Rogério M. B. Moreno

Thermogravimetric studies of decomposition kinetics of six different IAC Hevea rubber clones using Flynn–Wall–Ozawa approach

Abstract The thermal degradation behaviour of rubber from six new Hevea brasiliensis clones (IAC 40, 56, 300, 301, 302 and 303) from São 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.

Technological properties of latex and natural rubber of Hevea brasiliensis clones

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.

Assessment of growth and yield performance of rubber tree clones of the IAC 500 series

The objective of this work was to evaluate the performance of 15 clones of the IAC 500 series of Hevea brasiliensis, developed at Instituto Agronomico (IAC), over a 12-year period, in the northwest region of Sao Paulo State, Brazil. The 15 new clones evaluated are primary clones obtained from selected ortets within half-sib progenies. The clone RRIM 600, of Malaysian origin, was used as the control. Dry rubber yield performance over a four-year period, mean girth at the tenth year, girth increment before and during tapping, thermal properties of the natural rubber produced and other characters of the laticiferous system were evaluated. Forty percent of the clones were superior in comparison to the control for yield. Clone IAC 500 recorded the highest yield (66.81 g per tree per tapping) over four years of tapping, followed by IAC 502 (62.37 g per tree per tapping), whereas the control recorded 48.71 g per tree per tapping. All selected clones were vigorous in growth. The natural rubber from this IAC clones showed thermal stability up to 300oC. No differences were observed in the thermal behavior of rubber among the IAC series and the RRIM 600 clones. The clones IAC 500, IAC 501, IAC 502, IAC 503 and IAC 506 are the more promising for small-scale plantations, due to growth and yield potential.

Avaliação de clones de borracha natural crua por ensaios padrão e análise dinâmico-mecânica

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.

Thermogravimetric studies of the decomposition kinetics of four different Hevea rubber clones using Ozawa's approach

Thermal degradation behavior of rubber from four rubber clones (RRIM 600, PB 235, GT1 and IAN 873) of the Hevea brasiliensis species was studied by thermogravimetry (TG) using Ozawas approach to assess the kinetic parameters of the decomposition process. These parameters indicated that the thermal behavior of natural rubber depends on the type of rubber clones studied. The order of reaction was found to be dependent on the degree of conversion indicating that both the early and the latter stages of rubber degradation follow zero or pseudo-zero order kinetics whereas the intermediate stages follow a first order kinetics and the activation energy was found to be dependent on the degree of conversion and the type of clone used ragging from 148 to 236 kJ/mol. Rubber from clones IAN 873, GT1 and RRIM 600 presented the best overall thermal stability whereas the clone PB 235 presented the lowest thermal stability, therefore in agreement with the plasticity retention index (PRI) behavior.

Comparação entre folhas sombreadas de sete clones adultos de seringueira

Universidade Estadual Paulista Julio de Mesquita Filho Departamento de Zoologia e Botânica Instituto de Biociencias, Letras e Ciencias Exatas

Monitoramento e Avaliação da Borracha Natural Crua Utilizando a Técnica de Análise Térmica Dinâmico-Mecânica

Resumo: A borracha natural obtida do latex sangrado de quatro clones de seringueira (Hevea brasiliensis) foi preparada pela coagulacao do latex com acido acetico (10%) e seca ao ar a 65 oC (48 horas). Os dados de DMTA foram utilizados para monitorar e avaliar as propriedades termo dinâmico-mecânicas. Os resultados sugerem um possivel aumento na massa molecular media do poliisopreno e, tambem, uma variacao em sua distribuicao para a borracha natural dos quatro clones de seringueira. Palavras-chave: Borracha natural, clones, seringueira, propriedades termo dinâmico-mecânicas. Monitoring and Evaluation of the Raw Natural Rubber Using the Technique of Dynamic Mechanical Thermal Analysis Abstract: Natural rubber of latex tapping of four rubber tree clones (Hevea brasiliensis) were prepared by coagulated latex with acetic acid (10%) and air drying at 65 °C (48 hours). DMTA data were used to monitor and evaluate the thermo dynamic-mechanical properties. The results suggest a possible increase in the average molecular mass of polyisoprene and also a variation in its distribution of natural rubber for four rubber tree clones.

Caracterização mecânica e térmica da borracha natural formulada e vulcanizada dos clones: GT 1, IAN 873, PB 235 e RRIM 600

The objective of this work was to study the mechanical and thermal performance of natural rubber (Hevea brasiliensis) compounds of different types of clones (GT 1, IAN 873, PB 235 and RRIM 600), as well as a mixture made from these clones and a commercial rubber GEB-1. These rubbers were formulated and prepared in a two-roll mill and vulcanized at different times (5, 7 and 9 minutes). The evaluation of the mechanical and thermal performance of different natural rubber compounds was carried out by differential scanning calorimetry (DSC), thermogravimetry analysis (TGA), mechanical properties (tensile and hardness tests), dynamic mechanic thermal analysis (DMTA), scanning electron microscopy (SEM), and infrared spectroscopy (FTIR). The values obtained for glass transition temperature (Tg) for vulcanized rubbers were found to be around -62 °C, while in the hardness test the values obtained were close to 60, with no great variations when the vulcanization time and type of clone were varied. The tensile tests showed that the best performance was obtained for the clone RRIM 600. All the samples studied were in agreement with standard specifications required for application in the rubber industry, indicating that all clones can be used, in principle, in the rubber industry in blended or unblended forms.The objective of this work was to study the mechanical and thermal performance of natural rubber (Hevea brasiliensis) compounds of different types of clones (GT 1, IAN 873, PB 235 and RRIM 600), as well as a mixture made from these clones and a commercial rubber GEB-1. These rubbers were formulated and prepared in a two-roll mill and vulcanized at different times (5, 7 and 9 minutes). The evaluation of the mechanical and thermal performance of different natural rubber compounds was carried out by differential scanning calorimetry (DSC), thermogravimetry analysis (TGA), mechanical properties (tensile and hardness tests), dynamic mechanic thermal analysis (DMTA), scanning electron microscopy (SEM), and infrared spectroscopy (FTIR). The values obtained for glass transition temperature (Tg) for vulcanized rubbers were found to be around -62 °C, while in the hardness test the values obtained were close to 60, with no great variations when the vulcanization time and type of clone were varied. The tensile tests showed that the best performance was obtained for the clone RRIM 600. All the samples studied were in agreement with standard specifications required for application in the rubber industry, indicating that all clones can be used, in principle, in the rubber industry in blended or unblended forms.

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.

Variação sazonal das trocas gasosas, turgescência relativa do tronco e produtividade em dois cultivares de seringueira em Votuporanga, SP, Brasil

RESUMO – (Variacao sazonal das trocas gasosas, turgescencia relativa do tronco e produtividade em dois cultivares de seringueira emVotuporanga, SP, Brasil). Alguns pesquisadores tem enfocado a influencia dos fatores agrometeorologicos e fisiologicos sobre a produtividadeda seringueira, mas a magnitude destas relacoes ainda nao e totalmente conhecida. Assim, no presente estudo, investigou-se a po ssivelrelacao entre alguns parâmetros fisiologicos e a producao de dois cultivares de seringueira, PB 235 e GT 1, cultivados em Votup oranga,Estado de Sao Paulo, durante o periodo seco e umido de 2000-2001. A producao total do periodo foi de 4.550,5 kg/ha, dos quais P B 235respondeu por 59,9%, com producao 12,6% maior que a de GT 1 no periodo seco e 29,8 % no periodo umido. Os valores da taxafotossintetica variaram entre 2,19 e 3,46 µmol m