Search

The polystyrene film as a formaldehyde-free adhesive for plywood production was developed from polystyrene foam waste (PSF) and D-limonene, extracted from orange peel waste. The influence of the weight ratio of solvent (D-limonene) to foam in the range of 1, 1.5 and 2 (w/w) on the properties of adhesive film and plywood panels was studied. In addition, the effects of pressing temperatures of 150°C, 165°C and 180°C on the properties of the plywood were investigated. The adhesive film was characterized by measuring the melt flow index, the average molecular weight of the polymers and by FTIR. The bonding quality of the adhesive films was investigated by shear strength tests. Integrated gel permeation chromatography has also shown that the average molecular weight of PSF is drastically reduced by doubling the solvent content. Shear strength and bending properties were also significantly reduced by doubling the weight ratio of solvent to foam. The mechanical properties of plywood are positively affected with increasing press temperature to 165°C. In general, plywood bonded with an adhesive film prepared with a solvent to foam weight ratio of 1 and press temperature of 165°C was fulfilled the requirement according to EN314-2 for interior use. [ABSTRACT FROM AUTHOR]

In simulation of wood mechanical behaviors, it is imperative to define elastic engineering parameters of the wood (three Young's moduli, three shear moduli and six Poisson's ratios). As regards, the determination of a set of nine independent elastic constants of wood by the experimental method is expensive and laborious and requires several specimens and test equipment and the literature is very rare and has a wide range in data. In this study, elastic engineering parameters of poplar wood (Populus deltoides) were determined by applying the ultrasonic waves and their first-ever application as input data in simulation of mechanical behavior of the poplar wood. Ultrasonic velocity measurements give a chance for the direct determination of the all orthotropic elastic constants using only little small stresses to the wood material. The commercial finite element program ABAQUSTM software package was used to model and analyze as linear orthotropic elastic materials. For validating the applicability and better and more accurate evaluation of engineering parameters were determined by ultrasonic wave propagation in simulation, both three-point bending and uniaxial tensile tests were examined. The ultrasonic technique for determination of elastic engineering parameters of poplar wood, as input data in the finite element method, leads to a very close correlation with the experiment results, which turns out that these data are reliable and applicable for the simulation of wood behaviors. [ABSTRACT FROM AUTHOR]

In this study, the MDF sanding dust was examined as a precursor for synthesizing activated carbon (AC). For this purpose, MDF sanding dust was impregnated with KOH at two different weight ratios 1:0.50 and 1:1 (sanding dust/KOH). The process was done in one step at a temperature of 750 °C and a heating rate of 8 °C/min. The synthesized ACs at different content were added into urea-formaldehyde (UF) resin for medium density fiberboard (MDF) production. The laboratory MDF boards were produced using a hot press at a temperature of 190 °C and pressure of 40 MPa. The ACs content in UF resin was set at 0.25%, 0.50% and 1% based on the dry weight of the resin. The ACs were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The BET equation was used to determine the specific surface area of the AC samples. Water absorption, thickness swelling, internal bonding, flexural modulus and strength, and the formaldehyde emission from MDF boards were determined. The curing behavior of UF resins were evaluated using Differential Scanning Calorimetry (DSC). The results revealed that surface area and micropore volume of ACs increase with increasing KOH ratio; and the ACs exhibited three-dimensional porous network structures. The DSC results also showed that the ACs significantly increase the reaction enthalpy of UF resins. The addition of AC as an additive to UF resin significantly reduces formaldehyde release from MDF boards and improves their physical and mechanical properties. [ABSTRACT FROM AUTHOR]

The main purpose of this work was to study the formaldehyde emission from wood plastic composites (WPCs) containing polyvinyl chloride (PVC), wood flour, and sanding dust of medium density fiberboard (MDF). Wood floor was replaced with 10, 15, and 20% MDF sanding dust (as a wood‐based panel waste), and the composites were manufactured by the extrusion method. Formaldehyde emission from WPCs was measured using two different methods: the desiccator method according to ISO 12460 and the flask method according to EN717‐3. Moreover, the physical and mechanical properties of the WPC samples were determined. The results indicated that the use of MDF sanding dust in formulation of WPCs leads to higher formaldehyde emission. The composites with higher content of MDF sanding dust exhibited higher formaldehyde emission. Although the PVC composites containing MDF sanding dust release formaldehyde, the formaldehyde emission values were very low. Therefore, these composites can be considered to be green composites and there is no concern in their indoor applications. J. VINYL ADDIT. TECHNOL., 25:159–164, 2019. © 2018 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Combined hygro-thermo-mechanical technique was adopted and used for densification of poplar wood instead of sole treatment. This technique is combination of two techniques of hygrothermal treatment and densification of wood. For treatment, poplar wood blocks were initially treated hygrothermally at temperatures of 130, 150 and 170°C for holding time of 20, 40 minutes. Afterwards, the densification process was carried out under a hot press (temperature 160°C for 20 minutes). For densification compression set was adjusted for 40 and 60 % based on the initial thickness (radial direction) of the blocks. The densified and non-densified wood blocks were tested for physical and mechanical properties as density, water absorption, thickness swelling, springback, bending strength, modulus of elasticity as well as shear strength parallel to grain. Results revealed that wood properties were enhanced due to the combined hygro-thermo-mechanical -treatment. According to the results, wood density was increased due to the combined hygro-thermo-mechanical -treatment significantly. The treatment improved the dimensional stability of the densified samples. It was also found that the combined hygro-thermo-mechanical -treatment could significantly improve mechanical properties and also reduce the springback in the densified poplar wood. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM PUBLISHER]

In this article, effects of nano-clay particles and compatibilization effect of the molten phase oxidized polypropylene were studied on the composites produced by wood fibers, polypropylene polymer, and nano-clay particles. To produce samples, wood fibers, and polypropylene polymer were mixed in an extruder in presence of 0, 2, and 4% nano-clay particles and 3% oxidized polypropylene (OPP), and then these samples were hot pressed in specific dimensions. Then the mechanical and physical properties, such as flexural strength, tensile strength, impact strength, and water absorption values were evaluated according to the ASTM Standards. The results showed that increment in amount of nano-clay particles and also, the usage of oxidized polypropylene, improved mechanical and physical properties of the composites. However, the impact strength and water absorption values were reduced. Also, X-ray diffraction analysis and electron microscopes images showed that the distribution of nano-clay particles in the matrix of polymer has intercalation structure. [ABSTRACT FROM PUBLISHER]

The purpose of the current research was to investigate water/moisture absorption and associated thickness swelling and their rates in hybrid wood flour/E-glass fiber/propylene composite immersed in water, exposed to steam, and the influence of application of the glass fiber as well as maleic-anhydride-polypropylene (MAPP 2%) as coupling agent on those properties. The sample strips with 10mm thickness and 70mm width were made by using a laboratory twin-screw extruder. The specimens were immersed in water and exposed to steam for 4320 min to determine the water/moisture absorption and the thickness swelling as well as their rates in the composites. Results revealed that application of the glass fibers increased in the water/moisture absorption significantly in the hybrid composites due to formed micro-gaps in interfaces between wood flour and the glass fibers. However, application of the coupling agent (MAPP 2%) significantly reduced the micro-gaps and diminished the water/moisture absorption as well as the related thickness swelling in the hybrid composites. [ABSTRACT FROM AUTHOR]

The effects of filler loading and immersion in water on the creep/recovery behavior of composites made from MDF (medium density fiberboard) flour (as natural fiber) and recycled HDPE (high density polyethylene) (as resin) were studied (at 60, 70, and 80% by weight fiber loadings). Nominal density and dimensions of the manufactured panels were 1 g/cm3 and 35 × 35 × 1 cm3, respectively. Maximum values of flexural modulus and strength of panels were obtained at 70 and 60% fiber content, respectively. The creep strain decreased as the lignocellulosic flour level increased. Water absorption has negative effect on creep behavior of MDF flour/HDPE composites. For all filler contents, it can be seen that the creep strain increases when the immersion time increases. This is believed to occur as a result of the cumulative effect of absorbed water on fiber matrix debonding and easier relaxation of the molecules at higher moisture contents leading to larger deformations at longer times. [ABSTRACT FROM AUTHOR]