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

Rubber plantation labor and labor movements as rubber prices decrease in southern Thailand

A decrease in rubber prices can initiate labor migration trends from rubber production to industrial or service sectors, which could further cause labor shortages in rubber production. This case was not studied in the different communities with a long history of rubber such as the center city of southern Thailand. This study analyzes the source of labor and movement of laborers working in rubber plantations in the context of decreasing rubber prices. We selected 3 representative areas, namely rural, suburban and urban communities in Hat Yai district, Songkhla province. Owners of rubber holdings were the target group for the survey, and individual interviews were conducted. We collected data between March and July 2015, engaging with 207 owners. The results showed that family labor and hired labor were widely used in rubber plantations in the three communities. Locally hired laborers and laborers from other countries were the main sources of hired labor for rubber plantations. The transnational laborers were a secondary source of labor for all communities, especially the rural ones. Family labor was the main source of labor for smallholder rubber plots, especially for the urban and suburban areas. Hired labor was used in all sizes of rubber holding in rural and suburban communities and were very common in the small rubber holdings in urban areas. This shows that the rubber production sector creates employment for local people and for migrants. Furthermore, low rubber price conditions did not significantly impact labor movement in rubber plantations. However, rubber plantations in urban and suburban communities lacked labor supply due to their proximity to the larger urban center of Hat Yai city. Therefore, the low tapping intensity and generate the diversified source of income to attract young labor generation to work on the farms should be policy to maintain natural rubber production in Thailand

Rubber friction on (apparently) smooth lubricated surfaces

We study rubber sliding friction on hard lubricated surfaces. We show that even if the hard surface appears smooth to the naked eye, it may exhibit short wavelength roughness, which may give the dominant contribution to rubber friction. That is, the observed sliding friction is mainly due to the viscoelastic deformations of the rubber by the substrate surface asperities. The presented results are of great importance for rubber sealing and other rubber applications involving (apparently) smooth surfaces.Comment: 7 pages, 15 figure

Toughness, Tenacity and Maximum Initial Strength of Rubber Modified Asphalt Binders

The toughness and tenacity test method, which was developed in the 1980s, is popular for evaluating a polymermodified binder. Several states like Nevada require performing this test to evaluate non-modified binder samples, as well as other types of modified binders. In this regard, a toughness and tenacity test was performed on rubber-modified samples produced from virgin binder PG58-28, PG64-16 and AC-20. In order to take the rubber size, type and content into account, two rubber sizes, mesh #20 and #40, two rubber types, ambient and cryogenic, and three rubber contents, 10%, 15%, and 20% were produced and tested. The results then were compared with polymer-modified and terminally blended rubber-modified samples. The results show improvement in the amount of initial maximum strength, and a decline in the magnitude of elongation, toughness and tenacity for the rubber-modified binder, compared to other types of binders

Impact behaviour of nylon-rubber blends: 6. Influence of structure on voiding processes; toughening mechanism

Dilatometry tests were performed on nylon-rubber blends with various rubber concentrations, particle sizes and types of impact modifier. Whereas rubber concentration and particle size do not affect the onset of voiding in the blends during a tensile test, the type of elastomer used has a considerable effect. A correlation exists between the stress at which the rubber particles cavitate (or detach from the matrix) in the tensile test and the impact behaviour of the blend. A toughening mechanism is proposed in which the cavitation stress of the rubber and the interparticle spacing play crucial roles

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

Reinforcement of natural rubber by precipitated silica: the influence of processing temperature

The thermal history and in particular the mixing dump temperature is a parameter of paramount importance in mixing rubber and silica with a silane coupling agent in order to achieve proper silanization of silica and to avoid premature scorch reactions. In this work, the influence of mixing dump temperature on the performance of silica reinforced Natural Rubber (NR) is investigated. The investigation also includes the effect of non-rubber constituents, primarily proteins in NR, by using deproteinized Natural Rubber (DPNR) and synthetic polyisoprene (IR). The vulcanization properties and rubber-to-filler interactions of silica reinforced NR in presence and absence of a silane coupling agent are highlighted. With increasing mixing dump temperature, the silanization reaction between silica and silane coupling agent proceeds further. At sufficiently high dump temperature, filler-filler interactions in the NR-silica compounds are reduced and silica-rubber interaction improved as evidenced by a drop in the Payne effect and increment in chemically bound rubber. It is demonstrated that NR and IR compounds mixed till above the optimum dump temperature exhibit cure reversion and reduction in tensile properties. On the other hand, DPNR-silica vulcanizates show slightly more constant physical properties