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

## TL;DR

This paper explores using phthalate-free plasticizers to improve the performance of a type of polymer used in soft robotics and medical devices.

## Contribution

The study introduces phthalate-free plasticizers that significantly enhance the actuation performance of P(VDF−TrFE−CTFE) terpolymer films.

## Key findings

- TOTM 10 wt% blends increased maximum strain 12.5× over the neat terpolymer, reaching 1% at 33.2 V/μm.
- TOTM 5 wt% blends achieved the largest tip deflections of 246.6 μm at 0.1 Hz and 1.65 mm at resonance.
- DINCH- and TOTM-based actuators withstood 60% higher electric fields than the neat terpolymer.

## Abstract

PVDF-based electroactive
polymer (EAP) actuators offer large field-induced
strains, high compliance, and simple and scalable processing, enabling
novel applications in soft robots, wearable devices, and medical devices.
This work investigates how blending the poly­(vinylidene fluoride−trifluoroethylene−chlorotrifluoroethylene)
[P­(VDF−TrFE−CTFE)] terpolymer with three phthalate-free
plasticizers (butyryl trihexyl citrate (BTHC), 1,2-cyclohexanedicarboxylic
acid diisononyl ester (DINCH), and tris­(2-ethylhexyl) trimellitate
(TOTM)) affects the electromechanical transduction properties. Thin
films of plasticizer/terpolymer blends were obtained via stencil printing.
Film morphology (SEM), crystallinity (XRD), and mechanical and dielectric
properties were investigated at different plasticizer contents, and
unimorph actuators were fabricated and characterized to quantify the
field-induced transverse strains. The maximum strain increased by
12.5× over the neat terpolymer in TOTM 10 wt % blends, reaching
1% at 33.2 V/μm. The largest tip deflections were achieved with
TOTM 5 wt %, giving 246.6 μm at 0.1 Hz and 1.65 mm at resonance
(33.7 V/μm). At a fixed field of 18 V/μm, blends with
BTHC 15 wt % and TOTM 10 wt % produced 3.8 and 4× strain improvements,
while DINCH 5 wt % and TOTM 5 wt % delivered 1.48 and 2.2× higher
deflections. DINCH- and TOTM-based actuators withstood at least 60%
higher fields than the neat terpolymer, likely due to plasticizer
diffusion into the EAP film pores. These results show that the studied
plasticizers can enhance transduction in P­(VDF−TrFE−CTFE),
with further improvements expected by reducing film porosity, establishing
optimal annealing processes and plasticizer concentrations.