Evaluation of hindered amine light stabilisers and their N-chlorinated derivatives as antibacterial and antifungal additives for thermoset surface coatings
N-Halogenated amines or ‘halamines’ have attracted recent attention as potential biocides for materi-als and surface coatings application. Facile N-chlorination of the hindered amine light stabiliser (HALS)Tinuvin®770, bis-(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, was achieved by reaction with sodiumdichloroisocyanurate. The chlorinated product was incorporated into a polyester-based paint formulatedfor coil coating, applied to test panels and subjected to high temperature curing conditions characteristicof the coil coating process (55 s at 262◦C). Rapid detection of N-chlorinated Tinuvin®770 in the curedcoating was confirmed, using liquid extraction surface analysis-mass spectrometry, by the characteris-tic fragmentation patterns of the halamines observed upon collision-induced dissociation. Antimicrobialactivity of the coating was determined by testing against the bacterium Pseudomonas aeruginosa and thefungus Cladosporium sp., two organisms that are known to colonise both internal and external surfaces inbuilding and cladding applications. The activity of HALS and halamine containing coatings were comparedagainst a commercial product containing an antimicrobial additive as well as control surfaces withoutadditives. Significant activity against the bacterium, but not against the fungus was demonstrated forthe parent HALS and halamine containing coatings. The possibility of regeneration of the halamines wasalso tested and confirmed by mass spectrometry, post-chlorination of samples showed no significantdifferences in activity between corresponding pairs of samples.