bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of pyrolysis on the properties of stabilized PAN fabric reinforced phenolic resins for 2D carbon/carbon composites
Authors: Ko Tse‐Hao , Jaw Juu‐Jiuh , Chen Ying‐Chie
Published: May 2005

Two‐dimensional (2D) carbon/carbon composites were prepared with phenol‐formaldehyde resin and a commercial stabilized PAN fabric. The effect of pyrolysis on the microstructure and flexural strength of the composites during the carbonization process was studied. The interaction between fabric and matrix inhibited the decomposition and the thermal fragmentation, leading to a higher carbon yield for the final composition. Because of the formation of strong bonding in the fiber/matrix interface, the composites made with stabilized PAN fabric showed catastrophic failure and low flexural strength below carbonization temperatures of 600°C. Above 600°C, the flexural strength of the composites increased with the increase in the carbonization temperatures, even when the fracture behavior showed catastrophic failure.
Electroconductive nylon 6 and copper composites
Authors: Larena Alicia , Pinto Gabriel
Published: May 2005

A study is reported on the effect of the filler size and concentration on the electrical resistivity, density, and hardness of composites made of copper powder embedded in nylon 6 matrix by means of compression molding. The electrical resistivity of the composites is > 1011ohm·cm unless the metal content reached the percolation threshold, beyond which the resistivity decreased markedly by as much as 1012. The percolation concentration was found to decrease with a decrease in the average particle diameter. The density of the composites was measured and compared with values calculated assuming different void levels within the samples. However, there is no sharp variation in the density due to the onset of percolation. Furthermore, it is shown that a percolation concentration can be also defined in the hardness/metal concentration curves as the intercept of linear regression curves of thelowandhighmetal content regimes, respectively.
Interfacial shear strength studies of nicalon fibers in epoxy matrix using single fiber composite test
Authors: Ho A. , Netravali A. N. , Phoenix S. L.
Published: May 2005

Interfacial properties of Nicalon (SiC) fiber in epoxy matrices of varying stiffnesses were studied using the single fiber composite test, in conjunction with stress birefringence patterns. Extensive debonding was observed with hard epoxies, but transverse matrix cracks were found in the more flexible epoxies, with the interface remaining intact. Micromechanical modeling and Monte Carlo simulation of the single fiber composite fragmentation process provided a basis to compute the interfacial shear stress from the final fragmentation length distribution. The interfacial shear stress appeared to decrease moderately with increasing matrix ductility. The large diameter Nicalon fibers create transverse cracks in the single fiber composite specimens made with flexible epoxies. Consequently, there is a high possibility of premature failure of the specimen before fiber break saturation is reached. This poses some difficulty in interpreting the results for flexible epoxies. It was also found that the interfacial shear stress values from the single fiber composite tests were always considerably higher than the ultimate shear stress values obtained from bulk epoxy (without fiber) tension tests. This effect is similar to what was seen earlier for single fiber composite tests based on graphite fibers and similar epoxy blends, though the difference between the two values was not as great.
Crystallinity in high polymers and copolymers: A determining factor for their practical applications
Authors: Natta Giulio
Published: May 2005

The relationships between crystallinity and physical and technological properties of high polymers are examined. In addition, the relationships between structure and crystallinity are discussed and polymers consisting of asymmetric monomeric units are examined in particular. In correspondence with the different possible configurational successions, different conformational characteristics (chain structures) and different physical properties are observed. Polytactic polymers are taken into consideration for the most part. With regard to copolymers, various types of crystalline polymers, in particular those which due to isomorphism of monomeric units are crystalline for any composition, and new classes of alternating copolymers are described.
Fire‐retardant components of self‐extinguishing polyesters
Authors: Roberts Carleton W.
Published: May 2005

An attempt has been made to categorize the various materials which have been utilized in polyester compositions to impart or enhance the fire‐retardancy of these compositions. Examples of halogen‐containing and phosphorus‐containing compounds are classified according to where they may be thought to occur in the complex chemical structures which are polyesters. The classifications are basically designed to take advantage of the known chemical reactions which lead to polyesters; the fire‐retardant component may be incorporated into the final composition in the diacid, diol, crosslinking agent or may be merely mechanically added as a diluent.
The interpretation of tacticity measurements
Authors: Miller Robert L.
Published: May 2005

To date, quantitative stereochemical data are available for a few polymers only. A convenient and graphic representation of this data has been developed. Analysis of this data yields two parameters characterizing a polymer, one representing the tacticity and the other representing the nature of the tactic sequence distribution. The statistical parameters obtained may be related to the polymerization conditions and, hence, to the mechanism of stereoregulation. Furthermore they may be related to a number of physical properties, such as melting point, equilibrium crystallinity, and melting curve. Thus, the proper analysis of the NMR data supplies a link between polymerization conditions and the properties of the resulting polymer.
Analysis of pressure transducer data from screw extruders
Authors: McKelvey James M. , Wheeler Norton C.
Published: May 2005

Based on the simplified, flat‐plate, isothermal, Newtonian flow model of the screw pump, an expression for pressure as a function of time at a fixed point on the extruder barrel has been derived. This expression predicts a periodic saw tooth pressure cycle under most flow conditions. It also establishes the flow conditions under which an inversion of the saw tooth cycle will occur. Pressure transducer data, in conjunction with extrusion rate data, can be used to calculate the average fluid viscosity in a region near the transducer.
Viscous flow and degradation of molten polypropylene
Authors: Schott Hans , Kaghan W. S.
Published: May 2005

The melt extrusion of a commercial polypropylene resin was studied with a screw extruder and a series of capillary dies of length:radius ratios varying from 0 to 65. Three temperatures and the range of shear rates encountered in industrial processing were covered. The temperature dependence of the apparent melt viscosity of polypropylene was intermediate between linear and branched polyethylene. Extrapolated zero shear activation energy for viscous flow was 9 ± 1 Kcal/mole. Shear dependence of the apparent viscosity of polypropylene melt was greater than for branched polyethylene in turn, greater for linear.
The anisotropy of creep behavior in oriented thermoplastics
Authors: Darlington M. W. , Saunders D. W.
Published: May 2005

Detailed studies have been carried out on the anisotropy of creep and creep rupture behavior of thermoplastics oriented by the imposition of a large permanent deformation. This deformation is usually such as to produce simple fiber symmetry within the specimen. Experimental techniques have been devised for the accurate measurement of all three principal strains during tensile creep on small samples which are cut from the oriented specimens at various angles to the symmetry axis. In this way a full characterization of the creep behavior up to strains of 5 percent has been obtained at room temperature.

Results are presented for work on rigid poly (vinyl chloride), poly(methyl methacrylate), and low density polyethylene. The results are discussed in terms of the time dependence and nonlinearity of the anisotropy. Creep rupture results on similar specimens are also presented and discussed. Anisotropy due to orientation is shown to be important in determining engineering properties and in understanding structure‐properties relationships.
Plastic deformation and structure of extruded polymer solids
Authors: Peterlin A.
Published: May 2005

During extrusion the main deformation and orientation of macromolecules is achieved by the flow component with longitudinal gradient. The orientation increases drastically if some solidification occurs during flow, yielding row‐nucleated cylindrites and even fully oriented hard elastomers. In all cases the basic elements are stacks of very thin (∼100Å) folded‐chain lamellae connected by very few tie molecules. The plastic deformation of the solid transforms the original lamellar material into the extremely well oriented fibrous structure with high anisotropy of physical properties. The basic element are the highly aligned, very long and thin microfibrils bundled into fibrils. The axial strength of microfibrils is caused by the great many taut tie molecules connecting as almost crystalline bridges the crystalline blocks across the interposed amorphous layers. In plastic deformation of fibrous material the fibrils are sheared and longitudinally displaced. The latter mode is responsible for almost all the observed elongation. It smooths the structural defects on the surface of fibrils caused by the ends of microfibrils and thus produces a better lateral fit of fibrils resulting in rapidly increasing resistance to plastic deformation. The former mode extends the interfibrillar tie molecules and hence drastically increases their fraction per amorphous layer.
Hydrostatic extrusion of solid polyethylene
Authors: Davis L. A.
Published: May 2005

Solid state processing of polyethylene (SS60‐050) by hydrostatic extrusion is investigated. Measurements are also reported for the tensile properties of polyethylene 60–050 under superposed hydrostatic pressure. With the latter data an estimate is made of the pressure required for extrusion of polyethylene in the absence of losses due to friction and redundant work. The limiting conditions for successful extrusion are discussed.
An approach for the processing engineer: Rheotechnics
Authors: Casale A. , Moroni A. , Ronzoni I.
Published: May 2005

Processing involves complex polymer flow problems, either in the melt or in solution. Rheologists have developed many studies with the aim of correlating polymer structure with flow properties and polymer processing. Most of these studies, however, have had relatively little impact on practical processing because of the difficulty in solving the mathematical equations involved. Recently, a relatively few papers have been published with the aim of bridging the gap between theoretical rheology and technology. The first part of the paper presents an account of works which have dealt with the process of filling a mold cavity. The second part discusses briefly some experimental results which provide a correlation between moldability and rheological properties. By analogy with the terms “electrology” and “electrotechnics,” the term “rheotechnics” is suggested for this new area of study.
Transport properties of polyvinylpyridinium anion‐exchange membranes
Authors: Wallace Richard A. , Vijayaraghavan N. V.
Published: May 2005

Measurements have been made of the electrical conductivity of water‐saturated heterogeneous anion‐exchange pyridinium membranes in their carbonate and hydroxyl ionic forms as a function of temperature. The pyridinium membranes were prepared from quaternized poly‐4‐vinylmethyl‐pyridinium resin electrolyte incorporated in a polyvinylidene fluoride matrix; the ratio of the pyridinium electrolyte to polyvinylidene fluoride was 4 to 1 by weight.

The ion‐exchange capacity and water content of these anion‐exchange pyridinium membranes were measured. Corresponding Arrhenius activation energies of ion transport of carbonate and hydroxyl counter‐ions have been calculated. Self‐diffusion coefficients and the equivalent conductances of these pyridinium membranes in their carbonate and hydroxyl counter‐ion forms have also been determined over a wide temperature range and compared to the reported values for present quaternary ammonium anion‐exchange membranes.
A dry‐etch resistant positive‐working electron resist
Authors: Roberts E. D.
Published: May 2005

This paper describes two types of cross‐linked positive‐working electron resists. The first is based upon phenol‐formaldehyde resins crosslinked to poly‐(methyl methacrylate) by phenolic ester groups. The second type is based upon polystyrene, crosslinked by carboxylic acid anhydride groups. The resist properties can be varied by changing the proportion of crosslinks. A version of the second type which contains about 95 percent styrene units is described. This material shows very good resistance to degradation in a plasma‐etching process for preparing chromium on glass masks, even when it is used as a very thin film.
Proximity printing of chrome masks
Authors: Meyerhofer Dietrich , Mitchell Joe
Published: May 2005

We have investigated the application of proximity printing to the copying of chrome masks used for integrated circuit fabrication. The mask blanks were coated with various positive and negative photoresists. When plotting the difference in width between etched lines on the print and the corresponding feature on the mask as a function of the separation, one observes fluctuations due to the movement of the diffraction peaks in the optical image. For the negative resist, the averaged difference in width is approximately constant to separations of 25 micrometer (μm), while for positive resists it changes monotonically with increasing gap spacing. The measured results are compared with calculations using a model of the resist exposure and development and good agreement is obtained. On the basis of these results we conclude that proximity printing would be difficult to apply to mask replication, but that it has considerable promise for replicating 10X step‐and‐repeat reticles.
Craze fibril formation and breakdown
Authors: Kramer Edward J.
Published: May 2005

As crazes grow in areal extent they also increase in width. The areal growth involves craze tip advance which has been shown to occur by the Taylor meniscus instability. Craze widening, at least for air crazes, occurs by drawing more fibrillar material from the craze‐bulk polymer interfaces at essentially constant extension ratio. Simple arguments will be given to predict the scale of the fibrillation in terms of the stress S at the craze tip and interfaces and an effective polymer surface energy (Γ) where:

which assumes that all entangled chain crossing the surface are broken [γ represents the van‐der‐Waals (intermolecular) surface energy, d is the entanglement mesh size, vE is the entanglement density, and Ub is the energy required to break a single backbone bond]. These arguments also give the rate of fibrillation as a function of S, a nominal plastic resistance σy and Γ and can explain the fact that the stress for crazing increases relative to that for shear deformation as the entanglement density of the polymer is increased. The geometrically necessary entanglement loss (either by scission as assumed above or by disentanglement‐ at temperatures just below Tg) that accompanies fibril formation has important consequences for fibril stability. The probability p that a given entangled chain is lost can be computed from simple geometrical considerations knowing the fibril diameter D, its extension ratio λ and the mesh size d; p increases rapidly as Dλ½ becomes comparable to or less than d. These concepts can be tested in blends of high molecular weight polymer with chains of the same polymer that are too short to entangle.
Microstructural aspects of failure in semicrystalline polymers
Authors: Schultz J. M.
Published: May 2005

Microstructural features of semicrystalline polymers are reviewed, as are the roles of chain properties and thermal history in their development. Experimental results relating failure properties to microstructural detail are described. General models to explain inter‐ and intra‐spherulitic failure behavior are proposed. Important are (a) the role of spherulite size in boundary incompatibility, (b) competition between spherulite boundary cracking and intraspherulitic yielding, (c) competition between localized (interspherulitic) fracture and dispersed (intraspherulitic) fracture.
Craze failure by midrib creep
Authors: Verheulpen‐Heymans Nicole
Published: May 2005

It has been known for some time that crazes thicken during growth mainly by drawing in fresh material from the craze‐bulk interface, keeping the average craze fibril draw ratio approximately constant. Since Creep effects contribute only negligibly to craze growth rates these effects have generally been considered unimportant regarding craze breakdown. However, it is also known that the first stage of fracture is failure of the craze midrib, which is a highly drawn, very thin region down the middle of a craze. Because of the very low thickness of the midrib it has little influence on craze behavior, and information on midrib behavior is difficult to obtain. It is the purpose of this paper to attempt to rationalize what information is available.
Stress relaxation of glass‐fiber‐reinforced rigid polyurethane foam
Authors: Morimoto Kiyotake , Suzuki Toshio , Yosomiya Ryutoku
Published: May 2005

Flexural stress relaxations were measured for rigid polyurethane foams (PUF) and glass‐fiber‐reinforced rigid polyurethane foams (FRU). The results were successfully analyzed in terms of the five element Maxwell model: (1) Samples reinforced with longer fibers exhibit reduced stress relaxation and reduced temperature dependency of stress relaxation; (2) The increased expansion ratio reduces the flexural modulus of both reinforced and non‐reinforced materials, but the stress relaxation tends to increase greatly at the higher temperature for PUF, while not so greatly for FRU; (3) The temperature dependency of E1 decreases as longer fibers are used to reinforce the polyurethane. The dependency is minimal for the polyurethane reinforced with continuous fibers, where the reinforcing effect is maximal; and (4) The activation energy calculated from τ2 according to the Arrhenius plot is smaller for the longer fiber reinforced polyurethane foams.
A study of the dynamics of foam growth: Analysis of the growth of closely spaced spherical bubbles
Authors: Amon Moris , Denson Costel D.
Published: May 2005

A mathematical analysis of bubble growth in an expanding foam is presented. The analysis is based on a cell model whereby the foam is divided into spherical microscopic unit cells of equal and constant mass, each consisting of a liquid envelope (or shell) and a concentric spherical gas bubble. Expansion occurs by diffusion of a dissolved gas from the supersaturated envelope into the bubble. This cell model is capable of describing important qualitative features of a real system of numerous bubbles growing in close proximity to one another, and is intended as the building block of a global analysis of macroscopic foam expansion. The coupled algebraic and differential equations governing the growth of a cell are derived and solved numerically. Five dimensionless parameters are identified for the case of constant temperature and pressure outside the cell, and their effects are demonstrated through computer simulations of the system. Of these parameters, surface tension and initial radius prove to be of relatively little importance in the practical cases considered. The other parameters are the thermodynamic driving force, the cell mass (inversely proportional to the number density of bubbles), and the ratio of characteristic times for mass and momentum transport.
Molecular kinetic theory of the glass transition
Authors: Chow T. S.
Published: May 2005

An overview of a new molecular kinetic theory of glass‐transition phenomena is presented and experimental comparisons of its prediction for a variety of thermal and stress histories reviewed. The theory, which was developed in accordance with the balance of nonequilibrium statistical entropy, is shown to provide a unified interpretation of some recent models. The volume‐relaxation process in amorphous polymers over the glass‐transition region is regarded as the result of the collapse of a series of free volumes having different levels of energies of hole formation. An applied stress is shown to contribute to the variation of the entropy. An activation volume is introduced as a new tensorial extensive variable. The theory is applied to the phenomenon of physical aging in polymer glasses and shown to provide good quantitative agreement with the results of a well‐known experiment on volume recovery of poly(vinyl acetate). This supports the underlying postulate of a fundamental link between the apparent relaxation time and the mean energy of hole formation, the distribution of relaxation times and the free‐volume fractions. In contrast to the prevalent thinking toward free volume theories, an explicit expression between Tg and stress is presented and reveals that Tg does not continue to increase at all pressures but levels off to a semi universal asymptote at very high pressure. The calculated effect of stress rate is found to be in good agreement with dynamic viscoelastic measurements.
Physical aging of heavy metal fluoride glasses—sub‐Tg enthalpy relaxation in a ZrF4‐BaF2‐LaF3‐AlF3 glass
Authors: Moynihan C. T. , Bruce A. J. , Gavin D. L. , Loehr S. R. , Opalka S. M. , Drexhage M. G.
Published: May 2005

The enthalpy changes during structural relaxation or physical aging of a 58ZrF4‐33BaF2‐5LaF3‐4AlF3 (ZBLA) glass during annealing well below the glass‐transition temperature have been studied using differential‐scanning calorimetry at several sub‐Tg temperatures. Substantial relaxation within the course of several hours was detected at temperatures as low as sixty degrees below Tg (585K). The relaxation process is extremely nonlinear and self‐retarding. The time dependence of the enthalpy during the initial stages of annealing was modeled approximately using the Narayanaswamy‐Tool approach. The structural‐relaxation parameters obtained from this fit were used to predict rates of physical aging for rapidly cooled ZBLA glass at temperatures close to ambient.
Spectroscopic observations on nonequilibrium glassy poly(vinyl chloride) and polystyrene
Authors: Joss B. L. , Bretzlaff R. S. , Wool R. P.
Published: May 2005

The relationship of valence‐coordinate deformation to the temperature dependence of some infrared peak‐absorption frequencies in Poly(vinyl chloride) (PVC) and polystyrene (PS) is stated. A skeletal band and a CH2 rocking band in PVC and a ring‐mode band in PS were studied in two kinds of experiments: steady heating and cooling of a quenched (nonequilibrium, glassy) sample through its glass‐transition temperature, Tg, and long‐term annealing of quenched samples below Tg, followed by steady heating and cooling. The results, a slope discontinuity, ΔM, in the v(T) relation at Tg and a frequency shift, Δviso, during isothermal annealing below Tg, are analyzed in two theoretical approaches. Interchain and intrachain contributions to the observed frequency shifts are expected to occur with a differing relative significance in different kinds of molecular vibrations, leading to one possible method of distinguishing valence‐coordinate deformation (chain strain) from other effects.
Spherulite growth in isotactic polypropylene‐based blends: Energy and morphological considerations
Authors: Bartczak Z. , Gałȩski A. , Martuscelli E.
Published: May 2005

The kinetics of isothermal crystallization of polymer blends in which the matrix is a crystallizable polymer is considered. It is shown that depending on the difference in interfacial energies the inclusions are rejected or engulfed by the growing spherulite. Other factors influencing rejection, engulfing, and/or deformation of dispersed particles of the second polymer are the viscosity of the melt, the spherulite growth rate, and the size of dispersed particles. If the difference in interfacial energies is positive, then rejection or engulfing requires additional work to be done by the crystallization front. This dissipation of energy decreases the spherulite growth rate. It is estimated that the rejection of the second component is the most important phenomenon in the crystallization of blends. The spherulite growth rate of isotactic polypropylene in blends with low‐density polyethylene and several elastomers was studied as a function of crystallization temperature and concentration. The comparison of growth rate data with morphological changes occuring during crystallization of blends studied shows very good agreement with the theoretical predictions based on energetics considerations.
Tensile yield in nylon 6,6
Authors: Hartmann Bruce , Cole Richard F.
Published: May 2005

Uniaxial tension tests to, the yield point were performed on poly(hexamethylene adipamide) (nylon 6,6) as a function of temperature from 21 to 200°C at a strain rate of 2 min−1. At 21 and 60°C, measurements were also made at strain rates from 0.02 to 8 min−1. Using simple rate theory, reasonable values of activation volume were obtained, but the simple theory is inadequate to determine the activation energy. The yield‐strain temperature dependence changes at 160°C as a result of a reversible crystal‐crystal transition. Because of this behavior of the yield strain, the yield energy is not a linear function of temperature, as observed for several other polymers.
Tensile properties of polyarylate‐polycarbonate blends
Authors: Mondragon Iñaki , Nazabal Jon
Published: May 2005

Blends of polyarylate (PA)‐a copolyester of bisphenol A with a mixture of terephthalic/isophthalic acids at 50/50 proportion–and polycarbonate of bisphenol A (PC) were melt mixed into films with a Brabender Plasticorder. The processing produced transreacted mixtures that exhibited a modulus and yield stress with a maximum that is above the linear (very similar to that observed for compatible polymer blends). The elongation at yield did not show any maximum but it is also above linearity.
Rheological and processing characteristics of polystyrene in the vicinity of Tll transition
Authors: Santamaría A. , Gallego F. , Muñoz M. E.
Published: May 2005

Rheological and processing parameters have been measured for a commercial polystyrene at temperatures from 155°C to 210°C resulting in no clear evidence for the existence of liquidliquid transition. Zero shear viscosities obtained from dynamic measurements and ends corrections and extrudate swell from capillary rheometry are analyzed, with the conclusion that the mechanism of flow is the same throughout the range of temperatures considered.
A new method of preparation of a rubber‐modified polyamide directly during caprolactam polymerization
Authors: Cimmino S. , D'Orazio L. , Greco R. , Maglio G. , Malinconico M. , Mancarella C. , Martuscelli E. , Musto P. , Palumbo R. , Ragosta G.
Published: May 2005

A new method to obtain a rubber‐modified polyamide 6 (PA6) directly during the polymerization of the caprolactam (CL) is described. Binary and ternary blends containing ethylene‐propylene random copolymers (EPM) and/or a fictionalized EPM rubber (EPM‐g‐SA) were prepared and their morphology as well as their mechanical properties were investigated as function of composition and reaction conditions. It was found that the morphology of the blends is strongly dependent on the method of preparation. More complex structures are observed in blends obtained with the “Solution” preparation. For a better resolution of the morphology, the smooth ultramicrotomed surfaces were exposed to boiling xylene before SEM (scanning electron microscopy) examination. The rubbery phases are selectively dissolved whereas the PA6 matrix is left. The tensile mechanical properties and the Izod impact behavior are related to the mode and state of dispersion of the rubbery components. The impact properties of ternary PA6/EPM/EPMg‐SA (80/18/2) and (80/15/5) blends, prepared during the CL polymerization are comparable to those of similar blends obtained by usual melt mixing procedures.
Mixing studies in the single screw extruder
Authors: Bigio D. I. , Boyd J. D. , Erwin L. , Gailus D. W.
Published: May 2005

Laminar mixing in a single screw extruder between two miscible liquids is considered. Studies are presented which examine the mixing performance in single screw extruders with mixing sections, variable geometry screws, and multi‐viscosity mixtures. Model extruders, set up on engine lathes, were used to mix colored silicone rubber which eventually cured in the screw channel. The cured silicone was then removed and sliced to measure the mixing. Results show mixing as a function of both down channel location and total average strain. For the mixing section study, results support the theory of interfacial area reorientation as the key mechanism in mixing section performance. Increasing viscosity ratio for the multi‐viscosity study showed a decrease in mixing rate.
The production and properties of poly(aryletherketone) (PEEK) rods oriented by drawing through a conical die
Authors: Richardson A. , Ania F. , Rueda D. R. , Ward I. M. , Baltá Calleja F. J.
Published: May 2005

Oriented poly(aryletherketone) (PEEK) rods have been produced by drawing isotropic polymer through a conical die. Room temperature Young's moduli were measured by three‐point bending and ranged from 5 GPa at a draw ratio of about 2 to 11 GPa at a draw ratio of about 4. Dynamic mechanical properties were explored in the range −150 to 200°C; two loss peaks were observed, with the higher corresponding to Tg.
Determination of end‐group concentrations and molecular weight of poly(butylene terephthalate) by solid‐state fourier transform infrared spectroscopy
Authors: Kosky P. G. , McDonald R. S. , Guggenheim E. A.
Published: May 2005

Molecular weight determination in poly(butylene terephthalate) (PBT) is hindered by the inherent difficulties of intrinsic viscosity (IV) determination in general and toxic solvents used in particular. In any case molecular weight does not include information as to the identity of end‐groups in the polymer chain. This report shows how the Fourier Transform Infrared method of Ward for PET can be adapted for alcoholic and acidic end‐group determinations in poly(butylene terephthalate) (PBT) and consequently for the number averaged molecular weight of PBT. A statistical analysis was performed on comparative IR‐ and IV‐derived molecular weight which revealed a correlation coefficient of better than 90 percent. The method is, therefore, recommended as an alternative to the standard IV technique, especially if simultaneous end‐group analyses are also required.
Recent advances in interpenetrating polymer networks
Authors: Sperling L. H.
Published: May 2005

Interpenetrating polymer networks (IPN's) can be defined as a combination of two polymers in network form, at least one of which was synthesized and/or crosslinked in the immediate presence of the other. Historically, the science of IPN's began with the papers of J. R. Millar in 1960 on homo‐IPN's made from polystyrene, but the first recorded publication is a patent by J. W. Aylsworth in 1914. This latter system was based on phenol‐formaldehyde for one network, and sulfur cured natural rubber for the other network. Early academic laboratories interested in IPN's include the Frisch team at Detroit and SUNY, who soon added their former student, Danny Klempner, and Yuri Lipatov's team at the Ukranian SSR Academy of Sciences in the USSR, as well as the author's laboratory. More recent academic teams interested in IPN's include Douglas Hourston at the University of Lancaster, England; Robert Cohen at MIT; S. C. Kim at the Korea Advanced Institute of Science and Technology, Seoul, Korea; G. Meyer and J. M. Widmaier in Strasbourg, France; and many others. Numerous industrial laboratories are interested, noting that about 90 U.S. patients have been granted, most of them in the past ten years. Systems of special interest include the new thermoplastic IPN's, which are really hybrid materials between polymer blends and IPN's, and the IPN‐based RIM (reaction injection molding) materials. Other materials include the sequential IPN's and the SIN's, which have both polymers simultaneously polymerized, and the latex IPN's, which often exhibit core‐shell characteristics.
Inertia and gravitational effects in extrusion dies for non‐Newtonian fluids
Authors: Leonard William K.
Published: May 2005

An analysis is presented which allows the sheet or film die designer to estimate when inertial and gravitational effects are important. General theoretical equations are developed for end fed dies with arbitrary variation of the cavity cross sectional shape, cavity taper, slot length, and gap over the width. The method assumes viscous flow and a two dimensional approximation for the cavity flow. For fluid flow properties, it is assumed only that the apparent viscosity is a single valued function of the shear rate. In the important special case of constant die geometry and power law fluids, three dimensionless numbers plus the power law index are the parameters controlling the uniformity of flow from the die. Results are presented that illustrate when die orientations with respect to gravity and when fluid inertia are important. When they are not, simple expressions for die inlet pressure and uniformity index are given.
Energy absorption characteristics of polymeric foams used as cushioning materials
Authors: Miltz Joseph , Ramon Ori
Published: May 2005

The “Efficiency of Energy Absorption” (or “Efficiency”) and “Ideality” parameters were evaluated for several plastic foams and were found to be very useful in choosing an appropriate cushion for the protection of a specific product. The maxima in these parameters were found to be in the same range of stresses, when derived from dynamic measurements or from predicted stress‐strain curves based on previously proposed “Reference” and “Modified Boltzman Superposition” Models. For the rate independent foams the maxima in these parameters do not change with strain rate and can therefore be derived from slow, constant rate (“static”) experiments. For rate dependent foams however, the maxima from “static” measurements were found to be in a lower range of stresses than those derived from dynamic ones. As a result, slow rate compressive measurements do not predict well the behavior of the foams during impact and the use of the “Reference” and “Modified Boltzman Superposition” Models is required for good predictions. It was found that the suffer PS and PE foams attain maximum Efficiency and Ideality at higher stresses than the more flexible PUR foams.
Rotary injection reaction injection molding (RI‐RIM). Part II: Interfacial segregation of release systems
Authors: Briscoe B. J. , Khan M. B. , Richardson S. M.
Published: May 2005

This paper describes the shear imposed interfacial segregation of release systems for the facilitated attenuation of polyurethane (PU) adhesion to metal coun‐terfaces using a RI‐RIM system. It is shown that the migration rate of the dispersed release additives due to a shear imposed stress in the resin fluid is much greater than that arising from Fickian diffusion, thereby removing a vital constraint from conventional practice. The novel rotary injection RIM system is presented to simulate the on‐line injection and shear induced interfacial segregation in model PU/abherent systems. A wide range of recipes comprising single (liquids or solids) and multicomponent (liquid‐liquid and solid‐liquid) release materials were injected into the polymerizing resin mixture to provide cohesively weak and friable “particle” boundary layer assemblies at the PU/metal interface. An instrumented Blister Test was employed to evaluate the quality of the molded interfaces in terms of adhesion and the concentration distribution of the injected species in the final cured moldings was determined through high pressure liquid chromatography (HPLC). A comparison of the results on the shear modified and the compounded interfaces confirm an accentuated lateral migration of the additives to the interface resulting in an appreciable diminution in the adhesion of the system. Finally, transport models are suggested to account for the observed augmented transport.
Mechanical properties and behavior of open cell foams used as cushioning materials
Authors: Ramon O. , Mizrahi S. , Miltz J.
Published: May 2005

It is the purpose of the present publication to show that most of the phenomenological viscoelastic theories developed for bulk polymers can be readily adapted to plastic foams in order to evaluate their mechanical properties. In addition it will be demonstrated how the mechanical properties of open cell plastic foams can be predicted from a few simple compression and relaxation experiments.
Impact fracture toughness tests on polymers
Authors: Adams G. C. , Bender R. G. , Crouch B. A. , Williams J. G.
Published: May 2005

A series of impact tests are described in which the plane strain fracture toughness, Kc1, of five different polymers is measured using a three point bend specimen at striker speeds up to 5m/s. At low speeds Kc1 is determined using the maximum load and a static analysis, but at speeds greater than 1 m/s the dynamic effects render the load signal unusable. For the higher speeds the fracture is timed using contact and crack propagation gages and the analysis is performed using the striker displacement at fracture. A dynamic analysis is used to convert this measurement to the true specimen displacement and Kc1 is determined from this. The apparent downward trends in the Kc1 results obtained, especially at speeds above 3m/s, are discussed.
Dynamics of a CSTR for styrene polymerization initiated by a binary initiator system
Authors: Kim Kee‐Jeong , Choi Kyu‐Yong , Alexander James C.
Published: May 2005

The steady state and dynamic behavior of a continuous stirred tank reactor has been analyzed for free radical solution polymerization of styrene initiated by a mixture of two initiators having different thermal stabilities. From the steady state analysis of the reactor model with a mean residence time as a bifurcation parameter, four unique regions of steady state solutions are identified in an operating parameter space for a given initiator feed composition. A variety of complex bifurcation behavior such as multiple steady states, Hopf bifurcation and limit cycles have been observed and their stability characteristics have been analyzed. The effects of feed initiator composition and the concentration of the initiator in the feed stream on the reactor dynamics are also presented.
Bulk and surface compression viscosities of high and low density polyethylenes
Authors: Aleman J. V.
Published: May 2005

Bulk compression flow of high density polyethylene (HDPE) and low density polyethylene (LDPE) have been measured at temperatures of 423 to 463K, pressure up to 150 MPa, and bulk compression rates of about 1.0 to 200.00 × 10−5 s−1. Bulk and surface compression modulus of elasticity (L and Ks), longitudinal bulk compression viscosity (ηL), and surface compression viscosity (η) are described as a function of compression rates (kv and ks), compression deformations (kv percent and Ks percent), and temperature (T). Bulk and surface compression flow activation energies are of the order of 40 to 100 KJ/mol and 3.84 KJ/mol, respectively.
Numerical simulation of the cast film process
Authors: d'Halewyu S. , Agassant J. F. , Demay Y.
Published: May 2005

The cast film process is studied and a numerical simulation is performed using a finite element method. Two dimensional equations involving the thickness and a mean velocity are used by considering the film as a thin layer. The process is assumed to be isothermal between the die exit and the quick cooling on the chill roll. The width of the film is computed iteratively as a free surface problem by means of a finite element method. The thickness distribution of the film is obtained by a finite volume method. This approach allows modeling of the well known “dog‐bone” or “edge bead” defect with a reasonable computation time.
Crystallization phenomena in the injection molding of poly ether ether ketone and its influence on mechanical properties
Authors: Hsiung Chang‐Meng , Cakmak Mukerrem , White James L.
Published: May 2005

A basic experimental investigation of structure development in the injection molding of poly ether ether ketone (PEEK) is presented. It is shown that, dependent upon processing conditions, especially mold temperature, PEEK may be injection molded to form glassy or crystalline parts or parts consisting of intermediate structures such as a glassy surface and one with an internal crystalline link. In general, cold molds produce glassy parts and hot molds crystalline parts. This behavior is carefully characterized using optical microscopy, differential scanning calorimetry, and wide angle X‐ray diffraction techniques. The mechanical properties of these injection molded parts is characterized as a function of the crystalline and glassy contents and types of structural gradients developed in the parts.
Analysis of polymer blend morphology by transmission and reflection light scattering techniques
Authors: Belanger C. , Cielo P. , Favis B. D. , Patterson W. I.
Published: May 2005

Optical inspection is a potentially powerful and practical tool to collect information on polymer blend morphology for on‐line quality and process control. This paper describes two approaches for the characterization of polymer blend materials by multiple light scattering. A quantitative evaluation of spectral turbidimetry (scattering of transmitted light) is presented and an adaptation of this technique for monitoring particle size, independent of the volume fraction is demonstrated. Such a procedure is applicable to materials in film form. A different approach is presented for the analysis of nearly spherical particles in optically thick samples: the diffuse reflection pattern surrounding the position of incidence of a focused light beam on the surface of the turbid medium is scanned by a single side imaging system. A spectral pseudo‐transmittance signal processing technique provides particle size information again independent of the volume fraction: Both techniques have been tested using well characterized polystyrene microspheres suspended in water as well as poly(methyl) (methacrylate)/polystyrene polymer blends.
Finite element analysis of dip coating with bingham fluids
Authors: Hurez P. , Tanguy P. A.
Published: May 2005

A finite element analysis of the dip coating process with Bingham fluids is presented. The solution method for the viscoplastic flow problem was based on the augmented Lagrangian method allowing a rigorous treatment of the stress discontinuity. To compute the location of the free surface at equilibrium, an iterative method was used based on the arbitrary Eulerian‐Lagrangian approach in conjunction with mesh smoothing. Numerical predictions were validated against experimental data for the Newtonian limit case. Computations were then performed with Bingham fluids. The influence of yield stress on the meniscus flow Is discussed.
Birefringence–An important property of plastic substrates for magneto‐optical storage disks
Authors: Siebourg W. , Schmid H. , Rateike F. M. , Anders S. , Grigo U. , Löwer H.
Published: May 2005

Birefringence is an important substrate property for optical data storage media. The basic definitions of birefringence and its relation to the chemical nature of polycarbonate are outlined. The polarizability of the monomer unit, expressed in the rheo‐optical constant and the degree of remaining polymer chain orientation, determines the level of birefringence in polycarbonate disk substrates. Based on this theory, the theory of blending materials with positive and negative rheo‐optical constants Is developed, and the current work with polycarbonate/polystyrene blends is reviewed. The biggest disadvantage of the reviewed system Js that only binary systems with low LCST (lower critical solution temperature) (<240°C) can be formulated. Finally, we report on successful development work of a single‐phase blend of a modified polycarbonate with a special styrene‐acrylonitrile copolymer. The experimental results are compared with the theoretical expectations, and the implications on the injection molding of disk substrates are discussed.
Thermotropic liquid crystalline halatopolymers
Authors: Ibidapo T. Adesanya
Published: May 2005

Divalent metal (I.e.) Ba(2+), Ca(2+i), Mg(2+), Mn(2+), Cd(2+), Zn(2+), Pb(2+), and Sn(2+) salts of monovalent organic acids (i.e. p‐methoxycinnamic, cinnamic, p‐methoxybenzoic, and 4‐n‐butoxybenzoic) were synthesized via the double decomposition reaction from aqueous solution. Optical microscopy and differential scanning calorimetry (DSC) analysis showed that this series of salts formed nematic liquid crystals. DSC thermograms were characterized by broad nematic‐to‐isotropic transitions indicative of biphasic regions in which the nematic and isotropic phases coexist. These liquid crystalline salts were polymeric when melted due to ionic crosslinking which took place through the coordination of the divalent metal ion. Except Sn (2+) and Pb(2+), all the liquid crystalline halato‐polymers were spun into fibers.
Model‐Filled polymers. III: Rheological behavior of polystyrene containing cross‐linked polystyrene beads
Authors: Park M. , Gandhi K. , Sun L. , Salovey R. , Aklonis J. J.
Published: May 2005

The steady shear viscosity and dynamic moduli, at 180 and 200°C, of polystyrene composites, containing cross‐linked monodisperse polystyrene beads varying in diameter from 0.2 to 0.8 μm, are independent of bead size and cross‐link density, but increase with the volume fraction of beads. Steady shear viscosities exhibit power‐law regions up to 40% concentration of beads, but no yield stress. Storage and loss moduli are initially linear with frequency, on double logarithmic plots, with limiting slopes of 1.3 and 0.9, respectively. Uncross‐linked beads and beads cross‐linked with 0.1% divinylbenzene are destroyed by thermomechanical dispersion in the melt.
Optimizing blown film polyethylene using a merit function
Authors: Cantor Kirk M. , Harrison Ian R.
Published: May 2005

The extrusion of blown film polyethylene is a complex process characterized by a large number of interdependent process variables. In order to derive the set of process conditions necessary for a desired film solid state property, the processor normally utilizes a laborious trial‐and‐error method. In this work, a technique is described to establish more directly the set of extruder settings for producing film with an optimum value of a given property. Biaxial toughness was optimized in the present work, but the technique is applicable to any quantifiable film property.
Vortex formation in a dual‐cavity coat‐hanger die
Authors: Lee Kwong‐Yang , Wen Shu‐Heng , Liu Ta‐Jo
Published: May 2005

The effects of cavity shapes, particularly the expansion and contraction angles, and the Theological properties of polymeric liquids on vortex formation in the cuter cavity of a dual‐cavity coat‐hanger die have been examined. For power‐law fluids, a vortex may appear in the expansion side of the outer cavity, and the size of the vortex is influenced by the expansion angle, the power‐law index, and the Reynolds number. Two viscoelastic fluids were used in the flow visualization experiment; for an aqueous polyacrylamide solution, a vortex may appear in the contraction side of the outer cavity and this vortex is influenced by the contraction angle and the fluid elasticity, but no vortex was observed for a Boger fluid.