Polyurethane-grafted graphene oxide from repurposed foam mattress waste

Abstract

Polyurethanes (PU) make up a large portion of commodity plastics appearing in applications including insulation, footwear, and memory foam mattresses. Unfortunately, as thermoset polymers, polyurethanes lack a clear path for recycling and repurposing, creating a sustainability issue. Herein, using dynamic depolymerization, we demonstrate a simple one-pot synthesis for preparation of an upcycled polyurethane grafted graphene material (PU–GO). Through this dynamic depolymerization using green conditions, PU–GO nanofillers with tunable PU to GO ratios were synthesized. Chemical analysis revealed that the polyurethane graphenic materials primarily contained the polycarbamate hard-segment of polyurethane while the soft polyol component was removed in washes. PU–GOs were incorporated into bulk polyurethane foam to create composites as a filler at 0.25, 0.5, 1.0, and 2.0 weight percent filler and the thermal and mechanical properties of the resulting foams were analyzed. All PU–GO fillers were shown to improve thermal insulation up to a filler content of 0.5%, with all but 2 of the fillers demonstrating improvements up to 2% of filler content. The greatest decrease in thermal conductivity was 38.5% compared to neat PU foam, observed with the composites containing 0.5% of PU₁₀–GO₁ and 1.0% of PU₃–GO₁. Mechanical performance was tested for each foam and showed that lower polyurethane content graphenic composites produced foams that were less susceptible to fatiguing and more durable over cyclic loading, while higher polyurethane content graphenic composites had mechanical stability similar to neat PU but initially had greater impact resistance. Taken together, these novel PU–GO fillers prepared from repurposed PU mattress show promise as a sustainable additive to improve PU performance.