Enhanced performance of PVC-based electromagnetic shielding composite films via solvent swelling-induced and microstructure optimization

With the growing severity of electromagnetic interference (EMI), developing efficient and more environmentally friendly shielding materials has become crucial. Traditional evaporation-induced phase separation (EIPS) methods suffer from long preparation cycles, significant solvent evaporation posing flash explosion hazards, and issues of filler sedimentation. Although non-solvent-induced phase separation (NIPS) is greener, its electrical conductivity and EMI shielding effectiveness (SE) remains limited. To address these challenges, this study proposes an innovative strategy: first preparing polyvinyl chloride (PVC)/carbon black (CB)/carbon nanotube (CNT) composite films via NIPS, followed by a solvent swelling-thermal drying process to reconstruct the conductive network. The NIPS method rapidly immobilizes fillers to prevent sedimentation, while subsequent immersion in a DMAc/H₂O mixed solvent (8:2 mass ratio) induces PVC swelling, promoting filler redistribution and densification. During thermal drying, solvent evaporation induces film shrinkage, further optimizing filler connectivity. Under optimized conditions (60 °C drying temperature, 20 minutes soaking), the film thickness decreases from 0.24 mm to 0.04 mm, while electrical conductivity dramatically increases from 16.5 S/m to 567.6 S/m, and EMI shielding effectiveness (SE) improves from 5.3 dB to 18.1 dB. When the film thickness is increased to 0.2 mm, the EMI SE reaches 32.9 dB, outperforming films prepared by conventional EIPS. This study not only overcomes the electrical conductivity limitations of the NIPS method but also avoids the safety risks of the EIPS method, providing a novel, greener, and safer approach for the fabrication of lightweight, high-performance EMI shielding materials. The proposed strategy shows significant potential for applications in flexible electronics and communication devices.