Electron‐Beam Cross‐Linking as a Post‐Processing Strategy to Stabilize Percolated CNT Networks in LDPE for Broadband EMI Shielding

Low‐density polyethylene (LDPE) filled with carbon nanotubes (CNTs) is a scalable platform for lightweight electromagnetic interference (EMI) shielding. However, the stability of percolated CNT networks under thermomechanical loading remains a key limitation for wire and cable applications. In this work, electron‐beam (EB) irradiation is introduced as a post‐processing control parameter to stabilize CNT conductive networks independently of filler loading. LDPE/multiwalled CNT composites containing 0–10 wt% CNT were prepared by melt compounding and irradiated at absorbed doses of 0–200 kGy using trimethylolpropane trimethacrylate as a cross‐linking co‐agent. Unirradiated composites exhibited an electrical percolation threshold at approximately 2.5 wt% CNT, with DC conductivity increasing by nearly nine orders of magnitude above this threshold. EB irradiation increased the composite insoluble fraction from approximately zero to more than 60% at 150–200 kGy. This was accompanied by significant improvements in tensile strength, elastic modulus, and hot‐set resistance at 200°C, while changes in melting temperature (< 2°C) and crystallinity (< 6%) remained minor. For percolated compositions (≥ 5 wt% CNT), both DC and AC conductivity were largely preserved after EB processing, indicating stabilization rather than disruption of CNT–CNT transport pathways. As a result, EB‐crosslinked CNT/LDPE composites achieved broadband, absorption‐dominated EMI shielding with total shielding effectiveness (SE) of approximately 25–32 dB over 10 MHz–3 GHz at a thickness of ~1.5 mm. These results establish a quantitative composition–dose–performance framework in which CNT loading governs electrical percolation and shielding magnitude, whereas EB‐induced cross‐linking governs thermomechanical robustness and service stability. The proposed decoupling strategy provides a practical route to durable, additive‐modified polyolefin EMI shielding materials compatible with industrial electron‐beam processing.