Propriedades tecnológicas do látex e da borracha natural de clones de Hevea brasiliensis

A indústria da borracha está cada vez mais exigente em relação à qualidade e a uniformidade da borracha natural produzida no Brasil. Neste trabalho as propriedades tecnológicas do látex e da borracha natural dos clones de seringueira GT 1, PB 235, IAN 873 e RRIM 600 [Hevea brasiliensis (Willd. ex Adr. de Juss.) Muell.-.Arg] foram avaliadas pelos ensaios padrões do conteúdo de borracha seca (DRC%), porcentagem de nitrogênio (N%) e porcentagem de cinzas (CNZ%) por dois anos consecutivos; os dados obtidos foram correlacionados com dados de temperatura e precipitação. As propriedades do látex e da borracha natural variaram (P < 0.01) em função do tipo de clone e entre coletas. O DRC% diminuiu no início da estação seca (maio a junho), enquanto N% e CNZ% aumentaram. O período de abril a junho revelou ser crítico, pois os valores da N% oscilaram acima 0,60%, fora dos padrões estabelecidos pela norma técnica brasileira ABNT/NBR. O clone RRIM 600 foi menos suscetível às variações climáticas.Rubber industry has increased the requirements for quality and uniformity of natural rubber produced in Brazil. Technological properties of latex and natural rubber of clones GT 1, PB 235, IAN 873 and RRIM 600 [Hevea brasiliensis (Willd. Former Adr. de Juss.) Muell.- Arg] were evaluated by standard methods of the dry rubber content (DRC%), percentage of nitrogen (N%) and percentage of ashes (ASH%) in two consecutive years; data were correlated with temperature and precipitation. Properties of latex and natural rubber varied (P < 0.01) as a function of clone type and among tappings. DRC decreased in the beginning of the dry season (May to June) and N% and ASH% increased in the same period. April to June was a critical period, when N% was above 0.60%, out of standards established by the technical standard ABNT/NBR in Brazil. Clone RRIM 600 was less susceptible to climatic variations

Barrier and mechanical properties of clay-reinforced polymeric nanocomposites

In this work, clay-based nanocomposites films were prepared by addition of clay-Na+ natural montmorillonite in pectin and hydroxypropyl methylcellulose (HPMC) matrices. Mechanical (tensile strength, elastic modulus, and elongation) and barrier (Water Vapor Permeability (WVP), and Oxygen permeability (O2P)) properties were investigated. From results, it was observed that the WVP and O2P decreased when nanoclay was included into the HPMC and pectin matrix films. Additionally, the incorporation of nanoclay in the films significantly improved the mechanical properties because the reinforcing effect of clay from its high aspect ratio and its enormous surface area. These results are very important in packaging area.CNPqFINEPFAPES

Poly(lactic acid)/carbon nanotube fibers as novel platforms for glucose biosensors

The focus of this paper is the development and investigation of properties of new nanostructured architecture for biosensors applications. Highly porous nanocomposite fibers were developed for use as active materials in biosensors. The nanocomposites comprised poly(lactic acid)(PLA)/multi-walled carbon nanotube (MWCNT) fibers obtained via solution-blow spinning onto indium tin oxide (ITO) electrodes. The electrocatalytic properties of nanocomposite-modified ITO electrodes were investigated toward hydrogen peroxide (H2O2) detection. We investigated the effect of carbon nanotube concentration and the time deposition of fibers on the sensors properties, viz., sensitivity and limit of detection. Cyclic voltammetry experiments revealed that the nanocomposite-modified electrodes displayed enhanced activity in the electrochemical reduction of H2O2, which offers a number of attractive features to be explored in development of an amperometric biosensor. Glucose oxidase (GOD) was further immobilized by drop coating on an optimized ITO electrode covered by poly(lactic acid)/carbon nanotube nanofibrous mats. The optimum biosensor response was linear up to 800 mM of glucose with a sensitivity of 358 nA·mM−1 and a Michaelis-Menten constant (KM) of 4.3 mM. These results demonstrate that the solution blow spun nanocomposite fibers have great potential for application as amperometric biosensors due to their high surface to volume ratio, high porosity and permeability of the substrate. The latter features may significantly enhance the field of glucose biosensors.MCT/FINEPCAPESCNP

Evaluation of latex and of raw natural rubber of rubber tree clones recommended for the São Paulo State, Brazil

Este trabalho teve como objetivo avaliar parâmetros do látex e da borracha natural de quatro clones de seringueira [Hevea brasiliensis (Willd. ex Adr. de Juss.) Muell.-Arg.] cultivados em larga escala na Fazenda Cambuhy no Município de Matão, Estado de São Paulo. Foram utilizados látex de 20 árvores do estande de cada um dos clones, GT 1, PB 235, IAN 873 e RRIM 600, com 12 anos de idade, no quarto ano de sangria sob o sistema 1/2S d/3 6d/7. 11m/y. ET 5,0%. Pa 12/y. Foram analisados o conteúdo de borracha seca, porcentagem de cinzas, porcentagem de nitrogênio, plasticidade Wallace (PO), índice de retenção de plasticidade e viscosidade Mooney (VR). O conteúdo de borracha seca apresentou tendência de queda com o decréscimo da temperatura ao longo do ano (r = 0,75). Contrário ao conteúdo de borracha seca, as propriedades porcentagem de nitrogênio e porcentagem de cinzas apresentaram tendência de aumento com a redução da temperatura ao longo do período das coletas. A correlação entre PO e VR foi linear e elevada (r = 0,93). Os altos valores de PO e VR indicam que as borrachas dos clones estudados são consideradas como borrachas duras. Os valores do índice de retenção de plasticidade foram baixos, indicando baixa resistência à degradação térmica. Os resultados mostram influência marcante dos fatores climáticos em algumas propriedades dos látices e da borracha natural dos clones estudados, sugerindo condição importante para se entender o comportamento dos mesmos.The objective of the present paper was to evaluate the parameters of latex and natural rubber from four clones of rubber tree [Hevea brasiliensis (Willd. ex Adr. de Juss.) Muell.-Arg.] planted in large scale in Cambuhy plantations in São Paulo State, Brazil. Latex from 20 trees of each 12-year-old clones viz. GT 1, PB 235, IAN 873 and RRIM 600 following the 1/2S d/3 6d/7. 11m/y. ET 5.0%. Pa 12/y tapping system in the fourth year of yielding. The studied parameters were percentages of dry rubber content (DRC), ashes and nitrogen, Wallace plasticity (PO), plasticity retention index (PRI) and Mooney viscosity (VR). Results indicated a trend of reduction in DRC with decreasing temperatures (r = 0.75). Results of ashes percentages and N percentages indicated a behavior opposite to DRC, increasing with the decreasing temperature along the year. A high correlation value (r = 0.93) was obtained between PO and VR. The high values obtained for PO and VR indicate that the rubber studied should be considered as hard rubbers. The PRI values for these clones were considered low and are associated with a low resistance to thermal degradation. The results obtained indicate a strong influence of climatic conditions on some properties of the lattices and natural rubber for the studied clones. Such parameters suggest an important condition to understand the behavior of these clones

Effect of lubricant on mechanical and rheological properties of compatibilized PP/sawdust composites

AbstractAn investigation was performed regarding the effect of compatibilizer and lubricant concentrations on the mechanical and rheological properties of polypropylene/sawdust composites using two-level factorial central composite design. Maleic anhydride grafted PP (PP-g-MA) was used as compatibilizer and the lubricant used was Struktol TPW 113. Composites without these additives were also prepared. Processing was carried out in a co-rotating twin-screw extruder coupled to a Haake rheometer. Mechanical properties were assessed from tensile tests and rheological properties were evaluated by oscillatory measurements and melt flow index (MFI) test. Tensile strength improved with increasing compatibilizer concentration in the composites and reached a maximum value in the absence of lubricant. When both additives were present tensile strength decreased, suggesting a possible interaction between lubricant and compatibilizer, reducing efficiency of the latter. The general trend observed for rheological results was a decrease in complex viscosity, storage modulus and MFI when both additives were present

Effect of rootstock on the scion of Hevea brasiliensis through metabolic analysis of latex samples by 1H NMR

In this study, the effect of rootstock on grafting through metabolomic analysis of latex (Hevea brasiliensis) samples was verified by 1H nuclear magnetic resonance (NMR) and multivariate data analysis. Sixteen metabolites present in the latex cytosol were characterized by NMR. PCA analysis showed that the latex samples of the RR and GR groups can be differentiated. The GR group samples present a metabolic profile similar to the RR group samples, while the RG group is in an intermediate position between RR and GG groups. Sucrose and formate contributed greatly to the separation obtained by PCA, presenting a good correlation between the results. 1H NMR was an efficient technique to differentiate latex samples from different types of rootstocks and grafting and in the future could be used to predict rubber production by latex analysis

Nanostructured Polylactic Acid/Candeia Essential Oil Mats Obtained by Electrospinning

This work aims to evaluate the effect of inclusion of different contents of candeia (Eremanthus erythropappus) essential oil (whose alpha-bisabolol is the main terpene) on the properties of polylactic acid (PLA) nanostructured mats and their relationship with fiber morphology and structure. The interaction occurring between the PLA and the candeia essential oil was confirmed by thermal and microscopy analysis. Addition of candeia essential oil increased nanofiber diameter and decreased the glass transition and melting temperatures of the nanofibers, suggesting lower energy input for processing. Scanning electron microscopy (SEM) images provided evidence of a homogeneous structure for the nanostructured mats. X-ray diffraction did not show differences in the crystallization of the nanofibers. This ongoing research confirms the possibility of incorporation of candeia essential oil in the production of nanofibers that will be studied for multipurpose applications