Methylcellulose-Based Edible Films and Coatings: 2. Mechanical and Thermal Properties as a Function of Plasticizer Content

Several edible films based on methylcellulose and polyethylene glycol 400 (PEG400) were prepared and stored until equilibration at different relative humidities. Tensile stress−strain curves show very different behaviors as a function of PEG400 and relative humidity. Tensile strength strongly depends on relative humidity and then on water content, more than on PEG400 content. On the contrary, elongation is dependent both on water and PEG400. These differences correspond to the glass transition of the polymer, which affects the elongation more than the tensile strength. However, from DSC measurements, it appears that the PEG400 has no or a very low compatibility with the methylcellulose matrix.