3D Printing of Bismaleimides: From New Ink Formulation to Printed Thermosetting Polymer Objects

Additive manufacturing is a novel manufacturing paradigm which has numerous potential applications in industry and research. PolyJet technology allows printing of extremely complex geometrical structures with high precision and smooth surface. New engineering polymers with diverse characteristics should be developed to expand PolyJet applications. Bismaleimides (BMIs) are very attractive polymers due to their excellent thermal, mechanical, and chemical stability, and their good dielectric properties. However, BMIs are currently not available as inks for PolyJet technology. Low-viscosity aliphatic BMIs are used to develop a novel UV-curable ink. The UV reactivity and ink viscosity are optimized by addition of an environmentally friendly diluent and a mixture of photoinitiators. Optimization of the jetting and printing conditions allows for the first ever production of 3D thermosetting BMI objects by PolyJet technology. Thermal post curing is used to enhance mechanical properties and thermal stability of the printed material. It is found to have a thermal decomposition temperature, T_5%, of about 400 °C, low dielectric constant, high dielectric strength, and low moisture absorption. The resulting properties of the printed BMI material open a wide range of potential applications in fields such as robotics, electronics, automotive, aerospace, and space technology.