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Polyurethane Foam (polyurethane + foam)
Kinds of Polyurethane Foam Selected AbstractsOxypropylation of Lignins and Preparation of Rigid Polyurethane Foams from the Ensuing PolyolsMACROMOLECULAR MATERIALS & ENGINEERING, Issue 10 2005Hamid Nadji Abstract Summary: Different lignins were converted into polyols by a chain extension reaction with propylene oxide (PO). Thus, soda lignin from Alfa (Stipa tenacissima) (SL), organosolv lignin from hardwoods (OL), kraft lignin (KL) from softwood and oxidized organosolv lignin (OOL) were oxypropylated in a batch reactor at 180,°C in the presence of KOH as catalyst. The ensuing polyols were characterized by FTIR and 1H NMR spectroscopy, which showed that they had incorporated poly(propylene oxide) grafts into their structure. Their viscosity varied from 5 mPa,·,s to infinity, depending on the Lignin/PO ratio and their hydroxy index was in the range of 100,200, which made them suitable for rigid polyurethane foam (RPU) formulations. The RPUs thus obtained had a Tg of ca. 60,°C and a thermal conductivity of ,20 mW/m,·,K before ageing and ,25 mW/m,·,K after accelerated ageing for 10 d at 70,°C. The analyses of the gases inside the cells showed that these were mostly closed, since the partial pressure did not decrease significantly with ageing. Photograph of polyurethane foam made from OLOP. [source] Novel TRIP-Steel/Mg-PSZ Composite,Open Cell Foam Structures for Energy AbsorptionADVANCED ENGINEERING MATERIALS, Issue 3 2010Christos G. Aneziris Porous materials have received extensive attention for energy absorption in the last years. In terms of this study austenitic TRIP-steel/Mg-PSZ composite,open cell foam structures are formed based on replicas using open-celled polyurethane foam as a skeleton with and without a supporting dense face (jacket) coating. Their compression strength as well as their specific energy absorption SEA has been registered as a function of the compressive strain. The zirconia addition has reinforced the composite material with the face coating up to a compressive strain of 50%. The stress-induced martensitic transformation of partially stabilized zirconia phases has been investigated as a function of the compressive strain by EBSD. The zirconia phase transformation is triggered already at low compressive strains below 2%. [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 piloted transition to flaming in smoldering fire retarded and non-fire retarded polyurethane foamFIRE AND MATERIALS, Issue 8 2008Olivier M. Putzeys Abstract The piloted transition from smoldering to flaming, though a significant fire safety concern, has not been previously extensively studied. Experimental results are presented on the piloted transition from smoldering to flaming in non-fire retarded (NFR) polyurethane foam and the fire retarded polyurethane foam Pyrell®. The samples are small blocks, vertically placed in the wall of an upward wind tunnel. The free surface is exposed to an oxidizer flow and a radiant heat flux. The smolder product gases pass upwards through a pilot. The experiments on NFR foam show that the smolder velocity and peak smolder temperature, which increase with the oxygen concentration and heat flux, are strongly correlated to the transition to flaming event, in that there are minimum values of these parameters for transition to occur. The existence of a minimum smolder velocity for ignition supports the concept of a gaseous mixture reaching a lean flammability limit as the criterion for the transition to flaming. To compensate for the solid- and gas-phase effects of the fire retardants on the piloted transition in Pyrell, it was necessary to increase the oxygen concentration and the power supplied to the smolder igniter and the pilot. The piloted transition is observed in oxygen concentrations above 17% in NFR foam and above 23% in Pyrell. The results show that although Pyrell is less flammable than NFR foam, it is still susceptible to smoldering and the piloted transition to flaming in oxygen-enriched environments, which is of interest for special applications such as future space missions. Copyright © 2008 John Wiley & Sons, Ltd. [source] A model to predict fire resistance of non-load bearing wood-stud wallsFIRE AND MATERIALS, Issue 1 2003H. Takeda Abstract The author has developed a series of computer models to predict the fire resistance of wood-framed walls and floors. The models utilize two-dimensional heat-conduction equations and thermo-physical property data to describe heat transfer through the assemblies. The model for wall assemblies WALL2D, the basic version of the wall model, has already been published in Fire and Materials. Recently, WALL2D has been extended to WALL2DN to analyse heat transfer through insulated walls and walls that experience openings at the joints between adjacent sheets of gypsum board. Since gypsum board shrinks at high temperatures, the joints between adjacent sheets of gypsum board open. Hot fire gases, thereby, enter the openings and heat the edge of the gypsum board and wood studs. The new model WALL2DN simulates the joint opening and describes the resultant effect of openings. The model also calculates heat transfer through insulation in the stud cavity and depicts the effect of insulation on the fire resistance of non-load bearing wall assemblies. Insulation selected in WALL2DN is glass-fibre insulation, rock-fibre insulation, polystyrene foam and polyurethane foam. When walls are exposed to fire, the insulation in the cavity shrinks (and/or melts) and an empty space appears at the interface between insulation and gypsum board. The model simulates this shrinking behaviour of insulation in the cavity. Finally, the model was validated by comparing the predicted results to those from full-scale standard fire-endurance tests. Copyright © 2003 John Wiley & Sons, Ltd. [source] Processing, mechanical properties, and interfacial bonding of a thermoplastic core-foam/composite-skin sandwich panel,ADVANCES IN POLYMER TECHNOLOGY, Issue 3 2010S. Pappadą Abstract In this work, a thermoplastic sandwich panel was designed, produced, and tested for use in insulating walls of containers for food transportation. A sandwich construction comprising a poly(ethylene terephthalate) core and polypropylene/glass fiber skins was evaluated as possible replacement of systems consisting of polyurethane foam in combination with unsaturated polyester glass-reinforced skins that are currently used for the manufacture of these structures. Factors were taken into account to satisfy the simultaneous need of thermal insulation and adequate mechanical properties that are required for the production of large flat panels 100-mm thick. The influences of different manufacturing processes and skin-core adhesion on the mechanical properties of this thermoplastic sandwich were investigated and are discussed in the text. © 2010 Wiley Periodicals, Inc. Adv Polym Techn 29:137,145, 2010; View this article online at wileyonlinelibrary. DOI 10.1002/adv.20186 [source] Composites of rigid polyurethane foam and cellulose fiber residueJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010M. C. Silva Abstract Rigid polyurethane composite foams were prepared with cellulose fibers as a filler. The cellulose fibers were an industrial residue of blanched cellulose pulp production. The influence of the cellulose fiber concentration on the structural, thermal, mechanical, and morphological properties of the foams was investigated. We also studied the influence of the cellulose fibers on the foam's resistance to fungal attack by placing a suspension of known fungus in contact with the surface of the foam and following the morphological evolution as a function of time (for 60 days). The increase in the cellulose filler concentration in the foams, up to 16% w/w with respect to the polyol, changed their properties as follows: (1) the cell size decreased, (2) the thermooxidative stability and mechanical properties remained approximately constant, (3) the thermal conductivity decreased slightly, and (4) fungal growth was observed. Therefore, a cellulosic fibrous industrial residue was rationally valorized as a filler in classical rigid polyurethane foams; this yielded materials with mechanical resistance and a susceptibility to fungi in a wet environment. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Enhancing the mechanical integrity of the implant,bone interface with BoneWelding® technology: Determination of quasi-static interfacial strength and fatigue resistanceJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2006Stephen J. Ferguson Abstract The BoneWelding® technology is an innovative bonding method, which offers new alternatives in the treatment of fractures and other degenerative disorders of the musculoskeletal system. The BoneWelding process employs ultrasonic energy to liquefy a polymeric interface between orthopaedic implants and the host bone. Polymer penetrates the pores of the surrounding bone and, following a rapid solidification, forms a strong and uniform bond between implant and bone. Biomechanical testing was performed to determine the quasi-static push-out strength and fatigue performance of 3.5-mm-diameter polymeric dowels bonded to a bone surrogate material (Sawbones solid and cellular polyurethane foam) using the BoneWelding process. Fatigue tests were conducted over 100,000 cycles of 20,100 N loading. Mechanical test results were compared with those obtained with a comparably-sized, commercial metallic fracture fixation screw. Tests in surrogate bone material of varying density demonstrated significantly superior mechanical performance of the bonded dowels in comparison to conventional bone screws (p < 0.01), with holding strengths approaching 700 N. Even in extremely porous host material, the performance of the bonded dowels was equivalent to that of the bone screws. For both cellular and solid bone analog materials, failure always occurred within the bone analog material surrounding and distant to the implant; the infiltrated interface was stronger than the surrounding bone analog material. No significant decrease in interfacial strength was observed following conditioning in a physiological saline solution for a period of 1 month prior to testing. Ultrasonically inserted implants migrated, on average, less than 20 ,m over, and interfacial stiffness remained constant the full duration of fatigue testing. With further refinement, the BoneWelding technology may offer a quicker, simpler, and more effective method for achieving strong fixation and primary stability for fracture fixation or other orthopaedic and dental implant applications. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2006 [source] Cell growth and Trametes versicolor laccase production in transformed Pichia pastoris cultured by solid-state or submerged fermentationsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 4 2010Marcos López Abstract BACKGROUND: Growth kinetics of Pichia pastoris and heterologous expression of Trametes versicolor laccase were compared. This is the first study of its kind between solid-state yeast cultures done on polyurethane foam (PUF) and submerged liquid fermentations (SmF). RESULTS: The maximum values of biomass were similar for SSF (solid-state fermentation) and SmF experiments when the BOD (biochemical oxygen demand) was lower than 100 g L,1. For higher BOD levels, the maximum values of biomass were 55 g L,1 (SSF) and 35 g L,1 (SmF). Micrographs of PUF preparations showed yeast growing within liquid lamellae, thinner than 100 µm, forming large horizontal aggregates. Yeast aggregates were much smaller in SmF than in SSF experiments; however, laccase expression was lower in PUF than in SmF, unless the methanol concentration was increased to 63 g L,1, which was inhibitory only to the SmF system. CONCLUSION: The results show that oxygen mass transfer is more efficient in SSF, which is related to the higher area/volume ratio compared with SmF. Induction differences may also be due to hindered diffusion of methanol within large yeast aggregates. Copyright © 2009 Society of Chemical Industry [source] Measurement of flow field in biofilm reactors by 3-D magnetic resonance imagingAICHE JOURNAL, Issue 11 2005Kevin P. Nott Abstract 3-D Magnetic resonance imaging (MRI) was used to measure the flow field of water in a packed-bed column containing Serratia sp. biofilm supported on polyurethane foam, and subsequently to follow a reaction which precipitates lanthanum phosphate on the biofilm. Sensitizing the MR image contrast to the fluid flow along the axis of the bioreactor provided better image-contrast between the foam and fluid compared to that based on MR signal intensity alone. After reaction, that same "velocity contrast" effectively defined the difference between blocked and unblocked regions by distinguishing between regions of flow and no flow. Data acquired during progressive blockage of reactors challenged at two different flow rates accord with reactor theory; thus, the faster flow rate replenished the reactants uniformly, whereas at the slower flow rate the reactants were concentration limited. MRI velocimetry was used to generate data that can be used to model reactors where the efficiency is progressively compromised by blockage due to precipitation. © 2005 American Institute of Chemical Engineers AIChE J, 2005 [source] Pressurised liquid extraction of polycyclic aromatic hydrocarbons from gas and particulate phases of atmospheric samplesJOURNAL OF SEPARATION SCIENCE, JSS, Issue 7 2009Maria Rosa Ras Abstract Pressurised liquid extraction (PLE) was applied to determine the atmospheric levels of 16 polycyclic aromatic hydrocarbons (PAHs) in the gas and particulate phases. The method involved high-volume air sampling with quartz fibre filters (QFFs) and polyurethane foam (PUF) plugs and analytes were subsequently extracted from the samples by PLE, and determined with GC-MS. We optimised the PLE conditions for the solvent, the number of cycles and extraction temperature. Recoveries were higher than 90% for most compounds. Method LODs and LOQs were between 0.001 and 0.02 ng/m3 and between 0.01 and 0.05 ng/m3. Air samples were taken from a site in the region of Tarragona in Catalonia, Spain, where one of the largest petrochemical complexes in southern Europe is located. The total concentration of PAHs were from 6.7 to 27.66 ng/m3, with predominant levels of PAHs appearing in the gas phase (48,81%), and an average level of benzo[a]pyrene, the most carcinogenic PAH, of 0.86 ng/m3. [source] Chromotropic acid-functionalized polyurethane foam: A new sorbent for on-line preconcentration and determination of cobalt and nickel in lettuce samplesJOURNAL OF SEPARATION SCIENCE, JSS, Issue 9 2006Valfredo Azevedo Lemos Abstract A chromotropic acid-functionalized polyurethane foam has been developed for use in an on-line preconcentration system for cobalt and nickel determination. The packing material was prepared by covalent coupling of chromotropic acid with the polyurethane foam through an azo group. Co and Ni ions were sorbed in the minicolumn, from which they could be eluted directly to the nebulizer-burner system of a flame atomic absorption spectrometer. Elution of cobalt and nickel from the minicolumn can be accomplished with 0.50 and 0.75 M HCl solutions, respectively. The enrichment factors obtained were 22 (Co) and 27 (Ni), for 60 s preconcentration time, and 57 (Co) and 59 (Ni), if a preconcentration time of 180 s was used. Under the optimum conditions, the proposed procedure allowed the determination of metals with detection limits of 0.43 (cobalt) and 0.52 ,g/L (nickel), respectively, on using preconcentration periods of 180 s. The accuracy of the developed procedure was evaluated by analysis of the certified reference materials NIST 1515 Apple Leaves and NIST 1570a Spinach Leaves. The method was applied to the analysis of lettuce samples. The contents of cobalt in the samples analyzed varied from 0.75 to 0.98 ,g/g. Nickel was not detected in the lettuce samples. [source] Oxypropylation of Lignins and Preparation of Rigid Polyurethane Foams from the Ensuing PolyolsMACROMOLECULAR MATERIALS & ENGINEERING, Issue 10 2005Hamid Nadji Abstract Summary: Different lignins were converted into polyols by a chain extension reaction with propylene oxide (PO). Thus, soda lignin from Alfa (Stipa tenacissima) (SL), organosolv lignin from hardwoods (OL), kraft lignin (KL) from softwood and oxidized organosolv lignin (OOL) were oxypropylated in a batch reactor at 180,°C in the presence of KOH as catalyst. The ensuing polyols were characterized by FTIR and 1H NMR spectroscopy, which showed that they had incorporated poly(propylene oxide) grafts into their structure. Their viscosity varied from 5 mPa,·,s to infinity, depending on the Lignin/PO ratio and their hydroxy index was in the range of 100,200, which made them suitable for rigid polyurethane foam (RPU) formulations. The RPUs thus obtained had a Tg of ca. 60,°C and a thermal conductivity of ,20 mW/m,·,K before ageing and ,25 mW/m,·,K after accelerated ageing for 10 d at 70,°C. The analyses of the gases inside the cells showed that these were mostly closed, since the partial pressure did not decrease significantly with ageing. Photograph of polyurethane foam made from OLOP. [source] Formation and characterization of polyurethane,vermiculite clay nanocomposite foamsPOLYMER ENGINEERING & SCIENCE, Issue 9 2008T. Umasankar Patro Nanocomposites of rigid polyurethane foam with unmodified vermiculite clay are synthesized. The clay is dispersed either in polyol or isocyanate before blending. The viscosity of the polyol is found to increase slightly on the addition of clay up to 5 pphp (parts per hundred parts of polyol by weight). The gel time and rise time are significantly reduced by the addition of clay, indicating that the clay acts as a heterogeneous catalyst for the foaming and polymerization reactions. X-ray diffraction and transmission electron microscopy of the polyurethane composite foams indicate that the clay is partially exfoliated in the polymer matrix. The clay is found to induce gas bubble nucleation resulting in smaller cells with a narrower size distribution in the cured foam. The closed cell content of the clay nanocomposite foams increases slightly with clay concentration. The mechanical properties are found to be the best at 2.3 wt% of clay when the clay is dispersed in the isocyanate; the compressive strength and modulus normalized to a density of 40 kg/m3 are 40% and 34% higher than the foam without clay, respectively. The thermal conductivity is found to be 10% lower than the foam without clay. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers [source] Ferrous iron oxidation by foam immobilized Acidithiobacillus ferrooxidans: Experiments and modelingBIOTECHNOLOGY PROGRESS, Issue 5 2009S. Jaisankar Abstract Ferrous iron bio-oxidation by Acidithiobacillus ferrooxidans immobilized on polyurethane foam was investigated. Cells were immobilized on foams by placing them in a growth environment and fully bacterially activated polyurethane foams (BAPUFs) were prepared by serial subculturing in batches with partially bacterially activated foam (pBAPUFs). The dependence of foam density on cell immobilization process, the effect of pH and BAPUF loading on ferrous oxidation were studied to choose operating parameters for continuous operations. With an objective to have high cell densities both in foam and the liquid phase, pretreated foams of density 50 kg/m3 as cell support and ferrous oxidation at pH 1.5 to moderate the ferric precipitation were preferred. A novel basket-type bioreactor for continuous ferrous iron oxidation, which features a multiple effect of stirred tank in combination with recirculation, was designed and operated. The results were compared with that of a free cell and a sheet-type foam immobilized reactors. A fivefold increase in ferric iron productivity at 33.02 g/h/L of free volume in foam was achieved using basket-type bioreactor when compared to a free cell continuous system. A mathematical model for ferrous iron oxidation by Acidithiobacillus ferrooxidans cells immobilized on polyurethane foam was developed with cell growth in foam accounted by an effectiveness factor. The basic parameters of simulation were estimated using the experimental data on free cell growth as well as from cell attachment to foam under nongrowing conditions. The model predicted the phase of both oxidation of ferrous in shake flasks by pBAPUFs as well as by fully activated BAPUFs for different cell loadings in foam. Model for stirred tank basket bioreactor predicted within 5% both transient and steady state of the experiments closely for the simulated dilution rates. Bio-oxidation at high Fe2+ concentrations were simulated with experiments when substrate and product inhibition coefficients were factored into cell growth kinetics. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [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] Composites of rigid polyurethane foam and cellulose fiber residueJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010M. C. Silva Abstract Rigid polyurethane composite foams were prepared with cellulose fibers as a filler. The cellulose fibers were an industrial residue of blanched cellulose pulp production. The influence of the cellulose fiber concentration on the structural, thermal, mechanical, and morphological properties of the foams was investigated. We also studied the influence of the cellulose fibers on the foam's resistance to fungal attack by placing a suspension of known fungus in contact with the surface of the foam and following the morphological evolution as a function of time (for 60 days). The increase in the cellulose filler concentration in the foams, up to 16% w/w with respect to the polyol, changed their properties as follows: (1) the cell size decreased, (2) the thermooxidative stability and mechanical properties remained approximately constant, (3) the thermal conductivity decreased slightly, and (4) fungal growth was observed. Therefore, a cellulosic fibrous industrial residue was rationally valorized as a filler in classical rigid polyurethane foams; this yielded materials with mechanical resistance and a susceptibility to fungi in a wet environment. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Microstructure and physical properties of open-cell polyolefin foamsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2009M. A. Rodriguez-Perez Abstract The cellular structure, physical properties, and structure,property relationships of novel open-cell polyolefin foams produced by compression molding and based on blends of an ethylene/vinyl acetate copolymer and a low-density polyethylene have been studied and compared with those of closed-cell polyolefin foams of similar chemical compositions and densities and with those of open-cell polyurethane foams. Properties such as the elastic modulus, collapse stress, energy absorbed in mechanical tests, thermal expansion, dynamic mechanical response, and acoustic absorption have been measured. The experimental results show that the cellular structure of the analyzed materials has interconnected cells due to the presence of large and small holes in the cell walls, and this structure is clearly different from the typical structure of open-cell polyurethane foams. The open-cell polyolefin foams under study, in comparison with closed-cell foams of similar densities and chemical compositions, are good acoustic absorbers; they have a significant loss factor and lower compressive strength and thermal stability. The physical reasons for this macroscopic behavior are analyzed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Modeling the dynamics of reactive foaming and film thinning in polyurethane foamsAICHE JOURNAL, Issue 2 2010G. Harikrishnan Abstract Flexible polyurethane foams are widely used in cushioning and packaging applications. A model for the dynamics of formation of polyurethane foams is presented, which includes thinning of foam lamellae. Experimental measurements for water blown flexible foam formulations at different water concentrations are presented to validate the model. Adiabatic temperature rise measurements during foaming are used to obtain the kinetic parameters of the reactions of isocyanate with polyol and water. The variation of foam density during foaming is studied by weight loss and video shooting methods and both are compared to estimate the amount of blowing gas lost during foaming. The average thickness of the foam lamellae of the solid foam is obtained by SEM measurements. The predictions of the model show good agreement with the experimental measurements of temperature and density with time and the final lamellar thickness. The results are important for understanding the cell opening process. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Modeling for batch phenol biodegradation with immobilized Alcaligenes faecalisAICHE JOURNAL, Issue 4 2006Xiaoqiang Jia Abstract Intrinsic cell growth and phenol biodegradation kinetics of Alcaligenes faecalis were studied in shaking flasks. Batch phenol biodegradation experiments were carried out in a 7.5 L fermentor with immobilized Alcaligenes faecalis in polyurethane foams. A double-layer reaction-diffusion model was developed to describe the dynamic behaviors of batch phenol biodegradation processes. Phenol degradation (within the cell-immobilized polyurethane foams as well as in the main liquid phase) and cell growth (within the cell-immobilized polyurethane foams only) at different initial phenol concentrations were simulated and analyzed in terms of both biodegradation time and layer radius course. The good agreement between the model simulations and the experimental measurements for phenol degradation in the main liquid phase validates the proposed double-layer reaction-diffusion model. © 2005 American Institute of Chemical Engineers AIChE J, 2006 [source] Auxetic compliant flexible PU foams: static and dynamic propertiesPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 3 2005F. Scarpa Abstract The paper describes the manufacturing and tensile testing of auxetic (negative Poisson's ratio) thermoplastic polyurethane foams, both under constant strain rate and sinusoidal excitation. The foams are produced from conventional flexible polyurethane basis following a manufacturing route developed in previous works. The Poisson's ratio behaviour over tensile strain has been analyzed using an Image Data processing technique based on Edge Detection from digital images recorded during quasi-static tensile test. The samples have been subjected to tensile and compressive tests at quasi-static and constant strain-rate values (up to 12 s,1). Analogous tests have been performed over iso-volumetric foams samples, i.e., foams subjected to the same volumetric compression of the auxetic ones, exhibiting a near zero Poisson's ratio behaviour. The auxetic and non-auxetic foams have been also tested under sinusoidal cycling load up to 10 Hz, with maximum pre-strain applied of 12%. The hysteresis of the cycling loading curve has been measured to determine the damping hysteretic loss factor for the various foams. The measurements indicate that auxetic foams have increased damping loss factor of 20% compared to the conventional foams. The energy dissipation is particularly relevant in the tensile segment of the curve, with effects given by the pre-strain level imposed on the samples. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Simulation of the percolation of water into rigid polyurethane foams at applied hydraulic pressuresPOLYMER ENGINEERING & SCIENCE, Issue 7 2006Pravakar Mondal The hydraulic resistance of polyurethane foams is studied by means of simulations of water penetration into model foams. The model foams of cubical shape are constructed by generating the centers of the cells randomly. The strength of the window separating two cells is assumed to be a function of the distance between the centers of the cells in one set of computations. In another set of computations the strengths of the windows are assigned randomly from a specified distribution. The foam is exposed to an elevated pressure at its boundaries and water penetrates into the foam by rupturing the windows with strengths lesser than the applied pressure. The variation of equilibrium volume fraction of the foam filled with water for increasing hydraulic pressures shows typical percolation behavior: there is a sharp increase in the volume filled beyond a threshold pressure. Simulations show that beyond a certain sample size there is no change in the percolation curve with sample size, and indicate that it is mainly the weaker windows that control the hydraulic resistance of the foam. The simulation results are compared with experimental data. POLYM. ENG. SCI. 46:970,983, 2006. © 2006 Society of Plastics Engineers [source] Long-term performance of environmentally-friendly blown polyurethane foamsPOLYMER ENGINEERING & SCIENCE, Issue 3 2005M. Modesti We studied the long-term performance of new environmentally-friendly blowing agents for polyurethane foams. Several blowing agents, hydrofluorocarbons, hydrocarbons, and a possible hydrochlorofluorocarbon substitute (dimethoxymethane), as well as hydrochlorofluorocarbons, were analyzed. The determination of effective diffusion coefficients (knowledge of which is required to study long-term performance) was performed by means of a classical gas chromatographic technique and by a new method based on infrared spectroscopy. The reliability of the experimental procedure used is showed by comparing experimental and predicted aging, as the slope of the aging curve (i.e., thermal conductivity vs. time) depends only on effective diffusion coefficients. Our study of long-term performance of foams blown with alternative blowing agents shows that hydrofluorocarbons represent a proper alternative to hydrochlorofluorocarbons, as the foams show similar initial thermal conductivity and a slower aging rate (i.e., better long-term performance). POLYM. ENG. SCI. 45:260,270, 2005. © 2005 Society of Plastics Engineers. [source] Ferrous iron oxidation by foam immobilized Acidithiobacillus ferrooxidans: Experiments and modelingBIOTECHNOLOGY PROGRESS, Issue 5 2009S. Jaisankar Abstract Ferrous iron bio-oxidation by Acidithiobacillus ferrooxidans immobilized on polyurethane foam was investigated. Cells were immobilized on foams by placing them in a growth environment and fully bacterially activated polyurethane foams (BAPUFs) were prepared by serial subculturing in batches with partially bacterially activated foam (pBAPUFs). The dependence of foam density on cell immobilization process, the effect of pH and BAPUF loading on ferrous oxidation were studied to choose operating parameters for continuous operations. With an objective to have high cell densities both in foam and the liquid phase, pretreated foams of density 50 kg/m3 as cell support and ferrous oxidation at pH 1.5 to moderate the ferric precipitation were preferred. A novel basket-type bioreactor for continuous ferrous iron oxidation, which features a multiple effect of stirred tank in combination with recirculation, was designed and operated. The results were compared with that of a free cell and a sheet-type foam immobilized reactors. A fivefold increase in ferric iron productivity at 33.02 g/h/L of free volume in foam was achieved using basket-type bioreactor when compared to a free cell continuous system. A mathematical model for ferrous iron oxidation by Acidithiobacillus ferrooxidans cells immobilized on polyurethane foam was developed with cell growth in foam accounted by an effectiveness factor. The basic parameters of simulation were estimated using the experimental data on free cell growth as well as from cell attachment to foam under nongrowing conditions. The model predicted the phase of both oxidation of ferrous in shake flasks by pBAPUFs as well as by fully activated BAPUFs for different cell loadings in foam. Model for stirred tank basket bioreactor predicted within 5% both transient and steady state of the experiments closely for the simulated dilution rates. Bio-oxidation at high Fe2+ concentrations were simulated with experiments when substrate and product inhibition coefficients were factored into cell growth kinetics. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] | |||||||||||||