Browsing by Author "Asimeng, Bernard Owusu"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    The mechanical properties of bamboo reinforced sawdust composite briquettes
    (2008-08-25) Asimeng, Bernard Owusu
    The flexural modulus (elastic modulus), flexural strength (bending strength), fracture load, maximum deflection, bulk density and the percentage apparent porosity of sapele (Entandrophragma cylindricum) sawdust and bamboo strip composites have been determined using the static bending test and porosity measurement. The sawdust particles were sieved into three different particles sizes (d): coarse (1400 pm < d < 2000 pm), medium (500 pm< d < 1400 pm) and fine (d < 500 pm). Composite briquettes were formed by arranging bamboo strips in different orientation (planar, oblique and vertical stacking) in a wooden mould of dimension 50 cm x 10 cm x 2.5 cm and the sawdust matrix of approximately the same particle sizes were formed around them, using wood glue as a binder. Pressure was exerted to ensure good bonding. Sawdust briquettes without reinforcement were first formed followed by the composite briquettes. They were then subjected to bending tests. The porosity values of the composite briquettes were also determined. The composite briquettes made from medium stacking configuration with eight strips (M«) were found to have good application in high-performance structure work. It actually produced the combined properties of light weight (low bulk density of 438.21 kg m"3), high flexural modulus of0.240 GPa, high flexural strength of 5.77 MPa, maximum deflection of 3.90 cm and fracture load of 600.71 N. The results indicated that the lighter weight composite briquettes depended on the density of the bamboo strips and the particle size of the sawdust matrix. The incorporation of bamboo strip into the sawdust matrix introduced some degree of flexibility into the composite, but the introduction of too many of them decreases the strength. The changes in the strength and flexibility of the composite briquettes have been explained by stress distribution, interfacial bonding and spacing between the bamboo strips.
  • Thumbnail Image
    Item
    Tensile properties, water absorption and enzymatic degradation studies of polyethylene/starch filled hydroxyapatite blend for orthopaedic applications
    (June, 2016.) Asimeng, Bernard Owusu
    Linear low-density polyethylene (LLDPE)/starch blends filled with hydroxyapatite have been synthesized by injection moulding. The aim was to control the rate of biodegradation of LLDPE/starch blends for bone screw fixation using hydroxyapatite (HA). Hydroxyapatite contents were varied from 1.0% to 3.0% in intervals of 0.5% by parts and the blend phases were characterised using X-ray diffractometry (XRD) and scanning electron microscopy (SEM). Biodegradation was studied by performing water absorption and enzymatic tests. Water uptakes by the samples were carried out according to ASTM D570 and enzymatic test was carried out on samples in phosphate buffered saline (PBS) containing α-amylase. Tensile properties of the samples before and after enzymatic degradation were determined using Titan and Testometric’s universal testing machine while the surface changes were determined with Meiji Techno optical microscope. Seven different samples were formed for the study, two of the samples; one composed of LLDPE only and the other of 60% LLDPE, 40% starch and 0% hydroxyapatite, were used as controls. The results obtained show that the incorporation of starch granules into the LLDPE reduces the tensile strength but almost doubles the tensile modulus and this was attributed to starch granules expanding the amorphous tie chain of LLDPE. Addition of hydroxyapatite into the blend gave an increase in the tensile strength. The increase in strength with increasing HA content was statistically significant at a p-value of 0.0008 and the improvement slowed the rate at which the blend degraded. Hydroxyapatite is suspected to have affected the intermediate phase of the LLDPE by the hydroxyl group through hydrogen bonding. The water absorption by the blends showed that as hydroxyapatite content increased, the moisture uptake of the blends increased and enzymatic degradation rate increased, giving rise to high percentage loss in tensile strength and modulus. Conversely there was a high gain in percentage elongation. Optical micrographs of the surfaces of the degraded samples showed surface erosion and agglomerates. The samples that showed higher erosion and more agglomerates had the highest water uptake and highest percentage loss in tensile strength and those with less erosion and fewer agglomerates had less water uptake and less percentage loss in tensile strength.