Arsenic species in an arsenic hyperaccumulating fern, Pityrogramma calomelanos: a potential phytoremediator of arsenic-contaminated soils

The fern Pityrogramma calomelanos is a hyperaccumulator of arsenic that grows readily on arsenic-contaminated soils in the Ron Phibun district of southern Thailand. P. calomelanos accumulates arsenic mostly in the fronds (up to 8350 microg As g(-1) dry mass) while the rhizoids contain the lowest concentrations of arsenic (88-310 microg As g(-1) dry mass). The arsenic species in aqueous extracts of the fern and soil were determined by high performance liquid chromatography coupled to an inductively coupled plasma mass spectrometer (HPLC-ICPMS) which served as an arsenic specific detector. Only a small part of the arsenic (6.1-12%) in soil was extracted into water, and most of this arsenic (> 97%) was present as arsenate. The arsenic in the fern rhizoids was approximately 60% water-extractable, 95% of which was present as arsenate. In contrast, arsenic in the fern fronds was readily extracted into water (86-93%) and was present mainly as arsenite (60-72%) with the remainder being arsenate. Methylarsonate and dimethylarsinate were detected as trace constituents in only two fern samples. Preliminary estimates of phytoremediation potential suggest that P. calomelanos might remove approximately 2% of the soil arsenic load per year. With due consideration to the type of arsenic compounds present in the fern, and their water-solubility, the option of disposing high arsenic ferns at sea is raised for discussion.     

Pineapple leaf fibers (PALF) as the sustainable carbon anode material for lithium-ion batteries

Journal of Materials Science: Materials in Electronics - Pineapple leaf fiber (PALF) is considered as a promising low cost carbon precursor to produce a high graphitic carbon material, regarding to...     

Irradiation of highly oriented polyethylene fibers in the atmosphere of some vinyl monomers: Effect on compressive strength

Highly oriented polyethylene fibers have been modified by γ‐irradiation in the presence of some vinyl monomer vapors, followed with further annealing in the atmosphere of the same monomer. Two types of vinyl monomers that are known to produce polymers with different glass transition temperatures, namely methyl methacrylate and vinyl acetate, were studied for their effect on the compressive strength of the fiber. It was found that a significant improvement in compressive strength, measured by tensile recoil test, was obtained. The level of improvement was affected by heat treatment and the presence of monomer during irradiation. Modification with vinyl acetate was found to be more effective than methyl methacrylate. These facts suggest that the improvement in compressive strength was attributable to several factors, including structural relaxation, the presence of graft copolymer, and energy dissipation ability of the graft copolymer. It is speculated that lateral integrity of the fiber is one of the key factors that prevents sliding of microfibril and possibly lateral or circumferential expansion of the fiber to accommodate kink band. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2494–2502, 2001     

Thermal decomposition behavior and mechanical properties of elastomeric composites based on polyolefinic thermoplastic elastomer and organomontmorillonite

The elastomeric composites based on organomontmorillonite (OMMT) and Santoprene thermoplastic elastomer were prepared by melt processing. Maleic anhydride grafted polypropylene (PP-g-MA) was used as a compatibilizer for the composite system. By adding optimum content of PP-g-MA, the fracture surface of the composites observed by SEM was smoothened as a result from compatibilizing effect. From XRD results, the measured d-spacing data proved a good dispersion of nanoclay along with compatibilizer. Thermal decomposition behavior of the neat components and its composites obtained from simultaneous TG and DSC profiles indicated that the incorporation of OMMT into the matrix polymer improved the thermal stability in air but not in nitrogen. No significant change in thermal stability of the composites with addition of PP-g-MA. The incorporation of clay significantly enhanced in dynamic mechanical and tensile properties of the composites. The dynamic storage modulus, tensile modulus and yield stress of the composites with the presence of PP-g-MA were remarkably improved.     

The preparation and antimicrobial effect of AgZrP/nylon 6,10 fibers used as dental hygiene materials

Silver zirconium phosphate (AgZrP) was incorporated into nylon 6,10 fibers by using a twin screw extruder to produce antimicrobial fibers. Monofilament fibers with various degrees of AgZrP loading were prepared by the melt‐spinning process. The surface concentration of AgZrP particles was found to be dependent on AgZrP loading. A poor interface between AgZrP and the polymeric matrix was observed, however, it did not affect the drawn process. The presence of AgZrP particles did not disturb the structure and slightly effected to the mechanical properties of the nylon fiber. The fiber with the highest draw ratio showed the highest degree of polymer chain orientation, a higher tensile strength and a higher modulus. The antimicrobial effect started when the silver ion concentration was high enough, The AgZrP fiber showed the highest antimicrobial effect on S. mutans, L. Casei, S. aureus, and C. albicans at 10, 15, 10, and 15%, respectively. The AgZrP fibers showed the significant antimicrobial effect on three strains of microorganisms except S. aureus. Antimicrobial activities of AgZrP were demonstrated and the results showed that AgZrP incorporated into the matrix of nylon 6,10 fibers can improve their antimicrobial property. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

The relation between filament diameter and fracture strength for ultra-high-modulus polyethylene fibres

The effect of filament diameter on the failure stress of polyethylene fibres has been studied using Weibull analysis. Both gel-spun and melt-spun fibres have been examined, so that differences might be observed for changes in draw ratio or modulus as well as molecular weight. It is concluded that the strength of high-modulus melt-spun fibres relates to the concentration of flaws and is significantly dependent on filament diameter. Conflicting results for gel-spun fibres are discussed in the light of the present investigation, and it is concluded that the mechanism of failure in these fibres is different from that of the melt-spun fibres.     

Fiber–matrix interactions in aramid‐short‐fiber‐reinforced thermoplastic polyurethane composites

The mechanical and dynamic mechanical properties of thermoplastic polyurethane (TPU) elastomers reinforced with two types of aramid short fibers, m‐aramid (Teijin‐Conex) and copoly(p‐aramid) (Technora), were investigated in this study with respect to the fiber loading. In general, both types of composites exhibited very similar stress–strain behaviors, except that Technora–TPU was stronger than Conex–TPU. This was primarily due to the intrinsic strength of the reinforcing fibers. Both types of fibers reinforced TPU effectively without any surface treatment. This could be attributed to good fiber–matrix interactions, which were revealed by the broadening of the tan δ peak in dynamic mechanical analysis. Furthermore, the morphologies of cryogenically fractured surfaces of the composites and extracted fibers, investigated with scanning electron microscopy, revealed possible polar–polar interactions between the aramid fibers and TPU matrices. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1059–1067, 2003     

Isothermal decomposition behavior and dynamic mechanical properties of in situ‐reinforcing elastomer composites based on thermoplastic elastomers and thermotropic liquid crystalline polymer

In situ‐reinforcing composites based on two elastomer matrices very different in melt viscosity, styrene–(ethylene butylene)–styrene triblock copolymer (Kraton G1650), and styrene–(ethylene propylene) diblock copolymer (Kraton G1701), and a thermotropic liquid crystalline polymer (TLCP), Rodrun LC3000, were prepared using a twin‐screw extruder. The isothermal decomposition behavior and dynamic mechanical properties of the extruded strands were investigated by means of thermogravimetry (TG) and dynamic mechanical analysis (DMA), respectively. No significant change in the shape of TG curves for the neat matrices and their LC3000‐containing blends was observed under isothermal heating in nitrogen. In air, G1650 and G1701 showed a single weight‐loss stage and rapid decomposition whereas their blends with 30 wt % LC3000 showed different profiles of weight loss depending on isothermal temperatures. The calculated kinetic parameters indicated that the thermal stability of the polymers is much higher in nitrogen than in air and suggested an enhancement of thermal resistance of the elastomer matrices by addition of TLCP. DMA results showed a great enhancement in dynamic moduli for the blend with 10 wt % LC3000 when compared with the neat matrix. The tan δ peaks corresponding to the elastic and hard phases in both matrices mostly shifted to the lower temperature with LC3000 loading. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 917–927, 2007