Commercial Polycarbonate Research Articles

Carbon nanotube hollow fiber membranes: High-throughput fabrication, structural control and electrochemically improved selectivity

A simple approach to high-throughput fabrication of length-unlimited, neat carbon nanotube (CNT) hollow fiber membranes based on wet-spinning technology is presented. The prepared CNT membranes exhibit uniform hollow fiber configuration, good electrical conductivity and controllable attributes (for example, thicknesses, structures and pore sizes). Specifically, the CNT hollow fiber membranes with three-dimensional macroporous structure in their cross sections can support a water flux of 12000±1500Lm−2h−1bar−1 which is 6 times higher than that of polymeric membranes with the similar pore size of about 100nm, 10 times and 2 times higher than that of commercial Al2O3 ceramic membranes (pore size of 1000nm) and polycarbonate membranes (pore size of 200nm), respectively. Experimental measurements indicate their ultrahigh porosity of 95±3% and hydrophilicity derived from H2SO4/HNO3 treatment of CNTs for well dispersion in solvent mainly account for the high permeability. Benefiting from their good electrical conductivity, the CNT membranes demonstrate the interesting electricity-induced improved selectivity (rejection ability) for nanoparticles, which is mainly attributed to the electrostatic interaction, preventing their penetrating the CNT membranes. The distinctive function of CNT membranes is highly expected to contribute to various important areas of application, such as water purification and biomolecule separation.

Facile electrochemical synthesis, using microemulsions with ionic liquid, of highly mesoporous CoPt nanorods with enhanced electrocatalytic performance for clean energy

We have established a facile and generalizable electrochemical synthesis of metallic mesoporous nanorods in the nanochannels of commercial polycarbonate membranes using microemulsions containing ionic liquids. Herein, we report the preparation of magnetic CoPt nanorods with various meso or nanopores distributions, depending on the microemulsion type (ionic liquid –in-water (IL/W), bicontinuous (β) or water-in-ionic liquid (W/IL)). The synthesized porous nanorods show a much enhanced electrocatalytic activity for methanol oxidation in comparison with compact Pt nanorods (up to 12 times) or Pt/C electrocatalyst (Pt nanoparticles or commercial black platinum). Therefore, the synthesized CoPt mesoporous nanorods could be excellent catalysts in direct methanol fuel cells (DMFC's), as they have high surface areas, large pore volumes and high corrosion stability, and they exhibit promising catalytic properties.

Modifying the luminescence characteristics of Lu2O3:Eu large nanocrystals with polycarbonate host

Lu2O3:Eu phosphor fine powder with average size of crystallites of about 100–150 nm was synthesized. TEM images proved only an insignificant agglomeration of the phosphor. Using these fine particles and commercial polycarbonate a composite material was prepared in a form of 2 mm thick plate and its spectroscopic properties were compared to the powder. While the emission and luminescence excitation spectra were found very similar in both types of materials, the decay times of the Eu3+ red luminescence appeared to drop from 1.8–2 ms for the powder to 0.9–1 ms for the composite, with the latter value being perfectly the same as for the coarse‐grained sintered translucent ceramics. Since the refractive indices of Lu2O3 host and the polycarbonate are 1.935 and 1.582, respectively, such a drastic change in the Eu3+ emission kinetics could not be fully explained by the variations of this parameter only. This result is with some disagreement with previously published data. POLYM. COMPOS., 37:1330–1334, 2016. © 2014 Society of Plastics Engineers

Mechanical Behavior of Polycarbonate Fabricated at Different Cooling Speeds

This comparative study investigates the mechanical properties of polycarbonate in manufacturing conditions of different cooling speed. All experiments were conducted using 0.8 mm thick specimens made of commercial Polycarbonate granule (3 mm), according to the ASTM standard. The test results illustrate that polycarbonate specimens manufactured in fast-cooling (FC) condition exhibit at least five times higher resilience in ambient temperature than those of slow-cooling (SC) condition. However, the resilience of FC polycarbonate specimen quickly deteriorates, as the test temperature reduces to negative 40 degrees C. On the other hand, SC specimens barely changed their tensile properties. Thus, the test reveals that tensile properties of polycarbonate are significantly affected by the cooling speed in the manufacturing stage, and exposed temperature conditions. In this manuscript, the correlations between toughness and yield strength of polycarbonate specimen are summarized and discussed in terms of the cooling conditions and environmental temperature.

Synthesis of Silicon and Germanium Nanowire Assemblies by Template-Assisted Electrodeposition from an Ionic Liquid

We report on the template-assisted synthesis of silicon and germanium nanowires from the air- and water-stable ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([Py1,4] TFSA). The synthesis was done by electrochemical deposition in the pores of a commercial track-etched polycarbonate membrane. After chemical dissolution of the polycarbonate membrane in dichloromethane, nanowire assemblies with a regular arrangement were obtained. Different lengths of nanowires can be obtained by varying the applied potential and the time of deposition. The nanowire assemblies were characterised by scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDX). Our results show that the template-assisted electrochemical deposition approach in ionic liquids has the potential to easily synthesise germanium and silicon nanowire assemblies.

A strategy to achieve high electromagnetic interference shielding and ultra low percolation in multiwall carbon nanotube–polycarbonate composites through selective localization of carbon nanotubes

Here, we report a simple method that involves solution blending of polycarbonate (PC) in the presence of multiwall carbon nanotubes (MWCNTs) and commercial PC beads for the preparation of electrically conducting MWCNT–PC composites with high electromagnetic interference shielding effectiveness (EMI SE) and electrical conductivity at very low (∼0.021 wt%) percolation threshold (pc). Thus, electrical conductivity of ∼4.57 × 10−3 S cm−1 was achieved in the MWCNT–PC composites at an extremely low MWCNT loading (0.10 wt%) in the presence of 70 wt% PC beads in the composites. Finally, optimizing the ratio of PC beads and MWCNT loading in the composites, a very high EMI SE value (∼23.1 dB) was achieved at low loading (2 wt%) of MWCNT with 70 wt% PC beads. The effective concentration of MWCNT increases in the solution blended PC region with increasing the amount of PC beads. Thus, a strong interconnected conductive network structure of CNT–CNT is developed throughout the matrix and the presence of strong π–π interaction among the electron-rich phenyl rings of PC and MWCNT in the composites plays a crucial role in increasing the EMI shielding value and electrical conductivity of the MWCNT–PC composites.

Conical nanopores fabricated via a pressure-biased chemical etch

Controlling the size and shape of nanopores in polymer membranes can significantly impact transport of molecular or ionic species through these membranes. Here we describe a facile method to controllably form conical nanopores in ion-tracked polycarbonate membranes. Commercial polycarbonate ion-tracked membranes were placed between a concentrated alkaline solution and an acidic solution. By varying the height of the acidic solution, the hydrostatic pressure was controlled, regulating the acid flux through the nanopores. The resulting asymmetric etching of the membrane produced conical pores with controllable aspect ratios. Scanning electron microscopy of both the pores and nickel nanostructures electrolessly templated in the pores confirms their conical shape. This safe, straightforward approach obviates the need to use large voltages, currents, and/or plasma etching equipment traditionally employed to create conical nanopores.

Lifetime assessment of Bisphenol-A Polycarbonate (BPA-PC) plastic lens, used in LED-based products

In this investigation, the accelerated optical degradation of two different commercial Bisphenol-A Polycarbonate (BPA-PC) grades under elevated temperature stress is studied. The BPA-PC plates are used both in light conversion carriers in LED modules and encapsulants in LED packages. BPA-PC plates are exposed to temperatures in the range of 100–140°C. Optical properties of the thermally-aged plates were studied using an integrated sphere. The results show that increasing the exposure time leads to degradation of BPA-PC optical properties, i.e. decrease of light transmission and increase in the yellowing index (YI). An exponential luminous decay model and Arrhenius equation are used to predict the lumen depreciation over different time and temperatures. Accelerated thermal stress tests together with the applied reliability model are used to predict the lifetime of plastic lens in LED lamps in real life conditions.

Characterization of a Sulfonated Polycarbonate Resistive Humidity Sensor

In this work; resistive moisture sensors were obtained by dip coating sulfonated polycarbonate (SPC) onto silver interdigitated electrodes. Commercial polycarbonate was sulfonated with acetyl sulphate at two different sulfonation degrees corresponding to 9.0 and 18.0 mole %. Impedance spectroscopy was used to investigate the humidity sensing properties at controlled relative humidity (RH%) environments generated from standard saline solutions in the range of 11–90 RH%. For the highest sulfonated sample; in the RH% range investigated (11 to 90%); the sensor impedance changed from 4.7 MΩ to 18 kΩ. Humidity sensors made from sulfonated polycarbonate showed exponential decay behavior of the impedance at constant frequency with the environmental relative humidity. Sample 9SPC presented dielectric relaxation response for environmental humidity between 58 and 90 RH% while sample 18SPC presented dielectric relaxation response for the entire measured range between 11 and 90 RH%. Sulfonated polycarbonate could be a promising material for the fabrication of simple and cheap humidity-sensing sensors for the assessment of relative humidity of the surrounding environment, as suggested by experimental results.

Template-Directed Electrodeposition of SnO<sub>2</sub> Nanotubes and 1D Zn/SnO<sub>2</sub> Core-Shell Nanostructures

Template-directed electrosynthesis has been employed widely to prepare solids of defined dimension. It offers controllable routes to create nanostructures. In this study, one electrochemical method to fabricate one-dimensional metal oxide nanostructures was developed. The electrochemistry strategy was employed to manipulate the pH value within the pores of a template and the growth of continuous one-dimensional metal oxide nanostructures was controlled. The strategy was exemplified by the growth of tin oxide nanotubes. At room temperature, the reduction of nitrate within pores was employed to electrogenerate hydroxide ions and drive local precipitation of stannic oxide nanotubes. The nanotube walls displayed nearly uniform thickness along their entire length which were obtained within commercial track-etched polycarbonate membranes. One-dimensional Zn/SnO2 core-shell nanostructures were achieved by the further electrodeposition of Zn within SnO2 nanotubes.

Ultrafast room temperature wiping-rubbing fabrication of graphene nanosheets as flexible transparent conductive films with high surface stability

In this letter, we developed an original innovative wiping-rubbing method to fabricate flexible transparent conductive films (TCFs) based on graphene nanosheets. We achieved this by using only commercial graphite block and polycarbonate film as raw materials, through a cost effective and ultrafast room temperature wiping-rubbing process (within 2 min). The properties of our flexible TCFs were competitive when comparing with literature reported graphene TCFs. Our flexible TCFs showed enough surface stability under a series of surface destructive treatments. The physical mechanism aspects of wiping-rubbing processes and surface stability were discussed.

Fabrication of polymeric honeycomb microporous films: breath figures strategy and stabilization of water droplets by fluorinated diblock copolymer micelles

Polymeric honeycomb microporous films were prepared from fluorinated diblock copolymers, poly(tert-butyl acrylate)-b-poly(2-[(perfluorononenyl)oxy]ethyl methacrylate) (PtBA-b-PFNEMAs), and four other commercial polymers, including polystyrene (PS), polycarbonate (PC), polylactic acid (PLA), and polymethylmethacrylate (PMMA) via breath figures method. The as-formed fluorinated diblock copolymer micelles in chloroform were not only utilized to stabilize the templated water droplets in bulk, but also introduced as the water droplets stabilizer in other polymeric materials. Our strategy was successfully achieved, as the micropores were decorated with the fluorinated diblock copolymer as directly shown in the SEM images and FT-IR/ATR-FTIR. Polymer concentration and the solution casting volume effects were checked to tune the sizes of the micropores in diblock copolymer films. The ratio of the added fluorinated diblock copolymer as a novel factor to tune the sizes of the micropores was also investigated.

Fabrication of functional silicon-based nanoporous membranes

Macroscopic porous membranes with pore diameter uniformity approaching the nanometer scale have great potential to significantly increase the speed, selectivity, and efficiency of molecular separations. We present fabrication, characterization, and molecular transport evaluation of nanoporous thin silicon-based sieves created by laser interferometric lithography (LIL). This fabrication approach is ideally suited for the integration of nanostructured pore arrays into larger microfluidic processing systems, using a simple all-silicon lithographic process. Submilli-meter-scale planar arrays of uniform cylindrical and pyramidal nanopores are created in silicon nitride and silicon, respectively, with average pore diameters below 250 nm and significantly smaller standard error than commercial polycarbonate track etched (PCTE) membranes. Molecular transport properties of short cylindrical pores fabricated by LIL are compared to those of thicker commercial PCTE membranes for the first time. A 10-fold increase in pyridine pore flux is achieved with thin membranes relative to commercial sieves, without any modification of the membrane surface.

Mapping radiation fields in containers for industrial γ-irradiation using polycarbonate dosimeters

The main part of the quality control of industrial irradiation is assurance of absorbed doses in various parts of irradiated objects. Commercial polycarbonate (PC) films develop yellow color upon radiation exposure. PC films (3mm thick) were used to map radiation fields inside product containers irradiated with Co-60 sources at IPEN. Optical densities were measured with a Shimadzu UV2101PC spectrophotometer.

Chain Packing in Glassy Polymers by Natural-Abundance 13C−13C Spin Diffusion Using 2D Centerband-Only Detection of Exchange

The proximities of specific subgroups of nearest-neighbor chains in glassy polymers are revealed by distance-dependent (13)C-(13)C dipolar couplings and spin diffusion. The measurement of such proximities is practical even with natural-abundance levels of (13)C using a 2D version of centerband-only detection of exchange (CODEX). Two-dimensional CODEX is a relaxation-compensated experiment that avoids the problems associated with variations in T(1)(C)'s due to dynamic site heterogeneity in the glass. Isotropic chemical shifts are encoded in the t(1) preparation times before and after mixing, and variations in T(2)'s are compensated by an S(0) reference (no mixing). Data acquisition involves acquisition of an S(0) reference signal on alternate scans, and the active control of power amplifiers, to achieve stability and accuracy over long accumulation times. The model system to calibrate spin diffusion is the polymer itself. For a mixing time of 200 ms, only (13)C-(13)C pairs separated by one or two bonds (2.5 Å) show cross peaks, which therefore identify reference intrachain proximities. For a mixing time of 1200 ms, 5 Å interchain proximities appear. The resulting cross peaks are used in a simple and direct way to compare nonrandom chain packing for two commercial polycarbonates with decidedly different mechanical properties.

Estimation of long-term creep behavior of polycarbonate by stress-time superposition and effects of physical aging

Long-term property estimation is required for the long-term load bearing applications of thermoplastics. In the present work, short-term creep behavior of commercial grade polycarbonate was evaluated using an in-house manufactured testing rig at various creep stress levels keeping the testing temperature constant. Creep curves were shifted with respect to the time scale and a Master curve was obtained using stress-time superposition principle. To assess the effects of physical aging on the creep behavior, various specimens with different aging histories were tested. It was observed that aging had an insignificant effect on the creep behavior of polycarbonate under the employed conditioning and testing conditions.

Large-scale synthesis of uniform nickel nanowires and their characterisation

Nickel nanowires were synthesised using template synthesis technique. Commercial polycarbonate membranes having pore diameter 100 nm were used as templates. Scanning electron microscopy depicted that the diameter and length of nanowires are same as that of pore diameter and thickness of the template membrane. X-ray diffraction and energy dispersive X-ray fluorescence recommended that the nanowires are of pure nickel metal rather than a nickel compound. Room temperature magnetic characterisation was performed using a vibrating sample magnetometer. The value of saturation magnetisation was observed as different for nickel nanowires with different aspect ratio.

The effect of oligomer blending on the flow properties of polycarbonate

We successfully prepared high-flow polycarbonate (PC) by blending commercial PC with a low molecular weight PC oligomer. The oligomer was synthesized by the addition of a large quantity of mono functional phenol groups, and the chain end group was reacted withp-tertiary butyl phenol (PTBP) to block the reactivity. The viscosity average molecular weight (M v ) for the oligomer was about 4,000–5,000 g/mol, compared to ∼19,000 g/mol for the PC blend obtained by blending 10 wt% of the prepared oligomer with the commercial grade PC (M v of 21,000 g/mol). The blended PC had a melt flow index of 45, which is 2.5 times higher, and a processing temperature that was 20 °C lower, than that of commercial grade PC having a similarM v .

Nanopore immunosensor for peanut protein Ara h1

A nanopore immunosensor is demonstrated for peanut protein Ara h1, a common food allergen. This biosensor is constructed by immobilizing the antibody to peanut protein Ara h1 within Au-coated pores of commercial nanoporous polycarbonate membranes. Peanut protein Ara h1 is detected as the change in the pore conductivity as the pores are partially obscured by antigen binding. Control experiments with the antibody to cockroach protein Bla g1 demonstrate that the observed effects do not arise from non-specific adsorption. Binding of peanut protein is studied as a function of the pore diameter (15, 30 and 50 nm), and as a function of the concentration of peanut protein. The results show the greatest sensitivity for membranes with the smallest pore diameter, and exhibit mass transfer effects for membranes with larger pore diameters. Approximate calculations of diffusion times for transport of peanut protein Ara h1 through these nanoporous membranes suggest that mass transport effects should not be observed. This discrepancy between experimental observations of mass transfer effects and model predictions suggest that diffusion of peanut protein Ara h1 is anomalously slow in this system.

Current-driven, electrically detected ferromagnetic resonance in electrodeposited spin valves

We investigate the ferromagnetic resonance of Co/Cu/Co trilayers by use of AC-spin-transfer torque excitations. Magnetic structures are grown in a 6-μm-thick commercial nanoporous polycarbonate membranes by use of electrodeposition in a cobalt/copper single bath. We show that microwave magnetic excitations corresponding to the uniform mode of the two cobalt layers are electrically detected as a change of the DC voltage of the system.