Evaluation of properties of starch-based adhesives and particleboard manufactured from them

The objective of this study was to evaluate some of the mechanical and physical properties of experimental particleboard panels manufactured from rubberwood (Hevea brasiliensis) bonded using oil palm starch, wheat starch, and urea formaldehyde (UF) at a density of 0.60 g/cm³. Bending characteristics, internal bond strength, thickness swelling, and water absorptions of the samples were determined based on Japanese Industrial Standard (JIS). Overall mechanical properties for natural binder oil palm starch resulted in higher values than those made from wheat starch. The highest internal-bonding strength (IB) value of 0.41 N/mm² was determined for the samples made from oil palm starch. Dimensional stability in the form of thickness swelling of the samples made from oil palm starch had higher values, ranging from 4.24 to 22.84% than those manufactured from wheat starch. Natural adhesive showed comparable strength with panels manufactured with UF. Overall results meet the Japanese Industrial Standard (JIS) requirements except for water absorption and thickness swelling of the samples.     

Preparation and Evaluation of Particleboard with a Soy Flour-Polyethylenimine-Maleic Anhydride Adhesive

A soy-based formaldehyde-free adhesive consisting of soy flour (SF), polyethylenimine (PEI), maleic anhydride (MA) and NaOH was investigated for making three-layer particleboard. The weight ratio of SF/PEI/MA/NaOH was 7/1.0/0.32/0.1. Hot-press temperature, hot-press time, particleboard density and adhesive usage were optimized in terms of enhancing the modulus of rupture (MOR), modulus of elasticity (MOE) and internal bond strength (IB) of the resulting particleboard. The MOR, MOE and IB met the minimum industrial requirements of M-2 particleboard under the following variables: hot-press temperature of 170 °C, hot-press time of 270 s, the adhesive usage of surface particles at 10 wt%, the adhesive usage of the core particles at 8 wt%, and the targeted particleboard density of 0.80 g/cm³.     

Low formaldehyde emission particleboard panels realized through a new acrylic binder

The effectiveness of acrylic resins as low formaldehyde emission binders for particleboard production was explored. In particular, a multifunctional methacrylic monomer, ethoxylated bisphenol A dimethacrylate, classified as nonskin and eyes irritant, was selected and tested. In comparison panels realized with classic urea‐formaldehyde (UF) binder were also prepared. No significant differences were found through the morpholocigal analysis of samples prepared with the two different binders. Moreover, particleboard panels realized with the acrylic binder showed better mechanical properties and lower water absorption and thickness swelling in comparison with corresponding panels realized with the UF binders. Furthermore, the replacement of the UF with the acrylic binder did not affect thermal insulation properties of the panels. Formaldehyde release tests revealed that particleboard panels obtained by applying the acrylic binder can be classified as E1 following the European classification and even F**** following the stricter Japanese classification. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

A Formaldehyde-Free Soy-Based Adhesive for Making Oriented Strandboard

A formaldehyde-free adhesive consisting of soy flour, polyethylenimine, maleic anhydride, and sodium hydroxide was investigated for making randomly oriented strandboard (R-OSB) and oriented strandboard (OSB). The hot-press conditions and the adhesive usage rate were optimized in terms of enhancing internal bond strength (IB), modulus of rupture (MOR), and modulus of elasticity (MOE) of the resulting R-OSB and OSB. The IB, MOR, and MOE were the highest at a hot-press temperature of 170°C, a hot-press time of 4–5 min, and an adhesive usage rate of 7%. The strengths of the OSB panels made with this formaldehyde-free adhesive were compared with those of commercial OSB panels purchased at a local Home Depot store.     

Tensile Strength of Monolayer Particleboards Produced from Date Palm Midrib Chips Bonded with Urea Formaldehyde

Systematic laboratory-scale experiments were carried out to study the technical feasibility of producing monolayer particleboards using midribs of Saudi Arabian date palm tree branches (Phoenix dactylifera-L) as raw material. Chips produced from midrib and impregnated with a predetermined proportion of urea formaldyhde binder were hot-pressed under constant pressure (3.25 N/mm²), temperature (180°C) and press cycle times of 5, 7, and 9 min. Experimental particleboard specimens subjected to mechanical tests exhibited satisfactory tensile strength levels. Strength was enhanced phenomenally by improving the particle quality and optimizing experimental variables. Electron microscopy and EDX data on the internal structure of the midribs are also reported.     

Influence of Process Variables on the Bending Strength of Particleboard Produced from Arabian Date Palm Mid-Rib Chips

Feed produced from Arabian date palm (Phoenix dectylifera-L) biomass and impregnated with urea formaldehyde (UF) adhesive binder is subjected to hot compaction to yield particleboard panels of excellent bending strength. Process variables such as press temperature, press cycle time, compaction pressure and particle thickness are shown to exercise significant effects on the bending strength of the final product. The influence of chipping technique on particle integrity and surface quality is highlighted. Scanning electron microscopic (SEM) evidence is presented to illustrate microstructural damages caused by excessively high compaction pressure.     

Technical soda lignin dissolved in urea as an environmental friendly binder in wood fiberboard

The application of lignin as binder in wood composite panel is not only environmentally friendly but also commercially attractive. The dissolving of technical soda lignin is the most premier challenge in its application. In this study, the effect of different key factors on soda lignin solubility in urea was investigated. The maximum solubility of 60.16?g/L was obtained under the temperature 70?°C, urea concentration 8?M, lignin content 7%, and pH 8.8. Then, different kinds of wood fiber material were mixed with the dissolved lignin solution to make fiber board separately. The results showed that the lignin can enhance the tensile strength of particleboard and can be used as a binder in wood material, but the strength will be different with different materials. The optimal tensile strength obtained was 44.63?MPa with the sample made from oriented cotton linter sheet.     

Modeling and optimization of formaldehyde‐free wood composites using a Box‐Behnken design

A response surface model using a Box‐Behnken design was constructed to statistically model and optimize the material compositions‐processing conditions‐mechanical property relationships of formaldehyde‐free wood composite panels. Three levels of binding agent content, pressing time, and press temperature were studied and regression models were developed to describe and optimize the statistical effects of the formulation and processing conditions on the mechanical properties of the panels. Linear models best fit both the flexural strength (modulus of rupture [MOR]) and internal bond (IB) strength of the panels. Increasing any of the manufacturing variables resulted in greater MOR and IB strength. Flexural stiffness (modulus of elasticity [MOE]) was best described by a quadratic regression model. Increased MOE could be obtained through higher pressing times, binding agent concentrations, and/or pressing temperatures. However, binding agent concentration had less effect on increasing the MOE at higher pressing temperatures. Numerical optimization showed that formaldehyde‐free panels with desired mechanical properties could be manufactured at pressing temperatures ranging from 187.18 to199.97°C, pressing time from 3.31 to 8.83 minutes, and binding agent concentration from 7.66 to 11.86%. POLYM. COMPOS., 27:497–503, 2006. © 2006 Society of Plastics Engineers     

Effects of Adhesive Application Methods on Performance of a Soy-based Adhesive in Oriented Strandboard

A wet method and dry method of applying a soy flour (SF)–curing agent (CA) adhesive onto wood flakes were evaluated for making randomly oriented strandboard (R-OSB) and OSB. The wet method involved the thorough mixing of SF and CA prior to spraying the SF–CA mixture onto wood flakes. SF:CA weight ratio, adhesive add-on rate, hot-press conditions were optimized for enhancing internal bond strength (IB), modulus of rupture (MOR), and modulus of elasticity(MOE) of the resulting R-OSB. The highest IB, MOR and MOE were obtained at the 1:1 SF:CA weight ratio. IB, MOR and MOE of R-OSB exceeded the minimum industrial requirements at a ≥7% adhesive add-on rate, a hot-press temperature in the 170–220 °C range, and a ≥4 min hot-press time. The dry method involved spraying aqueous CA solution onto a mixture of SF and wood flakes. The dry method allowed the strengths of the resulting R-OSB to exceed the minimum industrial requirements at a higher SF:CA ratio (up to 7:1). The dry method was superior to the wet method because a higher SF:CA ratio meant a lower adhesive cost. OSBs made with the SF–CA adhesive had strengths higher than or comparable to commercial OSBs.     

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.     

1,3-Dimethylol-4,5-dihydroxyethyleneurea as a Potential Alternative Binder for Plywood

Two types of commercial 1,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU) resins were used for the first time as the binders in 3-ply plywood manufacturing. The studies were aimed at the assessment of the applicability of DMDHEU as substitute for widely used urea–formaldehyde (UF) resins. Applied press platen temperature was 120°C, 140°C, and 160°C and pressing time was 300 s. The results indicate that the DMDHEU can be used as a binder for plywood. The mechanical properties: tensile shear strength, modulus of rupture (MOR), and modulus of elasticity (MOE) were determined – i.e., > 1.0, 75–90, and 11100–18000 MPa, respectively. It was found that platen temperature 120°C was sufficient for the proper cure of the binder and to obtain dry shear strength that met the requirements of EN 310 standard. Formaldehyde release was 2.8 ± 0.6 mg?m^–2?h^–1 which complied with standards for interior grade plywood.     

Modified wheat gluten as a binder in particleboard made from reed

To evaluate the utilization of reed in environmental friendly high‐density particleboard, modified wheat gluten was used with urea‐formaldehyde as a binder in different ratios, applying the optimum conditions obtained on using UF resin alone. The scanning electron microscopy of the reed fibers showed that the fibers are cylindrical in shape, which helps in enhancing the adhesion between the binder and the inner and outer surfaces of the fibers. The dependence of the mechanical properties (modulus of rupture, modulus of elasticity and the internal bond) and the physical properties (water absorption and thickness swelling) on the urea‐formaldehyde/modified gluten ratios was studied. Addition of 1% and 2% boric acid as a fungicide to the binder mixture resulted in no significant change in the mechanical properties and slight improvement in the physical properties of the produced particleboard. Thermogravimetric analyses of selected samples were done to study the thermal stability of the particleboard bonded with the modified binder with and without boric acid. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Performance evaluation of a natural based adhesive derived from Irvingia wood species kernel extracts on wood panel production

Abstract

Irvingia seed kernels have been identified as potential raw materials for a wide range of applications such as biodiesel, cosmetics, perfume, and soap. As a result, the Irvingia wood species is earmarked for domestication globally in order to commercially exploit these potential benefits. This study investigated the physical and mechanical properties of experimental panels made with pine (Pinus elliottii) wood particles, using modified Irvingia gabonensis (IG) and Irvingia wombolu (IW) extracts as a binder. The mean values of modulus of rupture (MOR) and modulus of elasticity (MOE) for the panels produced with this Irvingia-based adhesive were 5.8 and 1251?MPa, respectively. These values are within the minimum requirement for MOR and MOE (5.5 and 1034?MPa, respectively) for panel grade 1-L-1 as specified by the American National Standards Institute A208.1. The results from the study show that Irvingia kernel extracts may be considered as a potential environmentally friendly adhesive for wood composite manufacture.     

Curing of low level melamine‐modified urea‐formaldehyde particleboard binder resins studied with dynamic mechanical analysis (DMA)

Effects of resin formulation, catalyst, and curing temperature were studied for particleboard binder‐type urea‐formaldehyde (UF) and 6 ～ 12% melamine‐modified urea‐melamine‐formaldehyde (UMF) resins using the dynamic mechanical analysis method at 125 ～ 160°C. In general, the UF and UMF resins gelled and, after a relatively long low modulus period, rapidly vitrified. The gel times shortened as the catalyst level and resin mix time increased. The cure slope of the vitrification stage decreased as the catalyst mix time increased, perhaps because of the deleterious effects of polymer advancements incurred before curing. For UMF resins, the higher extent of polymerization effected for UF base resin in resin synthesis increased the cure slope of vitrification. The cure times taken to reach the vitrification were longer for UMF resins than UF resins and increased with increased melamine levels. The thermal stability and rigidity of cured UMF resins were higher than those of UF resins and also higher for resins with higher melamine levels, to indicate the possibility of bonding particleboard with improved bond strength and lower formaldehyde emission. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 377–389, 2005     

The Response of Hardwood Flakes and Flakeboard to High Temperature Drying

This study assesses the effect of high temperature drying on chemical and mechanical properties of flakes and correlates changes in flake quality with board properties. The high temperature drying of flakes was found to have a significant effect on the internal bond (IB) of the resulting panels. The highest IB values were observed in boards produced from flakes dried at 150°C. Boards produced from flakes dried at 20°C and 350°C exhibited consistently lower values for IB. Opposite trends were noted for total acid content of flake. Multiple regression and correlation analysis revealed a strong relationship between IB, total acid content, and dryer temperature. A significant species effect was also present. Increased levels of flake total acids. acid buffering capacity, and the ratio of acid to base buffering capacities resulted in decreased board property values. Flake bending tests indicated that, in general, the strength and stiffness of the flakes were adversely affected by high temperature drying. This effect did not manifest itself, however, in the resulting panels. Possible reasons for this phenomenon are discussed.     

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.     

Novel composite sandwich structure from green materials: Mechanical,physical, and biological evaluation

Flax and Jute fabrics were used as reinforcements with polyester resin to form composite skins while poplar particleboard was used as a core for making composite sandwich structures by applying vacuum assisted resin transfer molding (VARTM) technique. Mechanical, physical, and biological properties of these novel composite sandwich structures were evaluated. The results showed that the proposed engineered panels have superior mechanical properties that are suitable for different structural applications compared with conventional particleboards. When compared with the control panels, significant enhancement on Modulus of elasticity (MOE) and Modulus of rupture (MOR) were achieved. On the other hand, the results indicated that the proposed panel composites exhibit better dimensional stability compared with poplar particleboard control panels. In addition, the proposed composite sandwich structures proved resistant against the decay fungi after 12 weeks of fungal exposure. Obviously, the developed composite panels could be used in a wide variety of applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42253.     

Low addition of melamine salts for improved melamine‐urea‐formaldehyde adhesive water resistance

The addition of melamine acetate salts to an adhesive glue mix can allow the use of melamine–urea–formaldehyde (MUF) resins of lower melamine contents (rather than just urea–formaldehyde resins) and lower total amounts of melamine. Performances can be obtained that are characteristic of the top‐of‐the‐line, generally higher melamine content MUF adhesive resins for the preparation of wood particleboard panels. Improvements in the panel internal‐bond strength of greater than 30% can be obtained by the addition of melamine acetate salts to top‐of‐the‐line MUF resins. The approach to the concept of increased melamine solubility with a melamine salt is compatible with the approach of increasing melamine solubility with solvents such as acetals (e.g., methylal). However, the synergy advantage of using the two approaches jointly is not very marked. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 287–292, 2003     

Influence of processing conditions and material compositions on the performance of formaldehyde‐free wood‐based composites

This study examined the differences between formaldehyde‐free wood composite panels made with maleated polyethylene (MAPE) and maleated polypropylene (MAPP) binding agents. Specifically, the study investigated the contrasts of (a) base resin type, PE vs. PP, (b) molecular weight/maleic anhydride content in MAPP binding agents, and (c) the manufacturing methods (reactive extrusion vs. hot press) on the physicomechanical properties of the composites. FTIR and XPS analyses of unmodified and modified wood particles after reactive extrusion with maleated polyolefins provided evidence of chemical bonding between the hydroxyl groups of wood particles and maleated polyolefins. Although extruding the particles before panel pressing gave better internal bond (IB) strength, superior bending properties were obtained through compression molding alone. MAPP‐based panels outperformed MAPE‐based panels in stiffness. Conversely, MAPE increased the IB strength of the panels compared with MAPP. Polymer base resin had no effect on modulus of rupture or screw holding capacity. Differences between the two maleated polypropylene compounds were not significant for any of the mechanical properties tested. Formaldehyde‐free wood composites manufactured in this study often outperformed standard requirements for conventional particleboard, regardless of material composition or manufacturing method used. POLYM. COMPOS., 27:599–607, 2006. © 2006 Society of Plastics Engineers     

Ionic liquid modified lignin-phenol-glyoxal resin: a green alternative resin for production of particleboards

The aim of this research was to evaluate the properties of particleboard panels bonded with ionic liquid treated lignin- phenol- glyoxal (LPG) resin. For this purpose, soda bagasse lignin was modified by 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]) ionic liquid and then various contents of virgin and modified lignin (20, 30 and 40 wt% based on weight of phenol), phenol and glyoxal were used for synthesis of LPG resins. After resin synthesis, thermal and physicochemical properties of the synthesized resins such as curing behavior, gelation time, viscosity, solid content and density were measured. Finally, the resins so prepared were used for laboratory particleboard manufacturing. The panels physical (water absorption, thickness swelling) as well as mechanical (MOE, MOR and internal bond strength) properties were measured according to standard methods. The resins tests indicated that modification of lignin with ionic liquid not only can accelerate the gelation time and increase viscosity, density and solid content of LPG resins but also decrease the temperature required for curing the LPG resins. Based on the results of this work, the mechanical strength and dimensional stability of the particleboards bonded with a LPG resin can be improved by using modified lignin. The particleboards prepared with the LPG resin, using either modified or virgin lignin, presented higher water absorption as well as weaker mechanical strength than those prepared with the control PF resin. However, there does not appear to be any statistically significant difference between the some properties of the panels bonded with the control PF resin and those bonded with the LPG resin containing modified lignin.