Influence of glycerol content on the electrical properties of potato starch films

Effects of glycerol (G) and temperature (T) on the electrical properties of potato starch (PS) films were investigated by impedance spectroscopy measurements in the radio frequency range (20 Hz–3 MHz). The membranes were prepared by a solution casting method with weight fraction glycerol/potato starch (G/PS) = 0.1, 0.3, and 0.5 and characterized by DSC, FTIR, and moisture content measurements. The dc‐conductivity ( σ 0 ) of all compositions increases with the glycerol concentration and temperature, reaching the value of 5.2 × 10 −5 /Scm at 423 K, for G/PS = 0.5. The real part of the conductivity shows power–law frequency dependence ( f n , n ≈ 0.98) at frequencies higher than a crossover frequency ( f p ). The imaginary part of the electric modulus plots shows non‐Debye asymmetrical peaks at about the frequency f p and it is characterized by a “stretched” exponential parameter β ≈ 0.8. The temperature dependence of σ 0 , f p (both showing an Arrhenius‐type behavior) and DSC data shows a phase boundary at about 353 K for all compositions. Results are discussed in terms of correlation effects in ion motion that takes place in a separate second phase in the G/PS films with composition G/H 2 O.