MAGIC ANGLE C-13 NMR DETERMINATION OF THE FATE OF KETONE END GROUPS DURING PHOTOLYSIS OF CROSS-LINKED ACRYLIC COPOLYMERS

Ketone end groups formed during acrylate copolymerization are a main source of free radical formation during the initial stages of weathering in crosslinked coatings formulated with these copolymers. During weathering, the rate of formation of radicals changes. Other chromophores such as hydroperoxides are also observed. To better understand the photooxidation process, magic angle spinning C-13 NMR spectroscopy has been used to measure the change in concentration of ketone end groups in crosslinked acrylic copolymer coatings as a function of weathering time. A clear correlation has been established between ketone concentration, hydroperoxide concentration, and free radical formation rates in weathered coatings.