Pyrolysis of 3d Printed Polylactic Acid Waste: A Kinetic Study Via Tg-Ftir/Gc-Ms Analysis

Abstract

Polylactic acid (PLA) is one of the most common 3D printing materials. The waste of 3D printed products mainly made of PLA have relatively high calorific value and low impurities, which makes it possible to realize energy utilization through thermal conversion. In this study, the pyrolysis characteristic of 3D printed PLA waste (3DP-PLAW) was studied by TG-FTIR/GC-MS. Different from pure PLA pyrolysis in previous research, two main pyrolysis stages (260-390 °C and 390-500 °C) were observed during 3DP-PLAW pyrolysis. After reaching 390 °C, the residual ash and char were subjected to secondary reaction. It was speculated that the second pyrolysis stage may be due to the change of PLA physicochemical properties during 3D printing process. And the higher heating value (HHV) of 3DP-PLAW was 20.949 MJ·kg-1, which was higher than pure PLA. The pyrolysis kinetics of 3DP-PLAW was analyzed by DAEM, FWO, Straink and Friedman methods. It was found that the activation energies obtained by these four methods were basically the same (E ave = 206 kJ·mol-1), indicating that these methods were applicable to biomass plastics. TG-FTIR/GC-MS results showed that CO, CO2, CH4, CH3CHO, esters, carbon-basis compounds and ethene were the main gaseous products of 3DP-PLAW pyrolysis. Different from previous study of pure PLA, there is no ketone observed in gaseous products during 3DP-PLAW, which implies that energy recovery of 3DP-PLAW may be an environmentally friendly management method. This study is expected to provide fundamentals for 3DP-PLAW energy recovery and utilization.

Keywords: 3D printed PLA waste, pyrolysis, Kinetic analysis, TG-FTIR/GC-MS analysis