The Spreading of Inkjet-Printed Droplets with Varying Polymer Molar Mass on a Dry Solid Substrate

An experimental study on the spreading of inkjet printed droplets of a polystyrene/toluene solution with varied molar masses on solid dry surfaces is presented. The polymer's number-averaged molar mass was varied between 1.5 and 545 kDa, which also caused a variation in the viscosity from 0.6 to 1.7 mPa . s. The results were compared with theoretical models for droplet spreading and were found to fit with an error between 2 and 20% with the predictions. Furthermore, the in-flight evaporation of the free-falling droplet was investigated for polystyrene/toluene solutions that have a constant vapor pressure by printing from a systematically increased height.