Functionalization of silk fibres through acid anhydride grafting: enhanced dye absorption, thermal stability, and durability

This work investigated the functionalization of degummed silk fibres via graft copolymerisation with acetic anhydride (AA) and maleic anhydride (MA) for low-temperature dyeing and improved durability. FTIR analysis confirmed the introduction of ester and carboxyl groups on the silk fibroin, with potassium persulfate as a free-radical initiator. The dye affinity of modified fibres towards Direct Blue 1 and Direct Red 28 was enhanced, enabling almost complete exhaustion of the dye at decreased dyeing temperatures (60–70°C) as well as reduced processing times and lower electrolyte concentrations than untreated silk. MA-grafted silk outperforms the treatments, offering higher dye uptake at a more conducive pH, therefore reducing dyeing temperature and chemical consumption. MA modification improved thermal stability according to thermogravimetric analysis, improved tenacity levels on prolonged exposure to sunlight and displayed superior colour fastness to washing, alkali, and photodegradation, which suggested an increase in durability and a longer service life.