Pyrolysis characteristics of blended textile in waste clothing

Abstract

The pyrolysis of blended textiles from waste clothing was studied to advance the technology for recycling such materials. Waste garments made of polyester/cotton, a common blended textile, were used as experimental samples. The pyrolysis properties of polyester/cotton were examined using thermogravimetric analysis (TGA) and laboratory-scale pyrolysis experiments. The thermogravimetric (TG) curve indicated that the pyrolysis of polyester/cotton began at 255.1 °C and ended at 471.7 °C. The pyrolysis derivative curve for polyester/cotton displayed three peaks, with the most significant peak at 353.8 °C and minor peaks at 319.9 °C and 403.4 °C. Laboratory-scale pyrolysis experiments were then performed at heating temperatures of 400, 500, 600, and 700 °C. The pyrolysis products were characterized by analyzing the char, tar, and gas generated. The polyester/cotton char exhibited a high higher heating value (HHV) of 32,640 J/g-char (db) at 600 °C. The tar composition revealed that the polyester/cotton char was primarily composed of fragments with a phenyl structure derived from polyester, with benzoic acid being a notable tar component. This composition was marked by significant production of polycyclic aromatic hydrocarbons, even at pyrolysis temperatures below 700 °C. The main components of the pyrolysis gases were CO₂ and CO at low and high temperatures of 400 and 700 °C, respectively. By summarizing the composition of tar and gas in relation to pyrolysis temperature, a mechanism was proposed in which interactions between the hydroxyl groups in the molecular structure of cotton and the benzene rings in the molecular structure of polyester during pyrolysis lead to CO formation. These findings contribute to the development of recycling technologies for utilizing waste clothing as an energy source and chemical feedstock.