Effect of moisture absorption on the thermal properties of Bombyx mori silk fibroin films

✍ Scribed by N. Agarwal; D. A. Hoagland; R. J. Farris

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 190 KB
• Volume: 63
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/(sici)1097-4628(19970118)63:3<401::aid-app17>3.0.co;2-2

✦ Synopsis

Films of regenerated Bombyx mori silk are strongly affected by absorbed moisture, a phenomenon studied here by differential scanning calorimetry (DSC). Exposure of previously dried films to environments of controlled relative humidity produces test samples of well-defined equilibrium moisture content. Ultimate moisture uptake is as high as 20-23% (by weight) at 75% relative humidity. The glass transition temperature, T g , drops by 40ЊC at moisture uptakes as low as 2%, and T g depressions as large as 140ЊC are observed at higher relative humidity. The moisture-induced decrease of T g is completely reversible, as a film remoistened and then redried possesses an unchanged T g . Trends in T g with water uptake correspond reasonably well to predictions of a classical thermodynamic theory, indicating that the plasticization effect of moisture on the combined silk-water system can be satisfactorily explained from macroscopic properties of the constituents without any reference to specific interactions.