Melamine–Glyoxal–Glutaraldehyde Wood Panel Adhesives without Formaldehyde
Abstract
:1. Introduction
2. Materials and Methods
2.1. Preparation of N-Methyl-2-Pyrrolidone Hydrogen Sulphate ([HNMP] [HSO4−]) Ionic Liquid
2.2. Preparation of MG and MGG’ Resins
2.3. Fourier Transform Infrared Spectrometry (FTIR)
2.4. Matrix Assisted Laser Desorption Ionisation Time of Flight (MALDI-ToF) Spectrometry
2.5. Plywood Preparation and Testing
3. Results and Discussion
3.1. Adhesives Bonding Performance
3.2. Analysis of Chemical Species Formed in the Reactions Analysed by MALDI-ToF Spectrometry
3.3. Analysis of Reactions by Fourier Transform Infrared (FTIR) Spectrometry
3.4. Summary of Effects
- 1.
- IL appears to catalyse the reaction of aldehydes, and aldehydes pre-reacted with urea or melamine, to yield aldol condensation. It allows aldol condensation even of aldehydes that have been pre-reacted with melamine or even with wood lignin. An example (Scheme 11):
- 2.
- IL catalyses the hardening of melamine–aldehyde resins to decrease hardening temperature, energy of activation of the hardening/condensation reaction and thus equally to improve their performance at equal temperature.
- 3.
4. Conclusions
Acknowledgments
Author Contributions
Conflicts of Interest
References
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Resin Type | Relative Mixing Molar Ratio Glyoxal:Glutaraldehyde | Melamine (g) | Glyoxal (40% Solution) (g) | Glutaraldehyde (50% Solution) (g) |
---|---|---|---|---|
MG | 100:0 | 25.2 | 174 | 0 |
MGG’1 | 95:5 | 25.2 | 163.5 | 12 |
MGG’2 | 90:10 | 25.2 | 156.6 | 24 |
MGG’3 | 85:15 | 25.2 | 147.9 | 36 |
MGG’4 | 80:20 | 25.2 | 139.2 | 48 |
MGG’4 | 75:25 | 25.2 | 130.5 | 60 |
Name of Resin | Relative Mixing Mole Ratio of Glyoxal:Glutaraldehyde | Solid Content/% | Viscosity/mPa·s | Dry Shear Strength/MPa | 24 h Cold Water Shear Strength/MPa | 2 h Boiling Water Shear Strength/MPa |
---|---|---|---|---|---|---|
MG | 100:0 | 49 | 390 | 0.6 | 0.63 | -- |
MGG’1 | 95:5 | 48.9 | 410 | 0.6 | 0.9 | -- |
MGG’2 | 90:10 | 48.8 | 540 | 0.59 | 1.02 | -- |
MGG’3 | 85:15 | 48.7 | 1720 | 0.76 | 1.39 | 0.45 |
MGG’4 | 80:20 | 48.5 | 2890 | 0.73 | 1.48 | 0.7 |
MGG’4 | 75:25 | solidified in the reactor |
Peak | Chemical Species |
---|---|
199–200 Da = calculated 197 Da, proton = 198 Da | |
138 Da = 140 Da, glyoxal dimer by aldol condensation | |
By aldol condensation as: | |
234 Da = 230 Da calculated, plus protonated, by aldol condensation, with Na+ | |
366–367 Da = 366 Da calculated, without Na+ | |
387 Da = 366 Da + 23 Da = as above but with Na+487–488 Da = with Na+ | |
Peak | Chemical Species |
---|---|
199–200 Da = calculated 197 Da, proton = 198 Da without Na+ | |
222 Da = as 199–200 but with Na+, however it is also possible 224 Da = 225 Da calculated with Na+ obtained by aldol condensation | |
328.6 Da = 304 Da + 23 = 327 Da calculated, glutaraldehyde trimer by aldol condensation with Na+ | |
by aldol condensation, thus as | |
but also at 325 Da (observed 324 Da) thus more probable: | |
as well as coupling with [HSO4−] (see example of the 424 Da peak). 424 Da = 426 calculated, glutaraldehyde tetramer by aldol condensation with Na+but also | |
and also | |
but also protonated + [HSO4−] such as | |
524 Da = glutaraldehyde pentamer by aldolcondensation, with Na+ but also the alternatives as for the 424 Da peak | --- |
624 Da = glutaraldehyde hexamer by aldolcondensation, with Na+ but also the alternatives as for the 424 Da peak | --- |
724 Da = glutaraldehyde heptamer by aldolcondensation, with Na+ but also the alternatives as for the 424 Da peak | --- |
Peak | Chemical Species |
---|---|
200 Da = [HNMP] [HSO4−], calculated 197 Da, + protonation. 536–539 Da = 539 Da calculated (516 + Na+ = 539) | |
Peak | Chemical Species |
---|---|
149–151 Da = Melamine + 23 Da (Na+) with and without IL 159 Da = G + G’ by aldol condensation with and without IL. Small with IL 184–185 Da = M(Glyox)1 without Na+ in MGG’ with IL 197.8 Da = [HNMP] [HSO4−] (only present in MGG’ with IL) 234 Da = aldol condensation of glyoxal + Na+ exists only in MGG’ + IL | |
331.5 Da = 328.6 Da glutaraldehyde+IL by aldol condensation occurs but is relatively small in MGG’ + IL | |
But also 331.5 = 310 + Na+ (333 calculated deprotonated = 332) in MGG’ + IL | |
395 Da = 392 Da (369 + 23) calculated. MGG’ + IL with Na+ | |
439 Da = MG5 + Na+, present in only MGG’ | |
496 Da = 491 Da (with Na+), probably multiprotoated, in MGG’ + IL (= GMGMG’) | |
521 Da = 516/518 calculated = MG5G’ without Na+ or MG5G’ without Na+ of MGG’ + IL 536–539 Da = MG5G’ + Na+ | |
557.4 Da = 558 Da calculated = MG4G2’ of MGG’ + IL without Na+ 566 Da without Na+, in MGG’ 581.7 Da = 581 calculated = MG4G2’ with Na+ in MGG’ + IL 588 Da with Na+. 588 Da in both MGG’ and MGG’ + IL | |
736–738 Da = 738 deprotonated, without Na+ In both MGG’ and MGG”+IL | |
795–796 Da = without Na+ in both MGG’ and MGG’ + IL | |
993 Da = 992 Calculated + protonated with Na+, only in MGG’ | |
1010 Da = 1008 Da calculated + protonated, only in MGG’ | |
1169 Da = 1168 Da calculated, Without Na+ | |
Wavelength/cm−1 | Group |
---|---|
812 | triazine bending vibration |
1074.3 | C–O stretching vibration |
1235 | C–O–C (ether group) stretching vibration |
1460.1 | Methylene C–H bending vibration |
1543 | Triazine C=N bending vibration |
1550.8 | Triazine C=N bending vibration |
1678 | C=O(carbonyl) stretching vibration |
1735.9 | C=O(ketone) stretching vibration |
2739 | C–H stretching vibration |
2962.7 | C–H(aldehyde) stretching vibration |
3100–3200 | N–H, O–H stretching vibration |
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Xi, X.; Pizzi, A.; Amirou, S. Melamine–Glyoxal–Glutaraldehyde Wood Panel Adhesives without Formaldehyde. Polymers 2018, 10, 22. https://doi.org/10.3390/polym10010022
Xi X, Pizzi A, Amirou S. Melamine–Glyoxal–Glutaraldehyde Wood Panel Adhesives without Formaldehyde. Polymers. 2018; 10(1):22. https://doi.org/10.3390/polym10010022
Chicago/Turabian StyleXi, Xuedong, Antonio Pizzi, and Siham Amirou. 2018. "Melamine–Glyoxal–Glutaraldehyde Wood Panel Adhesives without Formaldehyde" Polymers 10, no. 1: 22. https://doi.org/10.3390/polym10010022
APA StyleXi, X., Pizzi, A., & Amirou, S. (2018). Melamine–Glyoxal–Glutaraldehyde Wood Panel Adhesives without Formaldehyde. Polymers, 10(1), 22. https://doi.org/10.3390/polym10010022