Polymer processing for neat and modified polymer

Polymeric films are realized via the solution casting method. The first step consists of dissolving the terpolymer P(VDF-TrFE-CFE) powder in 2-butanone solvent (also known as methyl-ethyl-ketone) at 25%wt. Monomeric composition of terpolymer is 62.2% for VDF, 29.4% for TrFE, and 8.4% for CFE expressed as molar fraction. The polymeric dissolution prepared in this manner is then casted on glass plate using a calibrated casting-knife to obtain polymer film with a thickness of approximately 55 µm ± 1 µm. Subsequently, casted films are heated up at 70 °C for 1 h to ensure complete solvent removal. Films are then peeled off and placed on polytetrafluoroethylene (PTFE) foils, and thermal annealing at 102 °C is performed to promote crystallinity¹³. The annealing temperature was chosen as the onset of the melting peak for the second melting of terpolymer powder that was determined via DSC.

To further improve the electromechanical performances of electrostrictive P(VDF-TrFE-CFE) terpolymer, modified polymeric films are realized by blending P(VDF-TrFE-CFE) terpolymer with 10%wt of a phthalate plasticizer¹⁴, which was performed at the first step during terpolymer dissolution. The addition of DINP plasticizer was chosen because of its biocompatibility as well as its ability to substantially enhance electromechanical coupling of the terpolymer¹⁰. The pure and modified EAPs were then subjected to high-energy β-irradiation at 50 kGy, which is a standard sterilization dose for medical instruments (according to industrial process of IONISOS). A comparison between the pristine and the sterilized samples in terms of thermal/electrical/electromechanical performance will be investigated in section III.