Study of catalytic infrared curing powder coating technology: experiments and modelling

Abstract

Catalytic combustion can effectively and cleanly convert the chemical energy of fossil fuels into infrared radiation energy. However, there is little research on the use of this technology to cure powder coatings. In order to carry out the application and theoretical study of this technology, a catalytic infrared heating equipment based on a Pt/Al2O3 noble metal catalyst was designed, constructed, and tested. Experimental and modeling studies were carried out in this study using Polyester/TGIC and GMA/DDDA powder coating systems, respectively.
Based on a literature review and analysis, a feasibility and heat transfer
process study was first carried out using Polyester/TGIC powder coatings. The optimal curing parameters for the catalytic infrared curing process for powder coatings were determined via experiments at 220 °C for 3 min and 230 °C for 2 min. As the curing temperature increased and the curing time increased, the mechanical properties of the coating were found to improve. However, the gloss of the coating was reduced and the color darkened. A one-dimensional heat transfer model was developed to investigate the heat transfer process for powder coatings. This study introduced an internal heat source for the first time, and the heat transfer process for polyester-based powder coatings with different substrate thicknesses was numerically simulated. The numerical simulations demonstrated that the efficiency of the heat transfer between the catalytic infrared gas supply and the coating surface was 0.4. When the substrate thickness was 1 mm, the coating was most rapidly cured at 230 °C. When the substrate thickness was ≥2 mm, the most rapid curing occurred at 220 °C.
Next, the curing process study was conducted using GMA/DDDA System
powder coatings. Fourier-transformed infrared (FT-IR) spectroscopy is employed to record the concentration of epoxide groups with respect to time under different temperature conditions, with the reaction conducted under IR radiation. The resulting data were then fitted by the Levenberg–Marquardt
algorithm using MATLAB software to obtain the kinetic parameters, namely
the rate constant (k), catalytic constants (n and m), reaction activation energy
(E), and the pre-exponential factor (A) of the curing reaction. Additionally, this study proposed a new concept: the “photo-thermal synergistic effect” of infrared curing and its evaluation criteria using a dimensionless quantity, i.e., photo-thermal synergistic index ( PTSI). Incredibly, this index integrates the impact of IR curing technology on two aspects: the curing process and the properties of the cured product.
Overall, this work contributes to advancing the understanding and application of catalytic infrared curing, offering a theoretical and experimental basis for industrial-scale implementation.

Date of Award	13 Jul 2025
Original language	English
Awarding Institution	University of Nottingham
Supervisor	Isaac Yu Fat Lun (Supervisor), Runqi Liang (Supervisor) & Zhiang Zhang (Supervisor)