Characteristics of dual-curable blocked isocyanate with thermal radical initiator for low-temperature curing of automotive coatings

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

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)

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 languageEnglish
Pages (from-to)160-166
Number of pages7
JournalProgress in Organic Coatings
Volume125
DOIs
Publication statusPublished - 2018 Dec 1

Keywords

  • Automotive coatings
  • Dual-curable blocked isocyanate
  • Low-temperature curing
  • Radical reaction
  • TRI
  • Urethane reaction

ASJC Scopus subject areas

  • Chemical Engineering(all)
  • Surfaces, Coatings and Films
  • Organic Chemistry
  • Materials Chemistry

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