Urea-Formaldehyde Kinetic Studies. I. Variation in Urea Solutions

Smythe, L.E.

doi:10.1021/ja01150a089

Cited by 33 publications

(16 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Methylene groups have been known to form only in the acidic pH within the common time regimes used in the manufacturing of UF resins. 1,[3][4][5][6][7][8][9][10][11] In addition, the turbidity of Samples B5 and B6 cast some uncertainty on the accuracy of 13 C-NMR results, but it was very light and appears to be too minimal to increase the Type I methylene-group content by preferentially suppressing other carbon groups. The increases in Type I methylene groups in Sample B5 and B6 are corroborated by the significant decreases in the overall hydroxymethyl-group content as well as decreases in the free urea content observed in the 13 C-NMR carbonyl-group data.…”

Section: Room-temperature Storage Of Uf Resinsmentioning

confidence: 99%

“…In previous publications, some details on reaction pathways occurring during and after the synthesis of wood adhesive-type urea-formaldehyde (UF) resins were reported based on 13 C-NMR data. 1,2 UF resins have been known for many decades [3][4][5][6][7][8][9][10][11] and are currently used worldwide as thermosetting wood adhesives in manufacturing particleboard (PB) and medium-density fiberboard. 12 Drawbacks of UF resins are low water resistance and tendency to emit formaldehyde from bonded wood composite boards.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Examination of selected synthesis parameters for typical wood adhesive-type urea–formaldehyde resins by 13C-NMR spectroscopy. II

Kim

2000

J. Appl. Polym. Sci.

View full text Add to dashboard Cite

A particleboard adhesive-type urea-formaldehyde (UF) resin was made at a formaldehyde ratio of 2.10 and added with a second urea at low temperature to the typical final formaldehyde/urea ratio of 1.15. Time samples taken during heat treatments of the resin sample up to 70°C over a period of 250 min showed decreases in Type II/IIi hydroxymethyl group content, accompanied with decreases in resin sample viscosity and increases in formaldehyde emission of bonded particleboards. The results indicate that various hydroxymethyl groups of polymeric UF resin components migrate to the second urea to form Type I hydroxymethyl groups. Time samples taken during the room-temperature storage of the resin sample over a period of 1 month behaved similarly initially, but in the later stage, some polymerization progressed, shown by increases in viscosity and methylene and methylene-ether group contents.

show abstract

Section: Room-temperature Storage Of Uf Resinsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Examination of selected synthesis parameters for typical wood adhesive-type urea–formaldehyde resins by 13C-NMR spectroscopy. II

Kim

2000

J. Appl. Polym. Sci.

View full text Add to dashboard Cite

show abstract

“…Urea-formaldehyde (UF) resins have been known for many decades and currently are used as thermosetting wood-adhesive binders in manufacturing interior-use wood-composite boards, such as particleboard (PB) and medium-density fiber-board. [1][2][3][4][5][6][7][8][9] The drawbacks of UF resins are the low water resistance and high formaldehyde-emission levels of wood-composite boards, 10 -13 which have been the industry's concern in recent years. The overall formaldehyde/urea (F/U) mol ratio used in the manufacturing of UF resins, which currently runs at a low value of about 1.15, has been the key parameter used in controlling the formaldehydeemission level.…”

Section: Introductionmentioning

confidence: 99%

Examination of selected synthesis and room‐temperature storage parameters for wood adhesive‐type urea–formaldehyde resins by ¹³C‐NMR spectroscopy. IV

Kim

Wan

et al. 2001

J of Applied Polymer Sci

View full text Add to dashboard Cite

Typical particleboard wood-adhesive urea-formaldehyde (UF) resins, synthesized with formaldehyde/first urea (F/U 1 ) mol ratios of 1.80, 2.10, and 2.40 and the second urea added to an overall F/U ratio of 1.15, in weak alkaline pH, were allowed to stand at room temperature over a period of 50 days.13 C-NMR of time samples taken over the storage period showed gradual migration of hydroxymethyl groups from the polymeric first-urea components to the monomeric second-urea components and also an advancing degree of polymerization of resins by forming methylene and methylene ether groups involving the second urea. These phenomena that varied with the F/U 1 mol ratios used in the resin syntheses due to the varying polymer branching structures resulted in the first step of resin synthesis. Varying viscosity decreases and increases of the resins also occurred. Due to these chemical and physical changes, the particleboards that bonded with the sampled resins showed varying bond strength and formaldehydeemission values, indicating process optimizations possible to improve bonding and formaldehyde-emission performances.

show abstract

“…We observed that the pH increased with time in our experiments. This is probably due to the decomposition of urea to give ammonium salts, a process that has been observed before (de Jong 1950;Smythe 1951). However, the inclusion of a buffer in the reaction mixture did not significantly effect the course of the reaction.…”

Section: Resultsmentioning

confidence: 90%

Oligonucleotides as probes for studying polymerization reactions in dilute aqueous solution: II. Polycondensations

Kolb

Orgel

1995

J Mol Evol

View full text Add to dashboard Cite

We have prepared a [32P]-labeled oligonucleotide probe carrying a ureido (-NH-CO-NH2) function at its 3'-terminus. This labeled oligomer was used to study polycondensations of urea and formaldehyde and of various phenols and formaldehyde in aqueous solution. The formation of formaldehyde copolymers attached to the amido-function of the probe was monitored by gel electrophoresis. Our results are generally in agreement with those obtained using conventional techniques. Our method is suitable for monitoring potentially prebiotic polycondensation reactions involving formaldehyde.

show abstract

Urea-Formaldehyde Kinetic Studies. I. Variation in Urea Solutions

Cited by 33 publications

References 0 publications

Examination of selected synthesis parameters for typical wood adhesive-type urea–formaldehyde resins by 13C-NMR spectroscopy. II

Examination of selected synthesis parameters for typical wood adhesive-type urea–formaldehyde resins by 13C-NMR spectroscopy. II

Examination of selected synthesis and room‐temperature storage parameters for wood adhesive‐type urea–formaldehyde resins by ¹³C‐NMR spectroscopy. IV

Oligonucleotides as probes for studying polymerization reactions in dilute aqueous solution: II. Polycondensations

Contact Info

Product

Resources

About

Urea-Formaldehyde Kinetic Studies. I. Variation in Urea Solutions

Cited by 33 publications

References 0 publications

Examination of selected synthesis parameters for typical wood adhesive-type urea–formaldehyde resins by 13C-NMR spectroscopy. II

Examination of selected synthesis parameters for typical wood adhesive-type urea–formaldehyde resins by 13C-NMR spectroscopy. II

Examination of selected synthesis and room‐temperature storage parameters for wood adhesive‐type urea–formaldehyde resins by 13C‐NMR spectroscopy. IV

Oligonucleotides as probes for studying polymerization reactions in dilute aqueous solution: II. Polycondensations

Contact Info

Product

Resources

About

Examination of selected synthesis and room‐temperature storage parameters for wood adhesive‐type urea–formaldehyde resins by ¹³C‐NMR spectroscopy. IV