Flexible,lead-free,gamma-shielding materials based on natural rubber/metal oxide composites

Properties such as gamma shielding, cure characteristics, and mechanical properties of natural rubber (NR) system with addition of oxides such as: iron (II, III) oxide (Fe₃O₄), tungsten (III) oxide (W₂O₃), or bismuth (III) oxide (Bi₂O₃) were studied for potential replacement of flexible lead (Pb), and introduced as gamma-shielding materials, to minimize risks caused by Pb. The results showed that increase in the content of oxides such as Fe₃O₄, W₂O₃, or Bi₂O₃ from 0 to 100, 300, and 500 parts/100 parts of rubber by weight (phr) increased the gamma attenuation coefficients, tensile modulus at 100% elongation, and hardness (Shore A), though they reduced the tensile strength and elongation-at-break. The composites also underwent thermal aging tests at 70 °C for 96 h. The results indicated slight reduction in the overall tensile properties. Specifically, for NR composites with 300 or 500 phr of Bi₂O₃, the mass attenuation coefficients (μ _m) of these composites were the highest among other composites and even higher than lead sheets that were measured using the same set-up. The outcome of the results imply great possibilities of replacing hazardous lead-containing gamma-shielding materials with the investigated composites, while still providing safe and efficient gamma-shielding properties for the users.     

ABS modified with hydrogenated polystyrene‐grafted‐natural rubber

Natural rubber (NR) latex was grafted by emulsion polymerization with styrene monomer, using cumene hydroperoxide/tetraethylene pentamene as redox initiator system. The polystyrene‐grafted NR (PS‐g‐NR) was hydrogenated by diimide reduction in the latex form using hydrazine and hydrogen peroxide with boric acid as a promoter. At the optimum condition for graft copolymerization, a grafting efficiency of 81.5% was obtained. In addition, the highest hydrogenation level of 47.2% was achieved using a hydrazine:hydrogen peroxide molar ratio of 1:1.1. Hydrogenation of the PS‐g‐NR (H(PS‐g‐NR)) increased the thermal stability. Transmission electron microscopy analysis of the H(PS‐g‐NR) particles revealed a nonhydrogenated rubber core and hydrogenated outer rubber layer, in accordance with the layer model. The addition of H(PS‐g‐NR) at 10 wt % as modifier in an acrylonitrile–butadiene–styrene (ABS) copolymer increased the tensile and impact strengths and the thermal resistance of the ABS blends, and to a greater extent than that provided by blending with NR or PS‐g‐NR. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Treatment of effluents from textile-rinsing operations by thermally stable nanofiltration membranes

Thermally stable nanofiltration membranes were used to recover hot water from rinsing effluents from acid and reactive dyeing operations. Two types of flat-sheet membranes, MPF-34 (MWCO 200) and MPF-36 (MWCO 1000), were tested at 60°C and 10 bar. Experiments carried out with the made-up feeds containing acid dye and acetic acid showed that both membranes were able to retain more than 99% of dye. MPF-36 suffered from substantial flux decline due to the dye and acid in the feeds but still provided higher fluxes than MPF-34. Furthermore, reactive dye rejection of MPF-36 was acceptable, ranging from 97 to 99.5%, while the fluxes, 105-140 1/m².h, were exceptionally high. MPF-36 was then further tested with the wastewater from industrial processes. The membrane could recover hot water by removing more than 98% of acid dye and 90% of reactive dyes. Despite severe fouling by acid dye, the membrane was still able to provide 40-50 1/m².h of permeate fluxes. For the reactive dye rinsing effluents, remarkably high fluxes of 120-1501/m2.h were obtained. Chemical cleaning of the used membrane with 0.2% wt. HNO₃ and subsequently 0.5% wt. NaOH recovered 80-100% of the flux.