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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Caracterização da bainha fibrosa da palmeira Livistona chinensis para aplicação no design de produto

Jobim, Silvie Janis Mossate January 2018 (has links)
A palmeira Livistona chinensis, nativa do sul do Japão, é muito utilizada como planta ornamental em paisagismos em todo o território brasileiro, e além de adaptar-se bem a vários tipos de solos é de fácil reprodução. Essa palmeira produz uma bainha fibrosa na base de seu pecíolo, que é de fácil extração, plana, flexível e porosa, com características ainda pouco conhecidas e exploradas, é um material de fonte renovável que instiga a criatividade para seu uso tanto de forma artesanal quanto industrial. Neste contexto a caracterização da bainha fibrosa da palmeira Livistona chinensis se torna relevante, pois pode representar um leque de oportunidades para o desenvolvimento de novos produtos para o mercado. A caracterização da bainha fibrosa foi realizada com auxílio de microscópio eletrônico de varredura, espectrometria de energia dispersiva de raios-X, microtomografia, análise termogravimétrica, difração de raios-X, composição química e umidade, espectroscopia no infravermelho por transformada de Fourier Também foram obtidos valores para densidade, gramatura e resistência à tração, incluindo índice de absorção acústica, condutividade térmica e Termografia infravermelha. Os ensaios e análises realizados indicaram que a fibra possui propriedades e características que são comparáveis a outras fibras lignocelulósicas e os resultados estão bem próximas aos encontrados para as fibras de coco, como a composição química, densidade e índice de cristalinidade. Um dos fatores relevantes é o índice de condutividade térmica da bainha fibrosa que se manteve próximo aos valores de materiais isolantes utilizados industrialmente como a lã de rocha e lã de vidro. Quanto aos ensaios de termografia de infravermelho, que apontam seu potencial para ser usado como isolante térmico. / The Livistona chinensis palm, native to southern Japan, is widely used as an ornamental plant in landscaping throughout the Brazilian territory, and besides adapting well to various types of soils, it is easy to reproduce. It produces a fibrous sheath at the base of its petiole, which is easy to extract, flat, flexible and porous, with characteristics still little known and exploited, is a renewable source material, and which instigates creativity for its use both artisanly and industrial. In this context the characterization of the fibrous sheath of palmeira Livistona chinensis becomes relevant, since it can represent a range of opportunities for the development of new products for the market. The characterization of the fibrous sheath was performed with scanning electron microscope, X-ray dispersive energy spectrometry, microtomography, thermogravimetric analysis, X-ray diffraction, chemical composition and humidity, Fourier transform infrared spectroscopy We also obtained values for density, weight and tensile strength, including acoustic absorption index, thermal conductivity and infrared thermography. The tests and analyzes indicated that the fiber has properties and characteristics that are comparable to other lignocellulosic fibers and the results are very close to those found for coconut fibers, such as chemical composition, density and crystallinity index. One of the relevant factors is the thermal conductivity index of the fibrous sheath that remained close to the values of insulating materials used industrially as rock wool and glass wool. Regarding the infrared thermography tests, which point out its potential to be used as thermal insulation.
12

Studies on O2 plasma modification and fluoroalkyl functional siloxane (FAS) coating effects on natural lignocellulosic coir fibers and development of coir based polypropylene (PP)/ethylene-propylene-diene rubber (EPDM) composites / Études sur la modification du plasma O2 et les effets du revêtement siloxane à fonction fluoroalkyle (FAS) sur les fibres de fibre de coco lignocellulosiques naturelles et le développement de composites à base de fibre de coco (PP) / caoutchouc éthylène-propylène-diène (EPDM)

Kosappallyillom Muraleedharan, Praveen 29 June 2018 (has links)
Au cours des dernières années, le développement de matériaux composites avancés fabriqués à partir de fibres naturelles a été principalement axé sur l'obtention de matériaux à haut module et à haute résistance. Cependant, la résistance élevée n'est pas suffisante, car certains des matériaux possèdent une nature fragile (l'allongement à la rupture est faible), et l'un des critères de performance les plus importants devrait être la capacité à absorber l'énergie et à résister aux chocs. La manière dont un matériau composite se déforme et subit des endommagements dépend à la fois des propriétés chimiques et mécaniques de trois constituants de base : les fibres, la matrice et une fine région d'interphase (parfois appelée interface) chargée d'assurer le lien entre matrice et fibre. En raison de leurs propriétés uniques et de leur nature abondante, les fibres à base de cellulose émergent comme un choix privilégié pour les communautés scientifiques, techniques et commerciales qui recherchaient des matériaux durables dans diverses applications. Bien que ces fibres possèdent plusieurs avantages par rapport aux charges synthétiques, l'adhérence entre la fibre et la matrice, la sensibilité à l'humidité et les propriétés au feu restent des domaines difficiles à traiter. Dans ce contexte, une nouvelle technique basée sur la méthode par pulvérisation-séchage-durcissement a permis de fabriquer un revêtement sol-gel hydrophobe sur la surface de la fibre de coco lignocellulosique. La modification de surface des fibres de coco a été effectuée à l'aide d'un plasma oxygène à basse pression suivi d'un enduit sol-gel polymérisable à sec avec un siloxane à fonction fluoroalkyle (FAS). Le prétraitement par plasma a augmenté la concentration effective du réseau FAS sur les fibres de fibre de coco dans le but de créer la surface extrêmement hydrophobe. L'efficacité du traitement plasma et du sol gel FAS sur fibre de coco a été étudiée en utilisant différentes techniques de caractérisation telles que l'analyse de l'angle de contact, l'absorption d'eau, la microscopie électronique à balayage, la microscopie à force atomique et la spectroscopie photoélectronique. Les propriétés mécaniques, morphologiques, rhéologiques et thermiques de différentes formulations de mélanges PP/EPDM ont été étudiées pour trouver la composition optimale du mélange pour la préparation de composites. Les composites résultants à base de polypropylène, d'EPDM et de fibre de coco possèdent des propriétés de résistance aux chocs élevées et des propriétés de traction et de flexion comparables. Les propriétés mécaniques, morphologiques, rhéologiques et thermiques des composites PP/EPDM/Coir ont été étudiées en détail pour examiner la stabilité des composites. / In recent years, the development of advanced high performance composite materials made from natural fibers was mainly focussed on achieving high modulus and strength materials. However, the high strength is not sufficient, as some of the materials possess brittle nature (the overall elongation to fracture is small), and one of the more important performance criterion should be the ability to absorb energy and resist impact loadings. The manner in which a composite material deforms and subjected to fractures depends upon both the chemical and mechanical properties of three basic constituents: the fibers, the matrix and a fine interphase region (sometimes referred to as the interface) responsible for assuring the bond between the matrix and fiber. Due to its unique properties and abundant in nature, lignocellulose based fibers are emerging as a preferred choice for scientific, engineering and commercial communities who were looking for sustainable materials in various applications. Though these fibers possess several advantages over synthetic fillers, adhesion between the fiber and matrix, moisture repellence, flame retardant properties etc are still challenging areas to be addressed. In this context a novel technique based on spray-dry- cure method to establish a hydrophobic sol-gel coating on the lignocellulosic coir fiber surface. The surface modification of lignocellulosic coir fibers was done with the use of low-pressure oxygen plasma, followed by the application of a spray-dry-cure sol–gel coating with the water and oil repellent organic–inorganic hybrid precursor fluoroalkyl-functional siloxane (FAS), with the aim of creating the extremely hydrophobic coir fiber surface. The plasma pre-treatment increased the effective concentration of the FAS network on the lignocellulosic coir fibers. The effectiveness of plasma treatment and FAS sol gel coating on the coir fiber was studied using different characterisation techniques such as contact angle analysis, water absorption studies, scanning electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy. The mechanical, morphological, rheological and thermal properties of different PP/EPDM blend formulations were carried out to find out optimum blend composition for composite preparation. The resulting composites based on polypropylene, EPDM and coir possess high impact strength properties and comparable tensile and flexural properties. The mechanical, morphological, rheological and thermal properties of PP/EPDM/Coir composites were studied in detail to examine the stability of the composites.
13

An examination of longleaf pine cell-wall morphology by electron microscopy of single fibers

Dunning, Charles E. 01 January 1968 (has links)
No description available.
14

Effect of digestion on wood structure

Bixler, A. L. M. (Andrew Loy Moore) 01 January 1937 (has links)
No description available.
15

An examination of longleaf pine cell-wall morphology by electron microscopy of single fibers

Dunning, Charles E., January 1968 (has links) (PDF)
Thesis (Ph. D.)--Institute of Paper Chemistry, 1968.
16

Bugweed, a short fibre source of high potential

Hoto, N. A. (Nceba Antony) 03 1900 (has links)
Thesis (MFor ) -- University of Stellenbosch, 2003. / ENGLISH ABSTRACT: The bulk of paper grades destined for the printing industry are produced on modern paper machines which continuously become wider and faster. In order to improve printability, print quality and dimensional stability, such papers contain a large percentage of mineral pigments either in the form of internal loading or external coatings. Although mineral pigments exercise a substantial beneficial effect on paper surface quality, unfortunately these minerals do not contribute towards sheet strength and machine runnability. Today's papermakers are faced with the dilemma of producing highly filled and coated printing papers with low grammages on faster running paper machines, but often lacking the required quality of fibre resources to secure a smooth runnability of such at high speeds. Standard fibre furnishes will have to be upgraded with special types of reinforcing fibres in order to meet the demands of sheet strength and machine runnability. The investigation had succeeded to identify a new suitable fibre resource, which would satisfy the demand of a reinforcing type natural material. / AFRIKAANSE OPSOMMING: Die oorgrootte meerderheid tipes papier wat vir die drukkersbedryf bestem is, word op moderne papiermasjiene vervaardig wat steeds breër en vinniger word. Om die drukbaarheid, drukkwaliteit en dimensionele stabiliteit te verbeter, bevat sulke papiere groot hoeveelhede minerale pigmente wat in die vorm van interne ladings of as eksterne bestrykings teenwoordig is. Alhoewel minerale pigmente -n merkbare voordelige effek op die papier oppervlakte-kwaliteit uittoefen, dra sulke pigmente ongelukkig nie by tot die sterkte en loopvermoë van die papier nie. Die hedendaagse papiervervaardiger word konfronteer met die dilemma om swaar gevuldeen bestrykte drukpapiere met lae oppervlaktegewig op vinniger lopende papiermasjiene te vervaardig. Dit gebeur dikwels sonder die beskikbaarheid van die nodige hoëkwaliteit veselbronne om te verseker dat die loopvermoë van die papier teen hoë spoed nie benadeel word nie. Standaard veselsamestellings salopgegradeer moet word met spesiale tipe versterkingsvesels om aan die uitdaging van hoë velsterkte en masjien-Ioopvermoë te voldoen. Hierdie ondersoek het daarin geslaag om 'n nuwe geskikte veselbron te dentifiseer en wat aandie behoeftes van 'n versterkingsvesel sal voldoen.
17

Comportement hygro-thermo-mécanique de matériaux structuraux pour la construction associant des fibres de kénaf à des terres argileuses / Hygro-thermo-mechanical behavior of structural materials for the construction associating kenaff fibers with clayed lands

Laibi, Babatounde 21 December 2017 (has links)
Les briques de terre compressée (BTC) à la façon traditionnelle au Bénin présentent de piètres propriétés mécaniques, ce qui explique que les populations recourent aux parpaings de ciment relativement trop couteux et dont l’emploi affecte fortement les ressources en eau et en énergie. Ce travail propose des pistes d’amélioration des BTC pour l’écoconstruction par l’ajout de fibres végétales à des sols usités localement pour la construction. Cette stratégie permet de valoriser les matières premières minérales et végétales dans un domaine d’activités qui concerne une grande partie de la population. Dans un premier temps, un sol a été choisi d’après sa composition chimique, ses propriétés physiques, mécaniques et technologiques. Le choix de la fibre de kénaf pour le renforcement de la matrice minérale se justifie par ses excellentes propriétés mécaniques spécifiques et sa disponibilité à très faible coût. Les effets des fibres sur le comportement du sol au jeune âge, puis sur les comportements mécanique et hygrothermique des matériaux consolidés sous 5 MPa (pression applicable avec les équipements facilement disponibles au Bénin), ont été étudiés pour trois taux massiques de fibres (0,5%; 1% et 1,5% relativement au sol) dans différentes longueurs (5, 10, 20 et 30 mm). Les résultats indiquent une nette amélioration du comportement mécanique des BTC renforcés par le kénaf en termes des résistances à la flexion et à la compression, et de la résistance à la rupture catastrophique (comportement pseudo ductile). Les résultats les plus élevés sont obtenus pour une teneur de 0,5% de fibres de longueur 30 mm. L’ajout de ciment seul au sol fibré (taux de 3, 5 et 7%) ou de ciment associé au laitier de haut fourneau (taux de 3-5% et 5-10%, respectivement) permet en sus d’améliorer de façon importante la résistance à la prise d’eau. Les meilleurs résultats sont obtenus avec 5% de ciment et 10% de laitier de haut fourneau. Les mesures réalisées en chambre biclimatique ont permis de caractériser les matériaux comme paroi séparatrice, en étudiant les transferts de chaleur et de vapeur d’eau. Les résultats mettent en évidence l’effet significatif de l’ajout d’un liant au BTC : L’ajout d’un liant diminue le déphasage et augmente l’atténuation du matériau. Les meilleurs résultats de comportement hygrothermique sont obtenus pour le sol fibré.Cette étude démontre qu’il est possible de produire au Bénin, à partir de matières premières locales et avec des équipements peu onéreux, des éco-matériaux aux propriétés mécaniques et hygrothermiques satisfaisantes pour la construction d’habitat de type R+1. / Traditional Compressed Earth Blocks (CEB) in the Republic of Benin have poor mechanical properties, this justifies why people rely on relatively expensive cement blocks; the use of which greatly affects resources such as water and energy. In this work we have proposed ways to enhance CEB properties for eco-construction by adding plant fibers to locally used construction's soils. This strategy makes it possible to value mineral and vegetable raw materials in a field of an activity that is common to a large part of the population. At first, a soil was chosen according to its chemical composition, its physical, mechanical and technological properties. The choice of kenaf fiber for the reinforcement of the mineral matrix isjustified by its excellent specific mechanical properties and its availability at very low cost. The effects of fibers on soil behavior at young age and on the mechanical and hygrothermal behavior of consolidated materials under 5 MPa (pressure applicable with equipment readily available in Benin) were studied for three mass content of fibers relatively to the soil (0.5% 1% and 1.5%) and different lengths (5, 10, 20 and 30 mm). The results indicated a remarkable improvement in the mechanical behavior of kenaf-reinforced CEBs in terms of flexural and compressive strengths and tolerance to damage. The highest results were obtained with 0.5% of fibers 30 mm long. The addition of a binder (3, 5 and 7% of cement) or (3-5% and 5-10% of cement and blast furnace slag mix) allowed an important reduction in water uptake. The best mechanical results were obtained for a biocomposite made up with BAK soil, 0.5% of flax fibers 30 mm long and a mix of 5% cement and 10% blast furnace slag. Measurements carried out in a biclimatic chamber made it possible to characterize the hydric and thermal behavior of the soil-based materials. The addition of a binder decreases the phase shift and increases the attenuation of the material. These different results show that it is possible to produce in Benin with the available equipment, CEB with mechanical and hygrothermal properties sufficient enought for the construction of type R + 1 habitat.
18

Thermoplastic and Thermoset Natural Fiber Composite and Sandwich Performance

Yang, Bing 05 1900 (has links)
The objective of this thesis is to investigate the effects of adding natural fiber (kenaf fiber, retted kenaf fiber, and sugarcane fiber) into polymer materials. The effects are obtained by considering three main parts. 1. Performance in thermoplastic composites. The effect of fiber retting on polymer composite crystallization and mechanical performance was investigated. PHBV/PBAT in 80/20 blend ratio was modified using 5% by weight kenaf fiber. Dynamic mechanical analysis of the composites was done to investigate the glass transition and the modulus at sub-ambient and ambient temperatures. ESEM was conducted to analyze fiber topography which revealed smoother surfaces on the pectinase retted fibers. 2. Performance in thermoset composites. The effect of the incorporation of natural fibers of kenaf and of sugarcane combined with the polyester resin matrix is investigated. A comparison of mechanical properties of kenaf polyester composite, sugarcane polyester composite and pure polyester in tensile, bending, dynamic mechanical thermal analysis (DMA) and moisture test on performance is measured.. 3. Performance in sandwich composites. The comparison of the performance characteristics and mechanical properties of natural fiber composites panels with soft and rigid foam cores are evaluated. A thorough test of the mechanical behavior of composites sandwich materials in tensile, bending and DCB is presented here.
19

A fibre optimisation index developed from a material investigation of Eucalyptus grandis for the Kraft pulping process.

Du Plessis, Marius 03 1900 (has links)
Thesis (PhD (For))--Stellenbosch University, 2012. / ENGLISH ABSTRACT: A primary reason for the existence of the forest industry is to provide a renewable and natural resource for much needed timber and fibre products. Substantial improvements in management practices are required to increase forest volume and pulp yields for increased demand. Eucalyptus grandis clonal trees of age 6.75 years, grown in a Nelder 1a spacing experiment, were sampled and analysed to describe the effect of planting density on i) growth and yield, ii) wood properties and iii) pulp and paper quality. The main objective was to populate a fibre productivity index (FPI) which would be suitable from technical and economical perspectives. A material study was conducted on the wood and in addition, two methods were developed to further describe the variability of the forest resource to i) separate growth rings by means of wood density peaks from gamma-ray densitometry and ii) calibrate near infrared (NIR) prediction models. The results indicated that planting density did not influence the variability of wood density but mechanisms affecting available soil water are important. NIR prediction models were developed to rapidly and reliably assess wood properties on a non-destructive basis. The validation models for wood density, total pulp yield, kappa number and insoluble lignin returned high predictive ability. When applied to predict chemical properties from an independent data set, the outcomes were accurate in comparison with measured data. Growth and yield functions were developed for tree survival, dominant height and basal area. They accurately predicted outcomes as demonstrated by the goodness of fit and their logical behaviour tested over the range of planting densities. When the most extreme stand density treatments, 6809 and 275 trees per hectare (TPH) were evaluated for wood and fibre properties, the larger trees grown at 275 TPH, produced wood of better quality for pulp processing; basic wood density at 0.520 g cm–3 (21 % higher), fibre cell wall thickness at 2.10 μm (18.6 % thicker) and fibre lumen diameter at 8.16 μm (9.9 % lower) than for 6809 TPH. Intra-specific tree variability of wood and product properties increased from diameter at breast height (DBH) to 35 % and then decreased to 65 % of tree height. The effect of planting density was carried throughout the product value chain up to the paper manufacturing phase. Paper with higher bulk mass and thickness and more porous sheets is most likely to be made from lower planting densities (801 and 275 TPH), and stronger, smoother and denser paper is most likely to be made with trees at high planting densities (6809 or 2336 TPH). From the growth and yield and materials investigation, technical indicators identified to populate a fibre productivity index were: i) mean annual increment (MAI) as a forestry growth indicator, ii) wood density, summarising the composition of wood and, iii) pulp yield, the indicator of the amount of fibre processed through a chemical cooking process. Delivered cost of timber to the mill, was identified as the most suitable economic indicator which included fixed costs elements, variable costs and aspects of mill efficiency. The product of the technical and economic indicators concluded in a profit/loss scenario of producing 1 ton of pulp was deemed the best index to describe the entire and integrated value chain. This index, termed the Fibre Productivity Index (FPI) at the Mill, denoted as FPMill, is an integrated index that is easy to interpret in the realms of a forestry - pulp manufacturing, and can be used for differential pricing of timber for wood quality. / AFRIKAANSE OPSOMMING: 'n Primêre rede vir die bestaan van die bosbouindustrie is om ‘n hernubare, natuurlike hulpbron vir hout en vesel te voorsien. Aansienlike verbeterings in bestuurspraktyke is nodig om die houtvolume en pulpopbrengste vir die toename in aanvraag te verhoog. Eucalyptus grandis klonale bome met ‘n ouderdom van 6.75 jaar en wat in 'n Nelder 1a spasiëring eksperiment gegroei is, is versamel en ontleed om die effek van opstandsdigtheid te beskryf op a) groei en opbrengs, b) houteienskappe en c) pulp- en papiergehalte. Die hoofdoel was om 'n veselproduktiwiteitsindeks (FPI), wat geskik sou wees in terme van tegniese en ekonomiese perspektiewe, te ontwikkel. 'n Materiaalkundigestudie is op hout uitgevoer. Twee metodes is ontwikkel om die variasie in hout as natuurlike hulpbron te beskryf deur a) vroeëhout- en laathoutdigtheidspieke deur gammastraal-densitometrie van mekaar te skei en variasie in groeiringe te beskryf en b) daarstelling van naby-infrarooispektroskopiese (NIR) voorspellingsmodelle. Die resultate het aangedui dat aanplantingsdigtheid nie ‘n invloed het op die variasie van houtdigtheid nie, maar dat meganismes wat beskikbare grondwater bepaal, belangrik is. NIR-voorspellingsmodelle is ontwikkel om houteienskappe op 'n nie-destruktiewe manier betroubaar te kan evalueer. Die validasiemodelle vir houtdigtheid, pulpopbrengs, kappanommer en onoplosbare lignien, openbaar akkurate voorspellingsvermoë. Wanneer dit toegepas word om chemiese eienskappe van 'n onafhanklike datastel te voorspel, was die resultate akkuraat in vergelyking met gemete data. Groei- en opbrengsfunksies is ontwikkel vir mortaliteit, dominante boomhoogte en basale area. Akkurate voorspellingsuitkomste is verkry soos gedemonstreer deur die logiese gedrag wat getoets is vir alle plantdigthede. Toe die mees ekstreme opstansdigtheidbehandelings vir hul hout- en veseleienskappe geëvalueer is, was die hout van die groter bome, teen 275 stamme per hektaar (SPH), van beter gehalte. Dit was veral prominent vir houtdigtheid van 0.520 g cm-3 (21 % hoër), veselselwanddikte van 2.10 μm (18.6 % dikker) en vesellumendeursnit van 8.16 μm (9.9 % laer) as by die hoër (6809) SPH. Intra-spesifieke boomvariasie van hout- en produkeienskappe het toegeneem van deursnee op borshoogte (DBH) tot 35 % en dan weer afgeneem tot 65 % van die boomhoogte. Die effek van plantdigtheid is regdeur die produkwaardeketting tot by die papiervervaardigingstadium sigbaar. Papier met hoër basismassa en dikte, en meer poreuse papiervelle kan meer waarskynlik van laer aanplantdigtheid (801 en 275 TPH) bome gemaak kan word. Papier wat sterker, gladder en digter is, kan waarskynlik gemaak word van hout van bome teen hoë aanplantdigthede (6809 of 2336 SPH). Die veselproduktiwiteitindeks wat ontwikkel is uit die materiaalondersoek en tegniese aanwysers wat geïdentifiseer is sluit in i) gemiddelde jaarlikse aanwas, as 'n bosbou groei-indikator, ii) houtdigtheid, wat ‘n opsomming van die samestelling van hout is, en iii) pulpopbrengs; die aanduiding van die hoeveelheid vesel verwerk deur 'n chemiese verpulpingsproses. Gelewerde koste van hout by die pulpmeul is geïdentifiseer as die mees geskikte ekonomiese aanwyser wat vaste kosteelemente, veranderlike koste en aspekte van die meul se doeltreffendheid insluit. Die produk van die tegniese en ekonomiese aanwysers is saamgevat in 'n wins / verlies opsie vir die vervaardiging van 1 ton pulp, en is beskou as die mees geskikte indeks om die geïntegreerde waardeketting te beskryf. Dié indeks, die sogenaamde Vesel Produktiwiteitsindeks (VPI) by die Pulpmeul, aangedui as VPMeul, is 'n geïntegreerde indeks wat maklik is om te interpreteer in 'n bosbou - pulpvervaardigingsopset, en kan gebruik word in die differensiële prysbepaling van hout waarby die kwaliteit in ag geneem word.
20

Progresso genético no melhoramento de algodoeiro no Estado de Mato Grosso. / Genetic gain in cotton breeding in Mato Grosso state, Brazil.

Moresco, Edina Regina 06 June 2003 (has links)
O melhoramento genético vegetal visa a obtenção de novos genótipos que representem algum tipo de ganho comparado aos genótipos em uso pelos agricultores. Para verificar se este objetivo está sendo alcançado, é necessário avaliar o desempenho do programa de melhoramento. Visando quantificar o progresso genético do programa da Embrapa para melhoramento de algodoeiro (Gossypium hirsutum L.) para as condições do estado de Mato Grosso, foram avaliados os dados de 12 anos de pesquisa para os caracteres produtividade de caroço (Kg/ha) e rendimento de fibra (%). Foram utilizadas três metodologias, sendo uma baseada em contrastes entre genótipos comuns em anos consecutivos (metodologia de Vencovsky et al., 1986) (VE), e duas baseadas em regressão linear de médias ajustadas (metodologias de Breseguello, 1998 e de Fonseca Júnior, 1997, respectivamente BR e FJ). Apenas as metodologias de regressão apresentaram estimativas significativas para o progresso genético. Para produtividade (Kg/ha), o progresso genético médio anual obtido pelas metodologias BR e FJ foram respectivamente 3,93% e 3,63%. Já para o caráter rendimento de fibra (%), o progresso genético médio anual para as mesmas metodologias foi respectivamente 0,96% e 1,03%. Os genótipos que apresentaram maior contribuição ao progresso genético para produtividade e rendimento de fibra foram respectivamente a linhagem FMTB 99-03 e a cultivar BRS Cedro. A taxa de substituição de genótipos calculada foi de 55,92%. Com base nos dados obtidos nesta pesquisa, pode-se concluir que após 12 anos de pesquisa no estado de Mato Grosso, o melhoramento genético da Embrapa algodão produziu resultados positivos e significativos, refletido nas estimativas de ganho genético médio. / The main objective of a breeding program is the development of new cultivars, with presents some genetic gain when compared with obsoletes cultivars, allowing farmers to increase their net income. In order to evaluate the performance of genotypes developed by EMBRAPA Cotton Breeding Program carried out in Mato Grosso State, the genetic gain was estimated for yield and lint percent based on 12 years of data set. Three methods were considered for estimation of genetic gain, one based on contrasts among common genotypes (Vencovsky et al., 1986) (VE); and two based on regression of adjusted mean {Breseguello et al., 1998 (BR) and Fonseca Júnior, 1997 (FJ)}. Estimates of genetic gain were positive and significant for the two methods based on regression. The average genetic gain estimated to yield by BR and FJ methods were respectively 3.93% and 3.63%. For lint percent, the average genetic gain estimated by the same methods were 0.96% and 1.03%, respectively. The Genotypes FMTB 99-03 and BRS CEDRO provided the maximum contribution to yield and lint percent, respectively. From the results above and after 12 years of research, it was concluded that Embrapa cotton breeding program in Mato Grosso State achieved positive and significant results which were reflected in a high average of genetic gain estimates.

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