Homogeneous methylolation of melamine: Mathematical modeling

Nicolau, Verónica V.; Estenoz, Diana Alejandra; Meira, G. R.

doi:10.1002/app.26796

Cited by 5 publications

(15 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The values under k m * were corrected to take into consideration that only COH 2 undergoes methylolation. The corrected constants ( k m in Table II) were obtained through9: where eq. (8) assumes an instantaneous equilibrium for eq.…”

Section: General Considerationsmentioning

confidence: 99%

“…In the case of k m under Okano and Ogata,4 a factor of 0.5 was also included in the right hand‐side of eq. (8), to allow for the methylolation of all six reactive H's of M. Finally, the values of k m and k ′ m under Nicolau et al9 were obtained by averaging the (12 forward and 12 backward) reported constants.…”

Section: General Considerationsmentioning

confidence: 99%

“…For such mechanism, Tomita8 adjusted 14 (out of the 24) kinetic constants on the basis of dilute solution reactions carried out in at 48°C and pH = 9. Based on the same measurements8 and reaction scheme,3 all the 24 methylolation/demethylolation kinetic constants were recently adjusted in Nicolau et al9…”

Section: Introductionmentioning

confidence: 99%

“…Nastke et al5 presented a theoretical and experimental investigation on buffered methylolation/condensations. In the first part of this series,10 five reactions between F and M were carried out, and the main results are presented further below. Gupta11 employed 10 “chemical entities” for modeling a batch reaction between M and F. The models assume 12 irreversible methylolations, 13 irreversible methylene bridge formations, and only five kinetic constants.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Methylolation of melamine with incipient condensation. II. Mathematical modeling

Nicolau

Estenoz

Meira

2009

J of Applied Polymer Sci

Self Cite

View full text Add to dashboard Cite

A novel mathematical model is presented for the reaction between melamine (M) and formaldehyde (F) at pH ¼ 9.0 and at temperatures between 38 and 90 C. It is based on a kinetic scheme that includes reversible methylolations, irreversible formation of (unsubstituted) methylene bridges, reversible formation of (unsubstituted) ether bridges, instantaneous dissolution of M, and instantaneous equilibrium for the hydration/dehydration of F. The model predicts the distributions of molecular weights and functionalities of the evolving MF resin. Arrhenius expressions were adjusted for the seven kinetic constants on the basis of measurements reported in the first part of this series. Even though the final products contain thousands of different molecular species, 21 of them constitute more than 90% of the total weights. During the initial period with negligible condensation, the undissolved M distorts the distributions of molecular weights and functionalities; but the reversibility of methylolations corrects for such distortion prior to the effective start of condensation.

show abstract

Section: General Considerationsmentioning

confidence: 99%

Section: General Considerationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Methylolation of melamine with incipient condensation. II. Mathematical modeling

Nicolau

Estenoz

Meira

2009

J of Applied Polymer Sci

Self Cite

View full text Add to dashboard Cite

show abstract

“…In the first step, depending on the reaction conditions (mainly the melamine‐to‐formaldehyde molar ratio) up to six molecules of formaldehyde may react with melamine to form primary still water‐soluble methylolated melamine compounds, also known as methylols (methylolation) . These methylols may further condense under liberation of water to form the MF prepolymers, which consist of either methylene‐ or methylene ether‐bridged melamine rings. Typically, MF resin prepolymers intended for paper impregnation are of low‐molecular weight and consist of a statistical mixture of oligomers with about three to five melamine units to keep the viscosity low and allow for good paper penetration .…”

Section: Introductionmentioning

confidence: 99%

Drying and curing behaviour of melamine formaldehyde resin impregnated papers

Kohlmayr

Stultschnik

Teischinger

et al. 2013

J of Applied Polymer Sci

View full text Add to dashboard Cite

Melamine formaldehyde (MF) resins are widely used for the gluing and surface coating of wood‐based consumer products in the interior design of living environments. MF resins are especially relevant in decorative laminate applications because of their good performance‐to‐price ratio. In their industrial processing, an important intermediate state is the liquid MF prepolymer that is used for decorative paper impregnation. Here, the drying of impregnated papers is investigated with respect to premature curing. A new method to quantify water release upon drying that allows estimation of the degree of undesired precuring is described. Since curing proceeds via polycondensation, crosslinking brings about the release of water molecules. By thermogravimetric analysis (TGA), drying was studied in terms of water release due to physical drying (elimination of “dilution water”) and chemical crosslinking of the prepolymer to a three‐dimensional MF network (elimination of chemically liberated water). The results obtained by TGA/IR spectroscopic analysis of the liberated volatiles show that the emission of water from b‐stage MF can be clearly analytically separated into a physical (evaporation of dilution water) and a chemical (liberation via condensation) sequence. TGA experiments were correlated with curing experiments performed with differential scanning calorimetry (DSC) to estimate the residual crosslinking capacities of the impregnated papers. The drying conditions used during the preparation of impregnated decorative papers seemed to significantly affect their remaining reactivity only when harsh drying conditions were used. Upon heat exposure for prolonged time, precuring of the oligomer units results in a shift of the temperature maxima in TGA. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39860.

show abstract

Polymer Cross‐Linkling

Ray

2011

Encyclopedia of Polymer Science and Technology

View full text Add to dashboard Cite

Cross‐linking is a unique tool for polymer modification. Multidirectional chain extension of polymers resulting in the formation of network structure is defined as polymer cross‐linking. It hinders the free movement of polymer chains and restricts them from sliding past each other. Interconnection of the polymer chains generates elasticity in amorphous polymers and makes a polymer more resistant to heat, light, and other physical agencies. It enhances the dimensional stability, mechanical strength, and solvent resistance of a polymer. Cross‐linking may be accomplished either through polymerization of monomers with functionality greater than two (polycondensation) or by covalent bonding between preformed polymer molecules by irradiation, sulfur vulcanization, or miscellaneous chemical reactions. The degree of cross‐linking and regularity of the network are the two vital factors, which control the effects of cross‐linking on the properties of the polymers. Cross‐linking is carried out in elastomers, plastomers, and even on polymer blends to improve properties and to broaden the spectrum of applications. The present review describes different modes and kinetics of polymer cross‐linking as well as its effects on the properties of polymers.

show abstract

Homogeneous methylolation of melamine: Mathematical modeling

Cited by 5 publications

References 21 publications

Methylolation of melamine with incipient condensation. II. Mathematical modeling

Methylolation of melamine with incipient condensation. II. Mathematical modeling

Drying and curing behaviour of melamine formaldehyde resin impregnated papers

Polymer Cross‐Linkling

Contact Info

Product

Resources

About