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|Title: ||Mitigating the Impact of Non-Isoprene Constituents of Latex on Product Degradation and Process Emissions|
|Authors: ||Adjei, Felix Obiri|
|Issue Date: ||19-Apr-2012|
|Abstract: ||This study assessed the impact of chemical and mechanical pre-treatment methods that could be applied in the natural rubber industry with the objective of process-odour mitigation and product improvement.
In the chemical treatment, fresh latex were treated with of 1% acids (acetic and phosphoric) sufficient to induce coagulation; 1.0 to 2.0 g/kg.dry rubber of hydroxylamine sulphate salts (HNS); and 0.7 to 4.0 g/kg.dry rubber of copper (II) EDTA chelates separately. The impacts of these chemicals on the utilisation of latex carbohydrates and mercaptans generated during 96 h of natural fermentation have been reported. The effects of these chemicals on the resulting product’s Wallace plasticity, Plasticity retention index and Mooney viscosities of each sample were analysed. Hydroxylamine sulphate neither affected the carbohydrates nor the mercaptans generated during the fermentation step. However, acetic acid, phosphoric acid and copper (II) EDTA chelate caused a reduction in the levels of mercaptans and the carbohydrates in the fermenting latex. Hydroxylamine sulphate, acetic and phosphoric acids caused an improvement on the products’ Plasticity retention index, whereas all the concentrations of copper (II) EDTA chelate impacted negatively on both Wallace plasticity and Plasticity retention index of products through the oxidation of the polyisoprene itself.
The impact of mechanical pre-treatment was assessed using industrial mills such as slab cutter, macerator and a series of seven creepers in conjunction with a post milling maturation periods of 0, 168, 336, 504, and 672 hours, taking untreated cuplumps (free and agglomerated) as the control samples.
The impact of each of the combinations of mechanical pre-treatment and maturation periods were expressed in terms of Wallace plasticity, Plasticity retention index, Mooney viscosity, colour, degradation kinetics and odour emitted from the process of drying each sample. It was observed that, irrespective of the pre-treatment process or maturation period, heat degradation of processed NR obeys the first order rate law. Mechanical pre-treatment and maturation caused various degrees of improvement in the product properties as well as odour- mitigation depending on the combination of pre-treatment process and maturation period observed. The mechanical pre-treatment by the use of seven crepers became the optimum process since it simultaneously mitigated the odour and improved product properties beyond 336 h of maturation.|
|Description: ||A Thesis submitted to the Department of Chemical Engineering, Kwame Nkrumah University of Science and Technology, in partial fulfilment of the requirements for the degree of Master of Philosophy, April-2012|
|Appears in Collections:||College of Engineering|
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