Plasma-electrified repair of damaged polymer composites for surface crack healing and insulation recovery

Polymer composites, widely used in aerospace and electrical power systems, are inevitably aged by environmental stress causing cracks on the material's surface, which weakens their mechanical and electrical properties. Addressing the issue requires significant effort and the use of hazardous chemicals. In this study, a novel plasma-electrified repair method based on the Ar/H₂O/alkoxysilane (PMDMS) low temperature plasma is developed for the surface crack healing and insulation recovery of silicone rubber (SIR) composites. It is demonstrated that the plasma-enabled polymerization effectively repairs the cracked SIR, with a new fin-like insulating layer deposited on the crack surface. The mechanical and electrical properties of the cracked SIR are improved after the plasma repair, with the result clearly better than using the conventional coating method. Hydrolysis-condensation of PMDMS by plasma-enabled dissociation and re-assembly, surface activation of the crack by plasma modification and grafting-crosslinking in the crack account for the multiphase chemical reactions induced within the crack. Further analysis based on quantum chemistry calculations reveals that the plasma treatment both promotes the chemical reactivity of the SIR surface and reconstructs a dense repair phase in the crack with a wide forbidden gap and shallow taps, further confirming this effective crack healing process which improves the mechanical and electrical performances of the damaged SIR. Overall, this newly-developed plasma-electrified repair method for damaged SIR eliminates the environmental pollution caused by large scale and overused chemical coatings, and offers new possibilities for sustainable and low-carbon-emission material engineering for processing and restoration of composite materials.