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High Loadings (high + loading)
Selected AbstractsCrosslinked Polyacrolein Microspheres with High Loading of Aldehyde Groups for Use as Scavenger Resins in Organic Synthesis,MACROMOLECULAR RAPID COMMUNICATIONS, Issue 19 2004Chao Lin Abstract Summary: Suspension polymerization yielded microspheres (40,50 ,m) of polyacrolein. Smooth and rugged surfaces can be created by varying the polymerization procedure. We have shown that the polyacrolein resins with a high loading of aldehyde groups serve as effective scavengers for primary amines and may be used to remove compounds bearing amino groups in the combinatorial synthesis of compound libraries. Copolymerization with styrene can help to separate the adjacent aldehyde groups, thus making the functional groups more available in organic reactions. The polyacrolein resins in the aldehyde form or after appropriate chemical modifications may also be useful as support materials in solid-phase synthesis. The SEM image of macroporous polyacrolein microspheres with toluene as porogen prepared by free radical polymerization. [source] A New Method for Post-Synthesis Coating of Zirconia on the Mesopore Walls of SBA-15 Without Pore Blocking,ADVANCED MATERIALS, Issue 11 2008Cheralathan Kanakkampalayan Krishnan Zirconia coating of the mesopore walls of the mesoporous silica material SBA-15 is achieved by internal hydrolysis of a zirconia precursor, which is loaded inside the mesopores, using NH3/H2O vapor at elevated temperature and subsequent calcination (see figure). High loadings of zirconia, more than 30 wt%, can be coated on the mesopore walls without any pore blocking. [source] Ferrocenyl-functionalized long chain branched polydienesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2009Frederik Wurm Abstract A convenient two-step approach for the synthesis of ferrocenyl-functionalized long chain branched polydienes, based on both butadiene and isoprene, respectively, is presented. Classical living anionic polymerization was used to synthesize different ABn type poly(diene) macromonomers with moderate molecular weights between 1700 and 3200 g/mol and narrow polydispersity. Quantitative end-capping with chlorodimethylsilane resulted in the desired ABn macromonomer structures. In the ensuing Pt-catalyzed hydrosilylation polyaddition, branched, functionalized polydienes were obtained by a concurrent ABn + AR type of copolymerization with mono- and difunctional ferrocenyl silanes (fcSiMe2H or fc2SiMeH). Molecular weights of the branched polymers were in the range of 10,000 to 44,000 g/mol (SEC/MALLS). Because of the large number of functional end groups, high loading with ferrocene units up to 63 wt % of ferrocene was achieved. Detailed studies showed full conversion of the functional silanes and incorporation into the branched polymer. Further studies using DSC, TGA, and cyclovoltammetry (CV) measurements have been performed. Electrochemical studies demonstrated different electrochemical properties for fcSiMe2 - and fc2SiMe-units. The CVs of polymers modified with diferrocenylsilane units exhibit the pattern of communicating ferrocenyl sites with two distinct, separate oxidation waves. The polymers were also deposited on an electrode surface and the electrodes investigated via CV, showing formation of electroactive films with promising results for the use of the materials in biosensors. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2518,2529, 2009 [source] Crosslinked Polyacrolein Microspheres with High Loading of Aldehyde Groups for Use as Scavenger Resins in Organic Synthesis,MACROMOLECULAR RAPID COMMUNICATIONS, Issue 19 2004Chao Lin Abstract Summary: Suspension polymerization yielded microspheres (40,50 ,m) of polyacrolein. Smooth and rugged surfaces can be created by varying the polymerization procedure. We have shown that the polyacrolein resins with a high loading of aldehyde groups serve as effective scavengers for primary amines and may be used to remove compounds bearing amino groups in the combinatorial synthesis of compound libraries. Copolymerization with styrene can help to separate the adjacent aldehyde groups, thus making the functional groups more available in organic reactions. The polyacrolein resins in the aldehyde form or after appropriate chemical modifications may also be useful as support materials in solid-phase synthesis. The SEM image of macroporous polyacrolein microspheres with toluene as porogen prepared by free radical polymerization. [source] Recycling of silicone rubber waste: Effect of ground silicone rubber vulcanizate powder on the properties of silicone rubberPOLYMER ENGINEERING & SCIENCE, Issue 2 2003Arun Ghosh The silicone rubber vulcanizate powder (SVP) obtained from silicone rubber by mechanical grinding exists in a highly aggregated state. The particle size distribution of SVP is broad, ranging from 2 µm to 110 µm with an average particle size of 33 µm. X-ray Photoelectron Spectroscopy (XPS) and Infrared (IR) Spectroscopy studies show that there is no chemical change on the rubber surface following mechanical grinding of the heat-aged (200°C/10 days) silicone rubber vulcanizate. Addition of SVP in silicone rubber increases the Mooney viscosity, Mooney scorch time, shear viscosity and activation energy for viscous flow. Measurement of curing characteristics reveals that incorporation of SVP into the virgin silicone rubber causes an increase in minimum torque, but marginal decrease in maximum torque and rate constant of curing. However, the activation energy of curing shows an increasing trend with increasing loading of SVP. Expectedly, incorporation of SVP does not alter the glass-rubber transition and cold crystallization temperatures of silicone rubber, as observed in the dynamic mechanical spectra. It is further observed that on incorporation of even a high loading of SVP (i.e., 60 phr), the tensile and tear strength of the silicone rubber are decreased by only about 20%, and modulus dropped by 15%, while the hardness, tension set and hysteresis loss undergo marginal changes and compression stress-relaxation is not significantly changed. Atomic Force Microscopy studies reveal that incorporation of SVP into silicone rubber does not cause significant changes in the surface morphology. [source] Emulsion copolymerization of styrene and sodium styrene sulfonate: kinetics, monomer reactivity ratios and copolymer propertiesPOLYMER INTERNATIONAL, Issue 1 2009Dhamodaran Arunbabu Abstract BACKGROUND: The synthesis of poly[styrene- co -(sodium styrene sulfonate)], poly(S- co -NaSS), with a high loading of sulfonate groups is of current interest owing to its potential use in numerous areas. A series of these copolymers with various sulfonate loads were synthesized using the emulsion polymerization technique with a study of the copolymerization kinetics, monomer reactivity ratio and copolymer properties. RESULTS: The copolymerization kinetics are significantly enhanced with an increase of NaSS feed in the polymerization. Monomer reactivity ratios were determined from NMR data by employing the Fineman,Ross and Kelen,Tüdös methods. Styrene (r1) and NaSS (r2) reactivity ratios are 0.5 and 10, respectively. The colloidal particle size of the copolymers depends upon the NaSS composition. The thermal stability of the copolymers is greatly enhanced with higher NaSS content in the copolymer backbone. Higher glass transition temperatures are observed for the copolymers with higher NaSS content. CONCLUSION: The reactivity ratio values suggest that styrene prefers to form copolymers whereas NaSS produces homopolymers. It is also found that styrene copolymerization with NaSS is only twice as fast as homopolymerization. In contrast, NaSS homopolymerization is ten times faster than NaSS copolymerization with styrene. The NaSS content in the copolymer backbone affects the thermal stability and the glass transition of the copolymers. Copyright © 2008 Society of Chemical Industry [source] Biotransformation of R -2-hydroxy-4-phenylbutyric acid by D -lactate dehydrogenase and Candida boidinii cells containing formate dehydrogenase coimmobilized in a fibrous bed bioreactorBIOTECHNOLOGY & BIOENGINEERING, Issue 2 2005Yunling Bai Abstract R -2-hydroxy-4-phenylbutyric acid (R-HPBA) is an important intermediate in the manufacture of angiotensin converting enzyme inhibitors. In this work, a recombinant D -lactate dehydrogenase (LDH) was used to transform 2-oxo-4-phenylbutyric acid (OPBA) to R-HPBA, with concomitant oxidation of ,-nicotinamide adenine dinucleotide (NADH) to NAD+. The cofactor NADH was regenerated by formate dehydrogenase (FDH) present in whole cells of Candida boidinii, which were pre-treated with toluene to make them permeable. The whole cells used in the process were more stable and easier to prepare as compared with the isolated FDH from the cells. Kinetic study showed that the reaction rate was dependent on the concentration of cofactor, NAD+, and that both R-HPBA and OPBA inhibited the reaction. A novel method for co-immobilization of whole cells and LDH enzyme on cotton cloth was developed using polyethyleneimine (PEI), which induced the formation of PEI,enzyme,cell aggregates and their adsorption onto cotton cloth, leading to multilayer co-immobilization of cells and enzyme with high loading (0.5 g cell and 8 mg LDH per gram of cotton cloth) and activity yield (,>,95%). A fibrous bed bioreactor with co-immobilized cells and enzyme on the cotton cloth was then evaluated for R-HPBA production in fed-batch and repeated batch modes, which gave relatively stable reactor productivity of 9 g/L,·,h and product yield of 0.95 mol/mol OPBA when the concentrations of OPBA and R-HPBA were less than 10 g/L. © 2005 Wiley Periodicals, Inc. [source] The Forensic Inpatient Observation Scale (FIOS): development, reliability and validityCRIMINAL BEHAVIOUR AND MENTAL HEALTH, Issue 3 2001Irma G.H. Timmerman Introduction Re-offending, as a measure of success in forensic psychiatry, gives no information about other behaviours that may have changed. The development of the Forensic Inpatient Observation Scale (FIOS), an observation instrument to assess the non-offending functioning of forensic patients, is described. Study 1 In the first study the development of the initial item pool of the FIOS is described. This resulted in an instrument consisting of 78 items and seven scales. The internal reliability of the scales ranged from 0.78 to 0.91. The inter-rater reliability of the scales varied from 0.50 to 0.85 and the test,retest reliability over a period of three weeks was high for most scales, ranging from 0.74 to 0.89. Study 2 In the second study the FIOS was developed further in another sample of forensic patients. This time exploratory factor analysis with Varimax rotation and post hoc reliability analysis were applied to determine the factor structure among the items. This resulted in an item pool of 35 items, among which six factors could be distinguished that closely resemble the factor structure of the FIOS in study one: (1) self-care, (2) social behaviour, (3) oppositional behaviour, (4) insight offence/ problems, (5) verbal skills and (6) distress. Most items have high loadings on the factor they are assigned; 29 items have a loading of 0.60 or higher. The internal consistency of the scales ranges from 0.73 to 0.91 and the scales appear to be measuring independent constructs. Twenty-five out of the 35 items have an inter-rater correspondence of 90% or higher and 30 out of 35 items have an inter-rater correspondence of 87.5% or higher. The inter-rater reliability on the scale level, however, was somewhat less satisfying with correlations ranging from 0.50 to 0.69. Discussion It is argued that training the observers on a more regular basis will improve the inter-rater reliability. There is some evidence for the convergent validity of the FIOS. The FIOS has some advantages over existing inpatient scales in that it is developed specifically for forensic patients, it does not particularly focus on axis 1 symptoms but includes oppositional behaviour and attitudes to offending. Copyright © 2001 Whurr Publishers Ltd. [source] An analytical solution of one-dimensional consolidation for soft sensitive soil groundINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 9 2004Yun-Min Chen Abstract An analytical solution of one-dimensional consolidation for soft sensitive soil ground is presented. The moving boundary is introduced to indicate the notable change of consolidation behaviour of sensitive soil with the increase of stress level. It is assumed that the soil structure of the upper subsoil gradually destroys downwards with the dissipation of pore pressure, and the coefficient of consolidation as well as the coefficient of permeability of the upper subsoil become small, which hinders the dissipation of pore pressure of the lower subsoil. The consolidation degree curve obtained from the present solution is found to lie between the two curves obtained from Terzaghi one-dimensional consolidation solution with the parameters of the undisturbed soil and the remolded soil. The calculated results provide a new explanation for a general phenomenon in the consolidation of soft sensitive soil ground, as that for high loadings the consolidation is longer than for small ones. It should be pointed out from this study that both the deep mixing method and the long vertical drains methods are effective techniques for improving deep sensitive soil ground. Copyright © 2004 John Wiley & Sons, Ltd. [source] Biomedical Applications of Layer-by-Layer Assembly: From Biomimetics to Tissue Engineering,ADVANCED MATERIALS, Issue 24 2006Z. Tang Abstract The design of advanced, nanostructured materials at the molecular level is of tremendous interest for the scientific and engineering communities because of the broad application of these materials in the biomedical field. Among the available techniques, the layer-by-layer assembly method introduced by Decher and co-workers in 1992 has attracted extensive attention because it possesses extraordinary advantages for biomedical applications: ease of preparation, versatility, capability of incorporating high loadings of different types of biomolecules in the films, fine control over the materials' structure, and robustness of the products under ambient and physiological conditions. In this context, a systematic review of current research on biomedical applications of layer-by-layer assembly is presented. The structure and bioactivity of biomolecules in thin films fabricated by layer-by-layer assembly are introduced. The applications of layer-by-layer assembly in biomimetics, biosensors, drug delivery, protein and cell adhesion, mediation of cellular functions, and implantable materials are addressed. Future developments in the field of biomedical applications of layer-by-layer assembly are also discussed. [source] Effect of boron-containing materials on the flammability and thermal degradation of polyamide 6 composites containing melamineJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010Mehmet Do Abstract Three different boron-containing substances,zinc borate (ZnB), borophosphate (BPO4), and a boron- and silicon-containing oligomer (BSi),were used to improve the flame retardancy of melamine in a polyamide 6 (PA-6) matrix. The combustion and thermal degradation characteristics of PA-6 composites were investigated with the limiting oxygen index (LOI), the UL-94 standard, thermogravimetric analysis (TGA)/Fourier transform infrared (FTIR) spectroscopy, and differential scanning calorimetry (DSC). A slight increase was seen in the LOI values of a sample containing BSi (1 wt %). BPO4 at high loadings showed a V0 rating (indicating the best flame retardancy) and slightly lower LOI values in comparison with samples with only melamine. For ZnB and BSi, glassy film and char formation decreased the dripping rate and sublimation of melamine, and this led to low LOIs. According to the TGA,FTIR results, the addition of boron compounds did not change the decomposition product distribution of melamine and PA-6. The addition of boron compounds affected the flame retardancy by physical means. The TGA data showed that boron compounds and melamine reduced the decomposition temperature of PA-6. According to the DSC data, the inclusion of boron compounds increased the onset temperature of sublimation of melamine and also affected the flame retardancy negatively. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Influence of a novel castor-oil-derived additive on the mechanical properties and oxygen diffusivity of polystyreneJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2010Markus Klinger Abstract Mechanical properties, densities, and oxygen diffusion coefficients have been measured in polystyrene samples (PS) as a function of additive loading. The additive employed is based on castor oil, and is a desirable alternative to phthalates. Tensile strength measurements indicate the additive renders PS stronger at low loadings, i.e. it antiplasticizes the material. In contrast, the additive plasticizes PS at high loadings. Specific volumes and oxygen diffusion coefficients do not show this dual behavior. Rather, one observes a monotonic decrease in density and oxygen diffusivity with an increase in additive loading. This suggests that the larger segmental motions responsible for the macroscopic properties of the polymer are influenced by the additive in a different manner than the local motions and confined changes in free volume that govern the mobility of oxygen. These data indicate that antiplasticization cannot be predicted solely from diffusivity and density measurements and, vice versa, trends in diffusivity cannot be deduced from mechanical measurements alone. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Volatile fatty acid production during anaerobic mesophilic digestion of solid potato wasteJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2004Wilson Parawira Abstract The production of volatile fatty acids by anaerobic digestion of solid potato waste was investigated using a batch solid waste reactor with a working capacity of 2 dm,3 at 37°C. Solid potato waste was packed into the digester and the organic content of the waste was released by microbial activity by circulating water over the bed, using batch loads of 500 g or 1000 g potato waste. The sequence of appearance of the volatile fatty acids was (acetic, propionic); (n -butyric); (n -valeric, iso-valeric, caproic); (iso-butyric). After 300 h digestion of potato waste on a small scale, the fermentation products were chiefly (mg g,1 total VFAs): acetic acid (420), butyric acid (310), propionic acid (140) and caproic acid (90), with insignificant amounts of iso-butyric acid, n -valeric and iso-valeric acids. When the load of potato solids was increased, the volatile fatty acid content was similar, but butyric acid constituted 110 mg g,1 and lactic acid 400 mg g,1 of the total volatile fatty acids. The maximum soluble chemical oxygen demand (COD) achieved under the experimental conditions used was 27 and 37 g COD dm,3 at low and high loadings of potato solids, respectively. The total volatile fatty acids reached 19 g dm,3 of leachate at both loads of potato solid waste. Gas production was negligible, indicating that methanogenic activity was effectively inhibited. Copyright © 2004 Society of Chemical Industry [source] Experimental validation of a rigorous absorber model for CO2 postcombustion captureAICHE JOURNAL, Issue 4 2007Finn Andrew Tobiesen Abstract A rigorous rate-based model for acid gas absorption was developed and validated against mass-transfer data obtained from a 3-month campaign in a laboratory pilot-plant absorber in which the experimental gas,liquid material balance was within an average of 6%. The mass-transfer model is based on the penetration theory where the liquid film is discretized using an adaptive grid. The model was validated against all data and the deviation between simulated and averaged gas and liquid side experimental mass-transfer rates yielded a total variability of 6.26%, while the total average deviation was 6.16%. Simpler enhancement factor mass-transfer models were also tested, but showed slight over-prediction of mass-transfer rates. A sensitivity analysis shows that the accuracy of the equilibrium model is the single most important source of deviation between experiments and model, in particular at high loadings. Experimental data for the absorber in the integrated pilot plant are included. © 2007 American Institute of Chemical Engineers AIChE J, 2007 [source] High Surface Area, Mesoporous, Glassy Alumina with a Controllable Pore Size by Nanocasting from Carbon AerogelsCHEMISTRY - A EUROPEAN JOURNAL, Issue 5 2005Wen-Cui Li Dr. Abstract A strategy to synthesize amorphous, mesoporous alumina by nanocasting has been developed, involving carbon aerogel as a hard template and aluminum nitrate solution as an alumina precursor. The alumina generated exhibits small, transparent granules with a 3,6 mm diameter and has inherited the three-dimensional network structure of the carbon template. The mesopore surface area of the alumina can be as high as 365 m2,g,1, and the pore volume reaches 1.55 cm3,g,1 after calcination at 600,°C in air for 8 h. The pore parameters can be varied within a certain range by variation of the carbon aerogel template and the loading amount of the alumina precursor. At high loadings, the obtained glassy alumina clearly has a bimodal pore size distribution in the mesopore range. [source] | |||||||||||||