UC Davis

Mechanical deconstruction of post-consumer carpet results in plastic fibers as well as a finepowder, comprised mostly of calcium carbonate (CaCO3), ready for reuse. This powder is referred to as post-consumer carpet calcium carbonate (PC4) and contains low levels of microplastic fibers along with a wide range of trace components such as sand, antimony, perfluorinated compounds, and brominated flame retardants. While plastic fibers are relatively easy to reuse, the trace components of PC4 present recycling challenges. Clean-up of this powder is crucial for developing appropriate uses in recycled-content product manufacturing. Thermal treatment, ashing/combustion with oxygen present or charring/pyrolysis if oxygen is excluded, is proposed as a relatively low-cost method to break down microplastics and other hazardous components that accumulate in carpet. Fourier transform infrared (FTIR) spectroscopy was used to quantify the mass loss of polyethylene terephthalate (PET) as well as nylon 6 (N6) in PC4 samples when heated for 1 hour at 500 and 600 °C with and without oxygen. Single-bounce attenuated total reflectance, ATR-FTIR was used in addition to synchrotron-based FTIR microspectroscopy (SR-μFTIR) and a modified microscopic ATR-FTIR imaging technique using a large germanium hemisphere and focal plane array (FPA) detector. The data demonstrate that heat treatment at 600 °C successfully reduced both PET and N6 content below detection limits. Maps obtained via FTIR imaging reveal the size and spatial distribution of microplastics in PC4. This work is novel and significant as it addresses the long-term environmental challenges of waste and pollution from consumer goods and assesses the effectiveness of post-consumer carpet recycling.