Browsing by Author "Msemwa, Pelegrin Benedict"

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    Sisal- formaldehyde crosslinked CNSL composites
    (University of Dar es Salaam, 2013) Msemwa, Pelegrin Benedict
    Sisal fibre bundles have high tensile properties that can be used to reinforce polymer matrix in composite materials. However, the presence of surface impurities and their incompatibility to hydrophobic polar resins matrix necessitates for surface modification of the fibre or the resin. Alkalisation with sodium hydroxide was used in this study to chemically modify the surface of sisal fibre bundles in order to improve their compatibility with cashew nut shell liquid (CNSL)-formaldehyde cross linked resin matrix in the manufacture of composites. The sisal fibres bundles samples were alkalised with sodium hydroxide solutions concentrations 0.02 M, 0.04 M, 0.06 M, 0.08 M, 0.5 M, 1.0 M, 1.5 M, 2.0 M and 2.5 M, and analysed for physical, tensile, fine structure and thermal properties in order to determine alkaline concentration that would give optimal fibre properties. It was found that sisal fibre bundles treated with sodium hydroxide solution of concentration of 0.06 M had optimal mechanical and thermal properties. Unidirectional sisal-CNSL composites were manufactured by hand lay-up method using sisal fibres bundles alkalised with sodium hydroxide of various concentrations as above. The effects of alkalisation of the fibre bundles on the physical, thermal, mechanical and thermal-mechanical properties of sisal-CNSL composites were investigated. Sisal-CNSL composites made from sisal fibres bundles alkalised with sodium hydroxide of concentration 0.06 M was observed to produce composites with optimal physical, thermal, mechanical and thermal-mechanical properties. Furthermore, the specific strength and Young’s Modulus of this composite was found to be comparable to that of composites made with synthetics fibres and resins such as carbon-epoxy and glass-polyester composites. The results of this study indicates that renewable materials such as sisal fibre bundles and CNSL-based resin can be used in the manufacture of composites materials that could partially replace synthetic based materials such as carbon-epoxy or glass-polyester in light weight applications. The use of renewable materials in structural applications will contribute to environmental conservation through reduction of pollution associated with production of energy intensive synthetic materials.
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    A Study of the characteristics of the largest foundries in Tanzania
    (University of Dar es Salaam, 1997) Msemwa, Pelegrin Benedict
    An attempt has been made to study the characteristic of the largest foundries in Tanzania with a view of establish problems which hinder their performance and come out with a feasible solution required to solve them. The study was conducted through questionnaires sent to eleven foundries (TAZARA, NECO, TRC, UFI, TATC, MMMT, KIDC, SIDO-Moshi, Galmetal-Arusha, Jandu Plumbers and SIDO-Songea) which are considered to be the largest foundry industries. Data compiled from returned questionnaires and other related studies were evaluated. It was revealed that many of these foundries do not have enough equipment essential for the manufacturing of quality casting products. Also raw materials used by these foundries are of low quality, as a result they produce poor quality products and experience high level of scraps. This study also revealed that 90% of local foundries make sand mould construction using wooden pattern with neither graded nor sieved locally available sand. About 80% of local foundries employ old and outdated moulding machines and sand mixers which are denied maintenances due to lack of spareparts and expertise. Furthermore, about 70% of these foundries lack necessary facilities for control of moud variables and finished products. With respect to the level of technical personnel, this study revealed that about 50% of the local foundries have a foundry engineer and only 30% have technicians who have specialized in the foundry technology, while only 30% have enough artisans to cope up with the available facilities for full capacity utilization. Due to the above problems, less than 40% of local foundry can be categorized under class II of technical performance, and all the rest are class III, while none fails under class I. Upgrading Technical performance of Tanzania foundries should involve provision of all necessary facilities for mould and core making, melting and quality control of the process variables and of products. It is also indispensable for all foundries to have proper maintenance schedule of the available facilities in order to boast up capacity utilization of the available resources (materials, facilities and labour) and also revenue. Furthermore, upgrading foundry technical personnel skills and qualifications is essential if our foundries needs to raise their technical performance. This can be done through the establishment of a Pilot foundry which will be a source of well trained foundry technicians and artisans. Also to provide all locally available raw materials in good quality, a centre should be established which will be in charge of collecting and treating locally available raw materials and therafter supplying to users. Future work is required on locally available foundry raw materials such as scrap, binders, silica sand and refractories, which should lead on preparation of a handbook for local foundries use. An in-depth study is also required on the economic and financial viability of local manufacturing of all sophisticated casting components such as engine block, marine engine parts etc., (class A, and B products). This study should include investment in training of technical personnel and acquisition of machinery and marketing of products.