Thermomechanical properties of biodegradable films based on blends of gelatin and poly(vinyl alcohol)
- 作者：Oscar Mendieta-Taboada ; Paulo José ; do A. Sobral ; Rosemary A. Carvalho ; Ana Mô ; nica B.Q. Habitante
- 关键词：Protein ; Biopolymer ; Differential scanning calorimetry ; Dynamic-mechanical analysis ; Glass transition ; Viscoelastic properties
- 刊名：Food Hydrocolloids
- 出版年：2008
- 期刊代码：37_0268005x
- 类别：ch
- 出版时间：December 2008
- 卷：22
- 期：8
- 页码：1485-1492
- 文件大小：594 K
摘要
The aim of this work was to study the effect of the poly(vinyl alcohol) (PVA) concentration on the thermal and viscoelastic properties of films based on blends of gelatin and PVA using differential scanning calorimetry (DSC) and dynamic-mechanical analysis (DMA). One glass transition was observed between 43 and 49 °C on the DSC curves obtained in the first scanning of the blended films, followed by fusion of the crystalline portion between 116 and 134 °C. However, the DMA results showed that only the films with 10%PVA had a single peak in the tan <i>δi> spectrum. However, when the PVA concentration was increased the dynamic mechanical spectra showed two peaks on the tan <i>δi> curves, indicating two <i>Ti>gs. Despite this phase separation behavior the Gordon and Taylor model was successfully applied to correlate <i>Ti>g as a function of film composition, thus determining <i>ki>=7.47. In the DMA frequency tests, the DMA spectra showed that the storage modulus values decreased with increasing temperature. The master curves for the PVA–gelatin films were obtained applying the TTS principle (<i>Ti>r=100 °C). The WLF model was thus applied allowing for the determination of the constants <i>Ci>1 and <i>Ci>2. The values of these constants increased with increasing PVA concentrations in the blend: <i>Ci>1=49–66 and <i>Ci>2=463–480. These values were used to calculate the fractional free volume of the films at the <i>Ti>g and the thermal expansion coefficient of the films above the <i>Ti>g.