Rheological Studies on Glycerol Plasticized Gelatin and Its Blends with Epoxidized Soybean Oil

Blends of gelatin (Ge) plasticized with varying amounts of glycerol (Gly), buffer solution pH 10 and epoxidized soybean oil (ESO) to enhance hydrophobicity were prepared by mixing and injection-molding. Blends were characterized by rheological tests and microscopy to select optimal conditions for scaling up their processing. The effect of each component on rheological response was analyzed using parallel plate geometry. Coating of gelatin specimens with PDMS during rheological tests led to reliable and reproducible results since water evaporation was prevented. A gradual increment in ESO concentration led to blends with increased degree of phase separation, as evidenced by optical and confocal microscopy. Limited compatibility between ESO and Ge increased viscosity at high ESO levels, but up to 10% Gly could be replaced with ESO without a significant variation of rheological behavior.