Effect of processing methods on the electrical conductivity properties of silver-polyurethane composite films (Experimental and numerical studies)

Abstract

This research investigates the electrical properties of micro silver polyurethane (Ag-PU) composite films with different degrees of agglomeration. Ag-PU composite films were prepared by adding micro silver particles (<3.5 μm) into the thermoplastic PU matrix using a solution mixing method, followed by spin-coating or casting techniques. For some composite preparation, the silver solution was shear-mixed in an ultrasonic bath before being added to the PU solution to obtain higher filler dispersion within the polymer matrix. This method produced several composite films with variable degrees of silver aggregation with concentrations from 0 to 14 vol%. All composites showed only electrical conductivity through thickness when compressed under pressure in a range from 0.5 to 20 kPa. Generally, the percolation threshold and conductivity values of the composite film prepared by spin-coating were lower than those of the casting composite. The maximum conductivity value found in these composites was about 2.45 S/m. All composites’ electrical performance was numerically simulated using the finite element analysis method based on the representative volume element model (FE-RVE) with Digimat software. A correlation was observed between the experiments and those simulations. A semi-analytical model was used to estimate the composite electrical parameters.