An experimental approach to evaluate drying kinetics and foam formation in inks for inkjet printing of fuel-cell layers

Inkjet printing is a deposition technique that has remarkably evolved over the last two decades, becoming widely employed for various applications. Notably, it has proven very promising for catalyst and ionomer layer deposition in assembling CCM (Catalyst Coated Membranes) of PEMFC (Polymer Electrolyte Membrane Fuel Cells). However, fast drying of the processed inks at the outlet often causes nozzle clogging and foam formation within the supply circuit often yields poor release: these are the main challenges in applying inkjet printing on a large scale. So, an experimental approach for the evaluation of drying kinetics and foam formation in inks typically employed in fuel-cell manufacturing is presented. It allows to evaluate ink printability, compare different inks quantitatively and assess the performance of commonly used additives. Evaluation of drying kinetics is based on releasing ink droplets onto a support, then recording mass, ambient temperature and relative humidity. Foam formation is evaluated by filling a syringe with a known amount of ink, then injecting air at a set flow rate into the sampling volume: foam may be ultimately generated and its amount can be measured. Those relatively simple approaches were applied to various inks; validation was conducted by statistical analysis and by comparison with physical relationships and datasets available in the open literature.