The considerable volume of chromium-bearing wastes generated during the process of leather tanning, exacerbated by the potential for trivalent chromium in the wastes to be oxidised to the toxic hexavalent state, has created a major waste disposal dilemma for the tanning industry. While methods are available for the safe and effective treatment of residual chrome-tanning liquors, little has been done to address the issue of the chrome-bearing solid wastes. Given the increasingly stringent environmental compliance standards facing tanneries, unless an appropriate treatment process is developed in the immediate future, the continued use of chromium as a tanning agent could be compromised. Recent investigations have demonstrated the potential of heated alkaline conditions for dechroming these solid wastes. This study expanded upon these considerations and examined the feasibility of utilising the highly alkaline tannery waste effluents as cost-effective, substitute alkaline media. The three effluents considered in this study, classed as lime sulphide liquors, were shown to be capable of dechroming wet blue shavings, with resultant separation of the solid wastes into a protein and a concentrated chromium product. The solubilised protein product contained low chromium concentrations which comply with legal discharge limits. The precipitated chromium product offers opportunity for reutilisation in the tannery. A novel industrial-scale treatment process, based on these investigations, indicated the process to be capable of treating the quantity of shavings produced on a daily basis by a medium to large scale tannery. Application of this method for the dechroming of other chrome-tanned solid wastes was also shown to be feasible.

Leather is a widely used material whose handling character is still assessed manually by experienced people in the leather industry. The aim of this study was to provide a new approach to such characterisation by developing Artificial Neural Network models to investigate the relationship between the subjective assessment of leather handle and its measureable physical characteristics. Two collections of commercial leather samples provided by TFL and PITTARDS were studied in this project. While the handle of the TFL collection covered a varied range, the PITTARDS collection was all relatively soft leather and with less difference within the collection. Descriptive Sensory Analysis was used to identify and quantify the subjective assessment of leather handle. A panel constituted of leather experts was organised and trained to: 1) define attributes describing leather handle; 2) assess specific leather handle by responding to questionnaires seeking information about the above attributes. According to the analysis of the raw data and the assessment observation, the attributes that should be used for training the artificial network models were "stiff", "empty", "smooth", "firm", "high density" and "elastic". Various physical measurements relating to leather handle were carried out as follows: standard leather thickness, apparent density, thickness with 1 gram load and 2 gram load, resistance to compression, resistance to stretching, surface friction, modified vertical loop deformation, drooping angle and BLC softness. The parameters from each measurement were all scaled on range 0 to 1 before being fed into network models. Artificial neural networks were developed through learning from the TFL examples and then tested on the PITTARDS collection. In the training stage, parameters from physical measurements and attribute gradings provided by descriptive sensory analysis were fed into the networks as input and desired output respectively. In the testing stage, physical measurement parameters were input to the trained network and the output of the network, which was the prediction of the leather handle, was compared with the gradings given by the panel. The testing results showed that the neural network models developed were able to judge the handle of a newly presented leather as well as an expert. Statistical methods were explored in the development of artificial neural network models. Principal Component Analysis was used to classify the attributes of leather handle and demonstrated that the predominant and most representative attributes out of the six attributes were "stiff", "empty" and "smooth". A network model called physical2panel, predicting the above three attributes from three physical parameters was built up by adopting a novel pruning method termed "Double-Threshold" which was used to decide the irrelevance of an input to a model. This pruning method was based on Bayesian methodology and implemented by comparing the overall connection weight of each input to each output with the limitation of two thresholds. The pruning results revealed that among the sixteen physical parameters, only three of them, - the reading from BLC softness guage, the compression secant modulus and the leather thickness measured under 1 gram load were important to the model. Another network model, termed panel2panel, that predicts the other three attributes "firm", "high density" and "elastic" from the prediction of the model physical2panel was developed and also proved to work as well as a leather expert panel. The conception of a 3D handle space was explored and shown to be a powerful means of demonstrating the findings.

published_or_final_version / Business Administration / Master / Master of Business Administration

No description available.

Vegetable tannins used in tanning of hides and skins are limited to surface reactions by their large molecular weights. The molecular weight reduces penetration into the skin and lowers the thermal stability or tanning effect. Investigation into the utilisation of small phenolic compounds such as catechin to improve penetration with subsequent in situ enzymecatalysed polymerisation may provide a novel and alternative tanning agent. In this research, catechin was oxidised by enzymatic catalysis using laccase, with the polymerisation confirmed by FT-IR and UHPLC. Tanning experiments were undertaken to measure the effect of laccase-catalysed polymerisation of catechin in the thermal stabilisation of collagen, by monitoring the change in shrinkage temperature between the treated and untreated sample of hide powder (ΔTs). This study demonstrates that the stabilisation of collagen (ΔTs) is increased with the use of in situ enzyme-catalysed polymerisation. Depolymerisation of condensed tannins is presented as an alternative source of low molecular weight phenolics to be applied in the stabilisation of collagen. In this research, mimosa tannin from the Black Wattle tree (Acacia mearnsii) was used in the depolymerisation process. Preliminary experiments on depolymerisation were undertaken using the methods laccase-mediator system and L-cysteine in mild acidic medium, both showing unsatisfactory results. Acid-catalysed depolymerisation followed by nucleophile addition is a common analytical method for determining the degree of polymerisation of proanthocyanidins. The acid-catalysed depolymerisation method was scaled-up, with the addition of pyrogallol as a nucleophile trapping agent, and powdered depolymerised mimosa was obtained. Data show an increase in the monomeric content and decrease in percentage of condensed tannins for the acid-catalysed process, indicating the potential of the depolymerisation of mimosa tannin in obtaining environmentally friendly sources of low molecular weight phenolic compounds for use in large scale/industrial applications. The depolymerised product was applied in the stabilisation of hide powder and goat skin. Using hide powder, data show that the laccase-assisted polymerisation of the depolymerised mimosa reached higher values of ΔTs in comparison with the conventional process employing unmodified mimosa. Using goat skin, the new process achieved similar values of ΔTs as the conventional process. In order to obtain similar results for goat skin as obtained with hide powder, an optimisation may be carried out. Therefore, data obtained demonstrates the potential of the new route in vegetable tanning of leather.

Waste management in the leather industry worldwide is an issue of major importance for both solid and liquid wastes. It has been recognised that there are major environmental impacts from the poorly managed disposal of such wastes and these have a clear health impact upon human society. Within Europe, under EU driven legislation, the costs of wastes management are increasing rapidly and there is a clear need to research improved methods to cost effectively deal with leather industry wastes. Biodegradation (anaerobic), as a management option, of solid wastes from the leather industry is an area that is attracting increased interest in recent years as being a technique that has wide public acceptability as well as process efficiency. However, tanning agents that prolong the lifetime of leather goods have a negative impact on biodegradation and this needs to be addressed before efficient treatment can occur. To drive the agenda this research has the aims of • Highlighting the effects of tanning agent on anaerobic digestion. • Understanding the mechanism(s) by which different leather tannages can biodegraded. • Developing a process to reverse the action of tannage. Leather solid wastes were anaerobically digested using Serum Bottle Assays (SBA). The effect of a range of vegetable, mineral and aldehyde tanning agents of leather on the rate of anaerobic digestion was assessed. Common tanning agents used included; myrica, valonea, glutaraldehyde and chrome. To further identify key factors for cost effective anaerobic digestion, tanned hide powders and tanned leathers were also pre-treated using autoclaving, liming, enzymes etc, in an attempt to determine whether tannage may be reversed. Major techniques used in the research include: anaerobic digestion, Biochemical Methane Potential (BMP), Total Solids contents (TS), Gas Chromatography (GC) and Gas Chromatography Mass Spectrometry (GC-MS). Hydrolysable tannins are less resistant to anaerobic digestion than condensed tannins. However, enzymatic pre-treatment reduces the resistance and this offers a new effective pre-treatment route. Thermal pre-treatment also decreased resistance to anaerobic digression especially for chrome, glutaraldehyde, myrica and tannic acid tanned leathers. Chemical pre-treatment also generally lowered the resistance to anaerobic digestion. Selective pre-treatment offers a means of improving the cost effectiveness of anaerobic digestion of leather and therefore enabling a new waste management method to be adopted by the industry. A relationship emerges, in some cases, between chemical structure of tanning agent and inhibition of anaerobic digestion. This offers the possibility of producing new, designed organic tanning agents with, suitable properties, to be adopted by the industiy, The research agenda within the leather industry is still ongoing and recommendations for future research are addressed

SUMMARY Temporary and permanent shells are found in nature which transform with a growing organism and change their form while the organism develops or they are get rid off and grow up again thgrough the living cycle they serve as means of protection. In some cases, we can compare shells with person‘s emotinion states. Individ‘s innerworld, in which, he for some reasons closes in, we can call „shelter“ – he closes in willingly, in other cases the shell might be thrusted by other subject, or by other psychologically or physically stronger individs. Willinglly closed individ, is followed by such subjects as: closeness, not communicating, not improving, torpidity, separation from the world, from inovation. Individ closes in himself, separates from society, feel push off, misundertood. Either society is closed for individual for his not knowing, unwill to understand, to accept him the way he is, for losing relations, for interests missunderstanding, for difference of psichical possibilities. This is a topical issue which excites the minds of not only ordinary people but also artists, sociologist and scientists.

The thesis concerns the persistent coupling of formal and informal industrial relations within a particular manufacturing company. At first, the company's formal structure of industrial relations was heavily tempered by the operation of informal cross cutting ties. The resultant system of industrial relations was one that might be regarded as a hybrid, integrating formal and informal networks of relationships within the organization of the factory. The quite discernible ethos of informality or paternalism remained largely unchallenged by the rather facilitating political conditions that prevailed at the time. However, the political climate has, in the last decade or so, been subject to considerable pressure that has resulted in some far reaching and fundamental changes to the political order of the country. The emergent political conditions have enforced upon the company the need for change. The essence of such changes were perceived to hinge upon the transformation of the company's system of industrial relations. The transformation entailed the establishment of a more overtly formal system of industrial relations, separating the formal and informal relations which had becomes inextricably entwined. However, the objectives of such changes were never quite achieved. The distinction between the formal and informal industrial relations remained submerged in the melee of intergroup contestation. The various interest groups in the factory context appropriated the division between formal and informal industrial relations, enabling these groups to phrase their industrial strategies within an idiom most contextually appropriate. What emerged was an extension of this tendency to merge formal and informal industrial relations. / Thesis (M.A.)-University of Natal, Durban, 1995.

Thesis (Ph. D.)--Duke University, 1990. / Vita. Includes bibliographical references (leaves [1]-14, 2nd group).

Artigos de couro estão associados com tendências de moda e sofisticação em produtos de consumo. No processamento do couro, a fase de acabamento consiste de um conjunto de operações e tratamentos, essencialmente de superfície, que conferem características finais ao produto. Os objetivos do acabamento são reduzir defeitos visíveis, modificar as propriedades superficiais e melhorar os atributos de uso. Nesta fase final, são aplicadas, dentre outros produtos, resinas, geralmente, poliacrilatos e poliuretanos, e algumas vezes caseínas e outros polímeros que formam filmes de recobrimento protetores sobre o couro. Nesse contexto, este trabalho visa a uma avaliação dos filmes formados com resinas comerciais utilizadas industrialmente no acabamento de couros, relacionando a composição destes materiais com características sensoriais, com resistência mecânica, através de testes de tração, com estabilidade à água ou a solvente orgânico, com análise de dureza, e através de caracterizações por infravermelho e DSC. Ensaios de tração mostraram que as resinas poliuretânicas, no geral, apresentam uma maior resistência à tração quando comparadas com resinas acrílicas, assim como os valores de tenacidade, indicando que esses filmes suportam um maior impacto para levar o material à ruptura. A adição de pigmentos diminui essa resistência, tanto em resinas acrílicas quanto em resinas poliuretânicas, enquanto que a produção de filmes compactos apresenta características intermediárias com relação aos componentes puros. Todos os filmes acrílicos testados apresentaram uma maior capacidade de alongamento. Com relação à dureza, as resinas que se mostraram mais flexíveis e com maior alongamento, foram as que apresentaram menor dureza. A estabilidade dos filmes com relação à água e solventes mostrou que os componentes solúveis em água e em solvente aumentam com a presença de pigmento e que a absorção de água é maior e de solvente é menor em filmes com pigmento, tanto para acrilatos quanto para poliuretanos. As caracterizações a partir de análise por FTIR e DSC indicaram os grupamentos químicos e picos de temperaturas característicos dos acrilatos e poliuretanos, respectivamente. / Leather goods are associated with fashion trends and sophistication in consumer products. In the leather processing, the finishing phase consists of a series of operations and treatments, essentially in surface, conferring its final characteristics. The objectives are to reduce visible defects, modify surface properties and improve the usage attributes In this final stage are applied, among other products, resins, generally polyacrylates and polyurethanes, sometimes casein and other polymers, which form protective coating films on leather. In this context, this paper evaluates the films formed with commercial polymeric resins used industrially in finishing leather, relating the composition of these materials with their sensory characteristics, with their strength by tensile testing, with its stability to water or organic solvent, with analysis of hardness and characterizations by IR and DSC. Tensile tests showed that the polyurethane resins in general have a higher tensile strength when compared with acrylic resins, as well as the toughness values, indicating that these films support a greater impact to bring the material to rupture. The addition of pigments decreases this resistance, for acrylic resins and polyurethane resins, while the production of compact film has intermediate characteristics with respect to the pure components. All acrylic films tested had a higher elongation. With respect to hardness, the resins that were more flexible and more stretching, showed the lowest hardness. The stability of the films with respect to water and solvents has shown that water soluble solvent components increased by the presence of pigment and the water absorption is higher and the solvent is lower in pigmented films to acrylates and polyurethanes. The characterizations from IR and DSC analysis indicated the chemical groups and characteristic temperatures peaks of acrylates and polyurethanes, respectively.