Co-pyrolysis model for polylactic acid (PLA)/wood composite and its application in predicting combustion behaviors

Polylactic acid (PLA)/wood composite has gained great popularity in applications due to its renewable and biodegradable features, whereas quantitative modelling from microscale co-pyrolysis to bench-scale combustion was barely reported. To challenge this issue, poplar wood, PLA and three PLA/wood composites with mass ratios of 1:3, 1:1, and 3:1 were adopted to conduct thermogravimetric analysis (TGA) and cone calorimeter tests. A numerical model was utilized to examine the interaction between wood and PLA during co-pyrolysis. Kinetics and temperature-dependent thermodynamics of each component were determined by inversely modelling some specific experimental results, while the remaining data were used for model validation. Effective heats of combustion of gas products were estimated by fitting the recorded heat release rates (HRR) in combustion tests. The results showed that PLA/wood composites considerably reduced the peak temperature of co-pyrolysis by 21.7–23.7 K compared to neat PLA. Pyrolysis of wood and PLA could be described by a four-component reaction scheme and a single-step reaction, respectively, whereas two additional reactions were needed to quantify the interaction between PLA and wood. Three methods were used to predict the measured HRRs, and all calculated curves fitted the experimental results well. PLA/wood composites decelerated the thickness regression rate and prolonged the combustion time. Meanwhile, measured CO and CO2 production rates were thoroughly analyzed.