Manufacturing of micro-scale polyurethane foams by reactive inkjet printing

Reactive inkjet printing (RIJ) was used as an additive manufacturing (AM) tool. Combined with polyurethane (PU) chemistry, it is shown that RIJ can be used to build micro-scale foams. Waterblown polyurethane foams (PUF) based on polyethylene glycol 200 (PEG200), glycerol ethoxylate (Star-PEG) and 1,6-hexamethylene diisocyanate (HDI) were used to prepare the foams. The system was catalyzed using iron(III) chloride, dibutyltin dilaurate (DBTL), diazabicyclo octane (DABCO) and bis(2-dimethylaminoethyl) ether. The influence of iron(III) chloride and DBTL were investigated by means of temperature profile measurements. The stability of the catalyst system was tested for 32 hours within the ink formulation. The ink formulations were then printed with a Dimatix DMP3000 (Fujifilm, USA) printer using a 16 nozzle printhead with a nominal 10 pL drop volume. The reaction of the inks and the building of PUF after printing were investigated by light microscopy and SEM. It seems favorable to use high amounts of catalyst in order to obtain a more porous structure.