e beneficiamento da fibra e termina com a industrialização e confecção de artesanato [1,2,[4][5][6] .A planta do sisal é originária da península de Yucatã, no México, tendo recebido este nome de uma erva nativa chamada zizal-xiu [4] . Em 1834, as primeiras mudas foram levadas para o sul da Flórida (EUA) e a partir de 1892 começaram a ser cultivadas na África. No Brasil, as primeiras mudas de Agave sisalana Perrine foram introduzidas na Bahia em 1903, sendo esta a única espécie do gênero Agave cultivada comercialmente no país [5][6][7] . As fibras são extraídas das folhas, que possuem de 8 a 10 cm de largura e de 150 a 200 cm de comprimento. Da folha se obtém de 3 a 5% do seu peso em fibra. Os 95 a 97% restantes constituem os chamados resíduos do beneficiamento, que são utilizados como adubo orgânico, ração animal e pela indús-tria farmacêutica. As fibras são constituídas de fibrilas ou IntroduçãoO sisal é a principal fibra dura produzida no mundo, correspondendo a aproximadamente 70% da produção comercial de todas as fibras desse tipo. No Brasil, o cultivo do sisal se concentra na região Nordeste, sendo os estados da Bahia, Paraíba e Rio Grande do Norte os principais produtores, com 93,5, 3,5 e 3,0%, respectivamente, da produção nacional [1][2][3] . A agaveicultura se concentra em áreas de pequenos produtores, com predomínio do trabalho familiar. O sisal, além de constituir fonte de renda e emprego para um grande contingente de trabalhadores, é um importante agente de fixação do homem à região semi-árida nordestina, sendo, em algumas dessas regiões, a única alternativa de cultivo com resultados econômicos satisfatórios. A fibra do sisal, beneficiada ou industrializada, representa cerca de 80 milhões de dólares em divisas para o Brasil, além de gerar mais de meio milhão de empregos diretos e indiretos por Resumo: Nos últimos anos, o interesse pelo uso de fibras naturais em materiais compósitos poliméricos tem aumentado significativamente. Neste trabalho foram investigadas as propriedades, químicas, físicas, térmicas e estruturais da fibra de sisal brasileira da variedade Agave sisalana. Nosso objetivo foi avaliar a qualidade e o desempenho desta fibra para aplicações industriais. Foram realizados ensaios de resistência à tração, análise da composição química, difração de raios X, e estudos por microscopia eletrônica de varredura (MEV) ao longo do comprimento da fibra. A fibra de sisal brasileira apresentou propriedades mecânicas e térmicas dentro da faixa relatada na literatura, mostrando-se adequada para ser utilizada em materiais compósitos poliméricos. Palavras-chave: Fibras naturais, compósitos, composição química, caracterização. Chemical and Structural Characterization of Sisal Fibers from Agave sisalana VarietyAbstract: In recent years, the interest in the use of natural fibers in polymeric composite materials has increased significantly. In this work were investigated the structural, thermal, chemical, and physical properties of Brazilian sisal fiber from Agave sisalana variety. Our aim was to evaluate th...

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The process of spray drying consists of the transformation of a product in fluid form to the solid state in the form of powder. This is done through the dispersion of droplets from the product inside a chamber, in contact with hot air. In this process, substances known as carriers or encapsulating agents can be added, aiming at facilitating or even allowing the drying of certain products. The objective of this review was to approach the most important technological aspects of the drying by technique for the food industry, as well as showing the potential of using a spray dryer in the micro-encapsulation of bioactive substances.

The present work compared the recrystallization process of Nylon 6 with Nylon 6.6 fibers. For such a study, the fibers were submitted to different annealing conditions (slack and restrained conditions) in a wide range of temperatures. For the structural analysis, several techniques were applied, and among them, differential scanning calorimetry (DSC) was demonstrated to be a very important tool. Nylon 6 and 6.6 fibers responded differently to the applied annealings, indicating different recrystallization mechanisms. The Nylon 6 fiber presented the formation of new and very small crystallites in their interfibrillar regions for the annealings performed above 120ЊC independently of the annealing condition. In addition to their improvement in size and perfection as the annealing temperature increases, their presence favored a general recrystallization in a preferred direction, that is, of the fiber axis. The recrystallization process of the Nylon 6.6 was commanded by the disorientation process associated to the release of the hydrogen bonds. The DSC thermograms revealed two crystalline forms, that is, of the same type but with different degrees of size and perfection. At temperatures below the T g , the less perfect crystallites are converted into more perfect ones, while at temperatures above the T g , the intense movement of the chain segments favored a reversal in this process, that is, the more perfect ones are converted again to the less perfect form.

ABSTRACT:Chopped sisal fibers and finely powdered high-density polyethylene were surface functionalized using dichlorosilane (DS) under radio frequency (RF)-plasma conditions and characterized by electron spectroscopy for chemical analysis (ESCA) and fluorescence labeling techniques. A high-capacity (10 L), rotating, 13.56 MHz, electrodeless plasma installation, specially designed to allow the uniform surface modification of powdery and particulate matter of irregular shape, was used. A three-factor fractional experimental design was employed to evaluate the effect of RF-power, pressure, and reaction time on the ESCA-based relative atomic composition of plasmatreated samples. It was demonstrated that OSiH x Cl y functionalities are present on plasma-exposed surfaces and these functionalization reactions can be controlled by selecting proper plasma parameters.

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Sisal fibers and finely powdered high‐density polyethylene were surface functionalized with dichlorosilane on a RF(radio frequency)‐plasma reactor. Composites made from sisal and high‐density polyethylene were compounded using a thermokinetic mixer. The discharged mass was cooled, granulated, and injected molded into composite specimens for testing. The mechanical behaviors (tensile, impact and thermal dynamical mechanical properties) of composites made from cold plasma‐treated and untreated components are compared and discussed. The best mechanical performance was generally obtained for composites where only the inert thermoplastic matrix was plasma‐functionalized. Plasma treatment of lignocellulosic fibers seems to induce decomposition processes of the surface layers structures exposed to the plasma that generally does not contribute to significant improvement on the mechanical behavior of the composite.

Nylon 6 and 6.6 fibers were submitted to thermal annealing in a wide range of temperatures (below and above their glass transition temperatures) under inert atmosphere and slack condition, allowing free shrinkage. The structural changes due to the heat settings were analyzed by several techniques (differential scanning calorimetry analysis, wide-and small-angle X-ray scattering, and birefringence). The results revealed different recrystallization responses of the fibers to the applied thermal annealings and consequently different shrinkage mechanisms. In the recrystallization of the Nylon 6 fibers were involved a generation of nuclei crystallites in the interfibrillar regions, as well as growth and perfection of these new crystallites and preexisting ones. But, recrystallization of the Nylon 6.6 fiber was accompanied only by growth and perfection of the preexisting crystals. The existence of the nuclei crystallites at temperatures of heat treatments above 120ЊC was the major commanding factor for the Nylon 6 fiber to undergo less shrinkage than the Nylon 6.6 fiber. These very tiny crystallites worked as crosslinking points that would impose restrictions in the mobility of the chains segments, inhibiting subsequent disorientation of the amorphous regions and consequently intense shrinkage, thus resulting in recrystallization in a preferred direction of the fiber axis. The Nylon 6.6 fiber experienced an instantaneous shrinkage at the annealing temperature around 70ЊC. That was the temperature necessary to release its hydrogen bonds and the starting temperature for presenting its major structural changes, including global disorientation of the amorphous and crystalline regions. Thus, its recrystallization occurred with no preferred orientation. Also, it was suggested that the occurrence of so different shrinkage mechanisms reside in the different crystalline morphology that these fibers originally possessed before the heat treatments.