Healing and Reprocessing of Epoxy with Dynamic Covalent Bonds and Composites

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This grant provides funding for the study of the relationship between processing conditions and the healing and reprocessing of polymers and polymer composites containing dynamic covalent bonds. A significant feature of these polymers is that the backbone of the macromolecular chain can break and reconnect through bond exchange reactions. While such dynamic covalent reactions do not change the overall topology and properties of the polymer network, macroscopically they result in stress relaxation and material welding. The proposed work will examine the bond exchange reaction kinetics and welding kinetics and their dependence on processing conditions. Epoxy samples containing dynamic covalent bonds will be prepared in the lab and tested under different thermo-mechanical loading conditions to understand the effects of temperature on the bond exchange reaction kinetics. These samples will be broken then joined together under different thermo-mechanical loading conditions. Special dyes will be incorporated into polymer samples to facilitate monitoring the bond breaking and reforming process, as well as the migration of species due to bond exchange reactions. From these experiments, the relationships between bond exchange reaction kinetics, welding kinetics, and processing conditions will be established. The re-processibility of the dynamic covalent bond epoxy and its composites will also be investigated.If successful, the results from this work will lead to the development of new ?green? epoxy and composites that can be reshaped and recycled. The primary goal of this research is to establish fundamental principles for bond exchange reaction kinetics and welding kinetics. These principles may include how processing parameters, such as temperature, hold time, applied pressure, and surface roughness, can affect reshaping, welding, and re-processibility of the epoxy. Determining these processing parameters will enable robust processing and recycling of the epoxy, reduction in processing cost, and improvement on product quality. The established principles can also be used for polymers containing other types of dynamic covalent bonds.