bluuebunny/crossref_metadata_2025_split huggingface dataset:
Corona‐discharge treatment of polyethylene films. I. Experimental work and physical effects
Authors: Carley James F. , Kitze P. Thomas 
Published: December 2004

AbstractCorona treatment of films, mainly polyethylene, was studied at commercial levels in a small continuous treater. Degree of treatment was characterized by measuring polar and dispersion components of surface energy, ASTM Wipe and ASTM Adhesion Ratio (“peel adhesion”). The chief factors studied were corona current, applied frequency, web speed, dielectric thickness and air‐gap thickness between electrode and film. Other factors less intensively investigated were type of film, film additives, aging time after treatment, humidity and corona atmosphere. The polar component of surface energy, γ, is the key to understanding the changes in adhesive behavior of the films during treatment. We found that, for the equipment used, γ is accurately given by the equation

where D = dielectric thick ness and G = air gap, both in mils; S = web speed, ft/min; I = corona current, ma, and γ is in dyne‐cm/cm2. A similarly structured equation describes ASTM Wipe. Using measured surface‐energy components for the pressure‐sensitive tape used in the peel adhesion test, it was possible to calculate an adhesion interaction for each film on which peel adhesion was measured and to show that it closely correlates with peel strength. Humidity changes in the moderate‐humidity range, number of electrodes used and corona frequency had little effect on properties. Slip additives inhibited development of adhesion until treatment levels became high; adhesion properties gradually diminished upon aging of films stored at ambient conditions.
An upper bound on the performance of plane strain mixers
Authors: Erwin Lewis 
Published: December 2004

AbstractConsideration of the basic equation for mixing in plane strain laminar flow shows that mixing can proceed much more rapidly than has been commonly accepted. While linear rates of mixing have been predicted previously, exponential rates of mixing are possible. An upper bound for, the rate of mixing in plane strain laminar flow is shown to be an exponential. The geometry of the flow which produces this most rapid mixing is shown to be plane strain extensional flow, sometimes called pure shear flow, with all interfaces aligned normally to the smallest principle axis of the deformation.
Dynamic‐mechanical behavior of poly(vinyl chloride), PVC, and chlorinated PVC compounds in the range of processing temperatures
Authors: Bonnebat C. , De Vries A. J. 
Published: December 2004

AbstractBoth real and imaginary components of the complex shear viscosity have been determined as a function of strain amplitude, frequency and temperature for various samples of poly(vinyl chloride), PVC, and chlorinated PVC of increasing chlorine content, with the aid of a Rheometrics mechanical spectrometer using eccentric rotating disk geometry. Different methods of sample preparation (low temperature dry‐blending, high temperature extrusion or calendering) were used to study thermomechanical history effects. Results obtained in the region of “linear” viscoelastic behavior were compared with those of capillary flow experiments: at relatively high temperatures the validity of the Cox‐Merz relationship was confirmed. Use of time‐temperature superposition procedures made it possible to predict the important variation of viscosity over a broad range of shear rates. The experimental results in particular with regard to the strong influence of temperature and thermal history, were tentatively interpreted in terms of a supermolecular structure due to the presence of ordered domains (microcrystallites) of variable amount and size. This interpretation was shown to be consistent with differential scanning calorimetry.
Rheological and energetic considerations of the fluid dynamics and scale‐up of mixing small particles into polymer melts in an internal mixer
Authors: White James Lindsay 
Published: December 2004

AbstractA basic theoretical investigation is made of the fluid mechanics of mixing of particulates into a polymer melt in an internal mixer. It is shown how increasing levels of viscoelasticity, especially with non‐linear, strain rate hardening character, should deteriorate mixing. he characteristics of internal mixers are discussed in terms of dimensionless groups. Rational scaling procedures based on considerations of viscoelastic fluid mechanics and energy balances are critically investigated and their limitations considered.
Impregnated concrete. I: Characterization of poly (methyl methacrylate) prepared in concrete matrices
Authors: Madruga E. L. , San Roman J. , Fontan J. 
Published: December 2004

AbstractConcrete specimens were impregnated with methyl methacrylate and after polymerization in situ, the extraction of polymer was carried out using appropriate solvents. The molecular weight and the stereochemical configuration of extracted polymer were determined by viscosity measurements and NMR spectroscopy respectively. The results obtained are discussed in relation to the increase of glass transition temperature of poly(methyl methacrylate) when the polymer is inside the concrete.
Analysis of impurity migration in plastic containers
Authors: Wang Fred H. L. , Duda J. L. , Vrentas J. S. 
Published: December 2004

AbstractThe problem of the migration of impurities from plastic containers has been analyzed, and the effect of the outward diffusion of the container contents on the impurity migration has been considered. The system of equations describing the coupled diffusion problem has been solved using finite‐difference methods, and an analytical solution has been developed for the initial stages of the mass transfer process. It was found that the outward diffusion of the container contents can exhibit a large effect on the migration of impurity if the ratio of the diffusivity of the container contents to the diffusivity of the impurity exceeds 100. Sufficiently large values of this diffusivity ratio and of the impurity partition coefficient can minimize the buildup of undesirable impurities in the contents of a plastic container.
Effect of polymeric additives on the rheological properties of talc‐filled polypropylene
Authors: Goel Dinesh C. 
Published: December 2004

AbstractThe effect of small amounts of low molecular weight polypropylene oxide on the rheological properties of talc‐filled polypropylene composites was studied experimentally using a capillary viscometer. The elastic behavior of the system was investigated by exit pressure and die swell methods. Initial studies showed that the talc filler does not influence the viscosity of the polypropylene but decreases the elasticity of the polymer system. Addition of oligomer concentration in a 40 wt percent talc‐filled polypropylene not only decreases the viscosity but also further decreases considerably the elasticity of the filled polymer composite. In both cases about 3 wt percent oligomer cone entration appears to be optimal, and further addition of oligomer does not significantly influence the rheological characteristics of the talc‐filled polypropylene composite.
A study of crosslinking in polyimides by viscoelastic and diffusion techniques
Authors: Chartoff Richard P. , Chiu Tai Woo 
Published: December 2004

AbstractThis paper is concerned with detecting crosslinking and changes in crosslink densities in cured polyimides. The methods used include diffusional weight gain and dynamic mechanical measurements on thin films of the cured polymers. In this study changes in diffusivities (D) for dimethylformamide (DMF) sorption into polyimide films as well as dynamic mechanical moduli and loss tangents are shown to be related to differences in polyimide cure schedule and composition. In all cases studied there is a β loss dispersion in the range 120 to 150°C and a γ loss dispersion in the range −50 to −80°C. The position and intensity of the β and γ relaxation processes vary primarily with cure cycle. There is a significant correlation between the magnitude of the diffusion coefficient and β and γ transition temperatures (Tβ and Tγ). Tβ increases and Tγ decreases with higher values of D so that T*, the difference Tβ − Tγ, is directly proportional to the diffusivity. By relating these results to data in the literature and the known curing behavior of polyimides, this trend is shown to be consistent with the presence of crosslinking and to be related to the crosslink density of the polymers. The data of this study indicate that measurements of diffusion coefficients for solvent sorption can be used to study changes in crosslink densities in glassy thermosetting polymers. Since the method is best suited for studying one dimensional diffusion, it also is suggested as a possibility for determining relative crosslink densities in adhesives bonded between substrates.
Sorption and transport of water vapor in glassy poly(acrylonitrile)
Authors: Stannett V. , Haider M. , Koros W. J. , Hopfenberg H. B. 
Published: December 2004

AbstractSorption data for H2O in glassy poly(acrylonitrile)(PAN) are presented for a range of relative vapor pressures at temperatures from 20 to 50°C. Simple dual mode sorption, involving “hole‐filling” and molecular solution appears to dominate the low activity region of sorption. Based on the clustering analysis suggested by Zimm and Lundberg, pronounced clustering of penetrant appears to occur above a relative pressure of 0.6. The form of the effective concentration‐dependent diffusion coefficient for H2O in PAN, determined by analysis of steady state permeation data, suggests that water in the microvoids and clusters has a lower mobility than the molecularly dissolved water in the polymer matrix. Time lag measurements at high upstream relative water vapor pressures suggest that the transient state permeation has a non‐Fickian character due to relaxations which occur slowly to accommodate the clustering process.
Manufacture of high stiffness solid rods by the hydrostatic extrusion of linear polyethylene. Part II: Effect of polymer grade
Authors: Hope P. S. , Parsons B. 
Published: December 2004

AbstractThe solid phase hydrostatic extrusion behavior of a range of linear polyethylenes, including methyl and butyl copolymer grades, has been compared in terms of processing behavior and product properties, for large diameter extrusions in the adiabatic thermal regime. The most useful improvements in both stiffness and long term creep behavior were obtained from medium melt flow index homopolymers, although such grades required higher forming pressures than the copolymers. This represents a reversal of the creep behavior trends observed for small diameter isothermal extrusions, where copolymer grades were superior. The engineering potential of hydrostatically extruded linear polyethylene is discussed.
Crystallization—morphology—polymer processing correlations for IUPAC low density polyethylenes
Authors: Magill J. H. , Peddada S. V. , Mcmanus G. M. 
Published: December 2004

AbstractThe crystallization behavior of three IUPAC low density polyethylene samples has been characterized by thermal analysis. Their rates of crystallization only are directly correlatable with their film forming ability in film blowing technology. The IUPAC samples possessed essentially indistinguishable physical properties, including differential scanning calorimetry (DSC) melting curves and rheological characteristics, but their propensity for crystallization was found readily to parallel their film forming ability and other characteristics associated with end‐use performance. The application of thermal analysis to assess crystallization is a unique diagnostic tool for measuring polymer film processability, which is well illustrated here using a few simple experiments made on the original polymer specimens and a polymer blend. Although all samples exhibit similar small‐angle X‐ray periodicities, the morphological differences assessed, particularly by microtomy‐optical microscopy, correlate with, and complement, the results of phase transformation kinetics responsible for film properties. Fractography‐scanning electron microscopy proves to be inferior to optical methods for revealing the morphology of these low density polyethylenes.
Energy‐related failure criteria of thermoplastics
Authors: Brüller O. S. 
Published: December 2004

AbstractThree aspects of the failure of thermoplastics, having a special importance in engineering, are investigated. They are: (a) Transition from linear to nonlinear viscoelasticity; (b) Crazing; (c) Fracture. Energy related criteria, developed from the Reiner‐Weissenberg thermodynamical theory of strength, are used for the characterization and prediction of failure under its different forms, for simple uniaxial loading histories such as creep, stress relaxation and constant rate of strain. The computation of the stored and dissipated parts of the specific stress energy becomes possible in a relatively simple way, if the relaxation modulus and the creep compliance are approximated by Prony‐Dirichlet‐type series with a finite number of terms. Published experimental data, as well as experiments carried out by the author on different thermoplastics are in very good agreement with theoretical results. Further, based on experimental data, the equations obtained can be reduced to very simple and useful relations. The influence of elevated temperatures (below the glassy‐transition point) on failure is also considered.
Die drawing: Solid phase drawing of polymers through a converging die
Authors: Coates P. D. , Ward I. M. 
Published: December 2004

AbstractDie drawing, a new process for the production of oriented thermoplastic rods with an ultrahigh modulus of elasticity, involves drawing an isotropic workpiece through a converging die at temperatures below the polymer melting point. Die drawing of polypropylene is described, but the process is applicable to any polymer which can be drawn by conventional means. The considerable advantages of die drawing compared with conventional tensile drawing and hydrostatic or ram extrusion are discussed.
Some studies on plasma polymerization of benzene and cyclohexane in the gas phase
Authors: Bölük M. Y. , Akovali G. 
Published: December 2004

AbstractThe glow discharge polymerization benzene and cyclohexane at 13.56 mHz, and 60 watts, in a plug flow reactor with inner electrodes was studied. Film powder and oily polymeric products were obtained from benzene, and only films were produced from cyclohexane. Polymers produced were analyzed by infrared and their characteristic maps demonstrating the correlation between various physical forms of polymer and reaction conditions were prepared. Excepting oily products, all others are found highly crosslinked and contained free radicals. Contrary to the plasma polymerization (PP) oil of benzene, all others showed no aromatic character.
Craze healing in polymer glasses
Authors: Wool R. P. , O'Connor K. M. 
Published: December 2004

AbstractCraze healing was observed in many amorphous glassy polymers. A detailed study of the kinetics of craze healing in atactic polystyrene (Mw = 255,000) was conducted. The crazes were created in 0.08 mm films in air at room temperature, To, and constant stress, σo ⋍ 2,300 psi, healed at temperature Th for a time, Th, at σ = 0, and recrazed at To and σo. Nucleation times, τ1 and τ2, and growth rates, L1, and L2, for the first and second loading, respectively, were measured as a function of th and Th for individual crazes using dark field optical microscopy. Complete optical and mechanical healing was observed for Th ⩾ 70°C(Tg ≅ 100°C). At constant Th, healing progressed in five stages with increasing th as follows; (i) no healing, τ2 = 0, L2 ≫ L1; (ii) partial healing, τ2 <τ1, L2 > L1; (iii) similar growth, τ2 = τ1, L2 = L1; (iv) slower growth, τ2 > τ1, L2 < L1; (v) disappearance, τ2 → ∞, L2 → 0. A craze healing envelope of Th vs Th was obtained for the above stages. Craze healing occurred by line mode in which uniform healing occurred along the entire length of the craze.
Aging of pressure‐sensitive adhesives I: Stability of styrene‐lsoprene‐styrene block copolymer films at 95°C
Authors: Harrison Daniel J. P. , Johnson Julian F. , Yates W. Ross 
Published: December 2004

AbstractThis paper is the first in a series investigating the aging of pressure‐sensitive adhesives based on styrene‐isoprene‐styrene (SIS) block copolymers. An investigation of thermal/oxidative aging of thin SIS films is presented. During these aging experiments, samples were analyzed with size exclusion chromatography (SEC), multiple internal reflectance (MIR) infrared spectroscopy, tack tests, and surface tension estimations.
On the dynamics and control of a plasticating extruder
Authors: Costin M. H. , Taylor P. A. , Wright J. D. 
Published: December 2004

AbstractIn recent years, there have been many papers published on the application of process control to plasticating extruders. Much of the literature concentrates on the more classical control techniques. However, recent research has studied the application of stochastic identification techniques for building transfer function models for the extruder. In particular, the relationship of screw speed to die pressure and temperature has been studied. In the present work, both step tests and pseudorandom binary sequence tests were used to study the process dynamics of a 38 mm Killion extruder having a Iength‐to‐diameter ratio of 24:1. This study concentrates on the regulation of the extruder pressure in the face of its inherent surging characteristics. Variations in the quality of the feed plastic were studied through pulse and step changes in input polymer composition. Significant control problems resulted from measurement noise, which appeared at the same frequency as the screw rotation speed. Various mathematical filters to reduce the effect of this noise on the control variables were studied.
Chemical interpretation of the relaxed permittivity during epoxy resin cure
Authors: Sheppard Norman F. , Senturia Stephen D. 
Published: December 2004

AbstractThe isothermal cure of a diglycidyl ether of Bisphenol‐A (DGEBA) epoxy resin with diaminodiphenylsulfone has been characterized by microdielectrometry and differential scanning calorimetry. The cure temperatures ranged from 410 to 460K. The behavior of the relaxed (or static) dielectric permittivity vs. cure time and temperature was determined from the microdielectrometry data. The DSC data was fit to an autocatalyzed reaction kinetics model, which was then used to predict reactive group concentrations as a function of cure time and temperature. The temperature dependence of the relaxed permittivity at constant chemical conversion was examined in the context of the Onsager theory for the relaxed permittivity of a system of independent dipoles. This analysis indicated that the dipoles in the resin are not independent, as assumed by the Onsager theory, and that the behavior is similar to that observed in polyethers. An empirical modification to the Onsager theory was used in conjunction with the kinetic model to estimate dipole moments for the epoxide, primary amine, and reacted (secondary and tertiary) amine groups. The relative and absolute values of the dipole moments were in good agreement with estimates based on the structures, leading to the conclusion that the observed decrease of the relaxed permittivity during cure of this epoxy/amine system is due to the changing concentrations of polar reactive groups.
Material modeling and solid phase forming of polycarbonate sheet
Authors: Lee D. , Luken P. C. 
Published: December 2004

AbstractThe Maxwell‐Voigt type mechanical model proposed by Haward and Thackray was further modified to describe the strain rate dependent stress‐strain behavior of polycarbonate under the uniaxial loading condition. Major modifications included effects associated with different hardening components of inelastic resistance and the related temperature dependent material behavior. The modified analytical model was shown to describe some of the important features of the stress‐strain behavior of polycarbonate specimens tested over the range of strain rates and temperatures. Using the stress‐strain relationship as input data; several finite element analyses were made to predict the behavior of polycarbonate sheets under a simple solid phase cup forming process. The computed strain distributions agreed reasonably with the measured values obtained from the gridded polycarbonate sheet that was formed at an elevated temperature. Some of the key assumptions that were used in the analysis are discussed.
Kinetics of alcohol assisted craze growth in polycarbonate
Authors: Kirloskar Mohan A. , Donovan James A. 
Published: December 2004

AbstractThe kinetics of alcohol assisted, relaxation controlled craze growth in polycarbonate (PC) were studied between 280 to 340K in methanol, ethanol, propanol, butanol, and pentanol. Viscous deformation of plasticized craze material controlled the growth rate of a single craze during stress relaxation in single edge notched (SEN) specimens. The activation energy increased with craze driving force in all alcohols, except methanol, because of diffusion limited plasticization. The craze stress increased with the alcohol's ability to plasticize; this is not understood, but may be due to solvent Induced crystallization.
Fourier transform mechanical analysis for determining the nonlinear viscoelastic properties of polymers
Authors: Ganeriwala Surendra N. , Rotz Christopher A. 
Published: December 2004

AbstractFourier Transform Mechanical Analysis (FTMA) has been used to study the strain amplitude dependent nonlinear dynamic mechanical properties of two elastomer compounds, nitrile rubber (NBR) and Neoprene, at various frequencies up to 750 Hz. Basic theory and experimental results are presented for one‐dimensional isothermal single frequency simple shear deformation. The Green‐Rivlin constitutive equation was used to model the observed behavior. The energy dissipation mechanism and a physical meaning for the material functions in the Green‐Rivlin representation have also been examined. The stress Fourier spectrum contained terms at the input frequency and its higher harmonics. It can qualitatively indicate the type of mathematical mode that best describes the observed behavior. The first harmonic storage and loss moduli showed strong dependence on the strain amplitude and frequency. The FTMA methodology presented can be used to systematically conduct nonlinear dynamic mechanical studies on any polymer. It can provide enough insight which, along with a knowledge of the molecular structure, may indicate a path for developing a better representative continuum constitutive model of these complex materials.
Draw resonance in polypropylene melt spinning
Authors: Yoo H. J. 
Published: December 2004

AbstractAn attempt is made to gain better physical insight on the draw resonance phenomenon occurring during melt spinning of polypropylene (PP). An experimental study is first carried ouit to determine effects of spinning variables and material parameters on draw resonance, using two PRO‐FAX PP resins and one PRO‐FAX/LDPE blend. Based on the experimental observations, our view on the cause of draw resonance is presented. With this new concept, we are able to explain various aspects of the draw resonance phenomenon observed experimentally during melt spinning of PRO‐FAX PP resins. It is concluded that the extensional viscosity versus strain relationship, as determined by an extensional rheometer, is one of the most valuable rheological measurements in analyzing flow instability occurring during polymer processing operations that utilize extensional flows.