bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies of linear polymer dimensions of poly(4‐chlorostyrene) in various solvents around the θ temperatures by intrinsic viscosity
Authors: Baysal Bahattin M. , Yilmaz Ferdane 
Published: April 2007

AbstractIntrinsic viscosities of poly(4‐chlorostyrene) solutions in isopropyl‐benzene and n‐propylbenzene at temperatures above and below the theta (θ) temperatures of these solvents were measured using a capillary viscometer. The viscosity measurements were performed on three poly(4‐chlorostyrene) samples having molecular weights (M̄;v) 1.75 × 106, 6.5 × 105 and 2.7 × 105. A smooth and continuous contraction below the θ temperatures was observed for both solvents. The temperature dependence of [/eta] can be represented by a master curve in a plot of α3/eta|/tau|M1/2 (g1/2 mol−1/2) versus |/tau|M1/2 (g1/2 mol−1/2), where α/eta = [/eta(T)]/[/eta(θ)]1/3 is the expansion factor and /tau = (T ‐ θ)/T is the reduced temperature. A universal plot of reduced viscosity size (α/eta) versus reduced blob parameter (N/Nc) shows the achievement of collapsed state for T<θ. The prediction of thermal blob theory is also verified for T > θ. The temperature dependence of intrinsic viscosity, both below and above the θ temperature, exhibits similar behaviour to the temperature dependence of dipole moments for both of these solvents.
Structural change of cellulose contained in immature cotton boll during its growth
Authors: Matsuda Yukiko , Kowsaka Keisuke , Okajima Kunihiko , Kamide Kenji 
Published: April 2007

AbstractAn attempt was made to clarify the change in the structure of immature cotton (Gossypium spp.) boll during its growth. For this purpose, five immature cotton bolls with length less than 4.64 cm were adopted as samples and cellulose fibres taken from these bolls were subjected to SEM observation, 13C NMR, X‐ray diffraction and IR analysis. Intramolecular hydrogen bonds were progressively formed during the growth of first cell wall but crystallization did not occur at this stage. Crystallization, as detected by X‐ray diffraction, takes place after the formation of O3…O'5 and O2…O'6 intramolecular hydrogen bonds. The crystallization is well correlated with the formation of intermolecular hydrogen bonds, as detected by IR analysis. The conformational regularity of molecular chains (formation of intramolecular hydrogen bonds) is concluded to be prerequisite for the crystallization of cotton fibre.
Synthesis of ring‐shaped polyisoprene
Authors: Madani Abdelaziz El , Favier Jean‐Claude , Hémery Patrick , Sigwalt Pierre 
Published: April 2007

AbstractCyclization of α,ω;‐dilithiopolyisoprenes has been achieved in hexane solution in the presence of tetrahydrofuran (15% in volume) at −40 to ‐ 50°C. Using as linking agent the non‐conjugated diene 1,2‐bis(isopropenyl‐4‐phenyl)‐ethane, macrocyclic polyisoprenes could be obtained with yields of at least 90%, even for molecular weights as high as 30 000 mol g−1. With SiCl4 as coupling agent no gelation occurred and yields of about 70% in cyclic dimers, probably bicyclic, have been observed.These results are compared to those obtained by various authors with α,ω;‐dilithiopolystyrenes or α,ω;‐disodiopolystyrenes and are attributed mainly to the presence, in the polyisoprene case, of predominant cyclic aggregates even at low organolithium concentration.
Modification of kaolinite by surface polymerization
Authors: Laslett Robert L. , Wansbrough Katherine M. , Mainwaring David E. , Rizzardo Ezio , Singh Sirgit 
Published: April 2007

AbstractKaolinite filler surfaces were modified by both surface adsorption and surface reaction. Their subsequent wetting and adhesion properties were determined by measurement of the contact angle of the powders by the Washburn technique using three probe liquids that spanned molecular polarity. Surface modification by adsorption utilized the kaolinite surface acidity to polymerize styrene. Surface reaction involved reaction of kaolinite hydroxyl groups with aryl diisocyanates and subsequent termination with a series of alcohols of increasing complexity.It was shown that kaolinite surfaces could be modified to produce surfaces of controlled hydrophobicity that could exceed that of conventionally silanated kaolinite. The ability of phases to spread and wet these filler surfaces was analysed in terms of the thermodynamic functions—spreading coefficient S12 and spreading pressure πe.
Photodegradable high density polyethylene‐based shopping bags— environmental hazard or blessing?
Authors: Ferguson Grant M. , Hood Mark , Abbott Kerry 
Published: April 2007

AbstractPlastics are popularly regarded as an environmental hazard. Ferric stearate photoinitiated high density polyethylene (HDPE) films manufactured as supermarket shopping bags were found to rapidly photodegrade after exposure to ultraviolet (UV) and visible light irradiation. Our studies confirmed manufacturer's claims that the bags would degrade more rapidly than standard UV stabilised bags. The photodegradable bags had the potential to completely degrade and be resorbed into the biosphere without adverse effects.
Effect of lewis acids on cure kinetics and mechanical properties of hydroxyterminated polybutadiene polymers
Authors: Ninan K. N. , Krishnan K. 
Published: April 2007

AbstractThe effect of two Lewis acids, viz. BF3 and AlCl3 on the cure reaction of hydroxy‐terminated polybutadiene: toluene diisocyanate systems has been studied in order to evaluate them as possible pot‐life extenders in solid propellant formulations. The enthalpy of the cure exotherm, evaluated from DSC curves, did not show any dependence on the concentration of the two acids. The kinetic parameters for the cure reaction showed an increase in both cases indicating the effectiveness of the acids as reaction retardants. However, BF3 is not a suitable candidate for pot‐life extension, because of its adverse effect on the elongation at break of the cured HTPB samples. The coefficient of thermal expansion is unaffected by the two additives, probably because of their negligible influence on the cross‐link density of the cured network.
Phenol novolac/poly(4‐ hydroxyphenylmaleimide) blend hardeners for DGEBA‐type epoxy resin
Authors: Matsumoto Akihiro , Hasegawa Kiichi , Fukuda Akinori 
Published: April 2007

AbstractPhenol novolac/poly (4‐hydroxyphenylmaleimide) (PHPMI) blends were used as an epoxy resin hardener. The curing behavior of the above system and the thermal and mechanical properties of the cured epoxy resin were studied. It was not necessary to use a curing accelerator for this system, because PHPMI caused acceleration of the curing reaction. The curing mechanism of this system was investigated by using model compounds. Test pieces from the neat resins and the glass fiber reinforced resins were evaluated in terms of thermal and mechanical properties, respectively. It was found that heat resistance and mechanical properties were improved by increasing the amount of PHPMI in the hardener.
Curing studies on vinyl ester resin using acrylates as reactive diluents
Authors: Kant Krishna , Mishra A. , Rai J. S. P. 
Published: April 2007

AbstractThe curing behavior of bis(methacryloxy) derivatives of diglycidyl ether of bisphenol A (vinyl ester resin) containing acrylates (methyl, ethyl and butyl acrylate) as the reactive diluents (40% w/w) were studied by DSC analysis. Data found in this study indicated that an appreciable curing rate is obtained at lower temperature with increased concentrations of initiator. The acid value, activation energy, Arrhenius factor and specific heat are discussed.
Poly(4‐methylstyrene‐co‐chloromethylstyrene): A negative electron beam resist—synthesis and lithography evaluation
Authors: Affrossman Stanley , Bakshaee Massoud , Bramley David , Chow Fong , Dix Christopher , Hendy Paul , Jones Mervyn , Ledwith Anthony , Mills Margaret , Tate Phillip Miller , Pethrick Richard A. 
Published: April 2007

AbstractSynthesis and lithographic characterization of a series of negative acting electron sensitive resists based on poly(4‐methylstyrene‐co‐chloromethylstyrene) are reported. The sensitivity and contrast of these resists were found to depend on the chloromethylstyrene (CMS) content and an optimum value of 5 wt% was determined from consideration of parameters associated with the reproducibility of the synthetic method and also the lithographic performance. Both the sensitivity and resolution were found to depend on the molecular weight and CMS content of the copolymer. Several methods of scale up for the synthesis were explored, the route having a very significant influence on the film formation characteristics of the resists. The reactivity ratios of the monomers were measured in order that the compositional drift, which occurs during the synthesis, could be quantified. The effect of solvent composition and molecular weight of the copolymer were explored in relation to the quality of the resulting lithography. These studies have indicated that the copolymer has the potential of being used as a VLSI sub‐micron resist with good plasma etch resistance.
Ionomer interpenetrating polymer networks from polyurethane anionomers and polyurethane isocyanurate
Authors: Ai‐Salah Hasan A. , Xiao Han X. , McLean John A. , Frisch Kurt C. 
Published: April 2007

AbstractTwo‐component interpenetrating polymer network (IPN) systems composed from polyurethane isocyanurate and polyurethane anionomer were prepared by simultaneous polymerization and crosslinking in solution. Specific attractive forces that occurred among various networks helped to make them compatible and led to the formation of true homogeneous topologically interpenetrating polymer networks. These ionomer IPNs were characterized by means of stress‐strain properties, hardness, thermogravimetric analysis, density and conductivity. The morphology of the IPNs was studied by thermomechanical analysis and dynamic mechanical analysis.
Effect of synthesis conditions on properties of poly(N‐isopropylacrylamide) gels
Authors: Gehrke Stevin H. , Palasis Maria , Akhtar M. Kamal 
Published: April 2007

AbstractProperties of poly(N‐isopropylacrylamide) gels—equilibrium degree of swelling, shear modulus, effective crosslink density and clarity—depend significantly upon the conditions of synthesis. While it is well known that monomer and crosslinker concentrations affect gel properties, other variables are shown here to have significant effects on the properties of the resulting gels. Initiator type and concentration, synthesis temperature, mold geometry and polymerization time all significantly affect the properties, including the swelling degree. Evidence suggests that the microstructure of these gels is particularly sensitive to these variables.
Micellar polymerisation of ionic surfactants studied by conductimetry
Authors: Tribet C. , Gaboriaud R. , Lelievre J. 
Published: April 2007

AbstractThe micellar polymerisation of ionic surfactants such as allyldodecyl‐dimethylammonium bromide and 3‐dodecyl‐1‐vinyl imidazolium iodide has been studied by conductimetry in aqueous solution. The polymerisation was carried out using two different sources of γ rays directed into solutions of surfactant above the critical micellar concentration. Conductimetry is shown to be a very good physicochemical method for analysis of these solutions. The results showed different behaviour for the two surfactants, which has highlighted a change in the structure of their aggregates which led to the assumption of an interaction between the polymers of high mass and different products of the polymerisation (oligomers, products of degradation, monomers etc.). Ultrafiltration experiments coupled with 1H‐NMR and conductivity analysis confirm these assumptions.
Mechanical changes of electron beam irradiated ethylene–vinyl acetate copolymer (EVA) film (I)
Authors: Matsui Toshiro , Shimoda Mitsuya , Osajima Yutaka 
Published: April 2007

AbstractElectron beam irradiation of ethylene‐vinyl acetate copolymer (EVA) film results in a marked depression of sorption of flavour compounds. This effect is presumed to be brought about by radical reactions, following changes in the structure. The crosslinking density and gel fraction increased with irradiation dose, and the maximum percent gel reached 70% for 20 Mrad‐50g kg−1 EVA film, 35% for 20 Mrad‐95g kg−1 EVA film and 50% for 10 Mrad‐150g kg−1 EVA film.In calculating the ratio of scission to crosslinking events, it was found that EVA film is a polymer of the scission type. The degree of crystallinity, Xc decreased significantly with increasing irradiation dose in all irradiated films. For unirradiated films, Xc decreased with increase in vinyl acetate content, which suggests that crystalline regions of EVA film are primarily composed of ethylene units. Therefore, the scission reaction may predominantly take place in the crystalline region, resulting in the formation of methyl or end vinyl groups. This was supported by measuring the film density, peak melting temperature and stress at yield.
Dielectric and viscoelastic relaxations in poly(dicyclohexyl itaconate)
Authors: Díaz‐Calleja Ricardo , Gargallo Ligia , Radic Deodato 
Published: April 2007

AbstractThe relaxation spectrum of poly(dicyclohexyl itaconate) (PDCHI) was studied by dynamic mechanical, DC dielectric and thermally stimulated current measurements. Four relaxations, α, β, γ and δ, were obtained. The only method by which all four peaks were observed is that of dynamic dielectric measurements because of the broad range of frequencies employed. The β, γ and δ relaxations were characterized by the activation energy in a relaxation map. A tentative explanation of the molecular origin of each absorption is proposed. In the case of the α relaxation we have used two transformations, one from the permittivity to polarizability and the second from compliance to deformability in order to make evident the existence of this relaxation.
Diffusion and permeation of gases in undrawn and radially drawn films of native and commercial gutta‐percha (trans‐Polyisoprene)
Authors: Arvanitoyannis Loannis , Heath Richard , Embeoglou Loannis 
Published: April 2007

AbstractThe permeability of native and commercial grades of gutta‐percha (trans‐polyisoprene), was determined and related to diffusion rate both below and above the glass transition temperature (Tg) and the melting point (Tm). Both radially drawn and undrawn membranes were evaluated. Five gases (O2, N2, CO2, H2 and He) were used as permeants and the measurements were taken both above and below the polymers' crystalline Tm. The diffusivity of the gases was found to have an increased rate above the Tm. The reduction of solubility, diffusivity and permeability with increasing draw ratio was attributed to an increase in crystallinity.
Control of intrinsic brittleness and toughness of polymers and blends by chemical structure: A review
Authors: Wu Souheng 
Published: April 2007

AbstractThe intrinsic brittle‐ductile (craze‐yield) behavior of polymers and blends are controlled by two chain parameters: entanglement density ve and characteristic ratio Cx. These chain parameters can be predicted from chemical structure. Therefore, the intrinsic brittle‐ductile behavior of polymers and blends can be controlled by chemical structure using group additivity. The chemical composition and chain structure which can give the ultimate toughness in polymers and blends are discussed.
Solid state polyamidation processes
Authors: Papaspyrides Constantine D. 
Published: April 2007

AbstractLow reaction rates and distinct transition phenomena from the solid to the melt state restrain solid state polymerisation (SSP) reactions of nylon salts for industrial application. To alleviate these problems, catalysts containing nylon salts are employed. In this study, hexamethylenediammonium adipate (HMA) particles were used containing a strictly controlled amount of catalyst, either phosphoric acid, sulphuric acid or boric acid. The results show considerable acceleration of the reaction rate, especially in the presence of boric acid, while the solid state character of the process is maintained throughout the total course of the reaction. Comparative polymerisation runs were monitored both by end‐group and quantitative water determinations of the reacting material to exclude any accumulation of the water of polycondensation within the reacting particles. The results obtained support further the mechanism proposed for the transition solid‐melt in SSP runs of nylon salts in the absence of catalysts. In the latter case extended water accumulation is the rule.
Castor‐oil‐modified epoxy resins as model systems of rubber‐modified thermosets. 1: Thermodynamic analysis of the phase separation
Authors: Ruseckaite Roxana A. , Williams Roberto J. J. 
Published: April 2007

AbstractCastor oil (CO) was used to replace polydisperse commercial rubbers (carboxy‐ or epoxy‐terminated butadiene‐acrylonitrile random copolymers, CTBN or ETBN) in model systems developed to analyse the origin of the phase separation process in rubber‐modified thermosets. Mixtures of CO with an epoxy resin based on the diglycidyl ether of bisphenol A (DGEBA) showed a higher miscibility than a typical CTBN (18% acrylonitrile)‐DGEBA system. Thermodynamic factors accounting for this behaviour are discussed using the Flory‐Huggins lattice model. Addition of a stoichiometric amount of ethylenediamine (EDA) to a DGEBA‐CO solution increased the miscibility. A pseudo‐binary approach was used to fit the cloud point curve up to 30% volume fraction of CO. Percentage conversions at the cloud point during the DGEBA‐EDA polymerization were experimentally determined and compared with theoretical predictions using the pseudo‐binary approach in the framework of the Flory‐Huggins lattice model. Reasonable agreement was found, giving direct evidence of the fact that phase separation results from the decrease in the entropic contribution to the free energy of mixing during polymerization.
Raman spectroscopic studies of the polyacrylonitrile‐zinc complexes in aqueous solutions of zinc chloride and bromide
Authors: Edwards H. G. M. , Hoskins A. R. , Johnson A. F. , Lewis I. R. 
Published: April 2007

AbstractRaman spectroscopic studies of the dissolution of polyacrylonitrile (PAN) in aqueous zinc halides are reported. The dissociation constants of aqueous PAN‐zinc chloride and PAN‐zinc bromide containing 60‐75% wt/wt and 65‐80% wt/wt zinc in aqueous polyacrylonitrile solutions, respectively, have been measured by Raman spectroscopy. Intensity measurements allowed for a quantitative measurement of the amount of free and complexed CN groups to be made, utilising the 2259 and 2290cm−1v(CN) stretching Raman bands. The degree of complexation was found to be small in many of the solutions. The effect of the addition of salt on the structure of thev(OH) band at 3000‐3800 cm−1was studied for the aqueous zinc salts and an aqueous sodium thiocyanate solution. The low wavenumber regions of the Raman spectra, Δv = 100‐350cm−1, for both zinc chloride and zinc bromide solutions of PAN have also been studied.
Thermal, spectral and morphological studies on cellulose, cellulose ethylthiophosphate and its metal complexes in air
Authors: Bhagwan Jai , Lal Krishan , Horrocks A. Richard , Price Dennis 
Published: April 2007

AbstractMetal complexes of thiophosphorylated cellulose, when heated, give rise to high char yields. These and related observations suggest that such derivatisation may give rise to novel flame retardant treatments for cellulosic materials.The kinetics of thermal degradation of cellulose, cellulose ethylthiophosphate (CESP) and metal complexes of the CESP have been studied by thermogravimetry (TG) and differential thermal analysis (DTA) from ambient temperature to 700°C in dynamic air to investigate the potential flame retardance of the CESP and its metal complexes. Various parameters such as energy, entropy, enthalpy and free energy of activation have been calculated using the Broido method and transition state theory. For the decomposition stage of thermal degradation, the activation energies of the CESP samples lie in the range 53‐133 kJmol−1 and of the metal complexes, 108‐177kJmol−1, which are found to be lower than that of cellulose (187 kJmol−1). Scanning electron micrographs of the CESP show that the fibrillar structure of cotton has become more evident and chars retain the general morphology of the original fibre although severe, localised zones of damage reflect the gross chemical and physical changes occurring during pyrolysis. The IR spectra of chars of modified samples indicate formation of compounds containing C=O, C=C and P=O groups. The mechanisms of thermal degradation of the CESP and its metal complexes have been proposed.
Studies on modified phenolic resin. Iv: Properties of phenolic resin modified with 4‐hydroxyphenyl‐ maleimide/n‐butylacrylate copolymers
Authors: Matsumoto Akihiro , Hasegawa Kiichi , Fukuda Akinori 
Published: April 2007

AbstractThree 4‐hydroxyphenylmaleimide/ n‐butylacrylate (HPMI/n‐BuA) copolymers with different monomer ratios were synthesized. Their average molecular weights, glass transition temperatures (T,g), and thermal decomposition temperatures were measured. It was found that these copolymers had higher average molecular weights and higher thermal decomposition temperatures than novolac.Modified phenolic resins were prepared by transfer moulding from moulding compounds consisting of novolac, the copolymer, hexamethylenetetramine (hexamine), and glass fibre. Properties of the three kinds of modified phenolic resins were examined by flexural test, impact test, dynamic thermomechanometry, and observation of morphology. It was found that phenolic resin modified with HPMI/ n‐BuA (1/3‐6) copolymer and modified with HPMI/n‐BuA (1/7‐0) copolymer showed good toughness and good heat resistance. It was also found that the heat resistance of modified phenolic resins was improved by after‐cure, but the mechanical properties were decreased by after‐cure: similar behaviour was observed for unmodified phenolic resin.
Synthesis of poly(4‐methylstyrene)‐ graft‐poly(ethylene oxide)s and application as polymeric dispersant in coal‐water mixture
Authors: Bonaccorsi F. , Lezzi A. , Prevedello A. , Lanzini L. , Roggero A. 
Published: April 2007

AbstractPoly(4‐methylstyrene)‐graft‐poly(ethylene oxide)s were prepared via polymerisation of ethylene oxide on to poly(4‐methylstyrene)s functionalised with hydroxyl groups. In this way, many ‘comb‐like’ polymers having different hydrophobic backbone length, hydrophilic branch length and frequency of branches were synthesised. These polymers were tested as dispersants in coal‐water mixtures in order to correlate the dispersing properties of this class of polymers with the investigated parameters.
An examination of the CTONI utilizing Gc‐Gf theory: A comparison of the CTONI and WJ‐III
Authors: Lassiter Kerry S. , Matthews T. Darin , Feeback Greg 
Published: April 2007

AbstractThe present investigation examined the validity of the Comprehensive Test of Nonverbal Intelligence (CTONI) with the Woodcock‐Johnson III Tests of Cognitive Abilities (WJ‐III COG) by administering these instruments in counterbalanced order to 60 college students. Results indicated that the mean CTONI NIQ score was not significantly different from the mean WJ‐III COG General Intellectual Ability (GIA) score. However, mean score differences were found between the CTONI NIQ and the WJ‐III COG Verbal Ability, Thinking Ability, Comprehension‐Knowledge, and Fluid Reasoning cluster scores. Although the correlations between the CTONI and the WJ‐III COG cluster scores were generally of small magnitude, the CTONI Geometric Nonverbal IQ composite score demonstrated construct specificity, whereas the CTONI Pictorial Nonverbal IQ scale did not. The implications of the findings are discussed and practitioners are asked to use caution when using this instrument to assess the fluid reasoning abilities of college students. © 2007 Wiley Periodicals, Inc.