Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10140023 | Progress in Organic Coatings | 2018 | 7 Pages |
Abstract
Dual-curable blocked isocyanate with a thermal radical initiator (BL-Tri-cHD) was designed and synthesized to perform low-temperature curing of automotive coatings. BL-Tri-cHD can simultaneously react with both unsaturated CC double bonds for free-radical polymerization and hydroxyl groups for the urethane reaction in hydroxyl-functionalized urethane methacrylate oligomers (HFUMO) under mild thermal curing conditions. The dual crosslinking behavior and mechanical properties of HFUMO-based coatings using BL-Tri-cHD were compared with those of a commercial blocked isocyanate thermal crosslinker (Desmodur® BL-PL350). The onset temperature for initiating cured by BL-Tri-cHD was about 68â°C, confirming faster crosslinking at relatively lower temperature than BL-PL350, which initiated curing at 140â°C. To quantitatively evaluate the properties of cured coatings, a nano-indentation was made in the surfaces of clearcoat films cured at 150â°C, 130â°C, and 120â°C. Films cured using BL-Tri-cHD and BL-PL350 at 150â°C exhibited similar indentation patterns. The indentation curves for the films with BL-Tri-cHD cured at lower curing temperatures such as 130â°C and 120â°C showed favorable penetration depth profiles similar to the sample cured at 150â°C, whereas the films with BL-PL350 cured below 150â°C had a less dense network structure, resulting in a deeper penetration depth than the sample cured at 150â°C. Therefore, we report that dual-curable BL-Tri-cHD demonstrates promising performance in automotive coating applications and possesses the ability to form highly crosslinked networks, even at low curing temperatures.
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Authors
Kevin Injoe Jung, Beomjin Kim, Dong Geun Lee, Tae-Hee Lee, Seo Yeon Choi, Jin Chul Kim, Seung Man Noh, Young Il Park, Hyun Wook Jung,