Formulation of reactive inks for inkjet printing
Novel additive manufacturing processes are currently being focused in a variety of research fields. Digital inkjet printing produces small, uniformly-sized droplets that can be used as micro building blocks. In this way, spatially resolved structures of new, as well as known materials can be generated in an innovative way. For this reason, Fraunhofer IGB focuses its research on inkjet printing as a production tool for the individualization of production processes.
The combination of inkjet printing and the well-known polyurethane chemistry has great potential for future production of functional materials. At present, we are focusing on the production of polyurethane foams using two-component reactive inkjet printing. Two inks (an isocyanate-functional and, for example, a hydroxy-functional ink), each containing a reactive component, are printed separately in layers. The hydroxy-functional ink contains a polyethylene glycol (PEG) as the main carrier, combined with a crosslinker and catalysts. The second ink contains the pure isocyanate compound hexamethylene diisocyanate to obtain the porous polyurethane structure via a chemical reaction. For the first time, we were able to produce polyurethane foams without further mechanical mixing of the two reactive inks. By varying the inks, it is conceivable that spatially resolved differently-defined surface properties can be achieved in situ.