Due to its outstanding properties, ultraviolet (UV) ink is currently a major ink type used in 3D inkjet printing applications and additive manufacturing (AM) in general. However, there exists a major challenge which has to be addressed and overcome, namely the agglomeration issue, which can potentially lead to nozzle clogging. To understand the underlying physics and chemistry of the agglomeration phenomenon, numerical characterisation provides a low-cost high resolution solution, if the correct numerical methodology is appropriately exploited. F or this meso-scale agglomeration problem, dissipative particle dynamics (DPD) is a highly suitable simulation technique, and in this preliminary study, the commercial solver Material Studio 8.0 from Accelrys Inc is utilized. Here, the coarse-grained models are generated by directly coarse-grained from the atomistic model. Commercial UV inks used in AM applications today are usually composed of oligomers, monomers, photo-initiators, pigments, and other additives such as stabilizers and surfactants. Among these components. oligomers have the highest tendency to agglomerate, which can agitate the stability and quality of the printing fluid, and possibly lead to nozzle clogging. Specifically we study and examine the morphological characteristics of an UV ink composing of photopolymers of polystyrene (PS) and polyethylene glycol (PEG) as the main components in the simulation model. In this case, styrene is chosen as it is one of the most prevalent commercial photopolymers in present 3D inkjet applications, while ethylene glycol is a photopolymers known to improve ink viscosity. The preliminary results for different models considered show that the kind of photopolymers and their constituent ratios affect the agglomeration morphology of the system, and the existence of both oligomers and monomers results in mutual morphological benefits against agglomeration. The results also reveal the importance of other additives in the ink composition to prevent, reduce and control various forms of agglomeration to achieve enhanced print quality.ASTAR (Agency for Sci., Tech. and Research, S’pore)Published versio
