Conductivity Behaviour under Pressure of Copper Micro-Additive/Polyurethane Composites (Experiment and Modelling)

Area of Science:

• Materials Science
• Polymer Science
• Electrical Engineering

Background:

• Polymer-metal composites offer tunable electrical properties.
• Understanding conductivity mechanisms under external stimuli is crucial for advanced materials.

Purpose of the Study:

• To investigate the pressure-dependent conductivity of copper-polyurethane (PU) composites.
• To explore the pressure-induced percolation transition phenomenon (PIPT).
• To validate numerical simulation methods for predicting composite conductivity.

Main Methods:

• Fabrication of PU-Cu composite films using solution mixing and spin-coating.
• Experimental measurement of in-plane and through-thickness conductivity under varying pressure (1-20 kPa).
• Numerical modeling using a semi-analytical percolation model and finite element method (FEM) based on representative volume element (RVE) models.

Main Results:

• Conductivity changes were observed only in the through-thickness (z-direction) under pressure.
• Significant conductivity (up to 7.2 x 10^-1 S·m^-1) was induced by pressure in composites with >2.6 vol.% Cu.
• Percolation threshold concentrations decreased with increasing pressure, confirming PIPT.
• FEM simulations accurately predicted conductivity and percolation threshold.

Conclusions:

• Applied pressure effectively reduces polymer film thickness, enhancing inter-particle contact and conductivity.
• The study demonstrates the potential of FE-RVE simulations for predicting the electrical behavior of polymer-metal composites under pressure.
• This approach can reduce experimental costs and time for developing functional materials.