bluuebunny/crossref_metadata_2025_split huggingface dataset:
Further rapidly reacting ion‐exchange resins
Authors: Bolto B. A. , Siudak R. V. 
Published: June 2010

AbstractTo overcome the very slow reaction rates of weak electrolyte ion‐exchange resins in neutral salt solutions, the resins must be used as microparticles. Ways of handling microparticles are outlined. The present study is aimed at the preparation of large composite particles containing basic and acidic polymers in domains which are clearly segregated so that minimum interaction between the sites of opposite character occurs. Because the domain size is small, rapid reaction rates are achieved. Resins which show this effect have been prepared from basic and acidic monomers by using blocking procedures involving counterions, which significantly reduce the association of the basic and acidic sites. However, although very rapid reaction rates are obtained, the ion‐exchange capacities of the products remain inferior to those of composites made by binding the active microparticles together with an inert binder, showing that substantial self‐neutralization has still taken place. Similar results are obtained with basic and acidic monomers by using precipitation techniques, which are aimed at grafting one monomer onto a precipitated macroradical prepared from the other monomer.
Thermogravimetric studies of polymethylenes and polyethylenes
Authors: Mucha Maria 
Published: June 2010

AbstractSeven samples of polymethylene prepared during polymerization of diazomethane having different initial molecular weights and five samples of polyethylene (Lupolen type) having a different number of branches were studied by thermogravimetric analysis using Freeman Carrol's and Fuoss's methods to determine the number of CH3 groups per 1000 carbon atoms. The calculated activation energies reflect the effect of both molecular weight and the number of branches on the thermal stability of the polymer. Activation energy values decrease with the lowering of the molecular weight Mv of the polymethylene sample. This decrease of Mv occurred during the initial etching of the sample in fumic nitric acid. The activation energies of the branched polyethylenes decrease with the increase of the number of branches. Thermal stability of branched polyethylenes is lower than that of linear polyethylene.
Thermal oxidative stabilization of radiation‐crosslinked polyethylene‐ethylene propylene rubber blends
Authors: Kammel G. , Wiedenmann R. 
Published: June 2010

AbstractThe influence of co‐ and termonomers on the thermal‐oxidative stability of radiation‐crosslinked stabilized polyethylene‐ethylene propylene rubber (PE/EPR) blends is discussed. For these investigations the selected criteria were the induction period in the oxygen‐uptake test and the resulting mechanical properties after oven‐aging at 135°C.From the experiments it has been concluded that the addition of only a small portion of EPR containing 5% dicyclopentadiene (DCP) as termonomer greatly reduces the protection against aging as compared to low density polyethylene. The protection against aging for those blends containing the tercomponent 5‐ethylidene‐2‐norbornene (EN) was found to be (up to a ratio of 80% EPDM (EN)) above the values obtained for PE/EPM blends. In this connection the influence of the polymeric antioxidant 2,2,4‐trimethyl‐1,2‐dihydroquinoline on the degree of crosslinking will be considered.
Photochemical decomposition of cyclohexadienone peroxides
Authors: Lind H. , Winkler T. , Loeliger H. 
Published: June 2010

AbstractPhotolysis products of 4‐t‐butyl‐peroxy‐4‐methyl‐2, 6‐di‐t‐butyl cyclohexadienone have been identified and a mechanism of their formation is given.
Some effects of morphology on oxidation and stabilization of polyolefins
Authors: Billingham N. C. , Prentice P. , Walker T. J. 
Published: June 2010

AbstractPrevious work on the effects of crystallinity on the autoxidation of polyolefins is briefly reviewed and shows that polyethylene and polypropylene oxidize exclusively in the amorphous phase. Measurements of the rate of oxidation of poly(4‐methyl pentene‐1) (P4MP) show that the oxidation is first‐order in oxygen pressure over a wide range of film thickness, oxygen pressure, and oxidation temperature. A simple model of diffusion followed by chemical reaction fits the data very well. Values of the diffusion coefficient for oxygen and of its activation energy, calculated from oxidation data, agree well with experiment.It is shown that increased initial crystallinity increases the oxidation rate of P4MP, while the crystallinity of the polymer decreases markedly during oxidation. These results imply that P4MP oxidizes extensively in the crystal phase.Ultraviolet microscopy shows that typical stabilizer molecules are rejected from the crystal phase of P4MP; comparison of oxidation induction periods in polypropylene and P4MP, containing antioxidants, supports the view that the effectiveness of stabilizers in P4MP is markedly reduced by rejection from the crystal phase.
Some oxidation characteristics of polypropylene
Authors: Frank H. P. 
Published: June 2010

AbstractOxidation and corresponding oxidative degradation of polypropylene was studied under varying conditions. Thermal oxidation in the melt (processing stability) was followed by multiple extrusions, by determining the induction period for oxygen take‐up (165–220°C) and the rate of oxygen take‐up. Various antioxidants of the sterically hindered phenol type were used in these experiments. Long term thermal oxidation (150°C oven aging) was carried out over a period of 400 hr and followed by determining polymer properties ([ζ], density, etc.), antioxidant concentration, and antioxidant decomposition products. Analogous tests were performed after exposing the polymer samples up to 1000 hr to boiling water. In photooxidation (xenon lamp, Spectrotest) the most effective wavelength range in the near UV was found to be at about 312 nm; but even at 378 nm a small photodegradation effect can be observed. The solubility of various additives (antioxidants and UV‐stabilizers) was determined in amorphous polypropylene, but reliable results were obtained for tetrakis [methylene 3‐(3′,5′‐di‐tert‐butyl‐4‐hydroxyphenyl)‐propionate] only (temperature range 100–200°C).
Influence of the arrangement of the crystals and the structure of the noncrystalline regions on the mechanical properties of polyethylene terephthalate
Authors: Biangardi H. J. , Zachmann H. G. 
Published: June 2010

AbstractAmorphous samples of polyethylene terephthalate were stretched with different rates and stretching ratios at different temperatures. Afterwards they were crystallized. The arrangement of the crystals and the conformations of the chains in the noncrystalline regions were investigated by means of X‐ray wide‐angle scattering, X‐ray small‐angle scattering, birefringence measurements and nuclear magnetic resonance measurements. The influence of the morphological structure on the mechanical strength was determined. The stretching ratio itself generally does not characterize the orientation state. The structure obtained after crystallization depends mainly on the birefringence of the sample after stretching before crystallization. With increasing birefringence one obtains all intermediate structures starting from the well known spherulites composed of twisted lamellae in the unoriented material up to a paracrystalline lattice of lamellae split up into mosaic blocks in the highly oriented state. Also the conformations of the chains in the noncrystalline regions are influenced by the stretching. With increasing orientation the amount of tie molecules with comparatively large end‐to‐end distances becomes larger. The improvement of the mechanical properties with stretching is caused not only by the increasing orientation of the molecules but also by the increasing amount of taut tie molecules.
Peculiarities of supermolecular structure of polyimides and polyester imides
Authors: Sidorovich A. V. , Baklagina Yu. G. , Kenarov A. V. , Nadezhin Yu. S. , Adrova N. A. , Florinsky F. S. 
Published: June 2010

AbstractSupermolecular structures of fourteen heterocyclic thermally stable polymers of the polyimide (PI) and polyesterimide (PEI) class have been investigated by X‐ray scattering, optical, dilatometric and thermomechanical methods. Quasi‐crystalline structure of these polymers in the initial amorphous state of poly(amic acid) and poly(ester amic acid) and also after chemical imidization has been revealed. The quasi‐crystalline structure is characterized by a biaxial polarizability ellipsoid with a negative sign. This is indicated by distinct conoscopic figures recorded with a polarizing microscope. The effect of the number of oxyphenylene groups on the crystallizability of PI and PEI was investigated. For PEI the effect of self‐orientation of macromolecules induced by conformational transition was observed. Discrete small‐angle x‐ray scattering pattern (a long period) was also revealed for PEI. The appearance of long periods is caused by polymorphism of PEI uniquely determined for one of its types (PEI‐II). X‐ray scattering data confirmed by calculations of the lattice energy show that dianhydride pyromellitimide chain portion is the element determining the crystalline structure of PI. The structure is determined by van der Waals' forces and obeys the principle of dense packing. This leads to the appearance of layer structure with alternating layers of diamine and dianhydride portions. It was found that, depending on the rigidity of the diamine portion, PI and PEI exhibit different abilities of forming axial‐planar or axial textures in nonoriented films.
Excess volume and effect of pressure on the critical temperature
Authors: Onodera M. 
Published: June 2010

AbstractThe asymptotic method was applied to polymer solutions. The configurational partition function based on the lattice model was much improved by introducing free volumes into consideration. Consequently we were able to calculate the fractional volume change on mixing as the mean value through use of the configurational partition function, under the assumption of pairwise additivity of volume of mixing. The derived expression for the excess volume of mixing was compared with experimental results. Gibbs free energy was derived from Helmholtz free energy and the product of the volume of mixing and pressure, from this the critical pressure‐dependent composition and temperature was obtained. Thus we have the relation between pressure and critical temperature. The data are displayed figures that it might be compared with experimental results.
Entropy correlation theory and diffusion measurements for oriented polymers
Authors: Barker R. E. , Tsai R. C. , Willency R. A. 
Published: June 2010

AbstractThe entropy correlation theory predicts that any structural change which decreases the configurational entropy Sc of a complex molecular system will lead to an approximately equal increase in the activation entropy ΔS* for structurally controlled rate processes such as diffusion. In symbols, Δ(ΔS*) =‐ΔSc or ΔS*(A) = ΔS*(1)‐ΔSc, where, in the present case, the ordering parameter A is the elongation ratio L/L0. Although the theory is believed to be of wider scope, this paper deals with its confirmation for the case of gas diffusion in permanently stretched polymeric membranes. The systems investigated included representative poly(alkyl methacrylates) (viz. methyl, ethyl, isobutyl, and normal butyl methacrylate and a copolymer), and a selection of nonpolar and polar gases (Ar, O2, N2, CO). Diffusion and permeation measurements on the oriented films were made by the Daynes‐Barrer time lag method using a mass spectrometer for the detection instrument. The degree of orientation and its stability during an experiment were characterized by measurements of optical birefringence. For a comparison of the general theory with the specific data, it was found useful to prepare the samples in such a way that ΔSc ≈ a(A2 + (2/A)–3, corresponding to a quenched elastomer; then the data could be represented such that log DO is a linear function of ΔSc, where DO is the preexponental factor in the diffusion equation D = DO exp (‐ED/RT).
Properties of some rodlike polymers in solution
Authors: Wong C.‐P. , Ohnuma H. , Berry G. C. 
Published: June 2010

AbstractThe properties of poly (1, 4‐phenylene terephthalamide) (PPTA), Kevlar, and a poly(benzobisoxazole) (PBO) in solution are investigated. Molecular characterization using light scattering and viscometry on dilute solutions shows PBO and PPTA to have a rodlike conformation. Both are prone to interchain aggregation with the tendency for association apparently increasing with the ionic strength of the solvent. Rheological experiments are reported on disordered and ordered concentrated solutions of Kevlar and PBO. The dependence of the viscosity and recoverable compliance on shear rate is discussed and compared with that of flexible‐chain polymers. The dependence of the viscosity and recoverable compliance of PBO solutions on temperature and concentration is discussed.
Complex formation between poly(vinyl‐pyrrolidone) and poly(itaconic acid monomethylester) or its copolymer
Authors: Bimendina L. A. , Bekturov E. A. , Tleubaeva G. S. , Frolova V. A. 
Published: June 2010

AbstractComplex formation in poly(vinylpyrrolidone)‐poly(itaconic acid monomethylester) and poly(vinylpyrrolidone)‐copolymer of maleic anhydride and monomethylitaconate systems has been investigated. It is shown that the interpolymer complexes are formed at interaction of macromolecular components. Data of conductometric, potentiometric, and viscometric titrations indicate that the molar composition of complexes is PVP:PMMI = 1:1 and PVP:MA/ MMI = 3:2. The complex particles are very compact with the intrinsic viscosity in water about 0.05‐0.10 dl/g not depending upon the molecular weight of polymer components. Complexes are destroyed both by inadequate organic solvent (30‐40 vol %) in mixed solvent water ‐dimethylsulfoxide, and by thermal action.
Fluorescent labeling of soluble polymers
Authors: Rypáček F. , Drobníak J. , Krejčoves J. , Kálal J. 
Published: June 2010

AbstractPossibilities of polymer‐analogous labeling of soluble polymers with covalently bound fluorochrome in the side chain were investigated, using N(2‐aminoethylcarbonyl)‐5(6)‐aminofluorescein (I), 4‐aminomethyl‐7‐hydroxycoumarine (II), and fluoresceinisothiocyanate (FITC) as labels. The properties of polyaspartamides labeled with I and FITC were compared with regard to their bond stability and intensity of fluorescence.
Localized combined chemotherapy of solid gardner lymphosarcoma by methotrexate bound to synthetic polymeric carriers
Authors: Motyčka K. , Slavíková V. , Špaček P. , Kubín M. , Slavík K. 
Published: June 2010

AbstractA chemically modified poly‐2‐hydroxyethyl methacrylate was used as a carrier of methotrexate and 3′,5′‐dibromoaminopterin. Intratumorously implanted carrier with graded doses of sorbed methotrexate has prolonged the survival of treated mice. Best results were achieved if toxicity of higher doses of sorbed methotrexate was reversed by leukovorin. Increased toxicity and decrease of the survival time and of the detoxicating potency of leukovorin were found if using an advanced experimental tumor. A promising result in mice with advanced tumors by using sorbed 3′,5′‐dibromoaminopterin is reported.
Dependence of albumin–fibrinogen simple and competitive adsorption on surface properties of biomaterials
Authors: Brash J. L. , Uniyal S. 
Published: June 2010

AbstractAdsorption of fibrinogen and albumin from solutions of the proteins singly and in mixtures was studied. A variety of surfaces with varying degrees of hydrophilicity and thrombogenicity was investigated. Adsorption behavior shows a strong dependence on surface properties. All surfaces show a preference for fibrinogen, and the degree of preference appears to correlate with thrombogenic tendency and platelet reactivity.
The hydrolysis of α‐N‐benzoyl‐L‐arginine ethyl ester by monolayers of papain and trypsin
Authors: Graham N. B. , Novosel B. 
Published: June 2010

AbstractThe hydrolysis of α‐N‐Benzoyl‐L‐arginine ethyl ester (BAEE) as a substrate under monolayers of papain and trypsin at the air–water interface was studied using an automated Lauda film balance to characterize the monolayers and a small resin‐flask reactor with movable barriers for surface‐layer compression. The rates of reaction were followed by UV spectrophotometry. The hydrolysis rate increased with moderate increases in surface pressure and temperature.
Metal‐catalyzed oligomerization reactions of organosiloxanes
Authors: Curtis M. David 
Published: June 2010

AbstractTransition metal complexes, e.g., L2Pt(C2H4), L3RhCl, and L2Ir(CO)Cl (L = Ph3P), react with tetraalkyldisiloxanes, (HRR'Si)2O, to produce metallacycles featuring the transition metal, two silicons, and the oxygen in a four‐membered ring, MSiOSi. When R = Me and R' = Ph, stereoselectivity in the formation of the metallacycle from a mixture of stereoisomers of the starting disiloxane is observed. The catalytic activity of these complexes for the oligomerization of the disiloxanes has been investigated in the hope of obtaining stereoregular silicones. It has been found that extensive rearrangements occur which redistribute the groups on the silicon atoms. Increased selectivity for the desired exchange type (SiO groups for Si — H) was found when the catalysts were adsorbed on oxide supports. Although the goal of synthesizing stereoregular silicones has not yet been achieved, the results warrant further investigation.
Heat capacity of water absorbed in methylcellulose
Authors: Kinard D. A. , Hoeve C. A. J. 
Published: June 2010

AbstractThe heat capacity of methylcellulose is determined at various water contents over a wide range of temperatures, down to 125 K. From the data, the partial specific heat capacity of water has been obtained. The results show that water should be considered as a single, mobile phase. No evidence exists for bound water. Near 130 K water becomes immobilized in a glassy state.
Underwater stress relaxation studies of nafion (perfluorosulfonate) ionomer membranes
Authors: Kyu Thein , Eisenberg Adi 
Published: June 2010

AbstractIn an effort to elucidate the nature of ionic aggregation and its effect on the primary relaxation (α process) in the Nafion polymers (EW = 1200), underwater and undermethanol stress relaxation tests were conducted at various temperatures (20–70°C). Both semicrystalline and amorphous Nafion‐Na relax faster in the presence of water than in the dry state. In marked contrast to the behavior observed for Nafions in the dry condition, the kind of countercations is insignificant in the underwater stress relaxation. The great similarity in the underwater stress relaxation curves for different cations is attributable to the reduction of ionic interaction between the bound anions and unbound cations, probably associated with the water shielding around the ionic species. This leads to the suggestion that the primary α relaxation may be relevant to the ionic groups rather than to the matrix Tg, representing a reversal of the original assignment of the mechanical α and β relaxations. Increased swelling in methanol shows a modulus being one order of magnitude lower than that in the underwater runs. However, little or no difference is seen in the rates of stress relaxation in the underwater and undermethanol stress relaxation experiments. It is postulated that methanol also interacts with the interracial regions or with the fluorocarbon matrix in the Nafions, not just with the ionic regions.
Confinedrandom‐flightpolymerchainsinsolution: exclusion from micropores and distribution near barriers
Authors: Casassa Edward F. 
Published: June 2010

AbstractThe statistical basis of the entropic repulsion of dissolved random‐flight polymer chains from impenetrable passive barriers is described. The application of these ideas to the partial exclusion of linear and branched polymer chains from micropores and to the polymer concentration profile near a barrier is reviewed with emphasis on the mean projection of the chain as a measure of the exclusion effect.
Kinetics of particle nucleation and growth in the emulsion polymerization of acrylic monomers
Authors: Fitch Robert M. , Palmgren Tor H. , Aoyagi Tatsuhiro , Zuikov Aleksander 
Published: June 2010

AbstractThe rates of particle formation and growth during the earliest stages of the emulsion polymerization of several acrylic monomers have been studied as a function of surfactant concentration by means of the time‐dependence of light scattering from the reaction mixtures. Investigated were methyl methacrylate, and methyl, ethyl, and butyl acrylates at concentrations of SDS surfactant from zero to several times the CMC. Under continuous photoinitiation, the Rayleigh scattering intensities rose rapidly with slopes that increased with decreasing SDS concentration. The more water‐soluble the monomer, the more slowly was the rate of increase in scattering intensity.
Some evidence for the existence of the liquid‐liquid transition: Melt rheology studies
Authors: Maxwell Bryce , Cook Kevin S. 
Published: June 2010

AbstractIn 1963 Boyer proposed the existence of a liquid‐liquid transition, Tll, in polystyrene above the glass transition Tg. Since that time there has been considerable discussion and disagreement on the existence of this transition. Detailed shear modulus data as a function of temperature in the range 165–215°C will be presented for a series of polystyrenes of various molecular weights. In each case, as the temperature is increased, the modulus gradually decreases until a specific molecular weight dependent temperature is reached and then suddenly the modulus decreases rapidly over a few °C and then returns to its previous gradual decrease with increasing temperature. The response is reminiscent of the modulus behavior going through Tg. It is suggested that the temperature at which this sharp decreased in modulus takes place is Tll. The molecular weight effects on Tll will be discussed in terms of several rheological properties that measure the temperature of this transition.
Dynamics of rodlike macromolecules in semidilute solutions
Authors: Pecora R. 
Published: June 2010

AbstractExperimental data on the rotation and translation of rigid rod macromolecules in the semi‐dilute region are discussed in the terms of the Doi‐Edwards theory. Available data indicate that the rotational diffusion coefficients vary approximately as the inverse concentration squared and the inverse length to a power between 7 and 8. The absolute value of the decrease of the rotational diffusion coefficient in the semidilute region relative to the infinite dilution value is about two orders of magnitude less than is predicted by the Doi‐Edwards theory. Some possible explanations for these deviations include:
The constraints on diffusion imposed in the Doi‐Edwards theory are too severe even for rigid rods.
The molecules studied exhibit some flexibility and thus do not conform to a model for rigid rods.