Physical and mechanical properties of fire retardant-treated engkabang (Shorea macrophylla) and Acacia mangium particleboards were assessed. Tests selected for the assessments were water absorption, thickness swelling, modulus of rupture (MOR), modulus of elasticity (MOE) and internal bond (IB). The engkabang and Acacia mangium particles were mixed with 10% w/w of two different fire retardants namely zinc borate (4Zn0.6B2O3.7H2O)-simplified as ZBr and monoammonium phosphate (NH4)H2PO4) during the mixing stage of the particleboard manufacturing processes. The properties of the particleboards were tested using British European 1993 standard. An analysis of variance was carried out to study the effects of fire retardant types on the boards of both species. The study showed that MAP-treated particleboards were superior to ZBr-treated particleboards for both mechanical and physical performances except for modulus of elasticity (MOE). Overall, the fire retardants reduced the physical and mechanical properties of the engkabang and Acacia mangium particleboards. However, all treated and untreated particleboards complied with the standard requirement values and these findings are expected to increase the promotion of both species to be used in producing fire-retardant particleboards.show abstract
Problem statement: Occupying a suitable hot pressing time for particleboard fabrication seems very tricky for manufacturers of the wood-based panel. Longer or shorter pressing times can affect physical and mechanical properties of the produced particleboards and that is why extra care should be given on this matter. Longer pressing time can cause resin in a particleboard to over-cure whereas shorter pressing time can cause insufficient curing of the resin. Determination of hot pressing time is influenced by the type of filler and chemical used. The acidity or alkalinity of a filler and chemical can lengthen or shorten the time taken by the resin to cure. These parameters are usually assessed using buffering capacity test and curing time test. In this study, the two analyses were occupied to assess acidity or alkalinity of kenaf, Shorea macrophylla and Acacia mangium as well as the effect of fire retardants (zinc borate and monoammonium phosphate) to the curing rate of urea formaldehyde resin. Determine acidity or alkalinity of the wood particles through buffering capacity test. The effect of the fire retardants to the curing of Urea Formaldehyde (UF) resin was also studied. Approach: For buffering capacity test, the wood particles were extracted. Then, the extracts were separated into two parts. One part was tested with sodium hydroxide (NaOH) and another part was tested with sulphuric acid (H 2 SO 4 ). Sodium hydroxide was added into the extracts until they reached pH 11. The other part was added with sulphuric acid until they reached pH 3. The pH value was recorded each time 5 ml chemicals added. The acidity of the plants was observed by looking at the volume of sulphuric acid needed to reduce their pH to 3, whereas alkalinity was evaluated by looking at the volume of sodium hydroxide used to increase their pH to 11. Curing times of UF resin added or not added with fire retardants were calculated in second (sec). Results: Buffering capacity study revealed that kenaf, Shorea macrophylla and Acacia mangium behaved similarly in alkali and acidic conditions. All the materials had less resistance towards acid than towards alkali. Kenaf had the greatest resistance towards alkali compared with the other two species. As an important processing parameter in particleboard fabrication, the curing time of the adhesive mixture with added fire retardants was studied in comparison with a control mixture (without fire retardant with a curing time of 140 sec). Those two fire retardants showed different effect on the curing time of the mixture. Zinc borate was found to delay the curing time by more than 100% compared with control mixture whereas, monoammonium phosphate increased the curing time by almost 60%. The curing time for control mixture (without fire retardant) was 140 sec. Conclusion: Based on the testing results, some potential modifications to improve the curing time were discussed to avoid short curing time to improve the manufacturability of the material systems.
A research was conducted to discover the screw withdrawal resistance of moulded laminated veneer lumbers made from oil palm trunks (MLVOP). The MLVOPs were manufactured separately with three different veneer arrangements namely S100% (each ply came from the superior part), SS-CI (surface superior and core inferior) and S-I (alternate superior and inferior parts). The veneers were divided into two groups. One group of veneers was bonded with urea formaldehyde (UF) resin to MLVOPs and the other was bonded with phenol formaldehyde (PF). The veneers were pressed at a temperature of 110ºC for 20 min. The pressures applied to press the veneers to MLVOPs were 1500 psi, 2000 psi and 2500 psi. The study showed that the pressures and S-I veneer arrangement gave significant effects to the screw withdrawal resistance of UF-bonded and PF-bonded MLVOPs. MLVOPs with S-I veneer arrangement achieved the highest mean screw withdrawal resistance values when they were bonded with UF resin then pressed with 1500 psi and 2500 psi and bonded with PF resin and pressed with 1500 psi. The values were 848 N, 884 N and 496 N respectively. Overall, UF-bonded MLVOPs were better than those bonded with PF resin.
This research was undertaken to study the suitability of oil palm trunk to be utilized as a raw material for moulded laminated veneer oil palm (MLVOP). The trunks were converted into veneers by rotary peeling machine. The veneers were segregated into two veneer qualities namely superior (S) and inferior (I). The methods of segregating veneers quality were defined. The superior veneers were obtained by peeling the billets until their diameters left approximately 12 inches, meanwhile the inferior veneers were obtained by further peeling the same billets used for obtaining superior veneers until their diameters left 4 inches. The mean densities for superior veneer as well as inferior veneer were about 478.8 kg/m 3 and 385.1 kg/m 3 respectively. The mean moisture content of both superior and inferior veneers was approximately 11%. The veneers were arranged with 5 layers into three types of moulded shapes of furniture components namely i) 100% S ii) alternate S and I and iii) surface S & core I. The suitable pressure, temperature and time were set as important parameters. The arrangements of veneer quality were pressed using V-shape mould through hot press machine with three parameters pressure 1500 psi, 2000 psi and 2500 psi. Two types of adhesives namely UF and PF were used to produce MLVOP. The mechanical properties of the composites were tested with three bending types i.e. flat bending, type-V bending, and type-OV in accordance with BS EN 310:1993. The results showed that most of the samples bonded with UF-resin have better strengths (MOR and MOE) when tested with the three bending tests compared to the samples bonded with PF-resin. However, the results vary depends on the veneer arrangements.
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