Chemical Recycling of Bakelite Thermoset Resin by Thiocracking To Yield a High-Strength, Recyclable Composite

Abstract Bakelite is a phenol–formaldehyde thermoset with exceptional thermal stability and is an environmentally persistent material for which viable recycling methods are lacking. Elemental sulfur, an overproduced petroleum refining byproduct, similarly accumulates in large stockpiles. We report a one-pot, 100% atom economical thiocracking strategy to upcycle intractable Bakelite waste into a thermally processable composites ( BLS 90 ) via reaction of Bakelite with molten sulfur at 230 °C. Model compound studies reveal the effective breakdown of the Bakelite structure via C–C and C–O s-bond scission with concomitant benzylic S–C bond formation, leading the crosslinking via oligo/polysulfur catenates. The resulting composite exhibits a glass transition at − 36 °C, a melting transition at 118 °C, and decomposition onset at 235 °C. BLS 90 demonstrates a compressional strength of 27 ± 2 MPa, exceeding that required for ordinary Portland cement building foundations (17 MPa), and flexural strength of 4.9 ± 0.6 MPa. These findings demonstrate that thiocracking enables effective partial replacement of the thermally intractable C–C crosslink network with thermally reversible sulfur catenate crosslinks. This process yields a mechanically robust and thermally reprocessable material from the otherwise non-recyclable thermoset. This approach offers a dual waste-mitigation pathway for Bakelite and surplus elemental sulfur, producing composites suitable for structural applications while advancing the sustainable management of polymer and industrial sulfur waste streams. Graphical Abstract