Research Projects

Traditional thermoset epoxies comprising of permanent bonds exhibit robust mechanical strength, dimensional/thermal stability and chemical resistance qualifying it for many industrial applications, such as aircraft and automobile industries, electronic devices and so on. However, the challenges they pose are that they cannot be reshaped, (re)processed or recycled once cured (a 10 to 12 hour curing cycle is required) and ends up in landfill or needs to be incinerated after the life of the material. In contrast, thermoplastics flow on heating, thus enabling multiple processing but they are limited by their poor mechanical properties, solvent and heat resistance, structural stability. Therefore, it is desirable to fabricate materials having the combined mechanical properties of thermosets and (re)processable and recyclable nature of thermoplastics. This can be achieved by the incorporation of covalent adaptive networks (CANs) where the dynamic linkages are reversible and exchangeable when exposed to certain reaction conditions without suffering any loss in the structural integrity. These CANs can also release stress from deformation, allowing the cross-linked polymers to be reprocessed, reshaped, and recycled. This work is ultimately aimed at optimising an epoxy vitrimer possessing excellent strength- to- weight ratio capable of being rapidly processed by moulding along with self-healing property for easy repair of structural defects and recyclability. Vitrimers are a type of cross- linked polymers that can undergo topological rearrangement through covalent dynamic bond exchanges. Here, associative networks are considered for obtaining exceptional mechanical and thermal properties. The fast curing, (re)processable epoxies possessing a dual dynamic network (imine and acetal exchange) are introduced that allows to fix the network topology below the service temperature (less than 180 °C) and allows to re-process at a temperature greater than 180°C (where it flows like common thermoplastics) and below 180 °C where it behaves like traditional thermoset due to frozen linkages. The hardener is designed such that the dynamic networks cure the epoxy within 2 hours at 120 °C with excellent mechanical properties. Due to the presence of exchangeable Schiff base and acetal moieties formed by the conjugation of two reactants, there is an enhancement in probability for dynamic exchange reactions which further results in the re-processability, re-cyclability of the prepared Epoxies.

Covalent adaptable network, recyclable, reshaping, reusable, reprocessing.