bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hot melt adhesives: An outline scheme for the separation and identification of their components
Authors: Finch C. A. , Kidman D. H. 
Published: March 2007

AbstractMethods are described for identifying polyamides, polyurethanes, ethylene–vinyl acetate resins, polyesters, rosins and their esters, polyisobutenes and paraffin waxes in “hot‐melt” adhesives, by a combination of chemical tests and infrared spectrophotometry. Mixtures are separated quantitatively into their components by selective solvent extraction before testing.
An extension of polymer crystallisation kinetics to a branching mechanism for spherulitic growth
Authors: Booth A. , Hay J. N. 
Published: March 2007

AbstractThe initial stages in the development of spherulites from primary nuclei to spherical arrays of branching fibrils are included in the kinetics of polymer crystallisation. Since most of the experimental isotherms exhibit the required time dependence only over a limited range it is considered that the model has little use, and these initial stages in the development of spherulites have little effect on the degree of fit of the experimental isotherms to the Avrami rate equation.The general time dependences of crystallisations developing as a branching process is outlined and compared with that of the Avrami equations for growth of spherical particles.
Nitrogen‐containing products from the thermal decomposition of flexible polyurethane foams
Authors: Woolley W. D. 
Published: March 2007

AbstractThe thermal decomposition of a polyester and a polyether flexible foam in a nitrogen atmosphere has been studied by gas chromatography, mass spec‐trometry and elemental ultramicroanalysis. It is shown that the decomposition behaviours of the two foams are similar. At low temperatures (200 to 300 °C) there is a rapid and complete loss of the tolylene diisocyanate unit of each foam as a volatile yellow smoke leaving a polyol residue. The smoke has been isolated as a yellow solid (common to both foams) which contains virtually all of the nitrogen of the original foams and, under the conditions of test, is stable at temperatures up to 750 °C. Nitrogen‐containing products of low molecular weight (mainly hydrogen cyanide, acetonitrile, acrylonitrile, pyridine and benzonitrile) observed during the high temperature decomposition (over 800 °C) of the foams are shown to be derived from the yellow smokes. At 1000 °C, approximately 70% of the available nitrogen has been recovered as hydrogen cyanide.
The effectiveness of ultraviolet absorbers in PVC
Authors: Martin K. G. 
Published: March 2007

AbstractThe influence of some benzophenone‐type ultraviolet absorbers in a general PVC formulation has been studied by determining rates of photo‐oxidation when specimens were exposed to xenon‐arc irradiation under controlled conditions. Replicates of the formulation but without the absorbers were similarly photo‐oxidised behind a series of glass filters to provide a basis for assessing the effectiveness of the absorbers. Some changes in appearance of the specimens have also been measured and discussed in relation to the data on photo‐oxidation rate.
Sequence length and crystallinity in alpha‐olefin terpolymers
Authors: Davison S. , Taylor G. L. 
Published: March 2007

AbstractThe minimum sequence length for crystallisation in a polymer was determined by a novel kinetic approach using sequence analysis of a series of blocky terpolymers.Copolymers and terpolymers of ethylene, propylene, and but‐l‐ene were prepared with a Ziegler–Natta catalyst system. Compositions of feeds and polymers were analysed, and kinetic reactivity parameters were calculated using both the Fineman–Ross and Alfrey–Goldfinger approaches. The parameters were then applied to determine the sequence length distribution of each component in the terpolymers. Also, deliberate control of sequence lengths enabled synthesis of heptane‐soluble, rubbery polymers even using a catalyst system which normally produced blocky materials.Crystalline contents of the terpolymers were determined experimentally by nitric acid digestion. A critical comparison of the measured crystallinities with the calculated sequence length distributions was thereby made possible. From this comparison a minimum sequence length of monomer below which crystallisation did not occur was estimated; this length was approximately 20 backbone carbon atoms.
Calibration procedures in gel permeation chromatography
Authors: Dawkins J. V. 
Published: March 2007

AbstractProcedures for the determination of the log molecular weight vs. elution volume calibration relation are reviewed for linear homopolymers. The calibration curve is readily established with narrow molecular weight distribution fractions. For broad molecular weight distribution fractions the peak molecular weight at the peak elution volume of a fraction's gel permeation chromatogram has to be calculated from average molecular weights. When well‐characterised fractions of the polymer requiring analysis are unavailable, a calibration curve can be established by procedures which assume that the hydrodynamic volume of a polymer molecule in solution controls fractionation in gel permeation chromatography. These universal calibration procedures require information on Mark‐Houwink viscosity constants or polymer unperturbed dimensions. The validity of hydrodynamic volume as the universal calibration parameter is discussed with special reference to the goodness of the solvent for a polymer and polymer polarity. Examples are given of the various calibration procedures which are employed in the determination of molecular weight distribution and average molecular weights for poly(methylmethacrylate), polyethylene and polyisoprene.
Reaction of disulphides with cyclic phosphoramidites
Authors: Jarvie A. W. P. , Moore C. G. , Skelton D. 
Published: March 2007

AbstractIt has been observed that cyclic phosphoramidites react more slowly than triphenylphosphine with diallyldisulphide and do not give a quantitative yield of monosulphide. Therefore, contrary to expectation, these reagents are unsuitable for use as chemical probes for determining the structure of sulphurvulcanised rubber. It appears that, like triphenylphosphine, the cyclic phosphoramidites react with allylic disulphides by a SNi' mechanism.
The effect of boiling water on an amorphous aromatic polyamide
Authors: Buckley A. , Curnuck P. A. , Jones M. E. B. , Thomas I. 
Published: March 2007

AbstractAmorphous poly(sulphonyldi‐p‐phenylene‐α,ω‐alkylene dicarboxamides) undergo marked changes during immersion in boiling water. This treatment produces opacity, softening and ultimately blistering and embrittlement of moulded or cast specimens produced from these polyamides. These changes have been shown to be due to a lowering of the glass‐transition temperature (Tg) to below 100 °C, and to the acid catalysed, hydrolytic scission of in‐chain amide bonds. The stability to boiling water is improved by copolymerisation to raise the Tg and by minimising the total acid content of the polymers. An n.m.r. method for the determination of terminal amine groups in these polyamides is described.
Parameters affecting the performance of polyelectrolytes as aids to water clarification
Authors: Wilde P. F. , Dexter R. W. 
Published: March 2007

AbstractAn investigation of the flocculation of silica and alumina suspensions by a series of synthetic flocculants of a wide range of charge density both anionic and cationic in nature has been carried out. The extent of flocculation was determined by measurements of settling rate, sediment volume and supernatant clarity. The effect of the pH of the suspension on the performance of a number of selected polymers has been investigated. In the systems examined, flocculation was largely controlled by the charge carried by the suspended particles and polymer molecules.The dosage/settling rate characteristics of kaolin suspensions flocculated with non‐ionic polymers of varying molecular weight are reported.The dosages of non‐ionic polymers required for optimum flocculation of kaolin suspensions of varying solids content have been measured. At low particle concentrations bridging is less effective, and is probably reduced due to the adsorption of polymer molecules on to single particles.
Siloxane modification of polyamides
Authors: Owen M. J. , Thompson J. 
Published: March 2007

AbstractPolyamide–polydimethylsiloxane block copolymers were made by the BuLi or LiOSi(CH3)2OSi(CH3)2OLi catalysed polymerisation of hexamethylcyclotrisiloxane terminated by and using this substituted siloxane to initiate the polymerisation of lauryllactam or caprolactam in toluene solvent in the presence of lithium aluminium hydride as the catalyst.One or 2% of the polycaprolactam‐polydimethylsiloxane block copolymers were mixed with nylon 6 and discs moulded. The presence of silicone in the surface was demonstrated by determining the critical surface tensions of wetting using ethanol–water mixtures as the contact‐angle test liquids. A polylauryllactam–polydimethylsiloxane block copolymer compatible with polyethylene was similarly studied.An important application for such composites is to provide a dry lubricated surface, therefore the kinetic coefficients of friction of steel against these copolymer‐treated nylon 6 samples were determined demonstrating at best a reduction to one third that of the untreated control.
The laboratory evaluation of polyelectrolyte flocculants
Authors: Packham R. F. 
Published: March 2007

AbstractThe application of polyelectrolyte flocculants as primary coagulants, coagulant aids and sludge conditioners in the treatment of water for public supply is discussed. Laboratory techniques that have been used to evaluate commercial polyelectrolytes for these uses are described and exemplified with results. The difficulty of defining floc characteristics is emphasised.
Flammability of polymers. v. thermal volatilisation analysis of polyester resin compositions
Authors: Learmonth G. S. , Nesbit A. 
Published: March 2007

AbstractThermovolatilisation analysis has been used as part of an investigation of the flammability of an insaturated polyester resin. It was clearly possible to distinguish two reaction stages which were attributed to breakdown of the styrene and polyester chains respectively and in neither case did flame retardants affect the reaction very much.
trans‐polypentenamer: A general purpose rubber from a novel reaction
Authors: Amass A. J. 
Published: March 2007

AbstractThe nature of the catalysts for the ring‐opening polymerisation of cycloolefins is reviewed with particular reference to the production of trans‐polypentenamer. The roles of the components of the catalyst systems are discussed and a mechanism for the ring‐opening polymerisation of cycloolefins is proposed.
Synthesis and polymerisation of polycyclic compounds with strained C—C single bonds
Authors: Hall H. K. 
Published: March 2007

AbstractRing opening polymerisation of bicyclobutanes possessing electronegative substituents (CN, COOCH3, etc.) at one or both bridgeheads can be accomplished readily with either radical or anionic initiators. The polymer chains consist exclusively of cyclobutane rings linked through the 1,3 positions. Readily obtained in high molecular weight, they possess attractive physical properties for the formation of fibres and films. These new monomers copolymerise readily with vinyl compounds, exhibiting reactivities comparable to the latter, and provide a wide variety of new copolymers. Other bicyclic compounds containing strained C—C bonds whose polymerisation has been demonstrated include bicyclo‐[2.1.0]‐pentane‐1‐carbonitrile, 1‐methyl‐2,3‐benzocyclopropenecarbonitrile, and 1,3‐dehydroadamantane. The ability to polymerise requires a high strain energy, but a high degree of p character in the C—C single bond as well.
Kinetic investigation of the synthesis of a polyethersulphone
Authors: Attwood T. E. , Newton A. B. , Rose J. B. 
Published: March 2007

AbstractThis paper summarises results obtained from a kinetic investigation of the processes occuring during the synthesis of polyethersulphones by reactions such as:magnified imageThe factors determining the variations in functional group reactivities due to ‘bridge’ effects are described with reference to the reactivities of these groups in model systems, and the detailed kinetics shown by the polycondensations are explained. Evidence is presented to show that ether interchange can occur in a manner analogous to ester interchange in a polyesterification, and that in polycondensations where potassium fluoride (as opposed to the chloride or bromide) is eliminated chain extension is reversible and the use of high reactant concentrations is required to obtain polymers of high molecular weight.
A branching model for crystallisation kinetics
Authors: Iguchi M. 
Published: March 2007

AbstractIn order to test whether the branching probability of crystallites plays an important role in determining the structure and the mutual interaction of growing bodies in bulk crystallisation system, mathematical model experiments for dendrite growth on a hexagonal lattice were performed. It was shown that, when the branching frequency is high enough, a definite contour was developed for each growing body from different primary nuclei, giving rise to a sharp boundary. As the branching frequency decreased, however, the boundary became blurred as the result of the interaction of growing units from different origins, suggesting the inadequacy of the Avrami‐type kinetic model, i.e. the expanding‐and‐over‐lapping sphere model. For the latter case, a calculation of kinetic equations was made (with simple assumptions) assuming a growth of one‐dimensional unit which branches in succession. Crystallisation curves similar to those derived from current theories were obtained without restriction in the constant (i.e. without integer constant). A basic question cast by Gordon on the Avrami‐expression of one‐dimensional crystal growth was discussed briefly.
Application of polymer physics to practical problems associated with polyurethane solings
Authors: Whittaker R. E. 
Published: March 2007

AbstractThe cut growth and fatigue properties of a typical cellular polyurethane soling material are considered in terms of the tearing energy theory established for vulcanised solid rubbers. The minimum value of tearing energy (T0) below which no cut growth occurs in the absence of chemical effects is compared with practical results from shoe soles in wear.The existence of large holes in a soling material which can contribute to flex cracking failure is considered and a recent theory for their existence in solid rubbers is discussed. The scanning electron microscope has been used to illusstrate poor water absorption properties of low density polyurethane soling materials.
The characterisation of polyolefins using a curie‐point pyrolyser and gas chromatography
Authors: Northmore B. R. 
Published: March 2007

AbstractThe products of controlled thermal degradation of polyolefins have been examined by gas chromatography. The factors determining the formation of decomposition products in the Curie‐point pyrolyser have been studied and a highly reproducible distribution of products has been obtained at a pyrolysis temperature of 595 °C. The probable degradation mechanisms are discussed and a diagnostic scheme has been derived for determining from the degradation products the nature of the branches and thus identifying the comonomer in an ethylene copolymer.
A study of branching in ethylene copolymers by X‐ray diffraction
Authors: Preedy John E. 
Published: March 2007

AbstractBy slow cooling and annealing polyethylene a semiequilibrium crystallisation state is obtained. Under such crystallisation conditions changes in unit cell dimensions and crystallinities, as measured by X‐ray diffraction, may be related to the size and number of branch groups in polyethylene copolymers. Thus methyl and ethyl groups may be accommodated within the crystalline lattice whereas butyl groups are not. The method may be used to determine the type and extent of branching in unknown ethylene copolymers.
A study of sequence distribution in an aromatic copolyamide
Authors: Curnuck Peter A. , Jones Michael E. B. 
Published: March 2007

AbstractAddition of lithium chloride to solutions of a copolyamide prepared from di(p‐aminophenyl) ether, di(p‐aminophenyl) sulphone and isophthaloyl chloride enables the sequence distribution of the co‐units in the copolymer to be determined by nuclear magnetic resonance spectroscopy. Copolymers of controlled sequence distribution can be prepared by correct selection of polymerisation solvent, acid acceptor and the mixing sequence of the polymer forming reactants.
Mechanism and side reactions of the anionic condensation of styrene with alkyl halides
Authors: Iguchi Masatoshi , Ranson Richard J. , Gordon Manfred 
Published: March 2007

AbstractThe reactions occurring in the system styrene + butyl bromide + lithium in tetrahydrofuran are studied as a model for olefine/dihalide reactions pioneered by Richards and co‐workers for the purpose of synthesising highly regular copolymers. Computer fittings of a kinetic scheme and of gel permeation chromatographs of the products leads to the conclusion that homopolymerisation of styrene tends to be a serious side reaction to the desired condensation between the styrene dianion and two moles of butyl bromide. As expected from previous work, this is found to be much less serious in the analogous system with alpha methyl styrene in place of styrene.
The use of gel permeation chromatography to study the condensation of resorcinol with formaldehyde
Authors: Hope Paul , Anderson Roger , Bloss Alan S. 
Published: March 2007

AbstractGel permeation chromatography has been used to study the acid‐catalysed condensation of resorcinol with formaldehyde in concentrated solution. Rate curves for the consumption of resorcinol and the formation of some of the oligomeric products, and changes in molecular weight distribution during the reaction have been compared for condensates prepared using various reaction conditions.
Experience with PV‐diesel hybrid village power systems in Southern Morocco
Authors: Muñoz J. , Narvarte L. , Lorenzo E. 
Published: March 2007

AbstractIn October 2002, under the auspices of Spanish Cooperation, a pilot electrification project put into operation two centralised PV‐diesel hybrid systems in two different Moroccan villages. These systems currently provide a full‐time energy service and supply electricity to more than a hundred of families, six community buildings, street lighting and one running water system. The appearance of the electricity service is very similar to an urban one: one phase AC supply (230 V/50 Hz) distributed up to each dwelling using a low‐voltage mini‐grid, which has been designed to be fully compatible with a future arrival of the utility grid. The management of this electricity service is based on a ‘fee‐for‐service’ scheme agreed between a local NGO, partner of the project, and electricity associations created in each village, which are in charge of, among other tasks, recording the daily energy production of systems and the monthly energy consumption of each house. This register of data allows a systematic evaluation of both the system performance and the energy consumption of users. Now, after 4 years of operation, this paper presents the experience of this pilot electrification project and draws lessons that can be useful for designing, managing and sizing this type of small village PV‐hybrid system. Copyright © 2007 John Wiley & Sons, Ltd.
Multi‐crystalline Si solar cells with very fast deposited (180 nm/min) passivating hot‐wire CVD silicon nitride as antireflection coating
Authors: Verlaan V. , van der Werf C. H. M. , Houweling Z. S. , Romijn I. G. , Weeber A. W. , Dekkers H. F. W. , Goldbach H. D. , Schropp R. E. I. 
Published: March 2007

AbstractHot‐wire chemical vapor deposition (HWCVD) is a promising technique for very fast deposition of high quality thin films. We developed processing conditions for device‐ quality silicon nitride (a‐SiNx:H) anti‐reflection coating (ARC) at high deposition rates of 3 nm/s. The HWCVD SiNx layers were deposited on multicrystalline silicon (mc‐Si) solar cells provided by IMEC and ECN Solar Energy. Reference cells were provided with optimized parallel plate PECVD SiNx and microwave PECVD SiNx respectively. The application of HWCVD SiNx on IMEC mc‐Si solar cells led to effective passivation, evidenced by a Voc of 606 mV and consistent IQE curves. For further optimization, series were made with HW SiNx (with different x) on mc‐Si solar cells from ECN Solar Energy. The best cell efficiencies were obtained for samples with a N/Si ratio of 1·2 and a high mass density of >2·9 g/cm3. The best solar cells reached an efficiency of 15·7%, which is similar to the best reference cell, made from neighboring wafers, with microwave PECVD SiNx. The IQE measurements and high Voc values for these cells with HW SiNx demonstrate good bulk passivation. PC1D simulations confirm the excellent bulk‐ and surface‐passivation for HW SiNx coatings. Interesting is the significantly higher blue response for the cells with HWCVD SiNx when compared to the PECVD SiNx reference cells. This difference in blue response is caused by lower light absorption of the HWCVD layers (compared to microwave CVD; ECN) and better surface passivation (compared to parallel plate PECVD; IMEC). The application of HW SiNx as a passivating antireflection layer on mc‐Si solar cells leads to efficiencies comparable to those with optimized PECVD SiNx coatings, although HWCVD is performed at a much higher deposition rate. Copyright © 2007 John Wiley & Sons, Ltd.
Identification of carbonylated proteins from enriched rat skeletal muscle mitochondria using affinity chromatography‐stable isotope labeling and tandem mass spectrometry
Authors: Meany Danni L. , Xie Hongwei , Thompson LaDora V. , Arriaga Edgar A. , Griffin Timothy J. 
Published: March 2007

AbstractWe describe a strategy for the identification of carbonylated proteins from complex protein mixtures that combines biotin hydrazide labeling of protein carbonyl groups, avidin affinity chromatography, multiplexed iTRAQ reagent stable isotope labeling, and analysis using pulsed Q dissociation (PQD) operation on an LTQ linear ion trap mass spectrometer. This strategy provided the ability to distinguish biotin hydrazide labeled, avidin purified, carbonylated proteins from non‐carbonylated background proteins with affinity for the avidin column, derived from a control sample. Applying this strategy to the identification of crudely enriched rat skeletal muscle mitochondrial protein isolates, we generated a catalogue of over 200 carbonylated proteins by virtue of their quantitative enrichment compared to the control sample. The catalogue contains many mitochondrial localized proteins shown to be susceptible to carbonyl modification for the first time, including numerous transmembrane proteins involved in oxidative phosphorylation. Other oxidative modifications (e.g. nitrosylation, hydroxylation) were also identified on many of the carbonylated proteins, providing further evidence of the susceptibility of these proteins to oxidative damage. The results also demonstrate the utility of PQD operation on the LTQ instrument for quantitative analysis of iTRAQ reagent‐labeled peptide mixtures, as well as the quantitative reproducibility of the avidin‐affinity enrichment method.