An image processing approach for investigation on transport of iron oxide nanoparticles (FE3O4) stabilized with poly acrylic acid in two-dimensional porous media

Iron oxide nanoparticles were stabilized using poly acrylic acid (PAA) to yield stabilized slurry of Iron oxide nanoparticles. A two-dimensional physical model filled by glass beads was used to study the fate and transport of the iron oxide nanoparticles stabilized with PAA in porous media under saturated, steady-state flow conditions. Transport data for a nonreactive tracer, slurry of iron oxide nanoparticles stabilized with PAA were collected under similar flow conditions. The results show that low concentration slurry of iron oxide nanoparticles stabilized with PAA can be transported like a tracer without significant retardation. The image processing technique was employed to measure the tracer/nanoparticle concentration inside the 2-D model filled with glass beads. The groundwater flow model, Visual MODFLOW, was used to model the observed transport patterns through MT3DMS module. Finally, it was demonstrated that the numerical model MODFLOW can be used to predict the fate and transport characteristics of nanoparticles stabilized with PAA in groundwater aquifers.

Improved Spinnability of Metallocene Polyethylenes by Using Processing Aids

Melt spinning is a polymer processing technique that is strongly influenced by the extensional flow behaviour of polymer melts. Therefore only a few polymeric materials are usable for this kind of processing with sufficient take-up speeds. When approaching critical conditions of deformation most polymers show either fibre break in the molten state either by a brittle cohesive rupture or a ductile failure. During the melt spinning of pure and modified metallocene poylethylenes additional flow instabilities occur within the spinning die. Namely, wall slip, ‘sharkskin’ and pressure oscillations (gross fracture) may be obtained dependending on the volume flow rate. Pressure oscillations lead to diameter oscillations of the melt extrudate, which create local increase of tensile stress in the spin line. This effect immediately causes fiber break in the spinline.

Therefore, melt spinning of polyethylenes was only possible up to a critical molecular weight or its relating melt viscosity. The limitation of the molecular weight restricts the mechanical properties of the melt spun fibres. This paper reports on an attempt to find out appropriate processing aids for suppressing ‘sharkskin’ effects and pressure oscillations in an attempt to overcome the limitation of a critical molecular weight. At first, the critical conditions for the onset of flow instabilities for higher molecular weight polymers were analysed. Further experiments concerned with the use of processing aids for melt spinning of metallocene polyethylenes of higher molecular weights. A combination of boron nitride powder and a fluoroelastomer was found to be an effective processing aid for this process.

Extrusion Foam Coating of Coaxial Cables using Butane as Physical Blowing Agent

This paper presents an experimental study on manufacture and characterization of an insulating foam coating in the coaxial cables where a physical blowing agent (butane) is used. Coaxial cables with foam insulator are widely used in communication industries. The insulating foam plays a key role in the attenuation properties of the coaxial cables. In this research work, an extrusion setup was prepared to produce foam insulated coaxial cable using butane as the physical foaming agent. The effect of die geometry (die gap and die outlet diameter) on foam morphology and loss-attenuation were investigated using a blend of LDPE (90%)-HDPE (10%) as the main material. The results show that an acceptable low loss-attenuation is achievable via using a polyethylene compound and adjusting processing parameters.