The addition stage in the melamine-formaldehyde reaction: Computer fittings to the non-random model

Aldersley, J. W.; Gordon, M.; Halliwell, A.; Wilson, Thomas Cunningham

doi:10.1016/0032-3861(68)90044-x

Cited by 14 publications

(3 citation statements)

References 8 publications

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“…RNHÀ À ÀCH 2 À À ÀNHR þ H 2 O Success in making and using amino resins largely depends on the precise control of these two chemical reactions. Consequently, these reactions have been much studied (19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30).…”

Section: Chemistry Of Resin Formationmentioning

confidence: 99%

Amino Resins and Plastics

Williams¹

2002

Kirk-Othmer Encyclopedia of Chemical Technology

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Amino resins are thermosetting polymers made by combining an aldehyde with a compound containing an amino ( \documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}${{\relbar \kern-5pt{\relbar}\kern-7pt{\relbar}}{\rm{NH}}{_{2}}}$\end{document} ) group. Urea–formaldehyde (U/F) accounts for > 80% of amino resins; melamine–formaldehyde accounts for most of the rest. The principal attractions of amino resins and plastics are water solubility before curing; colorlessness; excellent solvent resistance; outstanding hardness and abrasion resistance; and good heat resistance. Amino resins provide a wide variety of useful products. Adhesives, the largest single market, are used to make plywood, chipboard, and sawdust board. Other types are used to make laminated wood beams, parquet flooring, and for furniture assembly. Aminoplasts and other thermosetting plastics are molded by an automatic injection‐molding process similar to that used for thermoplastics. The process is best applied to relatively small moldings. The great advantage of injection molding is that it eliminates manual labor costs, thereby allowing amino resins to better compete with thermoplastics. The future for amino resins and plastics seems secure. New developments will probably be in the areas of highly specialized materials for treating textiles, paper, etc, and for use with other resins in the formulation of surface coatings. Most amino resins are based on the reaction of formaldehyde with urea or melamine. The first step in the formation of resins and plastics from formaldehyde and amino compounds is the addition of formaldehyde to introduce the hydroxymethyl group, known as methylolation or hydroxymethylation. The second step is a condensation reaction that involves the linking together of monomer units with the liberation of water to form a dimer, a polymer chain, or a vast network, usually referred to as methylene bridge formation, polymerization, resinification, or simply cure. Precise control of the course, speed, and extent of the reaction is essential for successful manufacture. Amino resins are usually made by a batch process. Both urea– and melamine–formaldehyde resins are of low toxicity. Melamine–formaldehyde resins may be used in paper that contacts aqueous and fatty foods. However, some mills are looking for alternatives.

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Section: Chemistry Of Resin Formationmentioning

confidence: 99%

Amino Resins and Plastics

Williams¹

2002

Kirk-Othmer Encyclopedia of Chemical Technology

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“…Some deviation from random behavior was noted and parame-K ters were assigned to quantify the rate constants. The validity of these parameters was tested in a computer study by Aldersley, et al (9) who attempted to match experimental data on the free formaldehyde content with results from computation. Tomita (7) carried out a detailed experimental study of molecular species distribution of meth-(b) n HOCH20H 2 HO(-CH20-);;H + ( q -1) H20 K (1) OH -CH20H + OH(-CH20),H 2 OH(-CH20bH + €320 Melamine (2,4,6-triamino, 1,3,5-triazine) is a weakly basic material.…”

Section: Introductionmentioning

confidence: 99%

Modeling of polymerization of melamine and formaldehyde using a functional group approach

Kumar

Chandra

1987

Polymer Engineering & Sci

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A functional group approach that accounts for the formation of higher oligomers was used in modeling the batch polymerization of melamine and formaldehyde. Five rate constants are required instead of 24 as needed in earlier studies to fit experimental data in the entire range. The model presented allows the formation of higher oligomers even though their formation is small. The batch polymerization of melamine and formaldehyde was studied under a wide variation of reaction parameters to find conditions that would lead to formation of higher oligomers preferentially.

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“…The first attempt on developing a more comprehensive theoretical model for the polymerization of this complex system was made recently. 6 In this work, a mathematical framework was developed to analyze the kinetics of melamine-formaldehyde polymerization, accounting for the unequal reactivity of various functional groups. The model presented could predict the number average chain length as well as the average number of branch points per polymer molecule.…”

Section: Introductionmentioning

confidence: 99%

Modeling of melamine formaldehyde polymerization. II. Development of a simpler model

Gupta

1986

J of Applied Polymer Sci

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SynopsisThe kinetic modeling of melamine-formaldehyde polymerization presents a relatively formidable mathematical challenge because of the simultaneous presence of several types of deviations from Flory's equal reactivity hypothesis. A molecule of melamine has six reactive amide hydrogens, which can react with the -CH,OH groups of formaldehyde in solution. The reactivity of the secondary hydrogens on the melamine is about 61% of that of the primary hydrogens (induced asymmetry). There is a shielding effect present, i.e., the reactivity of the hydrogens near the outside of a multiringed polymer molecule is higher than that of the hydrogens inside the coiled molecules. Two bound -CH,OH groups on the polymer molecules can selfcondense to give methylene linkages, the reactivity depending upon the location of the two groups. And, to confound modeling efforts still further, all these reactions are reversible. An earlier attempt at modeling this system considered the reactions between 36 "basic" species. This model was far too detailed and failed to account for the reverse reactions.In the present study, a simpler model has been proposed which involves fewer "basic" species. An improved model for intramolecular reactions is also developed. Several important characteristics of the polymerization have been obtained as a function of time. F&sults from this model have been compared with those obtained from the earlier model, and also compared with the short-time experimental results. The present model can be extended to account for the reverse reactions quite easily.

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The addition stage in the melamine-formaldehyde reaction: Computer fittings to the non-random model

Cited by 14 publications

References 8 publications

Amino Resins and Plastics

Amino Resins and Plastics

Modeling of polymerization of melamine and formaldehyde using a functional group approach

Modeling of melamine formaldehyde polymerization. II. Development of a simpler model

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