Jin Heon Kwon

Electromagnetic interference shielding effectiveness, electrical resistivity and mechanical performance of carbonized medium density fiberboard

The effect of carbonization temperature on the electromagnetic interference shielding effectiveness, electrical resistivity, and mechanical performance of medium density fiberboards carbonized in a vacuum furnace under a gas flow of nitrogen (200 mL/min) between 400℃ and 1500℃ was investigated. The medium density fiberboards specimens carbonized below 700℃ showed stable and low electromagnetic interference values (1.3–7.6 dB) between 10 MHz and 1 GHz frequency. The electromagnetic interference (average 43.1 dB) of the MDF specimens carbonized at 800℃ were suitable for industrial applications. However, the MDF specimens carbonized above 900–1500℃ showed high electromagnetic interference values (66.8–84.6 dB). When the carbonization temperature increased from 600℃ to 700℃, the electrical resistivity of the specimens greatly decreased (180.9 × 103 to 137.5 Ω-cm). A further increment in the carbonization temperature (1200℃) had a small effect on the electrical resistivity (5.8 Ω-cm) of the specimens and no effect between 1300℃ (0.5 Ω-cm) and 1500℃ (0.5 Ω-cm). The carbonized specimens showed lower modulus of rupture and internal bond strength values than the untreated specimens but the differences between the strength values of the untreated specimens and the carbonized specimens decreased with increasing carbonization temperature. The modulus of elasticities of the specimens carbonized above 800℃ were higher than the untreated specimens.

Effect of Wood-derived Charcoal Content on Properties of Wood Plastic Composites

The effect of wood‑derived charcoal flour on the water resistance and mechanical properties of wood plastic composite (WPC) panels was investigated. The hot press molded WPC panels were produced from polypropylene (37 wt%) with maleic anhydride-grafted polypropylene (MAPP, 3 wt%) and different mixtures of wood flour and charcoal flour. The amount of charcoal flour was gradually increased up to 60 wt%. The thickness swelling and water absorption of WPC panels considerably decreased with increasing charcoal flour content. The internal bond strength and bending properties of the WPC panels significantly improved with increasing charcoal flour content. This was mainly attributed to the high amount of pores and gaps in the charcoal flour. Melted polypropylene could get into the pores and gaps during the hot press molding, which lead to a better interfacial adhesion between polymer matrix and wood filler. The results showed that the charcoal flour could be partially substituted for the wood flour in the production of WPC panels having higher dimensional stability and internal bond strength.

Combined effect of thermoplastic and thermosetting adhesives on properties of particleboard with rice husk core

1. The main components of rice husk are cellulose (25 to 35%), hemicellulose (18 to 21%), lignin (26 to 31%), silica (15 to 17%), solubles (2 to 5%), and moisture content of 5-10% 2 . The reasons behind the use of rice husk in particleboard industry are its high availability, low bulk density (90-150 kg/m 3 ), toughness, abrasive in nature, resistance to weathering and unique composition 3 . Although previous studies reported that rice husk particleboard could be used in the manufcture of furniture and interior fitments, the physical and mechanical properties of the particeboards were lower than those of the particleboards made from wood particles

Improving dimensional stability of injection molded wood plastic composites using cold and hot water extraction methods

Dimensional stability of wood plastic composites (WPCs) made from polypropylene and pine wood flour with and without coupling agent was investigated. The pine wood flour was prepared from wood chips which had been immersed, respectively, in boiling water for 1 h, 3 h, and 5 h or in distilled water for 1 day, 3 days, and 5 days at room temperature. It was found that thickness swelling (TS) and water absorption (WA) of the WPCs made using extracted wood were lower than those of WPCs produced with unextracted wood. The TS and WA values of WPCs decreased with extraction duration both for cold and hot water extraction. The effect of hot water extraction on the TS and WA properties of the WPCs was more pronounced than cold water extraction.

Improving Bending and Tensile Properties of Lignocellulosic Filled Polypropylene Composite Panels Using Aramid Fabric

The bending and tensile properties of polypropylene (PP) composites panels prepared from wood flour (50 wt%) or rice husk flour (50 wt%), PP (47 wt%) with coupling agent (maleic anhydride-grafted PP, 3 wt%), and aramid fabric were investigated. Three types of composite panels were produced using the aramid fabrics which were placed in single face layer, in core layer, or in two surface layers of the composite panels. The composite panels were manufactured using a dry blend/hot press (compression molding) method. The tensile and bending properties of the composite panels were greatly improved by the incorporation of aramid fabric. The composite panels having aramid fabrics positioned in two layers close to top and bottom layers had the highest bending and tensile properties, followed by one layer and core layer reinforcements, respectively. The tensile strength and modulus of wood flour-PP composites with the aramid fabric placed in the top and bottom layers were found to be 57.0 MPa and 5120 MPa while they were found to be 28.2 MPa and 3785 MPa for the wood flour-PP composites with the core layer of aramid fabric, respectively. The tensile strength and modulus of wood flour-PP composites without aramid fabric were found to be 12.5 MPa and 2540 MPa, respectively. Similar trends were observed for the rice husk flour-PP composite panels.