Lecture note on Flame Surface Treatment

This review summarises flame surface treatment as a controlled thermal-oxidative method used to raise surface free energy and wettability of polymers, composites, metals and films for improved ink, paint and adhesive bonding. It describes the dual mechanisms of thermal desorption of weak boundary layers and mild oxidative functionalization by flame radicals, and it links these mechanisms to measurable endpoints such as reduced contact angle and XPS/FTIR-detected oxygenated groups. The paper compares system classes from simple atmospheric burners to forced-air, swirl-stabilized and micro-jet/multi-row designs, and it explains how fuel composition and equivalence ratio, flame temperature, standoff and dwell time determine radical pools, radiative heat flux, pollutant formation and the risk of thermal damage. CFD and DES modelling emerge as practical tools to design uniform burners and avoid hot spots, while QA via contact-angle mapping and occasional XPS/FTIR checks supports robust inline control. Industrial advantages include low capital and small footprint for high-speed web processing and reduced liquid waste, whereas limitations centre on narrow process windows for thermally sensitive substrates and emissions and safety constraints for hydrogen-enriched fuels. The review highlights trade-offs in burner selection and the need for emissions monitoring and hybrid treatment strategies to balance activation, throughput and environmental compliance.