Polyethylene

The kinetics of abiotic oxidation in the dark and the kinetics of biological mineralization in soil and in a compost environment of thermally oxidized LDPE were studied. It was demonstrated that different activation energies are obtained for the thermal oxidation, depending on the composition of the materials. Significantly higher levels of biodegradability have been obtained in a soil environment at 23 C compared with the compost environment at 58 C. After two years of mineralization, 91% conversion to carbon dioxide was obtained in the soil test, compared with 43% in the compost test. The differences between fungal, archaeal and bacterial community structures in soil and compost after 607 days of biodegradability assay were mapped out. It was found that the most dominant bacterial and fungal terminal restriction fragments (TRFs) in the compost containing the test material are significantly different from the TRFs in the other environments.

In this paper, a study on the batch processing and characterization of microcellular foamed high-density polyethylene (HDPE/iPP) blends is reported. A microcellular plastic is a foamed polymer with a cell density greater than 109 cells/cm3 and fully grown cells smaller than 10 µm. Recent studies have shown that the morphology and crystallinity of semicrystalline polymers have a great influence on the solubility and diffusivity of the blowing agent and on the cellular structure of the resulting foam in microcellular batch processing. In this research, blends of HDPE and iPP were used to produce materials with variety of crystalline and phase morphologies to enhance the subsequent microcellular foaming. It was possible to produce much finer and more uniform foams with the blends than with neat HDPE and iPP. Moreover, the mechanical properties and in particular the impact strength of the blends were significantly improved by foaming.
(citation # 293)

An experimental research is presented aimed at determine the effect of disinfectants on high density polyethylene (HDPE) pipes, commonly employed in modern urban networks for water conveyance. The test campaign is oriented to the analysis of PE100, for alimentary use, with a nominal diameter DN 32. The effect of sodium hypochlorite at a constant concentration of 2.5 ppm is investigated, by applying non severe environmental conditions. The exposure is performed through an experimental plant specifically implemented, which consists of two separate lines, a chlorinated and a neutral one. On each line both samples from the pipe and dog bone specimens can be simultaneously exposed. A comparison is presented between the results of this test campaign and a former one investigating the effect of chlorine dioxide. It is shown that chlorine dioxide is much more aggressive on polyethylene than sodium hypochlorite. The mechanical properties of the pipe, however, are not affected by both type of disinfectants as testified by tensile tests and pressure tests at constant temperature. A fast and simple mechanical characterization by means of ring specimens is also investigated.

The present investigation was carried out to study the effect of different concentrations of calcium chloride (1%, 1.5%, 2%), paraffin wax coating and different wrapping materials (polyethylene, carton paper) inorder to increase the shelf life and to avoid the postharvest losses of Banky cultivars of apple. In physical characteristics general appearance (color and shape of fruit), weight loss percentage and

Lignin powder, obtained from an abundant and low cost source, straw, through a low environmental impact process, the steam explosion, is used for the preparation of blends with low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE) and atactic polystyrene (PS).

In the field of FTIR spectroscopy, the far infrared (FIR) spectral region has been so far less investigated than the mid-infrared (MIR), even though it presents great advantages in the characterization of those inorganic compounds, which are inactive in the MIR, such as some art pigments, corrosion products, etc. Furthermore, FIR spectroscopy is complementary to Raman spectroscopy if the fluorescence effects caused by the latter analytical technique are considered. In this paper, ATR in the FIR region is proposed as an alternative method to transmission for the analyses of pigments. This methodology was selected in order to reduce the sample amount needed for analysis, which is a must when examining cultural heritage materials. A selection of pigments have been analyzed in both ATR and transmission mode, and the resulting spectra were compared with each other. To better perform this comparison, an evaluation of the possible effect induced by the thermal treatment needed for the preparation of the polyethylene pellets on the transmission spectra of the samples has been carried out. Therefore, pigments have been analyzed in ATR mode before and after heating them at the same temperature employed for the polyethylene pellet preparation. The results showed that while the heating treatment causes only small changes in the intensity of some bands, the ATR spectra were characterized by differences in both intensity and band shifts towards lower frequencies if compared with those recorded in transmission mode. All pigments' transmission and ATR spectra are presented and discussed, and the ATR method was validated on a real case study.

Diffusion coefficient Lipid oxidation Whole milk powder a b s t r a c t Antioxidant active packaging is a promising technology for whole milk powder (WMP) protection. In this study, the migration of a-tocopherol from a multilayer active packaging (made of high density polyethylene, ethylene vinyl alcohol and a layer of low density polyethylene containing the antioxidant) to WMP was studied. A model based on the Fick's diffusion equation was used to calculate the diffusion coefficients (D) of a-tocopherol as 2.34 Â 10 À11 , 3.06 Â 10 À11 , and 3.14 Â 10 À11 cm 2 s À1 at 20, 30 and 40°C, respectively. The D at 20°C was different from those at 30 and 40°C (P < 0.05); but it was similar at 30 and 40°C. This low influence of temperature on the migration of a-tocopherol from 20 to 40°C assures the release at real storage and commercialization conditions in regions with warm/hot climate. The antioxidant delivering system delayed the lipid oxidation of WMP and it was more effective at 30 and 40°C since the rate of oxidative reactions was higher at these temperatures than at 20°C.

HDPE Aspergillus tubingensis VRKPT1 Aspergillus flavus VRKPT2 Fourier transformed infra-red spectroscopy Scanning electron microscopy a b s t r a c t High density polyethylene (HDPE) is the most commonly found non-degradable solid waste among the polyethylene. In this present study, HDPE degrading various fungal strains were isolated from the polyethylene waste dumped marine coastal area and screened under in vitro condition. Based on weight loss and FT-IR Spectrophotometric analysis, two fungal strains designated as VRKPT1 and VRKPT2 were found to be efficient in HDPE degradation. Through the sequence analysis of ITS region homology, the isolated fungi were identified as Aspergillus tubingensis VRKPT1 and Aspergillus flavus VRKPT2. The biofilm formation observed under epifluorescent microscope had shown the viability of fungal strains even after one month of incubation. The biodegradation of HDPE film nature was further investigated through SEM analysis. HDPE poses severe environmental threats and hence the ability of fungal isolates was proved to utilize virgin polyethylene as the carbon source without any pre-treatment and pro-oxidant additives.

aspects of porous polyethylene implant placement. The authors have retrospectively analyzed 136 cases of evisceration, enucleation, and secondary porous polyethylene implant placement and have concluded that there is no significant difference in exposure rates between wrapped and unwrapped implants.

Results of long-term hydrostatic strength study of piping systems made from polyethylene with increased temperature resistance PERT type II of Hostalen 4731B without reinforcement are presented and discussed in this paper. The different approximations of durability curves and various equivalent stress measures are considered and compared. An analytical expression for the maximum allowable internal pressure as function of service life of pipes, temperature, geometrical parameters of pipe cross-section and material properties is given. Pipes without reinforcement with nominal outer diameters from 32 mm to 225 mm were analyzed to assess long-term hydrostatic strength using equivalent stress, provided that there is no change in mechanism of damage accumulation. This allowed us to use linear extrapolation into area of long service life. The results indicate possible use of pipes SDR7.4 in heating networks for 50 years with heat transfer fluid parameters of 95 °C and internal pressure of 1 MPa.

The Present work includes, degradation of polyethylene under different environmental conditions to know the effect of physical, chemical and biological factors prevailing in those conditions on degradation of polyethylene. Plastic films viz., Low density polyethylene (LDPE), High density polyethylene (HDPE) and High molecular weight high density polyethylene (HMHDPE) each were incubated in three different conditions viz., black soil, sandy soil and red soil for a period of 3 months. The changes in the properties of plastic films after incubation was studied by change in the weight of the plastic film and mechanical parameters like tensile strength, breaking load and percentage of elongation. Among all the plastic films HDPE was found to be highly susceptible with 33% weight loss and 40% reduction in percentage of elongation compared to LDPE with 26% weight loss and 34 % reduction in percentage of elongation in black soil. Whereas HMHDPE found to be highly resistant in all the soils with no significant weight loss and percentage of elongation (15%). None of the plastic films had shown degradation in sandy soil even after incubation for 3 months. FTIR spectroscopy results showed that HDPE film incubated in black soil had undergone extensive degradation when compared with un incubated HDPE film.

The electrical resistivity of crosslinked high-density polyethylene loaded with conductive blacks and carbon fibers was studied as a function of filler concentration and temperature. A thermoelectric switching phenomenon (a sudden resistivity increase in the vicinity of the polyethylene melting point) in such semicrystalline conductive systems was investigated. Significant switching properties were found only in compounds useful in the medium conductivity range. A significant switching behavior was exhibited by compounds containing very low concentrations of carbon fibers. Some crosslinked compounds filled with mixtures of carbon black and carbon fibers were also studied. EXPERIMENTAL Compounds of polyethylene, carbon black, or carbon fibers, and peroxide were compression-molded at 190-200°C giving about 3 mm thick plaques. Radiation crosslinking was done by irradiating thermoplastic plaques with a Co60 source

This paper is devoted to investigation of morphological and physical-mechanical properties of polyethylene (PE)/clay nanocomposites prepared via in situ polymerization method using bi-supported Ziegler-Natta catalyst. Bentonite type clay and MgCl 2 (ethoxide type) were used as the support of TiCl 4. Catalyst support and polymerization process have been done in slurry phase using Triisobutylaluminum as the cocatalyst. The microstructure of the nanocomposites was examined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD and TEM indicated that almost fully exfoliated PE/clay nanocomposites were produced successfully using this method. According to permeability measurements, it was found that oxygen permeability values of the nanocomposite samples prepared with in situ polymerization method were dropped more than 200% introducing only 1 wt% clay to polymeric matrix. Differential scanning calorimetry (DSC) results indicated that the crystallization temperatures of samples are significantly higher than that of virgin PE. Moderate thermal stability enhancement of in situ polymerized nanocomposites was confirmed using thermogravimetric analysis (TGA).The storage modulus, Young's modulus and tensile strength of prepared samples were increased where the toughness was declined slightly. It seems that good dispersion and exfoliation of clay during polymerization should be responsible to get more effective reinforcing properties for clay in this method comparing to melt blending method for preparation of polyethylene nanocomposites.

In an industrial gas-phase polyethylene reactor, the safe operating range of temperature is rather narrow. Even within this temperature range, temperature excursions must be avoided because they can result in low catalyst productivity and significant changes in product properties. In previous work, using a first-principles model, including the recycle stream and the heat exchange system, a PID temperature controller with robust performance was designed via optimization in the frequency domain for different operating points. For the reactor total pressure, ethylene partial pressure, H2/C2 and C4/C2 molar ratios, PI controllers were designed. In the PID temperature controller, if the manipulated variable (cooling water valve opening) saturates then the reactor operates without a feedback temperature controller, leading to oscillatory behaviour and limit cycles. It has been demonstrated that the manipulated variable saturation and the nonlinear dynamic behaviour are removed when auxiliary manipulated variables, obtained by bifurcation analysis, are used in a multivariable control strategy for the reactor temperature control. In this work, two control structures are compared to define the most suitable proposal for implementation in an industrial reactor and the impact of these control structures in the reactor production and in the polymer melt index are analyzed. The first control structure considers the control problem using the designed PID controller for the reactor temperature and includes a switching strategy with a PI controller for the auxiliary manipulated variables. The second control structure considers the control problem also using the designed PID controller for the reactor temperature, however including a MPC controller for the auxiliary manipulated variables.

Electrochemical insertion of sodium ions into carbon using solid polymer electrolytes or organic liquid electrolytes is described. Cells with the configuration Na/P(EO)sNaCF3SOJCP(EO) = polyethylene oxide) or Na/liquid electrolyte/C were galvanostatically discharged, charged, and cycled. The extent of insertion into C (Le., x in Na § was found to be a strong function of the type and particle size of the carbon used, and the reversibility of the process was highly dependent upon the type of electrolyte used. The possibility of designing a sodium ion rocking chair cell is discussed, and a first-generation example, using a petroleum coke anode, polymer electrolyte, and sodium cobalt bronze cathode is described.

Post-herpetic neuralgia (PHN) is a common and often intractable neuropathic pain syndrome predominantly affecting the elderly. Topical local aneslthetics have shown promise in both uncontrolled and controlled studies. Thirty-five subjects with established PHN affecting the torso or extremities completed a four-session, random order, double-blind, vehicle-controlled study of the analgesic effects of topically applied 5% lidocaine in the form of a non-woven polyethylene adhesive patch. All subjects had allodynia on examination. Up to 3 patches, covering a maximum of 420 cm 2, were applied to cover the area of greatest pain as fully as possible. Lidocaine containing patches were applied in two of the four 12-h-long sessions, in one session vehicle patches were applied, and one session was a no-treatment observation session. Lidocaine containing patches significantly reduced pain intensity at all time points 30 rain to 12 h compared to no-treatment observation, and at all time points 4-12 h compared to vehicle patches. Lidocaine patches were superior to both no-treatment observation and vehicle patches in averaged category pain relief scores. The highest blood lidocaine level measured was 0.1 /xg/ml, indicating minimal systemic absorption of lidocaine. Patch application was without systemic side effects and well tolerated when applied on aUodynic skin for 12 h. This study demonstrates that topical 5% lidocaine in patch form is easy to use and relieves post-herpetic neuralgia.

We examine the effect of mulches on the soil volumetric water content (SVWC), pH, carbon (C), total and mineral (NH 4 and NO 3 ) nitrogen (N), total and bicarbonate phosphorus (P), and on the survival and relative growth rate of three species, Ipomea wolcottiana Rose, Lonchocarpus eriocarinalis Micheli and Caesalpinia eriostachys Benth, in a degraded seasonally dry tropical forest (SDTF) area. Our study year was unusually dry, with only half of the mean annual rainfall. Sixteen plots (5 · 6 m) for each of our four treatments, mulches with alfalfa (Medicago sativa L.) straw, forest litter (SDTF litter), polyethylene and bare soil (control), were used. In each plot, 20 tree saplings were planted of each species. The SVWC was higher in plots mulched with polyethylene than in bare soil plots. The soil pH did not change with mulching, and there were no differences between treatments in the concentrations of soil organic C, total N, NO 3 and total P. However, soil concentrations of NH 4 were highest in plots with alfalfa straw and of bicarbonate P in plots with polyethylene. Sapling survival was higher in polyethylene mulch plots than in other mulching treatments, in the order I. wolcottiana > C. eriostachys > L. eriocarinalis. Sapling survival under organic mulches, alfalfa straw and forest litter were similar, and lowest in bare soil. The relative growth rate followed the order L. eriocarinalis < C. eriostachys < I. wolcotiana, and the growth rate of all species was greatest under polyethylene mulch. We conclude that a combination of polyethylene mulch with species of high growth rate is best for restoring seasonally dry tropical areas.

The objective of this study was to investigate the outcome of revision total knee arthroplasty (TKA) in relation to the cause of index failure, the characteristics of the index procedure, and the elapsed time between index TKA and revision. A retrospective review based on a prospective database was performed on 146 consecutive revision TKA&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s. Variables tested were the cause of index failure; the elapsed time between the index and revision procedure; patient age at time of revision; partial or total revision of the implants; the performance of a tibial tubercle osteotomy; the presence of radiolucent lines; postoperative patellar tracking; and coronal plane alignment. Outcomes were measured with the Knee Society Knee Score (KS), Function Score (FS), and X-ray evaluation. Mean KS improved from 27.6 (SD 21.6) to 71.5 (SD 24.2) after revision (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.0001), mean FS from 27.5 (SD 22.7) to 53.3 (SD27.7), P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.0001. Overall survival rate was 90% at 5 years and 85% at 10 and 14 years. The cause of index failure had no significant influence on any of the outcome parameters. Significantly, better outcomes were noted for partial revisions and for revisions in older patients. Early revisions (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;2 years) were mostly performed for infection and instability, whereas late revisions (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;2 years) were mostly performed for polyethylene wear and loosening. The survival rate for late revisions was significantly better than for early revisions (P = 0.002). Revision TKA leads to a significant reduction in symptoms and improvement in function. The worst results can be expected for early revisions in young patients. Revision TKA is a demanding procedure with variable results and should therefore be performed by experienced surgeons. Therapeutic study-Level IV.

Chemicals effect from the environment and liquid chemicals (diesel and petrol) on rotational molding grade (HD3840UA) high density polyethylene (HDPE) and cross-linked HDPE samples were studied according to ASTM ISO 175: 1999. The HDPE (pure) and cross-linked HDPE samples with various antioxidant concentrations (0.0%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%) were prepared. Samples were immersed in the liquid chemicals at 23 o C for the immersion test. The weathering test was conducted to study the effected of chemical in the environment by exposing the samples to the natural atmosphere. The duration of the test is 1 day, 1 week and 8 weeks. Tensile test was carried out according to ASTM D638-02 to determine the stress at break, elongation at break and Young's Modulus. The changes in weight and dimension were also determined. The tensile properties result show that the rate of degradation for the petrol immersion is more than diesel immersion at 23 o C for both HDPE and cross-linked HDPE samples. Both samples experienced apparent reduction in the tensile properties within 24 hours, regardless of antioxidant concentrations. Physically the sample immersed in diesel shows a higher swelling ratio. The HDPE is more susceptible to liquid chemical as well as atmospheric attack. The cross-linked HDPE with optimum level of antioxidant contents is the most stable towards liquid chemical and environmental attack. Ke-V Hotel Residenc, 23-24 Ogos 2005 weather factor, including solar radiation, heat/cold, moisture (solid, liquid and vapor), oxygen and atmospheric contaminants not only on the polymeric itself but also other components within the matrix such as additives, dyes and stabilizers . Common air pollutants include sulfur oxides, hydrocarbons, nitrogen oxides and particulate matter such as sand, dust, dirt and soot. Some of these may react with organic materials but have a much more severe effect in combination with other factors. Example rapid discoloration of pigments as well as crosslinking and embitterment of material. The deterioration, chemically and environmentally, depends on the specific wavelength and amount of solar radiation the polymer are capable of absorbing. The strength of their chemical bonds in relation to the photon energies of the solar radiation absorbed and the reaction processes promoted by heat, moisture (including chemical contaminants) and other factors following bond breakage. Complex interactions of the combination of the environment factors with the polymer and its components result in irreversible exposure changes in the chemical structures and physical properties that generally changes both the appearance and mechanical properties and reduces the useful life of the material [3]. High density polyethylene (HDPE) upon weathering and liquid chemical imposes property defects or deterioration.

HDPE/iron powder composites have been characterized from the point of view of mechanical, thermal and electrical properties. Results for iron powder contents varying between 0 and 24 % by volume are presented. Generally, the composites show poorer mechanical properties as compared with the unfilled polymer. The density and hardness of HDPE/iron composites are higher than those of HDPE. The incorporation of iron powder in HDPE increases the thermal diffusivity and conductivity and decreases the specific heat and the electrical resistivity. The experimental data were interpreted using appropriate theoretical models.

The blends of poly(ethylene naphthalate) (PEN) and poly(ethylene terephthalate) (PET) were obtained by melt blending at 3108C for 2 min and quenching into an ice water. Mechanical properties and structural formation of unoriented amorphous PEN/PET blend ®lms during drawing at 85, 100 and 1308C were studied by tensile tests and in situ X-ray measurements. The results obtained were compared with the pure PEN and PET. The PET ®lm could not be drawn due to partial melt at above 1008C and a lower drawing rate but the ®lm blended with PEN was possible to be drawn. The crystallization of PEN/PET blend during drawing proceeded gradually due to the effect of PET at 1008C though the crystalline re¯ections in the crystallization of pure PEN appeared suddenly by necking. This was evidenced by the formation of a-form crystalline re¯ections of PEN as detected by in situ X-ray measurements.

Stretched polyethylene (PE) films have been used to orient small molecules for decades by depositing solutions on their surface and allowing the solvent to evaporate leaving the analyte absorbed on the polymer film. However, the non-polar hydrophobic nature of PE is an obstacle to aligning polar molecules and biological samples. In this work PE film was treated with oxygen plasma in order to increase surface hydrophilicity. Different treatment conditions were evaluated using contact angle measurement and X-ray photoelectron spectroscopy. Treated PE (PE OX ) films are shown to be able to align molecules of different polarities including progesterone, 1-pyrenecarboxaldehyde, 4 0 ,6-diamidino-2-phenylindole (DAPI) and anthracene. The degree of alignment of each molecule was studied by running series of linear dichroism (LD) experiments and the polarizations of electronic transition moments were determined. For the first time optimal conditions (such as stretching factor and concentration of the sample) for stretched film LD were determined. PE OX aligning ability was compared to that of normal PE films. Progesterone showed a slightly better alignment on PE OX than PE.

Growth and osmotic potential of calli induced from leaf- and root-derived tissues of six tepary bean lines (Phaseolus acutifolius) varying in drought resistance were assessed in vitro after polyethylene glycol-induced (10%, PEG-10,000) dehydration. Calli of resistant teparies were characterized by low initial osmotic potential (ψs) and relative growth rate (RGR) on medium lacking PEG (−0.30 MPa). However, calli of both resistant and sensitive lines were similar in dry matter percent (DM). Presence of PEG in the medium (−0.58 MPa) elevated DM in all teparies except one resistant line. Both leaf- and root-derived calli of sensitive teparies exhibited osmotic adjustment (OA) but reduced RGR that remained after rehydration in one line. We concluded that preexisting force of low cellular ψs rather than induced OA plays an important role in buffering adverse effects of dehydration and conditioning drought resistance of tepary beans. This information may aid Phaseolus breeders in screening for drought resistance among large number of accessions.

In the present study a series of polyethylene/plasticized starch blends were prepared using a poly(ethylene-g-maleic anhydride) copolymer as a reactive compatibilizer. Uncompatibilized blends were also prepared for comparison purposes. The prepared blends were studied using mechanical properties measurements and SEM microscopy to determine their morphology. The blends were also exposed to activated sludge to determine their biodegradability. 0 1998 Elsevier Science Limited. All rights reserved

We have measured charged nuclear fragments produced by 1 GeV/nucleon 56 Fe ions interacting with aluminium, polyethylene and lead. These materials are relevant for assessment of radiation risk for manned space flight. The data will be presented in a form suitable for comparison with models of nuclear fragmentation and transport, including linear energy transfer (LET) spectrum, fluence for iron and fragments, event-tack-and event-dose-averaged LET, total dose and iron contribution to dose. Ó 2005 Published by Elsevier Ltd on behalf of COSPAR.

With 5-7 month long duration missions at 51.6°inclination in Low Earth Orbit, the ionizing radiation levels to which International Space Station (ISS) crewmembers are exposed will be the highest planned occupational exposures in the world. Even with the expectation that regulatory dose limits will not be exceeded during a single tour of duty aboard the ISS, the ''as low as reasonably achievable'' (ALARA) precept requires that radiological risks be minimized when possible through a dose optimization process. Judicious placement of efficient shielding materials in locations where crewmembers sleep, rest, or work is an important means for implementing ALARA for spaceflight. Polyethylene (C n H n ) is a relatively inexpensive, stable, and, with a low atomic number, an effective shielding material that has been certified for use aboard the ISS. Several designs for placement of slabs or walls of polyethylene have been evaluated for radiation exposure reduction in the Crew Quarters (CQ) of the Zvezda (Star) Service Module. Optimization of shield designs relies on accurate characterization of the expected primary and secondary particle environment and modeling of the predicted radiobiological responses of critical organs and tissues. Results of the studies shown herein indicate that 20% or more reduction in equivalent dose to the CQ occupant is achievable. These results suggest that shielding design and risk analysis are necessary measures for reducing long-term radiological risks to ISS inhabitants and for meeting legal ALARA requirements. Verification of shield concepts requires results from specific designs to be compared with onboard dosimetry.

In this study, we quantified the adsorption of immunoglobulin G (IgG) protein onto several polyelectrolyte-modified sintered porous polyethylene (PPE) membranes. The polymer surfaces had both cationic and anionic charges obtained via the adsorption of polyethylenimine (PEI) and polyacrylic acid (PAA), respectively, onto plasma-activated PPE. The amount of IgG adsorption was determined by measuring the gamma radiation emitted by [ 125 I]-IgG radio labeled protein. By studying the impact of pH and ionic strength on IgG adsorption, we attempted to characterize the role and nature of the electrostatic interactions involved in the adsorption process to better understand how these interactions were influenced by the charge and structure of immobilized polyelectrolyte complexes at modified membrane surfaces. We were able to show that surface modification of PPE membranes with adsorbed PEI monolayers and PEI-PAA bilayers can greatly improve the IgG binding ability of the membrane under optimized conditions. We also showed that the observed improvement in the IgG binding is derived from electrostatic interactions between IgG and the polyelectrolyte surface. In addition, we found that the greatest IgG adsorption occurred when the IgG and the surface possessed predominantly opposite charges, rather than when the surface possessed the greatest electrostatic charge. Finally, we have found that the molecular weight of the terminating polyelectrolyte has a noticeable effect upon the electrostatic interactions between IgG and the PEI-PAA bilayer-modified PPE surfaces. r

The mechanical performance of Spectra 900 and Spectra 1000 fibers subjected to either glow-discharge or chemical etch treatments was evaluated with respect to untreated control fibers. Tensile strength measurements were carried out at different gauge lengths. The interfacial shear strength between these fibers and an epoxy resin (Epon 815) was determined by means of fiber pull-out tests. It was found that tensile behavior is insensitive to gauge lengths greater than 20 mm, that glow-discharge treatment improves interfacial adhesion, but at the cost of significant loss in tensile strength, and that chemical etching of these fibers in an aqua regiu bath increases the interfacial bonding to epoxy resin by about 5OVo without significantly decreasing the fiber strength. Tensile results for an epoxy resin reinforced with short Spectra 1000 fibers indicated that no reinforcing effect is obtained for the control. However, an increased interfacial bond strength brought about by chemical etching resulted in improved tensile performance for composite systems reinforced with treated fibers.

This paper quantifies the main impacts that the adoption of the best recycling practices together with a reduction in the consumption of single-use plastic bags and the adoption of a kerbside collection system could have on the 27 Member States of the EU. The main consequences in terms of employment, waste management costs, emissions and energy use have been quantified for two scenarios of polyethylene (PE) waste production and recycling. That is to say, a "business as usual scenario", where the 2012 performances of PE waste production and recycling are extrapolated to 2020, is compared to a "best practice scenario", where the best available recycling practices are modelled together with the possible adoption of the amended Packaging and Packaging Waste Directive related to the consumption of single-use plastic bags and the implementation of a kerbside collection system. The main results show that socioeconomic and environmental benefits can be generated across the EU by the implementation of the best practice scenario. In particular, estimations show a possible reduction of 4.4 million tonnes of non-recycled PE waste, together with a reduction of around €90 million in waste management costs in 2020 for the best practice scenario versus the business as usual scenario. An additional 35,622 jobs are also expected to be created. In environmental terms, the quantity of CO2 equivalent emissions could be reduced by around 1.46 million tonnes and the net energy requirements are expected to increase by 16.5 million GJ as a consequence of the reduction in the energy produced from waste. The main analysis provided in this paper, together with the data and the model presented, can be useful to identify the possible costs and benefits that the implementation of PE waste policies and Directives could generate for the EU.

The bone morphogenetic proteins (BMPs) are cytokines of the transforming growth factor beta family. Some BMPs such as BMP-2, BMP-7 and BMP-9 play a major role in the bone and cartilage formation. The BMP peptides corresponding to residues 73e92, 89e117, and 68e87 of BMP-2, BMP-7 and BMP-9 respectively as well as adhesion peptides (GRGDSPC) were grafted onto polyethylene terephthatalate (PET) surfaces. We evaluated the state of differentiation of pre-osteoblastic cells. The behavior of these cells on various functionalized surfaces highlighted the activity of the mimetic peptides immobilized on surfaces. The induced cells (observed in the case of surfaces grafted with BMP-2, 7 or 9 mimetic peptides and GRGDSPC peptides) were characterized on several levels. First of all, we focused on the evaluation of the osteoblastic markers such as the transcriptional factor Runx2, which is a critical regulator of osteoblastic differentiation. Secondly, the results obtained showed that these induced cells take a different morphology compared to the cells in a state of proliferation or in a state of extracellular matrix production. Induced cells were characterized by an increased thickness compared to non-induced cells. Thus, our studies prove a direct correlation between cell morphology and state of induction. Thereafter, we focused on characterizing the extracellular matrix formed by the cells on various surfaces. The extracellular matrix thickness was more significant in the case of surfaces grafted with mimetic peptides of the BMP-2, 7 or 9 and GRGDSPC peptides which once again proves their activity when immobilized on material surface. These results demonstrate that GRGDSPC and BMPs peptides, grafted to PET surface, act to enhance osteogenic differentiation and mineralization of pre-osteoblastic cells. These findings are potentially useful in developing engineered biomaterials for bone regeneration.

The combination of organophillised montmorillonite (MMT), synthetic hydromagnesite and aluminium hydroxide (ATH) as flame retardant system for polyethylene-based materials was studied and compared with a similar system with magnesium hydroxide, ATH and MMT. The thermal stability and the flame retardant properties were evaluated by thermogravimetric analysis (TGA), differential thermal analysis (DTA), limiting oxygen index (LOI) and cone calorimeter tests. The results indicated that the addition of montmorillonite makes it possible to reduce the total filler content to achieve the flame retardant requirements. The thermal stability of filled LDPE/EVA blends increases to a higher extent for the samples containing MMT. In the cone calorimeter tests we observed a reduction of the peak heat release rate for the sample containing montmorillonite in comparison with a sample with higher filler loading without this nanoclay. An increase of the stability of the char formed could be responsible for this favourable behaviour when montmorillonite is added.

This paper is focuses on the study of the thermal and dynamic mechanical properties of polyethylene (PE) modified with crude palm oil (CPO). PE of grades LLDPE and HDPE were used in this study. Various compositions of CPO and PE compounds were prepared in a twin-screw extruder. Films of 0.2 mm thickness were produced by using blown film technique. LLDPE and HDPE with CPO samples show only one melting temperature peak in DSC results, indicating the existence of one type of crystal species on all PE matrices. Dynamic mechanical analysis (DMA) shows the decrease of storage modulus was effect of plasticing of CPO. The shifting of b transition peak was observed on both polymers with the addition of CPO indicating the CPO has a lubricating effect on both polymers.

Degenerative disc disease is one of the most frequently encountered spinal disorders. The intervertebral disc is a complex anatomic and functional structure, which makes the development of an efficient and reliable artificial disc a complex challenge. Not only is the disc function arduous to reproduce, but there are important consequences associated with the conception and the choice of materials that will have to bear the loads. Biochemical problems have complicated things even more. Two different principles have been applied in the realisation of a discal replacement: a metallic and/or polyethylene prosthesis allowing mainly mobility or a prosthesis enabling the reproduction of viscoelastic properties. Of course some devices attempt to combine both principles. In this paper we will try to present, in chronological order, an overview of the designs published in the literature as well as in the patents granted in this field. The very fact that such a long list of implants, based on ...

The impact of water stress was analysed in the xero-halophyte Mediterranean shrub Atriplex halimus using two Tunisian populations originating from a subhumid coastal site (Monastir) or from a semi-arid area (Kairouan). Seedlings were exposed for 10 days to nutrient solution containing either 0 or 15% polyethylene glycol. Water potential (W w), osmotic potential (W s), osmotic potential at full turgor [W s (100)], relative water content (RWC), shoot dry weight (DW) and changes in solute concentrations were quantified every 2 days throughout the stress period and inorganic solutes contents were determined at the end of the treatment. The water deficit induced a decrease in W w , W s and RWC in both populations, recorded changes being higher in plants of Monastir than those of Kairouan while the shoot dry weight was reduced in a similar extent in stressed plants from both populations. Water deficit induced an increase in proline, glycinebetaine and sugar concentrations. Proline accumulated as early as after the 24-h stress treatment while, glycinebetaine required more than 6 days of stress to accumulate. At the end of the stress period, the plants of Kairouan population accumulated higher amounts of proline than those of Monastir, while an opposite trend was reported for glycinebetaine. Both populations specifically accumulated Na ? in response to drought stress, suggesting that this element could play a physiological role in the stress response of this xero-halophyte species. Presented results suggest that the non-recyclable osmotic solute glycinebetaine does not necessarily preferentially accumulates in population facing permanent water stress and that other strategy than osmotic adjustment might be involved in drought tolerance of A. halimus.

Reverse total shoulder arthroplasty (RTSA) is widely used; however, the effects of RTSA geometric parameters on joint and muscle loading, which strongly influence implant survivorship and long-term function, are not well understood. By investigating these parameters, it should be possible to objectively optimize RTSA design and implantation technique. The purposes of this study were to evaluate the effect of RTSA implant design parameters on (1) the deltoid muscle forces required to produce abduction, and (2) the magnitude of joint load and (3) the loading angle throughout this motion. We also sought to determine how these parameters interacted. Seven cadaveric shoulders were tested using a muscle load-driven in vitro simulator to achieve repeatable motions. The effects of three implant parameters-humeral lateralization (0, 5, 10 mm), polyethylene thickness (3, 6, 9 mm), and glenosphere lateralization (0, 5, 10 mm)-were assessed for the three outcomes: deltoid muscle force required ...

In the present study the effect that the ethylene-acrylic acid copolymer (EAA) and plasticized starch (PLST) have upon the thermooxidative degradation of low density polyethylene (LDPE) was examined. The course of oxidation was followed using a carbonyl index derived from FTIR measurements and thermogravimetric measurements of weight changes observed in incubated samples. Three types of blends were examined: LDPE/starch, LDPE/EAA, and LDPE/starch/EAA.

Samples of polyethylene pellets were collected at 30 beaches from 17 countries and analyzed for organochlorine compounds. PCB concentrations in the pellets were highest on US coasts, followed by western Europe and Japan, and were lower in tropical Asia, southern Africa and Australia. This spatial pattern reflected regional differences in the usage of PCBs and was positively correlated with data from Mussel Watch, another monitoring approach. DDTs showed high concentrations on the US west coast and in Vietnam. In Vietnam, DDT was predominant over its metabolites (DDE and DDD), suggesting the principal source may be current usage of the pesticide for malaria control. High concentrations of pesticide HCHs were detected in the pellets from southern Africa, suggesting current usage of the pesticides in southern Africa. This study demonstrates the utility and feasibility of the International Pellet Watch approach to monitor POPs at a global scale.

The main objective of this study was to explore nonacidic catalysts for recycling of low-density polyethylene (LDPE) by coprocessing with vacuum gas oil (VGO). The focus of this study is to investigate processability of coprocessing LDPE with VGO, and to obtain environmentally friendly liquid fuels from such coprocessing. LDPE and VGO were cracked over activated carbon-supported metal catalysts (M-Ac) and acidic catalysts (HZSM-5, DHC-8) using a batch autoclave at 425, 435, and 450°C under hydrogen atmosphere. In hydrocracking of LDPE in VGO, the most suitable temperature was found to be 435°C. The amount of sulfur in liquid products obtained from hydrocracking over activated carbon-supported metal catalysts was lower than that over HZSM-5. Activated carbon-supported metal catalysts acted as an absorbent for sulfur compounds and H 2 S and also facilitated hydrodesulfurization (HDS). The hydrocarbon types in liquids were determined by nuclear magnetic resonance (NMR) analysis. In the cases of activated carbonsupported metal catalysts, aromatic species were found between 4% and 8.9%, whereas the liquid product obtained over HZSM-5 has 28% aromatic species. In the presence of activated carbonsupported metal catalysts, the isoparaffin index was found to be between 0.32 and 0.66. However, the isoparaffin index was 0.01 in the liquid obtained over HZSM-5. The presence of lower aromatics and higher isoparaffin index in liquid products obtained over the activated carbon-supported metal catalysts suggest an improved hydrocarbon fuel from an environmental viewpoint.

The separation properties of Nafion ® and sulfonated polyimide (SP) membranes have been compared for the recovery of acids from effluents containing metallic salts. To improve the selectivity, we have deposited a polyethylene imine (PEI) anion-exchange layer on the membrane surface by using two different techniques, a conventional electrodeposition and the plasma polymerization technique involving an ethylene/ammonia monomers mixture. We have pointed out the efficiency of the latter technique since the transport number of multivalent cations has been decreased by 74 and 54% for the Nafion ® and the SP membranes, respectively. Plasma modified sulfonated polyimides are therefore good candidates for electrodialysis processes and constitute an alternative to the Nafion ® membrane.

The Pom-Pom model, recently introduced by McLeish and Larson ͓J. Rheol. 42, 81-110 ͑1998͔͒, is a breakthrough in the field of viscoelastic constitutive equations. With this model, a correct nonlinear behavior in both elongation and shear is accomplished. The original differential equations, improved with local branch-point displacement, are modified to overcome three drawbacks: solutions in steady state elongation show discontinuities, the equation for orientation is unbounded for high strain rates, the model does not have a second normal stress difference in shear. The modified extended Pom-Pom model does not show the three problems and is easy for implementation in finite element packages, because it is written as a single equation. Quantitative agreement is shown with experimental data in uniaxial, planar, equibiaxial elongation as well as shear, reversed flow and step-strain for two commercial low density polyethylene ͑LDPE͒ melts and one high density polyethylene ͑HDPE͒ melt. Such a good agreement over a full range of well defined rheometric experiments, i.e., shear, including reversed flow for one LDPE melt, and different elongational flows, is exceptional.

Electro-Fusion (EF) joint is a technique to join Polyethylene pipes (PE) pipes which carry gas or water medium. Generally it is assumed that the PE pipe has a 50 year life. But PE pipes get failed before its natural lifetime due to environmental load and conditions. PE joining is unavoidable in PE gas distribution pipe network. Failure of EF joint is a fundamental reason for the decrease in service life. This paper includes principles of Electro-fusion joint, temperature distribution, stress distribution due to thermal and structural loading. Due to this loading condition, inner cold region of EF joint has highly stress concentrated area. This paper analyzed using finite element analysis and found that the inner pressure causes to increase the gap between pipe and fitting while thermal load and external pressure tries to counteract the peeling effect. Due to this peeling effect, inner cold region acts as a crack initiation region. Weld joint strength depends upon the procedure adopted during EF joint which includes heating-cooling cycle, scrapping and contamination on joining surface are significant for the strength and life of the joint.

Diallyldimethylammonium chloride (DADMAC) was grafted onto polyethylene (PE) films by a double grafting procedure. The PE film was initially modified by grafting acrylic acid (AA), through a mutual irradiation method. AA-g-PE film, thus obtained was subjected to subsequent radiation grafting reaction of DADMAC, to give a DADMAC-g-AA-g-PE film having a comb-type structure. The influence of different conditions, such as the extent of AA grafting, DADMAC concentration, absorbed dose and dose rate, on the grafting yield of DADMAC was investigated. A maximum DADMAC grafting of 30% was achieved. The equilibrium degree of swelling (EDS) of the grafted films were gravimetrically determined. TGA and FT-IR techniques were employed to characterize the grafted PE films. Scheme 1. Grafting of DADMAC onto PE employing a two-stage procedure.

A simple, economic diode laser based cavity ringdown system for trace-gas applications in the petrochemical industry is presented. As acetylene (C 2 H 2 ) is sometimes present as an interfering contaminant in the gas flow of ethylene (ethene, C 2 H 4 ) in a polyethylene production process, an on-line monitoring of such traces is essential. We investigated C 2 H 2 -C 2 H 4 mixtures in a gas-flow configuration in real time. The experimental setup consists of a near-infrared external cavity diode laser with an output power of a few mW, standard telecommunication fibers and a home-made gas cell providing a user-friendly cavity alignment. A noise-equivalent detection sensitivity of 4.5 × 10 −8 cm −1 Hz −1/2 was achieved, corresponding to a detection limit of 20 ppbV C 2 H 2 in synthetic air at 100 mbar. In an actual C 2 H 2 -C 2 H 4 gas-flow measurement the minimum detectable concentration of C 2 H 2 added to the C 2 H 4 gas stream (which may already contain an unknown C 2 H 2 contamination) increased to 160 ppbV. Moreover, stepwise C 2 H 2 concentration increments of 500 ppbV were resolved with a 1-min time resolution and an excellent linear relationship between the absorption coefficient and the concentration was found.