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[en] A volatile organic compound (VOC) transport model has been developed to describe unsteady-state VOC permeation and diffusion within a waste drum. Model equations account for three primary mechanisms for VOC transport from a void volume within the drum. These mechanisms are VOC permeation across a polymer boundary, VOC diffusion across an opening in a volume boundary, and VOC solubilization in a polymer boundary. A series of lab-scale experiments was performed in which the VOC concentration was measured in simulated waste drums under different conditions. A lab-scale simulated waste drum consisted of a sized-down 55-gal metal drum containing a modified rigid polyethylene drum liner. Four polyethylene bags were sealed inside a large polyethylene bag, supported by a wire cage, and placed inside the drum liner. The small bags were filled with VOC-air gas mixture and the VOC concentration was measured throughout the drum over a period of time. Test variables included the type of VOC-air gas mixtures introduced into the small bags, the small bag closure type, and the presence or absence of a variable external heat source. Model results were calculated for those trials where the VOC permeability had been measured. Permeabilities for five VOCs [methylene chloride, 1,1,2-trichloro-1,2,2-trifluoroethane (Freon-113), 1,1,1-trichloroethane, carbon tetrachloride, and trichloroethylene] were measured across a polyethylene bag. Comparison of model and experimental results of VOC concentration as a function of time indicate that model accurately accounts for significant VOC transport mechanisms in a lab-scale waste drum
[en] The dose dependences of break stress of polymer materials and its specific lengthening at breakage of polymer materials were calculated within frames of model of free jointed chain with using of cascade-probably method. According of experimental data one can judge about polymer radiation stability and give recommendation on its use at electrotechnical machines and apparatus contraction using under ionization radiation
[en] The dose effect on the viscosimetric molecular average weight (Mv) of isostatic national polypropylene irradiated by gamma rays shows the occurrence of main chain scission up to 60 kGy and crosslinking between 60 kGy and 150 kGy. (author). 7 refs., 2 figs
[en] Charge packet has been observed on many occasions but its physical mechanisms have never been properly understood. One of the models proposed by Lewis et al shows the presence of negative differential mobility with an electric field in semicrystalline polyethylene. In this paper we have observed the negative differential mobility using the transient space charge profile measured by the pulsed electroacoustic technique. By superimposing a short pulse voltage to a dc voltage, it is possible to obtain the velocity of holes at different applied fields. To the best of our knowledge we have for the first time observed negative differential mobility in polyethylene. This observation provides crucial evidence to support Lewis's model and allows one to simulate charge packet and its behaviours. (fast track communication)
[en] Highlights: • A new process to produce flax/PP tape for AFP is described, using calendering between rollers. • Microstructure analysis shows surface polymer and good impregnation. • AFP forming process allows manufacture of temperature sensitive natural fibres. • Mechanical properties comparable to those for compression moulded plate specimens. Automated fibre placement (AFP) has been used to manufacture flax/polypropylene biocomposites for the first time. This required preparation of tape with a calibrated width from impregnated fibre sheets. The unidirectional tapes showed polymer-rich zones on the surface. During manufacture the polypropylene (PP) is melted locally with a laser. A consolidation step in a hot press is then required to reduce void content. The flax fibres, composed of polysaccharides, have limited thermal resistance so optimization of the thermal cycle is necessary, but subsequent characterization of mechanical behaviour showed no evidence of property loss in spite of an additional melting cycle. AFP appears to be a promising manufacturing method for biocomposites.
[en] The present theoretical approach to rubberlike elasticity is novel in that it utilizes the wealth of information which rotational isomeric state theory provides on the spatial configurations of chain molecules. Specifically, Monte Carlo calculations based on the rotational isomeric state approximation are used to simulate spatial configurations, and thus distribution functions for the end-to-end separation r of the chains. Results are presented for polyethylene (PE) [CH-2] and polydimethylsiloxane (PDMS) [Si(CH3)2--O--] chains most of which are quite short, in order to elucidate non-Gaussian effects due to limited chain extensibility. Large values of r were found to be more prevalent in PDMS than in PE, primarily because of the unusually large Si--O--Si bond angle in the PDMS chain, which increases its spatial extension. The use of these distribution functions in place of the Gaussian function for network chains gives upturns in modulus at high elongations, because of the rapidly diminishing number of configurations consistent with the required large values of r, and thus, correspondingly large decreases in the entropy of the network chains. Networks of PDMS should have values of the non-Gaussian increases in modulus significantly different from those for (amorphous) PE networks having the same number of skeletal bonds and stretched to the same relative length
[en] The intensity I3 of ortho-positronium (o-Ps) in a polymer blend system consisting of polyethylene (PE) and ethylene-vinylacetate (EVA, random copolymer with a vinylacetate content of about 14%) was measured as functions of EVA weight content (PHI=0-100%), electric field (E=0-60 kV/cm ), positron irradiation time (t=0-200 h) and temperature (T=100-300 K). It was found that the addition of small amounts of EVA to PE significantly alters the electric field, positron irradiation time and temperature dependence of I3. Positron trapping on polar EVA is suggested to be responsible for the sensitive effects of EVA.
[en] Full text.The present work concerns the rheological properties of binary blends obtained from wastes of PEhd and PS at the molton state. Data obtained in capillary rheometer are presented to describe the effects of blending ratio, shear stress and shear rate on the flow properties, melt viscosity and melt elasticity. For the blend composition corresponding to 20-40% PEhd content, the binary blends show a maximum in the value of melt viscosity accompanied by a minimum in melt elasticity. the variation of melt flow index as function of the composition of the blends indicate two deviations compared to the curve of ideal blend
[en] The subject of this paper is the use of a Cut-off Wall System (CWS) in conjunction with conventional soil bentonite slurry walls. The system is a vertical subsurface containment solution for isolating contaminated soils and groundwater in situ, thereby enhancing protection of the environment. The CWS is composed of geomembrane panels and specially designed connectors that form an interlocking subsurface vertical barrier wall. This system provides a cost effective, easily installed, positive cut-off for isolation of mixed and hazardous wastes, and wastes from uncontrolled releases. This application will address manufacturing, fabrication, installation, strength, QA/QC, chemical compatibility, and permeability