Synthesis of a novel melamine-formaldehyde resin-supported ionic liquid with Brønsted acid sites and its catalytic activities
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Brønsted–Lowry acid–base theory
Melamine resin
Abstract Crosslinking chemistry and network formation in hydroxy and carboxy functional acrylic copolymer resins cured with representative melamine‐formaldehyde crosslinking agents have been studied by infrared spectroscopy. Network formation in these systems is dominated by two reactions, the condensation of the hydroxy (or carboxy) functionality of the acrylic resin with melamine alkoxy groups to form acrylic‐melamine crosslinks, and the condensation of melamine hydroxy groups to form melamine‐melamine crosslinks. The extents of these reactions have been studied as functions of acrylic resin composition, melamine type and concentration, and cure time and temperature. For melamines with just methoxy functionality, the extent of formation of acrylic‐melamine crosslinks increased steadily with cure temperature. For melamines with substantial hydroxy functionality, the extent of formation of acrylic‐melamine crosslinks increased rapidly then leveled off with increasing cure temperature. The formation of melamine‐melamine crosslinks increased slowly with increasing cure temperature. From these data and a statistical model, effective crosslink densities were calculated. The crosslink densities correlated well with solvent resistance.
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Acrylic acid
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Melamine resin
Characterization
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Abstract A method of compositive characterization of Melamine‐Formaldehyde (MF) condensates by combining NMR spectroscopy and chemical analysis has been developed. Some Melamine‐Formaldehyde derivatives were prepared (dimethylol melamine, trimethylol melamine, hexamethylol melamine) to interpret the NMR spectra of MF condensates. The MF condensates (solid or lyophilized samples) were examinated in dimethylsulfoxide d 6 /CaCl 2 solvent phase without any chemical pretreatments. By this method it is possible to determine the content of methylol, methylene and oxymethylene formaldehyde and of nonsubstituted, monosubsituted and disubstituted amino groups.
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Methylene
Chemical modification
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Melamine resin
Urea-formaldehyde
Triazine
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Migration of melamine and formaldehyde into food‐simulating solvents from cups made of melamine resin was studied under various conditions. Little migration of melamine was observed in any unused cups kept at 60°C for 30 min, room temperature (26°C) for 1 h or cooled at—20°C for several days. Migration of both compounds was strongly affected by heating and acidity. The highest migration of melamine into 4% acetic acid used as a food‐simulating solvent was 42.9 ± 7.2 ppm when the migration test was repeated seven times at 95°C for 30 min. In this time, the migration of formaldehyde was 14.2 ±0.6 ppm into the solvent. The molecular ratio of the migration amount of formaldehyde to melamine decreased according to the formula Y=9.15X−0.813 over seven repetitions of the test, and was maintained at about 1.6 between the 10th and 20th repetitions. The inner surface of the cups became tarnished during the repetition of the test and their roughness increased from 1 μm before the test to 2.5–5 μm after 20 repetitions of the test. Migration of melamine from the cups being used at a cafeteria was 0.4 ± 0.5 ppm, but that of formaldehyde was undetectable when the cups were kept at 60°C for 30 min with 4% acetic acid.
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Melamine is an important chemical raw material. Its main applications are as follows: using as a flame retardant; synthesizing melamine formaldehyde resin and preparing melamine derivatives. The applications of melamine are described systemati- cally on the basis of introducing the characteristics of melamine, the modification of melamine formaldehyde resin and melamine derivatives.
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Melamine resin
Urea-formaldehyde
Triazine
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Abstract The addition of melamine acetate salts to an adhesive glue mix can allow the use of melamine–urea–formaldehyde (MUF) resins of lower melamine contents (rather than just urea–formaldehyde resins) and lower total amounts of melamine. Performances can be obtained that are characteristic of the top‐of‐the‐line, generally higher melamine content MUF adhesive resins for the preparation of wood particleboard panels. Improvements in the panel internal‐bond strength of greater than 30% can be obtained by the addition of melamine acetate salts to top‐of‐the‐line MUF resins. The approach to the concept of increased melamine solubility with a melamine salt is compatible with the approach of increasing melamine solubility with solvents such as acetals (e.g., methylal). However, the synergy advantage of using the two approaches jointly is not very marked. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 287–292, 2003
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Melamine resin
Water resistance
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The procedure for preparing sulfonated melamine formaldehyde resins and the factors affecting it were investigated. A four-step procedure was developed which results in reproducible watersoluble stable resins. The reactions that take place in the four steps are hydroxymethylation, sulfonation of the methylolmelamine intermediate, low pH condensation, and high pH rearrangement reaction. The reaction and the resins produced were found to be very sensitive to pH, temperature, sulfite/melamine, and formaldehyde/melamine molar ratios. The apparent molecular weight distribution of selected samples was also determined.
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Molar mass distribution
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