Effects of neutron irradiation on boron nitride and thermoplastic polyurethane nanocomposites considered for shielding in space

Boron nitride nanotubes (BNNTs) and thermoplastic polyurethane (TPU) nanocomposites show strong potential as lightweight shielding materials for space and nuclear applications. However, it is crucial to gain an understanding of the changes in materials' behaviour due to radiation exposure for their successful applications. In this study, we examine how neutron exposure affects the structure and other properties of BNNT/TPU nanocomposites under various neutron doses. We find that while BNNT buckypaper maintains structural integrity, TPU and BNNT/TPU nanocomposites undergo structural and chemical modifications. We interpret these changes to chain scission and branching in the polymers caused by neutron exposure. Mechanical test measurements show a decrease in the elastic modulus, yield strength, and ductility of irradiated TPU. On the other hand, the BNNT/TPU nanocomposites become brittle yet stronger, likely because of the high neutron absorption cross-section of BNNT. These findings provide useful insight for optimizing nanocomposites for applications in harsh and radiation-rich environments, including deep space.