Paulo Jansen de Oliveira

Polymers as carriers for rhizobial inoculant formulations

O objetivo deste trabalho foi avaliar a eficiencia de misturas polimericas de carboximetilcelulose (CMC) e amido, como veiculos de inoculante para rizobios, quanto a sua capacidade de manter celulas rizobianas viaveis e promover a nodulacao em feijao-caupi (Vigna unguiculata). O delineamento experimental foi completamente casualizado, com tres repeticoes. Quarenta diferentes composicoes polimericas de carboximetilcelulose (CMC) e amido, compatibilizadas ou nao com proporcoes de MgO ou ZnO, foram inicialmente avaliadas quanto a sua capacidade de manter celulas rizobianas viaveis pelo periodo de um mes. Posteriormente, veiculos de inoculantes selecionados foram avaliados quanto a capacidade de manter celulas rizobianas viaveis pelo periodo de 165 dias, e seu desempenho como veiculos de inoculantes foi comparado com os de inoculantes turfosos, em casa de vegetacao. Celulas rizobianas sobreviveram melhor em misturas com 50-60% de CMC. Os agentes compatibilizantes nao aumentaram a sobrevivencia das celulas rizobianas apos 30 dias de estocagem. A nodulacao do feijao-caupi com o uso das misturas polimericas nao diferiu estatisticamente da nodulacao com o uso da turfa. As misturas de CMC/amido, quando compatibilizadas com MgO (1%), sao veiculos eficientes para inoculantes rizobianos por ate 165 dias de armazenamento.

Produção e comportamento reológico de exopolissacarídeos sintetizados por rizóbios isolados de guandu

The objective of this work was to evaluate the production and the rheological behavior of exopolysaccharides (EPS) produced by pigeonpea [Cajanus cajan (L.) Millsp.] rhizobia isolates, as well as to evaluate the similarity of these isolates through amplified ribosomal DNA restriction analysis technique. The bacteria were cultured in YM liquid media and the EPS were precipited with cold ethanol from culture broth. After that, they were vacuum dried, weighted, stored and resuspended in water to rheological evaluations. The three evaluated isolates showed differences on the production and productivity of EPS, and the isolate 8.1c stood out, with higher relative efficiency. The evaluated EPS showed non-newtonian and pseudoplastic behavior, however they also presented differences as to the apparent viscosity at the same shear rate. At the shear rate of 1 s-1 all isolates were different, while at the shear rate of 40 s-1 the isolates 53.5 and 30.6a2 were the same, differing from the isolate 8.1c. Genetic similarity of the isolates was in agreement with the rheology results, where bacteria that synthesized EPS with lower apparent viscosity presented the higher similarity

Desvulcanização do resíduo de terpolímero de etileno-propileno-dieno (EPDM-r) por micro-ondas

Vulcanized elastomers are materials commonly used in several applications, such as automotive and footwear industries. In this study, scraps of ethylene-propylene-diene terpolymer (EPDM-r) from the automotive industry were exposed to microwaves during different periods (2-5 min). After devulcanization, the samples were characterized by gel content, differential scanning calorimetry (DSC) and activation energy of degradation (Ea) determined by thermogravimetric analysis (TGA). The degradation behavior of EPDM-r was consistent with the literature. The gel content analysis showed that the EPDM-r was devulcanized only at 5 minutes of exposure to the microwaves. DSC analysis demonstrated no significant changes in the samples, and the Ea results confirmed that the additives found in the composition of the EPDM-r affect the efficiency of the regeneration method.

Eficiência agronômica de nova formulação de inoculante rizobiano para feijão-caupi

O objetivo deste trabalho foi avaliar a eficiencia agronomica da formulacao polimerica IPC 2.2 como veiculo de inoculacao para feijao‑caupi. Foi avaliada a sobrevivencia de celulas aos 180 dias de armazenamento. Em experimento de campo, comparou-se a formulacao polimerica com a turfosa e a liquida e com adubacao nitrogenada de 50 e 80 kg ha‑¹ de N e um controle absoluto. A formulacao IPC 2.2 manteve concentracao de celulas superior a 109 g‑1 apos 180 dias e, em campo, proporcionou produtividade de graos superior a do controle absoluto e igual a dos tratamentos nitrogenados e veiculos turfoso e liquido.

Efeito de EPDM modificado nas propriedades mecânicas e no processamento de composições de EPDM contendo resíduo de EPDMR

This work was aimed at examining the effect from three agents in the recycling of waste rubber, namely copolymer ethylene-propylene-diene (EPDMR) containing carbon black. Three agents were prepared: EPDM modified by 1-dodecanotiol (EPDMSDD), EPDM modified by stearic acid (EPDMAE) and EPDM modified by fatty linolenic acid (EPDMAG). For the mechanical properties, the better tensile and tear strength associated with manufacturing extrusion were obtained using EPDMSDD. EPDMAE and EPDMAG improved the processing by extrusion, while keeping the mechanical properties. These results indicate that EPDMAE and EPDMAG act as auxiliary agents for processability.

Efeito da compatibilização da mistura NBR/EVA sobre sua morfologia de fase co-contínua

The influence of ethylene-vinyl acetate copolymer functionalized with mercapto groups (EVALSH) on rheological, morphological and dynamic mechanical properties of nitrilic rubber (NBR)/ ethylene - vinyl acetate copolymer (EVA) blends has been investigated. Selective extraction experiments of NBR phase and scanning electron micrography suggest that co-continuous morphologies were formed in a range of blend compositions from 30 to 60 wt% of EVA. The addition of EVALSH did not affect the co-continuous range but shifted the percolation threshold of NBR-richer blends towards lower amount of EVA. The co-continuous range was also evidenced by dynamic mechanical analysis. Rheological data also revealed that the presence of EVALSH increased the viscosity of the blends containing higher amounts of NBR.