Carbon–Boron Hybrid Polyethylene with Excellent Thermal Stability and Neutron Shielding Property

Polyethylene, due to its high hydrogen content, is widely utilized in nuclear facilities for neutron shielding. However, its inadequate thermal resistance limits its applicability in higher-temperature environments. The construction of carbon–boron (C–B) hybrid cross-linked networks by carborane enhanced the thermal performance of the material. At present, the synthesis methods for carborane derivatives are not sufficiently safe, efficient, and suitable for large-scale production, which restrict their application in resins. In this study, we synthesized 1,2-dichloromethyl-o-carborane (CBCl₂), which acted as intermediates to develop ethylene-functionalized carborane derivatives for the first time. This derivative was introduced as a cross-linking agent into PE through cross-linking reactions, resulting in the formation of a C–B hybrid cross-linked network. In situ protection and promotion of graphitization mechanisms significantly improved the thermal stability of the materials. At 800 °C, the thermal residue of the materials increased by 21.01 wt % (in nitrogen) and 30.83 wt % (in air). Despite a slight reduction in hydrogen content, there was a substantial increase in boron content, which enhanced the shielding effectiveness against both thermal and fast neutrons. This work expanded and optimized the synthetic pathways for carborane derivatives, improving various properties of polyethylene and thereby ensuring its safety in nuclear facilities.