Mechanochemical Depolymerization of PET: Kinetic Studies on Alkaline Hydrolysis of Commercial Feedstocks

The mechanochemical depolymerization of commercial PET feedstocks is successfully demonstrated for a variety of samples representing consumer products without the need for specific sample pretreatment. Complete depolymerization is achieved within 20 min by ball milling it with NaOH under ambient conditions. Samples with a higher initial content of amorphous domains depolymerize more rapidly, as collision energy is more effectively utilized for creating reactive interfaces between NaOH and PET. While thickness has a minor effect compared to crystallinity, thicker samples experience lower reaction rates because their accessible surface area is limited. For low-packing density samples, a reduced rate of depolymerization could be expected due to restricted ball motion, but this effect is overcompensated by the ease at which these samples form interfaces. The success of mechanochemical alkali-depolymerization of PET in a ball mill presents an opportunity for industrial implementation, offering a sustainable approach to polymer upcycling due to its mild reaction conditions and minimal solvent requirements.