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Leather tanning processes cause environmental impact as a result of the generation of solid waste, wastewater, and release of gases. The improper disposal of such waste may promote the oxidation of chromium, for example, changing it from chromium (III) to chromium (VI), in which becomes extremely toxic. In this study, composites were prepared from natural rubber (NR) with industrial leather waste (Lw), varying the waste amount from 20 to 80 phr, with the aim of recycling leather waste. The microstructure, mechanical properties and rheological properties of composites were investigated. The results showed that Lw increased tensile strength and hardness, with good reproducibility, and uniformity of residuals distributed as fillers (miscible materials). These properties indicate that this composite material can be used as raw material for the manufacture of shoes, bags, upholstery, etc. POLYM. COMPOS., 36:2275–2281, 2015. © 2014 Society of Plastics Engineers

This paper investigated the formation of crosslinks in natural rubber compounds in the vulcanization systems: conventional (CV), semi-efficient (SEV), and efficient (EV), processed with three types of accelerators: MBTS (dibenzothiazole disulfide), TMTD (tetramethylthiuram disulfide) and CBS (n-cyclohexyl 2-benzothiazole sulfenamide). The cross-linked densities were determined by organic solvent swelling, dynamic mechanical analysis (DMA), stress vs strain, and low-field nuclear magnetic resonance, the latter being the reference technique for comparison with the other results. It was found that the choice of accelerator type influences the processing time and the cross-linked density of the vulcanizate. The four techniques showed close values of cross-linked density for natural rubber compounds, demonstrating that the analytical techniques studied can be applied to determine crosslinked density.

Waste recycling has been the subject of numerous scientific researches regarding the environmental care. This paper reports the redirecting of sugarcane bagasse ash (SBA) as new filler to natural rubber (NR/SBA). The NR/ SBA composites were prepared using an opened cylinder mixer to incorporate the vulcanization agents and different proportions of residue (SBA). The ash contains about 70-90% of inorganic compounds, with silica (SiO 2 ) being the main compound. The SBA incorporation improved the mechanical properties of the vulcanized rubber. Based on these results, a new use is proposed for the agro-industry organic waste to be implemented in the rubber vulcanization process, aimed at improving the rubber physical properties as well as decreasing the prices of natural rubber composites.

Biocomposites based on natural rubber (NR) reinforced with 45S5 BioglassÒ (BG) particles were obtained by casting/evaporation method in which NR was dissolved in chloroform and mixed with BG particles. Structural, mechanical, and thermal tests were performed on the biocomposites to evaluate the influence of BG particles on the properties of the NR matrix. Thermogravimetric tests (TG/DTG) of the biocomposites showed decomposition profiles similar to that of NR, and the main peak of the DTG curve was well defined in the temperature range 300-450°C, characteristic of the structural degradation of NR. The TG analysis also revealed that the thermal stability of the samples increases with the increasing quantity of BG in the biocomposite. DMA tests showed higher storage modulus (E 0) values for samples with larger amounts of BG; however, above the T g , the E 0 value tended to zero due to the increased mobility of the polymer chains. By analyzing tan d, the T g values were calculated to be-46 and-50°C for NR and the biocomposite samples, respectively. Mechanical testing demonstrated that the addition of BG to the biocomposite improved the mechanical properties of the samples. The samples became more rigid with the increasing quantity of BG, as demonstrated by decreasing deformation and the increasing elastic modulus (Y) and breaking strength of the samples. The BG particles positively affected the mechanical and thermal properties of the biocomposite, allowing its use in biomedical applications.

necessarily the chromium contained in these residues influences the toxicity and genotoxicity of this new material.

Green chemistry is an innovative way to approach the synthesis of metallic nanostructures employing eco-friendly substances (natural compounds) acting as reducing agents. Usually, slow kinetics are expected due to, use of microbiological materials. In this report we study composites of natural rubber (NR) membranes fabricated using latex fromHevea brasiliensistrees (RRIM 600) that works as reducing agent for the synthesis of gold nanoparticles. A straight and clean method is presented, to produce gold nanoparticles (AuNP) in a flexible substrate or in solution, without the use of chemical reducing reagents, and at the same time providing good size’s homogeneity, reproducibility, and stability of the composites.

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