Use of isoconversional methods to analyze the cure kinetics of isocyanate‐ended quasi‐prepolymers with water

Daniel‐da‐Silva, Ana L.; Bordado, João; Martı́n-Martı́nez, José Miguel

doi:10.1002/app.24914

Cited by 8 publications

(8 citation statements)

References 33 publications

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“…Several polypropylene‐glycols, with different average molecular weights (400, 3000, and 4000 g/mol), named P400, P3000, and P4000, respectively, and linear (functionality 2 for P400 and P4000) or branched (functionality 3 for P3000) molecular structures, were used as received. The synthesis of NCO‐terminated polymers was followed according to the methodology described by Daniel da Silva et al10 NCO‐terminated polymers were synthesized by inducing the reaction between the polyol and an excess (5% molar) of pMDI. Further details can be found elsewhere 8, 10.…”

Section: Methodsmentioning

confidence: 99%

“…The synthesis of NCO‐terminated polymers was followed according to the methodology described by Daniel da Silva et al10 NCO‐terminated polymers were synthesized by inducing the reaction between the polyol and an excess (5% molar) of pMDI. Further details can be found elsewhere 8, 10. Free NCO contents and polymer functionalities for the different NCO terminated polymers synthesized are shown in Table I.…”

Section: Methodsmentioning

confidence: 99%

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Rheology of lubricating greases modified with reactive NCO‐terminated polymeric additives

Moreno

Franco

Valencia

et al. 2010

J of Applied Polymer Sci

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A comprehensive rheological characterization of lithium lubricating greases modified with NCO-terminated polymers has been performed in this work, with special emphasis on the effect of temperature. With this aim, NCO-terminated polymers were prepared from several di-and tri-functional polyols and polymeric MDI. Afterwards, the reaction between terminal isocyanate groups and 12-hydroxystearate lithium soap, used as thickener for lubricating grease formulations, was promoted. Transient and steady-state viscous flow, rheodestruction and stress relaxation tests were performed on the different samples studied. In this sense, the influence that temperature, free NCO content, molecular weight, and functionality of the reactive polymers exert on the rheological response of lubricating greases was analyzed.The most important rheological modification was achieved by using the lowest molecular weight polymer. In general, NCO-terminated polymers significantly dampen the influence of temperature on the rheological functions of the additive-free lubricating grease. In some cases, the viscosity and/or viscoelastic functions even increase with temperature, especially in formulations with residual free NCO groups. Several experimental flow problems, such as fracture and sample expelling from the measuring tool, are generally found, more frequently in formulations with high NCO content.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Rheology of lubricating greases modified with reactive NCO‐terminated polymeric additives

Moreno

Franco

Valencia

et al. 2010

J of Applied Polymer Sci

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“…Despite the industrial relevance of NCO ended urethane quasi‐prepolymers, to our knowledge only a few studies have been devoted to the kinetics of the curing reaction of low free NCO content ended prepolymers with water 6, 7. More recently, we have shown the potential of using a model‐free kinetic approach to better understand the complex curing process of NCO quasi‐prepolymers 8…”

Section: Introductionmentioning

confidence: 99%

Moisture curing kinetics of isocyanate ended urethane quasi‐prepolymers monitored by IR spectroscopy and DSC

Daniel‐da‐Silva

Bordado²,

Martı́n-Martı́nez

2007

J of Applied Polymer Sci

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The study of the kinetics of the curing of isocyanate quasi-prepolymers with water was performed by infrared spectroscopy and differential scanning calorimetry. The influence of the free isocyanate content, polyol functionality, and of the addition of an amine catalyst (2,2 0 -dimorpholinediethylether) in the reaction kinetics and morphology of the final poly(urethane urea) was analyzed. A second-order autocatalyzed model was successfully applied to reproduce the curing process under isothermal curing conditions, until gelation occurred. A kinetic model-free approach was used to find the dependence of the effective activation energy (E a ) with the extent of cure, when the reaction was performed under nonisothermal conditions. The dependence of E a with the reaction progress was different depending on the initial composition of the quasi-prepolymer, which reveals the complexity of the curing process.

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“…It is clearly shown in Table 2 that the activation energies on the first segment are higher than those on the second segment, which further indicates that the reaction at prophase obeys the diffusion controlled mechanism. An alternative approach is the application of the modelfree isoconversional methods which allow for the evaluation of the activation energy as a function of the extent of the reaction, without assuming any kinetic model [20,47,48]. These methods including integral methods (Isoint methods) and differential methods (FR methods) shown in (8) and (9) are determined by the specific form of in the basic equation [49]:…”

Section: Curing Kinetics Analysismentioning

confidence: 99%

“…have been used to study the curing of epoxy resin and polyurethane systems [13,[20][21][22]. Traditionally, the common chemical analysis techniques attempting to study the curing process are Fourier transform infrared spectroscopy (FTIR) [23,24] and differential scanning calorimetry (DSC) [25,26] which detect the degree of the conversion of reactive groups and they have been used in previous curing researches [27][28][29].…”

Section: Introductionmentioning

confidence: 99%

A Study of Isothermal Curing of PMI Using DMA

Zhang

Zou

et al. 2015

Advances in Materials Science and Engineering

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The isothermal curing of polymethacrylimide (PMI) is studied through the use of dynamic mechanical analysis (DMA). Based on the growth rate of measured dynamic mechanical property, the relative conversion is defined to investigate the evolution of storage modulus at different curing temperatures. Hsich's nonequilibrium thermodynamic fluctuation theory, Avrami equation, and isoconversional methods are used to analyze isothermal cure kinetics of PMI. The results show that there are different increase modes of at low temperature range and high temperature range, respectively. In low temperature range, the relative conversion curves include a transitional stage which is found to be strongly frequency-dependent, but this stage is not observed in the relative conversion curve in high temperature range. During the isothermal curing process, the relative evolution of can be described by Hsich's nonequilibrium thermodynamic fluctuation theory and Avrami equation. Moreover, the values and evolutions of activation energy are different in two temperature ranges, which suggest that the curing mechanism probably has changed.

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Use of isoconversional methods to analyze the cure kinetics of isocyanate‐ended quasi‐prepolymers with water

Cited by 8 publications

References 33 publications

Rheology of lubricating greases modified with reactive NCO‐terminated polymeric additives

Rheology of lubricating greases modified with reactive NCO‐terminated polymeric additives

Moisture curing kinetics of isocyanate ended urethane quasi‐prepolymers monitored by IR spectroscopy and DSC

A Study of Isothermal Curing of PMI Using DMA

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