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Assessing viscoelastic properties of chitosan scaffolds and validation with cyclical tests

Paper ID Volume ID Publish Year Pages File Format Full-Text
1229 79 2012 10 PDF Available
Title
Assessing viscoelastic properties of chitosan scaffolds and validation with cyclical tests
Abstract

We evaluated and modeled the viscoelastic characteristics of chitosan and chitosan–gelatin scaffolds prepared using a freeze-drying technique. Chitosan and chitosan–gelatin solutions (0.5 and 2 wt.%) were frozen at −80 °C and freeze-dried. Using the scaffolds, uniaxial tensile properties were evaluated under physiological conditions (hydrated in phosphate buffered saline at 37 °C) at a cross-head speed of 0.17 mm s−1 (10 mm min−1). From the break strain, the limit of strain per ramp was calculated to be 5% and the samples were stretched at a strain rate of 2.5% s−1. The ramp-and-hold type of stress-relaxation test was performed for five successive stages. Chitosan and chitosan–gelatin showed nearly 90% relaxation of stress after each stage. The relaxation behavior was independent of the concentration of chitosan and gelatin. Also, changes in the microstructure of the tested samples were evaluated using an inverted microscope. The micrographs acquired after relaxation experiments showed orientation of pores, suggesting the retention of the stretched state even after many hours of relaxation. Based on these observations, two models (i) containing a hyper-elastic spring (containing two parameters) and (ii) retaining pseudo-components (containing three parameters) were developed in Visual Basic Applications accessed through MS Excel. The models were used to fit the experimental stress-relaxation data and the parameters obtained from modeling were used to predict their respective cyclic behaviors, which were compared with cyclical experimental results. These results showed that the model could be used to predict the cyclical behavior under the tested strain rates. The model predictions were also tested using cyclic properties at a lower strain rate of 0.0867% s−1 (5% min−1) for 0.5 wt.% scaffolds but the model could not predict cyclical behavior at a very slow rate. In summary, the pseudo-component modeling approach can be used to model the sequential strain-and-hold stage and predict cyclical properties for the same strain rate.

Keywords
Chitosan; Scaffolds; Stress relaxation; Cyclical property; Time constant
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Publisher
Database: Elsevier - ScienceDirect
Journal: Acta Biomaterialia - Volume 8, Issue 4, April 2012, Pages 1566–1575
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us