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Polyvinyl Chloride (polyvinyl + chloride)
Selected AbstractsAnalyzing Polyvinyl Chloride in Japan With the Waste Input,Output Material Flow Analysis ModelJOURNAL OF INDUSTRIAL ECOLOGY, Issue 5 2009Shinichiro Nakamura Summary Effective life cycle management of polyvinyl chloride (PVC) calls for the separation of end-of-life PVC products at the time of collection not only from other wastes but among different PVC types as well. Information about the flow of PVC products in the economy is important for this purpose. Within the framework of the Japanese input,output (IO) table for the year 2000, with around 400 industry sectors, the flow of PVC is captured in terms of six PVC-embodying products and in terms of three PVC types, (1) flexible PVC (soft PVC), (2) rigid PVC (hard PVC), and (3) others. The degree of resolution; the consideration of different PVC types, which are seldom performed in the material flow analysis (MFA) literature; and the use of waste input,output material flow analysis (WIO-MFA) represent distinguishing features of our study. The use of WIO-MFA methodology enables one to convert a monetary input,output table into a physical interindustry flow table involving an arbitrary number of materials under full consideration of the mass balance. The results indicate that 40% of the PVC produced in Japan is exported (as resins and as products such as passenger motor cars), and the rest is accumulated mostly as capital stock. The largest share of accumulation goes to public construction in the form of plates, pipes, and bars, which are mostly hard-PVC products. [source] A Bis-Oxime Derivative of Diaza-18-Crown-6 as an Ionophore for Silver IonELECTROANALYSIS, Issue 11 2005Michael Abstract A new pendant-arm derivative of diaza-18-crown-6, containing two oxime donor groups, has been synthesized and incorporated into a polyvinyl chloride (PVC) membrane ion-selective electrode. The electrode shows selectivity for Ag+ ion, with a near Nernstian response. Pb2+, Cu2+, Hg2+, and Tl+ are major interfering ions, with Cd2+ having minor interference. The electrode shows no potentiometric response for the ions Mg2+, Al3+, K+, Ca2+, Ni2+, Fe3+, and La3+, and is responsive to H+ at pH<6. [source] Stability Enhancement of All-Solid-State H+ ISEs with Cross-Linked Silicon-Urethane MatricesELECTROANALYSIS, Issue 8 2005Nak-Hyun Kwon Abstract An all-solid-state hydrogen-ion-selective electrode (ASHISE) was fabricated using the polymer hybrid membrane. Polymer membranes composed of Tecoflex polyurethane (TPU), polyvinyl chloride (PVC), silicon rubber (SR), and additives (KTpClPB, DOA, and TDDA) were cast on a carbon rod. The TPU/SR hybrid membrane exhibited a longer lifetime and a higher sensitivity in the sensing of the H+ ion compared to conventional TPU/PVC and PVC/SR hybrid membranes. Moreover, the addition of SiCl4 to TPU-based matrices enhanced the potentiometric response and ISE stability, due to the chemical bonding between Si and CO in urethane, in which the cross-linking configuration was confirmed by DSC, FT-IR, and XPS experiments. TPU/SR membranes containing SiCl4 were rendered more stable and showed a pH response over a wide range (i.e., pH,2,11.5) with the slope of 60±2,mV/pH for more than four months. The ASHISE exhibited a small interfering potential variation in the wide range of the salt concentration (from 1.0×10,6,M up to 0.1,M). The ASHISE showed a result comparable to a commercial clinical blood analyzer. [source] Cot mattresses as reservoirs of potentially harmful bacteria and the sudden infant death syndromeFEMS IMMUNOLOGY & MEDICAL MICROBIOLOGY, Issue 1 2004Richard E. Sherburn Abstract Cot mattress materials were investigated as potential reservoirs of bacteria in relation to the sudden infant death syndrome (SIDS). The sleeping position of the infant significantly influenced bacterial population density of cot mattress polyurethane foams (p<0.0000001) and their covers (p<0.004). Staphylococcus aureus was isolated at significantly higher frequency (p<0.03) from the infant's head region of cot mattress materials. Significantly higher bacterial population densities (p<0.001) were associated with polyurethane foams from non-integral mattresses (exposed polyurethane foam), when compared to those from mattresses completely covered by polyvinyl chloride (integral type mattress). The frequency of isolation of S. aureus from polyurethane foams from non-integral mattresses was also significantly higher (p=0.03) than from foams from the integral type. The following factors were significantly associated with increased frequency of isolation of S. aureus: from the polyurethane foam, previous use of non-integral mattresses by another child (p=0.03 for all sample sites, p=0.01 for torso region); from the covers, sleeping in the prone position (p=0.003 head region, p=0.001 torso region). Prone sleeping was also significantly associated with increased bacterial population levels (p=0.01) and increased frequency of isolation of Escherichia coli (p=0.02) from the torso region of cot mattress covers. These findings could explain some recently identified risk factors for SIDS associated with type and previous use of cot mattresses. Clostridium perfringens was isolated at very low frequency and Streptococcus pyogenes was not isolated from any cot mattress materials tested. [source] The effect of temperature and ventilation condition on the toxic product yields from burning polymersFIRE AND MATERIALS, Issue 1 2008A. A. Stec Abstract A major cause of death or permanent injury in fires is inhalation of toxic gases. Moreover, every fire is unique, and the range of products, highly dependant on fire conditions, produces a wide variety of toxic and irritant species responsible for the most fire fatalities. Therefore, to fully understand each contribution to the toxicity it is necessary to quantify the decomposition products of the material under the test. Fires can be divided into a number of stages from smouldering combustion to early well-ventilated flaming through to fully developed under-ventilated flaming. These stages can be replicated by certain bench-scale physical fire models using different fuel-to-oxygen ratios, controlled by the primary air flow, and expressed in terms of the equivalence ratio (the actual fuel/air ratio divided by the stoichiometric fuel/air ratio). This work presents combustion product yields generated using a small-scale fire model. The Purser Furnace apparatus (BS7990 and ISO TS 19700) enables different fire stages to be created. Identification and quantification of combustion gases and particularly their toxic components from different fire scenarios were undertaken by continuous Fourier transform infrared spectroscopy. The relationship between type of the fire particularly the temperature and ventilation conditions and the toxic product yields for four bulk polymers, low-density polyethylene, polystyrene (PS), Nylon 6.6 and polyvinyl chloride (PVC) is reported. For all the polymers tested, except PVC, there is a dramatic increase in the yield of products of incomplete combustion (CO and hydrocarbons) with increase in equivalence ratio, as might be expected. For PVC there is a consistently high level of products of incomplete combustion arising both from flame inhibition by HCl and oxygen depletion. There is a low sensitivity to furnace temperature over the range 650,850°C, except that at 650°C PS shows an unexpectedly high yield of CO under well-ventilated conditions and PVC shows a slightly higher hydrocarbon yield. This demonstrates the dependence of toxic product yields on the equivalence ratio, and the lack of dependence on furnace temperature, within this range. Copyright © 2007 John Wiley & Sons, Ltd. [source] Detailed determination of smoke gas contents using a small-scale controlled equivalence ratio tube furnace methodFIRE AND MATERIALS, Issue 8 2007Per Blomqvist Abstract A series of tests including seven different materials and products have been conducted using a controlled equivalence ratio tube furnace test method. The main objective of the tests was to determine yields of fire-generated products at defined combustion conditions. The tube furnace test method was set up and run in close agreement with that described in BS 7990:2003. At the time of experimental work the new tube furnace method was in the process of becoming an international standard. It was thus of interest to make an assessment of the capability of the method for determining production yields of important toxic fire products from different types of materials and products. The test series included solid wood, flexible polyurethane (PUR), fire-retarded rigid PUR, a polyvinyl chloride (PVC) carpet, a high-performance data cable with fluorine-containing polymer matrix, a PVC-based cable sheathing material and fire-retarded polyethylene cable insulation material. Duplicate tests were generally conducted at both well-ventilated and vitiated combustion conditions with these materials. The smoke gases produced from the combustion were quantified for inorganic gases by FTIR technique in all tests. A more detailed analysis of the smoke gases was conducted for some of the materials. This extended analysis contained a detailed assessment of organic compounds including, e.g. volatile organic compounds, isocyanates, aldehydes and polycyclic aromatic hydrocarbons. The analysis further included measurement of the size distribution of fire-generated particles for some of the materials. The quantification of toxic inorganic gases produced by combustion at both well-ventilated and vitiated conditions was successful regarding repeatability and stability. Typical yields for the two fire stages investigated were determined for a wide range of materials and products. The detailed analysis of organic compounds further corroborated that the new tube furnace method can replicate defined combustion conditions. Copyright © 2007 John Wiley & Sons, Ltd. [source] Viable ultramicrocells in drinking waterJOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2009F.S. Silbaq Abstract Aims:, To examine the diversity of cultivable 0·2 micron filtrate biofilm forming bacteria from drinking water systems. Methods and Results:, Potable chlorinated drinking water hosts phylogenetically diverse ultramicrocells (UMC) (0·2 and 0·1 ,m filterable). UMC (starved or dwarf bacteria) were isolated by cultivation on minimal medium from a flow system wall model with polyvinyl chloride (PVC) pipes. All cultivated cells (25 different isolates) did not maintain their ultra-size after passages on rich media. Cultured UMC were identified by their 16S ribosomal DNA sequences. The results showed that they were closely related to uncultured and cultured members of the Proteobacteria, Actinobacteria and Firmicutes. The isolates of phylum Actinobacteria included representatives of a diverse set of Actinobacterial families: Micrococcaceae, Microbacteriaceae, Dermabacteraceae, Nocardiaceae and Nocardioidaceae. Conclusions:, This study is the first to show an abundance of cultivable UMC of various phyla in drinking water system, including a high frequency of bacteria known to be involved in opportunistic infections, such as Stenotrophomonas maltophilia, Microbacterium sp., Pandoraea sp. and Afipia strains. Significance and Impact of the Study:, Chlorinated tap water filtrate (0·2 and 0·1 ,m) still harbours opportunistic micro-organisms that can pose some health threat. [source] Antibacterial polyvinyl chloride/antibiotic films: The effect of solvent on morphology, antibacterial activity, and release kineticsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2010Martha Merchan Abstract Medical-grade polyvinyl chloride was modified with sodium ampicillin in a concentration range from 0 to 5 wt % by solvent casting technique using cyclohexanone and N,N -dimethylformamide. The obtained polymeric systems were characterized by optical microscopy, tensile test, and scanning electron microscopy. In addition, in vitro antibacterial activity against Gram-negative and Gram-positive bacteria was determined by an agar diffusion test. Antibiotic release experiments were performed in distilled water and physiological saline solution, which were monitored by UV-vis spectroscopy. The results showed a crucial role of the solvent on the morphology, antibacterial activity, and releasing characteristic of the ampicillin. Furthermore, a mathematical model was applied to data obtained from release study, to characterize the release kinetics of the ampicillin from the polyvinyl chloride-antibiotic systems. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Investigation of the effect of delayed reflux on PVC grain properties produced by suspension polymerizationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010N. Etesami Abstract The effects of the condenser operation on properties of polyvinyl chloride (PVC) particles produced by suspension polymerization process were investigated in a pilot scale reactor. It was observed that delaying reflux operation increased the cold plasticizer absorption of the final resin. Both bulk density and K-value of the PVC powder decreased by increasing time delay in the reflux operation. It was also found that commencement of refluxing before 20% conversion resulted in bimodal particle size distribution (PSD), while monomodal PSD was obtained for longer delays in refluxing. SEM micrographs showed that surface of produced particles were rough and smooth when reflux started before and after 20% conversion, respectively. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Absorption, disposition and metabolism of di-isononyl phthalate (DINP) in F-344 ratsJOURNAL OF APPLIED TOXICOLOGY, Issue 5 2002R. H. McKee Abstract Di-isononyl phthalate (DINP; CAS no. 68515-48-0) is a general-purpose plasticizer for polyvinyl chloride. It produced liver and kidney effects when given to rodents at high oral doses, but there were no target organ effects in primates treated under similar conditions. To assist in understanding the basis for these species differences, the pharmacokinetic properties of DINP were evaluated in rodents following both oral and dermal administration. These studies demonstrated that the pharmacokinetic properties of DINP are similar to those of other high-molecular-weight phthalates. When orally administered to rodents, DINP is rapidly metabolized in the gastrointestinal tract to the corresponding monoester, absorbed and excreted, primarily in the urine. Shortly after administration, DINP is found primarily in liver and kidneys, but it does not persist or accumulate in any organ or tissue. It is very poorly absorbed from the skin, but once absorbed it behaves in the same way as the orally administered material. The results of these rodent studies contrast with data from studies involving humans or other primates, which indicate low absorption at low oral doses and much more limited total absorption at high doses. It appears that many, if not all, of the effects of DINP in rodent studies are associated with internal doses that would be difficult, if not impossible, to achieve in humans under any circumstances. Thus, the results of rodent studies may not be very useful in assessing the potential risks to humans from high-molecular-weight phthalates. Copyright © 2002 John Wiley & Sons, Ltd. [source] A kinetic evaluation of the anaerobic digestion of two-phase olive mill effluent in batch reactorsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 3 2005Francisco Raposo Abstract A comparative kinetic study was carried out on the anaerobic digestion of two-phase olive mill effluent (TPOME) using three 1-dm3 volume stirred tank reactors, one with freely suspended biomass (control), and the other two with biomass supported on polyvinyl chloride (PVC) and bentonite (aluminium silicate), respectively. The reactors were batch fed at mesophilic temperature (35 °C) using volumes of TPOME of between 50 and 600 cm3, corresponding to chemical oxygen demand (COD) loadings in the range of 1.02,14.22 g, respectively. The process followed first-order kinetics and the specific rate constants, K0, were calculated. The K0 values decreased considerably from 2.59 to 0.14 d,1, from 1.93 to 0.23 d,1 and from 1.52 to 0.17 d,1 for the reactors with suspended biomass (control) and biomass immobilized on PVC and bentonite, respectively, when the COD loadings increased from 1.02 to 14.22 g; this showed an inhibition phenomenon in the three reactors studied. The values of the critical inhibitory substrate concentration (S*), theoretical kinetic constant without inhibition (KA) and the inhibition coefficient or inhibitory parameter for each reactor (n) were determined using the Levenspiel model. Copyright © 2004 Society of Chemical Industry [source] Analyzing Polyvinyl Chloride in Japan With the Waste Input,Output Material Flow Analysis ModelJOURNAL OF INDUSTRIAL ECOLOGY, Issue 5 2009Shinichiro Nakamura Summary Effective life cycle management of polyvinyl chloride (PVC) calls for the separation of end-of-life PVC products at the time of collection not only from other wastes but among different PVC types as well. Information about the flow of PVC products in the economy is important for this purpose. Within the framework of the Japanese input,output (IO) table for the year 2000, with around 400 industry sectors, the flow of PVC is captured in terms of six PVC-embodying products and in terms of three PVC types, (1) flexible PVC (soft PVC), (2) rigid PVC (hard PVC), and (3) others. The degree of resolution; the consideration of different PVC types, which are seldom performed in the material flow analysis (MFA) literature; and the use of waste input,output material flow analysis (WIO-MFA) represent distinguishing features of our study. The use of WIO-MFA methodology enables one to convert a monetary input,output table into a physical interindustry flow table involving an arbitrary number of materials under full consideration of the mass balance. The results indicate that 40% of the PVC produced in Japan is exported (as resins and as products such as passenger motor cars), and the rest is accumulated mostly as capital stock. The largest share of accumulation goes to public construction in the form of plates, pipes, and bars, which are mostly hard-PVC products. [source] Modeling for simulation of fluidized-bed incineration processAICHE JOURNAL, Issue 6 2001F. Marias A mathematical model for the fluidized-bed incineration process was developed using the waste composed of wood, cardboard and polyvinyl chloride. It is based on heat and mass balances of the gas held within the five zones representing both the bubbling bed and freeboard and including heat transfer with sand and reacting particles of char (pyrolysis residue). The mixture fraction concept and assumption of chemical equilibrium are used to compute temperature and species concentration fields resulting from volatile combustion. These fields are affected by char combustion, which relies, in turn, on a model based on surface reaction and a full population balance. The formation of pollutants (NOx, SOx ) was also taken into account. The main steps involved by the numerical resolution of the model are discussed, and some results are shown for a 1 MW unit. [source] Lack of O -polysaccharide enhances biofilm formation by Bradyrhizobium japonicumLETTERS IN APPLIED MICROBIOLOGY, Issue 5 2010Y.-W. Lee Abstract Aims:, To reveal the effects of the O -polysaccharide antigen of Bradyrhizobium japonicum LPS on biofilm formation and motility. Methods and Results:, Wild type and O-antigen-deficient mutant strains of B. japonicum were tested for biofilm formation on polyvinyl chloride (PVC) surfaces and motility on semi-solid (0·3%) agar media. After 7 days of incubation, the amount of biofilms formed by the mutant was c. 3·5-fold greater than that of the wild type. Unlike biofilm formation, the motility assay revealed that the mutant strain was less motile than the wild type. Conclusions:, This study shows enhanced biofilm formation and decreased motility by the O-antigen-deficient mutant, suggesting that the lack of the O -polysaccharide of the rhizobial LPS is associated with biofilm-forming ability and movement. Significance and Impact of the Study:, LPS plays an important role in both pathogenic and beneficial bacteria. It has also been reported that LPS deficiency negatively affects biofilm formation. However, our results demonstrate that the O-antigen-deficient mutant enhances biofilm formation, presumably through a significant increase in hydrophobicity. It is notable that the hydrophobicity of cell walls might be a key regulator in controlling biofilm development in B. japonicum. [source] Characterization of two Pseudomonas putida lipopeptide biosurfactants, putisolvin I and II, which inhibit biofilm formation and break down existing biofilmsMOLECULAR MICROBIOLOGY, Issue 1 2004Irene Kuiper Summary Pseudomonas putida strain PCL1445 was isolated from roots of plants, grown on a site polluted with polycyclic aromatic hydrocarbons. PCL1445 produces biosurfactant activity at the end of the exponential growth phase. High-performance liquid chromatography (HPLC) analysis of supernatant extracts of PCL1445 showed two peaks with surface-tension reducing activity, tentatively assigned as biosurfactants putisolvin I and putisolvin II and was followed by structural analyses. A transposon mutant of PCL1445, strain PCL1436, which lacks the two surface-active peaks appeared to be mutated in an open reading frame (ORF) with amino acid homology to various lipopeptide synthetases. Structural analyses of the two biosurfactants of PCL1445 revealed that both are novel cyclic lipodepsipeptides with a hexanoic lipid chain connected to the N-terminus of a 12-amino-acid peptide moiety, in which the C-terminal carboxylic acid group forms an ester with the hydroxyl side-chain of Ser9. The difference between the two structures is located in the second amino acid from the C-terminus, being valine for putisolvin I, and leucine/isoleucine for putisolvin II. We show that these novel compounds lower the surface tension and influence the biofilm development on polyvinyl chloride (PVC). Biofilm formation of the bio-synthetic mutant PCL1436 was strongly increased containing more cells, which formed aggregates earlier as compared with wild-type PCL1445 biofilms. Using purified putisolvin I and II it was shown that biofilm formation of different Pseudomonas strains was inhibited and most interestingly, that both putisolvins are also able to break down existing Pseudomonas biofilms. [source] PVC and LDPE for packing minimally processed garlicPACKAGING TECHNOLOGY AND SCIENCE, Issue 3 2002Nilda de Fátima Ferreira Soares Abstract Minimum processing associated with an adequate packing system has shown good results in preserving a large group of perishable horticultural produce. The present work was done to determine the effect of the number of layered of low-density polyethylene (LDPE) or polyvinyl chloride (PVC) film on the quality of minimally processed packed garlic (Allium sativum), known for its short shelf-life. Polystyrene trays containing 200,g garlic bulbils were wrapped in one to four layers of PVC or one or two layers of LDPE and stored at room temperature. Changes in weight, bulbil colouration, in-package gas composition and apparent quality were monitored for 14 days. Best results were obtained by wrapping the packages in four layers of PVC film, with insignificant weight loss (5%), changes in colour tone and saturation, and the in-pack atmosphere (O2,=,0.01% and CO2,=,13.5%) inhibited fungal growth, extending shelf-life to 13 days at 25,±,2°C. On the other hand, the high in-package moisture in LDPE wrapping favoured fungal growth, rapidly depreciating bulbil quality. The shelf-life of minimally processed garlic can be increased by maintaining an adequate in-pack atmosphere, which can be achieved by using four layers of PVC or a another film of similar permeability. Copyright © 2002 John Wiley & Sons, Ltd. [source] Production of leather-like composites using short leather fibers.POLYMER COMPOSITES, Issue 6 2002Leather-like composites were prepared by addition of chemically modified short leather fibers (SLF) into a plasticized polyvinyl chloride (pPVC) matrix. The fibers were subjected to chemical modification by emulsion polymerization to achieve good interfacial adhesion between SLF and the pPVC matrix. The SLF with chemical modification were obtained from three different reaction conditions where these SLF have different percentages of grafted and deposited PMMA polymer onto the fiber surface. The incorporation of the SLF into the thermoplastic matrix was carried out using a torque-rheometer and the composites obtained were molded by compression. Tensile and tear mechanical tests were performed on composite samples, and the morphology of the fractured surfaces was analyzed using scanning electron microscopy (SEM). The results show that the incorporation by grafting of polymethyl metacrylate (PMMA) onto the fibers produced a significant improvement of their interfacial adhesion to pPVC, promoting the compatibilization between the fiber surface and matrix. The findings are discussed and interpreted in terms of enhanced adhesion at phase boundaries. Overall, the results confirm that it is possible to produce modified leather composites based on a pPVC matrix, which exhibit relatively high tensile strength, tear resistance and flexibility. These composites are very suitable candidate materials for applications in the footwear industry. [source] The effects of water and frequency on fatigue crack growth rate in modified and unmodified polyvinyl chloridePOLYMER ENGINEERING & SCIENCE, Issue 2 2010Noorasikin Samat A study of the influence of water environments on the cyclic fatigue crack behavior of polyvinyl chloride (PVC), with (PVC-M) and without (PVC-U) chlorinated polyethylene (CPE) impact modifier was undertaken and compared with corresponding results in air. Two frequencies of 1 and 7 Hz were applied to assess the influence of frequency on the fatigue behavior; a higher fatigue resistance and threshold were obtained with increasing frequency. This trend is more significant in water. However, in this environment, the fatigue resistance deteriorated under conditions of higher stress intensity factor amplitude (,K) and frequency. The fatigue properties of PVC-U are the most affected by the presence of water, particularly at low frequency and higher ,K. Examination of the fracture surface showed the interaction of water molecules and the PVC matrix with the formation of (1) a nodular structure, close to the fatigue threshold and (2) plasticized structures at high ,K, which are associated with a greater threshold value and fatigue resistance. The absorption of the water retarded the fibrillation of craze and caused crack blunting effects. Water functions as a plasticizer, particularly at high ,K, through the formation of the plasticized structures. Results are compared with those observed from an in-service failure. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers [source] Effects of welding procedures on mechanical and morphological properties of hot gas butt welded PE, PP, and PVC sheetsPOLYMER ENGINEERING & SCIENCE, Issue 4 2008Onur Balkan Mechanical and morphological properties of hot gas butt welds on polyethylene (PE), polypropylene (PP), and polyvinyl chloride (PVC) sheets for four different procedures, which are single and double V-welds with and without a welding shoe, were investigated. Besides, weldabilities of base materials were evaluated by rheological measurements. These revealed that weldabilities of PE and PP sheets were better than that of PVC. Welding energy (Ew), which is transferred onto weld surfaces, was calculated to evaluate weld quality. The results of tensile, impact, and bending tests indicated that the weld strengths of PVC sheets were lower than those of PE and PP sheets. When the welding shoe was used, weld strength increased significantly for each material because of the presence of sufficient welding pressure and the effective heating on surfaces. The best results were attained for the double V-welds with the welding shoe. Morphology of welded regions was evaluated by polarized light, stereo, and scanning electron microscopy. Polarized light microscopy studies indicated that the heat-affected zone (HAZ) consisted of welding rod core, molten zone, and deformed spherulitic zone, and the welding interface was indistinguishable from the base material when the welding pressure was enough. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers [source] Establishing ignition conditions for the tank manifold fire at the Powell Duffryn tank terminalPROCESS SAFETY PROGRESS, Issue 3 2002John L. Woodward A fire destroyed three tanks containing crude sulfate turpentine (CST) at a storage facility in Savannah, Georgia, on April 10, 1995, prompting an evacuation, and resulting in some environmental damage. The events of this fire have been documented an a U.S. EPA report [1]. The investigators determined the most likely cause of ignition was overheating in a newly-installed activated-carbon drum as air was drawn in during evening cooling. One aspect not entirely explained in the EPA report is that the tanks were connected by a vapor manifold and were not protected by detonation arresters, yet the flames initially propagated to only one tank. This paper discusses the development of a model to quantify the likely sequence of events that is consistent with observations. Tank inflows and outflows forced by the diurnal temperature cycle were modeled to calculate hydrocarbon concentrations in the vapor space. This establishes that the combination of vapor concentrations above the lower flammable limit, and oxygen concentrations above the lower limit to support combustion, occur for only a few hours during the day. Further estimates of the ignition, flame acceleration, and run-up distance indicate that an explosion probably occurred inside the polyvinyl chloride (PVC) pipe. The forces from such an explosion would be sufficient to open the PVC pipe, thereby slowing the flame front propagation and contributing to the failure to initially ignite more than one tank. This paper illustrates how modeling strengthens an accident investigation and helps distinguish between alternative postulated ignition sequences. [source] Material wear of polymeric tracheostomy tubes: A six-month study,THE LARYNGOSCOPE, Issue 4 2009Sara Backman MSc Abstract Objectives: The objectives were to study long-term material wear of tracheostomy tubes made of silicone (Si), polyvinyl chloride (PVC), and polyurethane (PU) after 3 and 6 months of clinical use. Study Design: The study has a prospective and comparative design. Methods: Nineteen patients with long-term tracheostomy, attending the National Respiratory Center in Sweden, were included, n = 6 with Si tubes, n = 8 with PVC tubes, and n = 5 with PU tubes. The tubes were exposed to the local environment in the trachea for 3 and 6 months and analyzed by scanning electron microscopy, attenuated total reflectance Fourier transform infrared spectroscopy, and differential scanning calorimetry. Results: All tubes revealed severe surface changes. No significant differences were established after 3 or 6 months of exposure between the various materials. The changes had progressed significantly after this period, compared to previously reported changes after 30 days of exposure. The results from all analyzing techniques correlated well. Conclusions: All tubes, exposed in the trachea for 3,6 months, revealed major degradation and changes in the surface of the material. Polymeric tracheostomy tubes should be changed before the end of 3 months of clinical use. Laryngoscope, 2009 [source] Life-cycle toxicity of dibutyltin to the sheepshead minnow (Cyprinodon variegatus) and implications of the ubiquitous tributyltin impurity in test materialAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 9 2003Thomas F. Lytle Abstract Dibutyltin (DBT) is used in the plastics polymerization process as a catalyst in polyvinyl chloride (PVC) products and is the primary degradation product of tributyltin (TBT), an antifoulant in marine paint. DBT and other organotin compounds make their way into the environment through antifoulants, PVC processing plants, and PVC products maintained in water and water-handling systems. A flow-through saltwater life-cycle toxicity test was conducted to determine the chronic effect of DBT to the sheepshead minnow (Cyprinodon variegatus Lacepede), an estuarine species. Embryos were monitored through hatch, maturation, growth, and reproduction in DBT concentrations of 158, 286, 453, 887, and 1510 µg l,1. Progeny were monitored for survival as embryos and fry/juveniles, and growth for 30 days post-isolation. Mean length of parental generation fish was significantly reduced on day 30 at DBT concentrations ,887 µg l,1, setting the lowest observable effect concentration (LOEC) at 887 µg l,1 and the no observable effect concentration (NOEC) at 453 µg l,1. Fecundity, as egg viability, was significantly reduced at the LOEC. Survival of parental and progeny generation embryos and mean length, wet weight and dry weight of progeny generation juveniles were not significantly affected at concentrations ,LOEC. TBT, a toxic impurity in DBT reversibly produced in DBT by the process of comproportionation, was also monitored throughout this study. Comparing measured levels of TBT in this study with levels exerting toxic effects in an earlier TBT life-cycle study with C. variegatus suggests biological responses in this study were likely due to the TBT impurity and not to DBT alone. Results indicate that TBT impurity as low as 0.1% may have a significant influence on the perceived toxicity of DBT and that spontaneous production of TBT in DBT may be the major source of biological toxicity of DBT. Copyright © 2003 John Wiley & Sons, Ltd. [source] Pulsatile Ventricular Assist Device with Pericardial Inner LiningARTIFICIAL ORGANS, Issue 11 2001Adolfo A. Leirner Abstract: Preserved pericardium in contact with blood is not thrombogenic, therefore avoiding the use of anticoagulants, and has excellent mechanical properties. Our objective is to take advantage of these characteristics and build a pulsatile ventricular assist device (VAD) with pericardium used as the inner lining of the blood chamber. A mold is used for the tanning of the pericardium, rendering it with an exact shape. A flexible polymeric structure is designed to serve as a base for the pericardium, guiding it and limiting its rate of strain. It consists of two halves, which when outfitted with the interior pericardium lining and connected to each other, form the blood chamber. This assembly is housed in rigid polyvinyl chloride (PVC) shells making up the air chamber for the pneumatic activation. Valves are likewise made of pericardium. Sealing of the chambers was tested statically up to 300 mm Hg with no air or fluid leakage. The device was tested for 60 continuous days in a mock loop, demonstrating hydrodynamic performance adequate for ventricular assist. Micrographs (confocal laser and scanning electron microscopy) were obtained of several pericardium areas, especially on the flexing regions that are a transition between the wet and dry regions. No sign of damage to the pericardium was observed either with the naked eye or at the microscopic level. From the hydraulic performance and materials viewpoints, a completely pericardium-lined pulsatile VAD displaying a polymeric structure that avoids unpredictable bending and limits strain is feasible. The results warrant further studies regarding biocompatibility and strength advantages. [source] Phthalate Esters in Foods: Sources, Occurrence, and Analytical MethodsCOMPREHENSIVE REVIEWS IN FOOD SCIENCE AND FOOD SAFETY, Issue 1 2010Xu-Liang Cao ABSTRACT:, Phthalates are a group of diesters of ortho-phthalic acid (dialkyl or alkyl aryl esters of 1,2-benzenedicarboxylic acid). Higher-molecular-weight phthalates, such as di-2-ethylhexyl phthalate (DEHP), are primarily used as plasticizers to soften polyvinyl chloride (PVC) products, while the lower-molecular-weight phthalates, such as diethyl phthalate (DEP), di-n-butyl phthalate (DBP), and butyl benzyl phthalate (BBzP), are widely used as solvents to hold color and scent in various consumer and personal care products. Phthalates have become ubiquitous environmental contaminants due to volatilization and leaching from their widespread applications, and thus contamination of the environment has become another important source for phthalates in foods in addition to migration from packaging materials. Human exposure to phthalates has been an increased concern due to the findings from toxicology studies in animals. DEHP, one of the important and widely used phthalates, is a rodent liver carcinogen. DEHP, DBP, BBzP, and several phthalate metabolites, such as monobutyl phthalate, monobenzyl phthalate, and mono-(2-ethylhexyl) phthalate, are teratogenic in animals. Since foods are the major source of exposure to phthalates, information on levels of phthalates in foods is important for human exposure assessment. The objective of this review is to identify the knowledge gaps for future investigations by reviewing levels of a wide range of phthalates in a variety of foods, such as bottled water, soft drinks, infant formula, human milk, total diet foods, and others, migration of phthalates from various food-packaging materials, and traditional and new methodologies for the determination of phthalates in foods. [source] | ||||||||||||||||||||||