Tinctorial Response of Recycled PET Fibers to Chemical Modifications during Saponification and Aminolysis Reactions

In this article we show that poly­(ethylene terephthalate) (PET) fibers obtained from the recycling process of PET bottles can be chemically modified and used to create materials destined to become clothing articles. The modifications of the characteristics of PET fibers through saponification and aminolysis reactions have been studied. The work represents a comparative study of the behavior of PET virgin (of synthesis) fibers versus recycled PET fibers (from PET bottles). Comparisons have been made between the modifications which appear in physical and chemical structures, thermal stability, mechanical properties, and dyeability under the action of some reactions with NaOH, with ethylene diamine, or with their mixture at 20 °C. The FTIR, SEM, EDAX, XRD, DSC, and TGA analyses made evident the differences/similarities between the two types of studied polyester fibers. The recycled PET fibers are much less crystalline, more stable at high temperature, and easier to dye with nonspecific (anionic and cationic) dyes. After the treatment with AgNO₃, the virgin/recycled PET fibers, chemically modified (which have NH₂ groups), have antimicrobial activities due to their affinity for Ag ions. The silver presence on the treated samples can be seen even after 10 cycles of repeated home laundering. The only inconvenience of the treatments meant to modify the PET chemical structure is tenacity diminution, manifested in different ways, depending on the reagent type, concentration, and duration. However, the recycled PET fibers can be used to create materials destined to become clothing articles (by themselves or blended with synthetic/natural fibers) which can be more easily and more economically dyed in a single bath and a single stage