bluuebunny/crossref_metadata_2025_split huggingface dataset:
Xylylene Polymers
Authors: Beach W. F. 
Published: July 2004

AbstractPinhole‐free coatings of outstanding conformality and thickness uniformity are produced by exposing a substrate to a controlled deposition of pure gaseous monomer through the unique chemistry ofp‐xylylene, which is thermally stable but very reactive toward polymerization with other like molecules, in a process known as vapor deposition polymerization (VDP). A high molecular weight coating of poly(p‐xylylene) (PPX) is produced. Recent VDP developments are stressed in the article.The convenient generation of the extremely reactive monomer is accomplished by thermal cleavage of its stable dimer,cyclo‐di‐p‐xylylene (DPX), commercially in the Gorham process. The PPXs formed as coatings in the Gorham process are referred to generically as parylenes. Parylene N, Parylene C, and Parylene D are polymer coatings produced by the Gorham process using the dimers DPXN, DPXC, and DPXD, respectively. These dimers are the feedstocks for the coating process. The Parylene C monomer, chloro‐p‐xylylene, has become the de facto performance standard owing to its room temperature volatility. VDP processes using means other than pyrolytic cleavage of DPX to generate reactive monomer, none practiced commercially, include photopolymerization and plasma polymerization, as well as imidization to produce polyimide films.Manufacture of commercial DPXN is through two routes: direct pyrolysis ofp‐xylene and the Hofmann elimination route. DPXC and DPXD are prepared from DPXN by chlorinating. Thermodynamic considerations of the parylene process by VDP are covered. The importance of the physical processes of condensation and diffusion in VDP are treated, as is the propagation reaction.VDP produces films of uniform thickness having excellent conformality and purity. Electrical properties merit their use in electronic construction. Barrier, spectral, and optical properties are also useful. Crystallinity determines important properties of mechanical strength at elevated temperatures and solvent resistance, which constitute the principal advantages of PPX materials. Uses include circuit boards, hybrid circuits, semiconductors, capacitors, the bathythermograph, medical uses (as in pacemakers), artifact conservation, and in laser fusion targets. They are also used as barrier coatings, in corrosion control, and as dry lubricants. The dimers present little concern in handling and storage to an experienced operator. In ancillary operations such as cleaning or adhesion promotion, suitable precautions given in manufacturers' Material Safety Data Sheets should be observed.
Yeasts
Authors: Maloney Daniel 
Published: July 2004

AbstractYeasts are probably the oldest cultivated plants: their use dates to 3000BCor earlier. They are eukaryotic organisms, ie, they have a defined nucleus surrounded by a nuclear membrane and organized cytoplasmic organelles (mitochondria, peroxisomes, vacuoles, etc). The recognition of yeasts as a coherent group of microorganisms and of their role in fermentation generally preceded their taxonomic classification. They are fungi that exist as single cells during at least some part of their life cycle, they have no photosynthetic ability and are not motile. All the major groups of fungi,Basidiomycetes,Ascomycetes,Phycomycetes, and theFungi imperfecti, include species that have adopted a yeast phase. Yeasts usually reproduce vegetatively by budding or fission, but parasexual and sexual reproduction occur as well in most yeasts. There are extensive and authoritative texts on yeast taxonomy and identification. Among those listed, the genusSaccharomycesis of greatest practical and economic importance for the baking, beer, and wine industries, as well as for the production of biomass. This article emphasizes the biology and industrial use ofSaccharomyces cerevisiae. Due to its importance in the study of basic cell biology, reviews ofSaccharomycesgenetics and molecular biology appear regularly. Other yeasts participate in alcoholic fermentations and occur as food‐spoilage organisms or pathogens.
Zinc and Zinc Alloys
Authors: Goodwin Frank E. 
Published: July 2004

AbstractZinc is a relatively active metal and its compounds are stable. Since it is not found free in nature, it was discovered later than less‐reactive metals. The main application of zinc is to protect iron and other metals from corrosion. Occurrence and properties of zinc are discussed. Processing of the ore requires concentration of the ore followed by roasting, or reduction by electrolytic methods. Economic data, specifications and grades, health and safety factors are given. The uses of zinc coatings on iron and steel are as die‐casting alloys and foundry alloys. Rolled zinc and zinc dust and powder also find industrial use. Ores exploited for zinc invariably contain one or more other valuable metals, such as cadmium and mercury.
Zinc Compounds
Authors: Goodwin Frank E. 
Published: July 2004

AbstractZinc usually occurs as the sulfide, but significant quantities of the oxide, carbonate, silicate, and basic compounds of the latter two are mined. Properties of many of the compounds of zinc are given, with special attention given to zinc oxide, zinc chloride, and zinc sulfate. The oxide is important because it completely absorbs ultraviolet light below 366 nm and it is unique among white pigments. Details on the American (Direct) process and French (Indirect) Process for the production and processing of zinc are given as well as a discussion of secondary zinc oxide obtained from scrap. Zinc is needed for the proper functioning of plants and animals and this is discussed along with health and safety aspects, uses, and economics.
Fluorine Compounds, Inorganic, Zirconium
Authors: Meshri Dayal T. 
Published: July 2004

Abstract

Three binary zirconium fluorides, ZrF
2
, ZrF
3
, and ZrF
4
, are known to exist. The most commercially important zirconium fluoride compounds are zirconium tetrafluoride and fluorozirconic acid and its salts. ZrF
4
is used in the production of heavy‐metal fluoride glasses. These ultrapure glasses are utilized as optical fibers. Hexafluorozirconic acid is used in metal finishing and its alkali metal salts in the manufacture of abrasive grinding wheels. The properties, manufacture, and uses of the various zirconium fluorine‐containing compounds are discussed.
Ethylene polymerization with imine and phosphine nickel complexes containing isothiocyanate
Authors: Crossetti Geraldo L. , Dias Marcos L. , Queiroz Bruno T. , Silva Luciana P. , Ziglio Cláudio M. , Bomfim João A. S. , Filgueiras Carlos A. L. 
Published: July 2004

AbstractThree isothiocyanate complexes of nickel(II) containing diimine [ArNC(Me)C(Me)NAr]Ni‐ (NCS)2 (1), iminophosphine [Ph2PC6H4CHNAr]Ni(NCS)2 (2), or diphosphine (dppe)Ni(NCS)2 (3), [Ar = 2, 6‐iPr‐C6H3; dppe = 1, 2‐bis(diphenylphosphine)ethane] were synthesized and examined for ethylene polymerization activated by methylaluminoxane (MAO). Their behavior was compared with those of the corresponding halide analogues [ArNC(Me)C(Me)NAr]NiBr2 (4), [Ph2PC6H4CHNAr]NiBr2 (5), and (dppe)NiCl2 (6). The diimines showed the highest polymerization activity. Replacement of the halide for the NCS pseudo halide affected the activity and decreased the molecular weight of the polymer formed. The highest molecular weights were obtained with the diimine complexes. Highly branched polyethylenes were obtained with the bulkier complexes 1 and 4. Replacement of the halide for NCS in the diimine complexes also caused an increase in the branching content, whereas the opposite occurs for the iminophosphine complexes. The different activities and behavior of the catalyst systems with halide versus NCS in the polymerization of ethylene and the characteristics of the final products suggest a modification in the active species caused by the non‐chelating ligand. Polymer molecular weight and branching content is dependent on the MAO/Ni molar ratio and on the working temperature. Copyright © 2004 John Wiley & Sons, Ltd.
Crystallographic report: [(1,3‐Bis(4‐pyridyl)propane)(diaqua)zinc(II)] diperchlorate dihydrate
Authors: Choi Seung Hoon , Ryu Ji Young , Lee Jun Yong , Myoung Young Chan , Kim Cheal , Kim Youngmee , Song Byung Ho 
Published: July 2004

AbstractFour ligands of 1,3‐bis(4‐pyridyl)propane and two water molecules are coordinated to the zinc(II) atom so that the coordination geometry closely resembles a trans‐N4O2 octahedral environment. Copyright © 2004 John Wiley & Sons, Ltd.
Crystallographic report: Tricarbonyl(η5‐cyclopentadienyl)(dichloroindium) molybdenum
Authors: Grabowy T. , Wagner C. , Merzweiler K. 
Published: July 2004

AbstractIn the solid state, [{Cp(CO)3Mo}InCl2]∞ forms a one‐dimensional coordination polymer in which the indium atoms are coordinated by four chlorine atoms (InCl: 2.448(2)–3.004(2) Å) and a {Cp(CO)3Mo} group (InMo: 2.750(1) Å) in a distorted trigonal bipyramidal environment. Copyright © 2004 John Wiley & Sons, Ltd.
The role of cobalt, copper, nickel, and zinc in the DNA replication inhibitory activity of p‐aminophenyl triphenylporphyrin
Authors: Barragán Efraín , Gordillo Barbara , Vargas Genaro , Velazco Luis 
Published: July 2004

AbstractCationic porphyrins have been widely used as tumor localizers in cancer therapies. When cationic porphyrins are flat they intercalate with double‐stranded DNA, duplexes of RNA or RNA–DNA. The antitumor activity of some cationic porphyrins depends on their interaction with human telomeric quadruplexes. Here, we report that noncationic meso‐(4‐aminophenyl)triphenylporphyrin (H2TPPNH2) (3) and its cobalt, copper, nickel, and zinc metallo derivatives (4–7) have DNA replication inhibitory activity in B16 mouse melanoma line cells. By means of quantification of 3HdTT radio‐labeled DNA, we observed that the nonplanar porphyrin [CoTPPNH2] has the highest activity against carcinogenic DNA replication. Copyright © 2004 John Wiley & Sons, Ltd.
Physical, mechanical, and thermal properties of PVC/PMMA blends in relation to their morphologies
Authors: Chakrabarti Rupa , Das Molay , Chakraborty Debabrata 
Published: July 2004

AbstractThe effect of blending poly (methyl methacrylate) (PMMA) in various proportions with suitably stabilized and plasticized poly (vinyl chloride) (PVC) was studied with reference to their physical, mechanical, and thermal properties. The resulting morphologies of the various blends were also studied to find a suitable explanation of these properties. The physical and mechanical properties of such polyblends revealed a substantial increase in toughness accompanied with unusual increase in modulus and ultimate tensile strength after an initial drop at the initial stages of PMMA incorporation compared to pure reference compound PVC. The toughening effect, however, undergoes a reduction with increasing proportion of PMMA but it never goes below that of pure PVC (reference compound) within the ranges of PMMA incorporation under study. The various polyblends exhibit the two‐stage degradation typical of PVC and all of them possess higher thermal stability as manifested in their characteristic thermograms. The softening characteristics imparted by PMMA were also reflected in their respective TMA curves. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2721–2730, 2004
New insights into the degradation mechanism of poly(vinyl chloride), based on the action of novel costabilizers. I.
Authors: Santamaría E. , Edge M. , Allen N. S. , Harvey H. B. , Mellor M. , Orchison J. 
Published: July 2004

AbstractRecent legislation introduced to limit the use of heavy metal stabilizers (cadmium based) in poly(vinyl chloride) (PVC) has necessitated the use of organic costabilizers as adjuncts to alternative main stabilizer systems (barium/zinc or calcium/zinc). It has been suggested in the literature that costabilizers substitute allylic chlorine by a C‐alkylation reaction; costabilizers act as reverse catalysts for the initiation of degradation by complexing the π‐electron sites that would otherwise have an activating affect on labile chlorines; and costabilisers destroy carbonylallyl active sites by proton donation. To rationalize this debate, the focus of this paper is to elucidate the type of interactions that occur between a model compound for PVC and the novel costabiliser N‐phenyl‐3‐acetylpyrrolidin‐2,4‐dione (P24D). The model compound chosen was 4‐chloro‐2‐hexene (4C2H), which simulates the in‐chain allylic chlorine impurities present in PVC and are considered the most labile defects present in the polymer. Results suggested that stabilisation involves concerted reactions involving metal complexes rather than a series of stepwise reactions. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2731–2743, 2004
Engineering properties of Novolac resin‐PMMA{poly(methyl methacrylate)} IPN system
Authors: Goswami S. , Chakrabarty D. 
Published: July 2004

AbstractFull and semi interpenetrating polymer networks (IPNs) based on phenol‐formaldehyde resin (Novolac) and poly(methyl methacrylate) have been made by in situ sequential technique of IPN formation. These systems of different compositions were characterized with respect to their mechanical properties, such as, ultimate tensile strength (UTS), percentage elongation at break, modulus, and toughness. Thermal properties were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Extent of phase mixing of the two polymers was envisaged from the micrographs obtained by polarizing light microscopy (PLM). The effects of variation of the blend ratios on the above‐mentioned properties were examined. There was a decreasing trend of modulus and UTS with consequent increases in elongation at break and toughness for both types of IPNs with increase in proportions of PMMA. Lowering of glass transition temperatures (with respect to pure crosslinked Novolac resin) of the IPNs with increasing proportions of PMMA was observed, indicating a plasticizing influence of PMMA on the rigid and brittle matrix of phenolic resin. The TGA thermograms exhibit lowering in thermal stability of the IPNs with respect to pure phenolic resin in the regions of higher temperatures. With increase in proportion of PMMA the onset of degradation of the IPNs is shifted towards lower temperature zone. The surface morphology as revealed by PLM indicates distribution of discrete domains of PMMA in the phenolic resin matrix. The two phase interfaces are quite sharp at higher concentrations of PMMA. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2764–2774, 2004
Hydraulic resistance of rigid polyurethane foams. II. Effect of variation of surfactant, water, and nucleating agent concentrations on foam structure and properties
Authors: Mondal Pravakar , Khakhar D. V. 
Published: July 2004

AbstractHydraulic resistance of rigid polyurethane foams to penetration by water at high pressures is studied in this work in the context of buoyancy applications. Micron sized silica particles are used as nucleating agents. The effect of the variation of the concentrations of the surfactant, water, and nucleating agent on cell structure, closed cell content, and compressive modulus, is examined. Foams have densities in the range of 145 to 165 kg/m3. At a particular water concentration, with increase in the concentration of the surfactant, the window area of the cells becomes smaller and the hydraulic resistance of the foam increases. A cell window is the lamella of the foam material that separates two adjacent cells. With increase in the concentration of water keeping surfactant concentration constant, the average window area remains almost the same but the cell window area distribution becomes wider and the hydraulic resistance of the foams decreases. Foams made with silica have smaller cell windows but lower hydraulic resistance than that of the foams made without silica. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2830–2837, 2004
Synthesis and characterization of konjac glucomannan/poly(vinyl alcohol) interpenetrating polymer networks
Authors: Li Bin , Xie Bijun 
Published: July 2004

AbstractNovel interpenetrating polymer networks (IPNs) coded as KP were synthesized successfully from poly(vinyl alcohol) (PVA) and konjac glucomannan (KGM) in the presence of glutaraldehyde as a crosslink agent. The transparent IPN films that were 40 μm thick were prepared by means of conventional solvent‐casting technique and dried at room temperature for 2 days. The structure and miscibility of the KP films were studied by Fourier transformed infrared spectra, scanning electron microscopy, differential scanning calorimetry, wide‐angle X‐ray diffraction, and ultraviolet visible spectroscopy (UV–Vis). The results indicated that strong intermolecular interaction caused by crosslink bonding between PVA and KGM occurred in the IPN films, resulting in wonderful miscibility when the reaction time is 4 h. The tensile strength, elongation at break, and moisture uptake was much higher than that of the pure PVA film, KGM film, and uncrosslinked blend films. In other words, the structure of IPN endowed the films with excellent performance, so the new material has promising applications to food package film and agricultural film because of its biodegradability. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2775–2780, 2004
A new secondary accelerator for the sulfur vulcanization of natural rubber latex and its effect on the rheological properties
Authors: Kurien Mary , Claramma N. M. , Kuriakose A. P. 
Published: July 2004

AbstractThe vulcanization of natural rubber (NR) latex can be effectively carried out at low temperatures by using binary accelerator systems containing thiourea (TU) as a secondary accelerator. It was reported that sulfur‐containing nucleophiles such as thiourea enable the primary accelerator to become effective even at low temperatures, indicating a nucleophilic reaction mechanism in such vulcanization reactions. In the present study, a derivative of thiourea [viz. aminoiminomethyl thiourea (AMT)], which is more nucleophilic than thiourea, is used as a secondary accelerator in the sulfur vulcanization of NR latex. One of the aims of this study was to give conclusive evidence for a nucleophilic reaction mechanism. The synergistic effect of the above thiourea derivative with primary accelerators such as tetramethylthiuram disulfide (TMTD), zinc diethyldithiocarbamate (ZDC), and cyclohexylbenzthiazyl sulfenamide (CBS) was studied at two different temperatures (viz. 100 and 120°C). These binary systems were found to be very effective in reducing the optimum cure time of the different mixes compared to control formulations containing TU. The optimum amount of the secondary accelerator required was also determined. Mechanical properties such as tensile strength and tear strength of the vulcanizates were also evaluated. Chemical characterization of the vulcanizates was carried out by determining the total crosslink density. Values of the cure characteristics evaluated support a nucleophilic reaction mechanism in these vulcanization reactions under review. The effect of this secondary accelerator on the rheological behavior of compounded latex is also studied and was found not to affect adversely. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2781–2789, 2004
Maleic acid grafting on low density polyethylene
Authors: Singh S. K. , Tambe S. P. , Samui A. B. , Kumar Dhirendra 
Published: July 2004

AbstractGrafting of maleic acid (MAc) on low density polyethylene (LDPE) was carried out using γ‐irradiation technique. Preactivation method was used for grafting and a maximum grafting of 2.4% was obtained. Grafted polymer(LDPE‐g‐MAc) was characterized by chemical method, Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), Thermo‐Gravimetric Analysis (TGA), Melt Flow Index (MFI), Tensile Property Measurement, Particle Size Analysis, and Hot Stage Optical Microscopy. Presence of carbonyl peak of high intensity, high acid value, and low melt flow index value confirmed grafting of MAc on LDPE. A marginal change in thermal and mechanical properties of LDPE was observed after grafting. Change in crystallization behavior of LDPE has been noticed after grafting. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2802–2807, 2004
New tetrafunctional epoxy resin system with increased shelf life
Authors: Jagadeesh K. S. , Shashikiran K. 
Published: July 2004

AbstractChlorine‐ and methyl‐substituted aromatic diamines based on diaminodiphenylmethane were epoxidized and characterized. The effect of different substituents on epoxidation was studied. The cure studies of the two new tetrafunctional resins in comparison with unsubstituted resin N,N,N′,N′‐tetraglycidyl‐4,4′‐diaminodiphenylmethane (TGDDM) was carried out by DSC with 3,3′‐dichloro‐4,4′diaminodiphenylmethane (o‐DCDDM; 30% w/w) as a common curing agent. The mechanical properties such as flexural, Izod impact, heat distortion temperature (HDT), of such cured neat resins were also studied. The results of the cure studies indicate that the substitution of the α‐hydrogen of the resin by chlorine or methyl group decreases the reactivity of the resin leading to an increase in the shelf life. This study also indicates that the functionality of the resin plays a pivotal role in the reactivity and thus the shelf life of an epoxy resin system. The results of the mechanical properties of the neat resin casts obtained by subjecting to a common cure schedule when compared with the unsubstituted resin showed a decrease in impact strength, which is obvious because of the presence of a bulky pendant group but the impact strength was higher than that of the TGOS30 resin system. Results of flexural strength of the different substituted neat resin casts did not show much of a deviation from that of the unsubstituted resin system. The HDT results indicate no significant difference in the values of the unsubstituted resin vis‐a‐vis with substituted resin systems. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2790–2801, 2004
A simple sulfuric acid pretreatment method to improve the adsorption of Cr(VI) by chitosan
Authors: Lasko C. L. , Adams K. H. , DeBenedet E. M. , West P. A. 
Published: July 2004

AbstractAn optimum pH of 5.0 for the adsorption of Cr6+ by chitosan was determined by using a stirred‐batch reactor method at constant pH. When a column containing chitosan was used to bind Cr6+ in a situation where pH could not be held constant because of pH changes caused by the chitosan itself, significant binding occurred only at solution pH 1 and 2. When chitosan was pretreated with sulfuric acid in a range of 7–70 mol % sulfuric acid : moles glucosamine residue, maximum binding occurred at pH 6.0. Under these conditions, a column containing 0.500 g acid‐treated chitosan (35% mole ratio) reduced the concentration of Cr6+ in 713 bed volumes of 25 ppm Cr6+ solution to ≤5 ppm in the effluent. A similar column of pretreated chitosan reduced Cr6+ concentration in 1042 bed volumes of industrial chromium plating rinse water initially containing 18 ppm Cr6+ to ≤5 ppm. Capacity experiment results indicated 60 mg chromium bound per gram of treated chitosan at pH 6.0. Commercial resin IRA‐67 was also investigated as a Cr6+ binding agent. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2808–2814, 2004