A DSC, TG, IR study of the thermal decomposition of some alkyl- and aryl-ureas

Stradella, L.; Argentero, Massimo

doi:10.1016/0040-6031(95)02432-8

Cited by 17 publications

(8 citation statements)

References 7 publications

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“…The temperatures at which the material lost its dimensional stability, the flow temperature, are depicted in Figure . Since we are interested in the material properties at and above ambient temperature, the lower limit of the desired flow temperature range is room temperature, and the upper limit is 200 °C, which is the decomposition temperature of the urea groups . This window is indicated by the two dotted horizontal lines.…”

Section: Resultsmentioning

confidence: 99%

Synthesis and Characterization of Segmented Copoly(ether urea)s with Uniform Hard Segments

2005

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Employing protective group strategy and novel isocyanate chemistry, segmented copoly(ether urea)s with uniform hard segments were prepared. Amine-terminated poly(tetrahydrofuran) served as the soft segment of these polymers. The size of the hard segments and the number of urea groups it contains were varied systematically, and their influence on the properties was investigated. The strength of hydrogen bonding between the urea groups in monodisperse hard segments containing exactly 1 to exactly 4 urea groups was studied by infrared spectroscopy and compared with materials containing polydisperse hard segments. The strength of hydrogen bonding in polymers possessing exactly two urea groups per hard segment resulted in an optimal balance between excellent mechanical properties and good processability and solubility.

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Section: Resultsmentioning

confidence: 99%

Synthesis and Characterization of Segmented Copoly(ether urea)s with Uniform Hard Segments

2005

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“…Recently, Coebel and Elsener [49,50] mentioned that the thermal decomposition of urea can yield a variety of products apart from ammonia and isocyanic acid. The second anion is carbonate, produced from the complete decomposition of urea, as shown in the equation…”

Section: Discussionmentioning

confidence: 99%

Preparation and characterization of a new layered double hydroxide, Co–Zr–Si

Saber

2006

Journal of Colloid and Interface Science

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“…Using the latter level of theory allows us to remain consistent with the CCSD(T)/CBS approach, where the same level of calculation is used for geometries and frequencies. As shown in the literature, hydrogen bonding is suspected to be an important parameter in arylurea thermal decomposition experiments . The M06-2X method is known to better describe such nonbonded interactions compared to B3LYP .…”

Section: Methodsmentioning

confidence: 98%

Theoretical Study of the Thermal Decomposition of Urea Derivatives

et al. 2022

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An extensive theoretical study of the thermal decomposition of alkyl- and phenylureas, which are widely used in the pesticides, pharmaceuticals, and materials industries, has been carried out using electronic structure calculations and reaction rate theories. Enthalpies of formation and bond dissociation energies (BDE) of 11 urea derivatives have been calculated using different levels of theory (CBS-QB3, CCSD(T)/CBS//M06-2X/6-311++G(3df,2pd), and CBS-QM062X) according to the size of the system. Potential energy surfaces for the unimolecular decomposition pathways of these urea derivatives were also systematically computed for the first time. Several pericyclic reactions can be envisaged, as a function of the size and the nature of the N substituents, and all of these pathways were explored. Our calculations show that these compounds are solely decomposed by four-center pericyclic reactions, yielding substituted isocyanates and amines, and that initial bond fissions are not competitive. Based on the set of urea derivatives studied, a new reaction rate rule for their thermal decomposition was defined and involves the nature of the transferred H atom (primary or secondary/alkyl or benzyl) and the nature of the N-atom acceptor (primary, secondary, or tertiary). This new reaction rate rule allows us to determine the product branching ratios in the thermal decomposition of a given urea derivative and its total rate of decomposition. Applications on urea derivatives used in the chemical industry are presented and illustrate the usefulness of this new rate rule that allows to predict the previously unknown thermal decomposition kinetics of a large number of these compounds.

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A DSC, TG, IR study of the thermal decomposition of some alkyl- and aryl-ureas

Cited by 17 publications

References 7 publications

Synthesis and Characterization of Segmented Copoly(ether urea)s with Uniform Hard Segments

Synthesis and Characterization of Segmented Copoly(ether urea)s with Uniform Hard Segments

Preparation and characterization of a new layered double hydroxide, Co–Zr–Si

Theoretical Study of the Thermal Decomposition of Urea Derivatives

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