About the project
The core technology to be developed in the project is reactive inkjet printing as a technology to enable the additive manufacturing of novel thermoset composites based on epoxy-polyamine resins. The technology will allow not only for printing parts of complex shape without the need for casting or subsequent processing, but also the control of the microstructure. We will pioneer heterogeneous epoxies, composed from hard and soft microscale subdomains, with contrast and spatial distribution, which will be designed by modelling such to enhance the overall material toughness, without compromising its strength and modulus. Functionalized nanoparticles will be introduced at specific sites to either produce reinforcement or to enhance energy dissipation. The work will greatly broaden the range of applications of epoxies, will lead to a new thermoset printing technology and will introduce new material design concepts with diverse applications.
Additive manufacturing was developed to produce arbitrary shapes quickly at lower costs than previous prototyping techniques, such as injection molding, casting, or machining parts. The core technology to be developed within the Project is reactive inkjet printing as a technology to enable the additive manufacturing of novel thermoset composites based on epoxy-polyamine resins. Reactive inkjet printing allows overcoming the problems associated with pot-life and gradually changing properties of thermosetting inks such as viscosity and surface tension, which practically exclude jetting with standard printheads. The separate components of the resin are stable, even at elevated temperatures, and their reactive mixing occurs only after the deposition on the substrate. A unique selling point of reactive inkjet printing is in the possibility to manufacture entire multiscale structured parts, in particular gradient materials which ‘smoothly’ combine materials with different properties within one printed object. In one aspect, the mechanics can be tuned on a micrometer level, allowing the presence of neighboring harder and softer structures, which in this case can be achieved by adjusting the molar mixing ratio of the epoxy base and the hardener, leading to materials with different crosslink densities at the micro or mesoscale. In the second aspect, different macroscopic regions of a single printed part may exhibit different properties, realizing the concept of designing the ‘structure for purpose’. Importantly, in both cases there is a ‘smooth’ gradient transition between the separate regions and the presence of strong macroscopic interfaces is avoided, which otherwise could lead to the formation of cracks or other types of mechanical failure at high stress.
Another advantage of inkjet printing is the possible incorporation of nanofillers, i.e. in one of the inks, in order to obtain nanofilled composite materials. By using monodisperse filler particles functionalized with photoactive groups, the mechanical properties of the composites can be further structured by using patterned irradiation, leading to separate regions with strong and weak interfaces between the filler nanoparticles and the epoxy matrix. The two types of fillers will have different roles: those with strong interfaces will enhance the strength and modulus, while those with weak interfaces will be used to enhance toughness and arrest crack growth.
The main goal of the project is to proof the concept of reactive inkjet printing in the preparation of epoxy-amine multiscale structured composites and in consequence enable the technology to be useful in 3D printing. We are convinced that the realization of our concept will be a significant step forward in additive manufacturing as a whole, broadening the range of 3D printable materials from photopolymerizable acrylate resins to highly cross-linked epoxies in order to benefit from their superior mechanical, thermal and electric properties.