Charge Injection Suppression and Breakdown Strength Enhancement of Cellulose Pressboard via Al₂O₃/PTFE Functional Film Depositing

Under dc voltage, space charge effect becomes a key issue to restrict the insulation performance of the polymer insulation. In this research, novel Al ₂ O ₃ /poly-tetra-fluoroethylene (PTFE) composite functional film is fabricated by magnetron sputtering on the insulation pressboard surface to suppress space charge accumulation and to improve breakdown strength. The depositing sequence for composite film is determined by molecular simulation. The composition and the morphology of the prepared film are characterized and the thermal stability is evaluated. Pulsed electro-acoustic (PEA) results show that the space charge amount is reduced over 40% for the sputtered pressboard, indicating that the functional film owns an obvious positive effect on charge injection suppression. Less injected charges weaken the electric field distortion and lead to higher breakdown strength. This inhibition effect is mainly attributed to the deep trap and charge capture ability introduced by the functional film. This work provides a novel way to tailor the properties of the dielectric materials.