Dynamic of rubber production in Northeast Thailand: A case study at Subsomboon village, Doonsard sub-district, Kranuan district, Khon Kaen province

This research aim to study changes in rubber production and farmers' practices at Subsomboon village, Doonsard sub-district, Kranuan district, Khon Kaen province since the promotion of rubber plantation. Data were collected by using literature review, semi-structured interview (SSI) with Key-informants (KIs) using sub-topics and interviewing with a sample of 30 accessible rubber farmers using a closed ended questionnaire. It was found that rubber production in the area could be divided into 3 periods including the first period: Beginning of rubber cultivation (1992-2003) farmers started rubber plantation with government support for the production inputs and knowledge, the second period: Rubber booming (2004-2011) where the area of rubber dramatically increased mostly by farmer' s own investment and partly supported by the government and the third period: Declining of rubber (2012-present), when limited expansion of new rubber area was farmers own investment and no rubber replanting in some farms. Moreover, the study found that there are different practices among farmers at each period showing the adaptation of farmers in their plots according to the situation of family condition and rubber production in each period

Structural and physico-mechanical properties of natural rubber/GTR composites devulcanized by microwaves: influence of GTR source and irradiation time

Ground tire rubber from car and truck was modified using microwave irradiation at variable time. The irradiated ground tire rubber was used as filler in composites based on natural rubber. The composites, with high content of ground tire rubber, were prepared using an internal batch mixer and subsequently cross-linked at 160¿. The influence of the ground tire rubber source (car/truck) and irradiation time on structure, physico-mechanical behaviour, thermal properties and morphology of natural rubber/ground tire rubber composites was studied. The interfacial interactions between ground tire rubber and natural rubber as function of ground tire rubber source and irradiation time were evaluated by Fourier transform infrared spectroscopy, thermogravimetric analysis, tensile tests, swelling measurements and scanning electron microscopy. The results showed that irradiation of ground tire rubber slightly enhanced tensile properties and cross-link density of natural rubber/ground tire rubber composites. This effect was more evident in the case of ground tire rubbertruck because of its higher content of natural rubber and was reflected in changes in the interfacial adhesion, which were confirmed by the results of Fourier transform infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy analysisPostprint (author's final draft

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

Laboratory Tests Of Waste Mixtures Consisting Recycled Tyre Rubber and Coal-Mining Wastes

The paper presents the results of research on the application of recycled tyre rubber, in the form of rubber dust, in mixtures bound with a hydraulic binder, to improve the physical and mechanical parameters of unburnt coalmining slates. In particular, the parameters related to resistance to water and susceptibility of bound mixtures. The research was carried out on mixtures containing unburnt coal-mining slate, rubber dust, fly ash and cement, as well as on reference mixtures with no rubber dust in their composition. The observations were aimed at checking how the varied content of rubber dust affects the physical and mechanical parameters of the samples

Toxicity of Pyrolysis Gases from Elastomers

The toxicity of the pyrolysis gases from six elastomers was investigated. The elastomers were polyisoprene (natural rubber), styrene-butadiene rubber (SBR), ethylene propylene diene terpolymer (EPDM), acrylonitrile rubber, chlorosulfonated polyethylene rubber, and polychloroprene. The rising temperature and fixed temperature programs produced exactly the same rank order of materials based on time to death. Acryltonitrile rubber exhibited the greatest toxicity under these test conditions; carbon monoxide was not found in sufficient concentrations to be the primary cause of death

Fertilizer application on immature rubber. The case of clone PB 330 in Tboung Khmum Province, Cambodia

Fertilization is one of the most important factors that affect growth and yield of rubber tree. It takes a high rate of capital investment for plantation. Regulation on fertilizer quantity or/and ratio among fertilizer nutrients results in remarkable economical and technical impacts on the rubber plantation during the immature period. During the mature period, data are still controversial. This experimental study aimed to evaluate the effects of fertilizer on the rubber growth in immature stage. After seven years of experimentation, results showed that fertilization had a positive effect on the cumulative girth increment (cm) by 6% whereas the tapped rubber trees at opening increased by 7 to 13%

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

Rubber friction on smooth surfaces

We study the sliding friction for viscoelastic solids, e.g., rubber, on hard flat substrate surfaces. We consider first the fluctuating shear stress inside a viscoelastic solid which results from the thermal motion of the atoms or molecules in the solid. At the nanoscale the thermal fluctuations are very strong and give rise to stress fluctuations in the MPa-range, which is similar to the depinning stresses which typically occur at solid-rubber interfaces, indicating the crucial importance of thermal fluctuations for rubber friction on smooth surfaces. We develop a detailed model which takes into account the influence of thermal fluctuations on the depinning of small contact patches (stress domains) at the rubber-substrate interface. The theory predicts that the velocity dependence of the macroscopic shear stress has a bell-shaped f orm, and that the low-velocity side exhibits the same temperature dependence as the bulk viscoelastic modulus, in qualitative agreement with experimental data. Finally, we discuss the influence of small-amplitude substrate roughness on rubber sliding friction.Comment: 14 pages, 16 figure