Microbial population dynamics in rubber coagula from Hevea brasiliensis

Natural rubber produced from the tree Hevea brasiliensis is a material of first importance for the tyre industry and for many other sectors such as the vibration isolation and the general rubber good industries. To produce TSR10 or 20 block rubber, trees are tapped, and the produced latex coagulates a few hours later in the collection cup. The fresh coagulate of natural rubber is then subjected to a maturation process that involves complex microbial populations. These microorganisms were shown to influence the biochemical composition and the properties of the final material [1]. This study intends to better understand the dynamics of microbial populations during the maturation process through culture-dependent and high-throughput culture-independent methods (454 pyrosequencing). (Résumé d'auteur

Method of making formulated plastic separators for soluble electrode cells

A method making a membrane comprised of a hydrochloric acid-insoluble sheet of a mixture of a rubber and a powdered ion transport material is disclosed. The sheet can be present as a coating upon a flexible and porous substrate. These membranes can be used in oxidation-reduction electrical accumulator cells wherein the reduction of one member of a couple is accompained by the oxidation of the other member of the couple on the other side of the cell and this must be accompained by a change in chloride ion concentration in both sides. The method comprises preparing a mixture of fine rubber particles, a solvent for the rubber and a powdered ion transport material. The mixture is formed into a sheet and dried to produce a microporous sheet. The ion transport material includes particles ranging from about 0.01 to 10 microns in size and comprises from 20 to 50 volume percent of the microporous sheet

Rubber smallholders' flexibility No windfall, no crisis

A few decades ago rubber was one of the first tree crops to be characterized by a spectacular breakthrough, the production of new, highly productive clonal material. With regard to rubber, the adoption of clonal planting materials led to a spectacular improvement in labour-productivity and revenues. It requires also different cropping patterns during immature period. An increase in return to labour costs is usually the first priority of smallholders. As this adoption of clones by smallholders only started in the 1970s in Indonesia, this is an extremely important strategy which must be stressed before we begin to analyze the impact of the krismon (a contraction of “Krisis Monetar” in Indonesian or “monetary crisis”). With regard to rubber, there is clearly a dualism of seedlings and clonal material. This dualism is more important than with other tree crops. Rubber seedlings are often grown under a complex agroforestry system and nicknamed locally ‘jungle rubber'. Clonal rubber is generally grown in monoculture sometimes with intercrops during the first three years.“Even when computing the cost of the investment and the credit that has to be repaid, the net income per hectare and per labour day from a clonal plantation is at least 50% higher (sometimes 100%) than the income from a jungle rubber plantation” (Gouyon 1999, 31). What was the situation before krismon? Due to capital and information constraints, only 15% of the smallholders already had access to highly productive clonal material rubber in 1996. This percentage was achieved, first and foremost, through official projects. Then in the late 1990s, the “copying effect” started playing its role, however rather limited. More and more farmers were able to observe the advantages of clonal material. This led to a booming network of private nurseries that helped to accelerate the adoption of this material. This means that a relatively strong dynamism was observed before krismon. It also means that most clonal plantations are still young, which is important in terms of potential response to price changes (Chapter 1). However, when krismon arrived, around 85% of traditionnal rubber farmers still relied on ageing jungle rubber with limited productivity. How may krismon influence these ‘jungle rubber' and ‘clonal' farming systems? Is it going to accelerate or reduce the investment in rubber plantings? Is it going to help to accelerate the adoption of clones? In 1998, rubber farmers did not benefit from the spectacular windfall, which affected cocoa and coffee (Chapters 5-7). Can this be explained by the different performances of farming systems or by variations of the International market? Is there a direct relationship between the decline of global prices and the interference of the Asian crisis in Indonesian rubber supply and exports (Chapter 2)? Page 2 How did the monetary crisis affect the other dramatic changes faced by Indonesian rubber smallholders? In addition to the economic crisis, as in other regions of the country, the ecological crisis also struck Sumatra and Kalimantan in 1997-98. Huge fires destroyed millions of hectares of forests, fallows and crops, including rubber. Will both crisis reduce investment in clonal plantings? Eventually, regions such as West-Kalimantan were the theatre for grave social troubles related to conflicts between autochtons and some immigrants, especially spontaneous immigrants1. A lack of confidence in the country's regime was evident well before the crisis. Last but not least, oil palm development looms in traditional rubber regions. Might it hamper the development of clonal rubber technology in Indonesia? Does the crisis encourage the adoption of oil palm at the expense of rubber? Does the crisis deepen the social imbalance between smallholders who already have access to clones and those who do not? To try to answer these questions , the paper is structured in 4 sections: 1 A brief overview of the rubber sector : the situation before krismon 2 Krismon and its impact on rubber smallholdings 3 The rubber crisis on the international market 4 A conclusion including the future for the rubber smallholder sector

Integration of biotechnologies for rubber tree improvement. What about rootstock clones ?

Breeding and dissemination of planting material for rubber plantations are closely linked to propagation methods. Since the progress made by shifting from multiplication by seed to propagation by budding, the development of new techniques, such as micropropagation, has been awaited. New varietal types such as self-rooted plants, rejuvenated budded clones, genetically modified organisms, and rootstock material were developed from microcutting and somatic embryogenesis techniques at the research level. The development of rootstock clones adapted to the selected scion clones is likely to be the most promising approach to improve significantly rubber tree for various agronomical traits such as tree growth, tolerance to wind damage, root diseases and drought conditions. Both the recalcitrance to micropropagation techniques and the long-term process of evaluation and clone recommendation have hampered rapid progress in rubber tree, but nowadays, new research advances have to be considered. The root architecture modelling, genomics and post-genomics approaches, molecular breeding have been integrated to optimize the prediction in genetic improvement programme of several estate crops like oil palm. The integration of biotechnologies for rubber tree improvement must be considered to accelerate the development of rootstock material. That will be decisive for assessing the degree to which new technologies are taken on board in modern rubber growing. The involvement of growers and agro-industrialists. (Résumé d'auteur

Typology of rubber based farming systems in Cameroon: lessons for future plantings

The rubber smallholder sector in Cameroon was developed in different zones, periods and conditions. As a result, the diversity of the rubber farms is important. So, a typology of the farms, mainly based on the strategy for the development of the farming system, is proposed. Four different groups were identified: mini estate farms, family farms with continuous capitalisation of their income in plantations, family farms without capitalisation and emerging rubber family farms. The analysis of the rubber practices during the different stages of a rubber plantation development shows that the four groups present some specificities concerning the choice of the planting material and the strategy of tapping. On the other hand, no difference was noted for the management of the plantation during the immature period. Although the rubber smallholder sector in Cameroon is still limited compared to other African countries, it was possible to reveal that many farmers are interested in rubber. The diagnosis identified some difficulties that smallholders met for rubber cultivation. They have to be taken into consideration for the future plantings. (Résumé d'auteur

Warpage of rubber pressed composites

The rubber pressing process is applied for the rapid production of thermoplastic composite products. However, rubber pressed products show geometrical distortions, such as warpage, due to process-induced residual stresses. It is believed that these stresses build up as a result of the large thermal gradients that are present during consolidation. An experimental study is performed to measure the curvature after rubber pressing of initially flat woven fabric glass/PPS composite panels. A material model is proposed that incorporates the solidification of the composite in order to predict the residual stresses and the warpage due to inhomogenous cooling. The model is employed in Finite Element simulations of the rubber pressing process. The simulations are compared to the experimentally obtained curvatures. It shows that inhomogeneous cooling has a minor effect on the warpage in this case, and that another mechanism is present

Method of Attaching Strain Gauges to Various Materials

A method is provided to bond strain gauges to various materials. First, a tape with an adhesive backing is placed across the inside of the fixture frame. The strain gauge is flatly placed against the adhesive backing and coated with a thin, uniform layer of adhesive. The tape is then removed from the fixture frame and placed, strain gauge side down, on the material to be tested. If the material is a high reluctance material, the induction heating source is placed on the tape. If the material is a low reluctance material, a plate with a ferric side and a rubber side is placed, ferric side down, onto the tape. The induction heating source is then placed upon the rubber side. If the material is an insulator material, a ferric plate is placed on the tape. The induction heating source is then placed on the ferric plate. The inductive heating source then generates frequenty from 60 to 70 kilocycles to inductively heat either low reluctance material, ferric side, of ferric plate and provides incidental pressure of approximately five pounds per square inch to the tape for two minutes, thoroughly curing the adhesive. The induction heating source, and, if necessary, the plate or ferric plate, are then removed from the tape after one minute. The tape is then removed from the bonded strain gauge

Acoustic scattering from a strained region

A composite material consists of a rubber filled with gas-filled microspheres. In underwater applications it is compressed hydrostatically by a pressure that may be not insignificant compared with the shear modulus of the rubber, so large strains are produced around each spherical inclusion. When these spherical inclusions scatter an incident acoustic wave, the strained region around an inclusion has had its elastic properties altered by the large static strain. Thales Underwater Systems asked the Study Group to address the question of how this strained region affects the elastic scattering, bearing in mind that the dynamic shear modulus differs from its static value

Tools for multiaxial validation of behavior laws chosen for modeling hyper-elasticity of rubber-like materials

We present an experimental approach to discriminate hyper-elastic models describing the mechanical behavior of rubber-like materials. An evaluation of the displacement field obtained by digital image correlation allows us to evaluate the heterogeneous strain field observed during these tests. We focus on the particular case of hyper-elastic models to simulate the behavior of some rubber-like materials. Assuming incompressibility of the material, the hyper-elastic potential is determined from tension and compression tests. A biaxial loading condition is obtained in a multiaxial testing machine and model predictions are compared with experimental results