Solidification and thermal degradation of printable, stretchable electrical conductor from waterborne polyurethane and silver flakes

In this study, we prepared high-performance printable, stretchable electrical conductor from waterborne polyurethane and micro-silver flakes. The solidification and thermal degradation were investigated using differential scanning calorimetry and thermogravimetric analysis methods. The electrical conductor achieved solidification by volatilizing and removing the free water. The thermal degradation mainly happened in the range of 250–450 °C caused by the pyrolysis of the polymeric matrix of polyurethane. The pyrolysis kinetic equations were obtained using the kinetic methods, e.g., dα/dt = e22.16(1 − α)0.78α0.13e(−149.14/RT) for the polyurethane, dα/dt = e22.76(1 − α)0.84α0.11e(−150.69/RT), dα/dt = e21.43(1 − α)0.77α0.06e(−143.77/RT), and dα/dt = e19.06(1 − α)0.75α0.12e(−130.53/RT) for the electrical conductor containing 80, 85, and 90 % mass percentage of micro-silver flakes, where α was the fractional extent conversion at a given time t (or a given temperature T). Their overall order of reaction was 0.91, 0.95, 0.83, and 0.87, respectively, less than 1, demonstrating the thermal degradation was a single, simple reaction.