Molecular recycling of condensation polymers
Current plastic recycling methods are limited by polymer degradation and therefore require the addition of a significant amount of virgin plastic to maintain product quality. Molecular recycling is a more advanced technique that is not restricted by polymer degradation and allows the conversion of plastic waste into virgin-quality plastic through chemical reactions.
However, molecular recycling requires further development to improve its industrial relevance. The purpose of Joël Benninga's thesis is to contribute to this aim through the application and development of several molecular recycling techniques for a wide variety of commercial polymers.
Benninga presents the catalyst-free molecular recycling of a commercial polyurethane through a novel depolymerization technique, which required only water at elevated temperatures. In addition, the enzymatic degradation of various polyester blends is reported, thereby providing insight and opening up the possibility for the enzymatic recycling of commercial polyester blends.
Finally, Benninga studied the chemical recycling of poly(p-phenylene terephthalamide) (PPTA), which is commercially used for making aramid fibers. In collaboration with Teijin Aramid, Benninga developed a microwave-assisted recycling process, which resulted in rapid conversion of PPTA powder into its building blocks terephthalic acid and p-phenylenediamine, which were obtained in good yields and high purities. Additionally, the developed process was applied to para-aramid Twaron fibers.
Benninga presents an extensive microscopy study in which the degradation mechanisms involved in the recycling process are revealed, providing crucial insights into process optimization and eventual scale-up.
See also: Recycling your bulletproof vest in a microwave reactor