Studies of model urethane reactions and cure in polyurethanes by UV absorption and fluorescence spectroscopy

Huang, Xiao; Yu, Weiching; Sung, Chong Sook Paik

doi:10.1021/ma00204a007

Cited by 24 publications

(25 citation statements)

References 4 publications

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“…The apparent activation energy obtained for the MDI-butan-1-ol reaction is about 20 kJ/mol. This value is close to those obtained by Huang et al (17 kJ/mol) 17 and Sun and Sung (13 kJ/mol). 19 (The pseudo first-order rate constant values for the MDI-alcohol reactions can be found in the Supporting Information.…”

Section: Article Wileyonlinelibrarycom/appsupporting

confidence: 92%

“…However, previous experimental works, published on MDI-alcohol reactions, delivered contradictive results with respect of the values of k 1 ' to k 2 '. Huang et al 17 and Sun and Sung 19 found that k 1 '/k 2 ' 1, which is in good agreement with the theoretical expectation. Other authors 16,23 reported a value of approximately 1.5 for k 1 '/k 2 ' which is in accordance with our present results.…”

Section: Article Wileyonlinelibrarycom/appsupporting

confidence: 84%

“…Thus, to compare the reactivities of different diisocyanates toward alcohols is a difficult task because of the lack of finding the same experimental conditions for the diisocyanates to be compared. Furthermore, various experimental tools ranging from dilatometry and titration of the free isocyanate groups 11,22,24 to instrumental methods including liquid chromatography, 16 UVVis and fluorescence spectroscopy 17,19 as well as FT-IR spectroscopy 30 are being used for monitoring the isocyanate-alcohol reactions.…”

Section: Introductionmentioning

confidence: 99%

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New insight into the kinetics of diisocyanate‐alcohol reactions by high‐performance liquid chromatography and mass spectrometry

Nagy

Antal

Czifrák

et al. 2015

J of Applied Polymer Sci

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The uncatalyzed reactions of 2,4-TDI (2,4-toluenediisocyanate) and MDI (4,4 0 -diphenylmethane-diisocyanate) with alcohols including butan-1-ol, butan-2-ol, diethylene glycol monomethylether (DEGME) were studied by high-performance liquid chromatography (HPLC) and electrospray ionization mass spectrometry (ESI-MS). The reactions were carried out at different temperatures from 22 C to 75 C using high molar ratios of alcohols to diisocyanates. It was found that the first isocyanate group of the MDI reacts about 1.5 times faster with the alcohols than the second one. The relative reactivities of the isocyanate groups (para and ortho) of 2,4-TDI as a function of the temperature was also deduced. From the temperature dependence of the rate constants the apparent activation energies were determined. Furthermore, the dependence of the apparent rate constant on the concentration of alcohols was also investigated and a mechanism was proposed for the reaction of diisocyanates with alcohols.

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Section: Article Wileyonlinelibrarycom/appsupporting

confidence: 92%

Section: Article Wileyonlinelibrarycom/appsupporting

confidence: 84%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

New insight into the kinetics of diisocyanate‐alcohol reactions by high‐performance liquid chromatography and mass spectrometry

Nagy

Antal

Czifrák

et al. 2015

J of Applied Polymer Sci

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“…One of the crucial parameters in these syntheses is the reactivity of the isocyanate groups toward the polyols. Thus, large efforts have been devoted so far to study the reaction kinetics of industrially important isocyanates including, e.g., 4,4′‐diphenylmethane‐diisocyanate (4,4′‐MDI) , toluene‐diisocyanete (TDI) , and hexamethylene diisocyanates with various alcohols using different reaction conditions and monitoring methods such as titration , UV–vis photometry combined with high‐performance liquid chromatography (HPLC) , fluorescence spectroscopy , and mass spectrometry . It is now generally accepted that aromatic isocyanates have higher reactivity than that of the aliphatic ones, and they are used in many polyurethane formulations.…”

Section: Introductionmentioning

confidence: 99%

Kinetics of Uncatalyzed Reactions of 2,4′- and 4,4′-Diphenylmethane-Diisocyanate with Primary and Secondary Alcohols

Nagy

Kuki

et al. 2017

Int. J. Chem. Kinet.

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The kinetics of the uncatalyzed reaction of an industrially important 50/50 blend of isomers of 4,4′‐diphenylmethane‐diisocyanate (4,4‐MDI) and 2,4′‐diphenylmethane‐diisocyanate (2,4′‐MDI) with primary and secondary alcohols was studied using high‐performance liquid chromatography coupled with photodiode array detector. The alcohols such as 1‐propanol, 2‐propanol, 1‐hexanol, 2‐hexanol, 3‐hexanol, 1‐methoxy‐2‐propanol, and 3‐methoxy‐1‐propanol were used in high molar excess to diisocyanate in toluene at 80°C, and pseudo–first‐order dependences on the concentrations of 4,4′‐MDI and 2,4′‐MDI were found. Appropriate treatments of the kinetic data allowed us to determine the corresponding pseudo–first‐order rate constants. According to the kinetic results, the reactivity of the isocyanate group in the para‐position is about four to six times higher than that of the ortho‐positioned isocyanate group, depending on the reacting alcohol. Furthermore, the substitution effect, i.e., change in the reactivity of the free isocyanate group after the other has been reacted, was found for both 4,4′‐MDI and 2,4′‐MDI isomers. The differences in the reactivities of the isocyanate groups of 2,4′‐MDI and 4,4′‐MDI isomers before and after one of two isocyanate groups has been reacted are explained in terms of partial positive charges on the corresponding carbonyl carbon atom calculated by high‐level quantum chemical calculations. In addition, the UV‐spectral properties of the products obtained by quenching the reaction mixture with methanol are also discussed in light of practical implications.

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“…[4][5][6] The production routes to PUs are based on the addition reactions of isocyanates with functionalities of two or higher with different types of polyols. [11][12][13][14][15][16][17][18][19][20] The kinetics of the reaction between diisocyanates and polyols and polymer polyols with functionalities of two or higher are also well-documented. Evidently, the reactions of the isocyanate group with the hydroxyl groups of polyols play an essential role in the synthesis of PUs.…”

Section: Introductionmentioning

confidence: 99%

Uncatalyzed reactions of 4,4′-diphenylmethane-diisocyanate with polymer polyols as revealed by matrix-assisted laser desorption/ionization mass spectrometry

et al. 2016

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The uncatalyzed reactions of polyols including polypropylene glycol (PPG, M n ¼ 2000 g mol À1 ), polytetrahydrofuran (PTHF, M n ¼ 1000 g mol À1 ), poly(3-caprolactone)-diol (PCLD, M n ¼ 2000 g mol À1 ) and polypropylene glycol glycerol triether (PPG_GL, M n ¼ 1000 g mol À1 ) with 4,4 0 -diphenylmethanediisocyanate (MDI) were studied using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The reactions between these polyols and MDI were monitored in time and first-order consecutive reaction kinetics for the formations of polyols end-capped with MDI units were established. The fractional MALDI-TOF MS intensities obtained for the different polymer series at various reaction times were converted into molar fractions versus time data by means of the estimated relative MALDI-TOF MS response factors from which the corresponding rate constants and the relative reactivities of the hydroxyl groups of polyols were determined. It was found that the pseudo first-order rate constants for the polyol-MDI reaction decreased in the order of PCLD > PTHF > PPG z PPG_GL. It was also ascertained that the reactivity of the unreacted hydroxyl groups of the diols does not change significantly after the first one has reacted. On the contrary, in the case of PPG_GL it was found that the reactions of the hydroxyl groups with MDI proceed faster after any of the three hydroxyl groups has reacted, suggesting a positive substitution effect for this system. Reaction of polymer diols with MDIPolymer diols including polypropylene glycol (PPG, M n ¼ 2000 g mol À1 ), polytetrahydrofuran (M n ¼ 1000 g mol À1 ) andScheme 2 The reaction of polypropylene glycol glycerol triether (PPG_GL) with MDI (a) and the products obtained after quenching the reaction mixture by methanol (b).47026 | RSC Adv., 2016, 6, 47023-47032This journal is

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Studies of model urethane reactions and cure in polyurethanes by UV absorption and fluorescence spectroscopy

Cited by 24 publications

References 4 publications

New insight into the kinetics of diisocyanate‐alcohol reactions by high‐performance liquid chromatography and mass spectrometry

New insight into the kinetics of diisocyanate‐alcohol reactions by high‐performance liquid chromatography and mass spectrometry

Kinetics of Uncatalyzed Reactions of 2,4′- and 4,4′-Diphenylmethane-Diisocyanate with Primary and Secondary Alcohols

Uncatalyzed reactions of 4,4′-diphenylmethane-diisocyanate with polymer polyols as revealed by matrix-assisted laser desorption/ionization mass spectrometry

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