Urea–formaldehyde resin prepared with concentrated formaldehyde

Wu, Zhigang; Lei, Hong; Du, Guanben; Cao, Ming; Xi, Xuedong; Liang, Jiankun

doi:10.1080/01694243.2016.1193963

Cited by 21 publications

(11 citation statements)

References 25 publications

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“…The peaks of free U appeared at 160−161 ppm, and the mono-and disubstituted U at 159−160 ppm and 157−158 ppm, respectively. 6,16,36 With regard to the ratios of methylene/methylol and methylene ether/methylene along the different steps of Resin A, Figure 5 summarizes the results obtained. From these ratios, it is possible to conclude that the methylene linkages are preferentially formed at the beginning of synthesis (Res A1 and Res A2), but this feature is reversed at the end of condensation step (Figure 5).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Res A9 presents a higher quantity of dimethylol groups that should be responsible for better mechanical properties of this resin. 15 The values for methylene glycol carbons indicated that Res A8 (0.2%) presents lower free F than Res A9 (0.7%). As mentioned before, all these results can be explained by the difference between the ratio of F/U used.…”

Section: Industrial and Engineering Chemistry Researchmentioning

confidence: 92%

“…In order to understand the chemical structure of the polymer formed during the synthesis process, several methods have already been used. ,− Among the many existing methods to characterize resins, liquid-state 13 C NMR is the most used. This technique provides the most complete information on the chemical structures of F based resins, enabling the identification and quantitative determination of many functional groups.…”

Section: Introductionmentioning

confidence: 99%

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Impact of the Synthesis Procedure on Urea-Formaldehyde Resins Prepared by Alkaline–Acid Process

Gonçalves

Pereira

Paiva³

et al. 2019

Ind. Eng. Chem. Res.

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In this work, two synthesis procedures for the preparation of urea-formaldehyde (UF) resins, based on the alkaline–acid process, are studied in order to better understand the chemical reactions involved. For that purpose, the number of urea loads and the methyolation temperature were varied. The molecular weight distribution of the resins was monitored by gel permeation chromatography/size exclusion chromatography and the unreacted oligomers by high-performance liquid chromatography, during the synthesis processes. Chemical modifications were investigated using quantitative analysis by carbon-13 nuclear magnetic resonance of samples taken during the synthesis. The largest difference identified between the procedures regards the methylene linkages and methylol groups determined by 13C NMR. With the results of this study, it is possible to optimize the process and the properties of particleboards produced.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Section: Industrial and Engineering Chemistry Researchmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Impact of the Synthesis Procedure on Urea-Formaldehyde Resins Prepared by Alkaline–Acid Process

Gonçalves

Pereira

Paiva³

et al. 2019

Ind. Eng. Chem. Res.

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“…Figure shows the 13 C‐NMR spectra of Resin A (polyetheramine‐formaldehyde) and Resin E (PEA‐UF). Each signal observed in the spectra was identified according to chemical shifts reported in the literature, as seen in Table .…”

Section: Resultsmentioning

confidence: 99%

Introducing flexibility in urea–formaldehyde resins: Copolymerization with polyetheramines

Antunes¹,

Rêgo

Paiva³

et al. 2018

J. Polym. Sci. Part A: Polym. Chem.

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Adhesives obtained by copolymerizing urea, formaldehyde, and difunctional polyetheramine with different molecular weights (230, 600, 900, and 2000 g mol−1) are presented as a more resilient alternative to conventional urea–formaldehyde resins. Urea and polyetheramine contents were varied and the resulting resins characterized by FTIR, 13C‐NMR, and TGA. These resins were used for production of agglomerated cork panels, an application that demands that the binder system is flexible. Polyetheramine with molecular weight 900 g mol−1 yielded the most promising agglomerated cork panel, with remarkable flexibility, good tensile strength, and with the E1 formaldehyde content specification for wood‐based panels used in construction, according to European Standard EN 12460‐5. These new thermoset adhesives have demonstrated to be capable of being used in systems where conventional formaldehyde‐based resins do not perform well due to inherent high rigidity. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 1834–1843

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“…Formaldehyde can react with NH 4 Cl to generate HCl, thereby promoting the curing of amino resin adhesives. However, when NH 4 Cl is added as a curing agent, the wood panel generates extremely toxic dioxin during combustion while low-molar ratio urea formaldehyde (UF) and MUF resins cannot be cured completely [27,28]. To overcome this issue, (NH 4 ) 2 SO 4 was used as a curing agent for amino resin adhesives such as UF and MUF.…”

Section: Basic Physicochemical Properties Of Smuf Resin Adhesivementioning

confidence: 99%

Influence of Single/Collective Use of Curing Agents on the Curing Behavior and Bond Strength of Soy Protein-Melamine-Urea-Formaldehyde (SMUF) Resin for Plywood Assembly

Zhang

Zhou

et al. 2019

Polymers

Self Cite

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Soybean protein hydrolysate, melamine, urea, and concentrated formaldehyde were used to synthesize an environmentally friendly soybean protein-melamine-urea-formaldehyde (SMUF) co-condensation resin. (NH4)2SO4, (NH4)2HPO4, (NH4)2HPO4 + (NH4)2SO4, (NH4)2HPO4 + (NH4)2S2O8, and (NH4)2HPO4 + (NH4)2SO4 + (NH4)2S2O8 were employed as curing agents for SMUF resin. The curing and thermal behaviors of the SMUF resin were investigated using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The results revealed the following: (1) (NH4)2SO4 alone could not cure the SMUF resin completely; thus, the final shear strength accomplished plywood with the resin was low, and its water resistance was poor, while the adhesive section was loose and porous/brittle after curing. (2) (NH4)2HPO4 could be hydrolyzed to generate H+ and promote SMUF curing, but it could also form polyphosphoric acids, resulting in crosslinking reactions with SMUF in parallel; thereby, the curing properties were improved. (3) When (NH4)2HPO4 + (NH4)2SO4 + (NH4)2S2O8 were engaged collectively as curing agent, the shear strength, water resistance, and heat resistance of SMUF attained were the best possible whereas the curing temperature was decreased and the heat released by curing was elevated substantially, which signifies maximized extent of crosslinking was achieved. Further, the adhesive section exhibited mostly a crosslinking intertexture as demonstrated by means of SEM. Accordingly, this study may serve as a guide for the curing of amino resins, with low-molar ratio of formaldehyde to amine in adhesives, which are applied to plywood production.

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Urea–formaldehyde resin prepared with concentrated formaldehyde

Cited by 21 publications

References 25 publications

Impact of the Synthesis Procedure on Urea-Formaldehyde Resins Prepared by Alkaline–Acid Process

Impact of the Synthesis Procedure on Urea-Formaldehyde Resins Prepared by Alkaline–Acid Process

Introducing flexibility in urea–formaldehyde resins: Copolymerization with polyetheramines

Influence of Single/Collective Use of Curing Agents on the Curing Behavior and Bond Strength of Soy Protein-Melamine-Urea-Formaldehyde (SMUF) Resin for Plywood Assembly

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