Polypropylene Beads Research Articles

Effects of saturation temperature/pressure on melting behavior and cell structure of expanded polypropylene bead

The expanded polypropylene beads with microcellular structure were prepared by an autoclave-based batch foaming process using non-supercritical CO2 as the foaming agent. Herein, smaller polypropylene micropellets (∼0.6 mm) were obtained from three kinds of polypropylene resin by underwater micro-pelletizer system. The results from differential scanning calorimetry indicated that the double melting peaks of beads moved to higher temperature with increasing saturation temperature and pressure. The kind of comonomer did not exert noticeable influence on the double melting behaviors. The X-ray diffraction of expanded polypropylene bead revealed that characteristic peaks of α-type crystal did not change compared with that of original polypropylene micropellets. The relationship between cell morphology and saturation temperature/pressure of expanded polypropylene beads are discussed preliminarily by scanning electron microscope.

English

Nitrate is a major pollutant present in effluent wastewater from nitrogenous fertilizer, explosives, paper mills, pulp mills, and also from municipal waste. Nitrate is harmful to both mankind and animal and also to the environment. The World Health Organization has set a limit of 10 mg/L NO3 - for human consumption and 100 mg/l NO3 - for animals. Water above these limits requires denitrification. Nitrates causes cancer, blue-bay syndrome, hypertension and thyroid hypertrophy. Experimentation on biological denitrification was carried out in a fluidized bed bio-reactor using synthetic wastewater with polypropylene beads as supporting media for the growth of microorganism. Synthetic wastewater is taken into the reactor for biological treatment and air was fed from bottom with solids being fluidized at the top due to low density. Experiments were performed for water of different initial nitrate concentrations with Pseudomonas stutzeri microorganism by varying the parameters like airflow rate, temperature, carbon source, poly propylene beads and pH in the range 2 lpm to 3.5 lpm, 20 0C to 35 0 C, 70 mg/L to 85 mg/L, 5 mg/L to 25 mg/L and 6 to 8 respectively. The optimum parameters at which maximum denitrification is noticed are found to be 2.5 lpm (air flow rate), 30 0C (temperature), 85 mg/L (carbon source), 15 mg/L (poly propylene beads) and 7 (pH). More than 95% removal of nitrates is noticed from the experimental work. The objective of the study is to investigate the effect of operating parameters like airflow rate, temperature, carbon source, polypropylene beads and pH.

Simulation of Granular Transport of Geldart Type-A, -B, and -D Particles through a 90° Elbow

The flow behavior of three different classes of granular materials - pulverized coal particles (type-A), glass beads (type-B), and polypropylene beads (type-D) - is numerically investigated based on computational fluid dynamics. Three elbow geometries - square and circular (R/D = 1.5 and 3.0) - are employed to investigate turbulent gas-particulate flow in dilute and dilute-to-dense phase modes of pneumatic conveying. The unsteady Eulerian-Discrete phase approach with renormalized group (RNG) k-ε model is adopted, with the effects of particulate phase velocity on the gas flow, turbulent dispersion, lift forces, and particle-wall collisions incorporated in the model. The phenomenon of particle roping is well captured by the computations. Significant phase separation and particle segregation are observed in the vicinity of the lower wall of the pipe. Different classes of particles exhibit very distinct flow dynamics in terms of particle roping, particle segregation, turbulent dispersion, and particle velocity fluctuations. Numerical predictions for pressure drop, particle, and gas velocity profiles are in satisfactory agreement with experimental data from the literature.

Residence time distribution in spouted bed drying of maltodextrin solutions on a bed of inert particles

AbstractResidence time distributions (RTD) for aqueous maltodextrin solutions were determined in two kinds of spouted bed dryers: (1) conventional spouted bed (CSB) 0.305 m diameter with a bed of polypropylene beads and (2) spout‐fluid bed 0.143 m diameter with draft tube submerged in a bed of FEP® pellets (S‐FBDT). RTD, mean residence time tm, and spread of the distribution σ2, were determined at different drying temperatures, spouting velocities, bed depths, spraying pressures, and feed concentrations. Average values of tm and σ2 were 6.5 min and 26.6 min2 for the CSB and 6.9 min and 36 min2 for the S‐FBDT, respectively, for all operating conditions except spraying pressure. RTD curves were well represented by the response of an ideal stirred tank with a superimposed bypass of 15% on average for the CSB and 7% on average for the S‐FBDT dryer for all operating conditions. Increase in spraying pressure produced a reduction of tm and an increase in the bypass fraction of the product in both dryers. © 2011 Canadian Society for Chemical Engineering

Preparation of TiO 2 thin films on polypropylene beads by a rotating PCVD process and its application to organic pollutant removal

The TiO 2 thin films were coated on the polypropylene (PP) beads by a rotating cylindrical plasma chemical vapor deposition (PCVD) process and the photocatalytic activity of TiO 2 thin films was examined for the photodegradation of phenol in aqueous solution. The TiO 2 thin films grow more quickly on the PP beads with increasing the rotation speed of the reactor and with decreasing the number of PP beads. The photodegradation rate of phenol by TiO 2 thin films on the PP beads increases as the initial phenol concentration increases or as the number of PP beads coated with TiO 2 thin films increases in aqueous solution. The rotating cylindrical PCVD process can be a good method to coat the high-quality TiO 2 thin films on the particles. It is proposed that the particles coated with TiO 2 thin films can be applied to the removal of water pollutants with high efficiency.

Enhanced resistivity and breakdown strength via a granular two-phase silicone oil and polypropylene mixed media dielectric

A new granular two-phase mixed media insulator consisting of packed polypropylene beads and silicone oil is found to have up to 10 times greater resistivity and nearly 2 times greater breakdown strength compared with the same silicone oil when operated in DC mode.

APPLICATION OF PCVD PROCESS TO UNIFORM COATING OF TiO2 THIN FILMS ON POLYPROPYLENE BEADS

The growth of the TiO 2 thin films coated on the polypropylene beads was analyzed experimentally in a rotating cylindrical plasma chemical vapor deposition (PCVD) reactor. The precursors for the thin films were generated by plasma reactions, and they deposited on the polypropylene beads to become the uniform thin films. The TiO 2 thin films grow more quickly on the polypropylene beads by increasing the mass flow rate of TTIP, or the rotation speed of the reactor. The smaller number of polypropylene beads in the reactor increases the growth rate of the thin films. The high-quality TiO 2 thin films can be coated on particles uniformly by using the rotating cylindrical PCVD process. The particles coated with high-quality TiO 2 thin films can be applied to the removal of air and water pollutants by a photodegradation reaction of TiO 2.

Investigation on Flow Patterns and Transitions in a Multiple-Spouted Bed

Experimental studies on flow patterns and transitions were carried out in a visible multiple-spouted bed. The bed combines three spouted bed cells, each with a cross-section of 100 × 30 mm, and each cell has an independent spout nozzle of 10 mm in width. Polypropylene beads with a density of 900 kg/m3 and mean diameter of 2.8 mm were used as bed materials. Six distinct flow patterns, i.e., fixed bed (FB), internal jet (IJ), internal jet with bubble (IJB), single spouting (SS), multi-spouting (MS), and internal jet with slugging (IJS), were determined on the basis of criteria as well as schematic diagrams and typical flow pattern images obtained from a high-resolution digital charge coupled device (CCD) camera. Typical flow regime maps at three static bed heights were plotted to describe the transitions of flow patterns with central and auxiliary spouting gases. Besides, some important flow characteristics associated with flow patterns and transitions, i.e., minimum spouted velocity and pressure drop, were...

Generation of radical species on polypropylene by alkylborane‐oxygen system and its application to graft polymerization

AbstractGraft polymerization of ethyl acrylate and n‐butyl acrylate onto surface of polypropylene (PP) beads (diameter: 3.2 mm) were carried out by using a redox system composed of triethylborane (Et3B) and molecular oxygen in air. The amounts of the grafted polymers increased by prolonging a period of soaking PP beads in a solution of Et3B in hexane, a less polar solvent of which affinity with PP would be higher than that of tetrahydrofuran, a highly polar solvent. These results implied that the present graft polymerization involved: (1) interpenetration of Et3B into the surface area with the aid of hexane as a solvent, (2) its aerobic oxidation to generate a radical species, (3) abstraction of proton from PP by the radical species, and (4) initiation of polymerization from the resulting radical on the PP surface. Besides the acrylates, acrylic acid, and glycidyl methacrylate were also grafted onto the surface of PP to endow it with carboxyl and epoxy moieties, respectively. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6163–6167, 2009

A microwave‐assisted process for coating polymer and glass surfaces with semiconducting ZnO submicron particles

AbstractA new method for coating glass slides with ZnO particles with an average size of 200 nm is proposed in the current article. The coating was performed under microwave radiation. Two main morphologies are found for the ZnO crystals that are deposited on glass slides. The first morphology is that of a very dense coating of ZnO hexagonal rods growing perpendicular to the glass surface. The second is the growth of ZnO flower‐like particles. In addition to coating the glass by ZnO particles, we also report on coating other polymers [poly(methyl methacrylate) plate, polycarbonate beads, Nylon 6,6 beads, and polypropylene beads) by ZnO. The morphology obtained for ZnO coated on polymers is different from that detected for coating ZnO on glass. The unorganized coating of ZnO rods on polymers has been observed. The coated glass slides were characterized by X‐ray diffraction, volumetric titration, EDS, scanning electron microscope, and optical measurements (DRS and transmittance spectroscopy). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Media configuration and recirculation of upflow anaerobic floating filter for piggery wastewater treatment

An upflow anaerobic floating filter media (UAFF) reactor was applied to the treatment of synthetic and real piggery wastewater. The effect of media configuration and internal recirculation on the system performance was studied. In the first experiment, three-UAFF reactors filled with different media, i.e., polypropylene beads, sponge cubes and coconut fiber were continuously fed with synthetic wastewater at upflow velocity of 0.04 m h−1. The COD removal efficiency in the reactor filled with sponge cubes was highest at 90%, whereas the others filled with polypropylene beads and coconut fibers with lower specific surface area were about 80%. In the second experiment, three-UAFF reactors with sponge were applied to treat real piggery wastewater. COD removal efficiencies were found to be about 80% and methane production rate of 0.26 l lr−1d−1. The system performance could be slightly improved by 10% when applying internal recirculation. A sludge blanket (60–70% of total biomass) plays an important role in the system when applied to the treatment of piggery wastewater containing high suspended solid concentration.

Characterization of Bordetella pertussis growing as biofilm by chemical analysis and FT-IR spectroscopy

Although Bordetella pertussis, the etiologic agent of whooping cough, adheres and grows on the ciliated epithelium of the respiratory tract, it has been extensively studied only in liquid cultures. In this work, the phenotypic expression of B. pertussis in biofilm growth is described as a first approximation of events that may occur in the colonization of the host. The biofilm developed on polypropylene beads was monitored by chemical methods and Fourier transform infrared (FT-IR) spectroscopy. Analysis of cell envelopes revealed minimal differences in outer membrane protein (OMP) pattern and no variation of lipopolysaccharide (LPS) expression in biofilm compared with planktonically grown cells. Sessile cells exhibited a 2.4- to 3.0-fold higher carbohydrate/protein ratio compared with different types of planktonic cells. A 1.8-fold increased polysaccharide content with significantly increased hydrophilic characteristics was observed. FT-IR spectra of the biofilm cells showed higher intensity in the absorption bands assigned to polysaccharides (1,200-900 cm(-1) region) and vibrational modes of carboxylate groups (1,627, 1,405, and 1,373 cm(-1)) compared with the spectra of planktonic cells. In the biofilm matrix, uronic-acid-containing polysaccharides, proteins, and LPS were detected. The production of extracellular carbohydrates during biofilm growth was not associated with changes in the specific growth rate, growth phase, or oxygen limitation. It could represent an additional virulence factor that may help B. pertussis to evade host defenses.

Pneumatic transport of granular materials through a [formula omitted] bend

In the present study, a pneumatic conveying system incorporating a 90 ∘ bend is investigated. This study employs the use of three non-invasive instruments to measure solids concentration and velocity distribution determination in the pneumatic conveying system. They are namely the electrical capacitance tomography (ECT), particle image velocimetry and phase doppler particle analyzer. Pressure transducers were also used to monitor the pressure drop characteristics along the post-bend vertical pipe region. Two different classes of granular materials, polypropylene beads ( 2600 μ m , Geldart class D) and glass beads ( 500 μ m , Geldart class B), were used to investigate the differences in the flow characteristics for granular particles of various Geldart classes. The experimental results show a constant frequency pulsating flow for polypropylene beads in the dense-phase flow regime. This is illustrated by the visualization, ECT and pressure drop data. For dilute-phase flow regime, both polypropylene and glass beads show a continuous annulus flow structure. Numerical simulation using the Euler–Euler method was also conducted using computational fluid dynamics and the fluid and particle flow characteristics were compared with the experimental data obtained in the present study.

Drying of Liquid Feedstocks in a Spout‐Fluid‐Bed with Draft‐Tube Submerged in Inert Solids: Hydrodynamics and Drying Performance

AbstractA spout‐fluid bed with draft tube submerged in a bed of polypropylene beads was used for drying maltodextrin solutions. The hydrodynamics of the dryer were studied by determining the annular air flow vertical profile at different spouting velocities, using an additional air flow rate through the annulus equivalent to 0.5 Umf. The drying performance of the dryer was studied through the determination of several dryer response parameters (product moisture, evaporative capacity and volumetric evaporative capacity). These parameters were compared with those obtained in a conventional spouted bed with inert solids and a spray dryer.

Vacuum-driven lipase-catalysed direct condensation of l-ascorbic acid and fatty acids in ionic liquids: synthesis of a natural surface active antioxidant

L-Ascorbic acid (vitamin C) is a useful natural antioxidant, but is highly polar and does not dissolve in fats and oils. One solution is the synthesis of 6-O-L-ascorbyl fatty acid esters, which are surface-active and protect fats and oils from oxidation. Previous syntheses of 6-O-L-ascorbyl fatty acid esters by Candida antarctica lipase B (CAL-B)-catalysed esterification were inefficient due to either the poor solubility of L-ascorbic acid in nonpolar organic solvents or poor lipase activity in polar organic solvents. We report that replacing organic solvents with ionic liquids such as 1-alkyl-3-methylimidazolium tetrafluoroborates makes this synthesis more efficient and greener for three reasons. First, like polar organic solvents, ionic liquids dissolve polar substrates such as ascorbic acid (e.g., ∼130 mg mL−1 in sBMIM·BF4 at 60 °C), but unlike polar organic solvents, ionic liquids do not inactivate CAL-B. For this reason, using an ionic liquid as the solvent gave a faster reaction and a higher yield of product. Second, it eliminates toxic organic solvents that easily evaporate. Third, since ionic liquids are not volatile, we could use vacuum to drive the equilibrium toward product formation. This ability eliminated the need to use an excess of acyl donor or an activated acyl donor. One problem we encountered was product inhibition due to its precipitation on the immobilized lipase particles. To avoid this inhibition, we added a hydrophobic phase such as hexane or polypropylene beads. A CAL-B-catalysed direct esterification of stoichiometric amounts of ascorbic acid and oleic acid gave a high conversion (83%). The product 6-O-L-ascorbyl oleate was isolated as a mixture with oleic acid using only water and ethanol or methanol in 61% yield.

Design criteria for dense permeation-selective membranes for enantiomer separations

Dense enantioselective membranes can distinguish between two enantiomers by different mechanisms. At this moment, it is not clear which mechanism provides the best membranes for large-scale enantiomer separations. Therefore, we studied the design criteria for permeation-selective membranes combining literature data, experiments and model calculations. Literature data on dense permeation-selective membranes for enantiomer separation show that these membranes could be divided into two different classes: diffusion selective and sorption selective. Reviewing the literature on diffusion-selective membranes shows that these membranes have one main disadvantage: the inverse proportionality relation between the permeability and selectivity. This disadvantage is absent for sorption-selective membranes. As a model system, the diffusion of phenylalanine through a packed bed of polypropylene beads coated with N-dodecyl- l-hydroxyproline:Cu(II) was studied. The experiments showed that the material could selectively adsorb phenylalanine (Phe) with a selectivity ( d/ l) of 1.25. However, no permeation selectivity could be detected. With a dual sorption model these results could be interpreted. These model calculations showed that the permeation selectivity only approaches the intrinsic selectivity of the selector if the selectively adsorbed population is mobile and the non-selective permeation is minimized. Therefore, to our opinion more emphasis should be put on the development of sorption selective membranes.

High Rate Floating Medium Flocculation-Filtration with In-Line Polysilicato-Iron (PSI) Addition

The performance of a high rate floating medium flocculation-filtration system with an in-line addition of a silica-polymer compound, namely polysilicato-iron (PSI) has been investigated for water treatment. This study is intended to investigate the applicability of PSI as a sole flocculant or as a combined flocculant with an organic polymer in the downflow floating medium filter. The filter system was operated at a high loading rate of up to 60 m3 m−2 h−1. Filter column experiments were conducted at different PSI doses, filtration rates, filter depths and buoyant medium types and sizes. Results showed the filter system was able to yield uniform and filterable flocs (15 - 20 µm), even at a very high filtration rate of 60 m−3 h−1, through out the filter run time of 4 hours. Better filter performance was obtained when: (i) polystyrene beads of 1.9 mm diameter or polypropylene beads of 3.8 mm diameter; (ii) an in-line single dosage of 2.5 mg l−1 PSI; (iii) in-line combined dosages of 1.5 mg l−1 PSI and 0.4–0.6 mg l−1 organic polymers (cationic polyacrylamides, cationic polystyrene or Pollyallylamine hydrochloride) were used. When PSI was introduced as a sole flocculant, more than 90% turbidity was removed from a 54 NTU artificial kaolin clay suspension at a filtration rate of 30 m−3 m−2h−1 with very low headloss development. Greater removals were achieved when SIF was used in combination with a polymer (e.g.greater than 95% turbidity removal). Frequent (once in every 90 minutes) but short duration backwash (less than 60 s) by air and water enables the system to maintain a superior effluent quality (e.g. turbidity less than 1 NTU) during the filter run. Backwash water requirement was very low (approximately 1%-2% of filtered water production). A lower amount of sludge was produced from the filter in case of combined PSI and organic polymer coagulant addition.

An enhancement of critical flux in crossflow microfiltration with a pretreatment of floating medium flocculator/prefilter

In this study, use of a combined system of flocculation-microfiltration was assessed for its capability in removing solids and organics. The improvement of flux by the preflocculation was also investigated. The experimental set-up consisted of (i) Millipore flat plate microfiltration module with constant permeate withdrawal arrangement and (ii) a floating medium flocculator/filter consisting of polypropylene beads as a pretreatment. Commercial ferric chloride(FeCl3) was used for flocculation. The purpose of floating medium filter was primarily to produce filterable flocs and also to achieve partial solids and organics removal. The critical flux of kaolin clay suspension of 10–100mg/L was measured for membrane of pore size of 0.2μm in the presence of 0–4mg/L of fulvic acid in the suspension without any pretreatment. The critical flux was found to decrease with the increase in kaolin clay concentration. The results also indicated that there was no significant effect of organic (fulvic acid) concentration on critical flux. The pretreatment of floating medium filter alone without flocculant addition removed 30–40% of solids and resulted in a significant improvement of critical flux in crossflow microfiltration. Degree of solids and organic removal and the variation in critical flux were then studied in detail for the preflocculated/filtered kaolin clay suspension in the presence of organics. The pretreatment of flocculation/prefiltration removed approximately 50% of organics while producing uniform microflocs of 13–16 μm size. In addition, it enhanced the critical flux by 70% and resulted in 30–70% of the remaining organic removal in the crossflow microfiltration.

Dielectric relaxations in liquid-impregnated porous solids

We have studied dielectric relaxation in liquid-impregnated porous solids. The samples were constructed from either glued sand grains or sintered polypropylene beads. We experimentally obtain two relaxations originating from the bulk of the sample. Electrode effects are seen at low frequencies, only for high liquid conductivities. The two bulk relaxations are interpreted as being due to diffusion in the electrochemical double layer surrounding the solid grains, and as a Maxwell–Wagner relaxation due to the heterogeneity of the samples, respectively. The experimental results can be qualitatively reproduced by calculations using the grain consolidation model, which was extended to take into account interfacial effects. The permittivity at high (megahertz) frequencies can be understood by using simple mixing laws. We also propose an equivalent circuit for the electrical properties of a liquid-impregnated porous solid.

An enhancement of critical flux in crossflow microfiltration with a pretreatment of floating medium flocculator/prefilter

In this study, use of a combined system of flocculation-microfiltration was assessed for its capability in removing solids and organics. The improvement of flux by the preflocculation was also investigated. The experimental set-up consisted of (i) Millipore flat plate microfiltration module with constant permeate withdrawal arrangement and (ii) a floating medium flocculator/filter consisting of polypropylene beads as a pretreatment. Commercial ferric chloride(FeCl3) was used for flocculation. The purpose of floating medium filter was primarily to produce filterable flocs and also to achieve partial solids and organics removal. The critical flux of kaolin clay suspension of 10 – 100mg/L was measured for membrane of pore size of 0.2μm in the presence of 0 – 4mg/L of fulvic acid in the suspension without any pretreatment. The critical flux was found to decrease with the increase in kaolin clay concentration. The results also indicated that there was no significant effect of organic (fulvic acid) concentration on critical flux. The pretreatment of floating medium filter alone without flocculant addition removed 30 – 40% of solids and resulted in a significant improvement of critical flux in crossflow microfiltration. Degree of solids and organic removal and the variation in critical flux were then studied in detail for the preflocculated/filtered kaolin clay suspension in the presence of organics. The pretreatment of flocculation/prefiltration removed approximately 50% of organics while producing uniform microflocs of 13 – 16μm size. In addition, it enhanced the critical flux by 70% and resulted in 30 – 70% of the remaining organic removal in the crossflow microfiltration.