High performance polyimides for additive manufacturing: A critical review

• Comprehensive overview of AM techniques for thermosets & thermoplastic Polyimides is provided. • Structural tuning enhances PI printability while retaining thermal performance. • TPIs emerge as key candidates for AM due to thermoplastic processability. • Functional PI inks enable high-resolution 3D printing using VPP and DIW. • Future scope includes smart, multifunctional PI composites for next-gen AM. High performance polymers (HPPs), particularly polyimides (PIs), including both thermosetting and thermoplastic types, exhibit remarkable properties such as exceptional mechanical properties, outstanding thermal stability, and inherent flame retardancy. PIs are lightweight and potentially economical alternatives to metal based materials used in demanding applications, such as aerospace, transportation, and defense. However, processing PIs into the desired complex shapes is a significant challenge owing to their high melting temperature, high melt flow viscosity, and very narrow processing temperature window. Additive manufacturing (AM) techniques present an important avenue for processing such materials and emerged as a revolutionary approach to overcome these limitations, offering unprecedented design flexibility, reduced material waste, and the capability for rapid prototyping and production. Despite these advantages, AM of PIs has received considerably less attention, primarily due to significant processing challenges including material printability, thermal management complexities, and dimensional accuracy challenges that have hindered further advancements in this field. This comprehensive review explores the evolution and current status of polyimides additive manufacturing, providing insights into their chemistry, structural modifications, and detailed structure-property relationships. Various AM techniques including vat photopolymerization, material extrusion, direct ink writing, material jetting along with hybrid and emerging approaches are critically discussed, highlighting recent innovations, key challenges, and strategic solutions to enhance processing capabilities. Furthermore, the review identifies prospective research directions, emphasizing the potential for multifunctional and stimuli-responsive polyimides that could revolutionize next-generation applications. Overall, this review aims to stimulate further advancements in polyimide based additive manufacturing, fostering its broader industrial adoption and facilitating significant developments in high performance polymer technology.