ChemInform Abstract: MECHANISMS OF PEPTIDE COUPLING REACTIONS

Horiki, Kusuo

doi:10.1002/chin.197819284

Cited by 1 publication

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“…3,4 Although the high reactivity is considered a desired property in resin applications, it has also created problems with controlling the reaction of formaldehyde addition in resin synthesis and also with pot life and the storage of the resins. 5,6 To control the excessive reactivity of AR in resin preparation, acetone or other carbonyl compounds have often been added to form hydrogen-bonded complexes with phenolic hydroxyls to reduce the reaction rate of hydroxymethylation. 7,8 Nevertheless, even with complexing agents to reduce reactivity by a factor of 10, the hydroxlymethylation of AR is still eight times faster than the rate of resorcinol.…”

Section: Introductionmentioning

confidence: 99%

Melamine‐bridged alkyl resorcinol modified urea–formaldehyde resin for bonding hardwood plywood

Hse

Higuchi

2010

J of Applied Polymer Sci

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A powdery product was obtained by the reaction of methylolated melamine with alkyl resorcinols to form melamine-bridged alkyl resorcinols (MARs). The effects of the addition of this powder on the bonding strength and formaldehyde emission of urea-formaldehyde (UF) resins were investigated. Three types of UF resins with a formaldehyde/urea molar ratio of 1.3 synthesized by condensation at pH 1.0 (UF-1.0), pH 4.5 (UF-4.5), and pH 5.0 (UF-5.0) were fabricated. The addition of MAR to UF-4.5 and UF-5.0 for bonding hardwood plywood enhanced the bonding strength and reduced formaldehyde emission. For UF-1.0, the addition of MAR adversely affected the bonding strength. However, the UF-1.0 resin yielded the lowest formaldehyde emission of all of the UF resins in the study. The effects of the MAR addition were related to the molecular structures of the UF resins. UF-1.0 contained a large amount of free urea, a considerable number of urons, and a highly methylenelinked, ring-structured higher molecular weight fraction and had a smaller number of methylol groups. Therefore, the addition of MAR was considered to cause a shortage of the methylol groups, which in turn, led to incomplete resin curing. In contrast to UF-1.0, UF-5.0 contained a smaller amount of free urea and a linearly structured higher molecular weight fraction and had a larger number of methylol groups. In this case, MAR was considered to effectively react with the methylol groups to develop a three-dimensional crosslinked polymer network to enhance the bonding strength and suppress the generation of free formaldehyde to reduce formaldehyde emission.

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