Resumo: Nanocompósitos a base de poli(etileno-co-acetato de vinila) (EVA) e óxido de sílica (SiO 2 ), com tamanho nanométrico da ordem de 40 nm, foram preparados via intercalação por solução, empregando clorofórmio como solvente. Os nanocompósitos foram caracterizados principalmente pela espectroscopia de ressonância magnética nuclear (RMN), empregando a análise dos núcleos de carbono-13 (matriz polimérica); silício-29 (nanopartícula) e pela determinação do tempo de relaxação spin-rede do núcleo de hidrogênio no eixo rotatório (T 1ρ H) (matriz polimérica). Pelos dados de RMN foi observado que até cerca de 5% de sílica em massa obteve-se um nanocompósito polimérico com boa dispersão da sílica devido a uma forte interação entre a sílica e matriz de EVA. Palavras-chave: Nanocompósitos, RMN, EVA, sílica. Preparation of EVA/SILICA Nanocomposites Characterized with Solid State Nuclear Magnetic ResonanceAbstract: Nanocomposites of poly(ethylene-co-vinyl acetate)/silica (SiO 2 ) with dimensions of ca. 40 nm were prepared via solution intercalation employing chloroform as a solvent. They were mainly characterized with nuclear magnetic resonance spectroscopy (NMR) employing carbon-13 (polymeric matrix), silicon-29 (nanoparticles) and through the determination of the proton spin-lattice relaxation time in the rotating frame (T 1ρ H) (polymer matrix). From the NMR results it was inferred that up to 5% of silica in mass a well dispersed nanocomposite was obtained, owing to a strong interaction between silica and the EVA matrix. Keywords: Nanocomposites, NMR, EVA, silica. IntroduçãoA incorporação de cargas inorgânicas em polímeros origina materiais híbridos, nanocompósitos, com maior resistência mecânica, maior estabilidade térmica ou com propriedades ópticas, magnéticas ou elétricas superiores. As cargas tendo dimensões nanométricas (1-100 nm) apresentam uma área de superfície elevada, promovendo melhor dispersão na matriz polimérica e por isso, uma melhoria das propriedades físicas do compósito, que dependem da homogeneidade do material. A preparação de nanocompósitos de matriz polimérica permite, em muitos casos, encontrar um compromisso entre um baixo custo, devido à utilização de menor quantidade de carga, e um elevado nível de desempenho, que pode resultar da sinergia entre os componentes [1][2][3][4][5][6][7][8][9] .O desenvolvimento de materiais nanocompósitos ressalta a necessidade de se desenvolver métodos absolutos e inovadores de caracterização destes tipos de materiais, já que o estudo dos mecanismos de formação de híbridos, bem como das interações que ocorrem ao nível da interface inorgânica/orgânica são de grande interesse e de fundamental necessidade, para o entendimento do comportamento desses materiais em nível macroscópicos, visto que a morfologia do nanocompósito é o fator que dita as suas propriedades. É sabido que alterações nas propriedades ópticas, elétricas e/ou mecânicas de um material, à medida que se passa da forma macrocristalina para um material constituído por partículas de dimensões nanométrica...
This work search for new environmentally friendly applications for the fibers of banana pseudostem. The morphological characteristics of the cellulosic fibers originated from pseudostem allows obtaining fabrics with good mechanical properties. Observing the potential of banana agribusiness disposal that MusaFiber Company realized, in this fibrous residue, an opportunity for the development of new products. Fibers were extracted mechanically from the banana pseudostems, then, the obtained fibers were characterized in relation to the diameter, tensile strength, elongation at break by tensile tests and its morphological structure by scanning electron microscopy. The mechanical tests revealed much better tensile strength (590 MPa) when compared to other natural fibers, such as jute (249 MPa) and sisal (350 MPa). The highest mechanical strength is due to the high degree of crystallinity of this fiber (~ 67%) calculated from the FTIR spectrum and to its morphology.
The garment industry demands stamping processes that are increasingly more agile and less damaging to the environment. In this scenario, digital printing, with the sublimation transfer printing technique, presents itself as a viable option for synthetic textile substrates. Among the synthetic fibres, polyamide (P.A.) fibres stand out, as they are light, soft, durable, and boast moderate sweat absorption; however, before sublimation, superficial treatment is necessary in order to present good results such as withstanding washing and maintaining colour intensity. This study addresses the surface modification of the PA6.6 textile substrate by activating non-thermal plasma at atmospheric pressure to receive dye through the sublimation method with dispersed dye. The knitted PA6.6 fabric surface treatment was performed with plasma application at atmospheric pressure using air in the Plasmatreater AS400 equipment. The sublimation transfer effects were evaluated by wash fastness and colourimetric tests. To assess the wettability effect of the control and treated samples, a contact angle test was carried out on PA6.6 samples. Fourier transform infrared spectroscopy (FTIR) proved the changes in chemical functional groups in the fibres. The results showed a decrease in the contact angle of the textile surface, 4–5 grayscale results for colour change and transfer for washing, and an increase in colour strength. In the FTIR tests, there is an increase in the transmittance value of aromatic, carboxylic groups (C=O, 580 cm−1), amides (N=H, 1630 cm−1), and methyl groups (CH 1369 to 1463 cm−1) as well as the presence of new functional groups in the 3064 cm−1 and 2860 cm−1 bands. These conditions allowed sublimation in the knitted PA6.6 fabric and showed increased colour strength and good wash fastness.
Nanocomposites based on ethylene-co-vinyl acetate (EVA) and silica oxide (SiO2), with nanometric size (40nm) were prepared by solution process, employing chloroform as solvent. The nanocomposites were mainly characterized by solid state nuclear magnetic resonance spectroscopy (NMR). From the methodology employed polymer matrix was evaluated by the determination of proton nuclear spin-lattice relaxation time (T1H) and spin-spin relaxation time (T2H) employing low field NMR spectrometer and also applying carbon-13 (13C) solid-state NMR techniques and proton spin-lattice relaxation time in the rotating frame (T1pH) by high field NMR. The nanoparticle, silica oxide, was analyzed by silicon-29 (29Si) NMR MAS spectrum. The evaluation of relaxation time showed an increase in the proton spin-lattice relaxation time, because of silicon nucleus interaction with polymer chains promoting an increase in the sample rigidity, which is a result of good silica oxide dispersion in the polymeric matrix. The nanomaterial with 5% of SiO2presented good dispersion of silica oxide in the polymeric matrix, because of the formation of strong intermolecular interaction.
The evaluation of cotton fibers from Nuclear Magnetic Resonance (NMR) in solid state using high and low-field showed to be a good alternative to evaluate these materials. The main objective of this work was to use the solid-state NMR techniques to accompany the fibers nature, size and morphology to have a direct method to evaluate cotton fibers maturity. We could conclude that the solid-state NMR techniques are good source to evaluate the molecular behavior of cotton short and long fibers and give important information on sample's morphology, indicating that this technique can be used to distinguish the size of cotton fibers.
Os corantes sintéticos utilizados no segmento têxtil, além de gerarem grande impacto ambiental, podem causar problemas à saúde humana, como dermatites de contato. Os corantes naturais podem ser uma alternativa a eles, alguns possuindo, até mesmo, propriedades que ofereçam proteção UPF. Considerando a biodiversidade brasileira e o interesse mundial, este artigo pretende contribuir para o desenvolvimento de um corante oriundo de substratos da espécie Dipteryx alata Vogel, que além de seus variados benefícios à saúde também poderá ser utilizado como corante natural e agente de fotoproteção. Os resultados obtidos do desenvolvimento do método de tingimento de substratos têxteis apresentam informações interessantes, mas que exigem continuidade nos estudos para melhora com o propósito de alcançar novos mercados. Palavras Chave: corante natural; fotoproteção; têxtil.The synthetic dyes used in the textile segment, besides generating great environmental impact, can cause problems to human health, such as contact dermatites. Natural dyes may be an alternative to them, some even possessing properties that offer UPF protection. Considering Brazilian biodiversity and world interest, this article aims to contribute to the development of a dye from Dipteryx alata Vogel, which besides its various health benefits can also be used as a natural dye and photoprotection agent. The results obtained from the development of the method of dyeing textile substrates present interesting information, but which require continuity in studies for improvement in order to reach new markets.
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