FT-IR and Thermal-Mechanical Cure Characterization of Blocked Isocyanate Containing Coatings

Carlson, G. M.; Neag, C. M.; Kuo, Chao‐Yin; Provder, Theodore

doi:10.1007/978-1-4684-7776-4_9

Cited by 9 publications

(7 citation statements)

References 2 publications

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“…220 °C the modulus starts to increase, suggesting the occurrence of side reactions at these higher temperatures. High temperature side reactions are well-known in isocyanate chemistry and are known to effectively generate new (irreversible) chemical cross-links. , As mentioned previously, a similar behavior was observed when catalyst (DBTDL) was used in the curing reaction (Figures S3 and S4); catalyst is also known to aid the isocyanate side reactions at lower temperatures and increase the cross-linking density …”

Section: Resultssupporting

confidence: 69%

“…High temperature side reactions are well-known in isocyanate chemistry and are known to effectively generate new (irreversible) chemical crosslinks. 47,67 As mentioned previously, a similar behavior was observed when catalyst (DBTDL) was used in the curing reaction (Figures S3 and S4); catalyst is also known to aid the isocyanate side reactions at lower temperatures and increase the cross-linking density. 67 To better understand what is happening in these DCNs temperature-dependent FTIR studies were carried out.…”

Section: Initial Studies Focused On a Stoichiometric Mixture Of 3hdi ...supporting

confidence: 73%

“…47,67 As mentioned previously, a similar behavior was observed when catalyst (DBTDL) was used in the curing reaction (Figures S3 and S4); catalyst is also known to aid the isocyanate side reactions at lower temperatures and increase the cross-linking density. 67 To better understand what is happening in these DCNs temperature-dependent FTIR studies were carried out. Of particular use in these experiments is the out-of-phase stretching mode of the NCO group which appears as a strong absorption centered at ν = 2270 cm −1 and does not overlap with the absorption bands of other major functional groups (such as CO or N−H) in polyurethane/polyalkylurea materials.…”

Section: Initial Studies Focused On a Stoichiometric Mixture Of 3hdi ...supporting

confidence: 73%

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Effect of Sterics and Degree of Cross-Linking on the Mechanical Properties of Dynamic Poly(alkylurea–urethane) Networks

2017

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Dynamic covalent networks are polymer networks that contain a dynamic covalent bond which allows them to be reprocessable, remoldable, and recyclable as well as exhibit crack healing or stress-relaxation properties. A key component of these materials is the nature of the dynamic covalent bond, which in addition to chemical composition and architecture can be used to dramatically alter the physical properties of these networks. The aim of this study is to understand the impact of steric hindrance of N-alkyl substituents and network connectivity in poly(alkylurea− urethane) dynamic network films. In these materials, the dynamic bond is the hindered alkyl urea moiety, whose dynamic behavior is dictated by the sterics of the alkyl substituent. Networks were prepared by the noncatalyzed curing reaction of aminoethanol compounds of varying substituents with a trifunctional isocyanate cross-linker and varying amounts of a monofunctional capping agent. Thermomechanical properties and FTIR studies show the impact of hindered urea bond sterics on the reaction conversion, network connectivity, and therefore the relaxation of the dynamic networks. Stress relaxation analysis show the vitrimer-like behavior of these dynamic networks only when the degree of cross-linking is maintained by high reaction conversion (high equilibrium constant of the dynamic bond). These results give some insights into the design and properties of dynamic covalent networks and how the nature of dynamic bonds can be used to impact their properties.

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Section: Resultssupporting

confidence: 69%

Section: Initial Studies Focused On a Stoichiometric Mixture Of 3hdi ...supporting

confidence: 73%

Section: Initial Studies Focused On a Stoichiometric Mixture Of 3hdi ...supporting

confidence: 73%

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Effect of Sterics and Degree of Cross-Linking on the Mechanical Properties of Dynamic Poly(alkylurea–urethane) Networks

2017

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“…Organotin catalysts in PEPU formulations can reduce the starting temperature of the unblocking process of blocked IPDI isocyanates, 11,12 and can ease the progress of Reaction 2, shown in above scheme, impacting further on the unlocking reaction of blocked isocyanates. In the PEPU01 coating system, several factors would be expected to influence the unblocking of the MEKO-blocked isocyanate in solution during heating.…”

Section: Thermal Studies Of Meko-blocked Isocyanatementioning

confidence: 98%

The behavior of MEKO-blocked isocyanate compounds in aluminum flake pigmented, polyester–polyurethane can coating systems

Jiang

Driffield²,

Bradley³

et al. 2009

J Coat Technol Res

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Information is given concerning the curing characteristics of polyester-polyurethane (PEPU)-based food can coatings and the analysis of the free isocyanate by-products. The behavior of a methyl ethyl ketoxime (MEKO)-blocked isocyanate on heating was studied using thermal analytical techniques. Following this, the curing behavior of a PEPU-based can coating (PEPU01 that contained an aluminum flake pigment) and the MEKO-blocked isocyanate was investigated. A study of the unblocking of the MEKO-blocked isocyanate in the PEPU01 can coatings was undertaken with respect to the migration potential of any residualfree isocyanate compounds that could migrate from the cured PEPU can coatings to the surrounding medium (e.g., foodstuffs).

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“…Provder and coworkers studied the blocked isocyanate cure reaction in nonisothermal conditions 10–13. But, in practical point of view, it is very important to study the course of the reaction with respect to time in isothermal conditions.…”

Section: Resultsmentioning

confidence: 99%

Cure‐reaction kinetics of amine‐blocked polyisocyanates with alcohol using hot‐stage Fourier transform infrared spectroscopy

Sankar

Nasar

2008

J of Applied Polymer Sci

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Cure reaction between a series of N-methylaniline-blocked polyisocyanates, based on 4,4 0 -methylenebis(phenyl isocyanate), poly(tetrahydrofuran) and several substituted N-methylanilines, and n-decanol has been studied. The solid-state isothermal cure reaction was carried out using hot-stage FTIR spectroscopy, in the temperature range of 125-1458C. The urea carbonyl absorption band of blocked polyisocyanate moiety was used to monitor the conversion of blocked polyisocyanate into polyurethane. Kinetic and thermodynamic parameters were calculated using normalized conversion curves. The overall order of cure reaction, for each of the blocked polyisocyanates was found to be first order. Based on the results of kinetics and reaction conditions used in this study, the elimination-addition (S N 1 ) mechanism was suggested for the cure reaction between N-methylaniline-blocked polyisocyanates and n-decanol. The effect of substituents present in the blocking agents on the cure reaction of N-methylaniline-blocked polyisocyanates was investigated and found that the cure reaction of N-methylaniline-blocked polyisocyanates was retarded by electron-donating substituents and facilitated by electron withdrawing substituents. The observed high negative entropy of activation value supports the formation of a four-centered, intramolecularly hydrogen-bonded ring structure during transition state of the cure reaction.

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FT-IR and Thermal-Mechanical Cure Characterization of Blocked Isocyanate Containing Coatings

Cited by 9 publications

References 2 publications

Effect of Sterics and Degree of Cross-Linking on the Mechanical Properties of Dynamic Poly(alkylurea–urethane) Networks

Effect of Sterics and Degree of Cross-Linking on the Mechanical Properties of Dynamic Poly(alkylurea–urethane) Networks

The behavior of MEKO-blocked isocyanate compounds in aluminum flake pigmented, polyester–polyurethane can coating systems

Cure‐reaction kinetics of amine‐blocked polyisocyanates with alcohol using hot‐stage Fourier transform infrared spectroscopy

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