Dual-curable isocyanate crosslinking agents blocked by methacrylate-functionalized pyrazoles with lower curing temperature

Kim, Soeun; Hong, Jun Ui; Ha, Miran; Noh, Seung Man

doi:10.1016/j.porgcoat.2021.106501

Cited by 6 publications

(4 citation statements)

References 27 publications

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“…The cross-linking behavior of the clearcoats was verified using RPT under the same conditions as those used for rheometry measurements. − Crucially, the variation in the oscillation period of the pendulum is related to the cross-linking density and viscoelastic properties of cross-linked polymeric films . The oscillation periods observed during D-curing at 130 and 150 °C are shown in Figures a and b, respectively.…”

Section: Resultsmentioning

confidence: 96%

“…Dual-cross-linking systems combine the radical addition reactions of double bonds with urethane formation reactions, and they have been used to prepare automotive clearcoats. − Such systems exhibit high cross-linking efficiencies and show enhanced material properties. Crucially, because the radical reactions do not chemically interfere with the formation of the urethane network, the two reactions can proceed simultaneously; thus, the loosely formed urethane network is supplemented by the additional network formed via radical reactions under relatively low-temperature curing conditions (<150 °C).…”

Section: Introductionmentioning

confidence: 99%

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Controlled Dual Cross-Linking of Radical and Urethane Reactions via Vinyl Protection for High-Performance Coating Materials

Kim

Park

et al. 2023

ACS Appl. Polym. Mater.

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Herein, we present a method to control the dual cross-linking of radical and urethane reactions for the enhanced polymer coatings by protecting and deprotecting vinyl functionalities using sulfoxide chemistry. We exploited this chemistry to produce highly cross-linked polymers suitable for use as protective coatings. Briefly, dually cross-linkable polymers with sulfoxide-protected vinyl and hydroxyl functionalities were synthesized. Subsequently, thermal curing resulted in the reaction of the hydroxyl functionalities with isocyanate cross-linkers to form urethane cross-links. At the same time, the sulfoxide-protected vinyl functionalities were deprotected and participated in vinyl cross-linking via radical addition reactions. The real-time monitoring of the dual-cross-linking behavior and mechanical properties of the cross-linked films revealed enhanced cross-linking when the reaction rate of the vinyl functionalities was retarded during thermal curing. Thus, this work provides insights into methods of enhancing dual-cross-linking reaction efficiency, and the developed system has applications for the low-temperature preparation of automotive clearcoats.

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Section: Resultsmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Controlled Dual Cross-Linking of Radical and Urethane Reactions via Vinyl Protection for High-Performance Coating Materials

Kim

Park

et al. 2023

ACS Appl. Polym. Mater.

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“…This effect causes an uneven charge distribution within the group, resulting in carbon-positive atoms at the nucleophilic center, giving the −NCO group high reactivity (Figure S2). − By undergoing blocking-deblocking reactions (Figures S3 and S4), the material can further react with chain extenders, increasing the degree of polymerization and enhancing the overall performance of the material. This process effectively combines UV-thermal curing methods and significantly improves the material's mechanical properties. − …”

Section: Introductionmentioning

confidence: 99%

Synthesis and Characterization of Silicon-Modified Polyurethane Acrylate for UV-Thermal Dual Curing in Three Dimensional Printing

Wu,

Ding,

Yuan

et al. 2024

ACS Appl. Polym. Mater.

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Single UV-curing silicone-modified polyurethane acrylate materials have limitations, such as low molecular polymerization and weak mechanical properties compared to thermal-curing materials. This experiment synthesized a polyurethane prepolymer coated with isocyanate groups using hydroxyl polyether silicone oil (PDMS) and diisocyanate. tert-Butylaminoethyl methacrylate (t-BAEMA) was then utilized to create a silicon-modified polyurethane acrylate (SiBPUA) prepolymer with heat-unstable urea and photosensitive groups. This prepolymer was incorporated into photosensitive resin materials and processed through 3D DLP 3D printing. Upon heating, the −NCO group regenerated, and the chain extender underwent a secondary curing reaction, increasing molecular weight and improving performance. The study investigated the impact of different reactants on SiBPUA properties, deblocking temperature, optimal curing temperature, and enhancement of UV-curing materials through thermal curing. The results revealed that the use of isophorone diisocyanate (IPDI), 4,4′-diaminodicyclohexylmethane (PACM), and methyl methacrylate (MMA) resulted in the best mechanical properties. Furthermore, UV-thermal dual curing significantly enhanced tensile strength (12.5 MPa) and elongation at break (219.5%), broadening the application potential of UV-curing 3D printing materials.

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“…For example, the slow diffusion of the blocking group through the reactive medium could result in slow curing. 22 Soeun Kim et al 23 designed and synthesized methacrylate functionalized pyrazole derivatives as blocking agent of HDI trimers. The results show that the novel pyrazole blocking agent has solvent affinity and low steric resistance.…”

Section: Introductionmentioning

confidence: 99%

Influence of the melting point on the deblocking reaction of methyl ethyl ketoxime‐blocked aromatic polyisocyanates

Zhai

Meng

et al. 2022

J of Applied Polymer Sci

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Blocked polyisocyanates are used in single component (1 K) water‐based and powder coatings to simplify coating synthesis and reduce waste. However, the relationship between the melting point and deblocking behavior of blocked polyisocyanates is not clear. We aim to determine the influence of the melting temperature on the deblocking of methyl ethyl ketoxime (MEKO)‐blocked aromatic polyisocyanates. A toluene‐2,4‐diisocyanate trimer grafted with different mass ratios of methoxypolyethylene glycol (MPEG) is used to achieve compounds with different melting points and is blocked with MEKO. The deblocking behaviors of the polymers are investigated using Fourier transform infrared spectroscopy, differential scanning calorimetry, scanning electron microscopy, and thermogravimetric analysis. The results show that the deblocking temperature and average activation energy of the blocked polyisocyanates decrease with increase in melting point. Further, MEKO is more likely to be lost from blocked polyisocyanates having lower melting points. Furthermore, polyacrylic resins cured with blocked polyisocyanates having low melting points exhibit better properties than those having high melting points. The results reveal that the reduction in melting point induced by grafting with MPEG can significantly reduce the deblocking temperature of blocked polyisocyanates. The improvements in these properties may help achieve the low‐temperature crosslinking of blocked polyisocyanates for coating technologies.

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Dual-curable isocyanate crosslinking agents blocked by methacrylate-functionalized pyrazoles with lower curing temperature

Cited by 6 publications

References 27 publications

Controlled Dual Cross-Linking of Radical and Urethane Reactions via Vinyl Protection for High-Performance Coating Materials

Controlled Dual Cross-Linking of Radical and Urethane Reactions via Vinyl Protection for High-Performance Coating Materials

Synthesis and Characterization of Silicon-Modified Polyurethane Acrylate for UV-Thermal Dual Curing in Three Dimensional Printing

Influence of the melting point on the deblocking reaction of methyl ethyl ketoxime‐blocked aromatic polyisocyanates

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