Microcrystal Particles Behaviour in Inkjet Printing of Reactive Nylon Materials

A novel process using inkjet printing of molten materials to produce nylon 6 for additive layer manufacturing applications was investigated. Different reactive mixtures of molten caprolactam with activator and catalyst were characterized for physical properties to understand their jettability in an inkjet system. Although it was found that the surface tension and viscosity of all materials were within the range suitable for inkjet technology according to the literature, microcrystals of undissolved salt of the catalyst complex (caprolactam magnesium bromide) were found to influence melt supply behavior. The influence of the process on the catalyst microcrystal consistency and agglomeration beyond the jetting system was investigated for purged, deposited multiple droplets and also individual droplet samples using hot-stage polarized light microscopy. Quantitative image analysis showed that although microcrystal agglomeration occurred within the accumulated droplets due to kinetics of droplet impact, this however was much less than with the purged samples. A generally consistent content and dispersion of the microcrystals existed within the consecutively deposited droplets.