bluuebunny/crossref_metadata_2025 huggingface dataset:
Materialeinsparung durch aktiven Verschleißschutz
Authors: Wahl W.
Published: December 2004

Durch Abnutzung entstehen in den verschiedensten Bereichen der Technik erhebliche Materialverluste hauptsächlich bei Metall:Metall‐ und Metall:Mineral‐Berührung. Der dadurch entstehende beträchtliche Materialverlust nimmt zu durch die Erhöhung des spezifischen Durchsatzes eingesetzter Maschinen, des Arbeitens im Verbundsystem, höherer Rohstoffausbeutung, Einführung moderner Technologien bei Rohstoffgewinnung und Recycling und dem zunehmenden Wunsch, die durch solche Schäden entstehenden Folgekosten zu vermindern. Dabei ist nicht echte Rohstoffknappheit maßgebend sondern vielmehr die in Zukunft sich verändernde Relation der Steigerungsraten von Rohstoffkosten und Lohnkosten. Materialeinsparungen sind durch Anwendung der heute bekannten Grundlagen auf dem Verschleißgebiet möglich. Im einzelnen umfassen sie die Maßnahmen:

– Einsparen von Material bei Neuteilen,

– Einsetzen höherwertiger Werkstoffe,

– Einsetzen von Verbundlösungen und

– Regenerieren abgenutzter Teile.

Zahlreiche praktische Beispiele aus dem Bereich des Metall:Mineral‐ Verschleißes werden erläutert.

Durch diese Maßnahmen hat der Ingenieur die Möglichkeit, Rohstoffe einzusparen.
Bedeutung der Unregelmäßigkeit Gauß'scher Zufallsfolgen für die Betriebsfestigkeit
Authors: Gassner E. , Lowak H.
Published: December 2004

Die zum Teil widersprüchlichen Angaben im Schrifttum über den Einfluß des Unregelmäßigkeitsfaktors sind vermutlich darauf zurückzuführen, daß bei einschlägigen Untersuchungen neben dem Unregelmäßigkeitsfaktor auch noch andere Parameter unbeabsichtigt variiert wurden. Um zu einer Klärung beizutragen, wurden unter Zufallsfolgen von Axiallasten mit Merkmalen eines stationären Gaußprozesses Betriebsfestigkeits‐ Versuche an einem Kerbstab und an einer einschnittigen Fügung aus der Legierung AlCuMg2 durchgeführt und der Einfluß der Unregelmäßigkeit auf die Lebensdauer bestimmt. Die untersuchten Unregelmäßigkeitsfaktoren überdecken mit l = 0,99,0,7 und 0,3 den für die Betriebsfestigkeit interessanten Anwendungsbereich. Das gewählte Verfahren zur Generierung der Zufallsfolgen gewährleistet, daß der Unregelmäßigkeitsfaktor die einzige Variable unter den üblichen Parametern der Zufallsfolge bleibt.
Keramische Werkstoffe für Brennkammern von Fahrzeuggasturbinen
Authors: Grunke R.
Published: December 2004

Damit Fahrzeuggasturbinen im spezifischen Verbrauch mit den heute verwendeten Dieselmotoren konkurrieren können, sind hohe Temperaturen im Brennkammerbereich erforderlich; diese können mit Metallbrennkammern nicht realisiert werden. Als Brennkammerwerkstoff bieten sich hochtemperaturbeständige Sonderkeramiken an. Bei MTU wurden die in Frage kommenden Keramiken unter betriebsnahen Bedingungen auf ihre Eignung als Brennkammerwerkstoff untersucht. Besonders bewährt hàt sich siliziuminfiltriertes Siliziumkarbid. Bei weiterer Entwicklung ist auch die Verwendung anderer Keramiken dankbar.

Seit mehr als 40 Jahren wird versucht, anstelle von Hubkolbenmotoren Antriebsmaschinen mit ausschließlich rotierenden Teilen zu verwenden. Die vom Prinzip her einfache Arbeitsweise der Rotationsmaschinen war immer wieder ein Ansporn dazu, die damit verbundenen technologischen Schwierigkeiten in Angriff zu nehmen. So konnte in der Luftfahrt die Gasturbine mit ihrem günstigen Leistungsgewicht den Kolbenmotor in der Leistungsklasse über 500 PS völlig verdrängen.

Anfang der 50er Jahre begann man in den USA und in Großbritannien mit der Entwicklung von Fahrzeuggasturbinen. Die Schwierigkeiten, die dabei auftraten, sind bis heute noch nicht befriedigend gelöst. Bedingt durch die kleinen Abmessungen und ein ungünstiges Teillastverhalten entstehen Wirkungsgradverluste, die nur durch hohe Verbrennungstemperaturen ausgeglichen werden können. Damit zum Beispiel eine LKW‐Gasturbine mit 350 PS ähnliche Verbrauchswerte wie ein Dieselmotor erreicht, sind Turbineneintrittstemperaturen von etwa 1400 °C erforderlich. Da aus Gründen der Kosten und des Wirkungsgrades aufwendige Kühlkonzepte, wie sie in Fluggasturbinen eingesetzt werden, nicht in Frage kommen, ist die Realisierung dieser hohen Temperatur mit Metallteilen nicht möglich. Bereits bei einer Brennkammereintrittstemperatur von 1000°C werden etwa 5% der angesaugten Luft zur Brennkammerkühlung verwendet, was den spezifischen Verbrauch um etwa 8 g/PS h erhöht (1).

Diese Problematik sowie die beginnende Rohstoffverknappung und Rohstoffverteuerung führten zu der‐an sich nicht neuen‐Überlegung, die Heißteile einer Fahrzeugturbine aus Keramik zu bauen. Bereits während des zweiten Weltkrieges sowie in den 50er und 60er Jahren wurde versucht, Alumininumoxid für Turbinenschaufeln einzusetzen, was u. a. an der mangelnden Thermoschockbeständigkeit von Al2O3 scheiterte. Nun sind in den letzten Jahren, zunächst in USA und dann auch in Deutschland, die Bemühungen um den Einsatz von Keramik in Gasturbinen wieder verstärkt worden. Die Entwicklungsarbeiten sind z. Zt. in vollem Gange, wobei sich jetzt erste Tendenzen abzeichnen und auch einzelne Teilerfolge erzielt wurden (2).
The effect of design and operating conditions on melting in plasticating extruders
Authors: Tadmor Zehev , Klein Imrich
Published: December 2004

A previously proposed but further modified theoretical model for melting in plasticating extruders, in the form of a computer program, which predicts the amount of unmelted polymer at any point in the extruder, was used to simulate the effect of geometrical and operating variables on the melting performance of the extruder. The results indicate in increasing screw length required to complete melting with increasing throughput and a decreasing length of melting with increasing frequency of screw rotation. They further indicate the existence of an optimum barrel temperature for a maximum rate of melting, an optimum number of threads for a maximum melting rate, and a significant decrease in the rate of melting with increasing flight clearance. The effect of other geometrical variables and of operating conditions on the rate of melting and power consumption are also discussed.
The simulation of the plasticating screw extrusion process with a computer programmed theoretical model
Authors: Klein Imrich , Tadmor Zehev
Published: December 2004

A fundamental mathematical model of the plasticating extruder was assembled by combining a previously reported melting model with an improved melt pumping model. The validity of the model was tested with numerous experiments on 2 1/2 in. and 8 in. diameter extruders. The experiments were performed with low and high density polyethylene, plasticized polyvinyl chloride, rigid polyvinyl chloride powder, polypropylene, ABS and nylon 66. The mathematical model proved to be excellent in predicting pressure and plastic temperature profiles in the extruder channel, temperature fluctuation, solids content, and power consumption.
Resins and reinforced plastic laminates for continuous use at 650°f—II
Authors: Freeman J. H. , Frost L. W. , Bower G. M. , Traynor E. J. , Burgman H. A. , Ruffing C. R.
Published: December 2004

This paper is the third in a series describing work done under Air Force sponsorship to develop high temperature polyimide laminates for radomes and other parts for supersonic aircraft.

Twelve resin compositions are described and evaluated. Most were prepared from benzophenonetetracarboxylic dianhydride and one or more aromatic diamines. Modifying linkages such as amide, ether, benzimidazole, and oxadiazole were present in some cases.

A variety of precure and pressing conditions were studied, best results being obtained with a fully cured prepreg pressed at about 700°F and 200–1000 psi. Most of the laminates were made with E glass cloth, but some work was done also with S glass, Refrasil, and carbon cloth.

Initial flexural strengths on E glass of 35–60,000 psi at room temperature, and 20–40,000 psi at 600°F were observed for the better resins. On S glass, slightly higher strengths were observed together with values of about 10,000 psi at 700–1000°F. Aging data on E glass laminates show retention of at least 10,000 psi flexural strength at temperature for about 250 hrs. at 650°F, 1000 hrs. at 600°F, 5000 hrs. at 527°F, and 30,000 hrs. at 482°F.

Dielectric constant and dissipation factor at 10 Gc were found to be nearly constant at 3.5–4.4 and 0.005–0.01, respectively, for temperatures up to 662°F and for aging up to 1000 hrs. at 600°F. At frequencies of 60 c and 1 Kc, an increase of dissipation factor with temperature was found and was used as a measure of Tg.
The extrusion of polymers below their melting temperatures by the application of high pressures
Authors: Buckley A. , Long H. A.
Published: December 2004

A number of polymers have been “cold” extruded (i.e. at temperatures well below their normal melting temperatures) by the application of relatively high pressures. In all cases extrudates of relatively large cross‐sectional area have been produced, and non‐circular cross‐sections have also been extruded. The extruded products has been evaluated and the results discussed. In general it has been found that whilst extrusion gives an oriented product, the increase in tensile modulus is much less than for a comparably drawn fibre. This phenomenon has been discussed in terms of the changes in crystalline structure produced by extrusion.
Effect of melt history on polymer crystallization
Authors: Collier J. R. , Neal L. M.
Published: December 2004

As discussed in this paper, melt treatment prior to crystallization, apparently proceeds by the following stages: partial melting; an insensitive region; and at higher temperatures, deactivation of nucleation sites. The deactivation‐region onset temperature is quite dependent on the subsequent crystallization conditions and may not be observed in some polymers during crystallization from the melt. In addition, those polymers capable of being quenched directly from the melt to a non‐crystalline glassy state and subsequently crystallized by reheating to above the glass transition, do not exhibit any more than a partial melting type melt treatment effect. The deactivation regime absence is a result of the homogeneous nucleation that occurs during crystallization from the quenched glassy state at temperatures slightly above the glass transition.

Use of a metal‐ or glass‐constraining medium does mask (at least partially) the effect of melt history upon crystallization from the melt. In addition to the masking effect of a constraining medium, some of the controversy in the literature pertaining to the existence of a melt treatment phenomenon may arise due to degredation of some polymers prior to the onset of the deactivation regime. The crystallization conditions employed are also quite influential on the possible effect melt treatment can have since the melt history phenomenon is noted by its effect on subsequent crystallization.
On the characterization of nonlinear viscoelastic materials
Authors: Schapery R. A.
Published: December 2004

Starting with specific constitutive equations, methods of evaluating material properties from experimental data are outlined and then illustrated for some polymeric materials; these equations have been derived from thermodynamic principles, and are very similar to the Boltzmann superposition integral form of linear theory. The experimental basis for two equations under uniaxial loading and the influence of environmental factors on the properties are first examined. It is then shown that creep and recovery data can be conveiently used to evaluate properties in one equation, while two‐step relaxation data serve the same purpose for the second equation. Methods of reducing data to accomplish this characterization and to determine the accuracy of the theory are illustrated using existing data on nitrocellulose film, fiber‐reinforced phenolic resin, and polyisobutylene. Finally, a set of three‐dimensional constitutive equations is proposed which is consistent with nonlinear behavior of some metals and plastics, and which enables all properties to be evaluated from uniaxial creep and recovery data.
Flow properties of plasticized PVC: Reduction to composition and interaction variables
Authors: Schreiber H. P.
Published: December 2004

Existing theory of polymer flow has been applied to a definition of shift factors which reduce the widely different melt viscosity/shear rate diagrams of plasticized PVC compounds to well‐defined master curves. The master curves are temperature dependent and also define the flow properties of the unplasticized polymer on which a group of plasticized compounds is based. For given plasticizers, the value of the shift factor was found to depend on melt temperature and plasticizer volume fraction. Explicit relationships have been generated for three plasticizer systems; for these, melt viscosity/shear rate data can be precalculated over several decades of shear, and in the temperature range of 150–200°C. Absolute values of the shift factors depend on the type of plasticizer, and a correlation with polymer/diluent interaction parameters has been attempted. Initial results, valid only at high plasticizer volumes and near the reduced melt temperature of a polymer/plasticizer mixture, support the existence of such a correlation.
Flow properties of polyethylene melts
Authors: Mendelson R. A.
Published: December 2004

This discussion will illustrate some of the factors which go into the design of experiments required to solve problems in the field of plastics. Two quite diverse problems were considered. In the first case a series of experiments was described which provided a very general technique for predicting polyethylene flow behavior as a function of shear rate over a wide range of temperatures from a minimum of new data. In this case the experimentation concerned only the viscous aspect of flow and was not limited by the availability of special samples. In the second case it was desired to learn what the effect of a specific molecular structural variable was on the general melt rheological properties of polyethylene. This required the polymerization of special samples followed by detailed characterization by both solution property and melt rheological techniques.
Shear modification of polythene
Authors: Hanson D. E.
Published: December 2004

The changes occurring when polythene melts are subjected to shear, have been investigated using a rotating bob fitted into a ram extruder. In addition to chain scission, low density polythene exhibits reversible changes in mechanical and viscoelastic properties. The magnitude of the changes is controlled by total shear strain, and is related to molecular weight and long chain branching. The mechanism appears to be one of reversible disentanglement operating mainly on the large highly branched molecules. The work is relevant to various extrusion processes and to other long‐branched polymers.
Fatigue behavior of glass‐fiber fortified thermoplastics
Authors: Dally J. W. , Carrillo D. H.
Published: December 2004

This investigation deals with the fatigue behavior of a group of thermoplastics fortified with discontinuous glass fibers dispersed by an injection molding process. The thermoplastics included nylon, polystyrene and polyethylene reinforced with short (1/8 in.) and long (1/2 in.) glass fibers.

Several aspects of the fatigue behavior are included in the study. First, classical S–N curves were generated under fluctuating tension with R = 0.05 to show the loss of strength due to cyclic load application. Next, the extent of progressive fatigue damage was established by measuring the residual strength after cyclic loading. Finally, hypotheses pertaining to the fatigue mechanisms operative in all four materials were made based on microscopic examinations of sections removed from fatiguedamaged specimens.
Meaning and measurement of crystallinity in polymers: A Review
Authors: Kavesh S. , Schultz J. M.
Published: December 2004

A useful concept in polymer science is the degree of crystallinity—the fraction of the polymer that exists in a relatively ordered state. Methods of determination of the degree of crystallinity using density, infrared, thermal, N.M.R. and X ‐ray measurements are examined in light of modern notions of the structure of semi ‐crystalline polymers.
Studies on the stress relaxation of polystyrenes in the rubbery‐flow region
Authors: Narkis M. , Hopkins I. L. , Tobolsky A. V.
Published: December 2004

Relaxation modulus curves for narrow distribution and broad distribution polystyrenes are compared and the significant effect of molecular weight distribution on these curves is shown. An empirical three‐parameter equation is shown to describe the stress relaxation behavior of narrow distribution polystyrenes. New data for high molecular weight, narrow distribution polystyrenes are presented and used to extend the applicability of previous quantitative relations for higher molecular weights. The stress relaxation technique is shown to be sensitive to the type of plasticizer used at low concentrations.
The rheology of polypropylene—the influence of molecular weight distribution on melt elasticity
Authors: Petraglia G. , Coen A.
Published: December 2004

The structure of isotactic polypropylene, obtained by means of Ziegler‐Natta catalysis, can be characterized only by molecular weight distribution. The mechanism of stereospecific catalysis eliminates other variables, i.e., short and long branching. In this case it is possible to develop a rheological study dependent only by polydispersity. The spectrum of relaxation times of five samples of polypropylene have been calculated from swelling measurement in the molten state and from flow master curves. The molecular weight distribution of the samples has been calculated by means of the relaxation spectrum, as suggested by Ferry. This information has been compared with that obtained by a fractionation method. There is a good agreement between the calculated and measured polydispersity curves.
Description of tensile failure of viscoelastic materials under multiaxial loading
Authors: Dong R. G.
Published: December 2004

A description of tensile failure of polymeric materials under multiaxial loading has been formulated, based on a combination of ideas and implications derived from Smith's work on uniaxial tensile failure envelopes and the author's earlier theoretical work. Some simplification of the formal expressions was achieved by imposing restrictions that would assure that the uniaxial failure envelope is recovered under uniaxial tensile stress conditions and that the progression toward failure is monotonically increasing under monotonically increasing loads. The final result emerges as an extension of the uniaxial failure envelope applied to failure under multiaxial loads. Subsequently, the result is capable of describing rate effects to the same extent as can be described by the uniaxial failure envelope. This is an added capability over many of the existing multiaxial failure descriptions. Unfortunately, the result applied at best, only to those materials for which the uniaxial failure envelope applies; thus the generality is restricted. Some preliminary verification is presented for LX‐04‐1, a high‐explosive material composed of 85% HMX and 15% Viton by weight, using Peterman's results from 68°F biaxial tests. Further experimental work is underway.
On the solvent stress‐cracking of polycarbonate
Authors: Miller G. W. , Visser S. A. D. , Morecroft A. S.
Published: December 2004

The stress‐cracking of polycarbonate by a gaseous or liquid agent results from the diffusion of this agent into the polymer. The low molecular weight polymer fractions and the chain ends within the bulk of the polymer become more ordered during the diffusion and swelling process by their partial solubility in the crazing agent, causing crystallization. The creation of interfaces at areas of order‐disorder causes high shearing forces at this boundary and voids within the bulk of the polymer. These voids are then propagated as crazes or cracks at stresses much lower than the tensile strength of the polymer. Therefore, a stress‐cracking agent need not diffuse rapidly, but must be an effective environment for swelling and/or crystallization. Data from diffusion, density, thermal and molecular analyses are presented to support this mechanism.
Plasticating single‐screw extrusion theory
Authors: Chung Chan I.
Published: December 2004

Various solid conveying, melting, and metering theories developed for plasticating screw extrusions are reviewed. Some recommendations for improving the present melting theories are presented. It is pointed out that the overall performance of a screw extruder can be predicted only by combining the solid‐conveying, melting and metering theories into a complete mathematical package because the three functions of a screw extruder depend on each other and cannot be separated. A suggestion is made on how to combine these three theories.
Modulus of short carbon and glass fiber reinforced composites
Authors: Brody H. , Ward I. M.
Published: December 2004

A theoretical model for a short fiber reinforced composite is proposed. The composite is assumed to consist of an aggregate of sub‐units, each sub‐unit possessing the elastic properties of a reinforced composite in which the fibers are continuous and fully aligned. The elastic constants of a partially oriented composite are then calculated by the Voigt and Reuss averaging procedures, giving upper and lower bounds respectively for the composite modulus. Comparison is made with experimental data for such composites. The measured modulus of glass and carbon fiber composites is found to be given by the Reuss or lower bound, to a good approximation compared with the difference between the bounds, for fiber orientations ranging from almost isotropic to highly aligned.
Unstable flow of amorphous polymers through capillaries I. Velocity profiles of polymer having discontinuous flow curve
Authors: Bartǒs Otakar , Holomek Josef
Published: December 2004

Ciné film was employed for recording the movement of tracer particles, thus directly determining the velocity profile in the capillary flow of model materials of polybutadiene over a range of shear stresses relating to (1.) flow conditions in which there is no distortion of the regular stream of melt emerging from a capillary, (2.) severe surface fracture, (3.) elastic turbulence, (4.) oscillatory flow of melts with discontinuous flow curves. No qualitative difference was found between the velocity profiles in conditions (1) and (2); surface fracture is not related to laminar flow disturbances and originates at the capillary exit. Surface fracture must be distinguished from elastic turbulence. The streamline velocities undergo both local and time variations within the capillary under conditions of developed elastic turbulence; the wall velocity is non‐zero. A periodic pulsation of velocities occurs in the flow curve discontinuity region; it takes place throughout the capillary and is caused by stick‐slipping of polymer on the capillary wall. The frequency of velocity pulsations coincides with the frequency of extrudate variations.
Influence of reservoir diameter on the melt elasticity in capillary flow
Authors: Han Chang Dae , Kim Kwang Ung
Published: December 2004

An experimental study has been carried out to investigate the influence of the reservoir‐to‐capillary diameter (DR/D) ratio on the elastic properties of polymer melts flowing through capillary tubes. For the study, a capillary rheometer, described in an earlier paper by Han, was used with DR/D ratios of 3, 6, 9 and 12. Measurements were taken of wall normal stresses in high density polyethylene along the axis of the capillary, and the axial pressure profile was used to obtain the “exist pressure,” which is believed to be an elastic phenomenon. The analysis of the experimental data indicates that, for a given capillary length‐to‐diameter (L/D) ratio, the exit pressures first increase and then level off, as the DR/D ratio is increased. This behavior of the exit pressure is in accord with that of extrudate expansion which has also been determined in the experiment. This dependence of the exist pressure and extrudate expansion ratio on DR/D ratio is explained with the concept that the amount of recoverable elastic energy stored in the melt flowing through the capillary depends on the strain history, which the melt experiences on entering the capillary.
Thermally stable photoresist polymer
Authors: Kerwin Robert E. , Goldrick Michael R.
Published: December 2004

A new photoresist stable to 500°C has been developed. The addition of potassium dichromate to a polyamic acid, believed to be the condensation product of pyromellitic dianhydride and 4,4′‐diaminodiphenylether, results in a photosensitive polymer which can be cast or spun. The resultant film after exposure, development and post‐bake is a crosslinked aromatic polyimide. An efficient developing solution consisting of a 5:1 mixture of hexamethylphosphoramide and dimethylsulfoxide has been discovered. The system has been fully characterized in terms of composition, film formation, exposure, development, hardening and removal. This material has already proven useful as an area‐controlled, thermally stable dielectric and as a sputter‐etch resist. It has been demonstrated that under the conditions of sputter‐etching (bombardment of substrate with Ar, Ar+ species with energies from 1–300 eV) commercial photoresists, of the polyisoprene variety, char to the extent of being ineffective as a masking material. Under these same conditions, the thermally stable resist retains its film integrity and uniform sputter‐etch rate. An exemplary processing sequence is included as an appendix.
Some melt flow and mechanical design aspects of large extruders
Authors: Fenner R. T. , Williams J. G.
Published: December 2004

This paper examines two aspects in the design of large extruders. An analysis of the thermal problems in the flowing melt is given in terms of dimensionless groups and the results are applied to the scale‐up problem in extruder design. An analysis of the mechanical stability of extruder screws is also given including the effect of axial buckling and whirling. The results are examined as a possible limitation on extruder dimensions.
Properties of poly(vinylidene fluoride)
Authors: Stallings J. P. , Howell S. G.
Published: December 2004

The properties of fluorocarbon plastics have made them desirable for numerous new applications. Poly(vinylidene fluoride) (PVF2) can be easily extruded into films or fibers or injection molded into a variety of shapes. It was found that crystallinity, molecular weight distribution and polymer structure are important in establishing resin properties. Highly crystalline PVF2 with a narrow Gaussian molecular weight distribution gives specimens with optimum physical and chemical properties.
Fracture mechanics of polymers
Authors: Williams J. G.
Published: December 2004

A review of fracture mechanics and its relevance to designing with plastics is given. The basic philosophy of assuming the presence of flaws is developed, and the relevant equations are given. Data is presented for several polymers illustrating thickness and viscoelastic effects. A method of analysis for impact testing is then described together with some data. The unity of the data from a wide range of tests is emphasized.
Physical aging in plastics and other glassy materials
Authors: Struik L. C. E.
Published: December 2004

This paper surveys the basic aspects of physical aging. It shows that aging i s a general and important phenomenon found in all organic and inorganic glasses and in some metals as well. Moreover, the behavior of all these materials is very similar. It further shows that aging cannot be ignored in the testing of plastics, particularly in the prediction of their long‐term behavior.
Fatigue crack propagation in poly(methyl methacrylate): Effect of molecular weight and internal plasticization
Authors: Kim S. L. , Skibo M. , Manson J. A. , Hertzberg R. W.
Published: December 2004

In spite of the importance of fatigue behavior in engineering plastics, relatively few fundamental studies have been made of the effects of polymer structure, molecular weight, composition, and morphology on fatigue crack propagation (FCP). As, part of a broad program for the study of such effects, the role of molecular weight and internal plasticization has been studied in poly(methyl methacrylate) (PMMA) which had been specially prepared and characterized with respect to molecular weight, dynamic mechanical behavior, and, in some cases, stress‐strain response. As expected, values of fracture toughness,Kc, varied considerably as the molecular weight was rai ed, from 0.7 MPa, √matMv= 1.0 × 105to 1.1 atMv, = 4.8 × 106. However, a specific effect of fatigue was noted: over the same range ofKc, values of FCP rate decreased by two orders of magnitude as molecular weight was; increased. It is proposed that this high sensitivity is due to differences in the degree of chain disentanglement effected by the cyclic loading, with consequent differences in the strength of the craze preceding the crack. With PMMA plasticized internally with a low level (10 percent) of n‐butyl acrylate (nBA), the FCP rate andKc, were similar to those of controls, with very high rates shown. At higher nBA levels (up to 30 percent), the sensitivity of FCP rate to stress intensity factor range decreased considerably,Kc, increased by 30 percent and the pre‐exponential constant in the growth rate law increased. Plasticization weakens the polymer but at high degrees leads to enough hysteretic heating to induce local creep and crack blunting.
Oriented short glass fiber composites. III. Structure and mechanical properties of molded sheets
Authors: Kacir L. , Narkis M. , Ishai O.
Published: December 2004

Oriented short fiberglass mats prepared by the ERDE converging flow technique of fiber/glycerine dispersions were studied. Fiber orientation distribution in mats, prepregs and molded sheets were investigated by optical and X‐ray techniques. Longitudinal and transverse fracture surfaces of short fiberglass/epoxy molded sheets were analyzed. The effect of fiber length on tensile properties was also studied. The experimental results obtained on longitudinal, transverse, and off‐axis tensile modulus and ultimate strength were compared with classical elastic equations for continuous reinforcement.
Flexural fatigue of unidirectional fiberglass‐reinforced polyeste
Authors: Fesko Donald G.
Published: December 2004

Flexural fatigue data about a non‐zero mean stress are presented for unidirectional fiberglass‐reinforced polyester composites. The data are useful for the design of structural components and extend our knowledge regarding the mechanical performance of composite materials. In particular, the dependence of modulus, strength, and fatigue strength on glass content, both dry and wet, is described. Also, the extent to which design allowable stresses are influenced by minor impacts and by machining is discussed.
Wall slip and its implications in the design of single screw melt‐fed extruders
Authors: Worth R. A. , Parnaby J. , Helmy H. A. A.
Published: December 2004

The phenomenon of wall slip during the capillary flow of polymer melt is investigated for low and high density polyethylene. It is found that wall slip occurs in both cases, and that the effect is related to melt fracture. In addition, it is shown that a silicone fluid exhibits wall slip. The performance of the metering zone of a 38 mm diameter single‐screw extruder is discussed in relation to wall slip. It is suggested that the power consumption of the extruder is reduced as a result of slip at the polymer/metal interface. Results based on experiments with the silicone fluid tend to support this hypothesis. A theoretical analysis of the effects of wall slip upon throughput rate and power consumption for a one‐dimensional isothermal Newtonian case is included.
Crosslinking systems in the graft polymerization of chromium‐tanned collagen
Authors: Harris E. H. , Feairheller S. H.
Published: December 2004

Ten polyfunctional vinyl‐type monomers were graft polymerized with butyl acrylate or methyl methacrylate onto chromium‐tanned collagen in a redox initiated, emulsion‐type system. The thickness of the grafted leathers showed an increase ranging from 9 to 159 percent. The regression of total polymer on thickness gave a better fit than did bound polymer, the correlation coefficient being 0.774. The tensile load at break increased in all but one case, with a maximum increase of 70 percent over the control. Since the thickness increase was usually greater than the load increase, the tensile strength usually decreased. The changes, in tensile elongation were not always in agreement with those anticipated from crosslinked bulk polymers. In addition to these physical effects, inclusion of the polyfunctional comonomers generally reduced the amount of extractable polymer. A hypothesis is proposed to explain some of the observed effects.
Effect of rheological parameters on phase morphology of poly blends: A route to computer aided design and development of industrial polyblends
Authors: Plochocki A. P.
Published: December 2004

Set of procedures employing melt viscoelasticity functions for selecting components and composition of the binary polyblends and estimating minor phase domain size is introduced and illustrated with examples. The procedures intended for Computer Aided Manufacture of the polyblends (CAMOBLE) are based on shear stress dependent viscoelasticity ratios, and the selection of the composition exploits stress dependent synergism of the viscoelasticity functions. Also used is auxilary procedure for composition selection is based on verified blending laws accounting for interaction and shear effects. Evaluation of the performance characteristics (“mechanical properties”) is illustrated with a modified Kerner model.
The effect of initial morphology on the mechanical properties of ultra‐high molecular weight polyethylene
Authors: Zachariades Anagnostis E. , Kanamoto Tetsuo
Published: December 2004

Studies of the physical and mechanical properties of melt crystallized ultra‐high molecular weight polyethylene morphologies from melts with different thermal histories indicate that their properties depend on the degree of fusion of the powder particles during their processing and can be enhanced by heating the polymer above 220°C. The degree of cohesion of the powder particles and their initial morphology also have a significant effect on the deformability of the polymer in the solid state forming methods used to prepare high modulus and strength products.
Shrinkage as a measure of extended chain conformation
Authors: Jordon Mary E. , Juska T. D. , Harrison I. R.
Published: December 2004

Drawing of a semicrystalline polymer causes a molecular transformation from a spherulitic‐to‐fibrillar morphology. Shrinkage, which is a characteristic property of polymeric fibers, reverses, to a large extent, the extension that takes place during the deformational process of drawing. This paper focuses on the shrinkage behavior of various drawn semicrystalline polymers and the results are used as further evidence for the feasibility of a phase‐transition model whose mechanism can be generally termed “strain‐induced recrystallization.”
The effect of process and polymer variables on the light transmission properties of polypropylene tubular blown films
Authors: Bheda Jayendra H. , Spruiell Joseph E.
Published: December 2004

An extensive experimental study of the effect of processing and resin variables on the light transmission of polypropylene tubular blown film is reported. The resin variables investigated include melt flow rate (average molecular weight), molecular weight distribution, and the addition of a nucleating agent. Processing variables studied include blow‐up and draw down ratios, and frost line height (cooling rate). Increasing the draw down and blowup ratios and decreasing the frost line height generally lead to increased light transmission. Decreasing the resin melt flow rate, narrowing the molecular weight distribution, and the addition of a nucleating agent also improve light transmission. The overall light transmission properties of the films are dominated by their surface roughness characteristics, while the internal morphology of the films plays a secondary role. The changes in light transmission of the films in response to changes in processing or resin variables were traced to their effect on the surface texture and internal morphology.
Fracture characterization of tough polymers using the J method
Authors: Hashemi S. , Williams J. G.
Published: December 2004

The use of the J method to characterize fracture is described, and it is noted that smaller specimens may be used to obtain plane strain values than in conventional linear elastic fracture mechanics (LEFM) tests. Various methods of computing J are described, and the extrapolations necessary to define crack initiation are discussed. The various schemes and size criteria are then explored for a polypropylene copolymer, and it is found that the recommended ASTM procedure using energy works well. The method is then used to characterize several toughened polymers, and some discussion of the slope of the resistance curve is given.
Creep analysis of polymer structures
Authors: Trantina Gerald G.
Published: December 2004

One of the important aspects in designing polymer structures and predicting their lifetime is the computation of time‐dependent deformation. A tensile creep law for constant uniaxial stress was developed using talc‐filled polypropylene as an example. A simplified finite‐element creep analysis technique for polymer structures was developed with only one time step, an isochronous stress‐stress formulation, and a deformation plasticity‐type analysis, With an elastic analysis and this one‐step nonlinear analysis for a given time and temperature, the displacement of a critical location in the polymer structure can be calculated for any time and temperature without further finite‐element analysis. Comparisons of calculations with this one‐step analysis and with the standard time‐stepping analysis and experimental results for a beam in bending and a plate with a hole demonstrate the usefulness of this approach.
Geometry and nature of the interfacial layer in polyimide coatings
Authors: Startsev V. M. , Kiselev M. R. , Chugunova N. F.
Published: December 2004

A new approach to the quantitative evaluation of the thickness hi and the volume fraction Vi of the interfacial layer in polyimide coatings has been developed using the model of a one‐sided polymer coating as a three‐phase system (a substrate, an interfacial layer and a polymer matrix) and the method of differential scanning calorimetry. The new approach is characterized by the fact that a “pure” polymer matrix is modeled with the help of free films obtained on mercury. The formulas for the calculation of the thickness and volume fraction of the interfacial layer have been proposed. The value hi has been determined in polymer coatings of different thicknesses on aluminium foil. This parameter has been shown to be independent of the film thickness if the latter is not larger than the length of the interfacial layer. An assumption has been made about the “mechanical” origin of thick (> 1–5 μm) interfacial layers, and their relaxation character has been revealed.
The application of an exponential‐type function for the modeling of viscoelasticity of solid polymers
Authors: Garbarski Jacek
Published: December 2004

This paper presents some results of analytical work focused on finding the optimal description of the viscoelasticity of solid polymers. Memory functions of creep and relaxation are the basic functions in the constitutive equations. Applying a specific type of this kind of function is the purpose of this work. Based on the known exponential function, a new function called the “root function” has been created. Its very important feature is that the corresponding plots of spectra are of the same character as the curves of molecular weight distribution. The theory is verified by applying uniaxial creep tests. The experimental curves are compared with the numerical simulation based on the newly introduced root function. Apart from the purely phenomenological verification, the molecular weight distribution curves obtained by the traditional GPC (gel permeation chromatographic) method are compared with the spectra calculated analytically on the basis of the parameters calculated from the creep tests. A very good convergence of the curves confirms the selection of the memory function and the applied method.
Environmental aging and stress‐cracking of poly(ethylene terephthalate)
Authors: Jabarin S. A. , Lofgren E. A.
Published: December 2004

The environmental stress‐cracking behavior of poly(ethylene terephthalate), PET, has been studied by exposing PET sheet samples to a stress‐cracking liquid, at constant stress, for various periods of time. Samples evaluated are of equivalent molecular weights but vary in copolymer concentrations. The characterization of exposed samples includes examination of craze formation and density changes, measurement of tensile mechanical properties, and evaluation of changes in their enthalpies of relaxation by differential scanning calorimetry, DSC. Data analysis includes the correlation between the number of crazes formed as a function of exposure time and the nature of tensile failure. The relationship between measured enthalpy of relaxation and brittle vs. ductile failure is also established. Among the conclusions to be discussed are: (1) Samples with large numbers of crazes do not necessarily exhibit brittle failure during tensile evaluation; and (2) Brittle failure may be associated with crazing, but it must be caused by other factors.
Architecture with photopolymerization
Authors: Neckers D. C.
Published: December 2004

A brief summary of three‐dimensional photopolymerization using visible light photoinitiators and polyfunctional acrylates is presented. The work is directed by an effort to build actual models, in real time, using laser‐initiated photopolymerization in x, y layers of dimensional depth z.
Mechanistic study on chemically amplified resist systems using pinacol rearrangement in phenolic resin
Authors: Uchino Shou‐Ichi , Frank Curtis W.
Published: December 2004

Insolubilization mechanisms of chemically amplified resist systems using the pinacol rearrangement reaction have been investigated. An acid catalyzed dehydration of hydrobenzoin (HB) in a phenolic resin matrix proceeds by a consecutive reaction. HB converts to diphenylacetaldehyde (DAA), and subsequently the DAA produced reacts with HB to form 2,2‐diphenylmethyl‐4,5‐diphenyl‐1,3‐dioxolane (DPMDO), which is the dominant dissolution inhibitor of the HB resist. Benzopinacol (BP) and 1,1,2,2‐tetramethylethylene glycol (TMEG) react with acid to produce triphenylacetophenone and pinacolone respectively, which are the dissolution inhibitors of phenolic resin.
Progress in deep‐UV resists using CARL technology
Authors: Leuschner R. , Borndörfer H. , Kühn E. , Sebald M. , Sezi R. , Byer M. , Nölscher Ch.
Published: December 2004

Three positive working Si‐CARL resists for bilayer applications with oxygen‐RIE pattern transfer were investigated, and their lithographic performance at deep‐UV exposure was compared. With all three we obtained good focus latitudes for 0.35 μm lines and spaces ranging from 1.6 to 2.2 μm exposed with an 0.37 NA KrF‐excimer laser stepper. The zero bias exposure dose required for resist R1, of the diazodiketone type, is relatively high (70 mJ/cm2), but R1 has the advantage of not suffering from linewidth fluctuations caused by post‐exposure delay time effects. Processing for resists R2 and R3, which are based on acid catalyzed deprotection of t‐BOC‐imide and t‐butylester, respectively, had to be optimized to avoid bridging of isolated spaces after Chemical Amplification of Resist Lines (CARL). This bridging is caused indirectly by evaporation of triflate acid during PEB. Resist R2 needs only 8.5 mJ/cm2 for exposure but has a poor linewidth increase after CARL, which seems to be the reason for eroded 0.25 μm patterns after oxygen‐RIE. Resist R3 shows the steepest resist slopes and the best overall performance. The ultimate resolution for resists R1 and R3 is 0.25 μm, which, according to the Rayleigh equation for resolution, corresponds to a k‐factor of 0.37.
Anti‐reflective coating for deep UV lithography process enhancement
Authors: Barnes Gregg A. , Flaim Tony D. , Jones Susan K. , Dudley Bruce W. , Koester David A. , Peters Charles R. , Bobbio Stephen M.
Published: December 2004

We describe here performance enhancements provided by an anti‐reflective coating (ARC), developed for deep UV applications. The reduction in substrate reflections provided by the ARC layer results in significant increases in resolution capability and process latitude compared to single layer deep UV resist. Increased linewidth control and patterning capability for highly reflective, grainy, and topographical substrates is demonstrated.
Aerial image formation with a KrF excimer laser stepper
Authors: Preil M. E. , Arnold W. H.
Published: December 2004

We have studied the imaging characteristics of an excimer laser stepper as a function of laser wavelength. Focus, magnification, distortion, CD process window, and laser performance were all examined, and an operating wavelength was selected. The self‐metrology capabilities of both the laser and stepper were tested to insure that the system would set itself to the correct wavelength upon initialization, and maintain that setting during volume production activity. The use of an on‐line stepper image sensor to evaluate the quality of the aerial image, coupled with the built‐in wavelength tracking system as part of the laser optics, was found to provide the required closed loop system for wavelength and focus control. Based on these experiments, we have determined that a quick aerial image check before each production lot should suffice to insure focus control of better than 0.25 microns and magnification errors less than 15 nm during the entire time required to expose the lot.
Ester‐type photosensitive polyimide precursor with low thermal expansion coefficient
Authors: Matsuoka Y. , Yokota K. , Ogitani S. , Ikeda A. , Takahashi H. , Ai H.
Published: December 2004

For an ester‐type photosensitive polyimide precursor of low thermal expansion coefficient, the oxygen concentration in the curing process and the molecular weight of the polyimide precursor were found to control the properties of the polyimide. The effects of these factors on the thermal expansion coefficient, tensile strength, and modulus of polyimide film were investigated. Based on these results, a photosensitive polyimide with low thermal expansion coefficient, called the PIMEL TL‐series, was developed. Crack and delamination free multilayers were successfully achieved using this newly developed product.
A new positive‐type photoreactive polyimide precursor using 1,4‐dihydropyridine derivative
Authors: Omote Toshihiko , Yamaoka Tsuguo
Published: December 2004

A novel positive‐type polyimide precursor (BPDA/DDE) has been developed and examined. It is synthesized by the polycondensation of biphenyltetracarboxylic acid dianhydride and 4,4′‐diamino‐diphenyl ether, based on systems composed of dimethyl 1,4‐dihydro‐2,6‐dimethyl‐4‐(2‐nitrophenyl)‐3,5‐pyridinecarboxylate (nifedipine). Nifedipine photoconverted quantitatively to 4‐(2′‐nitrosophenyl)‐2,3‐dicarboxymethyl‐3,5‐dimethylpyridine (NDMPy) in a polyimide precursor film. It has been confirmed that nifedipine and NDMPy in the film act as a dissolution inhibitor and as a disolution promotor, respectively. The dissolution inhibition and promotion mechanisms were further investigated and subsequently expressed as follows:

Dissolution inhibition is due to resistivity of the polyimide precursor to an alkaline aqueous solution through intermolecular hydrogen bonding between — COOH in the polymer structure and — NH — in nifedipine.

Dissolution promotion is due to the hydrogen bond‐breaking by photoconversion from nifedipine to NDMPy and the newly formed intermolecular complex between the COOH and N in NDMPy.

The photoreactive polyimide precursor (BPDA/DDE), including 25wt% nifedipine, shows a 170mJ/cm2 sensitivity and a 5.5 γ value.