Multistage kinetic analysis of DMAA/MBAM polymer removal from gelcast ceramic parts using a multi-stage parallel...

This work aims to develop an effective method for investigating the multistage debinding kinetics and reaction mechanisms of removing N,N-dimethylacrylamide/N,N'-methylenebisacrylamide (DMAA/MBAM) polymer from gelcast ceramic parts. Thermogravimetry (TG) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) experiments were performed to investigate the thermal degradation characteristics and the main compounds produced during the pyrolysis of DMAA/MBAM polymer within green components. A multi-stage parallel reaction model (M-PRM) was proposed to separate the overlapping peaks in the dα/dT curves. The kinetic parameters (activation energy E and pre-exponential factor k ₀) of each substage were calculated using model-free methods (Flynn-Wall-Ozawa, Starink, Friedman and Kissinger-Akahira-Sunose) and an activation energy variable model. In addition, the most appropriate kinetic mechanism function f(α) of each substage was analyzed and discussed via Málek's procedure and the Šesták-Berggren (SB) model. The results showed that the DMAA/MBAM polymer burnout in green components can be divided into three substages through a three-stage parallel reaction model (3-PRM). The values of E (Friedman method) for substages 1 to 3 were E(α) = 139.862 - 110.481α + 156.161α ² - 88.714α ³ kJ mol^-1, E(α) = 160.791 + 152.496α - 236.906α ² + 163.724α ³ kJ mol^-1 and E(α) = 72.132 + 452.830α - 669.039α ² + 507.015α ³ kJ mol^-1, respectively. The average values of E showed an increasing tendency from substages 1 to 3, and a kinetic compensation effect was also observed between the E and k ₀ in each substage. The kinetic mechanism analysis revealed that the reaction mechanisms for substages 1 to 3 were f(α) = (1 - α)^0.668 α ^3.049(-ln(1 - α))^-3.874, f(α) = (1 - α)^0.700 α ^3.177(-ln(1 - α))^-3.962 and f(α) = (1 - α)^1.049 α ^-0.161(-ln(1 - α))^0.518, respectively. It is expected that the research results can be extended to investigate the multiplex debinding of binders or polymers for various colloidal molding techniques.