Polystyrene Pellets Research Articles

Polystyrene/multi-wall carbon nanotube composite and its foam assisted by ultrasound vibration

Polystyrene/multi-wall carbon nanotube composite with an interconnected honeycomb-like structure was prepared by firstly coating the surface of the polystyrene pellets with multi-wall carbon nanotube, and sequentially welded through an ultrasound vibration technique. The mechanical and morphological properties of as-prepared composite were investigated in various measurements. It was found that an aggregative and honeycomb-like morphology of multi-wall carbon nanotube existed in the polystyrene/multi-wall carbon nanotube composite according to the polarized optical microscopic and scanning electron microscopic results; the ultrasound vibration could benefit to the performance of flexural strength. Furthermore, different composite foams were studied in this work, employing supercritical carbon dioxide as a blowing agent. Compared to other foams prepared by the conventional methods, the compressive strength of the foams derived from as-described novel method, was significantly improved. Also, being ascribed to this interconnected structure by coating carbon nanotube on polystyrene pellets, good electrical conductivity of 0.05–0.11 S/m was achieved in the novel composite foams.

Packed Bed Bioreactor for the Isolation and Expansion of Placental-Derived Mesenchymal Stromal Cells.

Large numbers of Mesenchymal stem/stromal cells (MSCs) are required for clinical relevant doses to treat a number of diseases. To economically manufacture these MSCs, an automated bioreactor system will be required. Herein we describe the development of a scalable closed-system, packed bed bioreactor suitable for large-scale MSCs expansion. The packed bed was formed from fused polystyrene pellets that were air plasma treated to endow them with a surface chemistry similar to traditional tissue culture plastic. The packed bed was encased within a gas permeable shell to decouple the medium nutrient supply and gas exchange. This enabled a significant reduction in medium flow rates, thus reducing shear and even facilitating single pass medium exchange. The system was optimised in a small-scale bioreactor format (160 cm2) with murine-derived green fluorescent protein-expressing MSCs, and then scaled-up to a 2800 cm2 format. We demonstrated that placental derived MSCs could be isolated directly within the bioreactor and subsequently expanded. Our results demonstrate that the closed system large-scale packed bed bioreactor is an effective and scalable tool for large-scale isolation and expansion of MSCs.

Extended spectrum beta-lactamases in Escherichia coli from municipal wastewater.

Over the past decades, awareness of the environmental load of resistant organisms has increased. The presented paper focuses on antibiotic resistance and detection of resistance genes in environmental E. coli and on the evaluation of biofilm formation in ESBLs (extended spectrum beta-lactamase) producing E. coli isolated from an urban wastewater treatment plant. Wastewater samples and artificially added polystyrene pellets were used as the source for E. coli isolation. Minimal inhibitory concentrations of 19 antibiotics were determined according to CLSI (2013). Biofilm formation was investigated by crystal violet or resazurin methods. CTX-M, carbapenemases, qnrS, mobile elements and virulence factors were determined by PCR. Clonal relatedness of strains was detected by principal component analysis by a Maldi biotyper. ESBL phenotype was detected in 26% of environmental strains. CTX-M, CMY-2 and qnrS genes of antibiotic resistance were detected. IMP gene together with integron 1 in one ertapenem resistant E. coli was also recorded. There was no evident correlation between antibiotic resistance, virulence and biofilm production. The results showed that the wastewater is a source of ESBLs, carbapenemases and plasmid fluoroquinolone resistance. Strains with biofilm production, antibiotic resistance of CTX-M group, CMY-2, qnrS genes and virulence factors present a potential environmental health risk.

Ingested microplastics (>100 μm) are translocated to organs of the tropical fiddler crab Uca rapax

Microplastics, which are accumulating in marine sediments, are assumed to pose a risk for deposit feeding invertebrates. We tested whether the fiddler crab Uca rapax ingests and retains microplastics in its body. Furthermore, we investigated whether retention rates depend on (a) the quality of the marine environment in which the plastics were pre-weathered and on (b) their abundance. For this, polystyrene pellets were submersed at a polluted and a pristine site near Niterói, Brazil, for 2weeks. Then specimens of U. rapax were, in laboratory experiments, exposed to fragments (180–250μm) derived from these pellets for 2months. After this period, microplastics were observed in the gills, stomach and hepatopancreas of the animals. However, fragment retention was not influenced by the two factors that we manipulated. The presence of microplastics in different organs of the crab supports the assumption that these particles have the potential to harm marine invertebrates.

Live-Bed Scour at Bridge Piers in a Lightweight Polystyrene Bed

AbstractExperiments on scour at bridge piers were carried out in a sediment recirculating flume with a bed of polystyrene particles. The focus of the research reported in this paper was given to live-bed experiments. All experiments were run until equilibrium conditions with flow velocities u ranging from 0.8–8.5 times the critical velocity for the incipient motion of sediment particles uc. Maximum scour depth was continuously measured with an endoscopic camera from inside the pier, which was constructed by a plexiglass cylinder. Bed load transport with dunes was identified as the main transport mode for 1<u/uc<4. For ratios of u/uc≥4 entrainment into suspension without development of bedforms dominated. Results show that scour rapidly reach equilibrium in the bed of polystyrene pellets. In the clear-water experiments equilibrium scour depth remained constant in time. In the bed load region the fluctuation of scour depth corresponded to the dune migration through the scour hole, while in the suspended loa...

A more direct way to synthesize styrene

Polymer Chemistry![Figure][1] Polystyrene pellets PHOTO: © BLICKWINKEL/ALAMY Foam cups, foam pellets, plastic cutlery: All are made of polystyrene, which in turn is made of styrene. The massive manufacturing scale of this commodity chemical places a premium on the efficiency of its synthesis. The current industrial route requires three steps to make styrene from benzene and ethylene. Vaughan et al. present a rhodium catalyst that achieves the coupling in a single step by using a recyclable copper salt as an oxidant. Although the catalyst is slow for industrial application, it demonstrates the viability of a more direct process. Science , this issue p. [421][2] [1]: pending:yes [2]: /lookup/doi/10.1126/science.aaa2260

Polymer Protects Against Preterm Birth

The massive, gooey molecule hyaluronan protects the cervix from infections that can cause preterm birth, according to a study in mouse and human cells. The cervix serves as the first line of defense against microbes ascending the reproductive tract, and it also must accommodate birth. During pregnancy, cervical tissue becomes soft and compliant, the cells of the cervical epithelia proliferate, and mucus secretion increases. Cells throughout the cervix also ramp up production of hyaluronan, a sugar polymer with a wide array of functions, from maintaining extracellular matrix integrity to regulating innate immunity. Hyaluronan is found throughout the body, and is even present in breast milk—inducing the expression of antimicrobial peptides in the gut mucosa. In a new study [1], Yucel Akgul et al. took a close look at the function of this molecule in the cervix, where it is found in the extracellular matrix and in cervicovaginal mucus. The researchers created mice deficient in hyaluronan in the cervix, and found that the cervical epithelium of these appeared disorganized and had defects in expression of occludin, a tight junction protein. Moreover, depleting hyaluronan in a human cervical cell line increased epithelial cell permeability. In a separate experiment, hyaluronan also was shown to help maintain properties of the mucus—mucus from hyaluronan-deficient mice had increased permeability to bacteria-sized polystyrene pellets. The researchers conclude that hyaluronan is necessary to maintain the structure and integrity of the epithelium and for proper barrier function of mucus. These functions protect mice from preterm birth induced by bacterial infection. In various assays, mice deficient in hyaluronan were at least twice as susceptible to infection-induced preterm birth as wild-type mice. That finding dovetails with clinical studies showing differences in the properties of cervicovaginal mucus in women at high risk of preterm birth, compared to women not at risk. The new findings also downplay a role for hyaluronan in the matrix remodeling that occurs prior to labor, and that helps soften the cervical tissue. For instance, cervical stiffness was not affected in hyaluronan-deficient mice, and changes in cervical collagen throughout pregnancy—such as increased disorganization—proceeded fairly normally. The findings increase understanding of the factors that may contribute to preterm birth, a poorly understood but major public health issue. Complications from preterm birth are the leading cause of death in children under five years of age worldwide, according to a recent study in The Lancet [2], and infections are one major driver of this statistic.

Wind tunnel study of twelve dust samples by large particle size

Due to the lack of data by large dust and sand particle, the fluid dynamics characteristics, hence the collection efficiencies of different twelve dust samplers have been experimentally investigated. Wind tunnel tests were carried out at wind velocities ranging from 1 up to 5.5 ms−1. As a large solid particle of 0.5 and 1 mm in diameter, Polystyrene pellets called STYRO Beads or polystyrene sphere were used instead of sand or dust. The results demonstrate that the collection efficiency is relatively acceptable only of eight tested sampler and lie between 60 and 80% depending on the wind velocity and particle size. These samplers are: the Cox Sand Catcher (CSC), the British Standard Directional Dust Gauge (BSD), the Big Spring Number Eight (BSNE), the Suspended Sediment Trap (SUSTRA), the Modified Wilson and Cooke (MWAC), the Wedge Dust Flux Gauge (WDFG), the Model Series Number 680 (SIERRA) and the Pollet Catcher (POLCA). Generally they can be slightly recommended as suitable dust samplers but with collecting error of 20 up to 40%. However the BSNE verify the best performance with a catching error of about 20% and can be with caution selected as a suitable dust sampler. Quite the contrary, the other four tested samplers which are the Marble Dust Collector (MDCO), the United States Geological Survey (USGS), the Inverted Frisbee Sampler (IFS) and the Inverted Frisbee Shaped Collecting Bowl (IFSCB) cannot be recommended due to their very low collection efficiency of 5 up to 40%. In total the efficiency of sampler may be below 0.5, depending on the frictional losses (caused by the sampler geometry) in the fluid and the particle's motion, and on the intensity of airflow acceleration near the sampler inlet. Therefore, the literature data of dust are defective and insufficient. To avoid false collecting data and hence inaccurate mass flux modeling, the geometry of the dust sampler should be considered and furthermore improved.

Polystyrene Plastic: A Source and Sink for Polycyclic Aromatic Hydrocarbons in the Marine Environment

Polycyclic aromatic hydrocarbons (PAHs) on virgin polystyrene (PS) and PS marine debris led us to examine PS as a source and sink for PAHs in the marine environment. At two locations in San Diego Bay, we measured sorption of PAHs to PS pellets, sampling at 0, 1, 3, 6, 9, and 12 months. We detected 25 PAHs using a new analytical method with comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry. Several congeners were detected on samples before deployment. After deployment, some concentrations decreased (1,3-dimethylnaphthalene and 2,6-methylnaphthalene), while most increased [2-methylanthracene and all parent PAHs (PPAHs), except fluorene and fluoranthene], suggesting that PS debris is a source and sink for PAHs. When sorbed concentrations of PPAHs on PS are compared to the five most common polymers [polyethylene terephthalate (PET), high-density polyethylene (HDPE), polyvinyl chloride (PVC), low-density polyethylene (LDPE), and polypropylene (PP)], PS sorbed greater concentrations than PP, PET, and PVC, similar to HDPE and LDPE. Most strikingly, at 0 months, PPAHs on PS ranged from 8 to 200 times greater than on PET, HDPE, PVC, LDPE, and PP. The combination of greater PAHs in virgin pellets and large sorption suggests that PS may pose a greater risk of exposure to PAHs upon ingestion.

Raman correlation spectroscopy: A method studying physical properties of polystyrene by the means of multivariate analysis

Raman spectroscopy was used to determine physical properties of various grades of polystyrene, such as the Vicat temperature, the Izod impact and the Melt Flow Index. A number of 255 measurements were acquired on 195 samples of polystyrene pellets. The objective of this study is the correlation of these Raman results with those obtained by conventional techniques. Raman data endured different pre-treatments, such as correction of baseline, area normalization, selection of variables or multiple scatter correction. First, to discriminate the different families of polystyrene, Principal Component Analysis was applied to Raman spectra. Then, on the basis of Partial Least Square regression with random cross validation, the correlation between Raman spectrum of polystyrene and its physical properties was studied and discussed in the case of each pre-processing, in terms of correlation factor, the root-mean-square-error of calibration, the root-mean-square-error of validation and the root-mean-square-error of prediction, the bias and the number of latent variables. For example, in the specific case of the Vicat temperature, the best correlation factor is close to 0.98, and the root-mean-square-error of prediction is 0.85°C with three latent variables which are correlated with the Raman spectrum of raw materials.

Image analysis measurements of particle coefficient of restitution for coal gasification applications

New robust Lagrangian computational fluid dynamic (CFD) models are powerful tools that can be used to study the behavior of a diverse population of coal particle sizes, densities, and mineral compositions in entrained gasifiers. By using this approach, the responses of the particles impacting the wall were characterized over a range of velocities (1 to 8m/s) and incident angles (90 to 20°). Within CFD models, the kinematic coefficient of restitution is the boundary condition defining the particle wall behavior. Four surfaces were studied to simulate the physical conditions of different entrained-flow gasification particle–surface collision scenarios: 1) a flat metal plate 2) a low viscosity silicon adhesive, 3) a high viscosity silicon adhesive, and 4) adhered particles on a flat metal plate with Young's modulus of elasticity ranging from 0.9 to 190GPa. Entrained flow and drop experiments were conducted with granular coke particles, polyethylene beads and polystyrene pellets. The particle normal and tangential coefficients of restitution were measured using high speed imaging and particle tracking. The measured coefficients of restitution were observed to have a strong dependence on the rebound angles for most of the data. Suitable algebraic expressions for the normal and the tangential component of the coefficient of restitution were developed based upon ANOVA analysis. These expressions quantify the effect of normalized Young's modulus, particle equancy, and relative velocity on the coefficient of restitution. The coefficient of restitution did not have a strong dependence on the particle velocity over the range considered as long as the velocity was above the critical velocity. However, strong correlations were found between the degree of equancy of the particles and the mean coefficient of restitution such that the coefficient of restitution decreased for smaller particle equancies. It was concluded that the degree of equancy and the normalized Young's modulus should be considered in applications such as gasification and other cases involving the impact of non-spherical particles and complex surfaces. Sliding was observed when particles impacted on oblique surfaces; however, the resulting effects were within the range of measurement uncertainties.

Quantification of rubber in high impact polystyrene by Raman spectroscopy. Comparison of a band fitting method and chemometrics

An analytical method for the detection and the quantification of polybutadiene (rubber) in high impact polystyrene is described. The percentage of this product in high impact polystyrene pellets influences many of its properties, more the concentration is great, and more the mechanical resistance is high. The analytical method currently used to estimate the proportion of polybutadiene in high impact polystyrene pellets is nuclear magnetic resonance. Nevertheless, the application of Raman spectroscopy to polymers becomes more popular because of its sensitivity to the CC vinyl bond. This technique offers various advantages such as the absence of sample preparation. Raman spectroscopy is furthermore non destructive, and is a reproducible method. Information about conformations of polybutadiene can be easily accessible. Two different quantitative procedures were compared to evaluate which one is the best to estimate the percentage of polybutadiene in high impact polystyrene pellets. The first conventional method was based on the bands fitting of Raman spectra, and yielded a good prediction with a R2 regression coefficient equal to 0.96. The second was based on chemometric techniques with a 0.98−R2. Consequently, others evaluation factors of the procedures such as the root-mean-square error, the bias, or the number of principal components must have some influence to select the most appropriate quantitative model.

Microplastics in Beaches of the East Frisian Islands Spiekeroog and Kachelotplate

Microplastic particles were quantified in beach transects of the East Frisian islands Spiekeroog and Kachelotplate and in two samples from a tidal flat. Both granules and fibres were present while fragments and polystyrene pellets were completely absent. On the Kachelotplate the highest number of granules (496/10g sediment) was observed at the high water line while on Spiekeroog a sample from the dune area had the highest value (38/10g sediment). The tidal flat samples hat 36 and 136 granules/10g sediment with the higher number being associated with a blue mussel bank. Fibres were more homogeneously distributed and did not show any particular enrichment. In comparison with data from the Belgian coast the total numbers are higher which might be related to the exposure situation of the island beaches.

Comparison of covalent immobilization of amylase on polystyrene pellets with pentaethylenehexamine and pentaethylene glycol spacers

α-Amylase from Aspergillus oryzae was covalently immobilized onto polystyrene pellets with pentaethylenehexamine (PS-PEHA-Ald) and pentaethylene glycol (PS-PG-Ald) carrying a terminal aldehyde group. Optimum immobilization occured at pH 8.0 and 25°C, and at pH 7.0 and 35°C for PS-PEHA-Ald and PS-PG-Ald, respectively. PS-PEHA-Ald immobilized enzyme retained approximately 75% of the initial activity over 45days of storage, 70% of the initial activity after nine runs of recycling and displayed the better resistance to detrimental metal ions. PS-PG-Ald immobilized enzyme retained approximately 50% of the initial activity in 8h at 70°C. The catalytic efficiencies of PS-PEHA-Ald immobilized and PS-PG-Ald immobilized amylase were 1.42 and 1.29 times higher than that of native enzyme. The activation energy of the reaction mediated by the amylase was reduced by 58.1% and 57.3% when PS-PEHA-Ald and PS-PG-Ald used as support respectively.

Pellet interaction with runaway electrons

We describe results from recent experiments studying interaction of solid polystyrene pellets with a runaway electron current channel generated after cryogenic argon pellet rapid shutdown of DIII-D. Fast camera imaging shows the pellet trajectory and continuum emission from the subsequent explosion, with geometric calibration providing detailed explosion analysis and runaway energy. Electron cyclotron emission also occurs, associated with knock-on electrons broken free from the pellet by RE which then accelerate and runaway, and also with a short lived hot plasma blown off the pellet surface. In addition, we compare heating and explosion times from observations and a model of pellet heating and breakdown by runaway interaction.

Introducing water as a coblowing agent in the carbon dioxide extrusion foaming process for polystyrene thermal insulation foams

AbstractIn this study, water was used as a coblowing agent in the carbon dioxide (CO2) extrusion foaming process in a twin screw extruder. It enlarged cell size and thus lowered foam density for better thermal insulation. Different strategies have been studied including direct injection of water into the extruder with surfactants, extrusion foaming of water expandable polystyrene (WEPS) beads, and feeding water containing activated carbon (WCAC)/polystyrene (PS) pellets. It was found that WCAC/PS pellets provided the most stable and clean extrusion process, more uniform cell morphology, and better thermal insulation than other methods. POLYM. ENG. SCI., 50:1577–1584, 2010. © 2010 Society of Plastics Engineers

Comparison of flow characteristics for dilute phase pneumatic conveying for two different plastic pellets

A series of dilute phase pneumatic conveying experiments using two different types of plastic pellets has led to the determination and development of distinguishing flow characteristics. Separate experiments on polystyrene and polyolefin pellets captured pressure-drop fluctuations and values at two different measuring points—one at the lower horizontal section of the transporting pipe and another at the upper section and at two different solid-loading ratios for each material. Also, comparison and analysis of the pressure-drop fluctuations and values obtained from the experiments were carried out under the same solid-loading ratio and blower rotational speed for both materials. Basic pressure drop calculations were made to find pressure drop due to pure gas, and that due to the presence of solids using a solid friction factor. In addition, the power spectral density analysis, and the wavelet analysis were conducted for both materials to evaluate the flow characteristics.

Cellular structures of carbon nanotubes in a polymer matrix improve properties relative to composites with dispersed nanotubes

A new processing method has been developed to combine a polymer and single wall carbon nanotubes (SWCNTs) to form electrically conductive composites with desirable rheological and mechanical properties. The process involves coating polystyrene (PS) pellets with SWCNTs and then hot pressing to make a contiguous, cellular SWCNT structure. By this method, the electrical percolation threshold decreases and the electrical conductivity increases significantly as compared to composites with well-dispersed SWCNTs. For example, a SWCNT/PS composite with 0.5wt% nanotubes made by this coated particle process (CPP) has an electrical conductivity of ∼3×10−4S/cm, while a well-dispersed composite made by a coagulation method with the same SWCNT amount has an electrical conductivity of only ∼10−8S/cm. The rheological properties of the composite with a macroscopic cellular SWCNT structure are comparable to PS, while the well-dispersed composite exhibits a solid-like behavior, indicating that the composites made by this new CPP are more processable. In addition, the mechanical properties of the CPP-made composite decrease only slightly, as compared with PS. Relative to the common approach of seeking better dispersion, this new fabrication method provides an important alternative means to higher electrical conductivity in SWCNT/polymer composites. Our straightforward particle coating and pressing method avoids organic solvents and is suitable for large-scale, inexpensive processing using a wide variety of polymers and nanoparticles.

Gradient blending of poly(dimethylsiloxane) with polystyrene and polyethylene in supercritical carbon dioxide

Direct impregnation and blending of poly(dimethysiloxane) (PDMS) with polystyrene and polyethylene has been investigated. Blends of polystyrene were prepared by first swelling and impregnation of polystyrene pellets in 0.1, 3 and 5 wt% solutions of PDMS in CO 2 at 80 °C and 45.7 MPa and then depressurization either directly at the impregnation temperature or after cooling to 50 or 27 °C. Blends of polyethylene were formed by impregnation at 130 °C and 57 MPa with 0.1 wt% PDMS solutions in CO 2 and depressurization at either 130 or 50 °C. The microstructural features of the blends were investigated by scanning electron microscopy (SEM). PDMS distribution across the pellet cross sections was investigated in terms of silicon atom distribution using energy dispersive X-ray (EDX) analysis. It is shown that the blends display pore-wise and compositionally gradient features. They typically show a steep compositional gradient, with a high PDMS concentration near the edge of the pellets which decrease and reach a plateau value a short distance away from the outer surface. In blends with polystyrene, when decompressions were carried out at temperatures lower than the impregnation temperature, the PDMS distributions were found to be significantly different, displaying a characteristic local maximum in the 20–100 μm range from the outer surface. In these blends, the SEM results show the formation of a dense non-porous layer with a thickness that corresponds closely with the location of the observed PDMS maximum, pointing to a competition between the vitrification of the host matrix and the escaping ability of PDMS dissolved in carbon dioxide before its entrapment during depressurization. At decompressions at the impregnation temperature, or with impregnations with PDMS solutions of higher concentrations, polystyrene pellets were found to expand more, and display a pore-gradient feature with layers of progressively increasing pore sizes from the outer edges towards the central region of the pellets. In blends of polyethylene, in contrast to polystyrene, the local maximum in PDMS concentration was not observed. The overall PDMS levels in the central region away from the outer surface were lower. The central region of the pellet showed a nanoporous morphology.

Wasp Attacks and Spider Defence in the Orb Weaving Species Zygiella x-notata

Predator–prey relationships are generally based on arm-race. Wasps and spiders are both predators, which could be potential prey for each other. The orb weaver spider Zygiella x-notata is sometimes a prey for the wasp Vespula germanica. We observed the wasp hunting behaviour under natural conditions, and we tested the influence of the spider’s behaviour on the wasp attack success. Wasps were active predators during the reproductive period of the spider. Results showed that wasps located more easily male spiders than females particularly when they were engaged in mate guarding. Female location depended on the presence of a web, but also of prey or prey remains in the web. On the other hand, their location depend neither on the characteristics and the position of the retreat in the environment nor on the size of the web. After location, males were more often captured than females whatever their behaviour (mate guarding or not). Presence of prey remains or prey in the web did not increase the risk for the spider to be captured. There was also no influence of the retreat’s characteristics or of its position in the habitat on the risk for the spider to be captured; but wasp successful attacks were less numerous when silk was present around the entrance of the retreat or when the spider was completely inside. As prey and prey remains favoured location of spiders by the wasps, we tested spider web cleaning behaviour as a response to wasp predatory pressure. By throwing small polystyrene pellets in the webs, we observed that more 80% of the spiders rejected the pellets in less than one minute. Our data indicated that wasps were significant predators of Z. x-notata and wasp attack could have been a selective pressure that had favoured spider defensive behaviours such as web cleaning.