Examination of selected synthesis parameters for typical wood adhesive-type urea-formaldehyde resins by13C NMR spectroscopy. I

Kim, Moon G.

doi:10.1002/(sici)1099-0518(19990401)37:7<995::aid-pola14>3.0.co;2-6

Cited by 51 publications

(16 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Chemical shift values were assigned and carbon groups were quantified by using similar methods as those in our previous study (Kim 1999(Kim , 2000(Kim , 2001. The observed group distributions are in general very similar to those of the previous study, but the differences that occurred due to the strong acidic reaction step used in the resin synthesis were clearly shown, summarized as: (a) lower total hydroxylmethyl group contents; (b) higher total methylene-ether group contents, especially Type III methylene-ether contents; (c) similar total methylene group contents, but higher Type III methylene contents; and (d) higher cyclic urea contents to indicate the uron-type structures for some of the methylene-ether groups (Gu et al 1995;Soulard et al 1999).…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Low Mole Ratio UF and UMF Resins Entailing Uron-Type Methylene-Ether Groups and their Low Formaldehyde Emission Potentials

2013

Self Cite

View full text Add to dashboard Cite

The previous study on low mole ratio urea-formaldehyde (UF) and ureamelamine-formaldehyde (UMF) resins synthesized in the typical way as particleboard binders was repeated with the inclusion of a strong acidic reaction step at a mole ratio of 2.7 in the beginning of the resin synthesis procedure. The resulting UF and UMF resins showed longer storageand pot-lives, longer gel times, and the particleboards gave higher internal bond and lower water-soak absorption values. However, the free formaldehyde contents of boards were increased with UF resins and decreased with UMF resins, indicating that the uron-type methyleneether groups formed from the strong acidic step resulted in enhancement of the bonding, but they give off some extra formaldehyde, which is captured more effectively in UMF resins because of the higher reaction capacity of melamine. The extra acidic reaction step could be useful in UMF resin syntheses. The generation of extra formaldehyde by urontype methylene-ether bonds is documented.

show abstract

Section: Resultsmentioning

confidence: 99%

“…*** Degree of polymerization was calculated using: DP = 1 / [1 − (methylene + 0.5 x methylene-ether)]. For chemical structures and names of functional groups, refer to Kim (1999;2000;2001).…”

Section: Resultsmentioning

confidence: 99%

Low Mole Ratio UF and UMF Resins Entailing Uron-Type Methylene-Ether Groups and their Low Formaldehyde Emission Potentials

2013

Self Cite

View full text Add to dashboard Cite

show abstract

“…The spectra were recorded with a pulse angle of 90 degrees (12 µs). A 6-s relaxation delay was used to secure quantitative results of methylenic carbons, which had T1 values of 0.16 s or smaller, measured by the inversion recovery method [4]. To achieve a sufficient signal-to-noise ratio, the inverse-gated proton decoupling method was used.…”

Section: Procedures For Quantitative 13 C-nmr Determinationmentioning

confidence: 99%

“…The spectra were recorded at 150 MHz with 400-600 scans accumulated. The observed chemical shifts were assigned by referring to the assignments in the literature [3][4][5][6][7][8][9][10][11][12][13][14][15].…”

Section: Procedures For Quantitative 13 C-nmr Determinationmentioning

confidence: 99%

“…After the acidic condensation, the pH is adjusted back to alkaline and the additional urea (the second urea) is added to lower the F/U molar ratio to 0.9-1.2, aiming to capture the un-reacted formaldehyde. Although intensive studies have been completed to investigate the chemical structures of resin polymers by employing nuclear magnetic resonance d(NMR) analysis [3][4][5][6][7][8][9][10][11][12][13][14][15], our survey of the literature showed that the effects of post-added urea on the UF polymers were not focused or well-discussed. However, this issue is important for better understanding the relationship between low molar ratio and poor performance of the resin.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Characterization of the Low Molar Ratio Urea–Formaldehyde Resin with 13C NMR and ESI–MS: Negative Effects of the Post-Added Urea on the Urea–Formaldehyde Polymers

Wang

Cao

et al. 2018

Polymers

View full text Add to dashboard Cite

Abstract:The structural changes during three-step synthesis of low-molar ratio urea-formaldehyde (UF) resin were tracked by quantitative 13 C nuclear magnetic resonance ( 13 C NMR) analysis and electrospray ionization-mass spectrometry (ESI-MS). Condensations that produced polymers were found to be linked by ether bonds in addition to hydroxymethylation reactions at the first alkaline stage with a formaldehyde to urea ratio of 2:1. Considerable formation of branched methylene linkages, with the highest content among all the condensed structures, was the key feature of the acidic stage. Notable changes were observed for the chemical structures and molecular masses of the resin components after the formaldehyde to urea molar ratio was lowered to 1.2 by adding post-urea at the final alkaline stage. Specifically, most of the branched hydroxymethyl groups on the polymers were cleaved, resulting in a significant decrease in the branching degree of the polymers. The performance degradation of the UF resin was attributed to this debranching effect and the production of components with low molecular masses. Based on the observations, the curing pattern of low molar ratio UF resin was postulated and branched polymeric formaldehyde catcher bearing urea-reactivity was proposed.

show abstract

Urea‐Formaldehyde Resins

2019

Adhesives for Wood and Lignocellulosic Materials

View full text Add to dashboard Cite

Examination of selected synthesis parameters for typical wood adhesive-type urea-formaldehyde resins by13C NMR spectroscopy. I

Cited by 51 publications

References 15 publications

Low Mole Ratio UF and UMF Resins Entailing Uron-Type Methylene-Ether Groups and their Low Formaldehyde Emission Potentials

Low Mole Ratio UF and UMF Resins Entailing Uron-Type Methylene-Ether Groups and their Low Formaldehyde Emission Potentials

Characterization of the Low Molar Ratio Urea–Formaldehyde Resin with 13C NMR and ESI–MS: Negative Effects of the Post-Added Urea on the Urea–Formaldehyde Polymers

Urea‐Formaldehyde Resins

Contact Info

Product

Resources

About