Properties of plywood panels bonded with ionic liquid-modified lignin–phenol–formaldehyde resin

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%.     

A comparison between lignin modified by ionic liquids and glyoxalated lignin as modifiers of urea-formaldehyde resin

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.     

Use of organosolv lignin in phenol-formaldehyde resins for particleboard production: II. Particleboard production and properties

The objective of this work was to demonstrate the utility of lignin-based resins designed for application as an adhesive in the production of particleboard. Bond qualities of lignin-phenol-formaldehyde resins, phenolated-lignin-formaldehyde resins and commercial phenol-formaldehyde (PF-com) resin were assessed by using an automatic bonding evaluation system, prior to production of particleboards. In order to evaluate the quality of lignin-based resins, particleboards were produced and physical and mechanical properties were investigated. These physical properties included internal bond, modules of rupture and modulus of elasticity. Thickness swell and water absorption properties of particleboards bonded with lignin-based resins were also determined. The lignin-based resins have been reported previously in Part I of this study. The results showed that particleboards bonded with phenolated-lignin formaldehyde resins (up to 30% lignin content) exhibited similar physical and mechanical properties when compared to particleboards bonded with PF-com. The work has indicated that phenolated-lignin formaldehyde resins (up to 30% substitution level) can be used successfully as a wood adhesive for constructing particleboard. The performance of these panels is comparable to those of boards made using PF-com resin.     

Improving the properties of ionic liquid-treated lignin-urea-formaldehyde resins by a small addition of isocyanate for wood adhesive

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.     

Effect of resin type and content on properties of composite particleboard made of a mixture of wood and rice husk

This study investigated the effect of resin type and content on the dimensional stability and mechanical properties of single-layer composite particleboards made of a mixture of wood particles (70 wt%) and rice husk particles (30 wt%). Two types of resin, urea–formaldehyde (UF) resin and phenol–formaldehyde (PF) resin, were used in the experiments at three different contents which were 8, 10, or 12 wt%. The dimensional stability of the samples was significantly improved by increasing the resin content. When the contents of the UF and PF resins increased from 8 to 12 wt%, the WA values of the samples decreased to18% and 33%, respectively. Similar results were also observed for the TS values. The UF resin bonded samples swelled two times more than the PF resin bonded particleboard. The mechanical properties of the PF resin bonded samples were better than the UF resin bonded samples. When the contents of the UF and PF resins increased from 8% to 12 wt%, the internal bond strength values of the samples increased to 21% and 41%, respectively. The bending strength and modulus of elasticity of the samples were not significantly increased by increasing contents of the UF and PF resins, except for the 12 wt% content.     

The effect of soda bagasse lignin modified by ionic liquids on properties of the urea–formaldehyde resin as a wood adhesive

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.     

Reduction of Formaldehyde Emission from Particleboard by Phenolated Kraft Lignin

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.     

Improving Hot-Water Resistance of Melamine-Urea-Formaldehyde by Addition of PolyFox PF-151N Polymer

Melamine urea formaldehyde (MUF) thermosetting wood adhesives have poor performance at elevated temperatures and humid conditions. PolyFox PF-151N polymer was mixed at different loadings (0.05, 0.1, 0.5, and 1%) with MUF to improve properties, especially water resistance and bond strength. The physical properties of the optimized MUF/PolyFox PF-151N resins were measured. In order to evaluate the quality of optimized MUF/PolyFox PF-151N resins, particleboards were produced and physical and mechanical properties were investigated.

The results show that it is possible to add PolyFox PF-151N up to 0.1% to the MUF resin without altering the mechanical properties of the commercial MUF. The mechanical properties of the particleboard panels bonded with the optimal MUF/PolyFox PF-151N (99.9/0.1 by weight) resin were considerably increased as compared to the panels glued with neat MUF resin. The use of PolyFox significantly reduced 2-h and 24-h thickness swelling compared to the control panels.     

Influence of nanoclay on urea–glyoxalated lignin–formaldehyde resins for wood adhesive

In this research, the influence of nanoclay on urea–glyoxalated lignin–formaldehyde (GLUF) resin properties has been investigated. To prepare the GLUF resin, glyoxalated soda baggase lignin (15 wt%) was added as an alternative for the second urea during the UF resin synthesis. The prepared GLUF resin was mixed with the 0.5%, 1%, and 1.5% nanoclay by mechanically stirring for 5 min at room temperature. The physicochemical properties of the prepared resins were measured according to standard methods. Then the resins were used in particleboard production and the physical and mechanical properties of the manufactured panels were determined. Finally, from the results obtained, the best prepared resin was selected and its properties were analyzed by differential scanning calorimetry (DSC), Fourier transform infrared spectrometry (FTIR), and X-ray diffractometry (XRD). Generally the results indicated that the addition of sodium-montmorillonite (NaMMT) up to 1.5% appears to improve the performance of GLUF resins in particleboards. The results also showed that nanoclays improved mechanical strength (modulus of elasticity (MOE), Modulus of Rupture (MOR), and internal bond (IB) strength) of the panels bonded with GLUF resins. The panels containing GLUF resin and nanoclay yielded lower formaldehyde emission as well as water absorption content than those made from the neat GLUF resins. XRD characterization indicated that NaMMT only intercalated when mixed with GLUF resin. Based on DSC results, the addition of NaMMT could accelerate the curing of GLUF resins. The enthalpy of the cure reaction (ΔH) of GLUF resin containing NaMMT was increased compared with neat GLUF resin. Also the results of FTIR analysis indicated that addition of NaMMT change the GLUF resins structures.     

Medium‐density particleboards from rice husks and soybean protein concentrate

Rice husks are a valuable agricultural residue produced worldwide with potential applications as a wood substitute in particleboard manufacturing. In this work, the feasibility of producing medium‐density particleboards based on waste rice husks bonded with environmentally friendly adhesives from soybean protein concentrate was analyzed. The mechanical properties, internal bond strength, and water resistance of the obtained panels bonded with the homemade soybean protein concentrate adhesives were compared to those of boards glued with commercial adhesives such as phenol–formaldehyde and urea–formaldehyde resins. An alkaline treatment improved the gluing ability of the soybean protein concentrate. The mechanical properties of the alkali‐treated soybean protein concentrate were comparable to those determined for panels with urea–formaldehyde. The lower water resistance of the alkali‐treated soybean protein concentrate particleboards, compared with that of the formaldehyde‐based resins, was counterbalanced by the advantage of being more environmentally sound, which makes them suitable for applications for which the requirements for water resistance are not stringent. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Reduction of formaldehyde emission from plywood

The aim of this work is to evaluate performances of tannin-based resins designed as adhesive in the plywood production. For this purpose, a part of phenol formaldehyde (PF) and melamine formaldehyde (MF) in the classic adhesive formulation was replaced by tannin. The physical properties of the formulated resins (rheological characterization, etc.) were measured. In order to analyze the mechanical performance of tannin-based resins, plywood panels were produced and the mechanical properties including tensile strength wood failure and three-point bending strength were investigated. The performance of these panels is comparable to those of plywood panels made by commercial PF and MF. The results showed that the plywood panels bonded with tannin–PF (PFT) and tannin–MF (MFT) resins exhibited better mechanical properties in comparison to the plywood panels made of commercials PF and MF. The introduction of small properties of tannin in PF and MF resins contribute to the improvement of the water performance of these adhesives. The formaldehyde emission levels obtained from panels bonded with tannin-based resins were lower than those obtained from panels bonded with control PF and MF. Although there are no actual reaction at all between PF, MF, and tannin, addition of tannin significantly improves the water resistance of PF and MF resins. This is a novel finding that manifests the possibility of replacing a convention PF and MF resins by tannin. Modified adhesive is one of the goals in the plywood production without changing any of their production conditions with improvement to their overall properties.     

Properties of liquefied wood modified melamine-formaldehyde (MF) resin adhesive and its application for bonding particleboards

In this study, we modified melamine-formaldehyde (MF) resin adhesive with liquefied wood (LW) and determined the properties of MF–LW adhesive mixtures. Furthermore, we produced particleboards using prepared MF–LW mixtures and evaluated their mechanical and physical properties. Results showed that with increasing content of LW in the adhesive mixture gel time and peak temperature increased while reaction enthalpy decreased. With increasing substitution of MF resin adhesive with LW the thermal stability of adhesive mixture reduced, namely thermal degradation started at lower temperature and weight loss increased. Properties of particleboards improved with increasing amount of LW in the adhesive mixture up to 20% and then deteriorated. Nevertheless, the properties of particleboard with 30% LW in the adhesive mixture were comparable to the properties of particleboard without LW while they worsen at greater portion of LW. Consequently, MF resin adhesive with 30% LW substitution could be used to produce particleboards with suitable mechanical properties and reduced formaldehyde release content.     

Urea formaldehyde resin with low formaldehyde content modified by phenol formaldehyde intermediates and properties of its bamboo particleboards

Phenol formaldehyde reaction solution (PFS) was used to synthesize urea–formaldehyde resins (PFSUF resins) with low formaldehyde content. In addition, the prepared PFSUF resins were used as adhesives to bond bamboo particleboards. Mechanical properties, fracture morphology, water absorption ratio, and dimensional stability of bamboo particleboards have been studied by tensile tests, SEM tests, water absorption analysis, and swelling ratio analysis, respectively. The results demonstrate that the main ingredient of PFS is phenol formaldehyde intermediate 2,4,6‐trimethylolphenate and proper amount of PFS can be used to reduce the formaldehyde content of UF resins effectively. The results also show that bamboo particleboards bonded with PFSUF resins exhibit better mechanical properties, water resistance, and dimensional stability than that bonded with pure UF resin. However, the results of TG and mechanical properties analysis exhibit that alternative curing agents to ammonium chloride should be studied to improve the curing properties of the PFSUF resins with low formaldehyde content. Taken together, this work provides a method of preparing environment‐friendly PFSUF resins with low phenol and low formaldehyde content and the prepared resins have potential application in wood industry. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42280.     

Use of organosolv lignin in phenol–formaldehyde resins for particleboard production: I. Organosolv lignin modified resins

This paper describes the work considering the potential for partially replacing phenol with organosolv lignin in phenol–formaldehyde resin used as an adhesive in the production of particleboard. Lignin-based resins were synthesised with organosolv lignin using various percentages of lignin replacement for phenol. The lignin was introduced to the resin in two different ways. The first method was the replacement of a certain percentage of phenol (5–40%) with lignin (as supplied) directly into resins. In the second method, lignin was modified by phenolation prior to resin manufacture. Different degrees of phenol substitution (20–30%) were investigated for the production of lignin-based resins. The physical properties of the formulated resins were measured and compared to commercial PF resin.     

Polyamine-modified urea-formaldehyde resins. II. Resistance to stress induced by moisture cycling of solid wood joints and particleboard

The objective of this study was to improve the durability and stability of urea-formaldehydebonded wood products by decreasing the internal stress developed during resin cure and by improving the ability of the cured system to withstand cyclic stresses. Urea-formaldehyde resins were modified by (i) incorporating urea-terminated di- and trifunctional flexible amines into the resin structure, (ii) curing the resins with the hydrochloride derivatives of some of these amines (in place of ammonium chloride), or (iii) using both processes. The cyclic stress resistance of solid wood joints and the internal bond strength and thickness swell of particleboards made with these resins were compared with these properties in joints and particleboards made with an unmodified resin and a commercial urea-formaldehyde resin. The strength of joints and the internal bond strength of particleboards made with resins modified with urea-terminated hexamethylenediamine, bishexamethylenetriamine, and poly(propylene oxide) triamine at modifier contents of 13, 16, and 28 wt %, respectively, showed excellent stability even after repeated wet-dry cycles. Similar stress resistance was shown by wood joints and particleboards bonded with the unmodified resin cured with the hydrochloride salts of hexamethylenediamine and triethyleneaminetriamine. In contrast, solid wood joints and particleboards bonded with the unmodified resin cured with ammonium chloride showed lower resistance to cyclic stress. Particleboards that possessed good cyclic stress resistance also showed less thickness swell.     

木材工业用酚醛树脂胶粘剂的快速固化研究

从酚醛树脂胶粘剂的配方改进、胶粘剂合成工艺改进、催化剂添加、胶粘剂调胶及人造板热压工艺改进等几个方面,综述了近几年来木材工业用酚醛树脂胶粘剂快速固化研究。     

Behavior of amine-modified urea–formaldehyde-bonded wood joints at low formaldehyde/urea molar ratios

Urea–formaldehyde-bonded wood products are limited to interior nonstructural applications because of their poor durability under cyclic moisture or humid environments. The stability of solid-wood joints and particleboards can be enhanced by bonding with urea–formaldehyde adhesives modified with di- and trifunctional amines at an effective resin formaldehyde-to-urea mol ratio (F/U) of 1.6; however, particleboard formaldehyde emissions were not improved over those from boards made with unmodified adhesives and were unacceptably high. The relative effectiveness of selected modifications was investigated at resin form aldehyde-to-urea (F/U) molar ratios of 1.4 and 1.2 Solid-wood joints and particleboards made with modified adhesives, an unmodified adhesive, and a phenol formaldehyde (PF) resin were subjected to cyclic soak-dry (cyclic stress) treatments and moist-heat aging. Formaldehyde emissions from particleboards were also determined. At F/U 1.4, the resistance of solid-wood joints made with modified adhesives to cyclic stress and moist-heat aging was equal to that of PF-bonded joints and superior to that of joints bonded with unmodified adhesive. The resistance of particleboards made with modified adhesives was greater than that of boards made with unmodified adhesive but less than that of PF-bonded board. Solid-wood joints and particleboards made with F/U 1.4 resins performed better than did those made with F/U 1.2 resins. Particleboards made with F/U 1.2 resins had formaldehyde emissions well below the standard, and room temperature aging or bonding at high temperature reduced emissions substantially. © 1994 John Wiley & Sons, Inc. 1

1 This article is a US Government work and, as such, is in the public domain in the United States of America.

     

PU/PA纳米粒子改性酚醛树脂胶粘剂的研究

采用自乳化法制备PU/PA纳米粒子,并对酚醛树脂进行增韧改性.考查了丙烯酸酯单体种类、用量以及环氧树脂用量对改性酚醛树脂粘接性能的影响.借助TG、DSC、SEM和TEM对改性酚醛树脂体系的耐热性能、固化反应和微观形态进行了表征.结果表明,PU/PA纳米粒子的加入使酚醛树脂的常温和高温粘接强度显著增加,提高了酚醛树脂的固...     

Incorporation of a nano/micro CuO formulation into phenol formaldehyde (PF) resin: Curing kinetics,morphological analysis,and application

The effects of incorporation of nano-CuO into phenol formaldehyde (PF) resin during sythesis on curing kinetics, nano-CuO structure and bond quality were investigated on orientated strand board (OSB). Apparent activation energy of the PF resins modified with CuO was decreased during the reaction indicating an acceleration of both addition and condensation reactions. X-ray diffraction data indicated that the Cu was in a bivalent state. Morphological analysis confirmed that CuO was uniformly dispersed at both nano and micro scales. Addition of nano-CuO to PF resin was associated with significantly higher internal bond strength on OSB panels. The results suggest that nano-CuO enhances the properties of conventional PF resin to imporve panel properties.     

Jute felt composite from lignin modified phenolic resin

Raw and dewaxed jute felt composites were prepared with resol and lignin modified phenol formaldehyde resin. Four different types of lignin modified resins were used by replacing phenol with lignin. The lignin modified resins were prepared from purified lignin obtained from paper industry waste black liquor. To investigate bonding between jute and resin, IR spectroscopy of jute felts and composites was carried out. The thermal stability of the composites was assessed by DSC and TGA. It was found that the lignin resin jute composite is thermally more stable than resol composite. XRD of jute felt and composite shows that the crystallinity of the jute fiber increases after composite preparation. The lignin resin composites were tested for water absorption and thickness swelling, and it was found that the results are comparable with those of resol jute composite. Composites prepared from lignin phenol formaldehyde resin with 50% phenol replacement has shown 75% tensile strength retention to that of pure resol jute composite.