Thesis (M.S.)--University of Wisconsin--Madison, 1989. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 72-75).

This research provides a new insight on various properties, such as rheological, mechanical, and flame-retarding properties, as well as the foaming behaviors of wood flour /plastic composites (WPCs) through the addition of a small amount of nanosized clay particles. Although WPCs have replaced natural wood in many applications, their industrial usage has been limited because of their weak modulus, low impact strength, low screwing-ability/nailing-ability, high density compared to natural wood, as well as their flammability compared to plastics. In this context, the incorporation of nanoclay and foam structure into WPC has been studied to dramatically alleviate these drawbacks. The melt blending method was used to prepare different types of clay-filled wood flour composites such as intercalated and exfoliated clay nanocomposites. The effects of key processing variables such as the mixing time, mixing temperature and screw speed on clay dispersion were investigated from the thermodynamic and kinetic point of view. Their nanostructure was determined by using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Accordingly, effective strategies for controlling intercalation and exfoliation of polyolefin/clay nanocomposites were proposed and evaluated. Wood flour composites with high levels of clay dispersion were synthesized successfully using a general new route (i.e., maleated-polyolefin-based clay masterbatch and dilution). The effects of nanoclay particles on the rheological, thermal, and mechanical properties were identified. In addition, it was demonstrated that a small amount of well-dispersed nanoclay in WPC significantly improved flame retardancy of WPCs. The mechanism of improved flame-retarding effects on nanoparticles was elucidated as well. The relationship between the clay dispersion and the material properties were also clarified. Furthermore, the foaming behaviors of HDPE-based and PP-based wood flour/nanoclay composites were investigated using N2 as the blowing agent in an extrusion process. The cell nucleation and growth behaviors of wood flour/polyolefin/clay composite foams were elucidated while varying the temperature, pressure, wood flour content, clay content and dispersion degrees.

This research provides a new insight on various properties, such as rheological, mechanical, and flame-retarding properties, as well as the foaming behaviors of wood flour /plastic composites (WPCs) through the addition of a small amount of nanosized clay particles. Although WPCs have replaced natural wood in many applications, their industrial usage has been limited because of their weak modulus, low impact strength, low screwing-ability/nailing-ability, high density compared to natural wood, as well as their flammability compared to plastics. In this context, the incorporation of nanoclay and foam structure into WPC has been studied to dramatically alleviate these drawbacks. The melt blending method was used to prepare different types of clay-filled wood flour composites such as intercalated and exfoliated clay nanocomposites. The effects of key processing variables such as the mixing time, mixing temperature and screw speed on clay dispersion were investigated from the thermodynamic and kinetic point of view. Their nanostructure was determined by using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Accordingly, effective strategies for controlling intercalation and exfoliation of polyolefin/clay nanocomposites were proposed and evaluated. Wood flour composites with high levels of clay dispersion were synthesized successfully using a general new route (i.e., maleated-polyolefin-based clay masterbatch and dilution). The effects of nanoclay particles on the rheological, thermal, and mechanical properties were identified. In addition, it was demonstrated that a small amount of well-dispersed nanoclay in WPC significantly improved flame retardancy of WPCs. The mechanism of improved flame-retarding effects on nanoparticles was elucidated as well. The relationship between the clay dispersion and the material properties were also clarified. Furthermore, the foaming behaviors of HDPE-based and PP-based wood flour/nanoclay composites were investigated using N2 as the blowing agent in an extrusion process. The cell nucleation and growth behaviors of wood flour/polyolefin/clay composite foams were elucidated while varying the temperature, pressure, wood flour content, clay content and dispersion degrees.

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The effects of initial particle moisture content, wood-cement ratio and density on physical (thickness swelling and water absorption) and mechanical properties (MOE, MOR, IB and edgewise compression) were investigated. Five initial particle moisture content levels - 0-6%, 8-15%, 25-30%, 40-50% and 60-80%; three wood-cement ratios - 1:1, 1:1.5 and 1:2; and three density levels at each wood-cement ratio - 1:1 -0.472 g/cm³, 0.528 g/cm³ and 0.622 g/cm³, 1:1.5 - 0.636 g/cm³, 0.707 g/cm³ and 0.809 g/cm³; and 1:2 - 0.763 g/cm³, 0.847 g/cm³ and 0.939 g/cm³ were used. Combinations of the above variables gave 45 treatments. Three replicate boards were made for each treatment thus giving a total of 135 panels for the study. A total of 135 test specimens were used for each property tested. Results from the tests were compared to the German and ISO Standards for similar boards and to the Canadian Waferboard Standard. Initial particle moisture content was highly significant in the development of physical and mechanical properties of magnesite cement-bonded particleboard. Increasing initial particle moisture content from 0-6% to 60-80% resulted in the reduction of the physical and mechanical properties of the boards. The highest initial particle moisture content of (60-80%) yielded the lowest physical and mechanical properties. For manufacture of boards of favourable mechanical properties, an initial particle moisture content of not more than 15% is recommended. On the other hand, a higher initial particle moisture content (>40%) is considered desirable if board thickness and water absorption are to be minimized. All the mechanical properties tested consistently increased by increasing wood-cement ratio and density and were highest at 1:2 wood-cement ratio and density level 3 of each wood-cement ratio. Thickness swelling and water absorption were consistently reduced by increasing wood-cement ratio and density. In both physical properties tests, the 1:2 wood-cement ratio and density level 3 yielded the lowest values. Thirty-two of the forty-five treatment combinations of initial particle moisture content, density and wood-cement ratio pass the MOE requirement of the German Standard DIN 52 362 for Portland cement-bonded particleboard; forty-one treatments met the minimum MOE Canadian Waferboard Standard requirements, while no treatment meet the MOR requirements for this Standard. Eleven of the forty-five treatments met the minimum IB Canadian Waferboard Standard requirements. All the 45 treatments pass the ISO building board requirements in thickness swelling, while 18 treatments pass the water absorption requirements for this Standard. Most of the treatment combinations compare favourably with results obtained in tests conducted in Europe for cement-bonded particleboard. / Forestry, Faculty of / Graduate

Graphene nanoplatelets (GNPs) were used to reinforce wood polymer composites (WPCs) in order to achieve multifunctionality. Multifunctionality could be achieved through the GNPs because of their excellent mechanical and electrical properties. The research consists of two parts: HDPE/GNP/WF composites and LLDPE/GNP composites. The HDPE part is a continuation of previous work. Here further mechanical characterisation was done (impact testing), impurities in the composites were identified, the manufacturing process that results in damaged wood particles was investigated and the Young's modulus of the composites were modeled. The impact strength was improved due to the addition of GNPs. WF composites exhibited more brittle behaviour and therefore a lower impact strength. The impurities were identified as some form of nanoclay introduced during the extrusion process. The particles were damaged during the extrusion processes. Little can be done about this as different shear configurations and/or screw speeds will result in a poor GNP dispersion and distribution. Modeling of the Young's modulus was the most accurate through applying the laminate analogy and rule of thumbs. The rule of mixtures does not represent the composites which have a preferred orientation. During the previous work done, it was found that the HDPE composite were not electrically conductive and therefore not multifunctional. The work was therefore continued with LLDPE and GNPs. LLDPE has more branches and is less dense, resulting in potential opportunities for the GNPs to form a network through the polymer. This could lead to a better conductivity. Mechanical and electrical characterisation was done of the LLDPE/GNP composites. Here multifunctionality could also not be achieved as the composites were highly electrically resistant. Mechanical testing indicated that the GNPs significantly enhance the LLDPE matrix. Here an increase of up to 170% could be seen in tensile modulus and an increase of 46% in tensile strength. Furthermore the GNPs improved the flexural properties and increase the resistance to viscoplastic deformation during residual strain testing. Overall the GNPs improve the mechanical properties significantly, but at 10wt.% GNP contents, multifunctionality could still not be achieved.

Made available in DSpace on 2017-07-21T20:42:39Z (GMT). No. of bitstreams: 1 Arieny Rodrigues.pdf: 4134209 bytes, checksum: f2bb4f78c29e8485988b3c7e58f3478f (MD5) Previous issue date: 2011-12-20 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The use of polymeric mixtures has been extensively studied and has great prominence on account of obtaining a material with modified properties from others pre-existing. The polymer composites filled with wood or other natural fibers are a major attraction for presenting a number of advantages over inorganic fillers, for example, low density, and are derived from renewable sources. However, additional efforts are made to improve the interfacial adhesion between these components, because of the lack of compatibility between the wood, a highly polar substance, and polymer materials, nonpolar or with relatively low polarity. The objective of this work was to study the properties of polypropylene composites, both virgin (01 extrusion) and recycled (02 extrusions), using wood flour as reinforcements, compatible with polypropylene-co-acrylic acid (PP-g-AA) and polypropylene-co-maleic anhydride (PP-g-MA), at different concentrations. The materials were mixed in a twin-screw extruder and the characterizations were performed by means of infrared spectroscopy (FTIR), paralell plate rheology, impact tests, scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). This last technique was used to study isothermal and non-isothermal crystallization kinetics / A utilização de misturas poliméricas tem sido muito estudada e apresenta grande destaque por conta da obtenção de um material com propriedades modificadas a partir de outros pré-existentes. Os compósitos de matriz polimérica e carga de madeira ou outras fibras naturais constituem um grande atrativo por apresentar uma série de vantagens sobre cargas inorgânicas, como, por exemplo, baixa densidade, além de serem oriundas de fontes renováveis. No entanto, outros esforços são feitos para se melhorar a adesão interfacial entre estes componentes, por causa da falta de compatibilidade entre a madeira, substância altamente polar, e os materiais poliméricos, apolares ou com polaridade relativamente baixa. O objetivo do presente trabalho foi estudar as propriedades de compósitos de polipropileno, tanto virgem (01 extrusão) quanto reciclado (02 extrusões), utilizando a farinha de madeira como reforço, compatibilizados com polipropileno-co-ácido acrílico (PP-g-AA) e com polipropileno-co-anidrido maleico (PP-g-AM), em diferentes concentrações. Os materiais foram misturados em extrusora dupla-rosca e as caracterizações foram realizadas a partir de espectroscopia por infravermelho (FTIR), reologia de placas paralelas, testes de impacto, análises microscópicas (MEV), e calorimetria exploratória diferencial (DSC). Esta última técnica foi utilizada para estudar a cinética de cristalização isotérmica e não-isotérmica.

O uso de recursos florestais e madeireiros como cargas em matrizes poliméricas pode originar novos materiais com forte apelo ecológico e econômico. Dentre os resíduos do processamento mecânico e químico da madeira, há uma série de materiais de fácil acesso que podem ser manipulados a partir de certas técnicas de biorrefinaria, tais como a madeira, a casca de madeira, as pinhas (frutos do pinus), as acículas (folhas do pinus), a lignina residual (processo kraft) e o lodo de papel derivadas do processo químico de polpação celulósica. Tais matérias primas foram incorporadas em espumas rígidas e semi-rígidas de poliuretano (PU) processadas pelo método da expansão livre, utilizando-se uma mistura de óleo de mamona e glicerina loira como biopoliol, com vistas a obtenção de espumas quimicamente estáveis e ecologicamente corretas. A compatibilidade de algumas dessas cargas no sistema PU foi testada mediante reações induzidas na presença de isocianato e catalisador. As espumas PU foram caracterizadas por meio de técnicas de microscopia e espectroscopia, além de ensaios mecânicos, térmicos, higroscópicos, óticos, de resistência a chamas e de resistência à radiação UV. Por fim, foi avaliado o efeito de expansões sob confinamento nas propriedades morfológicas, mecânicas e térmicas do PU puro e de uma espuma carregada PU/madeira As espumas apresentaram estabilidade química e a inserção das cargas no PU puro possibilitou a obtenção de espumas com células homogêneas, melhor desempenho higroscópico, níveis similares de condutividade térmica e flamabilidade, além de maior brilho e diferentes padrões de cor. A farinha de madeira apresentou a maior afinidade com o sistema PU, seguida pela lignina kraft, resultando em espumas carregadas com células menores, mais arredondadas e com maior teor de células fechadas, além de espumas com maiores estabilidades térmica e dimensional. Todas as espumas apresentaram fotodegradações similares, marcadas por uma cor alaranjada, acompanhada por uma acentuada perda de brilho. As espumas carregadas naturalmente mais escuras foram mais resistentes à fotodegradação por serem capazes de causar um efeito contrário ao da descoloração natural do PU quando sujeito aos raios UV. O confinamento diminuiu o diâmetro médio de células da espuma PU/madeira e a anisotropia do PU puro, levando a formação de células mais homogêneas, marcadas por números de arestas rompidas e de células abertas aparentemente menores, que resultaram em maiores densidades aparentes e melhores propriedades mecânicas para espumas preparadas a 50% de confinamento e menor condutividade térmica para as espumas confinadas a 70%. / The use of forestry and wood-based resources as fillers in polymer matrices may originate new materials with strong environmental and economic appeals. Among the wastes from chemical and mechanical processing of wood, there are many materials readily available, which can be handled through biorrefinary techniques, like wood flour, wood bark, pine cones (fruits), pine needles (leaves), residual lignin (e.g. from kraft process) and paper sludge, the last two from the chemical processing of cellulosic pulp. In this thesis, such raw materials were incorporated into rigid and semi-rigid polyurethane (PU) foams prepared by the free-rising pouring method, using a mixture of castor oil and crude glycerin as a bio-based polyol in order to achieve chemically stable and eco-friendly foams. Compatibility of the fillers with the PU system was evaluated using induced reactions in the presence of isocyanate and catalyst. The PU foams were characterized by microscopy and spectroscopy techniques, as well as mechanical, thermal, hygroscopic, optical, flame resistance and UV radiation resistance tests. And the effect of rising under confinement on the morphological, mechanical and thermal properties of neat PU and wood/PU foam composites was also investigated The foams presented chemical stability and the addition of fillers into PU yielded foams with more homogeneous cells, better hygroscopic performance, similar thermal conductivities and flammabilities, as well as higher specular glosses and different colorimetric patterns. The wood flour presented the highest affinity with the PU system, followed by kraft lignin, resulting in foam composites with smaller and more rounded cells, with higher closed-cells content, and increased thermal and dimensional stabilities. All foams presented similar photodegradation behavior characterized by an orange color and a significant loss in specular gloss. The foam composites, being naturally darker, were more resistant to photodegradation, since they had an opposite effect related to natural discoloration under UV radiation. The confinement decreased cell diameter for the wood filled PU foam and the anisotropy index for neat PU foam, yielding more homogeneous cells, with fewer broken edges and open-cells, with greater apparent densities and better mechanical properties for foams prepared at 50% confinement and lower thermal conductivity for foams confined at 70%.

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