Resumo -Este trabalho teve como objetivo avaliar parâmetros do látex e da borracha natural de quatro clones de seringueira [ The high values obtained for P O and V R 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.

This work reports a systematic comparative study of the technological properties of natural lattices and rubbers extracted from Hancornia speciosa Gomes and Hevea brasiliensis [(Willd. ex Adr. de Juss.) Muell.-Arg.] (clone RRIM 600) trees from 11 collections in Brazil throughout 2004. Natural rubber latex particle sizes and distributions were quite similar with an average diameter around 1 lm. Molecular weight, Wallace plasticity, and Mooney viscosity values were approximately the same for both rubbers. Fourier transform infrared spectroscopy peaks characteristic of natural rubber were observed for both Hancornia and Hevea. The measured differences in technological properties included lower values for Hancornia dry rubber content, % ash, % nitrogen, and plasticity retention index but higher value for acetone extract. Interestingly, nitrogen and protein content were much lower in Hancornia, suggesting that it may have important applications in nonallergic rubber uses. This represents the first report of lacticifer-produced low-protein natural rubber. V

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. Key words: rubber tree, standard methods, productivity, environmental conditions PROPRIEDADES TECNOLÓGICAS DO LÁTEX E DA BORRACHA NATURAL DE CLONES DE Hevea brasiliensisRESUMO: 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.

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The latex and natural rubber from rubber trees [Hevea brasiliensis (Willd. exAdr. de Juss.) Muell. Arg.] from clones (RRIM 600, IAN 873, GT 1 and PB 252) recommended to the state of São Paulo, Brazil, were studied in three different tapping systems. The parameters studied were dry rubber content (DRC), percentages of ash and of nitrogen, Wallace Plasticity (P0) and Mooney Viscosity (VR). The rubber properties vary considerably as a function of clone type, tapping method and season of the year. DRC tends to decrease in the beginning of the dry, cold season (May and June), whereas both nitrogen % and ash % increase in the same period. A good linear correlation was obtained for P0 and VR. The highest P0 and VR were obtained for RRIM 600.

The thermal degradation behaviour of rubber from six new Hevea brasiliensis clones (IAC 40, 56, 300, 301, 302 and 303) from Sa ˜o Paulo State, Brazil was studied by thermogravimetry using the Flynn-Wall-Ozawa approach to assess the kinetic parameters (reaction order, activation energy and pre-exponential factor) of the decomposition process. This study indicated that the thermal behaviour is a complex multiple step process, which depends on the type of rubber Hevea clones studied. The rubber from these clones can be classified, following the order of decreasing thermal stability, as IAC 303 . 302 . 56 . 40 . 300 . 301.

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Resumo: A qualidade do látex de borracha natural (Hevea brasiliensis) de diferentes clones (RRIM 600, IAN 873, GT 1, PB 235), uma mistura destes clones e uma borracha comercial foi avaliada por ensaios padrões (plasticidade Wallace, PRI, viscosidade Mooney, % de cinzas, extrato acetônico e % de nitrogênio), DMA, DSC e TG. As borrachas estudadas apresentam propriedades competitivas com as da borracha presente no mercado, ficando dentro dos padrões de qualidade exigidos pela norma brasileira e pelo padrão internacional. Entre os clones, o clone RRIM 600 foi o que apresentou o melhor desempenho, principalmente em relação à viscosidade Mooney e ao PRI. Palavras-chave: Borracha natural, clone, látex, análise térmica. Evaluation of Clones of the Raw Natural Rubber by Standard Test and Dynamic Mechanical PropertiesAbstract: Natural rubber (Hevea brasiliensis) from different clones (RRIM 600, IAN 873, GT 1, PB 235), a mixture made from these clones, and a commercial rubber, have been characterized by DMA, DSC, TGA, and standards methods (Wallace plasticity, PRI, Mooney viscosity, ash percentage, acetonic extract and nitrogen percentage). All the samples studied complied with standard specifications required for application in the rubber industry, and can be used in the rubber industry in blended or unblended forms. Among the clones, the best results of the standards methods were obtained from the RRIM 600 clone, and the blended form of the natural rubber increases its storage modulus.