# Synthesis and Characteristic Valuation of a Thermoplastic Polyurethane Electrode Binder for In-Mold Coating

## TL;DR

This paper introduces a new thermoplastic polyurethane electrode binder with strong mechanical and electrical properties suitable for in-mold coating applications.

## Contribution

A novel thermoplastic polyurethane binder is synthesized and validated for use in stretchable electrode applications.

## Key findings

- The PHEI-PU series showed a tensile strength of 44.71 MPa and 190% elongation at break.
- The electrical resistance change rate remained below 20% even after stretching.
- SEM confirmed well-dispersed silver flakes in the coating layer after deformation.

## Abstract

A polyurethane series (PHEI-PU) was prepared via a one-shot bulk polymerization method using hexamethylene diisocyanate (HDI), polycarbonate diol (PCD), and isosorbide derivatives (ISBD) as chain extenders. The mechanical properties were evaluated using a universal testing machine (UTM), and the thermal properties were evaluated using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The PHEI-PU series exhibited excellent mechanical properties with an average tensile strength of 44.71 MPa and an elongation at break of 190%. To verify the applicability of different proportions of PU as an electrode binder, PU and Ag flakes were mixed (30/70 wt%) and coated on PCT substrates, the electrodes were evaluated by four-point probe before and after 50% elongation, and the dispersion was evaluated by scanning electron microscopy (SEM). The electrical resistance change rate of PHEI-PU series was less than 20%, and a coating layer with well-dispersed silver flakes was confirmed even after stretching. Therefore, it exhibited excellent physical properties, heat resistance, and electrical resistance change rate, confirming its applicability as an electrode binder for in-mold coating.