Optical and thermal studies of starch/methylcellulose blends

Starch and methylcellulose (MC) homopolymers and their blends were prepared using a casting technique. The samples were investigated by infrared (Fourier transform infrared (IR)), ultraviolet/visible (UV/VIS), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Significant changes in IR spectra of blend samples were observed, which indicated the occurrence of an intermolecular interactions between starch and MC. UV/VIS analyses revealed that the values of the optical band gap decreased with increasing MC content in blend samples. The positions of the investigated samples on the chromaticity diagram and the color parameters, such as L*, U*, V*, C*, h(ue) and Y-e, reflected the presence of a high color gradient and were composition dependent. A single glass transition temperature for each poly-blend sample was observed, which supported the existence of compatibility in such a system. The kinetic thermodynamic parameters, such as activation energy, enthalpy, entropy and Gibbs free energy, were evaluated from thermogravimetric analysis data using the Coats-Redfern relation.