A relatively new type of reinforced composite material, derived from immiscible blends of thermoplastic homopolymers, is characterised in this doctoral research. Microfibril Reinforced Composites (MFCs) utilise common engineering and commodity polymers to create high strength and stiffness microfibrils dispersed in an isotropic matrix. Unlike traditional polymer composites, MFCs use the dispersed component of a blend to create an even distribution of in situ reinforcing microfibrils via a simple extrusion, drawing and processing technique. This research quantifies the mechanical and oxygen gas barrier properties of polyolefin-based MFCs containing polyethylene terephthalate (PET) microfibrils. It is concerned not only with identifying MFCs with the best properties, but also with how manufacturing parameters influence those properties. Characterisation is split into several parts. Initial investigations into blend development during extrusion and drawing were conducted. The main purpose of this was to gain a better understanding of the factors influencing the morphological changes that occur during production. Blend viscosity ratio and capillary number were identified as key factors in determining the onset of coalescence, deformation and break up of the dispersed polymer. The effects on microfibril formation of several important manufacturing parameters were highlighted, with die diameter and extrusion speed the most influential of these. A significant skin-core microstructure was observed. Formation of elongated microfibres (with negligible molecular chain alignment) was shown to occur during extrusion, which was subsequently justified via modelling of the shear stress flow fields in the die. Drawn blends gave very high tensile strengths and stiffnesses due to highly oriented molecular chains. A threshold draw ratio of 3.5, at which properties change considerably, was identified. Mechanical properties of injection moulded MFCs from polypropylene were not considerably better than the neat matrix polymer. However, those from polyethylene (PE) showed significant improvement via injection moulding and directional compression moulding. MFCs with just 30% microfibril content displayed tensile properties up to six times greater than neat PE. Measurements of oxygen gas permeability highlighted improvements of up to 65%. Processing and cooling conditions were shown to significantly influence permeability via a Taguchi experimental design analysis. MFC storage containers from PE/PET were injection moulded as proof-of-concept on completion of the research.

Thermal spray coatings applied with high velocity techniques produce dense, industrial quality coatings with strong adhesion and minimal decomposition. This thesis reports on investigations of splat-substrate interactions for both solid and molten splats. Specifically, individual particles were studied to see how the particle is altered during the spray coating process, how they bond to the substrate and the role of surface oxides. Investigations of NiCr particles high velocity air fuel (HVAF) thermally sprayed onto different materials found that soft substrates predominantly had deeply penetrating solid particles, whereas harder substrates resisted particle penetration and had a higher percentage of molten splats. This effect is caused by particle kinetic energy converted into heat during plastic deformation. The percentage of particle kinetic energy converted into heat is proportional to substrate hardness. It was also discovered that during the coating process the oxide is not removed or altered in composition, but becomes redistributed over a larger surface area due to the plastic deformation of the substrate. During this process, small scale redistribution and penetration of the oxide material by the incoming particle occurs. These results support the idea that successful bonding can occur only when the surface oxide on the substrate and on the coating material has been disturbed (for solid splats) or disrupted (for molten splats). To date, our knowledge of solid splat bonding processes within thermal spray coatings has been very subjective where mechanical and chemical bonding has been expected to contribute. In this thesis, the splat-substrate interface was investigated with focused ion beam (FIB) microscopy, cross-sectional SEM and cross-sectional TEM. For solid NiCr splat HVAF coatings, the discovery of interfacial formations, together with no evidence of chemical bonding across the particle-substrate interface suggest that mechanical bonding is the dominant bonding mechanism for solid splat coatings; where as chemical bonding only plays a role when splats and/or substrate become molten. / GNS Science

A relatively new type of reinforced composite material, derived from immiscible blends of thermoplastic homopolymers, is characterised in this doctoral research. Microfibril Reinforced Composites (MFCs) utilise common engineering and commodity polymers to create high strength and stiffness microfibrils dispersed in an isotropic matrix. Unlike traditional polymer composites, MFCs use the dispersed component of a blend to create an even distribution of in situ reinforcing microfibrils via a simple extrusion, drawing and processing technique. This research quantifies the mechanical and oxygen gas barrier properties of polyolefin-based MFCs containing polyethylene terephthalate (PET) microfibrils. It is concerned not only with identifying MFCs with the best properties, but also with how manufacturing parameters influence those properties. Characterisation is split into several parts. Initial investigations into blend development during extrusion and drawing were conducted. The main purpose of this was to gain a better understanding of the factors influencing the morphological changes that occur during production. Blend viscosity ratio and capillary number were identified as key factors in determining the onset of coalescence, deformation and break up of the dispersed polymer. The effects on microfibril formation of several important manufacturing parameters were highlighted, with die diameter and extrusion speed the most influential of these. A significant skin-core microstructure was observed. Formation of elongated microfibres (with negligible molecular chain alignment) was shown to occur during extrusion, which was subsequently justified via modelling of the shear stress flow fields in the die. Drawn blends gave very high tensile strengths and stiffnesses due to highly oriented molecular chains. A threshold draw ratio of 3.5, at which properties change considerably, was identified. Mechanical properties of injection moulded MFCs from polypropylene were not considerably better than the neat matrix polymer. However, those from polyethylene (PE) showed significant improvement via injection moulding and directional compression moulding. MFCs with just 30% microfibril content displayed tensile properties up to six times greater than neat PE. Measurements of oxygen gas permeability highlighted improvements of up to 65%. Processing and cooling conditions were shown to significantly influence permeability via a Taguchi experimental design analysis. MFC storage containers from PE/PET were injection moulded as proof-of-concept on completion of the research.

Thermal spray coatings applied with high velocity techniques produce dense, industrial quality coatings with strong adhesion and minimal decomposition. This thesis reports on investigations of splat-substrate interactions for both solid and molten splats. Specifically, individual particles were studied to see how the particle is altered during the spray coating process, how they bond to the substrate and the role of surface oxides. Investigations of NiCr particles high velocity air fuel (HVAF) thermally sprayed onto different materials found that soft substrates predominantly had deeply penetrating solid particles, whereas harder substrates resisted particle penetration and had a higher percentage of molten splats. This effect is caused by particle kinetic energy converted into heat during plastic deformation. The percentage of particle kinetic energy converted into heat is proportional to substrate hardness. It was also discovered that during the coating process the oxide is not removed or altered in composition, but becomes redistributed over a larger surface area due to the plastic deformation of the substrate. During this process, small scale redistribution and penetration of the oxide material by the incoming particle occurs. These results support the idea that successful bonding can occur only when the surface oxide on the substrate and on the coating material has been disturbed (for solid splats) or disrupted (for molten splats). To date, our knowledge of solid splat bonding processes within thermal spray coatings has been very subjective where mechanical and chemical bonding has been expected to contribute. In this thesis, the splat-substrate interface was investigated with focused ion beam (FIB) microscopy, cross-sectional SEM and cross-sectional TEM. For solid NiCr splat HVAF coatings, the discovery of interfacial formations, together with no evidence of chemical bonding across the particle-substrate interface suggest that mechanical bonding is the dominant bonding mechanism for solid splat coatings; where as chemical bonding only plays a role when splats and/or substrate become molten. / GNS Science

A relatively new type of reinforced composite material, derived from immiscible blends of thermoplastic homopolymers, is characterised in this doctoral research. Microfibril Reinforced Composites (MFCs) utilise common engineering and commodity polymers to create high strength and stiffness microfibrils dispersed in an isotropic matrix. Unlike traditional polymer composites, MFCs use the dispersed component of a blend to create an even distribution of in situ reinforcing microfibrils via a simple extrusion, drawing and processing technique. This research quantifies the mechanical and oxygen gas barrier properties of polyolefin-based MFCs containing polyethylene terephthalate (PET) microfibrils. It is concerned not only with identifying MFCs with the best properties, but also with how manufacturing parameters influence those properties. Characterisation is split into several parts. Initial investigations into blend development during extrusion and drawing were conducted. The main purpose of this was to gain a better understanding of the factors influencing the morphological changes that occur during production. Blend viscosity ratio and capillary number were identified as key factors in determining the onset of coalescence, deformation and break up of the dispersed polymer. The effects on microfibril formation of several important manufacturing parameters were highlighted, with die diameter and extrusion speed the most influential of these. A significant skin-core microstructure was observed. Formation of elongated microfibres (with negligible molecular chain alignment) was shown to occur during extrusion, which was subsequently justified via modelling of the shear stress flow fields in the die. Drawn blends gave very high tensile strengths and stiffnesses due to highly oriented molecular chains. A threshold draw ratio of 3.5, at which properties change considerably, was identified. Mechanical properties of injection moulded MFCs from polypropylene were not considerably better than the neat matrix polymer. However, those from polyethylene (PE) showed significant improvement via injection moulding and directional compression moulding. MFCs with just 30% microfibril content displayed tensile properties up to six times greater than neat PE. Measurements of oxygen gas permeability highlighted improvements of up to 65%. Processing and cooling conditions were shown to significantly influence permeability via a Taguchi experimental design analysis. MFC storage containers from PE/PET were injection moulded as proof-of-concept on completion of the research.

Thermal spray coatings applied with high velocity techniques produce dense, industrial quality coatings with strong adhesion and minimal decomposition. This thesis reports on investigations of splat-substrate interactions for both solid and molten splats. Specifically, individual particles were studied to see how the particle is altered during the spray coating process, how they bond to the substrate and the role of surface oxides. Investigations of NiCr particles high velocity air fuel (HVAF) thermally sprayed onto different materials found that soft substrates predominantly had deeply penetrating solid particles, whereas harder substrates resisted particle penetration and had a higher percentage of molten splats. This effect is caused by particle kinetic energy converted into heat during plastic deformation. The percentage of particle kinetic energy converted into heat is proportional to substrate hardness. It was also discovered that during the coating process the oxide is not removed or altered in composition, but becomes redistributed over a larger surface area due to the plastic deformation of the substrate. During this process, small scale redistribution and penetration of the oxide material by the incoming particle occurs. These results support the idea that successful bonding can occur only when the surface oxide on the substrate and on the coating material has been disturbed (for solid splats) or disrupted (for molten splats). To date, our knowledge of solid splat bonding processes within thermal spray coatings has been very subjective where mechanical and chemical bonding has been expected to contribute. In this thesis, the splat-substrate interface was investigated with focused ion beam (FIB) microscopy, cross-sectional SEM and cross-sectional TEM. For solid NiCr splat HVAF coatings, the discovery of interfacial formations, together with no evidence of chemical bonding across the particle-substrate interface suggest that mechanical bonding is the dominant bonding mechanism for solid splat coatings; where as chemical bonding only plays a role when splats and/or substrate become molten. / GNS Science

A relatively new type of reinforced composite material, derived from immiscible blends of thermoplastic homopolymers, is characterised in this doctoral research. Microfibril Reinforced Composites (MFCs) utilise common engineering and commodity polymers to create high strength and stiffness microfibrils dispersed in an isotropic matrix. Unlike traditional polymer composites, MFCs use the dispersed component of a blend to create an even distribution of in situ reinforcing microfibrils via a simple extrusion, drawing and processing technique. This research quantifies the mechanical and oxygen gas barrier properties of polyolefin-based MFCs containing polyethylene terephthalate (PET) microfibrils. It is concerned not only with identifying MFCs with the best properties, but also with how manufacturing parameters influence those properties. Characterisation is split into several parts. Initial investigations into blend development during extrusion and drawing were conducted. The main purpose of this was to gain a better understanding of the factors influencing the morphological changes that occur during production. Blend viscosity ratio and capillary number were identified as key factors in determining the onset of coalescence, deformation and break up of the dispersed polymer. The effects on microfibril formation of several important manufacturing parameters were highlighted, with die diameter and extrusion speed the most influential of these. A significant skin-core microstructure was observed. Formation of elongated microfibres (with negligible molecular chain alignment) was shown to occur during extrusion, which was subsequently justified via modelling of the shear stress flow fields in the die. Drawn blends gave very high tensile strengths and stiffnesses due to highly oriented molecular chains. A threshold draw ratio of 3.5, at which properties change considerably, was identified. Mechanical properties of injection moulded MFCs from polypropylene were not considerably better than the neat matrix polymer. However, those from polyethylene (PE) showed significant improvement via injection moulding and directional compression moulding. MFCs with just 30% microfibril content displayed tensile properties up to six times greater than neat PE. Measurements of oxygen gas permeability highlighted improvements of up to 65%. Processing and cooling conditions were shown to significantly influence permeability via a Taguchi experimental design analysis. MFC storage containers from PE/PET were injection moulded as proof-of-concept on completion of the research.

Thermal spray coatings applied with high velocity techniques produce dense, industrial quality coatings with strong adhesion and minimal decomposition. This thesis reports on investigations of splat-substrate interactions for both solid and molten splats. Specifically, individual particles were studied to see how the particle is altered during the spray coating process, how they bond to the substrate and the role of surface oxides. Investigations of NiCr particles high velocity air fuel (HVAF) thermally sprayed onto different materials found that soft substrates predominantly had deeply penetrating solid particles, whereas harder substrates resisted particle penetration and had a higher percentage of molten splats. This effect is caused by particle kinetic energy converted into heat during plastic deformation. The percentage of particle kinetic energy converted into heat is proportional to substrate hardness. It was also discovered that during the coating process the oxide is not removed or altered in composition, but becomes redistributed over a larger surface area due to the plastic deformation of the substrate. During this process, small scale redistribution and penetration of the oxide material by the incoming particle occurs. These results support the idea that successful bonding can occur only when the surface oxide on the substrate and on the coating material has been disturbed (for solid splats) or disrupted (for molten splats). To date, our knowledge of solid splat bonding processes within thermal spray coatings has been very subjective where mechanical and chemical bonding has been expected to contribute. In this thesis, the splat-substrate interface was investigated with focused ion beam (FIB) microscopy, cross-sectional SEM and cross-sectional TEM. For solid NiCr splat HVAF coatings, the discovery of interfacial formations, together with no evidence of chemical bonding across the particle-substrate interface suggest that mechanical bonding is the dominant bonding mechanism for solid splat coatings; where as chemical bonding only plays a role when splats and/or substrate become molten. / GNS Science

No description available.

A utilização de polímeros ligno-celulósicos combinados com polímeros artificiais na forma de materiais compostos é fruto do desenvolvimento de uma linha de pesquisa que tinha como objetivo inicial a utilização dos primeiros como enchimento de uma matriz termofixa ou termoplástica aglutinante. Com o advento da necessidade do reaproveitamento de resíduos de processos industriais, as pesquisas e a utilização de resíduos fibrosos e partículas de madeira cresceram em importância e passaram a contribuir ainda mais decisivamente no desenvolvimento de novas técnicas, processos, equipamentos e insumos que possibilitam ampla gama de aplicações dos produtos obtidos. O presente trabalho objetivou a fabricação de placas compostas de serragem de duas espécies amplamente utilizadas em serrarias combinada com polietileno de baixa densidade reciclável (PEBD). Serragem e farinha de madeira de Pinus elliottii e Eucalyptus grandis , provenientes de lenho e de casca, foram separadas, beneficiadas e misturadas com partículas de PEBD também classificadas por tamanho, na proporção de 40% de madeira e 60% de plástico. A mistura foi prensada a 150 ° C por 30 minutos à pressão de 3 MPa. Foram fabricadas 44 placas de 6 mm de espessura nominal e 40 x 50 cm de lados, em 4 repetições de 11 tratamentos. Foram produzidos corpos-de-prova de todas as placas para os ensaios físicomecânicos segundo a norma ASTM D-1037, determinando-se a massa específica, o teor de umidade, a variação da massa e da espessura ocorridas em 2 e 24 horas de imersão em água, o módulo de elasticidade e o módulo de ruptura na flexão estática, a resistência à compressão e a força máxima de arrancamento de prego e de parafuso de fenda. O lenho de Pinus de granulometria fina combinado com PEBD fino apresentou as melhores propriedades físicomecânicas. Os tratamentos com lenho de Eucalyptus obtiveram o melhor desempenho geral e naqueles em que se utilizou a casca de Pinus os resultados não foram satisfatórios. Dentre os tratamentos que utilizaram cascas, a de Eucalyptus de granulometria grossa foi superior. O lenho de Pinus , principalmente em granulometrias mais finas e homogêneas revelaram-se promissores na utilização externa e as placas obtidas de casca de Pinus revelaram um grande potencial de utilização em usos internos não estruturais, como material alternativo. / Using ligno-celullose polymers combined with artificial polymers in form of composite material is result of a developing research line which had as initial objective the use of the firsts as just filling material in an agglutinant thermoplastic matrix. Due to the necessity of reusing industrial processing residues, the research and utilization of fiber and woody particles had grown in importance and started to contribute on the development of new techniques, processes, equipment and materials that make possible creating a huge variety of products and applications. The present work had the objective of manufacturing composite boards using sawdust from two different species widely used in sawmill combined with recyclable low density polyethylene. Pinus elliotii and Eucalyptus grandis sawdust and wood flour, produced from lumber and bark had been separated, treated and mixed with PEBD particles also classified by size, in the proportion of 40% wood and 60% plastic. The mixture was pressed at 150 °C during 30 minutes under 3 MPa pressure. It were manufactured 44 boards 6 mm nominal thickness and 40 x 50 cm sides in 4 replications of 11 treatments. Samples were obtained from all boards for physicmechanical tests according to ASTM D – 1037 standard, determining specific gravity, moisture content, mass and thickness variation occurred in 2 and 24 hours in water, modulus of elasticity and modulus of rupture in the static bending, compression strength and the withdrawal load of nail and screw. The Pinus wood of thin granulosity combined with thin LDPE had presented better physic-mechanical properties. The treatments in which was used Eucalyptus wood had shown better general performance and those in which was utilized Pinus bark had not presented satisfactory performance. Amongst the treatments in which bark was used, the Eucalyptus of thick granulosity had showed better performance. Boards made of Pinus wood specially in thinner and homogeneous granulosities seems to be excellent for exterior application and those in which was used Pinus bark had shown great potential as an alternative material for non structural purposes for interior applications.