Development of urea-urethane-based binary inks for reactive material jetting system

Reactive material jetting utilizes droplets of reactive inks which cure on mixing. In this study, the process is carried out by in-air collision and coalescence of the jetted droplets and subsequent deposition of a combined droplet onto the build surface. Thereby, precise volumes of droplets can be mixed ensuring stoichiometric proportions to produce and pattern materials in a single step. A series of reactive inks based on urea/urethane systems were developed. Materials with different properties were obtained ranging from tough (E = 107 MPa, U = 14 MPa, ε(U) = 33 %) to brittle (E = 47 MPa, U = 4.4 MPa, ε(U) = 9.2 %) and to elastic (E = 12 MPa, U = 5.6 MPa, ε(U) = 915 %) (E = 24 MPa, U = 4.0, ε(U) = 350 %). Obtained data were correlated with multilinear equations or group contribution models. The best fitting was obtained for a group contribution model based on the produced material molar group contributions. The obtained data were discussed based on the fitted model. This simple model shows good interpolation agreement, indicating that it could be used to predict compositions of reactive inks to produce materials of desired properties.