Plywood Adhesives Research Articles

Characterization Of Plywoods Produced By Various Bio-Adhesives

The increasing environmental concern and adverse health effects with the use of formaldehyde-based plywood adhesives has led to an interest in developing adhesives based on renewable resources. The main objective of this study was to explore and develop environmental friendly bio-based adhesives suitable for manufacturing plywood. Three different adhesives were prepared, one using soya meal powder and the other two using tamarind kernel powder as the major constituents. In the soya meal adhesive (SMA), water, pine oil and fresh hydrated lime were used for the preparation of the adhesive. Different methods were adopted in preparing the two tamarind adhesives, Tamarind Adhesive 1 (TA1) in which water, formalin and glucose were used and Tamarind Adhesive 2 (TA2) in which hot water and boric acid were used. These three adhesives were characterized in detail using Field Emission Scanning Electron Microscopy (FESEM) and X-Ray Diffraction (XRD). The FESEM images reveal the presence of dispersed particles in all the adhesives but the matrix of these adhesives varies. SMA shows a continuous matrix structure while the TA1 reveal agglomerated matrix structure and TA2 show more of continuous matrix with few agglomerated portions. The XRD analysis reveals the amorphous nature of all the three bio-adhesives. The XRD pattern of TA1 is similar to that of urea formaldehyde with a peak at around 20°, an indication of the presence of formalin, while the absence of such a peak in the other two adhesives is a clear indication of absence of dangerous formaldehyde. It can be concluded that the presence of dispersed particles in a continuous matrix and the absence of formaldehyde in SMA makes it superior in its properties. In spite of the presence of dispersed particles, the agglomerated matrix structure in TA1 might show inferior properties but the presence of formalin makes it similar in nature to that of urea formaldehyde. The combination of agglomeration and more of continuous matrix structure with dispersed particles and absence of formaldehyde in TA2 might make it similar in properties with SMA.

Assessing the tensile shear strength and interfacial bonding mechanism of poplar plywood with high-density polyethylene films as adhesive

A series of high-density polyethylene (HDPE) films were tested as adhesives for plywood and were fabricated using hot pressing followed by cold pressing. The effects of the moisture content, HDPE dosage, and the hot-press temperature and pressure on the mechanical properties were evaluated by analyzing the tensile shear strength. The results indicated that the HDPE films that were used as adhesives in plywood had good bonding strength, meeting the requirements for type II-grade plywood according to the GB/T 9846.3 standard (2004, Beijing, China). The bonding mechanism was also investigated using the width of the bond line, the average penetration (AP), and the effective penetration (EP) through the use of optical microscopy and scanning electron microscopy (SEM). The results showed that the HDPE is able to penetrate into the vessels, xylem, and so on. On the whole, both the AP and EP increased with an increase in the HDPE dosage and hot-press temperature and pressure, but not with an increase in the moisture content. In addition, the effects of the factors mentioned above on the width of the bond line, AP, and EP were also investigated by an ANOVA analysis.

Enhancing the Adhesive Strength of a Plywood Adhesive Developed from Hydrolyzed Specified Risk Materials.

The current production of wood composites relies mostly on formaldehyde-based adhesives such as urea formaldehyde (UF) and phenol formaldehyde (PF) resins. As these resins are produced from non-renewable resources, and there are some ongoing issues with possible health hazard due to formaldehyde emission from such products, the purpose of this research was to develop a formaldehyde-free plywood adhesive utilizing waste protein as a renewable feedstock. The feedstock for this work was specified risk material (SRM), which is currently being disposed of either by incineration or by landfilling. In this report, we describe a technology for utilization of SRM for the development of an environmentally friendly plywood adhesive. SRM was thermally hydrolyzed using a Canadian government-approved protocol, and the peptides were recovered from the hydrolyzate. The recovered peptides were chemically crosslinked with polyamidoamine-epichlorohydrin (PAE) resin to develop an adhesive system for bonding of plywood specimens. The effects of crosslinking time, peptides/crosslinking agent ratio, and temperature of hot pressing of plywood specimens on the strength of formulated adhesives were investigated. Formulations containing as much as 78% (wt/wt) peptides met the ASTM (American Society for Testing and Materials) specifications of minimum dry and soaked shear strength requirement for UF resin type adhesives. Under the optimum conditions tested, the peptides–PAE resin-based formulations resulted in plywood specimens having comparable dry as well as soaked shear strength to that of commercial PF resin.

PEREKAT KAYU LAPIS DARI DAUN LAMTORO (Leucaena Leucocephala)

Adhesives ( adesive ) is a very important material in the plywood industry, the amount of adhesives commonly used in the industry is an adhesive containing chemicals Urea formaldehyde . Urea Formaldehyde is a chemical compound which, when exposed to heat slightly will cause emissions which produce toxic gases that can pollute the air and cause health problems , can cause respiratory irritation and may even cause cancer .As a substitute for urea formaldehyde can be used natural materials containing tannin , tannin is widely available in a variety of plants , tannin present in the stems , bark , leaves and roots of plants. Manufacture of plywood adhesive of the leaf lamtoro besides environmentally friendly , can also increase the economic value of the leaves lamtoro .The process of making plywood adhesive of the leaf lamtoro by means of extraction with water at a temperature of 70 ° C for 2-5 hours , the adhesive quality test results are as follows : pH 6.8 ; Viscosity (thickness ) 1973.72 cps , density 1.0761 g / ml ; Test appearance ( color adhesive greenish brown , the smell is not overpowering ; does not appear any other materials that affect the adhesive ; content of 21.77 % solids ; gelatinasi time 39 minutes ; strong bonding strength ; the shelf life of one month. The cost of production of plywood adhesives of leaves lamtoro Rp.20.788.322 - with a production capacity of 1100 kg , in order to obtain the production cost of Rp.18 898,- /kg sticking plywood of leaves lamtoro . Keywords: Adhesives, Leaf lamtoro, manufacturing process, quality, cost of production.

Effects of bark extraction before liquefaction and liquid oil fractionation after liquefaction on bark-based phenol formaldehyde resoles

Liquid product from white birch bark liquefaction in water/ethanol (50:50, v/v) mixture was successfully applied in substituting 50wt% of phenol in the synthesis of bark based phenol formaldehyde (BPF) resole (i.e., 50% HTL-oil BPF resole). Besides, eHTL-oil from liquefaction of the bark extracted in 70vol% aqueous acetone, and fHTL-oil obtained after HTL-oil fractionation in water, were also used to substitute 50% of phenol for BPF resoles synthesis. The results showed that all the three BPF resoles contained more free formaldehyde than the neat PF resole, and bark extraction before liquefaction and HTL-oil fractionation after liquefaction led to higher free formaldehyde contents in the resulted 50% eHTL-oil BPF resole and 50% fHTL-oil BPF resole. Furthermore, bark extraction before liquefaction retarded the curing of the resulted 50% eHTL-oil BPF resole, while HTL-oil fractionation after liquefaction slightly promoted the curing of the resulted 50% eHTL-oil BPF resole. All the three BPF resoles displayed less thermal stability than the neat PF resole, but the effects of bark extraction before liquefaction and HTL-oil fractionation after liquefaction on the thermal stability of the resulted BPF resoles were negligible. All the three BPF resoles could meet the bond strength requirements as adhesives for plywood in accordance to the JIS standard. Bark extraction before liquefaction led to less water resistance for the resulted 50% eHTL-oil BPF resole, while HTL-oil fractionation after liquefaction improved the water resistance of the resulted 50% fHTL-oil BPF resole.

Investigating the use of peanut meal: a potential new resource for wood adhesives

This study was conducted to evaluate the potential of peanut meal (PM) to produce plywood adhesivesviasodium dodecyl sulfate (SDS) and ethylene glycol diglycidyl ether (EGDE) modification.

Properties of Lignin from Oil Palm Empty Fruit Bunch and Its Application for Plywood Adhesive

Properties of Lignin from Oil Palm Empty Fruit Bunch and Its Application for Plywood Adhesive

Properties of Lignin from Oil Palm Empty Fruit Bunch and Its Application for Plywood Adhesive

Lignin from lignocellulosic biomass is a potential biopolymer for wood adhesive. The aims of this study were to characterize lignin isolated from the black liquor of oil palm empty fruit bunch fiber pretreated with steam explosion in alkaline conditions and to examine the bond quality of aqueous polymer isocyanate (API) adhesive prepared from lignin, natural rubber latex (NRL), and polyvinyl a lcohol (PVA) as base polymers with isocyanate crosslinkers. Lignin was precipitated from the black liquor by adding hy drochloric acid; then the precipitate was separated by filtration, thoroughly washed with water up to pH 2 and pH 5, and dried. The isolated lignin was characterized by ultimate analysis, UV spectroscopy, FT-IR spectroscopy, and thermal analysis. Three-layer plywood samples were prepared, and the bond strengths of the plywood samples were dete rmined in dry conditions and after cyclic boiling. The lignin isolates with different pH values did not have sign ificantly different chemical and thermal properties . Both lignin isolates had similar C, H, and O contents, identica l functional groups in the FTIR spectra, similar ab sorption in the UV spectra, and high decomposition temperatures. The b ase polymers composition that could produce API adhesive for exterior applications was NRL/PVA/lignin (4/4/2). T he use of more lignin in the adhesive formulation d ecreased the bond strength of the plywood.

Influence of Ammonium Pentaborate (APB) on the Performance of Urea Formaldehyde (UF) Adhesives for Plywood

Ammonium pentaborate (APB) was used to modify urea formaldehyde (UF) resins, in which the formaldehyde to urea molar ratio was set at 1.80, 1.50, 1.25, and 1.05. Some specific properties, including gel time, free formaldehyde content in UF, bond strength, and formaldehyde emission levels from plywood were evaluated. The result showed that APB increased the gel time length, but also decreased free formaldehyde content and emission levels, which was reduced mostly by 79.0% and 81.4%, respectively. The result of bond strength indicated that APB was proper to modify high F/U molar ratio of UF resin regardless of the loading level, but a recommended loading level should be considered to relevantly lower the F/U molar ratio of UF. The suggested loading level of APB to UF is 8.0% to 6.0%, 6.0%, and 4.0% to UF resin with F/U molar ratio of 1.8, 1.5, and 1.25 separately.

Characterization and Application of Urea-Formaldehyde-Furfural Co-condensed Resins as Wood Adhesives

Furfural, as an organic compound derived from biomass materials, was used to partially substitute for formaldehyde in the synthesis of UF resin. Urea-formaldehyde-furfural co-condensed (UFFR) resins with different substitute ratios of furfural to formaldehyde (FR/F) were prepared. The effects of the FR/F substitute ratio on the performances of UFFR resins were investigated. Matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS) and Fourier transform infrared spectroscopy (FT-IR) were applied to characterize the chemical structures of UFFR resins. Plywood bonded by these resins was manufactured, and its bond strength and formaldehyde emission were measured. The results showed that the substitution of furfural in place of formaldehyde could reduce the free formaldehyde content effectively at the expense of prolongation of the curing time. The spectra of MALDI-TOF and FTIR confirmed the co-condensation of urea-formaldehyde-furfural both in uncured and cured resins. Plywood prepared under optimized parameters could yield high bond strength and low formaldehyde emission, which were 0.84 MPa and 0.23 ppm, respectively. The optimized parameters were as follows: a FR/F substitute ratio of 1/3; 1% (NH4)2S2O8 as the curing agent; and a hot pressing temperature of 130 °C. Hence, it is feasible to substitute partially formaldehyde by furfural to prepare UFFR resins as wood adhesives for plywood.

Cross-linked soy-based wood adhesives for plywood

To improve the water resistance of soy-based adhesive for wood panels, three kinds of cross-linkers, namely, epoxy resin (EPR), melamine–formaldehyde (MF) and their mixture EPR+MF were used in this paper. The results indicated that all the three cross-linkers improved the water resistance of soy-based adhesive and the hybrid cross-linker EPR+MF, was the best. With press temperature 160°C and press time 8min, type II and even type I plywood could be prepared when 6.4%EPR+6.4%MF is used as cross-linker of soy-based adhesive. FT-IR indicated that the great improvement of water resistance of soy-based adhesive modified with EPR and MF might be caused by the reaction between epoxy and –OH, and that between MF and –NH.

Reduction of Formaldehyde Emission from Plywood Adhesive Filling a Ground Scallop Shell

Reduction of Formaldehyde Emission from Plywood Adhesive Filling a Ground Scallop Shell

Evaluation of corn germ protein as an extender in plywood adhesive

This study was conducted to evaluate the potential of wet-milled corn germ protein as an extender in plywood adhesive. Partially defatted dried corn germ from wet-milling, containing 2.1% (dry basis, db) crude oil and 24.7% (db) crude protein, was ground to 40-mesh particle size to produce the meal. The predominant water- and saline-soluble proteins were extracted from the corn germ meal (CGM) by using 0.1 M NaCl as solvent in a method that used homogenization, centrifugation, dialysis, and freeze-drying. The recovered freeze-dried protein extract (FDPE) was substituted (on protein content basis) for wheat flour in the standard adhesive mix for sprayline coaters. Adhesive containing CGM was also prepared in the same manner. Mixing and adhesion properties of the corn germ-based adhesives were compared with those of the industry standard adhesive. The adhesive containing FDPE showed dispersibility and mixing behaviors, as well as viscosity values that were almost identical to those of the industry standard and superior to those of CGM adhesive. The mean wet tensile strength of the adhesive containing FDPE was notably greater (1.71 MPa) than that of CGM-based adhesive (1.34 MPa) and wheat-based standard adhesive (1.38 MPa), which indicated stronger bonding. The results demonstrated that corn germ protein has the potential to be an alternative protein extender in plywood adhesives for sprayline coaters.

Substitution of phenol in phenol-formaldehyde (PF) resins by wood tar for plywood adhesives

Abstract Wood tars from Acacia confusa Merr. and Cryptomeria japonica D. Don. were produced by reduced pressure distillation at 76 mm Hg and 50°C from the bottom layer of crude wood vinegars that had set for over 6 months. The feasibility of using water-soluble, resole-type, wood tar phenol-formaldehyde resins (WT-PF) was investigated. The resins were prepared from phenol (P) and wood tars (WTs) at weight ratios of 100:0, 80:20, 60:40 and 40:60 and F/P molar ratios of 1.5, 1.8 and 2.0 as plywood adhesives. The results demonstrated that WT-PF resins had a higher viscosity, shorter gel times, a higher polydispersity, a lower curing temperature and less heat of curing than conventional PF resins under the same conditions. The shear strength of plywood bonded with WT-PF resins was slightly lower than that of conventional PF resin. However, the WT-PF resin still met the CNS 1349 requirement for the dry test, and phenol substitution levels could be up to 60%, but only 20% for type I and type II plywood. The addition of A. confusa bark powder fillers could significantly improve the bonding strength of WT-PF resins, especially for the warm water soaking and soaking in boiling water tests. The required amounts of fillers added were up to 5% for A. confusa WT-PF resins and up to 3% for C. japonica resins.

Synthesis of biobased phenolic resins/adhesives with methylolated wood‐derived bio‐oil

AbstractBio‐oil from the hydrothermal liquefaction of Eastern White Pine (Pinus strobus L.) sawdust was methylolated with formaldehyde in the presence of sodium hydroxide. The obtained methylolated bio‐oil (MB) was used to synthesize methylolated bio‐oil–phenol formaldehyde (MBPF) resol resins with a phenol substitution ratio of up to 75 wt %. All of the resins were used as wood adhesives for the production of a three‐layered plywood. The MBPF resol resins were comprehensively characterized for their physical, chemical, thermal, and mechanical properties (e.g., viscosity, nonvolatile content, shelf life, free formaldehyde level, molecular weight and distribution, curing temperature, bonding strength) when used as plywood adhesives. All of the MBPF resins contained similar nonvolatile contents as the reference pure phenol formaldehyde (PF) resin but had higher viscosities and shorter shelf lives, depending on the amount of MB in the MBPF. All of the MBPF resins displayed a lower curing temperature than the reference PF resin, with the main curing peak around 140°C, which was similar to that of the pure PF resin. According to thermogravimetric analysis, the methylolation treatment of bio‐oil improved the thermal stability of the MBPF resins compared to the bio‐oil–PF resol resins, which used untreated bio‐oil. The dry/wet bonding strengths of the plywood specimens glued with the MBPF resol resins with up to 60 wt % phenol substitution exceeded or were comparable to those of the conventional PF resol resin. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Water‐resistant plywood adhesives prepared from phenolated larch bark in the presence of various combination catalysts

AbstractThe properties of larch barks phenolated with various combinations of acidic catalysts and the properties of adhesives synthesized with these phenolated barks have been investigated. The results have indicated that the catalyst species used has great effects on bark phenolation and many properties of the resultant bark adhesives (BA). High‐performance liquid chromatography (HPLC) and Gel permeation chromatography (GPC) analyses have indicated that the amount of phenol bound to the bark and recondensation of phenolated components decreased with decreasing acidity of the combination catalysts used, resulting in decreases in the extent of phenolation, bound phenol content, and molecular weight but an increase in the number of active sites on the phenolated bark. Larch bark phenolated with combined catalysts can be used to prepare water‐resistant wood adhesives with low formaldehyde emission. By judiciously decreasing the acidity of the catalyst used for bark phenolation, the properties of BA, such as storage life, bond strength, and formaldehyde emission, could be effectively improved. BA‐C showed the acceptable wet bond strength and a sufficiently low formaldehyde emission, making it a good potential candidate for commercial applications. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Influence of uron resins on the performance of UF resins as adhesives for plywood

Uron resin, a kind of urea-formaldehyde (UF) resin containing much more uron structure, were prepared. Several modied UF resins were obtained from mixing uron resins with normal UF resins as well as synthesizing UF resin with uron resin as raw material. � is work demonstrated that the introducing of the uron structure reduced free formaldehyde content of UF resin and formaldehyde emission levels in bonded plywood panels signicantly, the former were reduced by 76% and 84% in the latter. � e synthesis time of uron resin can be shortened to 8 hours. � e test result of free formaldehyde content, formaldehyde emission levels and bond strength indicated that specimen of 20 parts uron resin synthesized in 8 hours mixed with 100 parts UF resins (F/U molar ratio of 1.3) had a potential advantage to industrial application. � e benecial eect of uron resin on the performance of UF resin can be attributed to the opening of uron cycle structure and the following reaction with free formaldehyde and its oligomeric glycol forms.

Whey protein-based water-resistant and environmentally safe adhesives for plywood

Whey protein is a renewable and environmentally safe biomaterial, a by-product of cheese production. It can be utilized for non-food applications for value-added products. The substances glyoxal (GO), glutaraldehyde (GA), polymeric methylene biphenyl diisocyanate (p-MDI), urea-formaldehyde (UF) resin, and phenol-formaldehyde oligomer (PFO) that contain reactive groups were applied together with whey protein as modifier in order to increase crosslinking density and molecular weight for improving the bond strength and water resistance of whey protein. A water-resistant and environmentally safe whey protein-based wood adhesive for plywood was developed by evaluating the effects of these modifiers on the bond strength, bond durability, and free formaldehyde emission of the resulting plywood panels. Results of FTIR and SEM analyses and bond evaluation indicated that GO, GA, and p-MDI were not suitable to modify whey proteins due to their high reactivity with whey proteins, causing phase separation. UF resin was not a good modifier for whey proteins because of either its poor water-resistance or higher emission of hazardous formaldehyde. Whey protein adhesives modified with PFO had a dry shear bond strength of 1.98 MPa and a 28h-boiling-dry-boiling wet shear strength of 1.73 MPa, which were both much higher than the required values for structural use according to standard JIS K6806-2003, while its formaldehyde emission was 0.067mg/L, much lower than the required value for green plywood according to standard JIS A5908.

Evaluation of sorghum flour as extender in plywood adhesives for sprayline coaters or foam extrusion

This study was conducted to evaluate sorghum flour as protein extender in phenol–formaldehyde-based plywood adhesive for sprayline coaters or foam extrusion. Defatted sorghum flour, containing 0.2% (db) residual oil and 12.0% (db) crude protein, was analyzed for solubility and foaming properties. Sorghum flour proteins were least soluble (≤12%) under acidic pH, most soluble (72%) at pH 10, and produced substantial and highly stable foam at pH 10. Sorghum flour was substituted (on protein content basis) for wheat flour in the standard glue mix. Mixing properties and bond strength of the sorghum-based glue were compared with those of the industry standard glue. The sorghum flour-based adhesive had mixing properties and appearance that were superior to those of the standard wheat flour-based plywood glue, but its viscosity and bond strength were markedly less. Doubling the amount of protein contributed by sorghum flour in the glue mix markedly improved both viscosity (1104 cP) and adhesion strength (1.37 MPa) of the sorghum-based plywood glue to acceptable levels. The modified sorghum flour-based plywood glue also produced foam that remained stable up to 3 h. These results demonstrated that sorghum flour is a viable extender in plywood glues for sprayline coater or foam extrusion.

Evaluation of Forestry Residue-Source Oil-Tea Cake as an Extender for Phenol-Formaldehyde Plywood Adhesive

Forestry residue-source oil-tea cake (consisting of plant protein, tannin, carbohydrate compounds, and tea saponin) is a major by-product from the pressing process of Camellia (Camellia oleifera Abel) seeds. In this study, we evaluated oil-tea cake as a potential extender to replace the current industry extender, wheat flour, for applications with phenol-formaldehyde (PF) plywood adhesives. We evaluated mixing properties, curing characteristics, and adhesion performance of the adhesive containing oil-tea cake as compared with those of the standard wheat flour–based adhesive. The oil-tea cake–based adhesive showed excellent mixing properties and working life, and its viscosity met the recommended value for the sprayline coater. The adhesive containing oil-tea cake was comparable in wet shear strength and wood failure values of plywood to the wheat flour–based adhesive. Thermal analysis showed that adhesives containing oil-tea cake had significant curing reactions because of the relatively large curing enthalpy (DH) value of oil-tea cake. These results indicate that oil-tea cake is suitable as a low-cost and effective plywood adhesive extender. Therefore, using oil-tea cake is economically beneficial because it not only makes use of what would otherwise be forestry residue, but it is cheaper to use as a plywood adhesive than wheat flour.