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Thesis (Ph. D.)--Institute of Paper Chemistry, 1968. / Includes bibliographical references (p. 69).

Currently, the demand for wood-based panels has been growing solidly in European countries. Medium density fibreboard (MDF) manifests the potentialities for outstanding physical and mechanical properties. However, MDF from different fiber sources is normally designed for internal applications due to the poor moisture resistant capability. This study was conducted on acetylated MDF (Medite® MDF Exterior) to evaluate how physical (i.e. density, moisture content, dimensional stability, thickness swelling) and mechanical (i.e. modulus of elasticity, internal bonding strength before and after accelerated aging, bending stiffness and bending strength) properties behave at different relative humidity (i.e. 35 %, 65 % and 85 % RH at constant temperature of 20 ℃) levels. Bending stiffness was measured non-destructively by means of resonance method. The material used for control samples was commercial MDF. The size, quantity, conditioning and test method were followed in accordance with respective standards. The results showed that physical and mechanical properties were less influenced by Medite® MDF Exterior compared to commercial MDF. Medite® MDF Exterior were superior to commercial MDF in moisture resistance. Medite® MDF Exterior had more stable mechanical properties than commercial MDF with the changes of relative humidity.

Biocomposites have gained increasing attention in recent years. The environmental impacts of common plastics have led researchers and industrials to develop alternatives to fully petro-sourced materials (Beigbeder et al., 2019). This paper presents the results obtained from the life cycle assessments conducted for polystyrene (PS) and biocomposite DuraSense® Pure S40 Impact D (DS40). The aim is for DS40 to serve as a more environmentally friendly option to fossil-based plastic in the manufacturing and recycling of hangers. By replacing 40% of the fossil-based PS with wood fibers, DS40 gains an advantage with regard to its environmental impact. Exercising an LCA on a product offers the opportunity to analyze its environmental impacts and sustainability performance based on a cradle to grave perspective. Thus, to determine which factors that could create an adverse effect in the multiple lifecycles of hangers when recycled, four potential environmental factors were used for modelling several scenarios: loss in quality, end-of-life, travel distance, and packaging. The Global Warming Potential (GWP) - kg CO2 equivalent/functional unit was calculated using the GaBi Envision LCA software for each scenario, which subsequently were compared between PS and DS40. After the modelling of multiple scenarios, this study concludes that a hanger recycling system can be a viable activity due to the improved environmental sustainability. However, to remain as the alternative with the lowest GWP, it is necessary to keep what could be detrimental throughout the lives of the hangers made with DS40 to remain out of the loop. Preventing that the incorrect EoL is chosen, abstaining from the use of PE film as packaging, creating products with competent mechanical properties to have good longevity, and reducing the wasted material in each conversion step, make altogether the replacement of PS with DS40 in the production of hangers a less polluting alternative. The result showed that except for travel distance, all other factors considered have the potential to affect the GWP account, and with this, showing that there is more to consider than just the raw materials needed in the manufacturing of goods.

The aim with this master thesis was to investigate the potential of using non-wood fibers to enhance the paper strength. Abaca, sisal and banana fibers were added to conventional bleached chemical softwood pulp. The effect of refining was investigated, both as co-refining and as separate refining. The fiber properties were determined with a Fiber Tester and the drainage resistance was determined with Schopper-Riegler. Density, tensile index, tear index and burst index were determined on paper sheets made in a Rapid-Köthen sheet former. The results showed that abaca had longer fiber length than softwood, while sisal had slightly shorter fiber length compared with softwood. Sheet density was lowered with addition of all three fiber types, while the drainage resistance was increased for the same. It was also observed that the tensile index increased with additions of abaca, while additions of sisal and banana fibers gave lower tensile indexes. The same trend was observed for the tear index and burst index. Refining gave higher values of the drainage resistance, density, tensile index and burst index. However, the tear index was affected differently depending on the fiber type and fiber blend. For sisal and banana fibers, the tear index was first increased at lower refining degrees and were thereafter decreased with further refining. When studying abaca and softwood, a declining trend was observed over the entire refining interval. The conclusion was that addition of abaca fibers increased all investigated strength properties. Sisal and banana fibers gave higher values of the tear strength, when exposed to mild refining.

Submitted by José Eduardo Estevam da Silva (eduardoposmat@gmail.com) on 2018-04-15T21:56:51Z No. of bitstreams: 1 DISSERTAÇÃO VERSÃO FINAL.pdf: 4070557 bytes, checksum: fb263583bfb8f6573957500e76dce18a (MD5) / Approved for entry into archive by Minervina Teixeira Lopes null (vina_lopes@bauru.unesp.br) on 2018-04-16T19:34:27Z (GMT) No. of bitstreams: 1 silva_jee_me_bauru.pdf: 3974286 bytes, checksum: c0b61a56b4e52184bb3bdb58c2d99f52 (MD5) / Made available in DSpace on 2018-04-16T19:34:27Z (GMT). No. of bitstreams: 1 silva_jee_me_bauru.pdf: 3974286 bytes, checksum: c0b61a56b4e52184bb3bdb58c2d99f52 (MD5) Previous issue date: 2018-01-26 / O processo de fabricação de painéis MDF é muito dinâmico e a todo instante surgem novidades tecnológicas buscando não somente otimizar custos de processo, mas incrementar novas características ou melhorar a resistência mecânica e usinabilidade. As fibras de madeira de eucalipto e as resinas termofixas como a uréia-formaldeído desempenham papel importantíssimo no contexto industrial. Um grande número de pesquisas e estudos se direciona a aperfeiçoar os processos de fabricação por meio do aprimoramento da matéria-prima. Muitos materiais foram desenvolvidos e adicionados tanto as fibras como as resinas sendo muito comum a busca por melhorias na resistência mecânica nas chapas MDF. A resina MDI (metileno difenil diisocianato), por exemplo, possui muitas vantagens conhecidas como a isenção de emissão de formol e a alta resistência a água, porém, outras características relacionadas à interação química com a madeira são pouco estudadas. Nesse contexto tecnológico, o presente trabalho se dedicou ao uso das técnicas termoanalíticas TG/DTG-DTA e DSC para investigar e compreender melhor a interação química entre as fibras de madeira de eucalipto e as resinas sintéticas termofixas e por fim, sugerir melhorias ao processo produtivo buscando assim, reduzir custos de fabricação. Além das técnicas termogravimétricas, a espectroscopia vibracional de absorção na região infravermelho médio com transformada de Fourier também foi usada para auxiliar na proposta reacional de polimerização e principalmente na identificação da estrutura química dos produtos gerados. Investigou-se também o processo de polimerização térmica do monômero MDI bem como sua degradação térmica seguindo as recomendações do ICTAC. As curvas TG/DTG-DTA mostraram que a polimerização foi incompleta em todas as resinas indicando a necessidade de ajustes no processo. A proposta reacional para as resinas UF e MDI está de acordo com os dados das curvas TG e espectros de MIR. A partir da polimerização da resina MDI sugeriu-se a formação de carbodiimidas como produto final. Ao final da pesquisa, algumas melhorias foram propostas como o aumento da temperatura da prensa e a diminuição da concentração de resina visto que na situação atual, a polimerização é incompleta e deixa resíduos nas chapas MDF. Comprovou-se também que as chapas fora de especificação podem ser usadas como biomassa combustível nas caldeiras em substituição ao cavaco de eucalipto, pois liberam mais calor quando estão em combustão. / The process of manufacturing MDF panels is very dynamic and at every moment technological innovations are emerging, seeking not only to optimize process costs, but to increase new characteristics or improve mechanical strength and machinability. Eucalyptus wood fibers and thermoset resins such as urea-formaldehyde play a very important role in the industrial context. A great number of researches and studies are directed at perfecting the manufacturing processes through the improvement of the raw material. Many materials have been developed and added to both fibers and resins, and the search for improvements in mechanical strength in MDF sheets is very common. MDI resin (methylene diphenyl diisocyanate), for example, has many advantages known as formaldehyde emission exemption and high water resistance, but other characteristics related to the chemical interaction with wood are little studied. In this technological context, the present work was dedicated to the use of TG / DTG-DTA and DSC thermoanalytical techniques to investigate and better understand the chemical interaction between eucalyptus wood fibers and thermosetting synthetic resins and, finally, to suggest improvements to the production process thus seeking to reduce manufacturing costs. In addition to the thermogravimetric techniques, the vibrational absorption spectroscopy in the medium infrared region with Fourier transform was also used to aid in the polymerization reaction proposal and mainly in the identification of the chemical structure of the generated products. The thermal polymerization process of the MDI monomer as well as its thermal degradation following the recommendations of the ICTAC were also investigated. The TG / DTG-DTA curves showed that the polymerization was incomplete in all resins indicating the need for process adjustments. The reaction proposal for the UF and MDI resins is in agreement with the data of the TG curves and MIR spectra. From the polymerization of MDI resin the formation of carbodiimides was suggested as the final product. At the end of the research, some improvements were proposed, such as the increase in the temperature of the press and the decrease of the resin concentration, since in the current situation the polymerization is incomplete and leaves residues in the MDF sheets. It has also been proven that non-specification sheets can be used as biomass fuel in boilers instead of eucalyptus chips, as they release more heat when they are in combustion.

The basic ingredient of paper is the individual wood fibers. The property of the fibers depends on a variety of factors e.g., method of pulp production and processing. The final sheet quality depends in part on how the fibers interface between each other and therefore factors that affect the fiber size are of interest. The flexibility of the fibers depends in part on the pore water i.e., the fiber swelling. The sheet becomes less flexible at low water content which gives a loss in strength. Thus it becomes desirable to increase the water uptake. The experimental investigation described in this report consists of exposing the wood fibers to different ions and ionic strength and then measure the pore size by thermoporosimetry where a DSC (Differential Scanning Calorimeter) is used. DSC measures the freezing point of water in the pores of the wood fibers. As the freezing point varies with the pore size the size distribution can be determined. The results show that there are complications with thermoporosimetry measurements at different ion concentrations. The strength of the ionic solutions will contribute to a fictitious pore volume, which makes analysis difficult to interpret.

Wood is a widely used construction material that has many advantageous properties, and some drawbacks. These drawbacks are mainly associated with the porous vascular structure of wood that makes it a high water-absorbent material. In addition, wood’s properties alter substantially with respect to the moisture content. Amongst the treatment techniques that limit the water uptake capacity of wood, vacuum-aided impregnation has exhibited promising results. However, little research has explored the effect of key parameters (such as the vacuum pressure) on the effectiveness of the impregnation. This study aims to optimize the performance of SiO2 impregnation of spruce wood under vacuum pressures. The main objective of this research is to overcome wood’s weakness by reducing its water uptake capacity through a vacuum-aided impregnation technique and study its effect on the physico-mechanical properties of wood under dry and saturated conditions. The study was conducted in two parts. In the first part, wood samples underwent impregnation under atmospheric and three vacuum pressures. Density measurements, water uptake tests, microscopy examination, thermogravimetric analysis, and dynamic mechanical analysis were conducted on non-treated and SiO2-treated samples. Quantitative and qualitative analyses demonstrated that SiO2 impregnation performed under -90 kPa was able to effectively enhance the wood’s properties compared to the other conditions. The SiO2 impregnation under high vacuum pressure demonstrated an effective increase in the density of the wood and achieved a significant reduction in the water uptake capacity. The analysis of the wood’s viscoelastic properties revealed that SiO2 impregnation under atmospheric and vacuum conditions triggered two different reinforcing mechanisms: a solid film, causing stick-slip oscillation, and particle diffusion, causing particle-particle and particle-lumen wall friction, respectively. For the second part, characterization methods such as Impact test, DMA, SEM, EDS, Porosity, and SAXS tests were conducted on non-treated and -90 kPa treated spruce wood samples in dry, saturated, and submerged states in order to reveal the synergistic effect of the SiO2 impregnation pressure and water uptake on the wood’s properties. The results showed that high vacuum impregnation pressure has a significant positive reinforcing effect on the wood’s properties. It increased the impact resistance of wood in dry and saturated conditions. A high vacuum impregnation was able to overcome the softening effect of water and caused a significant increase in the Storage modulus by strengthening the wood’s vascular structure, which accordingly increased the wood’s capacity to absorb energy. High vacuum impregnation was also able to counteract the plasticizing effect of water and significantly increased the Loss modulus by increasing the internal friction in the wood with the diffusion of the nanoparticles in the wood’s cell walls and vascular structure. This phenomenon increased the wood's capacity to absorb and dissipate energy under dry and submerged conditions.

Wood is a viscoelastic composite material that has been historically prominent in the construction of buildings and continues to see widespread use. When used for exterior applications, wood is exposed to dynamic environmental conditions and can degrade if left untreated. Previous research by Lemaire-Paul et al. (2022) has proven that vacuum impregnation of the wood cell structure with a silica (SiO₂) nanoparticle colloid under a vacuum pressure of -90 kPa can enhance the viscoelastic properties, increase the density, and reduce the water uptake of white spruce wood. However, the behaviour of SiO₂-treated wood under different environmental conditions over time has yet to be fully explored. This research aims to examine the durability and performance of SiO₂-treated spruce wood samples subjected to accelerated aging conditions under high temperature and humidity as well as freeze-thaw cycling. Spruce wood samples were treated with 40% SiO₂ nanoparticle colloid under a vacuum pressure of -90 kPa. One set was placed in a hydrolytic aging chamber at 90°C and 80% RH. Another set was placed in a freeze-thaw cycling chamber that cycled from 25°C to -18°C and back at a rate of 6 cycles per day. The samples were removed at regular intervals and thermogravimetric analysis, dynamic mechanical analysis, tensiometry, X-Ray diffraction, and scanning electron microscopy were performed. When compared to the results obtained from a set of non-treated samples, it was found that the SiO₂-treated samples exhibited lower water uptake values that stabilized over time, as well as a lower rate of decrease in peak cellulose degradation temperatures under hydrolytic aging and a slight increase in peak cellulose degradation temperature over time under freeze-thaw aging. The effects of both aging conditions on the viscoelastic properties of the samples were also found to be insignificant. Both types of samples under both types of aging also exhibited an increase in crystallinity over time. These results indicate that the durability and properties of wood can be improved through nano-SiO₂ impregnation as the material remains relatively stable when subjected to high temperature and humidity conditions as well as freeze-thaw cycling over time.

Le travail développé dans cette thèse a pour but d’étudier le comportement hygrothermique de matériaux isolants bio-sourcés, et plus particulièrement les fibres de bois, le béton de chanvre, la laine de lin, la laine de mouton, le métisse® et les anas de lin. Ces matériaux, par essence naturels, présentent des spécificités liées à leur origine (animale ou végétale) et à leur structure (fibres, paille, matrice solide…). Leur porosité, très élevée, les rend réactifs aux variations d’humidité relative ambiante, ce qui peut impacter leurs performances thermiques et leur durabilité (comme pour tous les matériaux), mais également leur conférer des capacités de régulation. Dans un souci d’améliorer la connaissance de ces matériaux particuliers, nous proposons tout d’abord d’étudier l’impact causé par l’humidité sur leurs caractéristiques thermiques, principalement la conductivité thermique et la chaleur spécifique. Ensuite les caractéristiques hygrothermiques sont étudiées, ce qui permet de mieux comprendre les phénomènes dépendant des capacités d’adsorption, de désorption, de perméabilité ou de résistance à la vapeur d’eau. On se rend compte également de l’importance du gradient de température sur l’évolution des transferts hygriques au sein des matériaux. En plaçant les isolants bio-sourcés sous sollicitations aléatoires ou en conditions réelles d’utilisation, nous pouvons suivre leur comportement d’un point de vue expérimental. Le couplage à une approche numérique permet d’identifier les paramètres d’influence prépondérants, dans l’optique de la prédiction des transferts couplés chaleur/masse par une simulation dans des conditions particulières d’utilisation, comme la rénovation d’un habitat existant. On constate à partir de mesures in situ que ces matériaux ont une grande capacité d’adaptation à des environnements dont l’humidité relative est évolutive. / The work developed in this thesis aims to study the hygrothermal behavior of bio-sourced insulating materials, and more particularly wood fibers, hemp concrete, linen wool, sheep wool, material made of textile recycling (metisse®) and flax shives. These materials, which are essentially natural, have specific characteristics linked to their origin (animal or vegetable) and their structure (fibers, straw, solid matrix, etc.). Their very high porosity makes them reactive to the relative humidity variations, which can affect their thermal performances and their durability (as for all materials), but also give them a regulation capacities. In order to improve the knowledge of these particular materials, first, we propose to study the impact caused by moisture on their thermal characteristics, mainly thermal conductivity and specific heat. Then the hygrothermal characteristics are studied, which makes it possible to better understand the phenomena depending on the capacities of adsorption, desorption, permeability or water vapor resistance. Also, we realize the importance of the temperature gradient impact on the evolution of the hygroscopic transfers within the materials. By placing the studied bio-sourced insulation materials under random loading or under real conditions, it will be possible to follow their hygrothermal behavior from an experimental point of view. The numerical approach makes it possible to identify the preponderant influence parameters, in the context of the prediction of coupled heat and mass transfers by simulation under particular conditions of use, such as the renovation of an existing habitat. On the basis of in situ measurements, it can be seen that these materials have a high adaptability to environments whose relative humidity is evolutionary.