Pyrolysis behaviour and kinetic analysis of waste polylactic acid composite reinforced with reed straw processing residue

The lignocellulose reinforced composites are commonly used sustainable materials with good mechanical and physical properties. Aiming to properly dispose and recover the potential value of discarded lignocellulose reinforced composites, the pyrolysis behaviour and kinetics of reed straw processing residual/polylactic acid (RSPR/PLA) composites, a typical 3D printing material, was investigated. Based on the TG-FTIR results, the synergistic effects between RSPR and PLA during the pyrolysis process were clarified. Compared with the FTIR spectra of PLA, the absorption peaks of CO and CO₂ disappear in the FTIR spectra of RSPR/PLA composite, which indicates RSPR provides additional free radicals for the free radical reaction of PLA, and further promoting the decomposition. The apparent activation energy of the RSPR/PLA composite pyrolysis was calculated by two iso-conversional methods including Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS). The average E_a of the RSPR/PLA composite (122.6 kJ mol⁻¹ (FWO) and 117.9 kJ mol⁻¹ (KAS)) was lower than that of solo pyrolysis of RSPR (138.5 kJ mol⁻¹ (FWO) and 135.4 kJ mol⁻¹ (KAS)) and the pure PLA (197.0 kJ mol⁻¹ (FWO) and 196.6 kJ mol⁻¹ (KAS)). The master plot method results suggested the pyrolysis of RSPR/PLA composite followed the one-dimensional (D1) diffusion model. This work provides an environmentally friendly strategy to effective thermo-chemical upgrading of the value of discarded lignocellulose reinforced composite material.