Browsing by Author "Ogola, Wilson Otieno"

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    Production and characterisation of coffee husks particleboards.
    (University of Dar es Salaam, 2002) Ogola, Wilson Otieno
    Tanzania has an economy based on agriculture. The agricultural activities produce wastes that are normally burnt while preparing the farms for the next season, consequently causing environmental pollution. Very little of these wastes are economically found useful due to lack of technological knowhow. Research developments have revealed that agricultural wastes could be used to make useful engineering materials for roofing, panelling, sheathing and furniture. Also, naturally occurring binders, abundantly available in Tanzania, could be used in the binding of the materials instead of the synthetic binders that are non-available and expensive. In this research, particleboards have been processed from coffee husks, a by-product from coffee processing with a naturally occurring hydrolyzed tannin adhesive and some of the existing synthetic adhesives such as urea formaldehyde, phenol formaldehyde as binders. A blend of coffee husks and wood particles with the above resins were also processed. The processing techniques used in industry were simulated in the laboratory to produce the boards. The resulting boards were characterized by determining their physical and mechanical properties by using ASTM Standards D1037-93 part A and DIN 53456 standards. A comparison of their properties were made with the data of the wood art 2-1989 for grade Cl type (general purpose) article boards and from CAN 3-01883-M82 Grade Y-Canadian Standards for Exterior particleboards. Results indicate that coffee husks particle sizes were between 850 mm to 2 mm in diameter and the moisture content was between 9 to 13 %. The optimum physical and mechanical properties were obtained with 12-14% of hydrolyzed tannin resin content, 7-8% of urea formaldehyde and 10% phenol formaldehyde resin content, based on the dry weight of the coffee husks. Coffee husks particleboards had the following optimum physical properties: For coffee husks/hydrolyzed tannin particleboards of density1035 kg/m3, thickness swelling after one hour was 6% which compared well with the BS standards 5669 part 2, of 8.4%. It had water absorption of 8.4% for the same period. The water absorption and thickness swelling for coffee husks/urea formaldehyde particleboard of density 1033 kg/m3 were 24% and 20% respectively. The specific heat capacity was 1260, 1508, 1670, 1651 Jkg-1 ÂșC-1 for coffee husks/urea formaldehyde, coffee husks/phenol formaldehyde, coffee husks/tannin, wood/tannin particleboards at room temperature respectively. Coffee husks particleboards had the following optimum mechanical properties: For coffee husks/tannin particleboards of density 1035 kg/m3, the modulus of elasticity (MOE) was 1216 MPa, the modulus of rupture (MOR) was 6 MPa, the tensile strength parallel to the surface was 2 MPa, the impact strength was 11.3 kJ/m, a shear strength parallel to the surface of 0.51 MPa, work done on impact of 1.1 J, screw withdrawal forces of 2300 N (face), and 638 N(edge), nail withdrawal forces of 497 N(face)and 282 N (edge), compression strength parallel to the surface of 6 MPa and a nail head pull through of 1787 N. The corresponding coffee husks/urea formaldehyde particleboard had MOE and MOR of 1089 MPa and 5 MPa respectively. The impact streght was 3.4 kJ/m2, a tensile streght parallel to the surface of 0.7 MPa, work done of 3J, and nail head pull through of 387 N. The results indicated that, it was possible to produce particleboards using these locally available materials for general applications. This would help in reducing the current pressure on wood and also help in reducing deforestation and conservation of the rainforests as well as wild life survival. A blend of coffee husks with wood particles improved the mechanical properties and lowered the mphysical properties of coffee husks particleboards. The resulting particle boards, had physical and mechanical properties which compared well with those of particleboards made from other agricultural wastes such as maize cobs, maize husks and rice husks. However, the properties were lower than those from BS Standards 5669 part 2 type C1 (general purpose) and CAN 3-01883M82-Grade Y-Canadian Standards for Exterior particleboard. This was due to the limited particle sizes of the coffee husks that could not allow for much improvement in the physical and mechanical properties as well as their smooth waxy surfaces that could not allow for good interfacial adhesion.