Executive Summary : | The properties of thermoset polymers like good mechanical strength, solvent resistance, etc. have led to an explosive growth of plastic consumer products based on them. Unfortunately, they end up polluting the environment once they reach the end of their life because of their non-degradability. Covalent Adaptable chemistry involving reactions like transesterification, disulfide, imine exchange, etc. has enabled a new perspective on circular economy involving polymeric materials. These adaptable chemistries can produce materials with dynamic covalent crosslinks that undergo exchange reactions under specific stimuli thereby enabling recyclability to hitherto non-recyclable polymers like the thermoset polymers. The proposal aims to make use of these dynamic chemistries to create a toolbox of thermosetting polymers for Additive Manufacturing (AM). The incorporation of the covalent adaptable networks in the photocurable resin formulation is anticipated to allow reprocessing the 3D printed object to reshape, repair, or recycle. Dynamic polymers incorporating labile covalent bonds have the unique ability to activate the embedded dynamic chemistries upon external stimuli enabling the material to transition from solid to fluid-like flow. These materials are characterized by typical properties like a gradual decrease of viscosity upon heating that endows them with unique properties like self-healing, network reorganization, etc. The beauty of the covalent adaptable network (CAN) is its feasibility to be introduced into conventional crosslink networks like the photocurable resins in 3D printing or epoxy resins for composites. Additive manufacturing has seen explosive growth due to its promise of customized solutions for all products. More and more industries as well as the strategic sectors like the defense are incorporating AM into their development platforms. Therefore, this is the right time to develop novel materials that impart mechanical strength while at the same time allowing recyclability for 3D printing applications. The scientific objects of the proposal are to develop a photocurable resin formulation that incorporates dynamic covalent chemistry, which would enable the photocured 3D printed objects to be further cured thermally to obtain objects with enhanced mechanical properties. As proof of concept the 3D printed objects would be subjected to reprocessing by exposing them to external stimuli like heating or the addition of excess monomeric functionalities to push the equilibrium to CAN bond dissociation. The reformed new formulation would be mixed with more photocurable resins and utilized as new formulation for printing new 3D objects. The proposal also aims to study the effect of small molecule versus oligomeric moieties incorporating the dynamic covalent groups towards the mechanical strength of the 3D printed object. The applicability of such optimized formulations to develop custom-designed 3D printed consumer products would be explored. |