Reactivity and Curing Efficiency of Isocyanate Cross-linkers with Imidazole-Based Blocking Agents for Low-Temperature Curing of Automotive Clearcoats
For the application of low-temperature curing on automotive clearcoats, isocyanate cross-linkers blocked with imidazole derivatives were newly synthesized. The effect of the alkyl groups in the imidazole derivatives on the deblocking behavior and curing kinetics was investigated. The free isocyanate...
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doaj-c5df92833d43401b84c8ea35f14b19d72020-11-25T01:53:22ZengMDPI AGCoatings2079-64122020-10-011097497410.3390/coatings10100974Reactivity and Curing Efficiency of Isocyanate Cross-linkers with Imidazole-Based Blocking Agents for Low-Temperature Curing of Automotive ClearcoatsMoonhyun Choi0Maeng Gi Kim1Kevin Injoe Jung2Tae Hee Lee3Miran Ha4Woochan Hyung5Hyun Wook Jung6Seung Man Noh7Research Center for Green Fine Chemicals, Korea Research Institute of Chemical Technology (KRICT), Ulsan 44412, KoreaKCC Central Research Institute, Yongin-si, Gyeonggi-do 16891, KoreaDepartment of Chemical and Biological Engineering, Korea University, Seoul 02841, KoreaResearch Center for Green Fine Chemicals, Korea Research Institute of Chemical Technology (KRICT), Ulsan 44412, KoreaDepartment of Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, KoreaKCC Central Research Institute, Yongin-si, Gyeonggi-do 16891, KoreaDepartment of Chemical and Biological Engineering, Korea University, Seoul 02841, KoreaResearch Center for Green Fine Chemicals, Korea Research Institute of Chemical Technology (KRICT), Ulsan 44412, KoreaFor the application of low-temperature curing on automotive clearcoats, isocyanate cross-linkers blocked with imidazole derivatives were newly synthesized. The effect of the alkyl groups in the imidazole derivatives on the deblocking behavior and curing kinetics was investigated. The free isocyanate groups exposed by the deblocking of imidazole-based blocking agents were monitored by real-time Fourier-transform infrared spectroscopy. The bond dissociation energy, activation energy of deblocking, and H–N distance were interpreted through density functional theory simulation of various imidazole-based blocked isocyanates. To evaluate their applicability to automotive clearcoats, the synthesized imidazole-based blocked isocyanates were mixed with a polyol binder containing hydroxyl groups, and the clearcoat samples were cured at relatively low curing temperatures (100, 110, and 120 °C). The real-time storage modulus was measured using a rotational rheometer to elucidate the thermal curing dynamics by the blocking agents. In addition, the surface hardness of the cured clearcoat layers, which is affected by the chemical structure of the imidazole derivatives, was evaluated by nanoindentation test. In-depth analyses of the deblocking behaviors and thermal curing properties of clearcoats using imidazole-based blocked isocyanates demonstrated that the newly developed coating system could be suitably applied for the development of low-temperature curing technology.https://www.mdpi.com/2079-6412/10/10/974automotive clearcoatblocked isocyanateslow-temperature curingimidazole blocking agentcross-linking propertiesurethane reaction |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Moonhyun Choi Maeng Gi Kim Kevin Injoe Jung Tae Hee Lee Miran Ha Woochan Hyung Hyun Wook Jung Seung Man Noh |
spellingShingle |
Moonhyun Choi Maeng Gi Kim Kevin Injoe Jung Tae Hee Lee Miran Ha Woochan Hyung Hyun Wook Jung Seung Man Noh Reactivity and Curing Efficiency of Isocyanate Cross-linkers with Imidazole-Based Blocking Agents for Low-Temperature Curing of Automotive Clearcoats Coatings automotive clearcoat blocked isocyanates low-temperature curing imidazole blocking agent cross-linking properties urethane reaction |
author_facet |
Moonhyun Choi Maeng Gi Kim Kevin Injoe Jung Tae Hee Lee Miran Ha Woochan Hyung Hyun Wook Jung Seung Man Noh |
author_sort |
Moonhyun Choi |
title |
Reactivity and Curing Efficiency of Isocyanate Cross-linkers with Imidazole-Based Blocking Agents for Low-Temperature Curing of Automotive Clearcoats |
title_short |
Reactivity and Curing Efficiency of Isocyanate Cross-linkers with Imidazole-Based Blocking Agents for Low-Temperature Curing of Automotive Clearcoats |
title_full |
Reactivity and Curing Efficiency of Isocyanate Cross-linkers with Imidazole-Based Blocking Agents for Low-Temperature Curing of Automotive Clearcoats |
title_fullStr |
Reactivity and Curing Efficiency of Isocyanate Cross-linkers with Imidazole-Based Blocking Agents for Low-Temperature Curing of Automotive Clearcoats |
title_full_unstemmed |
Reactivity and Curing Efficiency of Isocyanate Cross-linkers with Imidazole-Based Blocking Agents for Low-Temperature Curing of Automotive Clearcoats |
title_sort |
reactivity and curing efficiency of isocyanate cross-linkers with imidazole-based blocking agents for low-temperature curing of automotive clearcoats |
publisher |
MDPI AG |
series |
Coatings |
issn |
2079-6412 |
publishDate |
2020-10-01 |
description |
For the application of low-temperature curing on automotive clearcoats, isocyanate cross-linkers blocked with imidazole derivatives were newly synthesized. The effect of the alkyl groups in the imidazole derivatives on the deblocking behavior and curing kinetics was investigated. The free isocyanate groups exposed by the deblocking of imidazole-based blocking agents were monitored by real-time Fourier-transform infrared spectroscopy. The bond dissociation energy, activation energy of deblocking, and H–N distance were interpreted through density functional theory simulation of various imidazole-based blocked isocyanates. To evaluate their applicability to automotive clearcoats, the synthesized imidazole-based blocked isocyanates were mixed with a polyol binder containing hydroxyl groups, and the clearcoat samples were cured at relatively low curing temperatures (100, 110, and 120 °C). The real-time storage modulus was measured using a rotational rheometer to elucidate the thermal curing dynamics by the blocking agents. In addition, the surface hardness of the cured clearcoat layers, which is affected by the chemical structure of the imidazole derivatives, was evaluated by nanoindentation test. In-depth analyses of the deblocking behaviors and thermal curing properties of clearcoats using imidazole-based blocked isocyanates demonstrated that the newly developed coating system could be suitably applied for the development of low-temperature curing technology. |
topic |
automotive clearcoat blocked isocyanates low-temperature curing imidazole blocking agent cross-linking properties urethane reaction |
url |
https://www.mdpi.com/2079-6412/10/10/974 |
work_keys_str_mv |
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1724991324012150784 |