Effect of urethane crosslinking by blocked isocyanates with Pyrazole-based blocking agents on rheological and mechanical performance of clearcoats

Young Gun June; Kevin Injoe Jung; Moonhyun Choi; Tae Hee Lee; Seung Man Noh; Hyun Wook Jung

doi:10.3390/coatings10100961

Effect of urethane crosslinking by blocked isocyanates with Pyrazole-based blocking agents on rheological and mechanical performance of clearcoats

Young Gun June, Kevin Injoe Jung, Moonhyun Choi, Tae Hee Lee, Seung Man Noh, Hyun Wook Jung

Research output: Contribution to journal › Article › peer-review

16 Citations (Scopus)

Abstract

A novel blocked isocyanate crosslinker was synthesized, and its applicability was investigated for the low-temperature curing of automotive clearcoats. Various pyrazole derivatives were prepared as blocking agents in isocyanate crosslinkers, which strongly affect the deblocking and curing properties of the urethane-bonded coating systems. The thermal curing properties of clearcoat samples containing a pyrazole-based blocked isocyanate crosslinker and polyol resin were characterized under two different temperature conditions (120 and 150^◦ C). The decrease in the amount of hydroxyl groups in the polyol before and after curing was expressed by the change in OH stretching frequency in the Fourier transform infrared (FT-IR) spectra. The real-time rheological storage moduli of the bulk clearcoat mixtures were measured via a rotational rheometer to determine the effect of pyrazole-based blocking agents on the curing dynamics. In addition, a rigid-body pendulum tester (RPT) was employed to investigate the curing behavior in the thin film form. The nano-indentation and the nano-scratch tests were conducted to examine the surface hardness and scratch resistance characteristics of the cured clearcoat films. The results show that a low-temperature curing system of clearcoats can be realized by tuning the curing temperature and reactivity of isocyanate crosslinkers blocked with pyrazole-based substituents.

Original language	English
Article number	961
Pages (from-to)	1-11
Number of pages	11
Journal	Coatings
Volume	10
Issue number	10
DOIs	https://doi.org/10.3390/coatings10100961
Publication status	Published - 2020 Oct

Bibliographical note

Funding Information:
Funding: This study was supported by the Ministry of Trade, Industry and Energy (MOTIE, Korea) under Industrial Technology Innovation Programs (Grant Nos. 10067706 and 20010256).

Publisher Copyright:
© 2020 by the authors. Licensee MDPI, Basel, Switzerland.

Keywords

Automotive clearcoat
Blocked isocyanates
Crosslinking dynamics
Low-temperature curing
Pyrazole blocking agents
Surface resistance
Urethane reaction

ASJC Scopus subject areas

Surfaces and Interfaces
Surfaces, Coatings and Films
Materials Chemistry

Access to Document

10.3390/coatings10100961

Cite this

@article{958ead01eb154c658d8866b4fa74d9d1,

title = "Effect of urethane crosslinking by blocked isocyanates with Pyrazole-based blocking agents on rheological and mechanical performance of clearcoats",

abstract = "A novel blocked isocyanate crosslinker was synthesized, and its applicability was investigated for the low-temperature curing of automotive clearcoats. Various pyrazole derivatives were prepared as blocking agents in isocyanate crosslinkers, which strongly affect the deblocking and curing properties of the urethane-bonded coating systems. The thermal curing properties of clearcoat samples containing a pyrazole-based blocked isocyanate crosslinker and polyol resin were characterized under two different temperature conditions (120 and 150◦ C). The decrease in the amount of hydroxyl groups in the polyol before and after curing was expressed by the change in OH stretching frequency in the Fourier transform infrared (FT-IR) spectra. The real-time rheological storage moduli of the bulk clearcoat mixtures were measured via a rotational rheometer to determine the effect of pyrazole-based blocking agents on the curing dynamics. In addition, a rigid-body pendulum tester (RPT) was employed to investigate the curing behavior in the thin film form. The nano-indentation and the nano-scratch tests were conducted to examine the surface hardness and scratch resistance characteristics of the cured clearcoat films. The results show that a low-temperature curing system of clearcoats can be realized by tuning the curing temperature and reactivity of isocyanate crosslinkers blocked with pyrazole-based substituents.",

keywords = "Automotive clearcoat, Blocked isocyanates, Crosslinking dynamics, Low-temperature curing, Pyrazole blocking agents, Surface resistance, Urethane reaction",

author = "June, {Young Gun} and Jung, {Kevin Injoe} and Moonhyun Choi and Lee, {Tae Hee} and Noh, {Seung Man} and Jung, {Hyun Wook}",

note = "Funding Information: Funding: This study was supported by the Ministry of Trade, Industry and Energy (MOTIE, Korea) under Industrial Technology Innovation Programs (Grant Nos. 10067706 and 20010256). Publisher Copyright: {\textcopyright} 2020 by the authors. Licensee MDPI, Basel, Switzerland.",

year = "2020",

month = oct,

doi = "10.3390/coatings10100961",

language = "English",

volume = "10",

pages = "1--11",

journal = "Coatings",

issn = "2079-6412",

publisher = "Multidisciplinary Digital Publishing Institute (MDPI)",

number = "10",

}

TY - JOUR

T1 - Effect of urethane crosslinking by blocked isocyanates with Pyrazole-based blocking agents on rheological and mechanical performance of clearcoats

AU - June, Young Gun

AU - Jung, Kevin Injoe

AU - Choi, Moonhyun

AU - Lee, Tae Hee

AU - Noh, Seung Man

AU - Jung, Hyun Wook

N1 - Funding Information: Funding: This study was supported by the Ministry of Trade, Industry and Energy (MOTIE, Korea) under Industrial Technology Innovation Programs (Grant Nos. 10067706 and 20010256). Publisher Copyright: © 2020 by the authors. Licensee MDPI, Basel, Switzerland.

PY - 2020/10

Y1 - 2020/10

N2 - A novel blocked isocyanate crosslinker was synthesized, and its applicability was investigated for the low-temperature curing of automotive clearcoats. Various pyrazole derivatives were prepared as blocking agents in isocyanate crosslinkers, which strongly affect the deblocking and curing properties of the urethane-bonded coating systems. The thermal curing properties of clearcoat samples containing a pyrazole-based blocked isocyanate crosslinker and polyol resin were characterized under two different temperature conditions (120 and 150◦ C). The decrease in the amount of hydroxyl groups in the polyol before and after curing was expressed by the change in OH stretching frequency in the Fourier transform infrared (FT-IR) spectra. The real-time rheological storage moduli of the bulk clearcoat mixtures were measured via a rotational rheometer to determine the effect of pyrazole-based blocking agents on the curing dynamics. In addition, a rigid-body pendulum tester (RPT) was employed to investigate the curing behavior in the thin film form. The nano-indentation and the nano-scratch tests were conducted to examine the surface hardness and scratch resistance characteristics of the cured clearcoat films. The results show that a low-temperature curing system of clearcoats can be realized by tuning the curing temperature and reactivity of isocyanate crosslinkers blocked with pyrazole-based substituents.

AB - A novel blocked isocyanate crosslinker was synthesized, and its applicability was investigated for the low-temperature curing of automotive clearcoats. Various pyrazole derivatives were prepared as blocking agents in isocyanate crosslinkers, which strongly affect the deblocking and curing properties of the urethane-bonded coating systems. The thermal curing properties of clearcoat samples containing a pyrazole-based blocked isocyanate crosslinker and polyol resin were characterized under two different temperature conditions (120 and 150◦ C). The decrease in the amount of hydroxyl groups in the polyol before and after curing was expressed by the change in OH stretching frequency in the Fourier transform infrared (FT-IR) spectra. The real-time rheological storage moduli of the bulk clearcoat mixtures were measured via a rotational rheometer to determine the effect of pyrazole-based blocking agents on the curing dynamics. In addition, a rigid-body pendulum tester (RPT) was employed to investigate the curing behavior in the thin film form. The nano-indentation and the nano-scratch tests were conducted to examine the surface hardness and scratch resistance characteristics of the cured clearcoat films. The results show that a low-temperature curing system of clearcoats can be realized by tuning the curing temperature and reactivity of isocyanate crosslinkers blocked with pyrazole-based substituents.

KW - Automotive clearcoat

KW - Blocked isocyanates

KW - Crosslinking dynamics

KW - Low-temperature curing

KW - Pyrazole blocking agents

KW - Surface resistance

KW - Urethane reaction

UR - http://www.scopus.com/inward/record.url?scp=85093824782&partnerID=8YFLogxK

U2 - 10.3390/coatings10100961

DO - 10.3390/coatings10100961

M3 - Article

AN - SCOPUS:85093824782

SN - 2079-6412

VL - 10

SP - 1

EP - 11

JO - Coatings

JF - Coatings

IS - 10

M1 - 961

ER -

Effect of urethane crosslinking by blocked isocyanates with Pyrazole-based blocking agents on rheological and mechanical performance of clearcoats

Abstract

Bibliographical note

Keywords

ASJC Scopus subject areas

Access to Document

Other files and links

Fingerprint

Cite this