Crystallographic Fingerprints of Thermal Textile Residues: Insights into Material Origin and Thermal Treatment Conditions from X-Ray Powder Diffraction and SEM–EDX

Thermal degradation of textile materials produces complex residues whose characterization can provide information on both the original material and the conditions experienced during heating. This study investigates the potential of X-ray Powder Diffraction (XRPD) as a complementary approach for the characterization of textile thermal residues and for evaluating whether crystallographic features can retain information on textile composition and thermal exposure conditions. Twenty-five commercial textile samples, including natural fibres (cotton and silk) and synthetic polyester-based fabrics, were characterized before and after controlled thermal treatments at 400 and 800 ◦C under air and a modified atmosphere containing 10% O2. The untreated fabrics exhibited characteristic diffraction patterns related to their fibre composition, whereas the residues showed significant changes depending on both the original textile and the treatment conditions. Higher-temperature treatments produced more crystalline residues, allowing improved discrimination among different textile categories. Differences between air and oxygen-limited conditions were also reflected in the diffraction patterns, indicating that oxygen availability influences the evolution of crystalline phases during thermal degradation. SEM–EDX analyses supported the interpretation of the diffraction data, although several residues showed complex patterns that prevented unambiguous phase identification. Overall, the results indicate that XRPD can provide valuable complementary information on the crystallographic evolution of textile thermal residues and may contribute to the characterization of textile composition and thermal exposure conditions.