2. Materials and Methods
2.1. Materials
Sawdust, Glasswares, Thermostat hot plate, Fume cupboard, Magnetic stirrer, Metal and Mould plate, Compression moulding (20 tonnes) machine. Digital pH Meter, Top loading balance, spatula, and thermometer.
400ml of 40% w/v formaldehyde solution (M & B laboratory grade), Urea (200mg M & B, Ammonia (15ml) solution, Ammonium Chloride.
2.2. Methods
2.2.1. Processing of Sawdust
The sawdust was obtained from a sawmill in Samaru, Zaria, Nigeria. It was first dried in the sun for about 72hrs, ground and sieved to obtain uniformed particle size saw dust using a 72m sieve.
2.2.2. Laboratory Synthesis of Urea Formaldehyde Resin
This was done by the condensation reaction of formaldehyde with urea in the ratio of 2.0:1.0. 400ml of 40% aqueous solution of formaldehyde was measured into a clean dried Pyrex 500ml beaker standing on a thermostat hot plate and the solution was stirred vigorously in a fume cupboard for 5minuites. 200g of Urea was gradually added, followed by 15ml of ammonia solution, the mixture was continuously stirred with a magnetic stirrer for one hour at a temperature of 65oC. The solution obtained was then concentrated by heating the solution at a temperature slightly above 65oc for 5hrs to evaporate the water content, pH was maintained at 8. The concentrate was allowed to cool at room temperature to produce a viscous liquid.
2.2.3. Resinification and Formulation Stage
A constant weight of the sawdust was added to the synthesized Urea-Formaldehyde solution and thoroughly mixed using an electric mixer. The impregnated moisture material was then poured into a mould with dimensions (120mm length, 60mm width, and 2mm thickness) containing aluminum foil. The mould was then placed in a compression moulding machine at a pressure of 10 tonnes and temperature of 150°C for 15minutes. The procedure was carried out for 30, 35, 40, and 45ml of urea formaldehyde resin with the constant weight of the filler (sawdust). The particleboard samples produced were allowed to cool at room temperature, and their mechanical properties determined.
NOTE:-CS is the control sample with no filler content and 50% UF Content.
2.2.4. Shore Hardness
Hardness was done according to ASTM D 2240, which is a measure of the resistance of a material to the penetration of a needle under a defined spring force. It is determined as a number from 0 to 100 on the scales A or D. The higher the numbers, the higher the hardness. The letter A is used for flexible types and the letter D for rigid types. Measurements were performed at room temperature. Shore A hardness scale was used and the average of 3 hardness values was taken.
2.2.5. Water Absorption
This was done using the kubrelka apparatus at room temperature. The test was carried out by weighing the specimens (20mm length, 10mm width, and 2mm thickness) before and after soaking in water for 24hrs.
Q=W2-W1/W1×100 (2)
2.2.6. Thickness Swell
The thickness swell test was carried out by measuring the thickness of the specimens before and after 24 hours in water using the Thickness gauge with serial No 82; all were set at room temperature. The ratio of the difference in thickness to the original thickness of the specimens expressed as a percentage is the percentage thickness swell of the sample.
3. Conclusion
The property of the particleboard is a function of the percentage composition of the components. This implies that the properties of the particleboard depend on the resin-filler ratio. Consequently, variation in the percentage composition alters the properties of the particleboard. Particle boards can be produced from sawdust using ureaformaldehyde as a binder Urea-formaldehyde particleboards have less ability to resist water penetration. Hence, UF particleboards have less dimensional stability. As a result, UF particleboards would not have better application in the moist or humid environment. Particle boards produced using more volume of UF are more dimensionally stable as evident in their smaller values of water absorption and thickness swelling compared with the other samples of a small quantity of the UF. The results show that the resin-sawdust ratio significantly influenced the water absorption, thickness swelling, hardness and density UF resin imparted poor mechanical properties to the particleboards. As a result, the PF particleboard is said to exhibit poor resistance to deformation. Therefore, the UF particleboards would be less durable, less tough and have less ability to resist abrasion as reported by. UF particleboards are less expensive to produce as one of the major components (Urea) is readily and cheaply available, as compared to PF Particleboards.