How does electron-beam radiation help cross-link plastics?

Electron-beam radiation facilitates the cross-linking of plastics through a process known as free-radical interlinking. When a polymer is exposed to high-energy electron-beam radiation, the energy disrupts chemical bonds within the material, specifically tearing away a hydrogen atom from the polymer molecule.1

This action leaves behind a highly reactive carbon atom, referred to as a free radical. Because these radicals are unstable and short-lived, they seek to stabilize by coupling with another carbon radical on a neighboring molecule. This coupling creates a stable carbon-to-carbon (C–C) bond, effectively interlinking different polymer chains. This process is highly effective for cross-linking various materials, including fully saturated polymers like polyethylene, which otherwise lack the reactive sites required for traditional chemical vulcanization.12