FTIR–XRD comparative study of pyrolysis residues obtained from plastic waste

This study examines the thermal degradation of PET-1 plastic waste containers (SIRAB, Azerbaijan) using FTIR spectroscopy and XRD analysis. Samples were pyrolyzed at 350°C, 450°C, and 550°C for 1 h under inert conditions. XRD results show a progressive loss of crystallinity with increasing temperature, leading to an almost fully amorphous, carbon-rich residue at 550°C. FTIR analysis indicates significant chemical changes above ∼420°C, including the formation of carbonyl-containing compounds (∼1679 cm⁻¹) and O–H related bands (2500–3062 cm⁻¹), associated with pyrolysis products formed via chain scission.Overall, combined FTIR and XRD results confirm a temperature-dependent degradation pathway characterized by structural amorphization and the formation of oxygenated aromatic residues.