Hydrolytic stability and crystallinity of cured urea–formaldehyde resin adhesives with different formaldehyde/urea mole ratios

Park, Byung‐Dae; Jeong, Ho‐Won

doi:10.1016/j.ijadhadh.2011.05.001

Cited by 134 publications

(61 citation statements)

References 17 publications

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“…Latex is an amorphous elastomer which is not prone to hydrolysis. The crystalline part of UF resin is also resistant to hydrolytic degradation as reported in the previous publications (Park and Jeong 2011a;2011b;2011c;Park and Causin 2013;Singh et al 2014). that they were partially covered by the latex when they were blended (Fig.…”

Section: Microstructures Of Modified Uf Resinssupporting

confidence: 62%

“…Some studies investigated the hydrolysis of UF resins to understand the mechanism of bond strength loss and formaldehyde released using neat cured UF resin (Dutkiewicz 1983;1984;Tohmura et al 2000;Ringena et al 2006;Abdullah and Park 2009;Park and Jeong 2011a;2011b), and UF resin-bonded wood panel products (Irleand Bolton 1988;Ebewele et al1991;Park et al 2006;Roffael and Hüster 2012). Furthermore, some authors have attempted to examine the morphology of cured UF resins.…”

Section: Introductionmentioning

confidence: 99%

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Microstructure of Cured Urea-Formaldehyde Resins Modified by Rubber Latex Emulsion after Hydrolytic Degradation

Nuryawan¹,

Park²

2014

Journal of the Korean Wood Science and Technology

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This study investigated microstructural changes of cured urea-formaldehyde (UF) resins mixed with aqueous rubber latex emulsion after intentional acid etching. Transmission electron microscopy (TEM) was used in order to better understand a hydrolytic degradation process of cured UF resins responsible for the formaldehyde emission from wood-based composite panels. A liquid UF resin with a formaldehyde to urea (F/U) molar ratio 1.0 was mixed with a rubber latex emulsion at three different mixing mass ratios (UF resin to latex = 30:70, 50:50, and 70:30). The rate of curing of the liquid modified UF resins decreased with an increase of the rubber latex proportion as determined by differential scanning calorimetry (DSC) measurement. Ultrathin sections of modified and cured UF resin films were exposed to hydrochloric acid etching in order to mimic a certain hydrolytic degradation. TEM observation showed spherical particles and various cavities in the cured UF resins after the acid etching, indicating that the acid etching had hydrolytically degraded some part of the cured UF resin by acid hydrolysis, also showing spherical particles of cured UF resin dispersed in the latex matrix. These results suggested that spherical structures of cured UF resin might play an important role in hindering the hydrolysis degradation of cured UF resin.

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Section: Microstructures Of Modified Uf Resinssupporting

confidence: 62%

Section: Introductionmentioning

confidence: 99%

Microstructure of Cured Urea-Formaldehyde Resins Modified by Rubber Latex Emulsion after Hydrolytic Degradation

Nuryawan¹,

Park²

2014

Journal of the Korean Wood Science and Technology

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“…This is an easy concept. However, some studies found that the hydrolytic stability of UF resin increased with the decrease in F/U molar ratio [21,22]. The crystalline region detected for cured UF resin with a F/U molar ratio lower than 1.2 was supposed to be responsible for the better water resistance.…”

Section: C Nmr Resultsmentioning

confidence: 98%

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

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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.

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“…3. Another reason could be the greater free formaldehyde content in high F/U mole ratio UF resins, which had released more hydrochloric acid when ammonium chloride was used as a hardener (Pizzi, 2003;Park et al, 2008Park et al, , 2011.…”

Section: Resultsmentioning

confidence: 99%

Effect of Urea-Formaldehyde Resin Adhesive Viscosity on Plywood Adhesion

Hong¹,

Park²

2017

Journal of the Korean Wood Science and Technology

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This work was conducted to investigate on the effect of urea-formaldehyde (UF) resin viscosity on plywood adhesion. The viscosity of UF resin was controlled either by adjusting the condensation reaction during its synthesis to obtain different target viscosities (100, 200 and 300 mPa.s) at two levels of formaldehyde/urea (F/U) mole ratios (1.0 and 1.2) or by adding different amounts (10, 20 and 30%) of wheat flour into the resins for the manufacture of plywood. When the viscosity of UF resin increased by the condensation reaction, the adhesion strength of plywood bonded with UF resin of 1.2 F/U mole ratio consistently increased, while those bonded with the 1.0 F/U mole ratio resin slightly decreased, suggesting a difference in the adhesion in plywood. However, the adhesion strength of plywood decreased as the viscosity increased by adding wheat flour, regardless of F/U mole ratio. The manipulation of UF resin viscosity by adjusting the condensation reaction was much more efficient than by adding wheat flour in improving the adhesion performance of plywood. These results indicated that a way of controlling the viscosity of UF resin adhesives has a great influence to their adhesion in plywood.

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Hydrolytic stability and crystallinity of cured urea–formaldehyde resin adhesives with different formaldehyde/urea mole ratios

Cited by 134 publications

References 17 publications

Microstructure of Cured Urea-Formaldehyde Resins Modified by Rubber Latex Emulsion after Hydrolytic Degradation

Microstructure of Cured Urea-Formaldehyde Resins Modified by Rubber Latex Emulsion after Hydrolytic Degradation

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

Effect of Urea-Formaldehyde Resin Adhesive Viscosity on Plywood Adhesion

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