The hornification of cellulose in chemical textile recycling

Currently, legislation and consumers’ environmental awareness drive toward textile recycling. Fiber-to-fiber recycling is found preferred and the only sustainable method. However, many of the developed polycotton recycling methods require harsh reaction conditions that cause unwanted hornification of the cotton fraction.
Polyester chemolysis methods were thus studied in terms of cotton hornification. The obtained cotton fractions and a post-consumer cotton reference sample were analyzed by several fiber characterization methods and dissolution tests. Two restoring methods were also applied to study whether the effects of fiber hornification that occurred in the chemolysis methods could be removed.
As expected, hornification occurred during chemolysis methods. However, none of the chemolysis methods was found superior to others. The fiber solubility decreased after chemolysis methods, and the effects could not be removed by the restoring methods. The solubility was however improved with all samples by the enzymatic treatment. All enzyme-treated chemolysis samples also showed better solubility compared to the untreated reference sample. Due to the poor dissolution of all samples, no clear results were however obtained from the characterization of dissolved cellulose and regenerated cellulose films analysis. Thus, the use of tested chemolysis methods is not advisable if the aim is to use the cellulose fraction into regenerated products.