Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8328428 | International Journal of Biological Macromolecules | 2018 | 5 Pages |
Abstract
The aim of this study was to evaluate the effect of plasticisers with different molecular weights (glycerol and sorbitol) on the structural relaxation kinetics of bovine gelatine films stored under the glass transition temperature (Tg). Plasticisers were tested at weight fractions of 0.0, 0.06 and 0.10. Films conditioned in environments under â¼44% relative humidity gave moisture contents (w/w) in the range 0.14-0.18. The enthalpy relaxation (ÎH) was determined using differential scanning calorimetry (DSC). Samples used had Tg values in the range 24-49â¯Â°C. After removing the thermal history (30â¯Â°C above Tg, 15â¯min), samples were isothermally stored at 10â¯Â°C below Tg for between 2 and 80â¯h. The addition of plasticisers induced a significant reduction in the rate of structural relaxation. The linearisation of ÎH by plotting against the logarithm of ageing time showed a reduction in the slope of samples plasticised with both polyols. The reduction in relaxation kinetics may be related to the ability of polyols to act as enhancers of molecular packing, as recently reported using positron spectroscopy (PALS). However, a direct correlation between the relaxation kinetics and the plasticiser's molecular weight could not be established, suggesting that this phenomenon may be governed by complex molecular gelatin-plasticiser-water interactions.
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Authors
Paulo DÃaz-Calderón, Bill MacNaughtan, Sandra Hill, John Mitchell, Javier Enrione,