A Note on the Effect of Microwave Heating on Iodine-Catalyzed Acetylation of Wood

The effect of microwave heating on the iodine-catalyzed acetylation of rubberwood with acetic anhydride has been investigated. Microwave radiation was used as the heating source for modifying specimens saturated with acetic anhydride in bulk solution (excess of reagent) and impregnated specimens (limited supply of anhydride). Extent of modification of wood was expressed in terms of weight percent gain (WPG) and modification was characterized using FTIR spectroscopy. In bulk solution, microwave radiations were primarily absorbed by anhydride solutions for heating purposes and a moderate WPG was obtained. However, when microwave heating was used to modify impregnated wood specimens under no excess of anhydride, a significant enhancement in degree of modification was achieved within a few minutes. The modified wood exhibited good anti-swelling efficiency.     

Effects of superheated steam treatment on moisture adsorption and mechanical properties of pre-dried rubberwood

Abstract

Rubberwood (Hevea brasiliensis) was treated with superheated steam (140–160?°C) for 1–3?h and then its adsorption ability, mechanical properties, and color changes were investigated. The results of adsorption show decreased equilibrium moisture content (EMC) for all heat-treated cases throughout the hygroscopic range. The Hailwood–Horrobin model was used to analyze the sorption isotherms and determine the monolayer and polylayer moisture contents for untreated and heat-treated rubberwood. The monolayer moisture content clearly decreased with treatment temperature and duration, whereas the reduction in polylayer moisture was relatively smaller. Moreover, the least density of water adsorption sites was found in wood after treatment at 160?°C for 3?h, indicating this as the cause for reduced equilibrium adsorption. All treatment conditions had improved mechanical properties, including compression parallel-to-grain, hardness, and tensile strength. The total color difference of the wood surface increased with increasing temperature and treatment duration.     

Effect of Heat Treatment on Color Changes,Dimensional Stability,and Mechanical Properties of Wood

Abstract

Properties of fast-growing timbers with low durability can be improved by thermal modification. Thermal modification is an eco-friendly method of improving durability of wood. In this work, specimens of rubberwood (Hevea brasiliensis) and silver oak (Grevillea robusta) were thermally modified in vacuum between 210 to 240°C for 1 to 8 hours, and their weight loss, color, and chemical changes evaluated. Rate of thermal degradation was determined from weight loss data. The color of the modified wood darkened and was uniform throughout. CIE lightness color coordinate (L*) decreased with treatment severity, while chroma coordinates a* and b* increased initially, but later decreased with increased process severity. FTIR analysis showed degradation of cell wall polymers resulting in generation of structures which are responsible for color darkening of thermally modified wood. Mechanical properties (bending strength, MOR, and bending stiffness, MOE) of heat-treated wood decreased. A decrease in hydroxyl groups reduced the hygroscopic nature, resulting in increased dimensional stability of thermally modified wood.     

Preparation of steam activated carbon from rubberwood sawdust (Hevea brasiliensis) and its adsorption kinetics

Activated carbon was produced from a biowaste product, rubberwood sawdust (RWSD) using steam in a high temperature fluidized bed reactor. Experiments were carried out to investigate the influence of various process parameters such as activation time, activation temperature, particle size and fluidising velocity on the quality of the activated carbon. The activated carbon was characterized based on its iodine number, methylene blue number, Brauner Emmet Teller (BET) surface area and surface area obtained using the ethylene glycol mono ethyl ether (EGME) retention method. The best quality activated carbon was obtained at an activation time and temperature of 1h and 750 degrees C for an average particle size of 0.46 mm. The adsorption kinetics shows that pseudo-second-order rate fitted the adsorption kinetics better than pseudo-first-order rate equation. The adsorption capacity of carbon produced from RWSD was found to be 1250 mg g(-1) for the Bismark Brown dye. The rate constant and diffusion coefficient for intraparticle transport were determined for steam activated carbon. The characteristic of the prepared activated carbon was found comparable to the commercial activated carbon.     

Rubberwood–high-density polyethylene composites: Effect of filler size and coupling agents on mechanical properties

Composites were made from rubberwood in the form of fibers (RWF) and powder (RWP) and high-density polyethylene (HDPE). The RWP–HDPE composites showed higher tensile strength than those of the fibers. The inferior properties of the RWF-filled composites were believed to be attributed to the agglomeration of the fibers. Two types of coupling agents, that is, 3-(trimethoxysilyl)propyl methacrylate (TPM) and 3-aminopropyltriethoxysilane (APE), were employed in an attempt to improve the mechanical properties of the composites. The former was able to significantly improve the modulus of elasticity (MOE) and impact strength of the RWF-filled composites. Treatment with TPM resulted in the reduction of the tensile modulus and increase in the elongation at break (EB) for both RWF and RWP-filled composites. APE produced RWP-filled composites with a higher tensile strength and modulus. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1993–2004, 1998     

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.     

提高热带硬木干燥产率的高温干燥系统

目前，商业化干燥高温干燥（HTD^TM）橡木和，或其他本土硬木未见报道。至目前为止，95％以上马来西亚木材干燥工厂采用传统低温蒸汽加热干燥系统。由马来西亚林业科学研究所（FRIM）开发的HTDTM系统，特别对于橡胶木家具行业提供了一个独特解决方案。这种技术无需采用标准贝塞尔化学处理，只需一级干燥操作即将生橡木锯材转化为可供下游制造加工过程使用的干木材。木材处理周期时间比现有过程减少75％以上。此外，经HTDTM处理过的木材质量好，与传统方法生产的木材相比，具有更好的外形稳定性。与行业伙伴合作，FRIM高温干燥橡木产品已经成功地用于试生产胶合板台面和其他的实木家具及组件。     

Rubberwood–polymer composites based on glycidyl methacrylate and diallyl phthalate

Wood–polymer composites (WPC) of rubberwood (Hevea Brasiliensis) were prepared by impregnating the wood with glycidyl methacrylate (GMA), combinations of glycidyl methacrylate and diallyl phthalate (GMA–DAP), or diallyl phthalate (DAP) alone. Polymerization was carried out by catalyst-heat treatment. The results showed that WPC based on GMA exhibited greater dimensional stability (results of antishrink efficiency after six days of soaking) about five times than those based on DAP alone. Flexural [Modulus of Elasticity (MOE), Modulus of Rupture (MOR), and toughnes], compressive, and impact properties for all the samples tested are improved, especially for those with higher chemical loading. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1221–1226, 1998     

Optimized conditions for the grafting reaction of poly(methyl acrylate) onto rubberwood fiber

Graft copolymerization of poly(methyl acrylate) (PMA) onto rubberwood fiber (RWF) was carried out by free radical initiation. Hydrogen peroxide and ferrous ions were used as an initiator system. Effects of various parameters (reaction temperature and reaction time, as well as hydrogen peroxide, ferrous ammonium sulfate and monomer concentrations) on the grafting percentage were investigated. A high percentage of grafting was achieved when optimum reaction conditions were used. The optimum temperature of the reaction was determined to be about 55 °C and the reaction time was 120 min. The optimum concentration of H₂O₂ was 0.03 M and the amounts of Fe²⁺ and MA were 0.4 mmol and 0.05 mol, respectively. The PMA homopolymer was removed from the graft copolymer by Soxhlet extraction using acetone. The presence of PMA on the fiber was confirmed by FT-IR spectroscopy and gravimetry. The surface morphology of the poly(methyl acrylate)-graft-(rubberwood fiber) was studied by means of scanning electron microscopy. Copyright © 2004 Society of Chemical Industry     

An approach for indirect monitoring of moisture content in rubberwood (Hevea brasiliensis) during hot air drying

Abstract

This study aimed to determine the equilibrium moisture content and to develop an indirect measurement technique for the moisture content (MC) by observing temperature and vapor pressure during hot air drying. The temperature and gas pressure were recorded during hot air drying at several points within wood sample specimens conforming to ASTM D 143 and AOAC, 1990. The moisture content was estimated from measured temperature and pressure. The accuracy of MC estimates was validated by oven-drying method. For validation, nine experiments at different temperatures of hot air drying were run and the indirect measurement was found to provide a good accuracy. The obtained statistics were R² = 82.5%, standard error (SE) ranging from 0.15 to 0.43, root mean square error (RMSE) ranging from 0.16 to 0.38 and mean absolute error (MAE) ranging from 0.4 to 1.1 respectively. It can be concluded that the air in wood was removed completely, especially when the MC was below the fiber saturation point. We have demonstrated an alternative moisture content monitoring method for potential adoption by the rubberwood industries.