Upcycling Printed Circuit Board E-Waste to High-Strength, Multifunctional, and Reprocessable Sulfur Composites via...

Printed circuit boards (PCBs) are a major fraction of electronic waste, yet their glass-fiber-reinforced epoxy matrices remain effectively unrecyclable. Herein, we employ thiocracking, a one-pot reaction of elemental sulfur with PCBs, to convert them into functional composites. The process is 99% atom-economic and near-zero-waste, exploiting only PCBs and abundant refinery by-product sulfur as reagents. Mechanistic progression from model bisphenol derivatives to FR-4 laminates and shredded PCBs demonstrated that thiocracking cleaves aryl-O and C-C linkages within the polymeric structure and reconstructs the network through polysulfide catenates. The resulting composites exhibit compressive strengths of 16-19.5 MPa, flexural strengths of ≈3 MPa, and tensile strengths up to 3.3 MPa, within ranges of commercial masonry and cements. Critically, the composite prepared from whole shredded PCBs with 90 wt% sulfur (CNS₉₀) retains 100% of its storage modulus after 10 melt-recast cycles. Unlike masonry products, CNS₉₀ is thermally insulative with low thermal conductivity (0.37 W m^-1 K^-1). Composite-infused fabric also shows antimicrobial activity against foodborne pathogens, with >99.2% reduction of pathogens Listeria monocytogenes, Staphylococcus aureus, and Salmonella enteritidis, including organisms against which previously reported high sulfur material-infused textiles showed no activity at all. Thiocracking thus provides a strategy to transform e-waste into high-strength, recyclable, insulative, and inherently pathogen-neutralizing structural elements.