Ali Shalbafan

Physiomechanical properties of ultra-lightweight foam core particleboard: different core densities

Abstract Ultra-lightweight foam core particleboards have been produced in a novel one-step process with resinated wood particles for the faces and expandable polystyrene (EPS) as core layer material. The mechanical and physical properties of panels were investigated in terms of the different foam core densities and press parameters (temperature, pressing and foaming time). The bending strength properties of the panels were not significantly changed with increasing foam core density from 80 to 120 kg m-3. Panels produced at a press temperature of 130°C (1-EPS) have an improved core-face interface and also a denser surface layer, which positively influences the internal bond and thickness swelling. The panels produced at a press temperature of 160°C (2-EPS) have smaller and more foam cells and an improved fusion of foam beads and properties, which have a positive influence on the edge screw withdrawal resistance and water absorption.

Internal decay assessment in standing beech trees using ultrasonic velocity measurement

Ultrasonic wave timing inspection was used to detect the internal decay in standing Iranian beech trees (Fagus orientalis). To evaluate the influence of internal decay on ultrasonic velocity, healthy round sections of freshly cut fallen beech trees were selected. Holes [as heart or internal decay indicator and with different shapes (circular and slot) and locations] were manually created and progressively enlarged in the wood section disks, and ultrasonic wave velocity was measured by using a commercial ultrasonic tester (Sylvatest Duo). The results showed that ultrasonic wave velocity linearly and significantly decreased by increasing hole dimensions, and location of holes had no influence on the extent and trend of velocity decrease. Although slots covered a small volume fraction of disks, they had a greater effect on ultrasonic velocities reduction as compared with circular holes.

Effect of aluminosilicate powders on the applicability of innovative geopolymer binders for wood-based composites

In this research, a new binder class for wood based composites, named geopolymer binder, was developed based on pozzolanic by-products (e.g. fly ash). Additionally, effects of different amounts of silica fume, as a replacement agent with other aluminosilicate components (e.g. fly ash and metakaolin), have been evaluated in the innovative binder. The Automated Bonding Evaluation System technique was used to characterize the bonding shear strength of the developed geopolymer binder. It was shown that the best shear strength for fly ash based binders was obtained by the lowest press temperature and longest pressing time. The addition of silica fume (from 20% up to 100%) significantly influenced the bonding shear strength in all binder types. Due to the chemical and mineralogical compositions, silica fume displays higher pozzolanic activity than metakaolin whereas fly ash shows lower strength in comparison to metakaolin. The silica fume (100%) based binder has also superior shear strength compared to those of conventional UF resin and other geopolymer binders. Bonding shear strength like that for UF resin was achieved by substituting only 20% silica fume in geopolymer binder compositions.

Geopolymers as potential new binder class for the wood based composite industry

Abstract Geopolymer binders are an emerging class of mineral polymer that can be manufactured from natural raw materials and industrial byproducts containing high amounts of silica (Si) and alumina (Al) in mineral compositions. Various ratios of materials used for manufacturing geopolymer binder have been tested to evaluate the bonding performance of geopolymers with wood by means of tests performed on an automated bonding evaluation system (ABES). Tests with a binder based on sodium silicate water glass (Na 50T) are partly promising, which resulted only 10% lower shear strength than that based on urea formaldehyde. The binder characteristics were significantly influenced by changing the ratio of SiO2:M2O (M=Na or K) and the ratio solid content to chemical base in the water glass. Expectedly, increasing press temperatures and pressing times showed a positive correlation with the curing performance of geopolymer binder. It was also demonstrated that the binder properties can be changed in wide ranges to obtain binders which fulfill the minimum requirements set by industrial users.

Reduction of formaldehyde emission from medium density fiberboard by chitosan as scavenger

ABSTRACT Chitosan was used as environmentally friendly and bio-based scavenger for reducing the formaldehyde emission from medium density fiberboard. Using of chitosan powder showed better capacity of formaldehyde adsorption rather than the chitosan solution. Liquid 13C-NMR showed that the free formaldehyde in urea formaldehyde adhesive having chitosan powder was drastically reduced. Additionally, the observed peak at 155 ppm showed that that the chitosan powder was copolymerized with urea formaldehyde adhesive. Increasing the amount of chitosan powder was significantly reduced the emitted formaldehyde. It was shown that the formaldehyde adsorption of chitosan was strongly influenced by the pH value of adhesive composition. The pH value and the adhesive gel time tended to increase with addition of chitosan powder, due to the proton affinity of chitosan. The mechanical and physical properties of panels did not significantly change when the chitosan content as scavenger was raised up to 3%, while a formaldehyde emission class of wood level was achieved. It is supposed that the emission of formaldehyde might well increase again while the reactive sites of the chitosan added were already saturated with formaldehyde. Hence, performing of long-term formaldehyde emission is recommended for further analysis based on the obtained results in this study.

Ultra-light particleboard: characterization of foam core layer by digital image correlation

Increasing markets for internet-traded furniture, but also economic concerns are main driving forces to considerably reduce the weight of wood-based furniture panels. Recent research and technological developments have led to an innovative one-step process which simplifies the typical multi-step process for production of foam core panels. Three layered sandwich panels (with particleboard faces and polymeric in situ expanded foam as core layer) can be produced by a one-step process without additional gluing between the face and core layers. As the morphology of the foam and hence its mechanical properties strongly depend on its chemical composition, as well as on the process parameters during expansion, there are no data available, so far, describing the foam of the novel panels. The aim of the proposed project is to determine the elastic properties of in situ expanded foams using 2D digital image correlation. The data can be used later on for the simulation of the elastic behavior of foam core particleboards by means of FEM to describe the short and long term behavior of the panels.