bluuebunny/crossref_metadata_2025 huggingface dataset:
Stereochemical effects in the electron impact mass spectra of some 2,6‐dideoxy‐3‐c‐methylhexopyranoses
Authors: Gioia B. , Vigevani A.
Published: May 2005

The electron impact mass spectra of the methyl α‐and β‐glycosides of axenose, of a number of derivatives, and of mycarose, display substantial differences, characteristic of their stereochemistry. In order to interpret this behaviour the structures of the fragments and the main features of the fragmentation patterns have been established, and the methyl glycosides of some related monosaccharides (arcanose, cladinose and idose) have been examined. The experimental results allow the observed differences to be attributed to the presence of an intramolecular hydrogen bond between the hydroxyl group at C‐3 and the oxygen atom of the methoxy group in the methyl α‐glycosides of axenose and mycarose.
Applications of artificial intelligence for chemical inference. XIX—Computer generation of ion structures
Authors: Smith Dennis H. , Konopelski Joseph P. , Djerassi Carl
Published: May 2005

The purpose of this paper is to discuss an interactive computer program which can be used to study questions of plausible ion structures. The program can be constrained in a variety of ways by the user, based on information inferred from (i) the structure of the intact molecule which gave rise to the ion, (ii) metastable defocusing experiments to identify progenitors, and (iii) existing knowledge of the fragmentations and rearrangements of related molecules, including deuterium labeled analogs. Implementation of these constraints is discussed primarily with the example of triethylamine, an apparently simple compound whose behavior is examined in detail with the aid of the program because of the complexity of its fragmentation.
Deconvolution of composite metastable peaks: A new method for the determination of metastable transitions occurring in the first field free region
Authors: Evers E. A. I. M. , Noest A. J. , Akkerman O. S.
Published: May 2005

The masses of daughter ions resulting from metastable transitions in the first field free region of a “reversed geometry” mass spectrometer can be accurately determined through a mass analysed ion kinetic energy scan at the apparent mass at which these daughter ions travel through the magnetic sector. A combination of these mass analysed ion kinetic scans with scanning the magnetic flux allows the resolution of overlapping metastable diffuse peaks.
Conjugated Schiff bases. VII—Decarbonylation of some 1,3‐hetrodienes under electron impact
Authors: Moskal Janusz , Nagraba Krzysztof , Pálonek Elzbieta
Published: May 2005

The mass spectra of some 1,3‐ heterodienes containing the 1‐oxa‐4‐aza‐butadiene system have been determined and the characteristic fragmentation pathways are discussed. The pathways suggested are supported by the appropriate metastables, the spectra of model compounds and by deuterium labelling. The 1, 3‐heterodienes substituted by the thioarylamide group from ions involving participation of the sulphur atom.
Determination of daughter ion elemental compositions in charge separation reactions
Authors: Vijfhuizen Peter C. , Van Der Schee Henk , Terlouw Johan K.
Published: May 2005

It is shown that the elemental composition of a product ion generated from a multiply charged ion in a charge separation reaction can be determined with a double focusing instrument under conditions of high mass and energy resolution. Results for a number of charge separation reactions in benzylamine are briefly discussed.
The mass spectra of halogenated β‐sultones and a comparative study with vinyl methanesulfonates
Authors: Kao Liu Lilian
Published: May 2005

The mass spectra of some halogenated β‐sultones which have been determined show some common features. These include the absence of molecular or ions and the presence of abundant trihalomethyl and [M‐ trihalomethyl]+ ions. The latter can subsequently lose sulfur dioxide, ions are also observed in high abundance.
Notiz zur elektronenstoßinduzierten Ringkontraktion von Cycloalkanonen und zur Struktur der ‐Ionen
Authors: Schwarz Helmut
Published: May 2005

Durch CA‐Untersuchung wird nachgewiesen, daß Cyclooktanon‐Ionen vor der Äthylen‐Eliminierung nicht zu ionisiertem 2‐Äthylcyclohexanon isomerisieren. Außerdem wird gezeigt, daß die durch einfache und doppelte McLafferty‐Umlagerung aus einigen Cycloalkanonen erzeugten Ionen m/e 98 je nach Konstitution der Vorläufer in verschiedenen Strukturen existieren können.
Mass spectrometry of the triethylsilyl, tri‐n‐propylsilyl and tri‐n‐butylsilyl derivatives of some alcohols, steroids and cannabinoids
Authors: Harvey D. J.
Published: May 2005

The 25 eV mass spectra of the trialkylsilyl (R = Et, Pr, Bu) derivatives of several alcohols, steroids and cannabinoids are compared with those of the corresponding trimethylsilyl (TMS) derivatives. Abundant ions produced by elimination of one of the alkyl groups characterize most of the spectra. Although the presence of such ions is advantageous in certain cases, such as for single ion monitoring studies, the spectra usually contain fewer ions of diagnostic use than the spectra of corresponding TMS derivatives. Successive elimination of CnH2n fragments is also a feature of these spectra.
Studies in mass spectrometry. IV—Fragmentation of aryltriflates. Substituent effects on [ArO]+ ion abundances: Looking for a best suited electron energy in the steady state approach. Experimental evidence for the ‘through bond’ stabilization of aryl cations by meta electron donor Substituents
Authors: Derocque Jean‐Luc , Jochem Martin
Published: May 2005

The fragmentation patterns of 24 substituted phenyltrifluoromethanesulfonates has been determined by exact mass and metastable transition measurements. The influence of the ring substituent(s) on the abundance of the [ArO]+ ions has been investigated at low energies and a new standard parameter for plotting against Hammett's ó constants is proposed. The direct loss of CF3SO3 from the molecular ion of 3,5‐(diisopropyl)‐phenyl‐, 3,5‐(dicyclopropyl)phenyl‐ and 3,5‐di(α‐methylcyclopropyl)‐phenyl‐methanesulfonate, and further observations on the fragmentation processes of these compounds are consistent with M.O. calculations on the ‘through bond’ stabilization of the [Ar]+ σ state by meta electron donor substituents.
Spectrométrie de Masse de Benzylidène—Acétals d'Hexopyranosides
Authors: Bosso Claude , Defaye Jacques , Gadelle Andrée , Ulrich Jacques
Published: May 2005

La fragmentation en impact électronique est rapportée pour 46 benzylidéne‐acétals d'hexopyranosides, appartenant aux séries allo, altro, galacto, gluco, gulo et manno ainsi que pour quelques produits de leur oxydation partielle. Indépendamment de l'ion moléculaire toujours présent et fréquemment partie d'un triplet magnified image ainsi que la rupture bien connu C‐1C‐2, C‐4C‐5 et (Ph)CHO(C‐4), on retrouvé généralement deux types de ruptures complémentaires (C‐1C‐2, C‐3C‐4; C‐1O‐5, C‐2C‐3, dont l'intensité varie selon la substitution ou selon la fonctionnalisation de la molécule. Ces fragmentations permettent dans la majorité des cas l'assignation des substitutions sur des systémes du type 1,3,6‐trioxa‐bicyclo[4.4.0]décane. Les limitations de cette méthode sont discutées.
Spectrométrie de Masse d'Hétérocycles. VIII—Edude de Dérivés du Dioxasilolanne‐1,3,2
Authors: Lageot C. , Guillemonat A.
Published: May 2005

L'étude de spectres de masse de dioxasilolannes‐1,3,2 montre que la présence de deux atomes d'oxygène simplifie notablement le nombre de fragmentations du cycle. Les principaux mécanismes conduisent à la formation d'ion ‘silylénoïdes’ à des ruptures en α et β du silicium ainsi qu'à des migrations d'hydrogène.
Electron impact induced alkyl‐group fragmentation on the acridine nucleus
Authors: Acheson R. M. , Aplin R. T. , Bolton R. G.
Published: May 2005

The fragmentation of simple alkyl acridines closely resembles that of the analogous quinoline derivatives. Interaction between the heteroatom and a 4‐alkyl substituent dramatically influences the fragmentation pattern with resultant γ‐cleavage or rearrangement to the heteroatom and corresponding elimination of an alkene fragment. The fragmentation of the 9‐chloroalkylacridines closely resembles that of the acridines with the loss of the clorine atom superposed on the alkylacridine fragmentation. Redistribution of the centre of apparent charge localization occurs for the acridones with a tendency for interaction with the 9‐position.
Conformational effects in the chemical ionization spectra of derivatives of isomeric 2,3‐dimethyl‐1,4‐cyclopentanediols
Authors: Claeys M. , Van Haver D.
Published: May 2005

The chemical ionization mass spectra of the trimethylsilyl and methylboronate derivatives of some isomeric 2,3‐dimethyl‐1,4‐cyclopentanediols have been determinded using methane and isobutane as reagent gases. The degree of loss of TMSOH or CH3B(OH)2 appears to be strongly dependent upon the stereochemistry of the 2,3‐dimethyl‐1,4‐cyclopentanediol moiety and permits differentiation between the structural isomers. The results obtained from the chemical ionization (isobutane) spectra of the methylboronates are in excellent agreement with those derived from infrared data.
Chemical ionization mass spectrometry: A method of estimating reagent gas pressure in the ion source based on kinetic data
Authors: Hancock Richard A. , Walder Raymond , Weigel Helmut
Published: May 2005

Consequential upon determinations of kinetic rate constants of ion/molecule reactions in methane and isobutane, simple equations are presented from which the pressures of methane and isobutane in the ion source of chemical ionization mass spectrometers can be calculated. Account is taken of the design of the ion source and it is only necessary to determine two ion currents for each gas.
Elimination of 1,3‐Dioxolan‐2‐yliden from cyclic ethylene ketals
Authors: Budzikiewicz H. , Römer A.
Published: May 2005

The structural prerequisites for an elimination of :C(OCH2)2 from the molecular ions of ethylene ketals of cyclic ketones are discussed.
Charge distribution between formally identical fragments: The retro Diels‐Alder cleavage
Authors: Turecček F. , Hanuš V.
Published: May 2005

The electron impact induced retro Diels‐Alder cleavage of 4‐vinylcyclohexene, 1,4‐dimethyl‐4‐vinylcyclo‐hexene, limonene, dicyclopentadiene and dicyclohexadiene has been investigated using deuterium labelled analogues. With limonene, dicylopentadiene and dicyclohexadiene the charged diene fragments are produced with the same probability from both subunits of the molecular ion. With 4‐vinylcyclohexene and 1,4‐dimethyl‐4‐vinylcyclohexene, diene fragments containing the former vinyl group are charged preferentially. This small asymmetry of charge distribution was found to be independent of the ionizing energy. A new, qualitative rationalization is suggested to account for the unsymmetrical charge distribution in 4‐vinylcyclohexene and 1,4‐dimethyl‐4‐vinylcyclohexene. Metastable spectra and hydrogen scrambling are discussed.
Charge distribution between formally identical fragments: The McLafferty rearrangement
Authors: Tureček F. , Hanuš V.
Published: May 2005

The McLafferty rearrangement for 2,5‐diphenyl‐1‐hexene and its deuterium labelled analogues has been investigated. The α‐methylstyrene fragments originating from different parts of the molecular ion retain the charge with equal probability and afford identical metastable spectra. The geometry of the transition state is discussed.
Ion cyclotron resonance studies of alkylsilyl ions: V—The reactions of alcohols and ethers with the allyldimethylsilyl cation
Authors: Blair Ian A. , Trenerry V. Craige , Bowie John H.
Published: May 2005

Diallyldimethylsilane provides a source of the allyldimethylsilyl cation in the ion cyclotron resonance spectrometer; reaction of this cation with alcohols (ROH) produces adducts which decompose by loss of C3H6 to yield the ion \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm Me}_2 \mathop {\rm S}\limits^{\rm + } {\rm i} - {\rm OR}} \right] $\end{document}. This elimination is thought to occur by a 1,5‐hydrogen shift, together with either stepwise or concerted silicon‐carbon bond cleavage. The corresponding aducts from ethers ROR1 (R1⩾R, R1⩾Et) first lose (R1H˙) and then undergo the elimination described above.
Mass spectra of some platinum clusters. Electron impact and field desorption studies of Ptn(CO)m(PR3)p complexes
Authors: Würminghausen Th. , Reinecke H. J. , Braunstein Pierre
Published: May 2005

The compounds Pt3(CO)3[P(C6H5)3]4 molecular weight 1717, Pt4(CO)5[P(C6H5)3]4 molecular weight 1968 and Pt5(CO)6[P(C2H5)3]4 molecular weight 1615 are thermally labile and are slowly solvolysed by tetrahydrofuran and acetone. They cannot be analysed by means of electron impact. Field desorption, however, shows the molecular ion and [MxCO]+˙ peaks.
Molecular weight parity predicted from the parity values of mass spectral peaks
Authors: Mun In Ki , Venkataraghavan Rengachari , McLafferty Fred W.
Published: May 2005

The fact that an unknown mass spectrum originates from a compound of even (or odd) numbered molecular weight can be predicted for 43% (13%) of unknowns with 95% (80%) reliability.
High pressure mass spectrometry of some liquid chromatographic mass spectrometric reagents
Authors: Yinon Jehuda , Cohen Aviad
Published: May 2005

Pressure dependence of several reversed phase liquid chromatographic solvents, including methanol, acetonitrile and mixtures of methanol: water and acetonitrile: water has been investigated. Typical ions, [MH]+, [2M+H]+ and [3M+H]+, were recorded as function of source pressure and as a function of the amount of water in the mixture. Ion formation processes in methanol: water and acetonitrile: water are discussed. The influence of liquid chromatographic mass spectrometric solvent pressure on the mass spectra of samples has been demonstrated on an amino acid sample.
A 15N labelling, FD and FAB study of ammonia loss from protonated arginine molecules
Authors: Zwinselman J. J. , Nibbering N. M. M. , van der Greef J. , De Brauw M. C. Ten Noever
Published: May 2005

The positive ion field desorption (FD) spectrum of arginine taken at the best anode temperature only contains a peak due to [M+H]+ ions. At higher emitter temperatures a considerable amount of fragmentation is induced and the [M+HNH3]+ ions become most abundant. Specific 15N labelling reveals that the eliminated ammonia molecule, exclusively, contains one of the terminal nitrogen atoms of the guanidyl group. This also applies to the ammonia loss from metastably decomposing [M+H]+ ions. The positive ion fast atom bombardment (FAB) spectrum shows more fragmentation than the FD spectrum. In contrast with the FD results, the [M+H]+ ions generated upon FAB with ion lifetimes <10−6 s eliminate both ammonia containing one of the terminal nitrogen atoms of the guanidyl group and ammonia containing the α‐amino group in the ratio of 1.35, as found by 15N labelling. The metastably decomposing [M+H]+ ions, however, eliminate only the former ammonia molecule. In the negative ion FD and FAB spectra no other peak than that corresponding to the [MH]− ion is observed. Some attention has been paid to the thermal degradation of arginine on the basis of a few Curie‐point pyrolysis experiments.
The dynamical theory of energy partition. Loss of a hydrogen atom from the hydroxymethylene radical cation
Authors: Donchi Kevin F. , Derrick Peter J.
Published: May 2005

The translational energy releases accompanying fromation of H˙ and [CHO]+ from [CHOH]+˙, H˙ and [CDO]+ from [CDOH]+˙, D˙ and [CHO]+ from [CHOD]+˙ and D˙ and [CDO]+ from [CDOD]+˙ have been calculated from the widths at half‐height of the respective metastable peaks. The energy releases for [CHOD]+˙ and [CDOD]+˙ are similar to each other in magnitude, but are both significantly larger than those for [CHOH]+˙ and [CDOH]+˙. These differences are discussed in terms of the dynamical theory of energy partition. The larger energy releases for decompositions giving D˙ are attributed to larger proportions of the kinetic energy being associated with the departing D˙ in the transition states, as compared to H˙ in the transition states for the decompositions yielding H˙.
A mass spectrometry/mass spectrometry investigation of the nature of [C10H10]+˙, [C9H7]+ and [C10H8]+˙ gas phase ions
Authors: Dass Chhabil , Gross M. L.
Published: May 2005

Additional evidence for the rearrangement of the 1‐ and 3‐phenylcyclobutene radical cations, their corresponding ring‐opened 1,3‐butadiene ions and 1,2‐dihydronaphthalene radical cations to methylindenetype ions has been obtained for the decomposing ions by mass analysed ion kinetic energy spectroscopy (MIKES). The nature of the [C9H7]+ and [C10H8]+˙ daughter ions arising from the electron ionization induced fragmentation of these [C10H10]+˙ precursors has been investigated by collisionally activated dissociation (CAD), collisional ionization and ion kinetic energy spectroscopy. The [C9H7]+ produced from the various C10H10 hydrocarbons are of identical structure or an identical mixture of interconverting structures. These ions are similar in nature to the [C9H7]+ generated from indene by low energy electron ionization. The [C10H8]+˙ ions also possess a common structure, which is presumably that of the maphthalene radical cation.
Quantitative determination of compounds in mixtures by B2E=constant linked scans
Authors: Walther Hansjörg , Schlunegger Urs Peter , Friedli Felix
Published: May 2005

The B2E = constant linked scan is shown to be an excellent tool for quantifications with reversed geometry mass spectrometers. Deuterium‐labelled analogues may be used as internal standards, thus providing very simple clean‐up procedures. The principle is demonstrated with the example of chloro‐substituted benzoic acid methyl esters. Possible interferences arising from isotope peaks are discussed. The method is applied to the quantification of caffeine in beverages.
Formation of ketone ions upon the loss of CH2O from ionized esters
Authors: Lin Thomas , Hudson Charles E. , McAdoo David J.
Published: May 2005

Unimolecular and collision‐induced decompositions of the products of CH2O loss from propyl propanoate and butyl butanoate demostrate that the respective products are the 3‐pentanone and 4‐heptanone ions.
The dichotomy of methyl loss from 2‐methylalkane molecular ions
Authors: Wolkoff Peder , Holmes John L. , Lossing F. P.
Published: May 2005

The kinetic energy release for methyl loss from the molecular ion of 2‐methylpentane increases c. twofold over the time‐range 1–15 μs. This result from a mixture of secondary and tertiary pentyl cations. The appearance energy showed that at threshold (and long times) only tertiary ions are formed. The molecular ion of 2‐methylhexane produces tertiary hexyl ions by loss of methyl at threshold, but in the μs time‐frame only secondary hexyl ions appear to be formed, because the kinetic energy release is small and independent of the observation time.
Chemical ionization of ethylene dibromide with ammonia gas
Authors: Cairns Thomas , Siegmund Emil G.
Published: May 2005

Under ammonia chemical ionization conditions, a fragment ion of ethylene dibromide undergoes a nucleophilic substitution reaction which is demostrated to be highly pressure‐dependent upon the reagent gas concentration. This reaction is strongly influenced by the stability of the intermediate carbonium ion and the ability of the substituted product ion to be stabilized by intramolecular hydrogen bonding.
Solvent‐derived metal oxides in electrospray mass spectrometry of metal salt solutions
Authors: Cheng Z. L. , Siu K. W. M. , Guevremont R. , Berman S. S.
Published: May 2005

The electrospray mass spectra of MX2and MX3salts (where X is typically halide or nitrate) in protic and aprotic solvents, and solvent mixtures were examined. Comparisons of species responses with equilibrium aqueous solution concentrations were made. For MX2salts, a good correlation between MOH+ response and MOH+ solution concentration was observed under conditions where the collision energy was nominally zero. Cu(II) is easily reduced in acetonitrile to Cu(I); Cu(I) was the principal species observed in the electrospray mass spectrum of Cu(II) in acetonitrile whereas Cu(II) was the principal species observed in that of Cu(II) in dimethyl sulphoxide. Gas‐phase reactions between solvated clusters produced by electrospray and a second solvent vapour were examined. M3+clusters were the principal ions observed when an aqueous solution of MX3was sprayed in the presence of aprotic solvent vapours.
Formation of· CH2CH2CO + and C2H6+· in the metastable decompositions of ionized ethyl formate
Authors: Hudson Charles E. , McAdoo David J.
Published: May 2005

The products of the metastable decompositions of ionized ethyl formate (a) are characterized. The loss of water from a produces ·CH2CH2CO+, a rarely reported product. Loss of H appears to produce CH2=CHC(OH). The third decomposition is an unusual formation of C2H. This work demonstrates that a previous supposition that isomerization to different intermediates is involved in the losses of ethene and of water from a is correct.
Analysis of amino acid mixtures by plasma desorption mass spectrometry
Authors: Hoppilliard Yannik , Mauriac Christine
Published: May 2005

Plasma desorption mass spectrometry (PDMS) was investigated as a means of analysing mixtures of three, four and five amino acids in both positive‐ and negative‐ion modes. Fifteen mixtures were tested; each mixture contained equimolar amounts of selected amino acids. The PD mass spectra exhibited MH+ and [M – H]− molecular ions for all the aminoacids with different desorption–ionization yields. The spectra were more easily interpreted in the negative‐ than the positive‐ion mode. The desorption order of the amino acids was progressively established by comparing the molecular ion desorption–ionization yields for each mixture. This desorption order was well correlated in both the positive‐ and negation‐ion modes with the acid–base thermodynamic data for the amino acids in the gas phase. This observation gives some insight into the desorption–ionization mechanisms under PDMS conditions.
Predicting mold flow for unsaturated polyester resin sheet molding compounds
Authors: Silva‐Nieto R. J. , Fisher B. C. , Birley A. W.
Published: May 2005

Improved products can be obtained from sheet molding compounds (SMC) if due regard is given to the geometry of the molding charge relative to the product shape. For example, it is possible to position designed charge shapes in the mold to produce moldings without weld‐lines and without substantially altering the initial fiber orientation of the SMC matrix. This paper describes theoretical and experimental work which has developed a charge shape calculation procedure for molding two‐dimensional SMC components weld‐line free without substantially altering the SMC‐matrix glass fiber orientation. The two main parts of the work are; (i) The theoretical development of a charge shape calculation procedure for molding symmetrical and unsymmetrical plaques. This includes a mathematical description of the compression flow process, which is used to determine flow front development from mold‐cavity pressure and velocity distributions. (ii) The results of experimental work which test the mathematical description of the compression flow process, and charge shape calculation procedure. These results include mold pressure measurements from an instrumented mold, fiber distribution and orientation measurements, and SMC‐material tensile strength properties.
Impact fracture of glass‐flake reinforced polypropylene
Authors: Vu‐Khanh T. , Fisa B.
Published: May 2005

The impact resistance of glass‐flake reinforced polypropylene was analyzed over a wide range of loading rates and glass‐flake concentrations. It was found that the dynamic fracture toughness, Kd, of the composite is strongly rate‐dependent. When impact velocity is increased, Kd first decreases, attains a minimum value, and then increases with impact speed. The increase in Kd with loading rate is attributed to the blunting effect at the crack tip, induced by adiabatic heating. The addition of glass flakes substantially increases the dynamic fracture toughness of polypropylene. The increase in Kd with glass‐flake content is also more pronounced when the loading rate is increased. The blunting effect was found to increase with glass‐flake concentration up to 30 percent by weight, leading to a stronger increase in Kd with glass‐flake content from 0 to 30 percent. Above 30 percent, the blunting effect diminishes with concentration.
Mechanical performance of various nylon 6 composites formed by in‐situ polymerization of caprolactam
Authors: Goettler Lloyd A. , Neff Willard J.
Published: May 2005

This paper describes the fabrication and mechanical characterization of composites made by incorporating various types of glass as bead or fiber into an activated caprolactam melt, which is then caused to anionically polymerize to a nylon 6 resin. Three types of composites are discussed and compared under separate headings: glass bead filled, sheet reinforced with a random fiberglass mat, and sheet reinforced with a unidirectional fiberglass mat that is studied under transverse loading to emphasize the role of the nylon 6 matrix resin. High molecular weight, better wet‐out and adhesion to the reinforcement, and cold drawing of the polycaprolactam resin lead to homogeneous cavitation that increases composite toughness in comparison to epoxy or other nylon matrices of equivalent stiffness.
Unique orientation of lamellae in film processed poly (phenylene sulfide)
Authors: Huo Peter Pengtao , Chung Jerry Sengshiu , Cebe Peggy
Published: May 2005

The morphology of poly(phenylene sulfide), PPS, obtained as processed film has been studied using wide angle X‐ray scattering (WAXS), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). A unique morphology has been identified in the original film. The spherulites are very small in size and possess a cylindrical symmetry with their lamellae oriented on the edge. In these processed PPS films, the a‐axis of the lattice is preferentially aligned perpendicular to the film plane, while the b and c axes are predominantly in the film plane. In the PPS isothermally crystallized from the melted, original film, there is no such preferential orientation. Thermal analysis of the original and melt crystal‐lized PPS shows that while the degree of crystallinity is about the same, the nature of the amorphous phase in the two materials is different. In the original film, we did not observe a heat capacity increment at a glass transition temperature by DSC, indicating that all of the amorphous phase belongs to the category of rigid amorphous phase. In the melt crystallized PPS, a distinct glass transition was seen, though only a portion of the amorphous phase becomes mobile at Tg. The differences in orientation and mobility of the amorphous phase in the original film compared to melt crystallized PPS are explained by the different thermal processing procedures used for the two materials.
Crystallization behavior and effect of thermal treatment on fracture performance of glass flake reinforced polypropylene
Authors: Denault J. , Vu‐Khanh T.
Published: May 2005

In this work, the role of the interface and matrix morphology in determining the fracture behavior of glass flake reinforced polypropylene is investigated. Differential scanning calorimetric analysis shows that silane coupling agent modifies the crystallization behavior of the polypropylene matrix. Silane treated glass flakes prepared by dry blending are found to induce nucleation and decrease the rate of development of the crystalline entities during the crystallization process. This effect is attributed to the physisorbed layer of silane on the glass flakes. The effect of matrix morphology on the fracture performance is analyzed by fracture mechanics. An increase in matrix crystallinity in pure polypropylene and in glass flake/polypropylene composites leads to a reduction in the maximum crack growth resistance. The lower ductility of a more crystalline matrix results in a reduction of the energy dissipated in the matrix stretching and, therefore, a concomitant decrease in the fracture energy. Although the effect of matrix morphology seemed to be important in the case of pure polypropylene and untreated glass flake polypropylene composites, this effect is found to be negligible for the silane treated composites. Nevertheless, microscopic observation of the fracture surfaces of silane treated composites also revealed a reduction in the ductility of the matrix in highly crystalline samples. An improvement in the matrix‐filler interface seems to inhibit the effect of matrix morphology on the fracture behavior of glass flake/polypropylene composites.
Modeling of the dynamic mechanical properties of semicrystalline thermoplastic matrix composites
Authors: Kenny José M. , Maffezzoli Alfonso , Nicolais Luigi
Published: May 2005

The modeling of the viscoelastic properties of semicrystalline polymeric matrix composites is discussed. Different mathematical models are applied to describe the development of the storage modulus, measured by dynamic mechanical analysis, as a function of the crystalline content during isothermal crystallization experiments. Best results are obtained with an empirical power law model developed in this work. The application of the Halpin‐Tsai equation and of a theoretical model, based on a combination of parallel‐series arrangements of viscoelastic elements representing the crystalline and amorphous phases, is also discussed. The main objective of this research is the comparison between experimental results obtained by differential scanning calorimetry and dynamic mechanical analysis during crystallization processes.
The effect of high pressure on the mechanical behavior of short fiber composites
Authors: Yuan J. , Hiltner A. , Baer E. , Rahrig D.
Published: May 2005

Three types of pressure dependent deformation processes have been observed for the short glass fiber reinforced composites of poly(vinyl chloride) (PVC). A unique deformation behavior, observed for the first time, features a sharp drop in stress followed by shear yielding in the matrix. Competitive pressure dependent failure processes in the composites are strongly affected by “debonding” at the fiber‐matrix interface. A new general pressure dependent yield criterion for PVC and its composites was elucidated.
A novel technique for the determination of high frequency equibiaxial stress‐deformation behavior of viscoelastic elastomers
Authors: Bhate A. P. , Kardos J. L.
Published: May 2005

Synthetic elastomers and elastormeric‐like copolymers are now being utilized for a wide spectrum of biomaterial uses including primary structural applications such as pump bladders in artificial hearts and left ventricular assist devices (LVAD), leaflets in prosthetic heart valves, and vascular prostheses. In making fatigue lifetime measurements, as well as for predicting durability, it is essential to know the biaxial stress‐deformation behavior at high strain rates (high frequencies) and at extension ratios at least as high as those encountered under performance conditions. This paper describes a technique for determining the high frequency equibiaxial stress‐deformation behavior of elastomers. Measurements of material parameters are made at the high strain rates (or frequencies) at which accelerated biaxial flaw growth and fatigue experiments are performed and hence do not require correction for strain‐rate dependence of material properties. Furthermore, the plastic deformation (creep) which occurs in the case of viscoelastic membranes is incorporated in the calculations; yielding the “true” values of the extension ratios. Experimental measurements were performed on urethane‐based biomaterials using a tuned fluid oscillator which produces cyclic biaxial inflation of the elastomeric membranes clamped around the circumference. Up to moderately large equibiaxial deformations, the form of strain energy function derived from the Gaussian, network theory (or the first approximation to Rivlin's formulation of strain energy function) was found to adequately describe the stress‐deformation data. This in turn permits accurate calculation of the tearing energy under biaxial conditions, which is a prime requisite for predicting biaxial fatigue lifetime distributions.
Plastic deformation and tearing in high density polyethylene blown films
Authors: Sherman Edward S.
Published: May 2005

Polymer films produced by tubular film blowing have a unique morphology that results from the large elongational flow in melt draw down and biaxial orientation due to bubble blow‐up. Three high density polyethylene (HDPE) blown films were produced under similar processing conditions from resins which varied principally in molecular weight (MW) and molecular weight distribution (MWD). Scanning electron microscopy (SEM) showed that the lower MW and narrower MWD resin produced film which had a uniaxial orientation of stacked lamellar crystals. The higher MW (HMW) and broad MWD resins produced films consisting of a network of nearly orthotropically oriented lamellar stacks. Greater high molecular weight fraction (MW > 106) in the resin resulted in more random orientation. The influence of these different structures on properties was studied by examining the plastic zone formation at crack tips and uniaxial tensile deformation with the SEM and comparing them to the macroscopic stress‐strain behavior. A continuous deformation of the network structure was observed in the HMW films. Lamellar deformation occurred primarily in regions of stacks oriented parallel to the tensile axis. Macroscopic yield occurred at 6 to 10 percent strain via a shearing and opening the lamellar crystals. Irreversible deformation occurred from ≃50 to 400 percent strain by transformation of the oriented lamellae to microfibrils. Eventually all the lamellar stacks in the network become aligned with the tensile axis. This process was found to improve the tear resistance in the crack propagation experiments. The lamellar stacks in the network orient perpendicular to the crack independent of crack propagation direction, insuring a more uniform transmission of stress and preventing local yielding. The tensile modulus, yield stress, and ultimate strength were highest in the film containing more high molecular weight polymer.
Kevlar 49 composite performance: Dependence on thermoset resin microstructure
Authors: Timm D. C. , Ayorinde A. J. , Lee C. H. , Steele L. F. , Plass N. C.
Published: May 2005

Molecular structures for cured, thermoset resins have been examined by analyses of resin extracts by gel permeation chromatography. Numerical interpretation of leached oligomeric fractions coupled with kinetic reaction theory yields microscopic estimates of the network's structure, including crosslink average molecular weight. Leached monomeric fractions describe extent of cure. Analyses of test data incorporate irreversible, mechanical deformations for neat resin castings and for filament wound, Kevlar 49 composites. Heat distortion temperatures correlate with crosslink architecture. Short beam shear strength data for naval ordinance laboratory rings and pressure vessel burst performance are examined in terms of the resin's molecular structure. Variations in resin cure observed by positive feedback via chromatography indicate fluctuations in extent of crosslink development. Test specimen performance correlates with these microscopic, molecular distributions. Resin applications include filament wound composites for the aerospace industry, anhydride cured epoxies, and amine cured epoxies. The former resin is an elastic body at ambient test conditions. A third resin, a crosslinked resin of 1,2 polybutadiene/t‐butylstyrene, is in final developmental stages and may exhibit a higher degree of viscoelastic behavior.
Concentrated solution and melt rheology of poly(vinylidene fluoride)
Authors: Auyeung Kim Fung
Published: May 2005

The concentrated solution and melt rheology of poly(vinylidene fluoride) [PVDF] were studied by using a falling needle solution viscometer, a Brookfield viscometer, and a Kayeness capillary rheometer. It was found that the concentrated solution (15 wt% in N‐dimethyl acetamide) rheology exhibited a different behavior for various grades of PVDF produced by different types of polymerization. While Newtonian behavior was found in one type of PVDF, shear thinning was found in another type. The power law model was used to describe the general solution behavior of these materials. Zero shear rate viscosity correlated well with the molecular weight (Mw) of the material. Melt viscosity of PVDF exhibited continuous shear thinning behavior throughout the whole range of shear rates. The data were best fitted by a second‐degree polynomial curve. Correlations were established between the molecular weight, molecular weight distribution, and the parameters of the polynomial curve. These correlations are useful for the prediction of various grades of PVDF designated for specific engineering applications. The correlations obtained from solution provided better and more accurate correlations to Mw parameters than those of melt rheology.
Bubble‐free devolatilization in counterrotating nonintermeshing twin‐screw extruder
Authors: Foster R. W. , Lindt J. T.
Published: May 2005

A theoretical analysis of the diffusion‐controlled, essentially bubble‐free, mass transfer regime of polymer solution devolatilization has been performed for a counterrotating, nonintermeshing twin‐screw extruder (1). The commonly used penetration diffusion approach is applied specifically to this geometry. Mass transfer from the recirculating pool and barrel film in the closed channel and the pool only in the open channel is taken into account. Use is made in this study of the recently determined pumping characteristics of this geometry (2), which allow the estimation of the length of the extraction section. Mass transfer rate measurements have been taken on a 20‐mm extruder using the model system polystyrene/ethylbenzene. The agreement between the mass transfer calculations and the experimental results is very good.
Viscoelastic response of epoxy glasses subjected to different thermal treatments
Authors: Lee Andre , McKenna Gregory B.
Published: May 2005

Isothermal aging after a quench from above the glass‐transition temperature (Tg) to below it was studied as a function of cross‐link density for model epoxy networks using small deformation stress relaxation experiments. We found that time‐aging time and time‐cross‐link density superposition principles described the changes observed in the Viscoelastic behavior of the epoxy networks. The aging response in the nonlinear Viscoelastic regime was also studied using creep experiments for one of the networks. It was found that upon aging near to the conventional glass‐transition temperature, the time required for the glass to age into structural equilibrium was independent of the magnitude of the applied stress. This result suggests that large stresses do not erase physical aging (or cause rejuvenation of the glasses).
Effect of emulsifier type on the copolymerization of styrene and acrylic acid
Authors: Corona‐Galvan S. , Martinez‐Gomez A. , Castañeda‐Perez J. , Puig J. E. , Schulz P. C. , Dominguez J. M. , Ruano A.
Published: May 2005

In this work we report the emulsion copolymerization of styrene and acrylic acid using a cationic (cetyltrimethylammonium bromide or CTAB) or an anionic (sodium dodecylsulfate or SDS) emulsifier. Latexes were stable and monodisperse with spherical particles of ∼100 nm for the CTAB latex and of ∼70 nm for the SDS latex. However, a random copolymer was produced with CTAB whereas a “blocky” copolymer was obtained with SDS. Here we propose a mechanism to explain these structural differences in terms of the relative reactivities of styrene and acrylic acid and of their initial location and distribution in the SDS and CTAB emulsions.
A nonlinear mechanical model for solid‐filled rubbers
Authors: So H. , Chen U. D.
Published: May 2005

A nonlinear mechanical model has been proposed for application to nonlinear viscoelastic elastomers. The model consists of four nonlinear elements similar to the Burgers model. Based on the theory of reaction rate proposed by Eyring and the statistic concept of entropy‐spring developed in rubber elasticity, four relevant nonlinear elements are used to construct the model. The deformation, or the time rate of deformation of each element is described by a nonlinear stretch parameter A. According to the model and the parameter A, two groups of equations are derived to describe the creep or relaxation behavior of solid‐filled and pure rubbers, respectively. In order to examine the applicability of the model as well as the nonlinear stretch parameter, a series of experiments for solid‐filled polybutadiene rubbers has been carried out, which include constant rate of tensile tests, creep and relaxation tests with and without aging effects. It is found that the nonlinear stretch parameter satisfies the Eyring equation and that the model agrees the experiments extremely well.
Dopant anion controlled ion transport behavior of polypyrrole
Authors: Qiu Yong‐Jian , Reynolds John R.
Published: May 2005

A combination of electrochemical and microgravimetric techniques, utilizing the electrochemical quartz crystal microbalance (EQCM), has been employed to study the ion transport behavior of polypyrrole films, prepared with a variety of electrolytes, during redox switching. Systems investigated include poly(pyrrole chloride), poly(pyrrole dodecylsulfate), poly{pyrrole‐co‐[3‐(pyrrol‐1‐y1)propanesulfonate]}, and polypyrrole/Nafion composites. It has been demonstrated that controlled ion transport properties of polypyrrole can be achieved by incorporating properly selected dopant anions into the polypyrrole film during electrosynthesis.
Structure and properties of molded polyblends containing liquid crystalline polymers
Authors: Beery D. , Kenig S. , Siegmann A.
Published: May 2005

The relationship between the microstructure developed during injection molding of liquid crystalline polymers (LCPs) containing blends and their mechanical properties, was studied. A wholly aromatic copolyester LCP was melt blended in various levels with polycarbonate (PC), poly(butylene terephthalate) (PBT), Nylon 6 (N‐6), and amorphous nylon (AN). In all cases the LCP was the minor component. The resulting injection molded structure had a distinct skin core morphology, where elongated fibrous LCP particles comprised the skin layer and spherical and ellipsoidal ones composed the core section. The highest elongation and the finest diameter LCP fibrils were obtained with AN/LCP system, followed by PC/LCP. PBT/LCP blends showed a coarser morphology, while N‐6/LCP system did not correlate with the tensile moduli of the injection molded specimens. AN/LCP blends demonstrated the highest moduli values, consistent with the highest orientations observed using electron microscopy, followed by PC/LCP, PBT/LCP, and N‐6/LCP. Finally, tensile strength levels were correlated with both orientation levels and interfacial adhesion between the polyblend components. AN/LCP that exhibited the highest orientation and good adhesion appearance gave the highest tensile strength values followed by PC/LCP, PBT/LCP, and N‐6/LCP polyblends.
A robust, streamlined, and reproducible method for proteomic analysis of serum by delipidation, albumin and IgG depletion, and two‐dimensional gel electrophoresis
Authors: Fu Qin , Garnham Christopher P. , Elliott Steven T. , Bovenkamp Diane E. , Van Eyk Jennifer E.
Published: May 2005

Serum is a readily available source for diagnostic assays, but the identification of disease‐specific serum biomarkers has been impeded by the dominance of human serum albumin and immunoglobulins (Igs) in the serum proteome. There is a need to reduce the technical variation in serum processing and analysis to allow for a reproducible analysis of large cohorts. To this end, we have developed a rapid and reproducible procedure for sample preparation and high‐resolution two‐dimensional gel electrophoresis to analyze human serum. Serum is centrifuged at high speed to remove lipids and aggregated proteins, incubated with protein G resin to remove IgG, precipitated with NaCl/ethanol to deplete albumin, and slowly resolubilized in a sodium dodecyl sulfate (SDS)/N‐(2‐hydroxyethyl)piperazine‐2’‐(2‐ethanesulfonic acid) (HEPES) buffer. The delipidated and IgG/albumin depleted serum proteins are focused on pH 4–7 linear large immobilized pH gradient strips, and then resolved by Bis‐Tris SDS‐polyacrylamide gel electrophoresis. The robustness and reproducibility of the optimized procedure was determined for three individual serum samples on three consecutive days. An image analysis of the nine silver‐stained gels demonstrated that the intensity and localization of protein spots are highly reproducible. Our IgG and albumin depletion procedure will aid in screening the patient sera for normal biological variation and disease‐specific biomarkers.
Controlling the Plasma‐Polymerization Process of N‐Vinyl‐2‐pyrrolidone
Authors: Norrman Kion , Winther‐Jensen Bjørn
Published: May 2005

Summary: N‐vinyl‐2‐pyrrolidone was plasma‐polymerized on glass substrates using a pulsed AC plasma. Pulsed AC plasma produces a chemical surface structure different from that produced by conventional RF plasma; this is ascribed to the different power regimes used. A high degree of control over the structure of the chemical surface was obtained using pulsed AC plasma, as shown by ToF‐SIMS. It is demonstrated how the experimental conditions to some extent control the chemical structure of the plasma‐polymerized film, e.g., film thickness, density of post‐plasma‐polymerized oligomeric chains, and the density of intact pyrrolidone rings.

Electrode configuration and gas flow in the two‐phase AC plasma chamber.

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Electrode configuration and gas flow in the two‐phase AC plasma chamber.
Flow Pattern in an Indoor Rocket Test Stand during static rocket motor firing
Authors: Korting P. A. O. G. , Reitsma H. J.
Published: May 2005

Experiments to determine the flow pattern in an indoor rocket test stand during static rocket motor firing are described. After a theoretical treatment of the flow properties, a description is given of the experimental set‐up. Tests were performed with short burning (1.8 s), low thrust (2,8 kN) rockets as well as with a long burning (40 s) rocket motor with higher thrust (9.5 kN). With the short burning rocket motors flow velocities obtained were between 3.3 m/s and 7.9 m/s. The stationary flow velocities of the long burning rocket motor amounted up to 24 m/s, while the increase in temperature of the flow was appr. 200 K. Experimental flow velocity appeared to be lower while the experimental flow temperature appeared to be higher than the theoretical values, mainly due to after burning of the fuel‐rich combustion gases.
Determination of the Decomposition Behavior of Double‐Base Propellants at Low Temperatures
Authors: Volk F. , Wunsch G.
Published: May 2005

Thermal and mechanical stability are very important characteristics of energetic materials used as ingredients of propellants compositions. For the determination of the thermal decomposition behavior of solid double base propellants, usually gravimetric, calorimetric, and chemical methods are being employed. At ICT, the decreasing rates of stabilizers determined by high‐performance chromatography at different temperatures are successfully used as a mean to forecast the chemical life time of propellants containing nitric esters. On the other hand, the mechanical properties are evaluated by measuring the tensile strength with a more or less accuracy.

In the last years, the increasing performance of the gel‐permeation chromatography enabled the determination of the molecular weight and the molecular weight distribution of nitrocellulose in different propellants. In this connection a linear relationship between temperature and depolymerization rate was obtained. This relationship corresponds fairly well with the stabilizer depletion rate and the drop in the mechanical properties.