bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of ammonium derivatives of oligoamidephosphates on the vulcanization characteristics and mechanical properties of some rubber compounds. 2. Styrene butadiene rubber compounds
Authors: Vladkova Todorka G. , Arnaudova Rumyana V. 
Published: April 2003

AbstractSBR compounds containing ammonium derivatives as neutral analogues of the oligoamidephosphates were studied with respect to their vulcanization characteristics and mechanical properties. Several differences between the effects of the neutral ammonium derivatives and the oligoamidephosphates were discovered, which may be connected with the different pHs of these products. As in the case of isoprene rubber compounds, the neutral products showed increased efficiency in comparison with the oligoamidephosphates. They offer the possibility of four‐fold reduction of the optimum cure time and partial replacement of the base sulphenamide accelerator. All SBR compositions containing neutral ammonium derivatives (NADs) were relatively well crosslinked and had cure characteristics and mechanical properties equal to, or better than, the corresponding compositions without neutral ammonium derivatives, even in the cases when the NAD amount was predominant. The results of our experiments give reason to assume that NADs participate in the vulcanization process with the formation of a different number of chemical bonds of various types. The NADs probably affect some physical interactions also.
Synthesis and characterisation of ternary polymer electrolytes with enhanced miscibility and high conductivity
Authors: Paulmer R. D. A. , Kulkarni A. R. 
Published: April 2003

AbstractThis paper reports the synthesis of amorphous polymer electrolytes. Polymer–salt complexes in the ternary system were prepared by mixing two polymers, namely poly(oxyethylene) and poly(oxypropylene glycol), with sodium iodide. This three component system is represented on a ternary pseudophase diagram. The ternary compositions are completely amorphous in a certain composition range and the composition POE–12%POPG–Nal with O/Na = 10 exhibited record high conductivity of 2 × 10−4 (Ω cm)−1 at ambient temperature. Formation of the amorphous electrolyte and the enhanced miscibility of the polymers were analysed using differential scanning calorimetry, X‐ray diffraction and ionic conductivity studies. The cation was found to play a major role in enhancing the miscibility of the polymers.
New amphiphilic poly(butadiene)‐graft‐poly(ethylene oxide)s
Authors: Decher Heribert , Stadler Reimund 
Published: April 2003

AbstractAmphiphilic graft copolymers with a poly(butadiene) backbone and poly(ethylene oxide) side chains were synthesized by grafting isocyanateterminated poly(ethylene oxide) on to partially hydroxylated poly(butadiene). The graft copolymers are water soluble if the fraction of hydrophilic poly(ethylene oxide) exceeds 50 wt%. Solutions of graft copolymers in water and tetrahydrofuran were studied by static light scattering and viscosity measurements. By dynamic light scattering in solution it was shown that the graft copolymers form clusters.
New fluorinated polysiloxanes containing an ester function in the spacer—II. Surface tension studies
Authors: Beyou Emmanuel , Bennetau Bernard , Dunoguès Jacques , Babin Pierre , Teyssié Dominique , Boileau Sylvie , Corpart Jean‐Marc 
Published: April 2003

AbstractThe surface tensions of fluorinated polysiloxanes prepared by hydrosilylation of unsaturated perfluoroalkyl esters derived from undecylenic acid [CH2CH(CH2)8COOCH2CH2RF, with RF = C6F13, C8F17, and C8F17(CH2)10COOCH2CH2CHCH2] by methylhydrodimethylsiloxane copolymers of various SiH contents have been measured. The critical surface tensions, γc, and the solid surface tensions, γDs, were deduced from n‐alkane and water contact angle data. They decrease as the perfluoroalkyl graft content of the copolymers increases. Some of them, which are in the range of the lowest surface tension fluoro polymers known, are observed when the fluorinated segments are self‐organized at the interface, i.e. when the polymers are mesomorphous or crystalline at room temperature.
Influence of dynamic cyclic extension on the electrical conductivity of fast extrusion furnace (FEF) black loaded rubber vulcanizates
Authors: Nasr G. M. , Darwish K. A. , Khairy S. A. , Hassan H. H. , Ateia E. 
Published: April 2003

AbstractThe influence of dynamic cyclic extension on the electrcal conductivity (σ) of 100 parts FEF carbon black loaded rubber (NR and SBR) vulcanizates was studied. The conductivity showed an initial rapid decrease with increasing cyclic strain amplitude, indicating a probable breakdown of the carbon black structure, owing to the masking of carbon particles by insulating rubber layers.The conduction mechanisms in these composites in terms of both the number of strain cycles and the strain amplitude were also studied. In addition, the temperature coefficient of conductivity was calculated for different amplitudes. It was greatly affected by the magnitude of the strain amplitude.
Behaviour of catalase immobilised on poly(acrylonitrile)‐g.co‐hydroxyethyl methacrylate when used in a continuous system
Authors: Piedade A. P. , Gil M. H. , Cavaco M. C. , Andrade M. E. 
Published: April 2003

AbstractSeveral poly(acrylonitrile)‐g.co‐hydroxyethyl methacrylate graft copolymers were prepared using gamma irradiation (60Co). The influences of the monomer concentration and the time of irradiation on the level of grafting were studied. Some of the graft copolymers obtained were characterised and used for the covalent immobilisation of catalase using two different methods of activation of the support.The enzyme/support systems obtained were characterised and the best selected to be used in a first approach for the study of the deterioration of a hydrogen peroxide solution in a continuous system.
Monomer sequence length distributions of hard segments of linear segmented poly(urethane–urea)s 2: computer simulation by the Monte Carlo method
Authors: Hanahata Hiroyuki , Kamide Kenji 
Published: April 2003

AbstractAn attempt was made to calculate, by the Monte Carlo method, monomer sequence length distributions of the hard segment (MSLDH) within a linear segmented poly(urethane–urea) (PUR) synthesised by the prepolymer method in which an isocyanate‐terminated prepolymer. A…A, an unreacted monomer diisocyanate, BB, and a diamine as chain extender, XY, are reacted to form PUR. MSLDH is governed by the molar ratio of [A…A]/[BB] and is dramatically affected when three kinds of unequal reactivity associated with the reactants are significant simultaneously; the induced asymmetry, the penultimate effect of an NCO group, and the induced asymmetry of an amino group. By applying the above simulation technique, the unequal reactivities are estimated in both the prepolymerisation and polymerisation reactions based on methylenebis(4‐phenylisocyanate), MDI, poly(tetramethyleneoxide), PTMO, and ethylenediamine, EDA. In addition, the effect of the one‐shot method instead of the prepolymer method on MSLDH is also examined.
Skinned polymeric membranes. Approach to the mechanism of formation of surface holes
Authors: Addad J. P. Cohen , Icard B. , Pellicioli L. 
Published: April 2003

AbstractIt is shown quantitatively that the formation of holes through the skin of membranes, prepared by the quick immersion in water of polyetherimides in solution in N‐methylpyrrolidone, is governed by the solvent mobility. The surface pattern observed by videomicroscopy exhibits a characteristic distance between neighbouring holes (≃5 μm) which is a linear function of D−1s; Ds is the solvent diffusion coefficient in the polymeric solution, measured using a pulsedfield gradient NMR technique. The dependence of this distance on the solvent concentration in water is also characterized.
New poly(amide–imide)s syntheses. 17. Preparation and properties of poly(amide–imide)s derived from N‐phenyl‐3,3‐bis[4‐(4‐aminophenoxy)‐phenyl]phthalimidine, trimellitic anhydride, and various aromatic diamines
Authors: Yang Chin‐Ping , Lin Jiun‐Hung 
Published: April 2003

AbstractA dicarboxylic acid (1) bearing two phthalimide rings was prepared by the condensation of N‐phenyl‐3,3‐bis[4‐(4‐aminophenoxy)phenyl]phthalimidine and trimellitic anhydride. A new family of poly(amide–imide)s having inherent viscosities of 0.65–1.65 dl/g was prepared by the triphenyl phosphite activated polycondensation of the diimide–diacid 1 with various aromatic diamines in a medium consisting of N‐methyl‐2‐pyrrolidone (NMP), pyridine, and calcium chloride. All the resulting polymers showed an amorphous nature and were readily soluble in polar solvents such as NMP and N,N‐dimethylacetamide. The soluble poly(amide–imide)s afforded transparent, flexible, and tough films. The glass transition temperatures of these polymers were in the range 249–340°C and the 10% weight loss temperatures were above 545°C in nitrogen.
Morphology and melting behaviour of poly(ethylene terephthalate) crystallized from the glassy state
Authors: Qudah Ali M. A. , Al‐Raheil Ismail A. 
Published: April 2003

AbstractThe influence of annealing conditions on the morphology and melting behaviour of poly(ethylene terephthalate) (PET) was studied. PET annealed under isothermal conditions often shows double melting endotherms depending on the annealing temperature (Ta) and the heating rate of the calorimeter. It was found that the morphological structure and the lower melting peak depend strongly on the annealing temperature, Ta. The increase of the lower melting peak temperature with Ta is due to an increase of the lamellar thickness within the spherulitic structure and to a higher crystallite perfection.
Counterion association to cationic polyelectrolytes in methanol/water mixtures
Authors: Barraza Raúl G. , Rios Hernán E. 
Published: April 2003

AbstractThe effect of the nature of the medium on the chloride and bromide condensation to a cationic polyelectrolyte was studied. Methanol/water mixtures were used as solvent in order to vary continuously the properties of the medium. The counterion–polyion interaction was studied by the determination of the Eisenberg interaction parameter (f*) by means of electrical conductivity measurements. Results indicate that f* parameters increase while the limiting electrical conductivity is rapidly decreasing. This apparently anomalous phenomenon is interpreted as a preferential solvation of the polyelectrolyte which brings about a conformational change, as revealed by the intrinsic viscosity behavior of the solutions. This change could induce an increase in the average distance between charges without further dissociation, which could explain the observed behavior of the f* parameter. It is concluded that the actual dielectric constant which governs the polyion–counterion interaction in the polyelectrolyte domain is not the bulk dielectric constant.
Segmental mobility model for diffusion of gases in polymers
Authors: Stuk L. G. F. 
Published: April 2003

AbstractDiffusion of small molecules in polymers is described quantitatively in terms of segmental mobility processes. The diffusion coefficient depends on a diffusive jump length, which is characteristic of the polymer, and a jump frequency, which is equated to the segmental mobility rate. The presence of a particular solute increases mobility of the surrounding polymer segments by a predictable amount, which is related to the partial molar volume of the solute. The theory is fit to experimental diffusion data, and partial molar volumes are calculated from the fitting parameters. Good agreement with experimental partial molar volumes is obtained.
Toward a prediction of the phase behavior of polyamide blends
Authors: Hu Jiangbin , Painter Paul C. , Coleman Michael M. , Krizan Timothy D. 
Published: April 2003

AbstractAs we have reported recently, the application of association models has provided a theoretical basis for the calculation of the free energy changes and phase diagrams of binary polymer blends in which hydrogen bonding plays a significant role. Here we report theoretical calculations of spinodal phase diagrams of a series of polyisophthalamide‐polyether blends and compare the predictions with experimental observations of the miscibility of these polymer blend systems. The general agreement between theory and experiment is very encouraging and has important ramifications to discussions of polymer‐induced crystallnity, the minimum number of hydrogen bonding sites necessary to ensure significant molecular mixing, and the effect of hydrogen bonding on the breadth of “miscibility windows.”
Transport properties of a thermotropic liquid‐crystalline polyester
Authors: De Candia F. , Renzulli A. , Vittoria V. , Roviello A. , Sirigu A. 
Published: April 2003

AbstractTransport properties of a thermotropic liquid‐crystalline polymer with the mesogenic group in the main chain were analyzed. Different samples were examined as films obtained by pressure molding and rapid quenching to 0°C. Thermal and transport parameters of the quenched films were measured. The results show that the isotropization enthalpy and sorption coefficient are interdependent, while the diffusion coefficient is substantially constant in all the samples analyzed. These results suggest that the permeable component behaves in the same way in the different samples but is present in different amounts, the transport phenomena occurring in amorphous, or less ordered, interphase regions within impermeable mesomorphic and crystalline domains.
Radiation effects on poly(1‐chloro‐1‐alkynes)
Authors: Tang Ben‐Zhong , Masuda Toshio , Higashimura Toshinobu , Yamaoka Hitoshi 
Published: April 2003

AbstractThe γ‐radiolysis behavior of poly(l‐chloro‐1‐alkynes)
\[
[\rlap{‐‐} ({\rm CCI} = {\rm CR}\rlap{‐‐} )_n ;{\rm R} = n ‐ {\rm alkyl}]
\]
greatly changed with the length of alkyl group and with the presence or absence of oxygen. When γ‐irradiated in air, poly(l‐chloro‐1‐hexyne) (R = n‐C4H9) decomposed to oligomers; its Gs value was as large as 5.4. When irradiated in vacuum, this polymer partly gelled. In contrast, poly(l‐chloro‐1‐decyne) (R = n‐C8H17) partly gelled even by irradiation in air. A high‐dose irradiation of this polymer in vacuum resulted in the quantitative formation of a gel. The polymers irradiated in air contained carbonyl and hydroxyl groups, indicating the participation of oxidation reaction. Comparison with their thermolysis leads to a conclusion that these Cl‐containing polyacetylenes are radiation‐sensitive irrespective of their high thermal stability.
Concentration dependence of the flory‐huggins interaction parameter of a polymer blend as determined by small‐angle X‐ray scattering experiments
Authors: Koch T. , Strobl G. R. 
Published: April 2003

AbstractDirect determination of the Flory‐Huggins interaction parameter χ of a polymer blend by small‐angle x‐ray scattering experiments is possible on the basis of the random phase approximation, if absolute intensities are measured. The usually superposed void scattering has to be properly accounted for. Investigations on a series of blends of polystyrene and poly(styrene‐co‐bromostyrene) yielded χ dependent upon the blend composition. χ shows only slight variations. Scattering data also give the radii of gyration of the two components in the blend.
Miscibility and orientation behavior of poly(vinyl alcohol) / poly(vinyl pyrrolidone) blends
Authors: Nishio Yoshiyuki , Haratani Tatsuo , Takahashi Toshisada 
Published: April 2003

AbstractThe miscibility of poly(viny1 alcohol)/poly(vinyl pyrrolidone) (PVA/PVP) blends is investigated by differential scanning calorimetry (DSC) and wide‐angle x‐ray diffraction (WAXD). The molecular orientation induced by uniaxial stretching of the blends is also examined by WAXD and birefringence measurements. It is shown by the DSC thermal analysis that the polymer pair is miscible, since a single glass transition temperature (Tg) is situated between the Tgs of the two homopolymers at every composition. The Tg versus composition curve does not follow a monotonic function but exhibits a cusp point at a PVP volume fraction of a little under 0.7, as in a case predicted by Kovacs' theory. The presence of a specific intermolecular interaction between the two polymers is suggested by an observed systematic depression in the melting point of the PVA component. A negative value of the polymer‐polymer interaction parameter, χ12 = 0.35 (at 513 K), is estimated from a thermodynamic approach via a control experiment using samples crystallized isothermally at various temperatures. The extent of optical birefringence (Δn) of the drawn blends decreases drastically with increasing PVP content up to 80 wt %, when compared at a given draw ratio, and ultimately Δn is found to change from positive to negative at a critical PVP concentration of a little over 80 wt %. Discussion of the molecular orientation behavior takes into consideration a birefringence compensation effect in the miscible amorphous phase due to positive and negative contributions of oriented PVA and PVP, respectively.
Simultaneous scission and crosslinking of polystyrene chains on irradiation by ultraviolet light in CCl4 and CHCl3 solutions
Authors: Turzyński Zbigniew , Witkowski Konrad , Woliński Leszek , Szafko Jerzy 
Published: April 2003

AbstractThis work is the continuation of the investigations of changes in the structure of polystyrene initiated by radiation of wavelengths λ ≥ 270 nm in oxygen‐free solutions in CCl4 and CHCl3. Coupled integral and quasielastic light scattering techniques have been applied, enabling observations of changes in the molecular weight distribution function w(M). On the basis of the experimental data and application of Saito and Inokuti's theoretical results, it is shown that in the irradiated solutions polystyrene undergoes simultaneous chain scission and crosslinking. The average number of scissions and crosslinks per macromolecule as a function of irradiation time is calculated. The effect of macromolecular mobility on both photochemical processes is also discussed.
On the universality of sedimentation of flexible polymers in dilute and semidilute solutions
Authors: Nyström B. , Roots J. 
Published: April 2003

AbstractIn the present investigation, the sedimentation behavior, over an extended concentration range, in solutions of polystyrenes under good, marginal, and theta solvent conditions, is analyzed in the framework of a recent theoretical model, which takes into account the gradual screening of both hydrodynamic and excluded‐volume interactions in the semidilute regime. The model inspires the construction of universal plots of the form S/S0 versus ksc, where S is the sedimentation coefficient at polymer concentration c, S0 is that at infinite dilution, and ks is the concentration dependence coefficient. The resulting analytical expressions, without adjustable parameters, are consistent with experimental sedimentation data over the whole concentration range studied.
Polymerization of para‐xylylene derivatives. VI. morphology of parylene N and parylene C films investigated by gas transport characteristics
Authors: Yeh Y.‐S. , James W. J. , Yasuda H. 
Published: April 2003

AbstractPolychloro‐p‐xylylene (Parylene C) and poly‐p‐xylylene (Parylene N) films were synthesized in vacuum with and without the presence of 42 mtorr of argon at various deposition temperatures and three different dimer sublimation rates. Depending on the synthesis conditions, the morphology of the films can vary from a homogeneous (nonporous) structure to a heterogeneous (porous) structure. The transport coefficients of the gases He, O2, N2, and CO2 through these films were measured at 25°C. The transport coefficients for both types of films vary with the deposition temperature and the dimer sublimation rate. The variation, however, cannot be solely explained by the change of crystallinity. Anomalous transport behavior is observed in the homogeneous, as‐synthesized polymers of relatively high crystalline content (above 20–30%). In many cases the permeabilities and diffusivities increase despite an increase in crystallinity. The effects of crystallization induced by isothermal and solvent annealing on the transport coefficients of polymers of Parylene C are different from those of Parylene N synthesized with or without argon. The mean pore size and effective porosity of the porous films were calculated from gas permeation data. For Parylene C and Parylene N porous films synthesized without argon, increasing the dimer sublimation rate or decreasing the deposition temperature increases the mean pore size but decreases the effective porosity. For Parylene N porous films synthesized in the presence of argon, increasing the dimer sublimation rate or decreasing the deposition temperature results in a decrease in the mean pore size but an increase in the effective porosity. Overall, no appreciable change in transport coefficients is observed upon addition of an inert gas.
Chemorheology relations for epoxy‐amine crosslinking
Authors: Bidstrup Sue Ann , Macosko Christopher W. 
Published: April 2003

AbstractThe goal of this study is to elucidate the relationship between the mechanism of bond formation, resulting structure, and the viscosity during the step polymerization of a thermoset. The system chosen for this work consists of a bifunctional epoxy, diglycidyl ether of bisphenol A, cured with a tetrafunctional amine, diaminodiphenyl sulfone. Steady shear and dynamic viscosity are measured as a function of extent of reaction throughout the epoxy‐amine cure. Branching theory is used to relate the extent of reaction (i.e., conversion of epoxy groups) to certain structural parameters, including the weight‐average molecular weight. The combination of the viscosity‐conversion data with the branching theory enables the correlation between changes in rheological properties and network structure during polymerization. The steady shear viscosity rise is modeled as the product of a structure‐dependent friction factor and weight‐average molecular weight. The structural significance of the point in cure when the dynamic storage and loss modulus are equal (i.e., tan δ = 1) is also explored.
Bubble nucleation in polymeric liquids. II. theoretical considerations
Authors: Han James H. , Dae Han Chang 
Published: April 2003

AbstractA theory based on classical nucleation theory is developed for bubble nucleation in polymer solutions. The theory requires information on solubility, diffusivity, concentration, surface tension, temperature, and degree of supersaturation. The effects of supersaturation and of the presence of large molecules in a liquid mixture on the free energy of bubble formation are included in the theoretical development. A semiempirical equation for the determination of bubble nucleation rate is developed, with the aid of experimental results reported in part I of this series. Using the experimental data, computer simulations of bubble nucleation in polymer solutions are performed. The consumptions of the volatile component in a liquid mixture, due to bubble nucleation and subsequent growth, and the variation of bubble nucleation rate during the expansion process are included in the simulation of the bubble nucleation process.