Enhanced thermal decomposition kinetics of poly(lactic acid) sacrificial polymer catalyzed by metal oxide nanoparticles

Abstract

Poly Lactic Acid (PLA) has been used as a sacrificial polymer in the fabrication of battery separators and can be employed in 0D–3D Vaporization of a Sacrificial Component (VaSC) fabrication. In this study, 1 wt% PLA/Fe₂O₃, PLA/CuO and PLA/Bi₂O₃ composites are prepared by solvent evaporation casting. Scanning Electron Microscopy (SEM) images indicate that the embedded nanoparticles are well dispersed in the polymer matrix and X-ray diffraction (XRD) verifies the crystallinity of these Metal Oxides (MOs). Thermal stability analysis of the PLA and PLA/MO composites is performed using a thermogravimetric analyzer (TGA) and Differential Scanning Calorimeter (DSC). The overall heat of combustion is measured by Microscale Combustion Calorimetry (MCC) and is found to be insensitive to the presence of nanoparticles. The overall catalytic effects of the three metal oxides have the following trend: Bi₂O₃ > Fe₂O₃ > CuO ≈ inert material. The PLA/Bi₂O₃ decomposition onset temperature (T_5%) and maximum mass loss decomposition temperature (T_max) are lowered by approximately 75 K and 100 K respectively compared to the neat PLA. The as-synthesized Bi₂O₃ is identified as the most effective additive among those proposed in the literature to catalyze the PLA thermal decomposition process. A numerical pyrolysis modeling tool, ThermaKin, is utilized to analyze thermogravimetric data of all the PLA/MOs and to produce a description of the decomposition kinetics, which can be utilized for modeling of thermal vaporization of these sacrificial materials.