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 C[dbnd]C 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 68 °C, confirming faster crosslinking at relatively lower temperature than BL-PL350, which initiated curing at 140 °C. To quantitatively evaluate the properties of cured coatings, a nano-indentation was made in the surfaces of clearcoat films cured at 150 °C, 130 °C, and 120 °C. Films cured using BL-Tri-cHD and BL-PL350 at 150 °C exhibited similar indentation patterns. The indentation curves for the films with BL-Tri-cHD cured at lower curing temperatures such as 130 °C and 120 °C showed favorable penetration depth profiles similar to the sample cured at 150 °C, whereas the films with BL-PL350 cured below 150 °C had a less dense network structure, resulting in a deeper penetration depth than the sample cured at 150 °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.
Original language | English |
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Pages (from-to) | 160-166 |
Number of pages | 7 |
Journal | Progress in Organic Coatings |
Volume | 125 |
DOIs | |
Publication status | Published - 2018 Dec |
Bibliographical note
Publisher Copyright:© 2018 Elsevier B.V.
Copyright:
Copyright 2018 Elsevier B.V., All rights reserved.
Keywords
- Automotive coatings
- Dual-curable blocked isocyanate
- Low-temperature curing
- Radical reaction
- TRI
- Urethane reaction
ASJC Scopus subject areas
- General Chemical Engineering
- Surfaces, Coatings and Films
- Organic Chemistry
- Materials Chemistry