High-performance materials for mask-projection stereolithography via in-situ sequential interpenetrating network

Stereolithography, a common technique used in additive manufacturing, offers high dimensional accuracy. However, there are limited choices of materials for this process. Acrylates and epoxies are commonly used, but their thermal properties are not suitable for applications in which high temperature performance is needed. In contrast, high-performance thermosets such as bismaleimide and cyanate ester are cured using high temperature processing techniques, and their use for stereolithography is limited. In this work, a photocurable formulation of bismaleimide, a reactive diluent, and cyanate ester was developed to improve thermal and mechanical properties as well as cure shrinkage of stereolithography resins. In-situ sequential interpenetrating polymer network (IPN) were investigated wherein the copolymerization reaction between bismaleimide and diluent occurs during printing, resulting in a cyanate ester swollen network with sub room temperature glass transition temperature (Tg). The polymerization of cyanate ester takes place during post processing. The resulting material possesses a Tg well above 200oC (loss modulus peak), significant decrease in cure shrinkage, and improved toughness.