Effect of isocyanate crosslinkers blocked with amine derivatives on rheological and crosslinking characteristics of automotive clearcoats

Young Gun June, Kevin Injoe Jung, Tae Hee Lee, Miran Ha, Seung Man Noh, Hyun Wook Jung

Research output: Contribution to journalArticlepeer-review

Abstract

Isocyanate crosslinkers with blocking agents based on various amine derivatives were newly synthesized for automotive clearcoat applications. Amine-based blocking agents were prepared by varying the alkyl substituent attached on both sides of the main nitrogen atom (named DEA, DiPA, NtBEA, and NtBiA) to modify their deblocking feature in blocked isocyanates (BIs) and curing reaction under thermal curing conditions. Curing properties of clearcoats containing amine-based BIs were characterized at the normal curing temperature of 150°C and were compared with those by the commercialized BI, Desmodur® PL350. The dissociation ability of the amine-based BIs was interpreted using the density functional theory (DFT) simulation under their optimized geometric configurations. The urethane reaction between isocyanate group in BIs and hydroxyl group in a hydroxyl-functionalized polyol binder within clearcoats was confirmed from the OH stretching absorbance data via Fourier-transform infrared (FT-IR) spectrometer. The real-time cross-linking dynamics of various clearcoats with amine-based BIs were comprehensively investigated using rotational rheometer and rigid-body pendulum tester. The surface mechanical properties of fully-cured clearcoat films were measured by nano-indentation and nano-scratch testers to address the crosslinked network formation caused by amine-based BIs. It is demonstrated that the amine-based BIs could be favorably applied to thermal curing process of clearcoats, based on their reactivity and curing performance.

Original languageEnglish
Pages (from-to)37-43
Number of pages7
JournalKorea Australia Rheology Journal
Volume33
Issue number1
DOIs
Publication statusPublished - 2021 Feb

Keywords

  • amine-based blocking agents
  • automotive clearcoat
  • blocked isocyanates
  • curing dynamics
  • surface resistance
  • urethane crosslinking

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics

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