bluuebunny/crossref_metadata_2025 huggingface dataset:
Elimination and rearrangement reactions in the electron impact ionization mass spectrometry of 2,4,5,5‐tetrasubstituted 1,2,4‐triazolidine‐3‐thiones
Authors: Pihlaja Kalevi , Mäki Esa , Schulze Klaus , Richter Christian
Published: May 2005

The electron impact mass spectra of 2,4,5,5‐tetrasubstituted l,2,4‐triazolidine‐3‐thiones exhibited, in addition to four main routes of fragmentation, a reaction leading to the formation of 5‐alkyl‐l,2,4‐triazoline‐3‐thiones via an elimination of HR4 (R3 ≤ R4 are the substituents at C(5)) or via a McLafferty‐type reaction from the rearranged molecular ion in the case of the 5,5‐spiro derivatives. Substitution at N(2), N(4) and/or C(5) had a decisive effect on the contribution of the alternative reaction routes. Some fragments via the triazoline‐thione structure were also formed.
Matrix‐assisted laser desorption of neutral organic molecules
Authors: Kinsel Gary R. , Lindner Josef , Grotemeyer Jürgen
Published: May 2005

Results of initial investigations of matrix‐assisted laser desorption (LD) of neutral molecules are presented. The investigations were performed using gramicidine D as the test molecule, since both the wavelength‐dependent LD beharioor and the ionization and fragmentation behaviour of the pure material had been studied previously. Comparisons between previously reported results for the pure compound and the matrix mixtures used in these studies are made. The results show that, whereas no signal could be observed from the pure sample material at non‐resonant desorbing wavelengths, addition of a strongly absorbing matrix to the sample initiated LD of abundant intact neutral sample molecules. The results are discussed in the light of previous studies of the LD mechanism and support an explosive, mechanically driven model for the LD process.
Fragmentation of ion–molecule adducts of transition metal ions with aromatic ring‐containing nitriles in the gas phase
Authors: Chen Lin‐Zhi , Miller Jack M.
Published: May 2005

Gas‐phase ion–molecule reactions of transition metal ions, M+ (M+ = Ni+, Co+, Fe+ and Mn+), with six aromatic ring‐containing nitriles were investigated in a modified fast atom bombardment (FAB) source. It is shown that the monoadduct, (Ph(CH2)nCN)–M+, is one of the most abundant ion–molecule reaction products. The main fragments in the FAB source are the [C7H7]+ and [C8H9]+ ions, and their formation is shown to involve metal ion insertion into the nitriles rather than direct bond cleavage from the ‘free’ or complexed nitriles after FAB ionization. An intramolecular oxidation–reduction reaction, giving [C7H7]+, is found in the metastable and collisionally induced dissociations of benzyl nitrile adducts accompanied by neutral MCN formation, but not seen for longer chain samples. An ortho effect is observed in the elimination of HCN from the 2‐methylbenzyl nitrile adduct ions. This reaction dominates the metastable ion spectrum of the adduct of Mn+, whereas metal detachment is nearly the major process for the other complexes of Mn+. The different bond‐insertion selectivities of the metal ions are also shown.
Competition between substitution (SN2), elimination (E2) and addition elimination (AE) reactions in the gas Phase
Authors: Haib J. , Stahl D.
Published: May 2005

The competition between substitution (SN2), elimination (E2) and addition–elimination (AE) reactions in the gas phase has been studied by using OH− and NH2− as nucleophiles reacting with esters of acetylenedicarboxylic acid of general formula RO(O)CCCC(O)OR′. By selectively varying R and R′ it was possible to show that the E2 reaction predominates over SN2 and that the relative contributions of the three reactions with OH− follow the decreasing order AE > E2 > SN2, whereas for NH2− it is E2 > AE > SN2. The E2 reaction is discussed in terms of substituent effects, relative acidity of the different β‐hydrogens and geometry of the transition state. For the AE reaction a leaving group order for this class of compounds was established.
Ion—molecule chemistry of pyrene in an ion‐trap mass spectrometer
Authors: Nourse B. D. , Cox K. A. , Cooks R. G.
Published: May 2005

The quadrupole ion‐trap mass spectrometer is used to investigate aspects of the ion‐molecule chemistry of the pyretic molecular radical cation (M+), the [M  H]+ ion and the [M  H2]+˙ ion. Cycloaddition and alkyl halide addition reactions with the reagents pyrene, methyl iodide, ethyl iodide, isopreue and 2‐iodopropane are investigated. The pyrene molecular radical cation is remarkably unreactive while the closed shell [M  H]+ ion is highly reactive and the [M  H2]+˙ ion shows intermediate reactivity. Analogies are found between the behaviour of the pyrene molecular radical cation and the corresponding [M  H]+ ion on the one hand, and the benzene radical cation and the phenylium ion on the other. The total lack of reactivity of the M+˙ ion is attributed to π‐delocalization of the radical and the cation over the large aromatic system. Addition of isoprene to the [M  H]+ and [M  H2]+˙ ions of pyrene occurs via cycloaddition reactions. A characteristic fragmentation of each adduct ion is methyl radical loss and evidence obtained using pyrene‐d10 indicates that the product in the case of [M  H]+ is an ionized indene. Addition of methyl iodide, ethyl iodide and 2‐iodopropane to the [M  H]+ ion of pyrene occurs to give an iodonium product (C16H9–I+–R) which fragments by loss of I˙ or CH3˙ to give the methylpyrene or iodopyreue product ions. Reactions of ethyl iodide and 2‐iodopropane with the dehydropyrene ion, [M  H2]+˙, give primarily an HI addition product, together with small contributions from the intact adducts. Evidence is provided suggesting that in this case the HI and alkyl halide molecules add across a CC bond rather than forming an iodine‐bound adduct. An experiment in which nine consecutive isolation and activation steps (MS10) are used to couvert the [2M  H]+ adduct, C32H, to C32H˙ exemplifies the intriguing ion chemistry and the stability of the carbon skeleton of the adduct ions.
Application of gas chromatography/mass spectrometry to steroid analysis in equine sports: Problems with enzyme hydrolysis
Authors: Houghton E. , Grainger L. , Dumasia M. C. , Teale P.
Published: May 2005

In steroid analysis in biological fluids, cleavage of conjugates is an essential step which can be achieved by either enzymatic or chemical hydrolysis. Where conjugation with both glucuronic acid and sulphate occurs, then the use of the enzyme preparation from Helix pomatia, containing both β‐glucuronidase and aryl sulphatase activities, would appear to be advantageous. However, it has been shown that the sulphatase enzymes of Helix pomatia do not hydrolyse 17β‐sulphates and that other enzymatic activities also present in the preparation can give rise to artefact formation with certain steroids.

The artefacts produced from incubation of dehydroisoandrosterone with the enzyme preparation from Helix pomatia have been identified by gas chromatography/mass spectrometry (GC/MS) as androst‐4‐ene‐3,17‐dione, androsta‐4,6‐diene‐3,17‐dioue, androst‐4‐ene‐3,6,17‐trione and 6‐hydroxyandrost‐4‐ene‐3,17‐dione. Incubation of androst‐5‐ene‐3,17‐diol produced a similar series of compounds with a 17‐hydroxy function. Semi‐quantitative GC/MS analysis has been used to determine the extent of these transformations in the presence of increasing amounts of the Helix pomatia preparation. Quantitative conversion in buffer can be obtained but the results from incubation in urine showed a marked modifying effect with minimal artefact formation. The enzyme preparation from Escherichia coli does not yield any artefacts and results are presented for the optimization of its use in the hydrolysis of the glucuronic acid conjugate of 5α‐estrane‐3β,17α‐diol, the major metabolite of nandrolone in the horse.
Collisionally activated dissociation of 2,4,6‐triphenylpyridinium cations
Authors: Katritzky Alan R. , Malhotra N. , Dega‐Szafran Zofia , Savage G. Paul , Eyler John R. , Watson Clifford H.
Published: May 2005

Thresholds for the appearance of fragment ions allowed the estimation of threshold fragmentation energies (TFE) for the collisionally activated dissociation (CAD) in the gas phase of laser‐desorbed pyridine‐ring substituted N‐benzylpyridinium cations to form pyridine and a carbocation. p‐Methylbenzylpyridinium cation underwent an alternative CAD into pyridinium cation and the p‐quinodimethane. The TFE are discussed in comparison with the energy differences (ΔΔHf = ΔHf(Py) + ΔHf(R+) − ΔHf(Py +R) calculated by the AM1 method to provide strong evidence for benzyl to tropylium cation rearrangement in an ion‐molecule pair.
Methane positive‐ion chemical ionization mass spectra of phenols
Authors: Iida Yoshio , Daishima Shigeki , Shibata Akihiro
Published: May 2005

Positive‐ion chemical ionization mass spectra for 48 phenols were measured using methane as the reagent gas in order to clarify their characteristics. The ion species obtained were almost identical with those generated in alkyl‐benzenes except for dehydrated ions produced from MH+ and adduct ions, in particular compounds such as pyrocatechol. Specific ions such as C6H7O+ (m/z 95) and C8H11O+ (m/z 123) in phenol derivatives (C6H4 · OH · R; R = CnH2n + 1, n ≥ 3) and [C7H9O]+ (m/z 109) and C9H13O+ (m/z 137) in cresol derivatives (C6H3 · OH · CH3 · R) were formed, respectively, by alkene elimination reaction from MH+ and [M + C2H5]+. The characteristic [M + 13]+ and [M + 15]+ ions observed in several phenols were identified as [M + C3H5 – C2H4]+ ([M + CH]+) and [M + C3H7 – C2H4]+ ([M + CH3]+), respectively, by tandem mass spectrometry.
Tandem mass spectrometry of aminated fullerene derivatives
Authors: Davey Simon N. , Tetler Lee W. , Leigh David A. , Moody Andrew E.
Published: May 2005

The products of the reaction between fullerenes (C60/C70) and dimethylamine were investigated by fast atom bombardment (FAB) mass spectrometry and tandem mass spectrometry (MS/MS). The FAB mass spectrum shows peaks corresponding to the addition of up to eight dimethylamine species, exclusively to C70. MS/MS reveals an unusual fragmentation pattern. The mass spectrum of the reaction products, together with a number of tandem mass spectra, are shown.
Study of the major fragmentation pathways of cypermethrin and related synthetic insecticides using tandem mass spectrometry
Authors: Fleet Ian A. , Tetler Lee W. , Monaghan John J.
Published: May 2005

Fragmentation pathways of the synthetic pyrethroid cypermethrin and four structurally related insecticides were investigated using a tandem quadrupole mass spectrometer incorporating a hexapole collision cell under positive‐ion electron impact ionization conditions. Conventional mass spectrometry using the first quadrupole analyser only and tandem mass spectrometry on selected precursor ions and product ions, and also constant neutral loss scan experiments, were used. Mechanisms and fragmentation pathways are proposed to explain the inherent stability of ions associated with the benzylphenoxy portion of this class of insecticide.
Ion–molecule reactions and dissociation of glycols in a quadrupole ion trap mass spectrometer: Evidence of intramolecular interactions
Authors: Eichmann Erika S. , Brodbelt Jennifer S.
Published: May 2005

Polyethylene glycols react with CH3OCH2+ ions from dimethyl ether to form [M + 13]+ products. The [M + 13]+ ions are stabilized by intramolecular interactions involving the internal ether oxygen atoms and the terminal methylene group. Collisionally activated dissociation (CAD), including MSn and deuterium labeling experiments show that fragmentation reactions involving intramolecular cyclization are predominant. Scrambling of hydrogen and deuterium atoms in the ion‐molecule reaction products is not indicated. The CAD spectra of the [M + 13]+ ions provide unambiguous assignment of the glycol size.
Formation and identification of ionized and neutral cumulenes, RNCCCNH, by tandem mass spectrometry
Authors: Flammang Robert , Laurent Sophie , Flammang‐Barbieux Monique , Wentrup Curt
Published: May 2005

Using a combination of mass spectrometric techniques, it is shown that 5‐amino‐4‐cyanoisoxazole molecular ions (1+˙), lose isocyanic acid HNO, not fulminic acid, HCN → O. Metastable ion fragmentations (unimolecular and collision induced) and deuterium‐labelling experiments are in agreement with the formation of a cumulenic structure, HNCCCNH (3a+˙). The hitherto unreported molecules HNCCCNH are also shown to be stable when formed in the low‐pressure gas phase of the mass spectrometer by using the technique of neutralization–reionization mass spectrometry. The arguments developed for the characterization of 3a+˙ have also been extended to the methylated and phenylated analogues 3b+˙ and 3c+˙ [RNCCCNH+˙, R = CH3 or C6H5]. On flash‐vacuum pyrolysis at 700°C, 1 also loses HNCO producing the cumulene 3a, which is in turn readily tautomerized into malononitrile via wall collisions.
Rearrangements in metastable ion decompositions of protonated propylamines
Authors: Audier Henri E. , Morton Thomas Hellman
Published: May 2005

Decomposition of nPrNH3+ to NH4+ does not occur via vicinal elimination. Hydrogen transfer takes place from all positions of the alkyl chain. Intermediacy of either an ion–neutral complex. [iPr+ NH3], or rearrangement to iPrNH3+ is required. SCF calculations were used to probe the potential energy surface. There is a minimum corresponding to [iPr+ NH3], in which the nitrogen lone pair points towards the machine hydrogen and is 2.1 Å away from it, and another, less stable, minimum corresponding to a hydrogen‐bonded structure, H3N …︁ H3CCHCH3+, in which one methyl hydrogen is 2.0 Å from the nitrogen. Density of states estimates suggest that avibrationally excited complex can live for the order of 100 ps before either collapsing to iPrNH3+ or yielding NH4+ and propene.
Unimolecular reaction dynamics from kinetic energy release distributions. 1—dissociation of bromobenzene ions
Authors: Lorquet J. C. , Leyh B.
Published: May 2005

Preliminary data on a new method for extracting dynamic data from the kinetic energy release distribution of metastable fragment ions are presented. This method can give information concerning the energy threshold of the reaction and the energy dependence of the rate constant (i.e. its logarithmic derivative). It was applied to bromine loss from bromobenzene cations.
On the sodium and lithium ion affinities of some α‐amino acids
Authors: Bojesen Gustav , Breindahl Torben , Andersen Ulla N.
Published: May 2005

The decomposition of 59 different cluster ions (generated by fast atom bombardment) consisting of two different amino acids and a sodium ion was analysed. The only fragment ions of significant abundance could be assigned to sodium ion‐bound amino acids. Assuming that the most abundant ion in the fragment ion spectrum corresponds to the amino acid with the highest sodium ion affinity (SIA), the 20 common α‐amino acids could be ordered with increasing sodium ion affinity as follows: Gly, Ala, Cys, Val, (Leu, Ile), Ser, Met, Thr, (Phe, Pro), Asp, Tyr, (Glu, Lys), Trp, Asn, Gln, His, Arg. Quantitative determinations were carried out by comparison of the lithium ion affinity (LIA) of Ala with that of dimethylformamide (DMF) in a fragment ion scan of the ion‐bound dimer Ala—Li+—DMF. LIA(Ala) was calculated from LIA(Ala) = LIA(DMF) – (1/C)ln[I(AlaLi+)/I(DMF—Li+)], where the constant C was estimated from measurements of proton‐bound amine–amino acid clusters. From fragment ion analysis of nine other Li+‐bound α‐amino acid dimers, the following lithium ion affinities were obtained: Gly 51.0, Ala 52.6, Sar 53.5, α‐aminobutyric acid 53.7, glycine methyl ester 54.7 and Val 54.8. SIA(Ala) was estimated to be 75% of the lithium ion affinity and from fragment ion analysis of ten Na+‐bound α‐amino acid dimers the following sodium ion affinities were obtained: Gly 37.9, Ala 39.4, α‐aminobutyric acid 40.3, Val 41.0, glycine methylster 41.0 and Sar 41.2.
Direct peptide profiling of single neurons by matrix‐assisted laser desorption–ionization mass spectrometry
Authors: van Veelen P. A. , Jiménez C. R. , Li K. W. , Wildering W. C. , Geraerts W. P. M. , Tjaden U. R. , van der Greef J.
Published: May 2005

Peptide profiles of single neurons in Lymnaea stagnalis were directly characterized by matrix‐assisted laser desorption–ionization mass spectrometry. The mass analysis was performed after minor pretreatment and without any separation steps. Good‐quality spectra were obtained of several cell types and also other tissues. The results were compared with the results of conventional peptide chemical methods. In addition to many known peptides, several new peptides were identified. The method provides new opportunities for studying peptide compositions at the single‐cell level, which is shown to have many advantages.
Alkylation in electron impact mass spectrometry of hydrobromides of 2‐alkylthioorotic acids
Authors: Wyrzykiewicz E. , Bartkowiak G.
Published: May 2005

The mass spectral fragmentations of eight 2‐alkylthioorotic acids and their hydrobromides were investigated. Fragmentation pathways, the elucidation of which was assisted by accurate mass measurements and metastable transitions, are proposed. It was found that there is evidence in the electron impact mass spectra of the hydrobromides of 2‐alkylthioorotic acids of intermolecular transfer of an alkyl group.
Ion cyclotron resonance mass spectrometric study of ion—molecule reactions in toluene—pyridine mixtures
Authors: Katritzky Alan R. , Dega‐Szafran Zofia , Ramanathan Ragulan , Eyler John R.
Published: May 2005

Ion—molecule reactions in toluene, toluene‐d8, pyridine, 4‐methyl‐, 4‐ethyl‐ and 4‐terr‐butylpyridine and quinoline and their mixtures were studied by ICR mass spectrometry at 10‐7 Torr (1 Torr = 133.3 Pa). The reactions of benzyl (m/z 91), benzyl‐d7 (m/z 98), methylbenzyl (m/z 105), and azabenzyl (m/z 92) ions with pyridines and quinoline were observed. The reactions of protonated pyridines with unprotonated molecules leading to homoconjugated ions (BHB)+ were detected.
Efficiency of collision‐induced ionization of fast neutrals: Effects of neutral internal energy and neutral translational energy
Authors: Harnish David , Holmes John L.
Published: May 2005

The ionization efficiencies of fast beams of CO and C2H4, with oxygen as target gas were shown to increase with increasing translational energy and to decrease with increase in internal energy. The latter may arise from a greater probability of homolysis in the neutral projectile species; it is not likely to arise from increased ionization of the target. Experimental parameters (and their validity) relating to the measurement of collision‐induced dissociative ionization mass spectra and which are also applicable to the reionization step in neutralization—reionization mass spectra were investigated.
Mechanism of stereospecific alcohol elimination from cyclohexane trans‐1,3‐dicarboxylates under electron impact ionization
Authors: Etinger A. , Idina A. , Mandelbaum A.
Published: May 2005

Diesters of cyclohexane trans‐1,3‐dicarboxylic acid give rise to major [M  ROH]+·. ions under electron impact ionization. A mass spectral study of the isomeric mixed methyl ethyl esters of the diacid, substituted by a methyl group at position 1 and deuterium labelled at position 3, indicates a stepwise mechanism for this alcohol elimination; the 3‐hydrogen (or deuterium) is transferred to the carbonyl of the 1‐ester group in the initial step. Subsequent migration of that hydrogen (or deuterium) to the alkoxyl of position 3 results in the highly site‐ and stereospecific alcohol elimination. CID spectra of the [M  ROH]+. ions obtained from the stereoisomeric diesters clearly show that they have different structures (or are different mixtures of structures).
Fragmentation of collisionally activated hydroxyphenoxide anions in the gas phase
Authors: Binkley Roger W. , Dillow Glen W. , Flechtner Thomas W. , Winnik Witold , Tevesz Michael J. S.
Published: May 2005

Low‐energy collisionally activated dissociation of O‐deprotonated dihydroxybenzenes (catechol, resorcinol, hydroquinone) in the gas phase causes both fragmentation to form [C6H4O2]– ions by loss of the remaining oxygen‐bound hydrogen atom and intramolecular hydrogen atom migration from O to C. The rearranged anions then undergo ring‐cleavage reactions which are different in each case. Both catechol and hydroquinone produce fragments which are the result of the loss of two carbon atoms and both oxygen atoms but the proposed mechanisms are different. Resorcinol also produces a fragment which derives from the loss of carbon dioxide. For this process a mechanism is proposed which involves a 6‐methylpyranone anion intermediate.
Curie‐point pyrolysis gas chromatography/mass spectrometry in the identification of paint media
Authors: Carbini Massimo , Volpin Stefano , Traldi Pietro
Published: May 2005

Curie‐point pyrolysis gas chromatography/mass spectrometry has been applied to different model paint samples containing proteinaceous (egg yolk) and oily (linseed oil) media. Results of pyrolysis at 610°C are highly reproducible, and among the different pyrolysis products some compounds diagnostic for the different binders have been identified. The application of the method to real samples, i.e. from the oil painting ‘Ritratto’ by Giuseppe Nogari (1669–1763) and from the tempera paint on the ligneous roof of S. Giobbe church (16th century) in Venice, proves its effectiveness in the identification of binding media.
Formation of nanocomposites of styrene and its copolymers using graphite as the nanomaterial
Authors: Uhl Fawn M. , Yao Qiang , Wilkie Charles A.
Published: May 2005

Graphite‐polymer nanocomposites were prepared by melt blending of various graphites (virgin graphite, expandable graphites, and expanded graphite) with polystyrene and its copolymers (acrylonitrile‐butadiene‐styrene (ABS) and high‐impact polystyrene (HIPS)). Nanocomposites were characterized by X‐ray diffraction, cone calorimetry, thermogravimetric analysis and evaluation of mechanical properties. Nanocomposite formation occurs at higher loadings (3–5%) of expandable graphites but not for virgin or expanded graphite. Copyright © 2005 John Wiley & Sons, Ltd.
Fire retardancy of polyethylene‐alumina trihydrate containing clay as a synergist
Authors: Zhang Jinguo , Wilkie Charles A.
Published: May 2005

The fire behavior of polyethylene combined with alumina trihydrate (ATH) and an oligomerically‐modified clay has been studied. The combination of polyethylene with 2.5% inorganic clay and 20% ATH gives a 73% reduction in the peak heat release rate (PHRR), which is the same as that obtained when 40% ATH is used alone. A further increase in the clay loading does not improve the fire properties. Mechanical properties, such as elongation at break, can be improved in comparing compounds with or without clay at the same reduction in PHRR. The oligomerically‐modified clay can also facilitate the melt blending process. Copyright © 2005 John Wiley & Sons, Ltd.
Model compound studies on the amine cure of epoxy resins
Authors: Byrne Catherine A. , Hagnauer Gary L. , Schneider Nathan S. , Lenz Robert W.
Published: May 2005

Monoepoxy phenyl glycidyl ether, curing agent p‐chloroaniline, and the substituted urea type accelerator Monuron were used as a model system for studying the amine cure of epoxies. Reactions were carried out at 120°C with amine to epoxy equivalent rations of 0.25 and 1.0 Reaction mixtures were analyzed primarily by reverse phase high performance liquid chromatography. Three types of reactions occur; simple amine addition to epoxy, homopolymerization of epoxy, and epoxy polymerization involving the addition products. In the absence of accelerator the reaction involved simple addition. With the accelerator, there was competition between addition and polymerization, the balance depending on the amine to epoxy equivalent ratio. Both addition and polymerization were important for a ratio of 1, but polymerization far outweighed addition for a ratio of 0.25.
Fatigue characteristics of high glass content sheet molding compound (SMC) materials
Authors: Mallick P. K.
Published: May 2005

Static and fatigue properties of high glass content sheet molding compound (SMC) materials were studied at various temperatures. It was shown that the matrix plays an important role in both fatigue characteristics and failure mechanism of such randomly oriented short fiber composites. Specifically, vinyl ester matrix shows better fatigue properties and post‐fatigue performance than the polyester system considered here.
Strength improvement of short graphite fiber‐reinforced polypropylene
Authors: Weiss R. A.
Published: May 2005

The Improvement of the tensile strength of discontinuous graphite fiber‐reinforced polypropylene is described. Two methods were employed: (1) modification of the polymer backbone by the introduction of acrylic acid grafts and (2) varying the chemistry of the fiber sizing. The strength improvements attained are attributed to intermolecular interactions, such as hydrogen bonding, which improve the adhesion between the fiber and the polymer.
Behavior of an aramid fiber under uniform compression
Authors: Deteresa Steven J. , Farris Richard J. , Porter Roger S.
Published: May 2005

A new method of applying small (<3 percent) and uniform compressive strains to organic fibers by shrinkage of a surrounding polymer matrix is reported. The results of this matrix‐induced compression on the morphology and tensile properties of Kevlar fiber are examined.
Fatigue crack growth and fracture in glass sphere‐filled nylon 6
Authors: Friedrich K. , Karsch U. A.
Published: May 2005

The common degrading effect of glass beads on the static fracture energy and the fatigue crack propagation response in nylon 6 materials is examined by conducting fracture mechanics tests and by considering the progress of cracks through the composites. The scanning electron micrographs indicate that the cracks travel through regions of polymer matrix and also along the interfaces between polymer and glass beads. It is demonstrated that, although fracture of the polymer regions requires considerable energy, cracking of the interfaces usually absorbs very little. Thus, the crack propagation is preferably concentrated on these microstructural regions, which is the cause of the decrease in fracture energy and increase in fatigue crack growth rate with increasing amount of glass spheres in the composite. Partial properties of the matrix and the interface are introduced in order to describe the fracture behavior and to improve the understanding of the gross fracture processes. The combination of these partial properties with the volume fraction of filler and certain geometrical factors by a modified rule of mixture leads to critical values for the failure of the composites, which are in reasonable accord with the measured fatigue and fracture data.
Tribological properties of polyesterimide and its composites
Authors: Ghosh U. K. , Jagga C. R. , Maiti S. , Vasudevan P.
Published: May 2005

Polyesterimide (PEI) and phenol formaldehyde (PF) samples were synthesized, and composites of the two polymers, as well as composites with carbon, were prepared. Using a pinon‐disc machine, the friction and wear properties of the following samples were studied in the load range of two to eight bars:

Phenolformaldehyde vs. steel

Phenol formaldehyde cured with hexamethylenetetramine vs. steel

Polyesterimide vs steel

Polyesterimide and carbon composite vs steel

Phenol formaldehyde vs polyesterimide

Phenol formaldehyde and polyesterimide composite vs. phenol formaldehyde

Phenol formaldehyde and polyesterimide composite vs. steel.

The data obtained from these experiments were compared with literature data on poly(tetrafluoroethylene) and nylon, conventionally used for tribological applications. It is seen that, in terms of thermal stability, friction, and wear, PEI and PF are promising for tribological applications.
The extrusion and performance of plasticized poly(vinyl chloride) hose reinforced with short cellulose fibers
Authors: Goettler Lloyd A.
Published: May 2005

Short fibers of natural cellulose treated to provide dispersability and strong interfacial bonding are ideal reinforcements for plasticized vinyl compounds. The development of substantial strength and stiffness in unidirectional composites indicates the reinforcing potential of these high aspect‐ratio fibers in soft compositions. Special extrusion dies developed to control fiber directionality in rubber extrudates are equally applicable to vinyl hose. The unusual expanding geometry of these tools aligns the fibers toward the circumferential direction to provide optimum reinforcement against contained pressure loading. Thus, reinforced poly(vinyl chloride) air and water hoses can be produced in a single extrusion step, since all of the necessary reinforcement is contained in the compound.
Stress relaxation properties of some reaction injection molded (RIM) and reinforced RIM systems
Authors: Turner R. B.
Published: May 2005

This study examined the stress relaxation properties of six urethane reaction injection molded (RIM) systems, both reinforced and non‐reinforced RIM systems from room temperature to 100°C. Data is presented which shows the dynamic mechanical (DMS), differential scanning calorimetry (DSC), physical properties, and stress relaxation data. The major conclusion from this work is that the state of hard segment (amorphous or crystalline) makes a vast difference in the polymer's reaction to stress.
Mechanical properties and morphology of polypropylene composites. Talc‐filled, elastomer‐modified polypropylene
Authors: Stamhuis J. E.
Published: May 2005

The balance of impact strength and rigidity of polypropylene can be significantly improved by physical blending of the polypropylene with a talc filler and a variety of elastomer types. Unsaturated elastomers were found to be effective impact strength improvers in 70/15/15 percent PP/elastomer/talc composites, whereas saturated elastomers gave rise to a high stiffness of such compounds. This is attributed primarily to different tendencies of the elastomers to coat the filler surface. Studies on a wider range of compositions, using a butadienestyrene‐butadiene (SBS) block copolymer and a ethylene‐propylene‐diene (EPDM) terpolymer as representatives of the two elastomer classes, indicated that at high stiffness levels (flexural modulus > 1.6 GN/m2), the composites with SBS show the best balance of properties, whereas at higher impact levels EPDM leads to a higher rigidity and impact strength. On the basis of morphological studies such differences can be explained qualitatively, in spite of the complex structure of these composites.
Influence of glass fiber content on the morphology and mechanical properties in injection molded polypropylene composites
Authors: Xavier S. F. , Misra A.
Published: May 2005

Propropylene was reinforced with various concentrations of glass fiber (0, 10, 20, 28, and 35 percent by weight) and standard test samples were prepared by injection molding under identical conditions. The influence of fiber concentration on the morphology and mechanical properties was investigated using polarizing microscope, scanning electron microscope, Instron universal testing machine, etc. Tensile strength, tensile modulus, and flexural strength were found to increase with glass fiber content, while impact strength was reduced. These observed changes in mechanical properties were explained in terms of alterations in skin‐core morphology, spherulite size, transcrystallinity, etc. The efficiency of reinforcement factor (K) was calculated for all the composites. It was found that K decreases with the increase of fiber concentration. This study attempts to correlate fiber concentration and polymer morphology with mechanical properties and the overall efficiency of reinforcement. This would help in optimizing the fiber content to prepare molded composites with desired mechanical properties.
Solid state extrusion of semicrystalline polymers
Authors: Krjutchkov A. N. , Dorfman I. Y. , Prut E. V. , Enikolopyan N. S.
Published: May 2005

The dynamics of solid state extrusion of polypropylene, high density polyethylene, and poly(tetrafluorethylene) have been investigated at various extrusion temperatures and piston velocities. A model of solid state extrusion of semicrystalline polymers is proposed. The formulae are obtained relating the value of the extrusion pressure with the parameters of the process and polymer properties. It has been found that for certain values of the parameters, defects of two main types emerge. A mechanism of defect formation is suggested.
Engineering analysis of reaction injection molding process of epoxy resin
Authors: Kim Do Hyun , Kim Sung Chul
Published: May 2005

An engineering analysis of reaction injection molding (RIM) process of epoxy resin was carried out through numerical simulation and actual experiment. In order to simulate the RIM process, and reaction kinetics and the viscosity function of the epoxy system were obtained from thermal analysis and rheological measurement, and the balance equations of the chemical species, momentum, and energy within a mold cavity were set up in cylindrical coordinates. As the result of the simulation, the temperature and conversion profiles within a disc type mold were obtained and a moldability analysis was made to find the optimum molding conditions. The temperature change during the curing reaction, at a fixed point within the mold cavity, was measured through the actual RIM experiment on a small scale, and was compared with the simulated results.
Characterization of thermoset cure behavior by differential scanning calorimetry. Part II: Effects of low‐profile additives
Authors: Lam P. W. K.
Published: May 2005

An autocatalyzed second‐order kinetic model was adopted to compare the isothermal and dynamic cure behavior of low‐profile polyester resins in terms of kinetic parameters such as degree of cure, cure rate, half‐life, onset cure temperature, reaction order, and Arrhenius parameters. The reaction orders of low‐profile unsaturated polyesters appear to be almost independent of isothermal cure temperatures. The ultimate conversion, conversion at peak maximum, onset cure temperature, and Arrhenius parameters of polyesters are only slightly affected by the concentration and type of low‐profile additives in the resins. Low‐profile additives, in general, tend to retard the cure rate and suppress the exothermicity of polyester resins because of dilution effects. For low‐profile additives such as poly(vinyl acetate) and polyurethane, which are “quite” compatible with polyesters before cure, the overall reaction rates of the resins are substantially enhanced over those of less compatible additives. However, the ultimate conversion of low‐profile polyesters is found to be slightly greater than that of neat polyester, in most cases.
Thermal properties of nickel powder filled polypropylene composites
Authors: Maiti S. N. , Mahapatro P. K.
Published: May 2005

The thermal properties of nickel powder filled polypropylene composites were measured over a range of filler concentrations. The thermal conductivities increased with filler concentration. Data were compared with predictions by theoretical models for two phase systems. The equation of Cheng‐Vachon gave reasonable agreement with measurements. A TGA (thermogravimetric) study of the composites showed that the presence of nickel powder increases the thermal stability of polymer through an increase in activation energy to a maximum at a critical filler concentration, beyond which the stability decreased. The Vicat softening point of the composites was also increased in the presence of Ni powder.
Assessment of fiber arrangement and contiguity in composite materials by image analysis
Authors: Wimolkiatisak Angel S. , Bell James P. , Scola Daniel A. , Chang Jemei
Published: May 2005

The overall objective of this research was to correlate the processing—fiber arrangement—properties relationships of composites. In order to do this, an experimental technique to quantitatively characterize the fiber arrangement was developed. Using this technique, the compression molded graphite/epoxy composites, CMC, were found to have a standard deviation of fiber spacing of about twice the value of those from the simulated random composites, SRC. The standard deviation of fiber volume fraction for CMC was about 4 times the value of SRC. In other words, the fibers in this laboratory CMC were poorly distributed relative to SRC.
Friction and wear behavior of graphite fiber‐reinforced composites
Authors: Shim Hyun H. , Kwon Oh K. , Youn Jae R.
Published: May 2005

Friction and wear behavior of continuous graphite fiber composites was studied for different fiber orientations against the sliding direction. The effect of fiber orientation on friction and wear of the composite and on deformation of the counterface was investigated experimentally. A pin on disk type testing machine was built and employed to generate friction and wear data. A graphite fiber composite plate was produced by the bleeder ply molding in an autoclave and machined into rectangular pin specimens with specific fiber orientations, i.e., normal, transverse, and longitudinal directions. Three different wear conditions were employed for two different periods of time, 24 and 48 hours. The wear track of the worn specimens and the metal counterface was examined and a scanning electron microscope (SEM) to observe the damaged fibers on the sliding surface of the specimen and wear film generation on the counterface. A wear mechanism of the continuous graphite fiber composite during sliding wear is proposed based on the experimental results.
A method for studying damage in a fiber reinforced thermoplastic by masking viscoelastic effects
Authors: Tonda R. D.
Published: May 2005

A technique and some preliminary results of a study of the damage state of a long fiber reinforced thermoplastic composite are presented, emphasizing the difficulty encountered when the matrix material contributes significant viscoelastic effects to the material response. The type and origin of these effects are reviewed, as is the theory that has been developed allowing for removal of the superimposed viscoelastic effects. It is demonstrated that the complicating effect of the superimposed viscoelasticity can be successfully removed, thereby providing a less confusing presentation of the data and offering the potential for greatly simplified design and analysis.
Bioabsorbable composites. I: Fundamental design considerations using free radically crosslinkable matrices
Authors: Storey Robson F. , Wiggins Jeffrey S. , Mauritz Kenneth A. , Puckett Aaron D.
Published: May 2005

Bioabsorbable composites have been fabricated, consisting of poly (glycolic acid) surgical mesh embedded in free radically crosslinked poly (D, Iactide‐co‐8‐caprolactone) fumarate‐ or poly(D, Iactide‐co‐‐glycolic acid) fumarate‐based matrices. Styrene and methyl methacrlate were investigated as hydrophobic comonomers and were found to significantly improve the degree of crosslinking, tensile strength and retention of physical properties during the initial stages of degradation particularly styrene. Hydrolytic degradation studies showed that the neat poly(D, L‐lactide‐co‐8caprolactone) fumarate matrix dwas excessively hydrophilic, failing after 10 days of immersion; a matrix modified with 25 wt% styrene underwent a steady, nearly linear loss in mass over a period of 35 days without fragmentation. A composite based on neat poly (D, L‐lactide‐co‐8‐caprolactone) fumarate displayed a tensile strength of 37 Mpa and modulus of 107 Mpa; addition of 25 wt% styrene yielded tensile strength and modulus of 64 Mpa and 689 Mpa, respectively. A silane coupling agent was shown to dramatically improve the fiber‐matrix interfacial adhesion; tensile strength of a poly(D, L‐lactide‐co‐glycolic acid) fumarate compsite was increase from 84 to 92 MPa upon fiber pretreatment. Improved adhesion was also demonstrated using SEM. Bioabsorbable composites are rigid at biological temperatures, but some can be custom formed at elevated temperatures, which might be useful in certain surgical applications.
Effect of catalyst concentrations on one‐shot polyether flexible urethane foams
Authors: Sandridge R. L. , Gemeinhardt P. G. , Saunders J. H.
Published: May 2005

Variations were made in the concentration of tin and amine catalysts used in a typical one‐short polyether flexible foam system. Differences in foaming characteristics and foam stability were correlated with the relative rates of the chemical reactions which are believed to occur during the foaming process. Physical properties measured on the samples showed in many cases a dependence on the balance between the tin and amine catalysts.
Further basic and experimental developments on heterophase polymer materials
Authors: Kronstein Max
Published: May 2005

Basic considerations are presented for the formation of three‐dimensional or “polymer” units from the conglomeration of freely moving reactive molecules. The resulting “heterophase” conditions are shown between these swelling units and the not‐polymerized fluid matter. Systematic variations of the ratio of the phases and changes in material are discussed.
The reinforcement of epoxy resins with potassium titanate whiskers
Authors: Mallick P. K. , Broutman L. J.
Published: May 2005

Fybex is a newly available potassium titanate whisker. Its usefulness as a reinforcement for a thermosetting epoxy resin is examined. The effect of surface treatment on the mechanical properties of the composite system is also considered.
Elastic moduli of highly oriented polyoxymethylene
Authors: Choy C. L. , Leung W. P. , Huang C. W.
Published: May 2005

The five independent elastic moduli C11, C12, C13, C33, and C44 for uniaxially drawn polyoxymethylene with draw ratio λ = 1‐16 have been measured from −60 to 120°C by an ultrasonic method at 10 MHz. Wide angle x‐ray diffraction and birefringence measurements indicate that the chains in the crystalline regions are fully aligned at λ = 5 but the degree of amorphous orientation increases steadily up to the highest draw ratio. Below the major amorphous γ relaxation (∼0°C at 10 MHz), only the axial longitudinal and tensile modulus, C33 and E0, show large increases. At 120°C, however, all the moduli increase with λ, with E0, E90 (transverse tensile modulus), C44 (axial shear modulus) and C66 (transverse shear modulus) increasing 10, 2.5, 3, and 2.5 times, respectively, as λ rises from 1 to 16. This improvement in mechanical properties may be attributed largely to the effect of taut tie‐molecules and crystalline bridges. Whereas the two‐parameter model of Seferis seems to be valid only below the γ relaxation, the Halpin‐Tsai equation can give a reasonable description of the mechanical behavior for the highly oriented samples (λ>5) over the entire temperature range.
Contrast enhanced photoresists—processing and modeling
Authors: Griffing B. F. , West P. R.
Published: May 2005

This paper will describe a new concept for the production of high contrast photopatterns. The method is designed to produce good quality patterns with very low contrast illumination through the use of photobleachable materials in conjunction with standard photoresists. A very thin bleachable layer is first applied to the photoresist surface. Following conventional exposure, the layer is removed and the resist developed in the ordinary way. As a result of the presence of the bleachable material, the contrast of the illumination that reaches the photoresist is increased. It is for this reason that the technique is called contrast enhancement. The degree to which the contrast is enhanced depends on both the photochemical properties of the bleachable material and the dose required to expose the underlying resist. The paper will discuss properties required of the bleachable material in order to make the technique feasible, such as the magnitudes of the extinction coefficient and the quantum yield. Bleaching experiments on candidate materials for the characterization of these parameters will be described. Also to be discussed is a model of the bleaching dynamics, which was used to calculate the improvements in contrast that are achieved as a function of base resist sensitivity. The extra processing steps required by the presence of the bleachable layer will be covered. Submicron resist patterns that demonstrate the resulting improvement in contrast will also be shown.
Effect of varying the composition of copolymers of glycidyl methacrylate and 3‐chlorostyrene (GMC) on electron lithographic performance
Authors: Novembre A. E. , Bowden M. J.
Published: May 2005

The polymerization kinetics, molecular parameters, and electron lithographic response of a series of copolymers of glycidyl methacrylate (GMA) and 3‐chlorostyrene (CLS) have been determined. The polymerization rate, molecular weight, and polydispersity decrease with increasing mole fraction of 3‐chlorostyrene (XCLS). Similarly, the sensitivity of this system decreases as the percentage of CLS in the copolymer increases. The value of D for the copolymer containing 14.3 mole percent CLS is 0.45 μC/cm2 increasing to 3.2 μC/cm2 for the 54 percent CLS copolymer of equivalent molecular weight. On the contrary the wet air and O2 plasma etch rates decrease as XCLS increases. For example, the etch rate using wet air for PGMA is ∼ 30 percent greater than GMC (XCLS = 0.54). The post exposure polymerization rate decreases as the CLS content increases. The extent of the post cure reaction is dose dependent being a maximum at D = 0.64 μC/cm2 for the copolymer containing 14.3 mole percent CLS.
Stress and displacement fields at the tip of a craze containing a crack
Authors: Warren William E.
Published: May 2005

Plane elasticity theory is utilized to obtain expressions for the stress and displacement fields at the tip of a craze containing a crack. The craze is modeled as a very thin elliptical inclusion with different elastic properties from hat of the surrounding bulk polymer. Problem is solved by superimposing the solution of a crack problem onto the solution for a uniformly loaded homogeneous craze. Invoking stress free boundary conditions on the crack surface provides a singular integral equation of Hilbert type with a unique solution. Contour lines of constant hydrostatic stress and constant maximum shear stress around the craze tip are shown graphically. These two stress combinations have played prominent roles in a number of proposed craze growth criteria. Results show that even for relatively long cracks within the craze, very little stress enhancement at the craze tip occurs. Only as the crack tip approaches the craze tip does the enhancement become significant, tending to drive the craze region ahead of the crack.
Relaxation induced changes in electrical behavior of glassy chalcogenide semiconductors
Authors: Abkowitz M.
Published: May 2005

Effects of structural relaxation and the glass‐transition process are clearly manifested in the electrical behavior of glassy‐chalcogenide films. Analysis of the transport and trapping of photoinjected carriers and of the thermal generation of free carriers in the bulk reveal that in chalcogenides each of these processes is mediated by a specific manifold of localized electronic states residing in the mobility (forbidden) gap. It is demonstrated that in the vicinity of Tg the population of these states varies systematically with the structural state of the glassy film always tending toward a temperature‐dependent quasi‐equilibrium. The present‐observations thus clearly establish the structural origin of key electronic‐gap states and simultaneously reveal the mechanism by which relaxation impacts electrical behavior.
Dynamic and steady‐state rheological properties of linear‐low‐density polyethylene melt
Authors: Saini D. R. , Shenoy A. V.
Published: May 2005

Linear‐low‐density polyethylene (LLDPE) is steadily gaining importance in a wide variety of applications due to its excellent performance characteristics in the final product. The rheological properties of LLDPE in the dynamic and steady state are of great pragmatic importance and these have been studied in the present work. A correlation between the dynamic and steady‐state rheological properties has been attempted and good agreement has been found.