bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ultrasound devulcanization of unfilled natural rubber networks, studied via component molecular mobility
Authors: Massey Joseph L , Parr Jennifer C , Wagler Todd A , von Meerwall Ernst , Hong Chang K , Isayev Avraam I 
Published: April 2007

Abstract13C NMR solids spectroscopy and transverse relaxation, and 1H relaxation and pulsed‐gradient spin‐echo self‐diffusion measurements at 70 °C were used to study molecular and segmental mobilities in natural rubber before and after sulfur crosslinking, and after subsequent devulcanization using intense ultrasound. NMR relaxation does not clearly distinguish between entangled and crosslinked network mobility, but unentangled sol and oligomeric species are separable within the longer T2 decay components. Ultrasound reactor settings affect the amount of extractable sol generated. Some two‐thirds of the sol is entangled, with number‐average molecular weights (Mn) above 10 000 g mol−1. Samples also contain near 2 wt% of inert light species (Mn < 400 g mol−1); ultrasound is relatively ineffective in producing additional oligomeric material. All proton mobilities increase as more sol is produced, but 13C relaxation, reflecting intramolecular effects, indicates a slight decrease in backbone mobility. In contrast with other rubbers, in natural rubber, neither the glass transition nor the sol diffusion rate is greatly affected by the extent of ultrasound exposure. Comparisons with previous similar work of this laboratory, particularly styrene‐butadiene rubber, are useful in confirming the molecular mechanisms involved. Copyright © 2007 Society of Chemical Industry
Transforming polymer blends into composites: a pathway towards nanostructured materials
Authors: Denchev Zlatan Z , Dencheva Nadya V 
Published: April 2007

AbstractPolymer blends and polymer‐based composites are two of the most rapidly developing groups of materials being of industrial, as well as of academic, interest. More than a decade ago a new group of polymer materials was introduced, which became known under the name ‘microfibrilar composites’ (MFCs). They were obtained by the transformation of blends of thermoplastic polymers into micro‐ or nanostructured systems by combination of appropriate mechanical and thermal treatments. Since then, the importance of these novel materials, both for theory and for engineering practice, has increased significantly. It is an objective of this review to outline the place of MFCs within the whole variety of polymer‐based composites. Furthermore, the methods of their preparation, the ways of investigating their structure and the relation of the structure and mechanical properties are discussed. Ultimately, an evaluation of the future trends in this exiting interdisciplinary research field is attempted. Copyright © 2007 Society of Chemical Industry
The characterisation of dope dyed poly (ethylene terephthalate)
Authors: Uglea Constantin V. , Stan Viorica N. 
Published: April 2007

AbstractBy analysing the polycondensation of ethylene glycol with dimethyl terephthalate, the influence of 1,4‐aminoanthraquinone dyestuffs on the chemical and molecular properties of dope dyed poly(ethylene terephthalate) has been determined. The results show that dope dyed poly(ethylene terephthalate) differs from the uncoloured polymer by a possession of a higher amount of ‐COOH end groups and diethylene glycol units. The shape and the position of molecular weight distribution curves determined by gel permeation chromatography are also influenced by the soluble dyestuffs used.
Friedal‐craft polymers in electrical applications. (I) Synthesis and evaluation of polymers based on terphenyls and p‐xylylene glycol dime thyl ether
Authors: Paxton J. C. , Tighe B. J. 
Published: April 2007

AbstractThe design and evaluation of Friedel‐Crafts polymers as electrical insulants is discussed with particular reference to materials based on p‐xylylene glycol dimethyl ether and terphenyl. The general synthetic procedure for these applications normally consists of two idealised stages. The first involves the formation of a soluble, linear or branched polymer. The second consists of its conversion, sometimes after isolation and compounding operations, to a cross‐linked material at a controllable rate in a moulding or film‐forming reaction.A variety of catalysts and reaction conditions were examined, of which SnC14 and the so‐called ball clays (a range of kaolin‐based minerals varying in acidity and iron content) proved to be the most interesting. The structures of the polymers at various stages of the reaction leading to the final cross‐linked product are discussed together with the properties of the resultant materials.
Photoconductivity and photovoltaism in polyvinylcarbazole membranes
Authors: Jones Eurfyl Glynne , Read Gordon 
Published: April 2007

AbstractThe preparation and photo‐electrical properties of free standing water impermeable membranes of polyvinylcarbazole (PVCa) are described. The membranes, with aqueous electrolyte contacts, show ohmic photoconduction when doped with crystal violet (CV) and irradiated with light of wavelengths > 475 nm. Optimum levels of doping, which approach one dye molecule per molecule of polymer, give photocurrent/dark current ratios of 106 with light levels of 175 mW cm−2. On open circuit pH dependent photovoltages > 200 mV are obtained which produce photovoltaic currents > 10−10 A cm−2 under short circuit conditions.The influence of combinations of tetracyano‐o‐benzoquinone (TCOBQ) and CV is additive but, in contrast to reported findings at high voltage gradients, combinations of tetracyanoquinodimethane (TCNQ) and CV lower the efficiency of the photoconduction process by an order of magnitude. Action spectral studies relate this effect to a photoredox process at the electrolyte‐membrane interface associated with the absorption band at 410nm in TCNQ, and suggest domaines of TCNQ in the polymer.The role of the sensitiser in the transfer of electrons from the membrane to the electrolyte and across the membrane is discussed and the importance, for efficient electron transfer, of the spacial relationship between CV molecules and the stacked carbazole residues in the PVCa molecules is emphasised.
Studies of the antenna effect in polymer molecules V. Determination of the extent of singlet energy migration in a phenanthrene — Containing polymer by fluorescence quenching
Authors: Holden David A. , Ng Dominic , Guillet James E. 
Published: April 2007

AbstractA modification of a Stern‐Volmer fluorescence quenching experiment was used to determine the extent of singlet energy migration between phenanthrene chromophores in poly(9‐phenanthrylmethyl methacrylate). This system avoids the problems of nonexponential fluorescence decay, inhomogeneous quencher concentrations and complication by the formation of excimers. The contribution to the distance travelled by the singlet excitation during the excited state lifetime as a result of energy migration was shown to correspond to about a third of the distance diffused by an oxygen molecule during the same time.
Thermoplast/phenolic resin aqueous dispersions
Authors: Demmer Christopher G. , Garnish Edward W. , Massy D. James R. 
Published: April 2007

AbstractCombinations of phenolic resols with high molecular weight thermoplasts in the form of aqueous dispersions can be prepared by dissolving the thermoplast in the phenol and reacting with aqueous formaldehyde solution in the presence of emulsifiers. The scope of this procedure has been explored and the wide variety of thermoplasts that can be utilised is demonstrated. Several of the products from this process show promising results in metal‐bonding applications. Some of the physical and chemical changes taking place during the reaction and dispersion are described.
Determination of number‐average molecular weight of atactic polystyrene and cellulose diacetate by vapour pressure osmometry
Authors: Kamide Kenji , Terakawa Toshikazu , Matsuda Shigenobu 
Published: April 2007

AbstractThe usefulness of vapour pressure osmometry (v.p.o.) as a method for determining the number average molecular weight Mn was examined in comparison with other methods such as gel‐permeation chromatography (g.p.c.) and membrane osmoetry (m.o.). For this purpose, the weight‐ and number‐average molecular weights Mw and Mn were determined on well‐defined atactic polystyrene and cellulose acetate (degree of substitution DS = 2.46) samples. The experimental difference between Mn (v.p.o.) and Mn (g.p.c.) for any given sample are note significant at a 95 per cent level. The v.p.o. method were reproducible to ± 7–9 per cent or better, being useful in Mn range 2–12×104.
Conformational transition in PMMA. Methyl isobutyl ketone
Authors: Katime I. , Pereg M. Garay 
Published: April 2007

AbstractIn this work we have studied the viscometric behaviour of several fractions of PMMA in methyl isobutyl ketone as a function of temperature. A conformational transition has been found in the temperature range 25–35°C.Likewise, the influence of solvent nature on the magnitude of the conformational transition has been studied.
Lignins as formulating agents for controlled release in agriculture
Authors: Wilkins Richard M. 
Published: April 2007

AbstractThe use of naturally‐occurring polymers, and in particular, kraft lignin, for controlled release pesticide formulations is reviewed. A matrix of kraft lignin containing polar pesticides can be prepared in granular form and the release rates of the active ingredient from this formulation are described. Successful applications of this type of formulation include herbicides for weed control in conifer plantation and insecticides in tropical flooded rice.
Studies in heterocyclic polymers, Pt VIII the preparation of o‐cyanobenzoic acid and some derivatives
Authors: Hodd Kenneth A. , Shadbolt Phillip 
Published: April 2007

AbstractIn a study of the synthesis of polyiminoimides the preparation of 2‐cyano‐benzoic acid (VI) and some derivatives has been examined. Both the symmetrical (XII) and the asymmetrical (XIII) phthaloyl dichlorides were found to give good yields of (VI) upon ammonolysis with (XII) the more efficient precursor. Conversion of the acid (VI) to its acid chloride (IX) was readily effected with PCl5. A number of substituted 2‐cyanobenzanilides were prepared from (IX) and their cyclisation to the related 2‐substituted‐3‐iminoisoindolinones studied using DSC. The nature of the substituent appeared to have little influence upon the rate of cyclisation which occurred spontaneously upon melting the parent anilide.The synthesis of mixed dicyanodicarboxylic acids from pyromellitic dianhydride and from benzophenone — 3,3′,4,4‐tetracarboxylic acid dianhydride was also studied but difficulties were encountered in resolving the products.
Characterisation of a bisphenol a epoxy resin. A collaborative study carried out by technical panel PTP3 of the technical cooperation programme
Authors: Wright W. William 
Published: April 2007

AbstractA collaborative study has been made by a number of laboratories of samples of nominally the same bisphenol A epoxy resin prepared in different countries and its cure with diaminodiphenylsulphone. A variety of techniques have been used to characterise the resin samples and their relative value for structural analysis and specification purposes assessed. Physical and mechanical properties of cured cast resin samples have also been measured and related to the resin structures observed. The study shows that some of the techniques do indicate differences in resin composition, but that these were not reflected in differences in mechanical properties.
13C N.m.r. Spectra of ring‐opened polymers of 1‐methylbicyclo[2.2.1]hept‐2‐ene and their hydrogenated products
Authors: Hamilton James G. , Ivin Kenneth J. , Rooney John J. 
Published: April 2007

AbstractThe 13C n.m.r. spectra of the title polymers have been completely assigned for a comprehensive range of cis contents (σc = 0–1) and head‐tail bias (HT/(HH + TT) = 1 −∞). In the unsaturated polymers (II), cis HH dyads are never found, so that all‐cis polymers are also all‐Ht, but cis TT dyads are formed in cis‐trans polymers, equal to the difference between trans HH and trans TT. The olefinic region consists of seven triplets; two each from cis HT and trans HT, and one each from cis TT, trans TT and trans HH. In the case of trans each triplet consists of a main centre peak due to ttt and ctc sequences and two wing peaks due to ttc and ctt sequences, as defined in the text. The upfield peaks also show cc/ct or tt/tc splittings as well as HH/HT or TT/TH splittings in most cases. In the saturated polymers C6 is sensitive to m/r ring dyad sequences. A corrected assignment is given for the hydrogenated polymer of norbornene.
Effects of fillers on and the role of hydrogen chloride in the behaviour of PVC in fires
Authors: Matthews George , Plemper George S. 
Published: April 2007

AbstractCalcium carbonate fillers react with hydrogen chloride liberated during pyrolysis of PVC to an extent depending on their particle sizes and concentrations. The effects of these and other fillers on the critical oxygen index is more complex and depends on a number of factors additional to the extent of hydrogen chloride retention, of which char formation in particular is not readily assessed numerically. Differential thermal analyses suggest that the reaction of hydrogen chloride with calcium carbonate or calcium oxide fillers proceeds rapidly upon liberation. Hydrogen chloride added to the gas stream raises the critical oxygen index to a considerably greater extent than do carbon dioxide or nitrogen. It is concluded that the exotherm due to reaction between calcium carbonate fillers and pyrolysis hydrogen chloride contributes only slightly to flammability, and that the involvement of hydrogen chloride in reducing flammability is chemical rather than physical.
Synthesis and micellar behaviour of some novel amphiphilic acrylate and methacrylate monomers
Authors: Hamid Shakeeb M. , Sherrington David C. 
Published: April 2007

AbstractThe syntheses of a number of acrylate and methacrylate based amphiphiles are described. One group consists essentially of quaternary ammonium salts and the other of potassium carboxylates. Two non‐ionic species based on oligoethylene oxides are also described. The critical micelle concentration of each has been determined from conductance and dye absorption data, and the values compare satisfactorily with literature data on similar non‐polymerisable molecules. The compounds readily oligomerised in bulk, and in the micellar state the dye absorption data also indicated oligomerisation initiated by a free radical source.
The tacticity of poly(tri‐n‐butyl tin methacrylate) determined by 13C n.m.r.
Authors: Dambatta Bello B. , Ebdon John R. 
Published: April 2007

AbstractThe tacticities of poly(tri‐n‐butyl tin methacrylate)s prepared with radical initiators at various temperatures have been measured by 13C n.m.r. As expected, the polymers are predominantly syndiotactic and this syndiotacticity decreases with an increase in temperature. The activation parameters governing the tacticity are similar to those published for poly(methyl methacrylate) but differ somewhat from values published for poly(trimethyl tin methacrylate).
Studies of polycarbonate — poly (butylene terephthalate) blends
Authors: Birley Arthur W. , Chen Xin Yue 
Published: April 2007

AbstractThe composition and microstructure of a blend of bisphenol‐A polycarbonate (PC) and poly (butylene terephthalate) (PBT) have been established by a variety of physical methods. The composition was established by solvent extraction and infra‐red spectrophotometry, while the microstructure was determined by these and the additional methods of differential scanning calorimetry and dynamic mechanical thermal analysis. The PBT retained its crystallinity in the commercial blend, (Xenoy CL‐100), but blending reduced the main glass‐rubber transition of the PC from 147°C to approximately 100°C. Conditioning of the blend at high temperatures resulted in progressive transesterification: 3 minutes at 240°C gave a small but significant effect, while 30 minutes at 270°C yielded large changes in the structure. These findings are important in respect of processing the material, and the limitations which might be incurred in plant recycling of scrap.
Studies on the photopolymerisation of vinyl monomers using amine‐organic halide systems as initiators
Authors: Pramanick Dinabandhu , Bhattacharyya Ramanath 
Published: April 2007

AbstractAmine‐organic halide systems have been found to be good photo‐initiators for the polymerisation of vinyl monomers in a benzene medium. The n‐tertiary butylamine‐carbonte‐trachloride (TBA‐CC14) system is most suitable for the polymerisation of methyl meth‐acrylate (MMA) in the presence of light. The rate of polymerisation (Rp) and degree of polymerisation (P̄n) are found to be independent of incident light intensity (Io). Rp and 1/P̄n are linearly related to [TBA]0.5 up to [TBA] = 0.108M, but above this concentration, TBA acts predominantly as a retarder. Rp and 1/P̄n are proportional to [CC14]0.5 at low [CC14]. At [CC14] > 0.099M it acts predominantly as a transfer agent. Furthermore, Rp is always proportional to [MMA]1.0 Endgroup analysis by dye‐partition test shows that both amine bearing radicals and CC13 radicals are the initiating species and an average of about one total endgroup per polymer molecule up to [CC14] = 0.099M indicates bimolecular termination of the poly (MMA) radicals through disproportionation. Higher chlorine endgroup and total endgroup incorporation at [CC14] > 0.099M gives additional evidence of the preponderance of chain transfer under this condition. A suitable mechanism of polymerisation is suggested, based on kinetics and endgroup evidence.
A chemical demonstration of the randomness of epoxidation of natural rubber
Authors: Davey John E. , Loadman M. John R. 
Published: April 2007

AbstractDuring the development of chemical methods for determining the epoxide content of epoxidised natural rubber (ENR) two methods were found to give results which were identical but which showed a progressive divergence from values obtained by absolute instrumental methods as the level of epoxidation increased.Statistical analysis of the sequence distribution of the epoxide groups, based on a random epoxidation, showed a good correlation between the value obtained by chemical analysis and the number of epoxide blocks rather than the number of epoxide groups.Two further instrumental methods for measuring the total epoxide content, using infra red spectroscopy and differential scanning calorimetry, were developed. Analytical procedures and calibration data are supplied.A combination of one chemical and one instrumental method can thus provide the absolute level of epoxidation and indicate whether the reaction has proceeded randomly or not, a point of crucial importance in the large scale manufacture of this material.
Matrix polymerisation of vinyl acetate in the presence of molecular sieves
Authors: Bezdade Mariana , Cascaval C. N. 
Published: April 2007

AbstractPolymerisation of vinyl acetate in the presence of some molecular sieves, Sephadex and CaX type Zeolite, led, in well defined experimental conditions, to polymers with a regular structure. Evidence of the role of molecular sieves as a matrix for stereoregular polymerisation was provided by n.m.r. spectra and scanning electron microscopy, while the pyrolysis‐ gas chromatography and elemental analysis have pointed out the separation of polymer from matrix. The experimental data obtained on polymerisation of vinyl acetate in the presence of molecular sieves allowed us to postulate the presence of a donor‐acceptor type reaction mechanism.
Lack of statistical significance
Authors: Kehle Thomas J. , Bray Melissa A. , Chafouleas Sandra M. , Kawano Takuji 
Published: April 2007

AbstractCriticism has been leveled against the use of statistical significance testing (SST) in many disciplines. However, the field of school psychology has been largely devoid of critiques of SST. Inspection of the primary journals in school psychology indicated numerous examples of SST with nonrandom samples and/or samples of convenience. In this article we present an argument against SST and its consequent p values in favor of the use of confidence intervals and effect sizes. Further, we present instances of common errors that impede cumulative knowledge in the literature related to school psychology. © 2007 Wiley Periodicals, Inc. Psychol Schs 44: 417–422, 2007.
Effect sizes, confidence intervals, and confidence intervals for effect sizes
Authors: Thompson Bruce 
Published: April 2007

AbstractThe present article provides a primer on (a) effect sizes, (b) confidence intervals, and (c) confidence intervals for effect sizes. Additionally, various admonitions for reformed statistical practice are presented. For example, a very important implication of the realization that there are dozens of effect size statistics is that authors must explicitly tell readers what effect sizes they are reporting. With respect to confidence intervals, when interpreting a 95% interval, we should never say that we are 95% confident that our interval captures the estimated population parameter. It is explained that effect sizes should be reported even for statistically nonsignificant effects. And, most importantly of all, it is emphasized that effect sizes should not be interpreted using Cohen's benchmarks. Instead, we ought to interpret our effects in direct and explicit comparison against the effects in the related prior literature. © 2007 Wiley Periodicals, Inc. Psychol Schs 44: 423–432, 2007.
RNASEL Arg462Gln polymorphism and prostate cancer in PLCO
Authors: Daugherty Sarah E. , Hayes Richard B. , Yeager Meredith , Andriole Gerald L. , Chatterjee Nilanjan , Huang Wen‐Yi , Isaacs William B. , Platz Elizabeth A. 
Published: April 2007

AbstractBACKGROUNDThe Gln allele of the Arg462Gln polymorphism in RNASEL results in a threefold decrease in enzymatic activity, a reported deficiency in apoptotic response, and has been associated with prostate cancer in some high‐risk family studies. The relationship of this variant to sporadic prostate cancer remains uncertain.METHODSWe conducted a nested case‐control study of 1,317 prostate cancer cases and 1,842 controls from the screening arm of the prostate, lung, colorectal, and ovarian (PLCO) cancer screening trial. Conditional logistic regression was used to evaluate the association between the RNASEL Arg462Gln polymorphism and prostate cancer.RESULTSNo statistically significant association was observed between the Arg462Gln polymorphism and prostate cancer (compared to Arg/Arg, Gln/Arg: OR= 0.99 95% CI 0.84–1.16; Gln/Gln: OR= 0.95 95% CI 0.74–1.21), although slight non‐significant differences in risk were observed among men with the Gln/Gln genotype by stage and grade.CONCLUSIONSThese results suggest that the RNASEL Gln/Gln genotype does not play an important role in the etiology of prostate cancer in the general population. Prostate 67: 849–854, 2007. Published 2007 Wiley‐Liss, Inc.