Green reinforcement in polymer systems have shown great promise in reducing cost, negative environmental effects, and dependency on nonrenewable resources. Both natural fillers and composite regrind can increase mechanical performance, while reducing new resin inputs for polymer based components. PVC and Polyurethane foam are widely used in North America in high volumes. Ground corn cob greatly increased the modulus of a flexible PVC system while minimally reducing maximum strength. The corn cob also showed signs of being a suitable filler in a polyurethane foam composite panel at low concentrations with minimal changes in mechanical performance. Polyurethane composite regrind illustrated great potential being used in new polyurethane composite panels with acceptable material properties. Replacing just a few percent of polyurethane and PVC with green reinforcement could reduce new production of these polymers by millions of pounds per year in North America alone.

Na área de moagem secundária, ou remoagem, a preocupação com a eficiência energética se mostra de extrema importância. Em geral, os consumos específicos desta etapa são superiores aos da etapa primária. Além disso, tem se observado uma tendência de afinamento das granulometrias de moagem nos novos projetos de minerais metálicos, o que leva cada vez mais a uma maior necessidade de gastos nesta etapa, tanto em termos de custos de implantação como de operação. Nos novos projetos que incluem remoagem no Brasil granulometrias de remoagem da ordem de 40 a 20 m têm se mostrado necessárias. Neste contexto, os moinhos tubulares de bolas, adequados para moagem primária, apresentam eficiências decrescentes em termos de aproveitamento de energia, quando são necessários produtos abaixo de 50 m. A fim de avaliar as melhores alternativas tecnológicas disponíveis para estas aplicações de remoagem, este trabalho estudou moinhos de carga agitada, com foco em moinhos verticais. O presente trabalho apresenta e discute os resultados de amostragens em escala industrial com o moinho vertical em quatro usinas em operação no Brasil. Foi desenvolvido também um novo ensaio em escala laboratorial para simular o consumo de energia e a distribuição granulométrica dos moinhos verticais, que se mostrou válido para a aplicação estudada. / Energy efficiency is extremely important in secondary grinding (regrinding) as specific consumption are greater than obtained in primary grinding. Moreover, finer grinding sizes are a trend in new grinding circuits therefore increasing the energy consumption, as well as respective capital and operating costs. In Brazil regrinding sizes between 40 a 20 m are common in greenfield projects. As horizontal ball mills show decreasing efficiency as grinding sizes are finer than 50 m, this work shows regrinding equipment alternatives to ball mills focusing on vertical mills. A number of survey campaigns were carried out on four industrial operations in which vertical mills were installed in the respective regrind circuit. A new batch test was developed and validated to predict the energy consumption and product size distribution associated to vertical mills.

Na área de moagem secundária, ou remoagem, a preocupação com a eficiência energética se mostra de extrema importância. Em geral, os consumos específicos desta etapa são superiores aos da etapa primária. Além disso, tem se observado uma tendência de afinamento das granulometrias de moagem nos novos projetos de minerais metálicos, o que leva cada vez mais a uma maior necessidade de gastos nesta etapa, tanto em termos de custos de implantação como de operação. Nos novos projetos que incluem remoagem no Brasil granulometrias de remoagem da ordem de 40 a 20 m têm se mostrado necessárias. Neste contexto, os moinhos tubulares de bolas, adequados para moagem primária, apresentam eficiências decrescentes em termos de aproveitamento de energia, quando são necessários produtos abaixo de 50 m. A fim de avaliar as melhores alternativas tecnológicas disponíveis para estas aplicações de remoagem, este trabalho estudou moinhos de carga agitada, com foco em moinhos verticais. O presente trabalho apresenta e discute os resultados de amostragens em escala industrial com o moinho vertical em quatro usinas em operação no Brasil. Foi desenvolvido também um novo ensaio em escala laboratorial para simular o consumo de energia e a distribuição granulométrica dos moinhos verticais, que se mostrou válido para a aplicação estudada. / Energy efficiency is extremely important in secondary grinding (regrinding) as specific consumption are greater than obtained in primary grinding. Moreover, finer grinding sizes are a trend in new grinding circuits therefore increasing the energy consumption, as well as respective capital and operating costs. In Brazil regrinding sizes between 40 a 20 m are common in greenfield projects. As horizontal ball mills show decreasing efficiency as grinding sizes are finer than 50 m, this work shows regrinding equipment alternatives to ball mills focusing on vertical mills. A number of survey campaigns were carried out on four industrial operations in which vertical mills were installed in the respective regrind circuit. A new batch test was developed and validated to predict the energy consumption and product size distribution associated to vertical mills.

The plastics industry is one of the fastest growing major industries in the world. There is an increase in the amount of plastic used for all types of products due to its light weight and ability to reprocess. For this reason, the reprocessing of thermoplastics and the usability of reprocessed materials are gaining significance, and it is important to produce and consume plastic materials in an environmentally friendly way. In addition, rising raw material cost linked to the increased oil prices encouraged for reusing of the plastic materials. The aim of this research was to study and optimize the injection moulding process parameters to achieve a trade-off between the product cost and product quality, measured through mechanical properties and geometry, based on using regrind ratios. The work was underpinned by a comprehensive study of multiple reprocessing effects in order to evaluate the effect of process parameters, material behaviour, reprocessing effects and possible links between the processing parameters and key properties. Experimental investigations were carried out, in particular, focused on the melt preparation phase to identify key process parameters and settings. Multiple reprocessing stages were carried out; using two types of PP material: unfilled and short glass filled. A series of tests were used to examine product quality (mass, colour and shrinkage) and physical properties (density, crystallinity, thermal stability, fibre length, molecular weight, in-line and off-line viscosity, tensile strength, modulus of elasticity, elongation (%) and flexural strength). This investigation showed that the mouldability of the filled and unfilled PP materials, through the successive reprocessing stages (using 100 % regrind), was observed to be relatively consistent. Given the link between the processing parameters and key product and material properties, it is possible to manufacture products with minimal loss to part quality and mechanical properties. The final phase of the work focused on process optimisation study for short glass fibre filled PP material and the identified key process parameters (melt temperature, screw rotational speed, holding pressure, holding time and injection rate). A response surface experiment was planned and carried out for three reprocessing stages (0 %, 25 % and 50 % regrind). The fitted response surface models were utilised to carry out the trade-off analysis between the operating cost (material cost, energy cost and labour cost) and product quality (dimensions and tensile strength) Based on the optimal moulding conditions, the operating cost was reduced (from stage I as a reference), by 24% and 30 % for stage II and stage III respectively. A small, perhaps undetectable, change in product dimensions was noted. In addition, a small reduction in tensile strength was noted (from stage I as a reference), by 0.4% and 0.1 % for stage II and stage III respectively. The same data was applied in other countries (Australia, USA, Brazil, Libya and China) to manufacture the same product; and it was observed that the cost was reduced with increasing of regrind ratio. But the significant reduction of the cost, essentially, depended on those countries which have low wage rates (e.g. Brazil, Libya and China). For example, the cost of moulded product manufactured in China is £ 0.025 (using 50% of regrind), while the cost of the same product produced in Australia is £ 0.12, hence giving a total saving of 79 % and making it a valuable issue to be considered in industry.

The plastics industry is one of the fastest growing major industries in the world. There is an increase in the amount of plastic used for all types of products due to its light weight and ability to reprocess. For this reason, the reprocessing of thermoplastics and the usability of reprocessed materials are gaining significance, and it is important to produce and consume plastic materials in an environmentally friendly way. In addition, rising raw material cost linked to the increased oil prices encouraged for reusing of the plastic materials. The aim of this research was to study and optimize the injection moulding process parameters to achieve a trade-off between the product cost and product quality, measured through mechanical properties and geometry, based on using regrind ratios. The work was underpinned by a comprehensive study of multiple reprocessing effects in order to evaluate the effect of process parameters, material behaviour, reprocessing effects and possible links between the processing parameters and key properties. Experimental investigations were carried out, in particular, focused on the melt preparation phase to identify key process parameters and settings. Multiple reprocessing stages were carried out; using two types of PP material: unfilled and short glass filled. A series of tests were used to examine product quality (mass, colour and shrinkage) and physical properties (density, crystallinity, thermal stability, fibre length, molecular weight, in-line and off-line viscosity, tensile strength, modulus of elasticity, elongation (%) and flexural strength). This investigation showed that the mouldability of the filled and unfilled PP materials, through the successive reprocessing stages (using 100 % regrind), was observed to be relatively consistent. Given the link between the processing parameters and key product and material properties, it is possible to manufacture products with minimal loss to part quality and mechanical properties. The final phase of the work focused on process optimisation study for short glass fibre filled PP material and the identified key process parameters (melt temperature, screw rotational speed, holding pressure, holding time and injection rate). A response surface experiment was planned and carried out for three reprocessing stages (0 %, 25 % and 50 % regrind). The fitted response surface models were utilised to carry out the trade-off analysis between the operating cost (material cost, energy cost and labour cost) and product quality (dimensions and tensile strength) Based on the optimal moulding conditions, the operating cost was reduced (from stage I as a reference), by 24% and 30 % for stage II and stage III respectively. A small, perhaps undetectable, change in product dimensions was noted. In addition, a small reduction in tensile strength was noted (from stage I as a reference), by 0.4% and 0.1 % for stage II and stage III respectively. The same data was applied in other countries (Australia, USA, Brazil, Libya and China) to manufacture the same product; and it was observed that the cost was reduced with increasing of regrind ratio. But the significant reduction of the cost, essentially, depended on those countries which have low wage rates (e.g. Brazil, Libya and China). For example, the cost of moulded product manufactured in China is £ 0.025 (using 50% of regrind), while the cost of the same product produced in Australia is £ 0.12, hence giving a total saving of 79 % and making it a valuable issue to be considered in industry. / Libyan Embassy

The presented diploma thesis deals with the evaluation of the influence of the addition of 30, 60 and 90 % of recycled material on the structure and mechanical properties of high-density polyethylene (HDPE), where recycled material represents both HDPE from a several years old part and material multiple reprocessed by extrusion. The changes of supramolecular structure were examined by calorimetric measurement, which did not indicate degradation of the material due to multiple extrusion. Mechanical properties were investigated by tensile tests and dynamic-mechanical analysis. Both measurements showed the same trend, where the first and second pass of the material through the extruder led to improved mechanical properties, e.g. to increase stiffness, while the influence of the third and fourth passes through the extruder had not a significant effect on the mechanical properties. In terms of the structure and mechanical properties, a positive effect of the combination of material after the second extrusion passing (30%) with virgin material was recorded.