@article {1882, title = { Ionic liquid-modified lignin as a bio-coupling agent for natural fiber-recycled polypropylene composites }, journal = { COMPOSITES PART B-ENGINEERING }, volume = {181}, year = {2020}, abstract = {

In this study, the influence of ionic liquid-treated lignin as a bio coupling agent on the various properties of bagasse fiber-recycled polypropylene composites was investigated. For this purpose, extracted lignin from Bagasse Soda black liquor was modified with 1-ethyl-3-methylimidazolium acetate ([Emim] [OAc]) ionic liquid and then different ratios of unmodified and modified lignin (0, 1, 3 and 5 wt\%) were added to the bagasse fiber/recycled polypropylene mixture. The composites were then manufactured by injection molding after mixing mechanically of the bagasse fiber, virgin or modified lignin and recycled polypropylene. Structural and thermal properties of lignin after modification by ionic liquid along with physical (water absorption and thickness swelling) and mechanical (flexural modulus, flexural strength, tensile strength and impact strength) properties of the manufactured composites were measured according to ASTM standard methods. The FTIR analysis indicated lignin rearrangements showing that some bonds changed or formed after its modification with IL. The DSC analysis showed that the glass transition temperature (T-g) of lignin decreased from 92 degrees C to 80 degrees C by increasing the weight ratio of ionic liquid to lignin from 20 to 30 wt\%. The panel testing results indicated that all physical and mechanical properties of the composites were continuously improved by increasing the lignin content from 1 to 5 wt\%. Thus, the composites with IL-treated lignin presented higher dimensional stability and mechanical strength compared to those prepared with unmodified lignin. Scanning electron microscopy (SEM) showed that treatment with ionic liquid improves the uniform dispersion of lignin in the polymer matrix.

}, author = {H. YOUNESI-KORDKHEILI and A. PIZZI} } @article {1853, title = { Oxidized polyethylene as a new alternative coupling agent for the fiberboards made from UF resin }, journal = { JOURNAL OF ADHESION }, volume = {96}, year = {2020}, pages = {665-678}, abstract = {

The aim of this research was to improve the bonding of bagasse fiber panels with urea formaldehyde (UF) resins by incorporating oxidized polyethylene (OPE) as a new coupling agent. To reduce the panels formaldehyde emission and to improve their water resistance was an additional aim of this work. Thus, different proportions of OPE (5, 10 and 15\%) were added during the UF resin preparation instead to the second urea. The resins were then used in the production of UF-bonded bagasse fiber panels. The physicochemical, structural and thermal properties of the resins as well as water absorption, flexural properties, internal bond strength (IB) and formaldehyde emission of the panels bonded with them were measured according to standard methods. According to the FTIR spectra, the absorbance related to C = C and C = O bonds increased due to the addition of OPE to the UF resin. DSC analysis indicated that in comparison to UF resin, the curing process of UF resin containing OPE occurred at a lower temperature. The gel time shortened and the viscosity increased by the addition of OPE to the UF resin. The panels containing OPE yielded higher IB, flexural modulus and strength compared to those made from pure UF resins. The panels bonded with modified UF resins also showed lower formaldehyde emission and water absorption. Based on finding of this work, the panels containing 15\% OPE emitted less formaldehyde, had higher mechanical strength and better dimensional stability than other percentages OPE-modified UF adhesives.

}, author = {H. YOUNESI-KORDKHEILI and A. PIZZI} } @article {1761, title = { A comparison between the influence of nanoclay and isocyanate on urea-glyoxal resins }, journal = { INTERNATIONAL WOOD PRODUCTS JOURNAL }, volume = {9}, year = {2018}, pages = {9-14}, abstract = {

The effects of pMDI and nanoclay on physical and mechanical properties of particleboards bonded with a urea-glyoxal (UG) resin were compared. pMDI (4, 6 and 8\%) and nanoclay (1, 2 and 3\%) were added to the synthesised UG resin. The properties of the resins prepared as well as of the particleboard panels bonded with them were then measured. The gel time shortened and the viscosity increased by addition of both pMDI and nanoclay into a UG resin. Differential Scanning Calorimetry (DSC) showed that the addition of pMDI decreased the onset, curing and peak temperatures of the UG resin. Nanoclay instead, only decreased the peak temperature of the UG resin. The particleboards bonded with UG resins/isocyanate yielded lower water absorption and percentage thickness swelling when compared to those bonded with the UG resin/nanoclay and the control UG resins. The mechanical properties of the particleboards bonded with UG resins could be significantly improved by the addition of increasing percentages of nanoclay and pMDI. The panels where pMDI was added to the UG resin presented higher flexural modulus, flexural strength and IB strength compared to those bonded with UG resins containing nanoclay.

}, author = {H. YOUNESI-KORDKHEILI and A. PIZZI} } @article {1740, title = { Improving the physical and mechanical properties of particleboards made from urea-glyoxal resin by addition of pMDI }, journal = { EUROPEAN JOURNAL OF WOOD AND WOOD PRODUCTS }, volume = {76}, year = {2018}, pages = {871-876}, abstract = {

The effect of pMDI on physical and mechanical properties of the particleboards made from urea-glyoxal resin was investigated. The nontoxic and ecofriendly urea-glyoxal (UG) resin was synthesized under weak acid conditions, and its different properties were measured. Then, pMDI at various contents (4, 6 and 8\% on resin solids) was added to the UG resin prepared. The thermal and physicochemical properties of the resins prepared as well as their water absorption, flexural properties (flexural modulus and strength) and internal bond (IB) strength of the particleboard panels bonded with them were measured according to standard methods. According to the physicochemical results obtained, the addition of pMDI significantly accelerated the gel time and increased the viscosity and solids content of UG resins. Differential scanning calorimetry indicated that the addition of pMDI decreases the onset and curing temperatures of the UG resin. Physical analysis results of the panels indicated that the particleboards made from UG resins with isocyanate yielded lower water absorption when compared to those bonded with the control UG resins. Based on the findings of this research work, the mechanical properties of particleboard panels bonded with UG resins could be significantly enhanced by the addition of increasing percentages of pMDI. The panels having 8 wt\% pMDI exhibited the highest flexural modulus, flexural strength and IB strength value and the lowest water absorption among all the panels prepared.

}, author = {H. YOUNESI-KORDKHEILI and A. PIZZI} } @article {1769, title = { Improving the properties of ionic liquid-treated lignin-urea-formaldehyde resins by a small addition of isocyanate for wood adhesive }, journal = { JOURNAL OF ADHESION }, volume = {94}, year = {2018}, pages = {406-419}, abstract = {

The aim of this research was to investigate the effect of polymeric 4, 4 diphenyl methane diisocyanate (pMDI) on the physical and mechanical properties of plywood panels bonded with an ionic liquid (IL)-treated lignin-urea-formaldehyde resin. Soda lignin modified by 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]) IL was added to a urea formaldehyde (UF) resin during resin synthesis to prepare a lignin-urea-formaldehyde (LUF) resin. pMDI at various contents (2, 4, and 6\% on resin solids) was then added to prepare a LUF resin. The thermal and physicochemical properties of the resins prepared as well as the water absorption, shear strength, and formaldehyde emission of the plywood panels bonded with them were measured according to standard methods. DSC analysis indicated that the addition of pMDI decreases the gel onset and curing temperatures of the LUF resin. According to the results obtained, the addition of pMDI significantly increased the viscosity and solid content and accelerated the gelation time of LUF resins. Based on the findings of this research, the addition of pMDI dramatically improves the performance of LUF resins as a new adhesive for wood-based panels. The LUF resins with isocyanate added yielded panels presenting lower formaldehyde emission and lower water absorption content when compared to those bonded with the control LUF resins. Greater dry and wet shear strength can be obtained by a small addition of pMDI to LUF resins.

}, author = {H. YOUNESI-KORDKHEILI and A. PIZZI and A. MOHAMMADGHASEMIPOUR} } @article {1764, title = { Properties of plywood panels bonded with ionic liquid-modified lignin-phenol-formaldehyde resin }, journal = { JOURNAL OF ADHESION }, volume = {94}, year = {2018}, pages = {143-154}, abstract = {

The aim of this research was to investigate the physical and mechanical properties of plywood panels bonded with ionic liquid-modified lignin-phenol-formaldehyde (LPF) resin. For this purpose, soda bagasse lignin was modified by 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]) ionic liquid, and then, various contents of modified lignins (10, 15, and 20 wt\%) were added as a substitute of phenol in phenol-formaldehyde (PF) resin synthesis. The properties of the synthesized resin were compared with those of a control PF resin. The changes in curing behavior of the resins prepared were analyzed by differential scanning calorimetry (DSC). The physical properties of the resins prepared, as well as the water absorption, thickness swelling, shear strength, and formaldehyde emission of the plywood panels bonded with these adhesives, were measured according to standard methods. DSC analysis indicated that in comparison with PF resins, curing of the LPF resin occurred at lower temperatures. The physical properties of the synthesized resins indicated that viscosity and solid content increased, while gel time and density decreased by addition of treated lignin to the PF resin. Although the panels containing resins with modified lignin yielded low formaldehyde emission, their dimensional stability was worse than those bonded with a commercial PF adhesive. The plywood prepared using IL-treated lignin PF resins has shear strength, which satisfy the requirements of the relevant standards specifications and significantly better than that of panels prepared with the control PF resin. The mechanical properties of the panels could be significantly enhanced with increased percentage of treated lignin content from 0 to 20 wt\%.

}, author = {H. YOUNESI-KORDKHEILI and A. PIZZI} } @article {1693, title = { A comparison between lignin modified by ionic liquids and glyoxalated lignin as modifiers of urea-formaldehyde resin }, journal = { JOURNAL OF ADHESION }, volume = {93}, year = {2017}, pages = {1120-1130}, abstract = {

The aim of this research was to compare the influence of modified lignin by ionic liquid (IL) on the physical and mechanical properties of wood-based panels bonded with urea-formaldehyde (UF) resin with the effect of glyoxalated lignin (GL) on UF properties. For this purpose, soda bagasse lignin was respectively modified by 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]) IL and glyoxal and then the various content of modified lignins (10, 15, and 20\%) were added at pH=7 during the UF resin synthesis instead of the second urea. The changes in the structure and thermal properties of lignin, after and before modification with glyoxal and IL, were analyzed by Fourier transform infrared spectrometry (FTIR) and differential scanning calorimetry (DSC). The physicochemical properties of the prepared resins as well as the water absorption, shear strength, and formaldehyde emission of the plywood panels made with these adhesives were measured according to standard methods. According to the FTIR spectra, the content of C=O bond increased in GL while in the IL-treated lignin the content of C-N bond markedly increased. DSC analysis indicated that lignin modified by IL had lower glass transition temperature (T-g) value compared to those modified with glyoxal and unmodified lignin, respectively. The UF resins containing IL-treated lignin exhibit a faster gel time compared to those prepared with GL. Equally, the plywood panels prepared with an IL had lower formaldehyde emission and higher mechanical strength compared to those made from UF resin containing GL. There were no significant differences in dimensional stability of the panels bonded with UFs modified with GL and those with IL-modified lignin.

}, author = {H. YOUNESI-KORDKHEILI and A. PIZZI} } @article {1695, title = { The effect of soda bagasse lignin modified by ionic liquids on properties of the urea-formaldehyde resin as a wood adhesive }, journal = { JOURNAL OF ADHESION }, volume = {93}, year = {2017}, pages = {914-925}, abstract = {

The aim of this research was to investigate the influence of lignin modified by ionic liquids on physical and mechanical properties of plywood panels bonded with the urea-formaldehyde (UF) resin. For this purpose, soda bagasse lignin was modified by the 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]) ionic liquid and then the various contents of unmodified and modified lignins (10, 15, and 20\%) were added at pH=7 instead of second urea during the UF resin synthesis. The physicochemical properties of the prepared resins as well as the water absorption, shear strength, and formaldehyde emission of the plywood panels made with these adhesives were measured according to standard methods. According to Fourier Transform Infrared (FTIR) Spectrometry, by treatment of lignin, the C=O, C-C, and C-H bonds decrease while the content of the C-N bond dramatically increases. Based on the finding of this research, the performance of soda bagasse lignin in UF resins dramatically improves by modification by ILs; as the resins with modified lignin yielded lower formaldehyde emission and water absorption when compared to those made from unmodified lignin and commercial UF adhesives, respectively. The shear strength as well as wood failure percentages are lower for the panels produced with modified lignin than for the panels produced with UF resins alone.

}, url = {https://hal.univ-lorraine.fr/hal-01599537}, author = {H. YOUNESI-KORDKHEILI and A. PIZZI and A. HONARBAKHSH-RAOUF and F. NEMATI} } @article {1644, title = { Acid Ionic Liquids as a New Hardener in Urea-Glyoxal Adhesive Resins }, journal = { POLYMERS }, volume = {8}, year = {2016}, abstract = {

The effect of acidic ionic liquid (IL) as a new catalyst on the properties of wood-based panels bonded with urea-glyoxal (UG) resins was investigated. Different levels of N-methyl-2-pyrrolidone hydrogen sulfate ([HNMP] HSO4 (0, 1, 2, 3 wt \%)) were added to prepared UG resin. The resin was then used for preparing laboratory particleboard panels. Then, the properties of the prepared panels were evaluated. The structure of the prepared UG resin was studied by C-13 NMR, and thermal curing behavior of the resin before and after the addition of IL was measured by DSC. Additionally, the main oligomers formed in the UG reaction were identified by matrix-assisted laser desorption/ionization time-of-flight (MALDI TOF) mass spectroscopy. The results indicated that IL can be used as an efficient catalyst for UG resin. The physicochemical tests indicated that the addition of [HNMP] HSO4 from 0 to 3 wt \% decreased the pH value of the glue-mix, and the pH decreased on curing to the same level as urea-formaldehyde resins. The gel accelerated with increasing catalyst content and with the decreasing of the pH in the UG resin. The panels prepared with IL had higher mechanical strength and dimensional stability compared to those made from UG resins containing NH4Cl. Scanning electron microscope (SEM) micrographs showed that the panels prepared with ionic liquid presented low porous. DSC analysis showed that the addition of IL to the UG resin decrease the energy of activation of the curing reaction to render possible cross-linking. The MALDI TOF results indicated a preponderant linearity of the oligomers formed, implying a high energy of activation of curing for UG resins.

}, url = {https://hal.univ-lorraine.fr/LERMAB-UL/hal-01599588}, author = {H. YOUNESI-KORDKHEILI and A. PIZZI} } @article {1654, title = { Reduction of Formaldehyde Emission from Particleboard by Phenolated Kraft Lignin }, journal = { JOURNAL OF ADHESION }, volume = {92}, year = {2016}, pages = {485-497}, abstract = {

The aim of this study was the reduction of formaldehyde emission from particleboard by phenolated Kraft lignin. For this purpose, the lignin was extracted from black liquor and then modified by phenolation. During the urea formaldehyde (UF) resin synthesis different proportions of unmodified and phenolated Kraft lignins (10\%, 15\%, and 20\%) were added at pH = 7 instead of the second urea. Physicochemical properties and structural changes of resins so prepared, as well as the internal bond (IB) strength and formaldehyde emission associated with the panels bonded with them were measured according to standard methods. The Fourier transform infrared (FTIR) analysis of lignin indicated that the content of O-H bonds increased in phenolated lignin while the aliphatic ethers C-O bonds decreased markedly in the modified lignin. Since both synthesis of UF resins and lignin phenolation are carried out under acid conditions, phenolation is an interesting way of modifying lignin for use in wood adhesive. The panels bonded with these resins showed significantly lower formaldehyde emission compared to commercial UF adhesives. The UF resin with 20\% phenolated lignin exhibited less formaldehyde release without significant differences in internal bond strength and physicochemical properties compared to an unmodified UF resin. XRD analysis results indicated that addition of phenolated lignin decreased the crystallinity of the hardened UF resins.

}, url = {https://hal.archives-ouvertes.fr/hal-01599783}, author = {H. YOUNESI-KORDKHEILI and A. PIZZI and G. NIYATZADE} } @article {1589, title = { Improving urea formaldehyde resin properties by glyoxalated soda bagasse lignin }, journal = { EUROPEAN JOURNAL OF WOOD AND WOOD PRODUCTS }, volume = {73}, year = {2015}, pages = {77-85}, abstract = {

The aim of this research was a reduction of formaldehyde emission and the improvement of the water resistance of urea formaldehyde (UF) resins by incorporating glyoxalated soda bagasse lignin. For this purpose, various contents of unmodified and glyoxalated lignins (10, 15 and 20 \%) were added at pH = 7 instead of second urea during the UF resin synthesis. The properties of the resins as well as water absorption, shear strength, and formaldehyde emission of plywood panels made with these adhesives were measured. Among all the resins synthesized, the resin yielding the best results (based on formaldehyde emission and gelation time as well as water absorption, mechanical strength, and formaldehyde content of the associated panels) was selected, and its properties were further analyzed by Differential Scanning Calorimetry (DSC), Fourier Transform Infrared Spectrometry (FTIR), and X-ray Diffractometry (XRD). The lignin based resins yielded good shear strength of the plywood panels, passing comfortably relevant international standard specifications; the panels also showed lower formaldehyde emission and water absorption when compared to commercial UF adhesives. Based on these findings, it was attempted to improve the performance of soda bagasse lignin in UF resins by glyoxalation. The UF resin containing 15 \% glyoxalated lignin (GLUF15) still exhibited less water absorption and formaldehyde release without significant differences in shear strength and physicochemical properties compared to the UF resin control. DSC analysis indicated that in comparison to UF resin the curing process of GLUF resin shifted to lower temperatures. According to the FTIR spectra, by addition of lignin the proportion of C-N bond in methylene linkages decreases when urea is partly replaced by lignin or glyoxalated lignin. XRD analysis indicated that the crystallinity of the UF resins decreased with addition of glyoxalated lignin.

}, url = {https://hal.archives-ouvertes.fr/hal-01597471}, author = {H. YOUNESI-KORDKHEILI and S. KAZEMI-NAJAFI and R.B. ESHKIKI and A. PIZZI} }