Sterically Hindered Aliphatic Polyamine Cross-Linking Agents for Epoxy Resin Recyclability

The patent changes the chemical structure of the cross-linking agent by introducing sterically hindered aliphatic polyamines with specific molecular structures (Formula 1) that have controlled reactivity. This parameter change in molecular structure allows the system to achieve both extended working time and recyclability by modifying the cross-linking mechanism rather than simply adding more time or heat.

The patent introduces dynamic characteristics to the cross-linking system through cleavable cross-linking groups that can break down under specific conditions. This allows the cross-linked polymer to transition from a stable cured state to a degradable state, enabling recyclability while maintaining structural integrity during the working time period.

The patent implements a two-stage curing process with distinct time periods: a first period for polymerization and cross-linking at elevated temperature, and a second period for degradation and recovery at lower temperature. This periodic action allows the system to achieve complete curing when needed while enabling processing and handling during the extended working time period before final curing.

The patent performs preliminary polymerization and cross-linking reactions during the first curing period at elevated temperature, creating a partially cured network that provides structural integrity. This preliminary action allows the material to be handled and processed during the working time period, with the final curing occurring after processing is complete.

The patent enables the degradation of cross-linked polymers under specific conditions to recover and reuse the original monomers and oligomers. The cleavable cross-linking groups allow the network to be systematically broken down, and the recovered materials can be reused in new formulations, creating a circular material flow that maintains structural stability during use while enabling recycling when needed.

The patent introduces dynamic reversibility to the cross-linking system through cleavable cross-linking groups that can transition between bound and unbound states. This dynamic characteristic allows the cross-linked structure to maintain stability during normal use while enabling controlled degradation for recycling, effectively making the cross-linking reaction reversible under appropriate conditions.