bluuebunny/crossref_metadata_2025_split huggingface dataset:
Relation between the compression yield stress of poly(vinyl chloride) and the loss peak in the β‐transition range
Authors: Bauwens J.‐C. 
Published: June 2010

AbstractPreviously we have shown that the study of the tensile yield stress of glassy polymers over a wide range of temperatures and strain rates as well as measurements of mechanical losses is of use in revealing secondary transitions.We report here the correlation between the shape of the β loss peak of poly(vinyl chloride) (PVC) (loss tangent versus temperature at a given frequency) and the yield stress curve (yield stress in compression versus temperature at a given strain rate), on the assumption that the broadness of the β peak is due to an activation energy spectrum around the classical value (14 kcal/mole) associated with this transition.Because in tensile tests PVC fractures before yielding in the transition temperature range, we have chosen compression tests to investigate this whole range.An equation is given relating the transition conditions in tensile or compression tests to the transition conditions in damping tests. The theory predicts that the double integral of the β peak must be proportional to the increase of the yield stress due to the transition; the theoretical curve is calculated and is found to fit the experimental data fairly well.
Rheological studies of chlorinated poly(vinyl chloride)
Authors: Krishnan M. , Gupta V. B. , Thampy R. T. , Kothari A. V. 
Published: June 2010

AbstractChlorinated poly(vinyl chloride) (CPVC) is known to have a higher softening temperature than conventional poly(vinyl chloride) (PVC). Its processability characteristics are, however, different; and in the literature, it has been reported that CPVC is more difficult to process. However, no detailed characteristics of its processability appear in the current literature. This paper describes some of the studies we have made on the flow behavior of CPVC.Investigations on the melt properties of CPVC, made on a capillary rheometer, indicate that above 67% chlorine content the resin shows gross distortion of the extrudate even at low stresses. This “melt fracture” phenomenon might arise from the elastic nature of the melt. The simple treatment of the flow data, based on a modified form of Poiseuille equation for capillary flow, gave no direct evidence for the increased elasticity of the melt. The limitations of the assumptions made in the simplified treatment may be responsible for this.It is proposed that the elasticity of the melt can arise from the crosslinks produced in the melt due to dehydrochlorination, which is known to increase with increasing chlorine content. It is also suggested that modification of the simple approach to capillary flow might give a better idea of the elastic nature of the melt.
Poly(vinyl chloride) with thrombus‐inhibiting properties
Authors: Buadze O. P. , Gegeshidze G. A. , Lakin K. M. , Nazin A. N. , Zhuravleva E. N. 
Published: June 2010

AbstractThe preparation of a polymer on the basis of suspension polyvinyl chloride resin with various chemical combinations offering anticoagulant effects on the blood is considered. As a result of many experiments, a material has been obtained which during its prolonged contact with blood reduces clotting thus preventing the thrombus formation. This gives us a base for preparing vascular catheters, substitutes for vascular conduits and various tubes for an extracorporal blood‐circulation apparatus as well as test‐tubes and vessels for taking and storing blood without the danger of clotting. A reliable extension of clotting time of blood under a continuous contact with the given polymer has been proved experimentally.
Compatible poly(vinyl chloride) vascular catheters
Authors: Gegeshidze G. A. , Buadze O. P. , Nazin A. N. , Zhuravleva E. N. , Shmyreva T. A. 
Published: June 2010

AbstractThe results of comparative investigations of polyethylene and specially developed polyvinyl chloride vascular catheters during their continuous implantation into the blood vascular system of the experimental animals are presented. An analysis of the experimental data allows to identify a certain regularity in the development of essential complications resulting from various physico‐chemical properties of the above‐mentioned polymeric materials. The prolonged presence of the polyethylene catheters in dog's magistral vessels was succeeded by a mass process of thrombo formation in the early period just after implantation and by an aneurysmal injury of the vessel walls occurring in the remote period that hindered a continual use of the catheters. The application of specially developed polyvinyl chloride compositions for the production of catheters possessing a higher elasticity and an inertness to the physiological tissue allowed the above‐mentioned complications to be suppressed completely and the presence of the catheters in the vascular bed of the experimental animals to be prolonged up to one year, and in the clinical practice up to one month. A continuous application of the polyvinyl chloride catheters enables a complex investigation of the function of the cardiovascular system to be carried out, and the process of specified pharma‐cotherapy and multiple analysis of blood to be simplified.
Thermomechanical degradation of poly(vinyl chloride)
Authors: Andersson Kent B. , Sörvik Erling M. 
Published: June 2010

AbstractThe thermomechanical degradation of stabilized and unstabilized poly (vinyl chloride) (PVC) has been investigated by use of a Brabender Plastogiaph. All degraded samples were analyzed by gel permeation chromatograph (GPC) and some of them were studied by infrared measurements and viscometry. The association of PVC molecules seemed to affect the GPC measurements for weight average molecular weights exceeding about 70,000. The heat treatment of solutions of degraded PVC before fractionating by GPC was very important in order to obtain real values of Mw.After the degradation point was reached, the Ba‐Cd stabilized samples showed a faster increase in Mw than the Sn stabilized or the unstabilized samples did.The emulsion polymer had not as good stability as the corresponding suspension polymer, presumably due to its larger content of remaining polymerization additives. No noticeable chain scission occurred for the low molecular weight PVC, PEVIKON R‐150. This polymer also showed a very slow increase in Mw when treated without any stabilizer. The average number of trifunctional branch units per molecule was found to be only 0.3 for PEVIKON R‐150 and 0.5 for PEVIKON R‐341, but increased during the degradation. The agreement between the results from the GPC, viscometry, Brabender tests, and the infrared measurements are excellent.
Theory of polymer adsorption at interfaces
Authors: Hoeve C. A. J. 
Published: June 2010

AbstractPrevious theories valid for polymer chains with large loops protruding into the solvent are developed. Interaction in various layers parallel to the interface is calculated according to the Flory‐Huggins theory. Excluded volume effects are shown to be so small that they can be neglected. The adsorption isotherm is expressed in two parameters: one for the partition function for adsorbed segments and the other one for the stiffness of the chains. For adsorption from good solvents, the fraction of segments in the surface layer is large and the loops are small. For adsorption from theta‐solvents, the fraction of segments in the surface layer is small and the loops are large. The trends are in agreement with those experimentally observed, but the observed layer thickness is larger than the theoretically deduced upper limit.
Calculation of interfacial tension in polymer systems
Authors: Wu Souheng 
Published: June 2010

AbstractWe propose an equation, based on “reciprocal” mean and force additivity, for calculating the interfacial tension between polymers or between a polymer and an ordinary liquid:

where γ12 is the interfacial tension; γi the surface tension; γ and γ the dispersion and polar components of γi, respectively. This equation is shown to predict accurately the interfacial tension between polymers or between a polymer and an ordinary liquid. Fowkes' equation or Fowkes' equation with a geometric‐mean polar term 2(γiPγ2p)1/2 is not applicable to polarlpolar systems. The interfacial tension arises mainly from disparity in the polarities of the two phases. The above equation can also be used to calculate the surface tension and polarity of polymers or organic solids from contact angle data.
Surface tension of mixtures of oligomers
Authors: Legrand D. G. , Gaines G. L. 
Published: June 2010

AbstractThe surface tension of mixtures of poly(dimethylsiloxane) and poly(isobutylene) fluids with their low molecular weight oligomers have been measured. These data, as well as those for n‐alkane mixtures from the literature, are fitted well by lattice‐theory expressions for the surface tension of polymer solutions, and do not show a simple dependence on the average molecular weight in the mixture. We conclude that the molecular weight depend‐ence we have previously observed for the surface tension of polymer fluids is only an approximation. The results also suggest that the lattice‐model theory may have broader applicability than the model from which it was developed would imply.
Studies of synthetic polypeptide‐water interactions using monolayer techniques
Authors: Malcolm Benjamin R. 
Published: June 2010

AbstractMolecular monolayers of a range of synthetic polypeptides spread at the air‐water interface have been investigated. Measurements of the surface pressure and surface potential are correlated with the chemical composition of the side chains. All the polymers are believed to be in the α‐helical conformation at the air‐water interface and the surface potential is accounted for principally by the interaction of the peptide groups with the underlying water; if however, there are ester groups in the side chains, an additional side chain‐water interaction is evident. The infrared absorption spectrum of water and alcohols adsorbed from the vapor on thick orientated specimens in the α‐helical conformation prepared from collapsed monolayers has also been investigated. The OH absorption of water, methanol and ethanol is dichroic and shows evidence of interactions similar to those required to account for the surface potential.
Monomolecular films of poly [methyl(n‐alkyl)siloxanes] on organic liquids
Authors: Jarvis N. L. 
Published: June 2010

AbstractA series of poly [methyl(n‐alkyl)siloxanes] were studied as insoluble monomolecular films on the following organic substrates: tricresyl phosphate, propylene carbonate, diethyl phthalate, and a highly chlorinated polyphenyl (Aroclor 1242). The siloxanes were discovered to form stable, insoluble, reproducible monomolecular films at each organic liquid/air interface. Film pressure (F) vs. area/molecule (A) isotherms were determined in each instance and were compared with previously determined F‐vs.‐A isotherms for polydi‐methylsiloxanes on the same organic substrates as well as on water. By combining the film balance data with molecular dimensions calculated from ball models, it was possible to make several tentative conclusions regarding the conformation of the adsorbed siloxane molecules as a function of film pressure, n‐alkyl chain length and substrate composition. The F‐vs.‐A curves for the poly(methylethylsiloxane) and polydimethylsiloxane films were consistent with the assumption that they assume a helical configuration when compressed at organic liquid/air interfaces; however, there is little evidence to indicate whether the polymer chains become fully extended at higher areas/molecule or remain in a somewhat coiled configuration.
Adsorption of lysozyme and some acetyl derivatives at the air‐water interface
Authors: Adams D. J. , Evans M. T. A. , Mitchell J. R. , Phillips M. C. , Rees P. M. 
Published: June 2010

AbstractAn examination was made of adsorbed and spread films of lysozyme and a series of its acetyl derivatives at the air‐water interface. Direct observations of adsorption and desorption were carried out by measuring the surface pressure and surface radioactivity of films of native and heat‐denatured 1‐14 C‐acetyl lysozyme. Acetylation of as little as one residue per molecule significantly alters the surface properties of lysozyme. Films of lysozyme derivatives spread on low ionic strength buffer give pressure‐area isotherms which are less expanded than those obtained on concentrated salt solutions because in the former case protein is lost to the subphase. The isotherms of native and heat‐denatured protein‐films spread on 3.5 M KC1 are independent of the degree of modification and compression rate and no desorption occurs. Pressure‐area isotherms of adsorbed films show that a low subphase concentration gives rise to a film containing extensively unfolded molecules, while higher concentrations lead to the formation of a film of higher surface concentration containing incompletely unfolded molecules. Spread protein films generally contain more completely unfolded molecules than adsorbed films and more expanded interfacial films are obtained when heat‐denatured molecules adsorb than when native molecules adsorb from solutions of the same concentration.
Effect of adsorbent on the adsorbed structure of poly (methyl methacrylate)
Authors: Thies Curt 
Published: June 2010

AbstractIsotherms and infrared bound fraction values (p) have been obtained for atactic poly‐(methyl methacrylate) (PMMA) adsorbed from trichloroethylene (24°C) on four adsorbents: aluminum oxide (γ‐AI2O3) formed by flame hydrolysis, micro‐fine reprecipi‐tated silica, silica formed by flame hydrolysis, and silica formed by flame hydrolysis and then reacted on the surface with dimethyl dichlorosilane. Differences in PMMA adsorbance values obtained with these adsorbents may be attributed in part to differences in surface area available for adsorption per gram adsorbent. However, variations in surface area do not account for variations in adsorbed structure indicated by the infrared bound fraction data. PMMA adsorbed on silica treated with dimethyl dichlorosilane had a value of p ≈0.10; p increased to 0.32–0.39 when untreated flame hydrolyzed silica was the adsorbent, and ranged from 0.46 to 0.49 for micro‐fine reprecipitated silica. PMMA adsorbed on γ‐AI2O3 had p = 0.32–0.28. This was the only adsorbent where values of p tended to decrease with increasing surface coverage. The variations in bound fraction data found in this study are interpreted in light of known differences in surface structure of the four adsorbents used. Drying the reprecipitated silica and γ‐AI2O3 at 310°C (in vacuo) caused a slight decrease in values of p which can also be explained in terms of known changes in surface structure caused by heat treatments.
Polymer adsorption studies at the solid/liquid interface using gel permeation chromatography. II. Influence of molecular weight on the adsorption of poly(vinyl chloride) from chlorobenzene onto calcium carbonate
Authors: Felter R. E. 
Published: June 2010

AbstractAdsorption of both high molecular weight (M̄w = 114,000) and low molecular weight (M̄w = 42,800) poly(vinyl chloride) resins were followed from chlorobenzene solution onto CaCO3 at room temperature, and compared with data obtained previously for an inter‐mediate molecular weight resin (M̄w = 80,600). At increase in the adsorption saturation capacity (ASC) was observed for increasing M̄w (31.6 mg‐g−1 to 41.7 mg‐g−1) as was a corresponding decrease in the number of molecules adsorbed (9.0 × 10−7 mol‐g−1 to 6.3 × 10−7 mol‐g−1). Preferential adsorption of high molecular weight polymer was noted for all resins. The average molecular weight of polymer adsorbed at ASC increased with increasing M̄w. Fractionation of the adsorbed polymer was also evident and improved with decreasing M̄w. Within the molecular weight distribution (MWD) of all three resins an increase in the amount of polymer adsorbed (described by an adsorption efficiency factor) with increasing molecular weight occurred up to a molecular weight near 75,000. Above a molecular weight of 75,000 the adsorption efficiency factor continued to increase with the low molecular weight resin but stayed fairly constant for the intermediate and high molecular weight resins. Competition of high molecular weight polymer for surface sites was cited as an ex‐planation. The polymer molecules were thought to adsorb as interpenetrating or compressed coils with relatively few points of surface contact.
Numerical interconversion of viscoelastic functions by linear programming
Authors: Shen Mitchel , Jamieson Ronald T. , Drandell Milton 
Published: June 2010

AbstractInterconversion of viscoelastic functions are customarily accomplished through the use of distribution of relaxation or retardation times. It will be shown that, by employing the Linear Programming (LP) technique, numerical interconversion may be obtained directly. As an example, starting with stress‐relaxation moduli E(t) of polyisobutylene, values of E′(ω), E″(ω), D″(ω), D(t), Dg, and ω of this polymer are obtained. Agreement with experimental data in the literature is found to be excellent. Calculated values are given in the form of upper and lower bounds of the functions, indicating a probable error margin of the computed values. The calculations are performed by standard LP routines, requiring little computer background of the user. Thus LP is a simple and general technique for calculating any viscoelastic function from any other given set of data.
Chemo‐rheology of curing in structural adhesives. II. Polyimide systems
Authors: Kaelble D. H. , Cirlin E. H. 
Published: June 2010

AbstractPolyimide adhesives are cured through the cyclization of the linear main chain of the polymer, rather than through the formation of a network structure. It was found that the average activation energy E* for the imidization process of the curing is 30.5 ± 5.4 kcal/mole and is substantially higher than that of the epoxy‐phenolic adhesive system which we have reported in Part I. The effect of metal filler upon the curing kinetics and mechanical properties of cured material is discussed on the basis of TMA and DSC measurements. In addition, the influence of moisture exposure on the tensile modulus E of the polyimide adhesives are also discussed.
Dynamic mechanical behavior of partially hydrolyzed ethylene‐vinyl acetate copolymers
Authors: Macknight William J. , Tetreault Roland J. 
Published: June 2010

AbstractA dynamic mechanical study has been made of two series of partially hydrolyzed ethylene‐vinyl acetate copolymers. Series A contains 75 mole % ethylene and series B contains 59 mole % ethylene. The frequencies employed were 3.5, 11, and 110 Hz, and the temperature range was from −180° to +120°C. Three relaxation regions are discernable in this range and these are labeled α, β, and γ in order of decreasing temperature. The α relaxation is associated with the glass transition of the copolymers. The β relaxation is absent in the unhydrolyzed copolymers and is dependent on hydroxyl content. It is assigned to local motions of hydrogen bonded groups. The γ relaxation is insensitive to hydroxyl content and is assigned to local motions of methylene sequences. The above assignments are supported by the effect of water added to the polymers. Added water decreases the temperatures of the α and β relaxations but does not affect the γ relaxation significantly. The magnitude of the β relaxation is considerably enhanced by water.
Shear rate dependent relaxation spectrum for polyethylene melts
Authors: Shroff Ramesh N. , Shida Mitsuzo 
Published: June 2010

AbstractMany of the familiar relations in the theory of linear viscoelasticity which relate the relaxation spectrum H(τ) to the experimentally measured quantities were extended to embrace the concept of shear dependent relaxation spectrum H(τ, \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \gamma \limits^ $\end{document}). The concept is based on the relation H(τ, \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \gamma \limits^ $\end{document}) = H(τ)h(θ)g(θ)3/2, where θ = c \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \gamma \limits^ $\end{document} τ and c = 0.5. Here \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \gamma \limits^ $\end{document} is the shear rate and τ is the relaxation time. The replacement of H(τ) by H(τ',\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \gamma \limits^ $\end{document}) in the integral relations of the linear theory produced the corresponding nonlinear parameters, e.g., the shear rate dependent viscosity η(\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \gamma \limits^ $\end{document}), the shear stress relaxation following cessation of steady‐state flow σ(\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \gamma \limits^ $\end{document},t) and the dynamic parameters under parallel superimposed rotation η'(ω) and G'(ω, \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \gamma \limits^ $\end{document}). The concept was used successfully for several high‐density polyethylene melts in interconversion between η(\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \gamma \limits^ $\end{document}), c(\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \gamma \limits^ $\end{document},t) and the dynamic viscosity η'(ω) without involving coordinate shifts or empirical parameters. The failure of this approach for interconversion between η(ω) and η(\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \gamma \limits^ $\end{document}) for the highly branched polyethylenes was ascribed to the level of long‐chain branching. For the high‐density resins, the agreement between measured η'(ω,\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \gamma \limits^ $\end{document}) and G'(ω,\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \gamma \limits^ $\end{document}) and those calculated using H(τ,\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \gamma \limits^ $\end{document}) was not quantitative since the parallel superimposed experiments require an additional term in ∂H(τ,\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \gamma \limits^ $\end{document})/∂ \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \gamma \limits^ ^2 $\end{document} inside the integral.
Thermal behavior of carbohydrates
Authors: Shafizadeh F. 
Published: June 2010

AbstractThermal analysis of a hardwood reflected the pyrolysis of its main components including xylan and cellulose. Thermal properties of these components were investigated with model compounds consisting of α‐D‐xylose, substituted phenyl β‐D‐xylopyranosides, β‐Dglucopyranosides and α‐D‐arabino‐hexopyranosides and 1,6‐anhydro‐β‐D‐glucopyranose.At the lower temperatures these molecules displayed anomerization, loss of water and phase change, which were studied with a variety of physical methods. Calorimeteric and wide line NMR measurements showed that 1,6‐anhydro‐β‐D‐glucopyranose and related anhydro sugars undergo plastic crystalline transition, involving reorientation of the molecules about their centers of gravity and self‐diffusion before melting.At more elevated temperatures the above compounds showed cleavage of the glycosidic group, polymerization of the sugar moiety, decomposition and evaporation of the pyrolysis products. This involved some heterolytic reactions, which could be catalyzed by acid or alkaline materials.Kinetics of the pyrolysis process, including the rates and energies of activation were determined by thermal analysis and ESR spectroscopy. These data indicated that cleavage of the glycosidic bond is directly influenced by variation of its electron density and constitutes the rate determining step in pyrolysis of the carbohydrate compounds.