Urethane coatings, photoinitiation rate

By contrast to melamine cross-linked coatings, the evolution of photoinitiation rates in urethane cross-linked coatings is very different with photoinitiation rates in weathered coatings tending to increase with exposure time, Fig. 13. ° " For coatings... 

Fig. 13. Photoinitiation rate for acrylic urethane coatings and polyester urethane as a function of near-ambient weathering time. O-Copolymer A D-Copolymer N A- polyester I. The filled symbols indicate the addition of a 320-nm filter to the near ambient exposure. (See Refs. 10...

It has been found that the photoinitiation rates of acrylic urethane and acrylic melamine coatings depend primarily upon the nature and concentration of chromophores that are incorporated into the acrylic copolymer during polymerization [731, 732]. The primary chromophores for conventional polymerization (peroxide and hydroperoxide initiators in ketone solvents) are ketonic end-groups [359, 735]. 

The spin traps technique was applied to the study of photoinitiation of polymer (coatings based on polyester-urethanes) degradation [730,731, 733, 734]. There is excellent qualitative correlation between the rate of... 

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