Phthalate-Free Plasticization of Electrostrictive P(VDF-TrFE-CTFE) for Enhanced Actuation

Area of Science:

• Materials Science
• Polymer Science
• Electromechanical Engineering

Background:

• Poly-(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) (P-(VDF-TrFE-CTFE)) based electroactive polymer (EAP) actuators are promising for soft robotics and wearable devices due to their large strains and compliance.
• Optimizing EAP properties, particularly electromechanical transduction, is crucial for expanding their application range.
• Phthalate-free plasticizers offer a safer alternative for modifying polymer properties.

Purpose of the Study:

• To investigate the impact of three phthalate-free plasticizers (BTHC, DINCH, TOTM) on the electromechanical transduction properties of P-(VDF-TrFE-CTFE) terpolymer.
• To quantify the improvements in field-induced strains and actuator deflections achieved through plasticizer blending.
• To explore the relationship between plasticizer concentration, film morphology, and actuator performance.

Main Methods:

• Thin films of P-(VDF-TrFE-CTFE) blended with varying concentrations of BTHC, DINCH, and TOTM were fabricated using stencil printing.
• Film morphology (SEM), crystallinity (XRD), and dielectric properties were analyzed.
• Unimorph actuators were constructed and characterized to measure field-induced transverse strains and tip deflections under varying electric fields and frequencies.

Main Results:

• Maximum strain increased by up to 12.5× in TOTM 10 wt % blends, reaching 1% at 33.2 V/μm.
• Largest tip deflections were observed with TOTM 5 wt % (246.6 μm at 0.1 Hz, 1.65 mm at resonance).
• Actuators with BTHC 15 wt % and TOTM 10 wt % showed 3.8× and 4× strain improvements, respectively, at 18 V/μm. DINCH 5 wt % and TOTM 5 wt % yielded 1.48× and 2.2× higher deflections.

Conclusions:

• Phthalate-free plasticizers, particularly TOTM and BTHC, significantly enhance electromechanical transduction in P-(VDF-TrFE-CTFE) electroactive polymer actuators.
• Plasticizer incorporation improves strain, deflection, and the breakdown field strength of the actuators.
• Further optimization of annealing processes, plasticizer concentrations, and reduction of film porosity can lead to even greater performance enhancements.