bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crosslinking of polypropylene–polyethylene blends by peroxide and the effect of pentaerythritol tetrallyl ether
Authors: Borsig Eberhard , Fiedlerová Agnesa , Rychlá Lyda , Lazár Milan , Rätzsch Manfred , Haudel Gottfried 
Published: April 2003

AbstractCrosslinking of polypropylene–polyethylene (PP‐PE) blends involving 10, 20, 30, 40, 50, 60, 70, 80, and 90% of PP with dicumylperoxide (DCP) or tert‐butyl perbenzoate (TBPB) and in the presence of coagent pentaerythritol tetrallyl ether (PETA) was investigated at 180°C. It was found that at lower concentrations of peroxide alone (e.g., 2.5% of DCP) only PE component is crosslinked in all compositions of PP‐PE blends. In the crosslinking of PP‐PE 50:50 with 4% of TBPB, insoluble gel was obtained, which contained 13% PP and 87% PE. If 2% PETA was also used, the portion of PP in gel increased to 39%; the total yield of gel in PP‐PE blend increased from 50 to 70%. The lower crosslinking efficiency of coagent PETA in the PP‐PE blends compared with PP alone is associated with better solubility of the coagent in the PE phase in contrast to the PP phase. The coagent does not particularly raise the crosslinking efficiency of peroxide in PE, but increases it in the PP phase. A remarkable decrease in melting temperature and temperature of crystallization of both polymer components depending on peroxide concentration was found by calorimetric measurements.
Bulk functionalization of ethylene–propylene copolymers. II. Influence of the initiator concentration and of the copolymer composition and chain microstructure on the reaction kinetics
Authors: Greco Roberto , Maglio Giovanni , Musto Pellegrino , Scarinzi Gennaro 
Published: April 2003

AbstractThe effect of the dicumylperoxide (DCPO) concentration on the kinetics of the bulk functionalization of an ethylene‐propylene copolymer (EPR) has been studied. It has been found that, enhancing the DCPO initial concentration in the reaction mixture, results in both increased initial reaction rate and grafting process efficiency. DCPO content also affects degradation, which always accompanies the grafting reaction. At high DCPO content, products with a high degree of grafting and intrinsic viscosity close to that of the parent copolymer can be obtained. Furthermore, the influence of the EPR composition and chain microstructure on the functionalization as well as on the degradation processes has been investigated. By increasing the C2 content in EPRs prepared by using vanadium‐based conventional catalysts, obtains faster functionalization kinetics and a less pronounced degradation of the products. At fixed experimental conditions, the highest grafting degrees have been obtained by using EPRs prepared by high‐yield titanium catalysts and characterized as a block‐like microstructure. The experimental results have been interpreted on the basis of a proposed reaction mechanism.
Anionic polymerization of styrene: Integration with styrene monomer production
Authors: Priddy Duane B. , Pirc Michael 
Published: April 2003

AbstractAnionic polymerization and ethylbenzene dehydrogenation were carried out in the laboratory using continuous reactor designs and conditions typical of current commerical processes. The dehydrogenator was operated at 43–55% conversion with continuous distillation of the ethylbenzene/styrene mixture to remove byproducts that would interfere with the subsequent anionic polymerization. The anionic polymerization was carried out using a reactor of the CSTR type which operated at > 99% conversion of styrene. The volatiles were recovered from the polymer syrup and recycled back to the dehydrogenator. During 4 months of continuous operation the integrated process showed no detrimental buildup of impurities which affected the anionic polymerization or dehydrogenation. The polystyrene produced had excellent color, clarity, thermal stability, and polydispersity (Mw/Mn = 2.1–2.4). The ability to control weight average molecular weight was within a range of 20,000 using an on‐line GPC in concert with a colorimeter.
Thermal stability characteristics of some resins from chemically modified PVC
Authors: Moitra Subrata , Biswas Mukul 
Published: April 2003

AbstractPVC has been modified by chlorine displacement reaction with m‐aminophenol, bisphenol A, and phenophthalein. Sulfonation of these condensates yields bifunctional weak acid resins which do not exhibit SO3H ionogenic group. Reaction of PVC with presulfonated bisphenol A, phenolphthalein, and phenol yields strong acid resins. Thermal stability characteristics of these various resins have been determined and the results indicate that such modifications improve the overall thermal stability of PVC.
A re‐evaluation of heat transfer associated with drawing of polymers
Authors: Chung B. T. F. , Liu F. 
Published: April 2003

AbstractThe temperature rise due to heat generation associated with drawing of polymer is re‐evaluated and rederived starting from the first law of thermodynamics. The errors of both formulations and sample calculations made in a previous investigation were corrected. The predicted efficiency or the fraction of mechanical work converted into heat during necking based on the present formulations is found to be reasonable.
Anomalous behavior of cured epoxy resins: Density at room temperature versus time and temperature of cure
Authors: Pang K. P. , Gillham J. K. 
Published: April 2003

AbstractThe room temperature density (ρRT) of a difunctional aromatic epoxy resin cured with a tetrafunctional aromatic amine passes through a maximum value in the vicinity of gelation with increasing conversion. For a given cooling rate cure resutls in a unique value of ρRT for each conversion as long as the material does not vitrify on cure. The occurrence of vitrification during cure eliminates the one‐to‐one relationship because of the nonequilibrium nature of the glass transition region and of the glassy state. In the glass transition region there is competition between physical aging which increases the density and chemical aging which, after gelation, decreases ρRT. After gelation, prolonged isothermal cure and physical aging to well beyond vitrification result in limiting values of ρRT which decrease with increasing temperature of cure. The maximum in the ρRT vs. conversion relationship is discussed in terms of the effects of shrinkage due to cure, the corresponding nonlinear increase in the glass transition temperature with increasing conversion after gelation, and longer relaxation times in the glass transition region with increasing crosslink density. Other factors which affect room temperature density are discussed.
Prediction of the concentration dependence of diffusion coefficients of polymers in solution
Authors: Qian J. W. , Rudin Alfred 
Published: April 2003

AbstractThe hydrodynamic volumes of solvated polymers shrink with increasing concentrations in solution until a concentration (cx) is reached at which the effective dimensions are those of a Theta solvent. A simple model (Ref. 7) can be used to calculate the volume fraction of solvated polymer coils as a function of concentration. From this, the concentration dependence of diffusion coefficients can be estimated (Ref. 5). Calculated data are in very good agreement with experimental values except for some lower molecular weight polymers in poor solvents.
Estimation of reactivity ratios of N‐methacryloloxyphthalimide copolymers by1H NMR
Authors: Shaaban A. F. , Khalil A. A. , Messiha N. N. 
Published: April 2003

AbstractCopolymerization of N‐methacryloyloxyphthalimide (NMP) with methyl acrylate (MA), methyl methacrylate (MMA), and acrylonitrile (AN) was carried out in dimethylformamide using azobisisobutyronitrile (AIBN) as an initiator at 60°C. The estimation of the copolymer compositions were carried by 1H nuclear magnetic resonance (NMR) spectroscopy. The monomer reactivity ratios for NMP‐MA, NMP‐MMA, and NMP‐AN systems were found to be r1 = 1.223, r2 = 0.208, r1 = 1.441, r2 = 0.704, r1 = 1.496 and r2 = 0.228, respectively, by Kelen–Tüdős method. Also, the Q and e values for NMP monomer was found to be Q = 0.90 and e = 0.01, respectively.
Permselectivities through artificial membranes at a non‐steady state
Authors: Higuchi Akon , Nakagawa Tsutomu 
Published: April 2003

AbstractNon‐steady‐state flux ratios of oxygen to nitrogen in a poly(dimethyl siloxane) membrane are theoretically investigated as a function of time. Concentration profiles of oxygen and nitrogen are found to decay to a negligible concentration with an increase of the distance from membrane surface and it is observed that oxygen penetrates deeper than nitrogen in the membrane at the non‐steady state. Differences of concentration profiles of oxygen and nitrogen lead to enormously high selectivity for oxygen at the non‐steady state. The flux and selectives are studied under the condition that the upstream pressure is pulsating to keep the non‐steady state continuously as suggested by Paul[Ind. Eng. Chem. Proc. Des. Dev., 10, 375 (1971)]. Model calculations are also performed for the concentration of uranium 235 from natural uranium. The flux ratio of uranium 235 to uranium 238 in the non‐steady state is calculated to be 1.144 at time/L2 = 800 s/cm2 (L = membrane thickness), which is higher than the value, 1.00429, at a steady state.
Thermodynamic study of polymer–solvent systems by reversed‐flow gas chromatography
Authors: Agathonos Pericles , Karaiskakis George 
Published: April 2003

AbstractReversed‐flow gas chromatography, a new method for studying heterogeneous catalysis, diffusion, adsorption, evaporation, and other related phenomena, is now applied to the determination of activity of the solvent in a polymer–solvent system in the whole range of polymer concentration, as well as for the calculation of excess partial molar thermodynamic functions of mixing. The systems used were polystyrene in cyclohexane, polyvinylacetate in cyclohexanone and polyvinylpyrrolidone in methanol. In the first system, which was studied in detail, weight fraction activity coefficients (a1/w1) at several temperatures (333.8–348.1 K) and various polymer concentrations (0.020–0.131 g/g) were determined. From the latter parameters weight fraction activity coefficients at infinite dilution (a1/w1)∞ were computed. Flory–Huggins interaction parameters x and solubility parameters δ2 were also determined. Finally, the thermodynamic parameters found by the present method are compared with those determined by other techniques or calculated theoretically.
Studies on the thermal properties of PVC : Polystyrene alloy
Authors: Eboatu A. N. , Olojo D. O. , Momoh M. 
Published: April 2003

AbstractThe effect of composition on the thermal properties of poly(vinyl chloride) (PVC)–polystyrene (PSt) alloy was investigated. Using the DSC, it was observed that the glass transition temperature (Tg) and melting point (Tm) as well as the enthalpic change at melting (ΔH) were altered with respect to their theoretical values. An attempt is made to explain these facts.
Miscible blends from plasticized poly(vinyl chloride) and epoxidized natural rubber
Authors: Varughese K. T. , De P. P. , Sanyal S. K. , De S. K. 
Published: April 2003

AbstractMiscible blends from plasticized poly(vinyl chloride), and epoxidized natural rubber having 50 mol% epoxidation level were prepared in a Brabender Plasticorder by the melt‐mixing technique. Changes in Brabender torque and temperature, density, dynamic mechanical properties, and differential scanning calorimetry of the samples were examined as a function of blend composition. The plasticized poly(vinyl chloride)/epoxidized natural rubber blends behaved as a compatible system at all composition ranges as evident from their single glass‐rubber transition temperature (Tg) obtained from dynamic mechanical analysis as well as from differential scanning calorimetry. Profound changes in the nature of the glass‐rubber transition were noted with respect to blend composition. The Tg‐width values of blends lie between those of plasticized poly(vinyl chloride) and epoxidized natural rubber.
A new inductive detection for the magnetoviscometer
Authors: Hermann W. , Sobczak R. 
Published: April 2003

AbstractFor a new magnetoviscometer with an inhomogeneous magnetic field to move iron spheres similar to the Stokes experiment, a nonoptical detection was developed. As a measuring principle the change of the impedance of a coil, penetrated by the sphere is used. The measuring principle is the change of impedance of an induction coil wrapped around the cell by the sphere. The measuring block, consisting of heating elements, detection coils, and a measuring cell is quite simple and therefore well suited for measuring under pressure. Since the proper cells are simply brass cylinders closed by a screw, they can be thrown away after the experiment (e.g., for network‐building polymers). Examples for said measurements are given.
Mathematical modeling of emulsion copolymerization reactors
Authors: Richards John R. , Congalidis John P. , Gilbert Robert G. 
Published: April 2003

AbstractThis article presents the physical mechanism and the mathematical structure of a comprehensive dynamic emulsion polymerization model (EPM). EPM combines the theory of coagulative nucleation of homogeneously nucleated precursors with detailed species material and energy balances to calculate the time evolution of the concentration, size, and colloidal characteristics of latex particles; the monomer conversions; the copolymer composition; and molecular weight in an emulsion system. The capabilities of EPM are demonstrated by comparisons of its predictions with experimental data from the literature covering styrene and styrene/methyl methacrylate polymerizations. EPM can successfully simulate continuous and batch reactors over a wide range of initiator and added surfactant concentrations.
Radiation grafting of α,β,β‐trifluorostyrene onto poly(ethylene–tetrafluoroethylene) film by preirradiation method. I. Effects of preirradiation dose, monomer concentration, reaction temperature, and film thickness
Authors: Momose Takashi , Yoshioka Hiroko , Ishigaki Isao , Okamoto Jiro 
Published: April 2003

AbstractPreirradiation grafting of α,β,β‐trifluorostyrene onto poly(ethylene–tetrafluoroethylene) film was studied. The trapped radicals formed upon irradiation were able to induce graft polymerization under appropriate conditions. The influences of the grafting conditions were analyzed kinetically. The grafting rate dependency on the preirradiation dose was found to be of order 0.3, and the monomer concentrations, 1.0. The overall activation energies for this grafting were calculated to be 6.2 × 104 and 9.3 × 103 J/mol below and above 50°C. The grafting rate was found to be independent of the film thickness, which ranged from 25 to 100 μm.
Turbulent drag effectiveness and shear stability of xanthan‐gum‐based graft copolymers
Authors: Ungeheuer S. , Bewersdorff H.‐W. , Singh R. P. 
Published: April 2003

AbstractA number of graft copolymers of xanthan gum and polyacrylamide have been synthesized by grafting acrylamide onto xanthan gum using the ceric‐ion‐initiated solution polymerization technique. The effects of various synthesis parameters such as amount of catalyst, reaction time, and ratio of xanthan and acrylamide on drag reduction effectiveness of the graft copolymers have been studied. The scaling up of grafting reaction has been accomplished in 40‐L reactor. The drag reduction effectiveness of the graft copolymers is investigated over a wide range of concentrations and Reynolds numbers. It is shown that the maximum drag reduction obtainable in xanthan gum solutions above 300 ppm can be obtained in solutions of graft copolymers at concentrations of 100–150 ppm. The grafting also improves the shear stability at higher Reynolds numbers. The shear stability of the graft copolymers at constant wall stress has been found to be superior to polyacrylamide and the mixtures of polyacrylamide and xanthan gum. In general, the shear stability of graft copolymers and polyacrylamide is shown to increase with concentration. The drag reduction characteristics and shear stability have been discussed in terms of structural features of the graft copolymers. The drag reduction characteristics of the graft copolymers are found to be similar to those of flexible polymers.
Preparation of glycidyl celluloses from completely allylated methylcellulose and tri‐O‐allylcellulose
Authors: Kondo Tetsuo , Ishizu Atsushi , Nakano Junzo 
Published: April 2003

AbstractGlycidyl celluloses were prepared from completely allylated methylcellulose and tri‐O‐allylcellulose with m‐chloroperbenzoic acid in homogeneous chloroform solutions. The degrees of substitution (DS) by epoxy groups were 0.60 and 1.33 for the products prepared from allylated methylcellulose and tri‐O‐allylcellulose, respectively. They were soluble in not only many organic solvents, but also methanol‐water mixtures [more than 70% (v/v)]. These products were characterized by infrared spectroscopy (IR), 13C‐NMR spectroscopy, and gel permeation chromatography (GPC).
Phenoxy resin: Characterization, solution properties, and inverse gas chromatography investigation of its potential miscibility with other polymers
Authors: Iribarren J. I. , Iriarte M. , Uriarte C. , Iruin J. J. 
Published: April 2003

AbstractA commercial sample of a copolymer of bisphenol‐A and epichlorohydrin (Phenoxy) has been carefully fractionated in a dioxane/methanol mixture. Mark‐Houwink constants in THF and the molecular weight distribution of the raw material have been obtained on the basis of the universal calibration procedure. Conformational magnitudes such as the characteristic ratio C∞ or the steric factor σ have been determined from viscometric data at 63°C in a good (dioxane) and a θ‐solvent (1,2‐dichloroethane). Inverse gas chromatography was used to study phenoxy miscibility with a variety of polymers. Using different probes as model compounds, the partial molar enthalpy of mixing ΔH at infinite dilution has been determined. Results were correlated with the reported miscibility of phenoxy with polyesters, polyethers, and polyoxides. A linear multiparametric correlation of ΔH with polarizabilities, dipole moments, and hydrogen bond accepting powers provides for a comprehensive analysis of other miscible systems.
Synthesis of 6‐ and 7‐oxo poly(vinyl ester)s and their evaluation
Authors: Shantha K. L. , Pratap G. , Rao V. S. Bhaskar 
Published: April 2003

AbstractLong chain vinyl esters of 6‐ and 7‐oxoaliphatic acids are synthesized as intermediate monomers for the preparation of poly 6‐oxo and 7‐oxo vinyl esters. These comblike polymers have wide applications as fluidity improvers. Detailed characterization of all the intermediates is done by IR, PMR, and MS for the first time. Their evaluation is done on high waxy Bombay high crude.
Characterization of substituted phenol–formaldehyde resins using solid‐state carbon‐13 NMR
Authors: Sinha Brijnaresh R. , Blum Frank D. , O'Connor Daniel 
Published: April 2003

AbstractCrosslinked substituted phenol–formaldehyde resins were synthesized from cashew nut shell liquid, 3‐n‐pentadecylphenol and phenol with formaldehyde. The resulting resins were crosslinked and investigated using carbon‐13 NMR in the solid state using cross‐polarization, magic angle spinning, and dipolar decoupling. Comparisons were made between the spectra of pure phenol–formaldehyde resins and it was shown possible to distinguish between the resins. It was also shown that the proton‐dephased spectrum gave better spectral resolution for the substituted compounds. In addition, the solids carbon‐13 technique verified that the degradation of the substituted phenolic resins occurs first with the degradation of the side chain in agreement with suggestions from earlier work.
Shear rate dependence of the viscosity of cellulose nitrate solutions in the dilute concentration regime revisited
Authors: Marx‐Figini M. , Gonzalez F. Rex 
Published: April 2003

AbstractA detailed rheological study of cellulose nitrate in ethylacetate had been carried out in the dilute concentration (c) regime, covering a degree of polymerization (DP) range between 300 < DPη < 7000 and shear rates (\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document}) between 100 s−1 < \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document} < 2000 s−1. The results show a strong dependence of the transition Newtonian to non‐Newtonian behavior on the three variables \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document}, DP, and c, similar to that found recently on solutions of synthetic polymers. Emphasis has been put on the critical concentrations corresponding to the standard shear rate 1000 s−1 to correspond to the standard conditions (\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document} ≅ 1000 s−1; 0.3 < [η] · c < 0.6; DS = 2.90 ± 0.02) proposed for the determination of the intrinsic viscosity [η] of cellulose nitrates. It is shown that solutions with concentrations adjusted according to the above given conditions still exhibit Newtonian behavior, up to the highest range of DP. It follows, therefore, that applying the standard conditions, an extrapolation to \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document} = 0 as has been proposed often for the intrinsic viscosity determination of cellulose nitrate is not advisable and results in considerable error. Considering the relationship between [η] and DP, the present results indicate that the decrease of the exponent (a) from a = 1.0 to a = 0.76, taking place above a DP ≅ 1000, is not a consequence of the applied shear rate but rather of the molecular properties of the solutes themselves.
Graft copolymerization of poly(butyl methacrylate) onto wool in the presence of air and nitrogen atmosphere. II
Authors: Shukla J. S. , Tiwari S. C. 
Published: April 2003

AbstractPoly(butyl methacrylate) (PBMA) was grafted onto wool in the presence of air and nitrogen atmosphere using potassium bromate and thioaceticacid (TAA) as redox initiating system, under different reaction conditions. The percentage grafting and percentage efficiency have been determined as a function of various reaction variables and the results have been compared. The graftcopolymer was characterized by scanning electron micrograph, thermogravimetry, and molecular weight.
The strain rate dependency of fracture in polyethylene: Fracture initiation
Authors: Barry D. B. , Delatycki O. 
Published: April 2003

AbstractThe dependency of fracture on the rate of strain of a range of polyethylene samples was measured in three point flexural tests at 23°C. The range of strain rates from 10−1 to 10−7 reciprocal seconds was examined. The J integrals at the initiation of the cracks were determined. This enabled the interrelationship between fracture initiation and the test rate to be established. The dependency follows a power law relation. The values of the exponents in the power law equations, derived from experiment, were found to be higher than the values calculated using established criteria for crack initiation. The difference is postulated to be due to the strengthening of the fibrils ahead of the crack because of the orientation of the fibrils in that region.