Repository hosted by TU Delft Library

For the experimental characterization of behind-armour debris so-called metallic witness packs can be used. A metallic witness pack consists of an array of metallic plates interspaced by polystyrene foam sheets. To quantify the fragment mass and velocity from the corresponding hole area and position in the individual witness plates, perforation threshold curves must be available to provide the ballistic limit velocity for each plate as a function of the fragment mass. Furthermore, the relation between the fragment impact velocity and hole size should be known. This paper presents the results of a collaborative study between Defence Research Establishment, Valcartier (DREV) and TNO Prins Maurits Laboratory, The Netherlands. The first phase of this project is an experimental study to develop perforation threshold and hole-growth curves for two metallic witness pack configurations. In addition, it is shown that a hydrocode can be successfully used to predict perforation threshold velocities.

Linear block copolymers of polystyrene and polysaccharide were synthesized using a block synthesis method with amino-terminated polystyrene and sodium cyanoborohydride as reducing agent. Different types of polysaccharides, dextrans, and maltodextrins with various molecular weights were used. IR spectroscopy indicated a successful coupling. Yields of reaction are 75-95 wt %. Attempts to couple long dextrans (Mw > 6000 Da) were not successful. Interfacial pressure measurements of monolayers of the copolymers on water showed interfacial behavior typical for amphiphilic compounds and different from the starting compounds, confirming the coupling reaction. Time-dependent hysteresis occurs between successive compression and expansion cycles. This is, to a large extent, due to the slow adsorption/desorption of the polysaccharide chains at the air-water interface and the formation of aggregates of copolymer at the interface. Aggregates are mainly formed by H-bonds between adjacent polysaccharide chains. The relaxation time for hysteresis, determined for polystyrene-dextran copolymer, was 85 min.

The use of a state-of-the-art commercial solvent-elimination interface for liquid chromatography-infrared spectroscopy is discussed from the perspective of quantitative analysis. The effect of eluent flow-rate is investigated with respect to the homogeneity of the deposit and the trace width along the deposition trace. Low flow-rates (50 μl/min or less) turn out to be favorable for obtaining a good trace and a high sensitivity. The trace width decreased from 2.20 to 1.13 mm when the flow-rate was reduced from 500 to 25 μl/min. Preservation of chromatographic detail during deposition was evaluated at different substrate moving speeds. The additional (extra-column) band broadening that is inherent to nebulizer-deposition interfaces, causes a loss in resolution in size-exclusion chromatography (SEC)-Fourier transform infrared (FTIR) spectroscopy in comparison with SEC-UV. The repeatability of the deposition is evaluated by SEC-FTIR analyses of polystyrene standards (peak molar-masses: 1250-2 950 000 g/mol) and the RSD is found to range from 3.2 to 5.8% in response and from 0.21 to 0.47% in retention time. © 2002 Elsevier Science B.V. All rights reserved. Chemicals/CAS: Indicators and Reagents; Polystyrenes; Solvents

In Japan there is growing concern about the possible adverse effects of consumption of food from styrene containers (mainly those made from polystyrene paper) due to the alleged oestrogenic activity of styrene oligomers (dimers and trimers), which may migrate into the food. To examine the possible oestrogenic activity of styrene dimers and trimers, extracts were made from 'general purpose polystyrene (GPPS)' and administered orally to immature female rats over a 4 day period. Increase of uterus weight (wet and blotted) was used for assessment of possible oestrogenic activity. To establish the sensitivity of the test method, immature rats were treated with diethylstilboestrol (DES), a well-known oestrogenic compound. It was found that treatment of rats with levels of up to 60 μg of styrene dimers and 930 μg of styrene trimers per kilogram body weight per day did not give any statistically significant increase of the uterus weight (wet or blotted), whereas DES caused statistically significant, dose-related increases in uterus weight at levels as low as 0.89 μg kg-1 body weight day-1. It was concluded that, compared with the estimated maximum human daily intake of styrene trimers of 1 μg kg-1 body weight day-1 from polystyrene food containers, the risk of adverse human health effects with respect to oestrogenicity may be considered negligible. Copyright © 2001 John Wiley & Sons, Ltd. Chemicals/CAS: Estrogens; Polystyrenes

Poly(styrene-b-butyl methacrylate) diblock copolymers, PS-6-PBMA, with different morphologies are investigated with respect to the influence of strain rate and temperature on tensile properties. In the first part the mechanical properties of bicontinuous and perforated lamellar structure are compared with other morphologies. Diblock copolymers with bicontinuous structures (39% PS) show a much higher tensile strength as well as a higher strain at break than diblock copolymers with lamellar structures (50% PS). In the second part the dependence of tensile properties on strain rate and temperature are discussed for different morphologies. A diblock copolymer with a polystyrene content of 76% PS reveals hexagpnally packed PBMA-cylinder, and the tensile strength, strain at break, and Young's modulus exceed the values of pure polystyrene at all measured strain rates. The interesting properties of PS-b-PBMA diblock copolymers are discussed with respect to the phase behavior, interface formation, and chain conformation.

Diblock copolymers consisting of polystyrene and acid-functionalized poly(propylene imine) dendrimers have been found to self-assemble spontaneously into regular microdomains. The hybride dendrimer-linear chain block copolymers yield highly asymmetric molecules which display an aggregation behavior at the strong segregation limit that differs from the well-known all-linear block copolymers. The morphological features are used to determine the relationship between the architecture of the blocks and the arrangement of the molecules in the bulk. Microlattice formation of these materials was examined by using small-angle X-ray scattering and transmission electron microscopy techniques. By increasing the dendrimer generation, the structures changed from hexagonally packed cylinders with polystyrene as matrix to lamellar phases of different packing density. Good agreement between TEM and SAXS results was obtained, and the microlattice morphology was found to be highly dependent on the dendrimer generation.

Mechanical properties of poly(styrene-b-n-butylmethacrylate) diblock copolymers, PS-b-PBMA, with different lengths of the polystyrene block were investigated. The copolymers display a composition range where the tensile strength of the block copolymers exceeds the values of the corresponding homopolymers. At a PS-content of 74 vol% not only the tensile strength but also the strain at break is higher than that of pure polystyrene. Furthermore, the absorbed energy shows a maximum at a polystyrene content of 29 vol%. This composition reveals a morphology of hexagonally packed PS-cylinders which turns out to be effective for the increase of toughness in PS-b-PBMA diblock copolymers. The improved mechnical properties of PS-b-PBMA diblock copolymers are discussed with respect to a possible correlation and synergism between phase behaviour, morphology, deformation mechanism, and interface formation. © 1998 Elsevier Science Ltd.

We present the synthesis of glucose-functionalized polystyrene particles through emulsion polymerisation using glucose acrylate as reactive surfactant. Additionally, we present the selective deposition of silver on the surface of these particles yielding well-defined polystyrene-silver composites.

We ink-jet print a blend of 6,13-bis(triisopropyl-silylethynyl)pentacene and polystyrene as the active layer for flexible circuits. The discrete ink-jet printed transistors exhibit a saturation mobility of 0.5 cm2 V -1 s-1. The relative spread in transistor characteristics can be very large. This spread is due to the morphology of the TIPS-PEN crystals, and is difficult to control using inkjet printing. Here we apply a novel circuitry design to minimize the probability of differences between the transistors. We include up to four transistors under the same ink-jet printed deposit. With the new design, we demonstrate unipolar circuitry building blocks such as inverters, NANDs and 19-stage ring-oscillators. Additionally, we integrate almost 300 TFTs, on a surface area of 34 mm2 of plastic foil, for 8-bit RFID transponder circuits. © 2012 Elsevier B.V. All rights reserved.

A new microfluidic approach for charge-based particle separation using combined hydrodynamic and electrokinetic effects is presented. A recirculating flow pattern is employed, generated through application of bi-directional flow in a narrow glass microchannel incorporating diverging or converging segments at both ends. The bi-directional flow in turn is a result of opposing pressure-driven flow and electro-osmotic flow in the device. Trapping and preconcentration of charged particles is observed in the recirculating flow, under conditions where the average net velocity of the particles themselves approaches zero. This phenomenon is termed flow-induced electrokinetic trapping (FIET). Importantly, the electrophoretic mobility (zeta potential) of the particles determines the flow conditions required for trapping. In this paper, we exploit FIET for the first time to perform particle separations. Using a non-uniform channel, one type of particle can be trapped according to its zeta-potential, while particles with higher or lower zeta-potentials are flushed away with the pressure-driven or electro-osmotic components, respectively, of the flow. This was demonstrated using simple mixtures of two polystyrene bead types having approximately the same size (3 m) but different zeta potentials (differences were in the order of 25 to 40 mV). To gain more insight into the separation mechanism, particle separations in straight, 3 cm-long microchannels with uniform cross-section were also studied under conditions of bi-directional flow without trapping. A thorough theoretical analysis confirmed that trapping occurs when electrokinetic and pressure-driven particle velocities are equal and opposite throughout the diverging segment. This makes it possible to predict the pressure and electric field conditions required to separate particles having defined zeta potentials. © 2009 The Royal Society of Chemistry.

The likelihood of oral exposure to nanoparticles (NPs) is increasing, and it is necessary to evaluate the oral bioavailability of NPs. In vitro approaches could help reducing animal studies, but validation against in vivo studies is essential. Previously, we assessed the translocation of 50 nm polystyrene NPs of different charges (neutral, positive and negative) using a Caco-2/HT29-MTX in vitro intestinal translocation model. The NPs translocated in a surface charge-dependent manner. The present study aimed to validate this in vitro intestinal model by an in vivo study. For this, rats were orally exposed to a single dose of these polystyrene NPs and the uptake in organs was determined. A negatively charged NP was taken up more than other NPs, with the highest amounts in kidney (37.4 µg/g tissue), heart (52.8 µg/g tissue), stomach wall (98.3 µg/g tissue) and small intestinal wall (94.4 µg/g tissue). This partly confirms our in vitro findings, where the same NPs translocated to the highest extent. The estimated bioavailability of different types of NPs ranged from 0.2 to 1.7 % in vivo, which was much lower than in vitro (1.6–12.3 %). Therefore, the integrated in vitro model cannot be used for a direct prediction of the bioavailability of orally administered NPs. However, the model can be used for prioritizing NPs before further in vivo testing for risk assessment. © 2015, The Author(s).

When plastics are collected for recycling, possibly contaminated articles might be recycled into food packaging, and thus the contaminants might subsequently migrate into the food. Multilayer functional barriers may be used to delay and to reduce such migration. The contribution of the work reported here is to establish reference values (at 40°C) of diffusion coefficients and of activation energies to predict the functional barrier efficiency of a broad range of polymers (polyolefins, polystyrene, polyamide, PVC, PET, PVDC, [ethylene vinyl alcohol copolymer], polyacrylonitrile and [ethylene vinyl acetate copolymer]). Diffusion coefficients (D) and activation energies (Ea) were measured and were compiled together with literature data. This allowed identification of new trends for the log D=f(molecular weight) relationships. The slopes were a function of the barrier efficiency of the polymer and temperature. The apparent activation energy of diffusion displayed two domains of variation with molecular weight (M). For low M (gases), there was little variation of Ea. Focusing on larger molecules, high barrier polymers displayed a larger dependence of Ea with M. The apparent activation energy decreased with T. These results suggest a discontinuity between rubbery and glassy polymers. © 2006 Taylor & Francis. Chemicals / CAS: ethylene vinyl acetate copolymer, 24937-78-8; ethylene vinyl alcohol copolymer, 25067-34-9; polyacrylonitrile, 25014-41-9, 63231-45-8; polyamide, 63428-83-1; polyethylene terephthalate, 25038-59-9, 9003-68-3; polystyrene, 9003-53-6; polyvinylchloride, 9002-86-2; rubber, 9006-04-6; vinylidene chloride, 25323-30-2, 75-35-4; Acrylic Resins; ethylene-vinyl alcohol copolymer, 25067-34-9; ethylenevinylacetate copolymer, 24937-78-8; Nylons; PL 732, 83136-87-2; Plastics; polyacrylonitrile, 25014-41-9; Polyenes; Polyethylene Terephthalates; Polymers; Polystyrenes; Polyvinyl Chloride, 9002-86-2; Polyvinyls

Two solvent-tolerant Pseudomonas putida S12 strains, originally designed for phenol and p-coumarate production, were engineered for efficient production of p-hydroxystyrene from glucose. This was established by introduction of the genes pal and pdc encoding L-phenylalanine/L-tyrosine ammonia lyase and p-coumaric acid decarboxylase, respectively. These enzymes allow the conversion of the central metabolite L-tyrosine into p-hydroxystyrene, via p-coumarate. Degradation of the p-coumarate intermediate was prevented by inactivating the fcs gene encoding feruloyl-coenzyme A synthetase. The best-performing strain was selected and cultivated in the fed-batch mode, resulting in the formation of 4.5 mM p-hydroxystyrene at a yield of 6.7% (C-mol of p-hydroxystyrene per C-mol of glucose) and a maximum volumetric productivity of 0.4 mM h-1. At this concentration, growth and production were completely halted due to the toxicity of p-hydroxystyrene. Product toxicity was overcome by the application of a second phase of 1-decanol to extract p-hydroxystyrene during fed-batch cultivation. This resulted in a twofold increase of the maximum volumetric productivity (0.75 mM h-1) and a final total p-hydroxystyrene concentration of 21 mM, which is a fourfold improvement compared to the single-phase fed-batch cultivation. The final concentration of p-hydroxystyrene in the water phase was 1.2 mM, while a concentration of 147 mM (17.6 g liter-1) was obtained in the 1-decanol phase. Thus, a P. putida S12 strain producing the low-value compound phenol was successfully altered for the production of the toxic value-added compound p-hydroxystyrene. Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Several series of nanocomposites were prepared using a latex-based process, the main step of which consisted of mixing an aqueous suspension of exfoliated carbon nanotubes (CNTs) and a polymer latex. In the present work, a systematic study on the electrical properties of fully amorphous (polystyrene - PS) as well as semi-crystalline (isotactic polypropylene - iPP) nanocomposites containing either single-wall (SWCNTs) or multi-wall carbon nanotubes (MWCNTs) has been conducted. Percolation thresholds as low as 0.05 wt.% or 0.1 wt.% were observed for SWCNT/iPP and MWCNT/iPP nanocomposites, respectively. The formation of a conductive percolating network at such a low CNT concentration is favored by the high intrinsic conductivity and the low viscosity of the polymer matrix. The electrical percolation threshold of the iPP-based system was found to be lower than its rheological percolation threshold. Beyond the percolation threshold, MWCNT-based nanocomposites generally exhibited higher conductivity levels than those based on SWCNTs, most probably due to the higher intrinsic conductivity of the MWCNTs as compared to that of the SWCNTs. These excellent electrical properties, associated with the strong nucleating effect of the CNTs reported earlier [1,2], render this type of nanocomposites extremely attractive from a technological point of view. © 2010 Elsevier Ltd. All rights reserved.

We present a systematic study of the influence of material composition and ink-jet processing conditions on the charge transport in bottom-gate field-effect transistors based on blends of 6,13-bis(triisopropyl-silylethynyl) pentacene (TIPS-PEN) and polystyrene. After careful process optimizations of blending ratio and printing temperature we routinely can make transistors with an average mobility of 1 cm2/Vs (maximum value 1.5 cm 2/Vs), on/off ratio exceeding 107, and sharp turn-on in current (sub-threshold slopes approaching 60 mV/decade). These characteristics are superior to the TIPS-PEN only transistors. Using channel scaling measurements and scanning Kelvin probe microscopy, the sharp turn-on in current in the blends is attributed to a contact resistance that originates from a thin insulating layer between the injecting contacts and the semiconductor channel. © 2011 Elsevier B.V. All rights reserved.

Doppler test objects are used to characterise Doppler systems, both stand-alone systems and the Doppler part of so-called duplex scanners. The aim of the project partially presented here is the development and validation of an example of a Doppler test object fulfilling the requirements of the IEC 1685. The project has been carried out by nine partners of five European countries and has been funded by the European Commission. The flow Doppler test object is composed of: tissue mimicking material (TMM), blood mimicking fluid (BMF), tube (embedded in the TMM and carrying the BMF), tank, flow system, including a pump and a flow meter. In the normative part of the IEC 1685, requirements are given for the values of acoustical parameters of TMM and BMF such as sound velocity, attenuation and backscattering. For BMF, requirements are given also for values of density and viscosity. In an informative (but not compulsory) annex, a description is given of a flow test object meeting these requirements as an example. This 'example test object' developed during the project is composed of TMM based on agar and including SiC-and Al2O3-powders, BMF based on nylon particles suspended in water and glycerine, and a tube of c-flex, a silicon copolymer. Two tube sizes are used: 4.0 mm ID and 8.0 mm ID. During the project, very precise recipes have been developed for the composition and preparation of both TMM and BMF. Based on these recipes and a description of the construction in a design five flow test objects have been constructed in the laboratories of five participants. The test objects have been compared by measurements of the physical parameters and by Doppler measurements of the five test objects with the same Doppler system. The measurements have been carried out by five observers. Inter-test object and inter-observer variabilities are determined, yielding information about usefulness of the parameters. © 1998 Elsevier Science B.V. Chemicals/CAS: Agar, 9002-18-0; Aluminum Oxide, 1344-28-1; Biocompatible Materials; C-Flex, 104521-01-9; Glycerol, 56-81-5; Nylons; Polyethylenes; Polystyrenes; Silicon, 7440-21-3

This work describes the fabrication, characterization, and biological evaluation of a thin protein-resistant poly(ethylene glycol) (PEG)-based hydrogel coating for antifouling applications. The coating was fabricated by free-radical polymerization on silanized glass and silicon and on polystyrene-covered silicon and gold. The physicochemical properties of the coating were characterized by infrared spectroscopy, ellipsometry, and contact angle measurements. In particular, the chemical stability of the coating in artificial seawater was evaluated over a six-month period. These measurements indicated that the degradation process was slow under the test conditions chosen, with the coating thickness and composition changing only marginally over the period. The settlement behavior of a broad and diverse group of marine and freshwater fouling organisms was evaluated. The tested organisms were barnacle larvae (Balanus amphitrite), algal zoospores (Ulva linza), diatoms (Navicula perminuta), and three bacteria species (Cobetia marina, Marinobacter hydrocarbonoclasticus, and Pseudomonas fluorescens). The biological results showed that the hydrogel coating exhibited excellent antifouling properties with respect to settlement and removal. © 2008 American Chemical Society.