@article {1871, title = { Characterization and Preparation of Furanic-Glyoxal Foams }, journal = {POLYMERS}, volume = {12}, year = {2020}, pages = {692}, abstract = {

Synthetic foams have become an essential industrial product for a great variety of applications. Furfuryl alcohol, as a biomass chemical, was reacted with glyoxal at room temperature to prepare furanic-glyoxal rigid foams, and p-toluenesulfonic acid was used as a catalyst to initiate the reaction. Foams with different molar ratios (furfuryl alcohol/glyoxal) were prepared in this work, and uniform cells foams have been obtained. Their compression resistance, 24-h water absorption, density, and other basic properties were tested. Scanning electron microscopy (SEM) was used to observe the cellular morphology of the foams prepared, thermogravimetric analysis (TGA) helped to understand their thermal and combustion properties, and FTIR and Matrix Assisted Laser Desorption Ionisation Time of Flight (MALDI ToF) mass spectroscopy to explain the structure of the resulting foams to clarify the reactions occurring during foaming. The results show that the compression resistance of furanic-glyoxal foams declined as the furfuryl alcohol/glyoxal ratio decreases also. SEM observations revealed that foams with open-cell were obtained when furfuryl alcohol was added in greater amounts, and more closed cell structures were formed as the proportion of glyoxal increased. TGA results showed that the initial ignition temperature of furanic-glyoxal foams is similar to 200 degrees C higher than that of wood, and the smaller comprehensive combustion index S (about 0.15 x 10(-7) (\%2 K-3 min(-2))) indicates that the foam burns slowly and has poor flammability, that is, it is not easy to burn.

}, author = {X.D. XI and A. PIZZI and H. LEI and G.B. DU and X.J. ZHOU and Y.Y. LIN} } @article {1861, title = { Condensed tannin-glucose-based NIPU bio-foams of improved fire retardancy }, journal = { POLYMER DEGRADATION AND STABILITY }, volume = {175}, year = {2020}, abstract = {

Glucose-based self-blowing non-isocyanate polyurethanes foams were prepared in our previous work. They showed excellent properties comparable to commercial foams by just using a simple preparation procedure. These foams, nevertheless, present a critical drawback that is their flammability. In the research presented here a natural phenolic compound, condensed tannin, was tested as a flame-retardant to improve the fire resistance of glucose-based NIPU foams. A number of tannin-substituted glucose-based NIPU foams (mimosa tannin replacing glucose at 0\%, 25\% and 50\%, respectively) were prepared and characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), Thermogravimetric analysis (TG), ignition experiment and limiting oxygen index (LOI). Other physical and mechanical properties, such as foaming processes, density, compression strength, etc. were also investigated. The results indicated that the tannin-modified glucose-based NIPU foams (T/G (1/3)-Fs and (T/G (1/1)-Fs)) exhibit smaller mean cell size, improved compression strength and higher density than (T/G (0/4)-Fs). The FT-IR analysis showed that urethane linkages were formed, the chemical structure of glucose-based NIPU foam being nonetheless preserved even if the glucose was partially replaced by the condensed tannin. Thermogravimetric analysis showed that the presence of condensed tannin decreased the thermal stability of the tannin-glucose NIPU foam composites slightly. In addition, ignition experiments were also carried out in which the glucose-based NIPU foams with a condensed tannin showed longer burning time than neat (T/G (0/4)-Fs). Finally, limiting oxygen index (LOI) values from 17.5\% to 25.5\%, show a higher value with the increasing condensed tannin substitution.

}, author = {X.Y. CHEN and J.X. LI and X.D. XI and A. PIZZI and X.J. ZHOU and E. FREDON and G.B. DU and C. GERARDIN} } @article {1864, title = { Effects of Broussonetiapapyrifera leaf cutting modes on bonding performance of its protein-based adhesives }, journal = { EUROPEAN JOURNAL OF WOOD AND WOOD PRODUCTS }, volume = {78}, year = {2020}, pages = {461-470}, abstract = {

Broussonetiapapyrifera leaf protein was used as a biomass feedstock to prepare wood adhesives, and the influence of cutting modes (cutting frequencies and cutting heights) on leaf protein content and reactivity was studied in this paper. Bonding performance of Broussonetiapapyrifera leaf protein-based adhesives were evaluated by shear strength of plywood. Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetry (TG), and scanning electron microscope (SEM) were used to analyze them. The results indicated that: (1) the leaf protein content gradually increased as the cutting height increased, but it presented a decreasing trend as the cutting frequency increased. When the cutting frequency is two times per year and the cutting height is 30 cm, this leaf protein-based adhesive exhibited the best bonding strength with 0.75 MPa. (2) Cutting frequency and cutting height have no significant correlations to the reactivity of leaf protein with the crosslinker. (3) DSC and FTIR indicated that both leaf protein content and reactivity appeared to exert an influence on the bonding properties of the protein adhesives, and the latter is more pronounced. (4) TG and SEM analyses indicated that under different cutting modes, leaf protein content, especially protein reactivity, had a great effect on the thermal properties of the adhesives. (5) Contact angle analysis showed that Broussonetiapapyrifera leaf protein-based adhesives had good wettability on wood surfaces. Under different cutting modes with the difference of leaf protein content and reactivity, the crosslinking degree of the adhesives with crosslinker and compactness of the cured adhesives were different and thus affect their bonding strength and water resistance.

}, author = {Z.G. WU and X.D. XI and A. PIZZI and Y.F. XIA and Q.X. ZHAO and H. LEI and J.K. LIANG} } @article {1886, title = { No-Aldehydes Glucose/Sucrose-Triacetin-Diamine Wood Adhesives for Particleboard }, journal = { JOURNAL OF RENEWABLE MATERIALS }, volume = {8}, year = {2020}, pages = {715-725}, abstract = {

A three reagents adhesive system for wood particleboards not containing any aldehyde was developed by the reaction of glucose or sucrose with triacetin (glycerin triacetate) and with hexamethylene diamine. The system was found to be based on the mix of three reactions, namely the reaction of (i) glucose with triacetin, (ii) of the diamine with triacetin, and (iii) of glucose with the diamine. The chemical species formed were identified by Matrix Assisted Laser Desorption Ionization Time of Flight (MALDI-ToF) mass spectrometry. Wood particleboard panels were prepared with this adhesive system and gave good internal bond (IB) strength results suitable for interior grade panels and with extremely low formaldehyde emission.

}, author = {X.D. XI and A. PIZZI} } @article {1885, title = { Oxidized demethylated lignin as a bio-based adhesive for wood bonding }, journal = { JOURNAL OF ADHESION }, year = {2020}, abstract = {

Lignin was successfully modified to prepare a bio-based wood adhesive by just two synthesis steps: demethylation and periodate oxidation. Fourier Transform Infrared Spectroscopy (FT-IR), Matrix Assisted Laser Desorption Ionization Time of Flight (MALDI-TOF) Mass Spectrometry and Thermomechanical Analysis (TMA) were combined to characterize the bio-based adhesives obtained. Furthermore, the adhesion performance of the bio-based lignin adhesive was measured by testing the tensile shear strength of the bonded joints. The results show that demethylated lignin gives to the wood joint acceptable dry shear strength, but no wet shear strength. Thus, sodium peroxide (NaIO4) oxidant was used to improve the bonding performance of lignin-based adhesives. The optimal formulation for oxidized demethylated lignin adhesives was found to be by 20\% addition of NaIO4. The adhesive presented is a lignin-derived non- aldehyde addition, high biomass content, and its preparation is convenient, low-cost product and can be applied to wood bonding.

}, author = {X.Y. CHEN and X.D. XI and A. PIZZI and E. FREDON and G.B. DU and C. GERARDIN and S. AMIROU} } @article {1865, title = { Preparation and Characterization of Condensed Tannin Non-Isocyanate Polyurethane (NIPU) Rigid Foams by Ambient Temperature Blowing }, journal = {POLYMERS}, volume = {12}, year = {2020}, abstract = {

Ambient temperature self-blowing mimosa tannin-based non-isocyanate polyurethane (NIPU) rigid foam was produced, based on a formulation of tannin-based non-isocyanate polyurethane (NIPU) resin. A citric acid and glutaraldehyde mixture served as a blowing agent used to provide foaming energy and cross-link the tannin-derived products to synthesize the NIPU foams. Series of tannin-based NIPU foams containing a different amount of citric acid and glutaraldehyde were prepared. The reaction mechanism of tannin-based NIPU foams were investigated by Fourier Trasform InfraRed (FT-IR), Matrix Assisted Laser Desorption Ionization (MALDI-TOF) mass spectrometry, and C-13 Nuclear Magnetic Resonance (C-13 NMR). The results indicated that urethane linkages were formed. The Tannin-based NIPU foams morphology including physical and mechanical properties were characterized by mechanical compression, by scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). All the foams prepared showed a similar open-cell morphology. Nevertheless, the number of cell-wall pores decreased with increasing additions of glutaraldehyde, while bigger foam cells were obtained with increasing additions of citric acid. The compressive mechanical properties improved with the higher level of crosslinking at the higher amount of glutaraldehyde. Moreover, the TGA results showed that the tannin-based NIPU foams prepared had similar thermal stability, although one of them (T-Fs-7) presented the highest char production and residual matter, approaching 18.7\% at 790 degrees C.

}, author = {X.Y. CHEN and X.D. XI and A. PIZZI and E. FREDON and X.J. ZHOU and J.X. LI and C. GERARDIN and G.B. DU} } @article {1837, title = { DEVELOPMENT OF MIMOSA TANNIN-BASED ADHESIVE CROSS-LINKED BY FURFURYL ALCOHOL- FORMALDEHYDE AND EPOXY RESINS }, journal = { WOOD RESEARCH }, volume = {64}, year = {2019}, pages = {847-858}, abstract = {

A furfuryl alcohol-formaldehyde resin was synthesized as a crosslinker in our laboratory to develop a mimosa tannin-based adhesive with good water resistance. C-13 nuclear magnetic resonance and matrix-assisted laser desorption ionization time-of-flight mass spectroscopy indicated that furfuryl alcohol reacted with formaldehyde under acidic conditions and that-CH (-OH) - groups to be the ones involved in the crosslinking of mimosa tannin-furfuryl alcohol-formaldehyde adhesive (TFF). The wet shear strength of TFF-bonded plywood suggested that the cured TFF adhesive was better than mimosa tannin-furfuryl alcohol (TF) adhesive. The water resistance of TFF adhesive cross-linked with 9\% epoxy resin was also higher than those of TFF and TF adhesives.

}, author = {J. ZHANG and L.H. XIONG and X.J. ZHOU and G.B. DU and J.K. LIANG and X.D. XI} } @article {1836, title = { EFFECTS OF HEAT-TREATMENT ON BONDING PERFORMANCE OF BETULA ALNOIDES }, journal = { WOOD RESEARCH }, volume = {64}, year = {2019}, pages = {1045-1054}, abstract = {

Heat-treatment woods of Betula alnoides were prepared by using vapor as the heat-conducting medium. Effects of heat-treatment time and heat-treatment temperature on equilibrium moisture content, density, pH value, contact angle and bonding performance of Benda alnoides were discussed in this paper. The results indicated that: (1) With the increase of heat-treatment temperature, the equilibrium moisture content, density and pH value of Betula alnoides decreased gradually. (2) With the increase of heat-treatment temperature, the contact angle of Betula alnoides increased from 70.08 degrees to about 100 degrees, resulting in the reduction of bonding strength gradually. Bonding strength of Betula alnoides after heat-treatment was related with the used adhesive. Bonding strength of different adhesives decreased to different extents. The bonding strength of Betula alnoides wood with polyvinyl acetate (PVAC) resin was generally higher than that of melamine-urea-formaldehyde (MUF) resin. The former were 6.35-4.56 MPa, and the latter were 5.60-3.00 MPa. (3) Heat-treatment time influenced equilibrium moisture content, density, contact angle, pH value and bonding strength of Betula alnoides less than heat-treatment temperature. (4) Heat-treatment could affect strength and surface performance of Betula alnoides greatly and the processing medium should be extended.

}, author = {Z.G. WU and S.C. CHEN and M.F. TIAN and L.F. LI and L.P. YU and X.D. XI and J.K. LIANG and B.G. ZHANG and H. LEI and J. ZHANG and T.A. CHEN} } @article {1840, title = {Glucose-Biobased Non-Isocyanate Polyurethane Rigid Foams}, journal = { JOURNAL OF RENEWABLE MATERIALS }, volume = {7}, year = {2019}, pages = {301-312}, abstract = {

Glucose-based non-isocyanate polyurethanes (NIPU) were prepared by reaction of glucose with dimethyl carbonate and hexamethylene diamine. These were used to prepare partially biobased polyurethane foams by reaction with NaHCO3 as a blowing agent and addition of a silane coupling agent having different functions such as coreactant and adjuvant to obtain more uniform and smaller cells. The foams were foamed and hardened by applying heat. The foams presented very limited fire resistance indicating that as for synthetic polyurethane foams the eventual use of a fire retardant appears to be necessary. The 2 hours water absorption was used to indicate if close cells or open cells occur. More characteristic is their stress strain behaviour. While compression does indeed flatten the cell walls nonetheless the cellular structure is maintained and the cell walls have not been destroyed. This indicates a certain level of elasticity in the cell walls of formulations containing NaHCO3. In effect the macro-appearance of this foams, confirms this explanation as the foam is densified and holds together.

}, url = {http://tsp.techscience.com//uploads/attached/file/20190325/20190325065121_13446.pdf}, author = {X.D. XI and A. PIZZI and C. GERARDIN and G.B. DU} } @article {1808, title = { Glutaraldehyde-wheat gluten protein adhesives for wood bonding }, journal = { JOURNAL OF ADHESION }, year = {2019}, abstract = {

Wheat gluten protein hydrolysate was used as a biomass feedstock to prepare environmentally friendly protein-based adhesives, with hydrolyzed wheat protein as control. Glutaraldehyde was used to modify it to obtain a glutaraldehyde-wheat protein (GP) adhesive. Polyethylenimine (PEI) was also used as a crosslinking agent. Plywood has been prepared and tested, and its performance was used to measure the wheat gluten protein hydrolysate adhesive bonding performance. Differential scanning calorimetry (DSC) and thermomechanical analysis (TMA) were used to analyze the adhesive thermal properties and the microstructures of the cured adhesives by scanning electron microscopy (SEM). The results show that modification by glutaraldehyde can effectively improve the bonding performance of wheat protein adhesives, the plywood bonded strength having been improved by its addition. The effect of PEI as a crosslinking agent became evident. It can greatly improve the bonding properties of glutaraldehyde-modified wheat protein adhesives. TMA analysis indicates that the glutaraldehyde-modified GP adhesive has a higher storage modulus than the unmodified one. The modulus of the adhesive increased after adding the PEI cross-linking agent.

}, author = {X.D. XI and A. PIZZI and C. GERARDIN and J.J. LIAO and S. AMIROU and S. ABDALLA} } @article {1825, title = { Non-isocyanate polyurethane adhesive from sucrose used for particleboard }, journal = { WOOD SCIENCE AND TECHNOLOGY }, volume = {53}, year = {2019}, pages = {393-405}, abstract = {

Sucrose-based non-isocyanate polyurethanes (S-NIPU) were synthesized by the already codified reaction of sucrose, dimethyl carbonate and hexamethylene diamine and used for the first time as adhesives for bonding particleboard. To decrease the NIPU adhesive curing temperature, a silane coupling agent was used as a crosslinking promoter. The performance of particleboards prepared at a press temperature of 230 degrees C, 200 degrees C and 180 degrees C and a press time of 8 min, 10 min and 12 min was tested and evaluated. The structure of the oligomers obtained was detected by matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Thermomechanical analysis and differential scanning calorimetry were also used to analyze their behavior. The particleboards bonded with the S-NIPU adhesive at 230 degrees C showed excellent properties, which, however, decreased as the press time was reduced. The silane coupling agent used as a crosslinking promoter significantly reduced the curing temperature of the adhesive and allowed to obtain good bonding at a lower press temperature. The results obtained confirmed that coupling the S-NIPU adhesive with a silane used as a crosslinking promoter can yield sufficiently improved results to function as a suitable adhesive for particleboard, medium density fiberboard and other types of particulate wood panels. It was also the first time that a NIPU adhesive was used for wood bonding.

}, author = {X.D. XI and Z.G. WU and A. PIZZI and C. GERARDIN and H. LEI and B.G. ZHANG and G.B. DU} } @article {1805, title = { Polypropylene Blend with Polyphenols through Dynamic Vulcanization: Mechanical, Rheological, Crystalline, Thermal, and UV Protective Property }, journal = {POLYMERS}, volume = {11}, year = {2019}, abstract = {

Tannin and lignin were blended with polypropylene (PP) through dynamic vulcanization technique. Their influence of mechanical property, crystallinity, thermal stability, as well as ultraviolet (UV) protection property on the PP matrix was investigated and compared with native tannin and lignin. According to our experimental results, tannin and lignin undergo dynamic vulcanization and were more compatible with the PP matrix. Besides, tannin and vulcanized tannin can perform as nucleating agents of PP because of their relatively small particle size. Moreover, vulcanized tannin/lignin have a better performance on the thermal stability of PP compared with native tannin/lignin, especially PP/vulcanized lignin blend. Furthermore, vulcanized tannin/lignin present better UV protective performance, concluded from fewer changes on surface morphology, carbonyl index, crystallinity, viscosity, and tensile property.

}, url = {https://hal.univ-lorraine.fr/LERMAB-UL/hal-02196798}, author = {J.J. LIAO and N. BROSSE and A. PIZZI and S. HOPPE and X.D. XI and X.J. ZHOU} } @article {1785, title = { Preparation and Evaluation of Glucose Based Non-Isocyanate Polyurethane Self-Blowing Rigid Foams }, journal = {POLYMERS}, volume = {11}, year = {2019}, abstract = {

A partially biobased self-blowing and self-hardening polyurethane foam from glucose-based non-isocyanate polyurethanes (g-NIPU) was prepared by reaction of glucose with dimethyl carbonate and hexamethylene diamine. However, these foam types generally require a high foaming temperature. In this paper, a self-blowing foam based on g-NIPU was prepared at room temperature by using maleic acid as an initiator and glutaraldehyde as a crosslinker. Water absorption, compression resistance, and fire resistance were tested. Scanning electron microscopy (SEM) was used to observe the foam cells structure. Middle infrared (ATR FT-MIR) and Matrix Assisted Laser Desorption Ionization Time-of-Flight (MALDI-TOF) mass spectrometry were used to help to analyze the reactions during the foaming process. The results obtained showed that self- blowing rigid foams have good compression, this being directly proportional to the foam density. Increasing the amount of glutaraldehyde or reducing maleic acid thickens the cell walls and increases the density of the foams. MALDI-TOF analysis showed that g-NIPU reacts with both maleic acid and glutaraldehyde. The foams presented poor fire resistance indicating that, as for isocyanate based polyurethane foams, addition of a fire retardant would be necessary.

}, author = {X.D. XI and A. PIZZI and C. GERARDIN and H. LEI and X.Y. CHEN and S. AMIROU} } @article {1797, title = { Reactions of Soy Flour and Soy Protein by Non-Volatile Aldehydes Generation by Specific Oxidation }, journal = {POLYMERS}, volume = {11}, year = {2019}, abstract = {

Soy protein isolate (SPI) and insoluble soy flour polymeric carbohydrates have been reacted with sodium periodate for the specific oxidation of vicinal -OH groups to investigate the reactions involved in this approach to soy flour adhesives. The reactions have been shown to generate carbohydrate oligomer fractions presenting one, two or multiple aldehyde groups. With the exception of the small molecular weight heptanedial, the smaller molecular weight aldehydes generated from mono- and disaccharides by the same reaction do not appear to form from the insoluble soy flour carbohydrates, or have already reacted. The reaction of periodate with soy protein isolate has been shown to generate some aldehydes too. When the mix of SPI and soy insoluble carbohydrates is treated with periodate, the majority of the observed aldehyde carrying species appear to be higher molecular weight carbohydrate oligomer fractions.

}, author = {C.R. FRIHART and A. PIZZI and X.D. XI and L.E. LORENZ} } @article {1777, title = { Soy protein isolate-based polyamides as wood adhesives }, journal = { WOOD SCIENCE AND TECHNOLOGY }, volume = {54}, year = {2019}, pages = {89-102}, abstract = {

Soy protein isolate was reacted first with maleic anhydride and then hexamethylenediamine to synthesis soy protein isolate-based polyamides (SPIPA). Its bonding properties were measured by preparing laboratory three-layer plywood. Furthermore, a silane coupling agent (KH560), citric acid and maleic anhydride were added as cross-linkers to the SPIPA glue mix before hot pressing the panels. ATR FT-MIR and MALDI-ToF were used to determine the structures of the SPIPA, and thermomechanical analysis was used to analyze its thermomechanical properties. The results show that maleic anhydride reacts with amino acids in the soy protein molecule and then reacts with hexamethylenediamine to form carbamate-structured polyamides. This is confirmed by the ATR FT-MIR and MALDI-ToF results. Moreover, structural analysis indicates that a large number of branched structures are formed and occur in the SPIPA, rendering possible the formation of a network during curing, ensuring the bonding performance of the adhesive. The SPIPA adhesive presented good bonding strength and water resistance above the standard requirements of China National Standard GB/T 9846-2015. In particular, when maleic anhydride was added as a cross-linking agent, namely the SPIPA-MA adhesive, the panels\&$\#$39; dry and wet shear strengths were improved so that it can be considered as a suitable soy protein-based wood adhesive.

}, author = {X.D. XI and A. PIZZI and C. GERARDIN and X.Y. CHEN and S. AMIROU} } @article {1815, title = { SYNTHESIS AND CHARACTERIZATION OF LIGNIN-BASED ADHESIVE CROSS-LINKED WITH FURFURYL ALCOHOL-FORMALDEHYDE AND EPOXY RESINS }, journal = { CELLULOSE CHEMISTRY AND TECHNOLOGY }, volume = {53}, year = {2019}, pages = {449-458}, abstract = {

Lignin extracted from corn stalk was cross-linked with furfuryl alcohol-formaldehyde (FF) resin in the laboratory to prepare a bio-based adhesive, with good water resistance, for producing particleboard. The results of matrix-assisted laser desorption-ionization time-of-flight mass spectroscopy and C-13 nuclear magnetic resonance spectroscopy indicated that furfuryl alcohol reacted with formaldehyde under acidic conditions. The -CH-(OH)- groups were involved in the cross-linking of the lignin-furfuryl-formaldehyde (LFF) adhesive. The internal bond strength of the LFF-bonded particleboard showed that the cured LFF was improved and had higher performance compared to the lignin-furfuryl alcohol (LF) adhesive. The LFF with 9\% epoxy resin adhesive had an excellent modulus of elasticity, which was higher than those of PF and LF adhesives.

}, author = {J. ZHANG and X.D. XI and X.J. ZHOU and J.K. LIANG and G.B. DU and J. CAI} } @article {1793, title = { Tannin-based adhesive cross-linked by furfuryl alcohol-glyoxal and epoxy resins }, journal = { INTERNATIONAL JOURNAL OF ADHESION AND ADHESIVES }, volume = {94}, year = {2019}, pages = {47-52}, abstract = {

To prepare a natural tannin-based adhesive with good water resistance, an environment friendly furfuryl alcohol-glyoxal resin (FG) synthesized in the laboratory was developed as a cross-linker for tannin-based adhesives. C-13 Nuclear Magnetic Resonance (NMR) and Matrix-Assisted Laser Desorption-Ionization Time-of-Flight (MALDI-TOF) mass spectroscopy results indicated that furfuryl alcohol and glyoxal reacted under acidic conditions and that the -CH-(OH)- groups could be shown to be the ones involved in the cross-linking of the tannin-furfuryl-glyoxal adhesive (TFG). The results for the wet shear strength of TFG-bonded plywood showed that the cured TFG was improved and better than that bonded with a tannin-furfuryl alcohol (TF) adhesive. Moreover, the TFG adhesive cross-linked with 12\% epoxy resin (EPR) presented a good water resistance. It had a modulus of elasticity (MOE) higher than that of tannin-furfuryl alcohol-formaldehyde (TFF), TF and phenol-formaldehyde (PF) adhesives.

}, author = {J. ZHANG and X.D. XI and J.K. LIANG and A. PIZZI and G.B. DU and S.D. DENG} } @article {1817, title = { Wheat protein hydrolysates-resorcinol-aldehydes as potential cold setting adhesives }, journal = { EUROPEAN JOURNAL OF WOOD AND WOOD PRODUCTS }, volume = {77}, year = {2019}, pages = {453-463}, abstract = {

Environmental concerns about natural adhesive materials are leading to an increasing interest towards the development of ecological products. The development of new value-added uses for wheat proteins led us to develop protein-based wood adhesives. Different protein cold-setting resins were formulated by reacting the protein hydrolysates with different aldehydes (formaldehyde, glyoxal and glutaraldehyde). Wood bonded with cold-setting protein adhesive with different aldehydes met the requirements for interior and exterior conditions, and the characterization was similar to those of conventional PRF (phenol-resorcinol-formaldehyde) adhesives. As the results indicate, both glyoxal and glutaraldehyde are able to react with wheat protein hydrolysates and are viable alternatives to formaldehyde and prospectively seem more environmentally friendly. Matrix-assisted laser desorption ionisation time-of-flight (MALDI-TOF) analysis allowed the identification of the main oligomer species obtained. The analysis showed that resin prepared with glutaraldehyde is not a simple mix of resorcinol-glutaraldehyde oligomers and amino acid, but a much more complex combination of various species including amino acid-glutaraldehyde and amino acid-resorcinol oligomers.

}, author = {S. AMIROU and A. PIZZI and X.D. XI} } @article {1765, title = { AN ECO-FRIENDLY UREA-FORMALDEHYDE RESIN: PREPARATION STRUCTURE AND PROPERTIES }, journal = { WOOD RESEARCH }, volume = {63}, year = {2018}, pages = {45-56}, abstract = {

The preparation, structures and properties of UF resin prepared with concentrated formaldehyde at a low molar ratio F/U=1.1 were studied in this paper. According to the results obtained from C-13-NMR, FT-IR and DMA, UF resin prepared with concentrated formaldehyde showed better mechanical properties and heat resistance and lower formaldehyde emission responsible for its high degree of polycondensation and crosslinking than that of UF prepared with common formaldehyde, but its stability was so bad due to its high content of ether bridges. However, it was stated that adding hydrolyzed soy protein to this UF resin at the first alkali preparation stage of \"alkali-acid-alkali\", its stability got improved due to the increase of methylene bridges, which was the key contribution to polycondensation.

}, author = {Z.G. WU and X.D. XI and L.P. YU and L. SU and H. LEI and G.B. DU and Z.W. YIN} } @article {1743, title = { Isocyanate-Free Polyurethane Coatings and Adhesives from Mono- and Di-Saccharides }, journal = {POLYMERS}, volume = {10}, year = {2018}, abstract = {

Mostly biosourced non-isocyanate polyurethanes (NIPU) were prepared from mono- and disaccharides, namely glucose and sucrose, reacted with dimethyl carbonate and hexamethylene diamine. The main aim of this research was to show that NIPU can be prepared from mono- and disaccharides, this just being an initial exploratory work and its sole main aim. The oligomers obtained were detected by MALDI-ToF, CP-MAS C-13 NMR, and FTIR spectrometries. The glucose-derived NIPU were shown to harden at a markedly lower temperature than the sucrose-derived ones and to be easier to handle and spread. The NIPU obtained were applied as wood and steel surface coatings and tested by the sessile drop test (on wood) and cross-cut test (on steel) with encouraging results. The glucose NIPU gave good surface coating results already at 103 degrees C, while the sucrose NIPU yielded good results only at a markedly higher temperature of hardening. The NIPU saccharide resins were also tested as thermosetting wood joint adhesives with the glucose NIPU yielding very encouraging results.

}, author = {X.D. XI and A. PIZZI and L. DELMOTTE} } @article {1767, title = { Melamine-Glyoxal-Glutaraldehyde Wood Panel Adhesives without Formaldehyde }, journal = {POLYMERS}, volume = {10}, year = {2018}, abstract = {

(MGG\&$\#$39;) resin adhesives for bonding wood panels were prepared by a single step procedure, namely reacting melamine with glyoxal and simultaneously with a much smaller proportion of glutaraldehyde. No formaldehyde was used. The inherent slow hardening of this resin was overcome by the addition of N-methyl-2-pyrrolidone hydrogen sulphate ionic liquid as the adhesive hardener in the glue mix. The plywood strength results obtained were comparable with those obtained with melamine-formaldehyde resins pressed under the same conditions. Matrix assisted laser desorption ionisation time of flight (MALDI ToF) and Fourier transform Infrared (FTIR) analysis allowed the identification of the main oligomer species obtained and of the different types of linkages formed, as well as to indicate the multifaceted role of the ionic liquid. These resins are proposed as a suitable substitute for equivalent formaldehyde-based resins.

}, author = {X.D. XI and A. PIZZI and S. AMIROU} } @article {1727, title = { Reactions with Wood Carbohydrates and Lignin of Citric Acid as a Bond Promoter of Wood Veneer Panels }, journal = { POLYMERS }, volume = {10}, year = {2018}, abstract = {

The reaction of citric acid with wood veneers was studied by Cross Polarization Magic Angle Spinning Nuclear Magnetic Resonance (CP MAS C-13 NMR) and matrix assisted laser desorption ionization time of flight (MALDI ToF) mass spectrometry. The analysis showed that reactions of citric acid occurred with both lignin and carbohydrate constituents of wood. The reactions occurring are esterifications between the carboxylic acid functions of citric acid and the numerous aromatic and aliphatic hydroxyl groups of the main wood constituents. Reaction of citric acid with glucose as a simple model compound of carbohydrates hydroxyl groups also yielded reactions leading to linear and branched oligomers by esterification. The result indicate that the reactions of esterification are accompanied in parallel by some internal rearrangements of lignin. The applied results on bonding wide flat wood surfaces such as veneers to obtain LVL panels yielded excellent strength results even if the conditions of pressing were more drastic than what is usual for this application. The applied bonding results have shown that citric acid has great potential to be used as a bio-binder for wood veneers.

}, author = {C. DEL-MENEZZI and S. AMIROU and A. PIZZI and X.D. XI and L. DELMOTTE} }