The sealed vessel was placed either into a preheated ultrasound bath and heated for the desired dissolution time. Alternatively, a glass coated stirbar was added and the vessel was placed into a microwave chamber where it was heated and stirred at 600 rpm for the dissolution time. The dissolution was carried out at 75 • C in line with Qianhui et al. (2023) . After the desired dissolution time the undissolved PA 6 filaments were carefully removed from the vessel using a spatula while maintaining as much as possible of the clear solution containing CEW and dissolved PA in the vessel. The undissolved filaments were spread out onto a weighted filter paper (m F ) and washed on a vacuum filtration setup with 1000 ml of H 2 O to remove all CaCl 2 . After washing, the filter paper with the undissolved filaments (uPA) was dried at 40 • C over night and weighed (m F+uPA ) to determine the conversion according to equation 1: