Interfacial Cross-Linking-Driven Hierarchical Crystal–Amorphous Design Enables UHMWPE with Superior Mechanical and Thermal Resistance

Polyethylene is widely used as a matrix resin for nuclear radiation protection due to its lightweight, high economic efficiency, and high hydrogen content. However, the intensification of the linear molecular chain motion of polyethylene and the sharp deterioration of mechanical properties at high temperatures have severely limited its application. In this study, polyethylene composites with a hierarchical crystal–amorphous structure have been prepared using the interfacial cross-linking strategy. The enhancement of the mechanical and heat-resistant properties of the composites was realized by modulating the crystalline-cross-linked structure. The intrinsic mechanism of the performance enhancement lies in the construction of a micrometer-scale interfacial three-dimensional cross-linking skeleton, which can effectively inhibit the slip of molecular chains. Meanwhile, the interfacial cross-linking technique greatly preserves the internal nanoscale highly crystalline structure, which promotes improvement of thermodynamic properties. This method improves the heat resistance of the material without compromising the neutron shielding properties. Compared with the uncross-linked polyethylene, the tensile strength increased by 67.1% and creep resistance by 40.2% at 70 °C. The Vicat softening point was increased to 136.6 °C. At a thickness of 10 mm, the neutron transmittance of the cross-linked polyethylene was 81.87%, showing good neutron shielding capability. Interfacial cross-linking-driven hierarchical crystal–amorphous technique is a simple and effective method for the preparation of highly heat-resistant polyethylene shielding materials.