Conversion of Waste PET Plastic to Aramid Fiber

A three-step synthesis was used to convert waste poly(ethylene terephthalate) (PET) into the high-value polymer, poly-para-phenylene terephthalamide (PPTA), used in the production of high-strength aramid fiber, such as Kevlar. Improvements to the polymerization reaction by the addition of calcium chloride to the solvent, N-methyl-2-pyrrolidone, and rigorous anhydrous conditions enabled the production of PET-derived PPTA with a 4.15 dL/g inherent viscosity in sulfuric acid that is amenable to fiber spinning. PPTA fibers were spun using a wet spinning apparatus under varied process parameters to assess their impact on fiber surface morphology, diameter, and the mechanical properties of the fibers. Select fibers were subjected to a postspinning heat treatment at 150 °C, which improved the tensile strength and modulus by 100% and 30%, respectively, relative to the as-spun fibers. Techno-economic and life-cycle analyses were conducted to evaluate the economic feasibility and the life-cycle greenhouse gas emissions of the approach. The results suggest the potential for up to a 30% cost reduction and comparable greenhouse gas emissions against conventional petroleum-based processes.