Innovative iodonium initiators for curing prepreg composite materials via photoinduced frontal polymerization

How to Cost-Effectively, Safely, and Efficiently Patch a Pipeline, Repair a Ship, or Fix an Aircraft?

Everyday items, buildings, installations, machinery, and vehicles rely heavily on composite materials. However, curing composite materials to achieve structural properties typically involves cationic polymerization - a process traditionally driven by thermal reactions inside industrial ovens. This standard approach subjects materials to elevated temperatures for several hours, resulting in substantial energy consumption. Filip Petko from Tadeusz Kościuszko Cracow University of Technology is addressing this inefficiency by developing novel initiators for photoinduced cationic frontal polymerization. Funded by the European Funds for a Modern Economy 2021 - 2027 (FENG) program under the Proof of Concept action implemented by the Foundation for Polish Science (FNP), his research explores dual-activity initiators to streamline composite curing.

"Curing composites via photochemical reactions requires significantly less time - seconds rather than hours," explains Filip Petko. "This method is particularly useful in hard-to-reach locations, such as pipelines or sewers undergoing trenchless rehabilitation. Uncured material is introduced, properly distributed, and then cured on-site. High-power lamps - typically mercury-vapor lamps - are used to trigger curing. While these lamps still consume notable energy, deploying a light source into confined spaces is far easier and safer than heating an entire conduit with steam or hot water, which carries severe risk of thermal injuries and operational accidents."

Conventional photochemical composite curing is generally limited to thin layers, making thick-section fabrication inefficient and economically unviable. Cationic frontal polymerization offers a solution: applying a localized trigger (light or heat) generates a self-sustaining thermal front that propagates through the entire material volume. To sustain this propagation front effectively and produce reliable mechanical properties over larger areas, current systems require two separate components - a photochemical initiator to trigger the front and a thermal initiator to sustain it. However, using multiple chemical initiators introduces potential environmental and biological hazards.

"In my prior research, I synthesized iodonium salts exhibiting dual photochemical and thermochemical activity. Through this Proof of Concept project, I aim to verify their performance as single-component initiators for frontal polymerization. Validating this hypothesis eliminates the need for a secondary initiator, lowering formulation costs while reducing environmental and health footprints," says Petko. He notes that fiber-reinforced composite repair systems are vital for rapid, localized interventions - including trenchless repairs of leaking gas or water mains, structural maintenance of inaccessible building elements, component replacements in aerospace, and emergency maritime repairs at sea. "I foresee the fiber-reinforced composite manufacturing industry shifting toward frontal polymerization, as it presents clear advantages over traditional curing methods."

Filip Petko graduated from the Faculty of Chemistry at Jagiellonian University, specializing in photochemistry and optical spectroscopy. His interest in natural and artificial photosynthesis led to a Master's thesis on photocatalytic carbon dioxide reduction under the Foundation for Polish Science (FNP) TEAM program. During his studies, he completed research internships at the Jerzy Haber Institute of Catalysis and Surface Chemistry (PAS), the Institute of Physics (PAS), and the Jagiellonian Centre for Experimental Therapeutics (JCET). At the Institute of Physics (PAS), he contributed to the FNP HOMING PLUS project focused on de novo designed photosynthetic proteins. Currently, Filip Petko, M.Sc., holds positions at Tadeusz Kościuszko Cracow University of Technology and Photo High Technologies.