomma SE‐234 22 Sweden
Abstract
AbstractHygroscopic biopolymers like proteins and polysaccharides suffer from humidity‐dependent mechanical properties. Because humidity can vary significantly over the year, or even within a day, these polymers will not generally have stable properties during their lifetimes. On wheat gluten, a model highly hygroscopic biopolymer material, it is observed that larger/thicker samples can be significantly more mechanically stable than thinner samples. It is shown here that this is due to slow water diffusion, which, in turn, is due to the rigid polymer structure caused by the double‐bond character of the peptide bond, the many bulky peptide side groups, and the hydrogen bond network. More than a year is required to reach complete moisture saturation (≈10 wt.%) in a 1 cm thick plate of glycerol‐plasticized wheat gluten, whereas this process takes only one day for a 0.5 mm thick plate. The overall moisture uptake is also retarded by swelling‐induced mechanical effects. Hence, hygroscopic biopolymers are better suited for larger/thicker products, where the moisture‐induced changes in mechanical properties are smeared out over time, to the extent that the product remains sufficiently tough over climate changes, for example, throughout the course of a year.
Subject
Materials Chemistry,Polymers and Plastics,Organic Chemistry,General Chemical Engineering
Cited by
2 articles.
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