2.4. Rheological measurement of FFS The rheological properties of FFS were performed on a Haake Rheostress 6000 rheometer(Thermo Scientific Instruments, Inc. Germany) fitted with a cone-plate geometry(diameter 25 mm angle- with a gap of 0.104 mm. Dynamic oscillatory mea surements were carried out in the linear viscoelasticity range(LVR) Storage modulus(G') and the loss modulus(G") were recorded in the 0.1-100 rad/s angular frequency sweep at a strain ampli- tude of 0.2% (in the LVR). The apparent viscosity as a function of the shear rate was determined in the range from 0.1 to 300 s 1 Samples were individually loaded on the measuring geometry and allowed to stand for 2 min prior to testing. All measurements were performed at 25 t 0.1 C and performed in triplicate. 2.5. Film analysis