bluuebunny/crossref_metadata_2025 huggingface dataset:
Tensile failure of weathered polycarbonate
Authors: Sherman E. S. , Ram A. , Kenig S.
Published: December 2004

Weatherability of several UV stabilized and unstabilized grades of LEXAN® polycarbonate (PC) was studied by exposure in a xenon arc lamp weather‐o‐meter. The tensile properties of thin (0.2 to 0.3 mm) compression molded and thick (3.4 mm) injection molded samples were investigated as a function of exposure time and correlated with the changes in fracture morphology and molecular weight by scanning electron microscopy (SEM) and gel permeation chromatography (GPC). The elongation at failure was the essential mechanical property influenced by exposure. An initial decrease in elongation at failure, followed by a slight increase before the materials turned completely brittle (i.e.; failure without yielding), was correlated with a change in the fracture mechanism starting from the exposed surface of the samples. The initial decrease was caused by penetrating surface cracks, while the later increase in ultimate elongation resulted from the flaking off of the brittle surface layer. The UV stabilized grade remained more ductile, since its molecular weight remains fairly constant up to 1500 h of exposure, while the unstabilized grades decrease in molecular weight continuously from the start of exposure. The useful lifetime of the samples, defined by the complete loss of ductility, is approximately 1500‐2000 h of accelerated exposure, which corresponds approximately to 1 year outdoor exposure under Israeli conditions.
Effects of high oxygen pressure and temperature on the aging of polypropylene
Authors: Faulkner Douglas L.
Published: December 2004

Thin films of polypropylene were aged in air and in pure oxygen at pressures ranging from 0.051 to 4.24 MPa (7.4 to 614 psi) and temperatures from 60 to 90°C. Carbonyl formation resulting from polypropylene oxidation was monitored using infrared spectroscopy. The induction time for spectroseopically detectable oxidation coincided with a drastic reduction in tensile elongation for similarly aged tensile specimens. The induction time decreased monotonically with increasing oxygen pressures, while the maximum rate of carbonyl formation increased rapidly at lower oxygen pressures and increased slightly thereafter. The maximum rate of carbonyl formation as a function of oxygen pressure was shown to be consistent with a kinetic rate equation proposed by Stivala, et al. Nearly identical activation energies for the initiation of polypropylene oxidation were determined from reciprocal induction times for samples aged in air and in 4.24 MPa of oxygen (23.9 and 23.8 kcal/g‐mole, respectively). The similarity of activation energies suggests that the same mechanism is involved in the initiation step. Samples aged 3.6 times faster in 4.24 MPa of oxygen than in air at the same aging temperature.
Crosslinking of fluorocarbon elastomers: Characterization of crosslinking system to obtain transparent, tough materials
Authors: Miller G. A. , Sperling L. H.
Published: December 2004

Viton® GLT is a new low‐temperature fluoroelastomer with a Tg near −40°C. A study was made on methods of Crosslinking this material while retaining its transparency. Combinations of trimethylolpropane trimethacrylate, TMPTM, and triallyl isocyanurate, Diak® #7, were milled into Viton GLT. After molding, the materials were exposed to electron‐irradiation, cross‐linking the material. Transparent, tough materials were obtained for compositions containing about 3 percent TMPTM/3 percent Diak #7/3 Mrads, which had an extension of over 100 percent, a tensile strength of over 1000 PSI, excellent clarity, and low surface tack.
Curing characteristics of particulate‐filled thermosets
Authors: McGee Stuart H.
Published: December 2004

A model to describe the effect of participate fillers on the heat transfer and curing characteristics of a thermosetting polymer is presented. It is assumed that the reaction kinetics are not altered by the addition of the filler and that the thermal characteristics of the composite are adequately described by the “spherical inclusion model.” The model is used to examine the effect of fillers on several important molding characteristics: time‐temperature profiles, peak temperatures, extent of reaction, and gel time. Results are presented for the curing of a typical polyester resin with varying filler content and filler type (glass, calcium carbonate, and aluminum). These results indicate that:

mold cycle time can be reduced at higher filler content by increasing the mold temperature without inducing thermal degradation, and

the progression of cure fronts through the thickness of the mold is significantly altered with increasing filler content; at low filler content the cure front progresses from the centerline toward the wall; at higher filler content, the cure front progresses from the wall toward the centerline.
Blends of EPDM and sulfonated ethylene‐propylene‐diene (EPDM) rubber with polypropylene: Structure, physical, and rheological properties
Authors: Duvdevani I. , Agarwal P. K. , Lundberg R. D.
Published: December 2004

Blends of ethylene‐propylene‐diene (EPDM) and of metal‐neutralized, Sulfonated EPDM elastomers with polypropylene were prepared, and their structure‐property relationships were investigated. Extensive rheological measurements, including linear viscoelastic dynamic mechanical studies, were conducted on the blends. As might have been expected, the properties were a strong function of the blend compositions. Both blend systems exhibited multiple transitions indicative of molecular incompatibility of the blend components. These observations are consistent with the morphologies that were observed by scanning electron microscopy using selective extraction techniques. Both blend systems revealed two continuous interwoven phases consisting of elastomer and polypropylene. However, on a relative basis, the moduli and flow of the two blend systems differed significantly; blends of sulfonated EPDM possess higher moduli and lower flow values. The physical and flow property differences between the two systems are directly attributed to the difference in the structure of the elastomer components.
Stress‐induced diffusion and chemical reaction in nonhomogeneous velocity gradient fields
Authors: Akay G.
Published: December 2004

The theoretical analysis of dispersion with or without stress‐induced diffusion and stress‐induced chemical reaction during laminar flow of viscoelastic fluids in capillaries is given. The results are applied to diffusion and degradation in polymers under nonhomogeneous velocity gradient fields. It is shown that the concentration profiles during dispersion are strongly dependent on axial and radial positions in the presence of stress‐induced diffusion. Stress‐induced degradation rate of macromolecules during capillary flow decreases if the macromolecules are subject to stress‐induced diffusion.
The curing of a bisphenol A‐type epoxy resin with 1,8 diamino‐p‐menthane
Authors: Donnellan Thomas , Roylance David
Published: December 2004

Differential Scanning Calorimetry(DSC), Torsional Braid Analysis (TBA), and Fourier Transform Infrared Spectroscopy (FT‐IR) were used to study the cure characteristics of an epoxy system that utilized a sterically hindered amine curing agent. The apparent activation energy was found to be 13.3 kCal./Mol. by DSC and 12.8 kCal./Mol. by FT‐IR. Resin volatility hindered useful application of conventional TBA techniques. The resin was found to react to a partially cured (52%) state at room temperature and then vitrify. Samples stored for a two‐month period showed no advance in cure state. Subsequent application of heat caused resin devitrification and advance to a more fully cured state. The isothermal curing behavior was studied in a temperature range from 100° to 150°C.
Devolatilization of polymer melts in single‐screw extruders
Authors: Biesenberger J. A. , Kessidis G.
Published: December 2004

Polymer melt devolatilization (DV) was studied using a single‐screw extruder with extruder RPM and polymer flow‐rate as the key parameters varied. DV efficiency was studied at atmospheric pressure under nitrogen and also at reduced pressure. Preliminary results are applied to current mathematical models.
Influence of the thermal history on dielectric properties of poly(vinyl chloride)
Authors: Calleja R. Díz , Ribelles J. L. Gomez
Published: December 2004

In this paper, we report dielectric permittivity and loss of poly (vinyl chloride) samples that have received three different thermal treatments: (a) as received, (b) quenched from 110°C to 20°C and (c) slow cooled at 5°C/h. There are several observations: first, the secondary (β) loss peak‐is not representative of a simple mechanism of transition, in agreement with results of other authors (10), second, in the glass transition zone, there are clearly two peaks (α1 and α2)—α1, is a typical peak of an amorphous glass transition; the second, α2, has possibly a crystalline origin—and, third (and the most interesting fact), there is an increase of the loss tangent in the intermediate zone between α and β peaks showing a new relaxational peak with high activation energy (70 Kcal/mole), in agreement with dynamic mechanical results (6).
On the fickian diffusion of organic penetrants in glass polymers
Authors: Tosun I. , Yilmaz L.
Published: December 2004

Fickian diffusion of organic penetrants in glassy polymers is formulated as a moving‐boundary problem, and the effect of concentration‐dependent diffusivity on the concentration distribution is investigated. The solutions obtained for concentration‐dependent and constant diffusivity cases are compared. The results show that the concentration distribution curves differ both quantitatively and qualitatively. It is concluded that the sharp advancing boundary between the glassy and rubbery regions is due not only to the discontinuous change in the physical properties of these regions but also to the strong concentration dependency of diffusivity.
Development of industrial polyolefin blends using melt rheology data
Authors: Plochocki A. P.
Published: December 2004

The review of current knowledge of the composition dependence of polymer‐blend processability and morphology shows that development of industrial blends requires use of a semiempirical approach, based on the particular rheological composition (PRC) concept. Selecting blend composition in the close proximity to PRC and employing factorial experiments for the mixing process allows the development of successful industrial polyethylene/polypropylene blends designed for film and blow‐molding applications.
Remarks on non‐shear thinning elastic fluids
Authors: Binnington R. J. , Boger D. V.
Published: December 2004

In response to difficulties encountered in measuring and reproducing the flow properties of Boger fluids (dilute solutions of polyarcylamide in corn syrup), Choplin, et al. proposed it particular variety of lubricant (Emkarox) and also solutions of polyacrylamide (Pusher 700) in mixtures of glycerine and water as better model fluids for molten polymers than the original Boger fluid. In response to this work it is argued that the model fluid systems proposed by Choplin, et al., although interesting in concept, have insufficient elasticity and hence are of limited potential for use in investigative work in polymer fluid mechanics. Of all the highly elastic constant viscosity fluids available, the polyisobutylene‐polybutene system is the most attractive. Both the properties of this organic Boger fluid and the original Boger fluid, are entirely consistent with simple fluid theory.
Dynamic behavior of a single screw plasticating extruder part I: Experimental study
Authors: Nelson R. W. , Chan D. , Yang B. , Lee L. James
Published: December 2004

The dynamic responses of a 2–1/2 inch single screw plasticating extruder and extrusion line were investigated. Step changes in screw speed, take‐up speed, back pressure, and processing materials were used to determine the transient responses of barrel pressures, die pressure, melt temperature, and extrudate thickness. Dynamic responses of the entire extrusion line can be explained by the flow mechanism of the extruder and the logical properties of the polymer used. A capillary rheometer was also used to determine if it could simulate pressure responses in the extruder for screw speed changes. Results showed that capillary rheometer was helpful in estimating the short term pressure responses in the die.
Dynamic behavior of a single screw plasticating extruder part II: Dynamic modeling
Authors: Chan D. , Nelson R. W. , Lee L. James
Published: December 2004

The dynamic response of a 2.5 inch plasticating extruder and the extrusion line are modeled using high density polyethylene and acrylics us extrudate. Screw speed, back pressure valve position, and material changes are used as forcing functions. Three fundamental transfer functions in the Laplace domain: a first order, a second order, and a lead‐lag, are developed to simulate the short term and long term responses of temperatures, pressures, and extrudate thickness. A kinetic‐elastic model which can predict rheological properties of non‐Newtonian, viscoelastic materials is also applied to the pressure responses of the extrusion process. This model can fit the experimental data well but due to the complexity involved in its parameter setting, more modifications are required before it can be applied for the control of extrusion process.
Stress‐Strain isotherms for stereoirregular and stereoblock cis‐trans polybutadienes
Authors: Sharaf M. A. , Mark J. E. , Gunesin B. , Julemont M. , Teyssié P.
Published: December 2004

Gamma radiation and high‐energy electrons were used to crosslink two types of polybutadiene (PBD), the first having random cis‐trans‐vinyl contents and the second consisting primarily of blocks of cis units and blocks of trans. The resulting elastomers were studied in elongation in the unswollen stale, generally at 5°C, and in swelling equilibrium in a thermodynamically good solvent. Stress‐strain isotherms obtained for the random‐PBD networks did not show upturns in the reduced stress [f*] at high elongations, which is consistent with their non‐crystallizability. The stereoblock polymers were found to be crystalline, with melting points ranging from 14 to 65°C. Attempts to achieve strain‐induced crystallization in the stereoblock networks by judicious choice of temperature were unsuccessful as judged by the absence of any significant upturns in [f*]. Values of the elasticity constants 2C1 and 2C2, and the molecular weight between crosslinks were similar to those obtained from the linear portions of the isotherms previously reported for high‐cis and high‐trans PBD, which readily undergo strain‐induced crystallization.
Comparison of the hole pressure and exit pressure methods for measuring polymer melt normal stresses
Authors: Baird Donald G. , Read M. D. , Pike R. D.
Published: December 2004

There has been considerable controversy over whether one can extract the primary normal stress difference (N1) for polymer melts from hole pressure (PH) and exit pressure (Pex) data. In this paper values of PH and Pex are obtained for three polymer melts in the same slit‐die apparatus under the same operating conditions. It is found that there is a good correlation between values of N1 obtained by means of a cone‐and‐plate rheometer and those obtained by means of PH data and the Higashitani‐Pritchard theory. On the other hand, values of N1 obtained by means of Pex data for polystyrene were two to five times higher than those obtained by means of the cone‐and‐plate device. For the lower molecular weight low density polyethylene (LDPE) sample, values of Pex were found to be both positive and negative. For the higher molecular weight LDPE sample, values of Pex were found not to increase monotonically with with σw. Hence, it was difficult to obtain unequivocal values of N1 for LDPE.
Effect of ductility on the fatigue behavior of epoxy resins
Authors: Lorenzo Luis , Hahn H. Thomas
Published: December 2004

The effect of ductility on fatigue behavior was studied using two DGEBA‐based (diglycidyl ether of bisphenol A) epoxies: a ductile Epon 815/Versamid 140 and a brittle Epon 828/Epon Z. Failure modes were different although normalized stress‐life relations were similar for both resins. Two competing failure mechanisms were identified: viscoelastic creep, and nucleation and coalescence into a main crack of microcracks. No signs of crazing or fibrillation were detected. The plastic elongation during fatigue was larger in Epon 815/Versamid 140. Fracture sources showed cracked material surrounded by a region of stable growth of the main crack. In the brittle Epon 828/Epon Z cracked material was scarce and the crack initiation region was clean, especially at high stress levels. Discontinuous crack growth bands and striations were seen in the stable crack growth regions. During unstable propagation the crack advanced at different levels joined by deep cleavage steps. Branching of the main crack occurred only in the brittle resin at the final stage of propagation.
Dynamic dielectric analysis: Nondestructive material evaluation and cure cycle monitoring
Authors: Kranbuehl D. , Delos S. , Yi E. , Mayer J. , Jarvie T. , Winfree W. , Hou T.
Published: December 2004

Dynamic dielectric analysis (DDA) has been used to study curing polymer systems and thermoplastics. Measurements have been made over a frequency range of six decades. This wide range of frequencies increases the amount of information which can be obtained. The data is analyzed in terms of the frequency dependence of the complex permittivity ε*, specific conductivity σ(ohm−1cm−1), and the relaxation time τ, parameters which are characteristic of the cure state of the material and independent of the size of the sample. Dynamic dielectric measurements have been used to monitor polymer processing in UDEL‐P1700, LARC‐160, polyphenyl quinoxaline (PPQ), and Epon 828 cured with Agent U. Dynamic dielectric measurements have been correlated with viscosity for the polysulfone thermoplastic UDEL‐P1700 and with viscosity and ultrasonic measurements on the DGEBA type epoxy Epon 828 cured with Agent U. The experimental results suggest that when ionic processes dominate the dielectric response, the intensive property σ is a good monitor of the resin's viscosity. The results show that the dielectric relaxation time τ can be used to monitor the state of the system and the extent and rate of the reaction. Solvent evolution can also be easily observed.
Dielectric modeling of the curing process
Authors: Lane John W. , Seferis James C. , Bachmann Michael A.
Published: December 2004

Dielectric data from an epoxy resin system were used as the foundation for dielectric modeling of the curing process. This resin system (DGEBA‐polyamide) was chosen as an easily processible model system. Dielectric average relaxation times, defined as the reciprocal of the angular frequency at which the loss component of the dielectric constant reaches a maximum, were determined for a 40°C isothermal cure. The changes in the average relaxation time through the cure exhibited similar behavior to those for viscosity, which inspired the correlation of the two properties. The dielectric relaxation time was modeled using a six‐parameter model analogous to that used for viscosity. The model parameters were in turn associated with both intrinsic properties of the system and reaction kinetics describing the cure. The possibility of extending the relaxation time model for use with single‐frequency data by means of a time‐frequency correlation was also investigated. Combined, these two modeling methodologies provide a powerful constitutive approach for describing dielectric properties of thermosetting polymers during cure.
The effect of additives and drawing temperature on gamma‐ or ultraviolet‐radiation induced oxidative degradation of drawn high density polyethylene
Authors: Tincer T. , Cimen I. , Akay G.
Published: December 2004

The effects of drawing temperature and the presence of various types of additives on gamma and ultraviolet radiation induced oxidative degradation of high density polyethylene have been studied. Uniaxial drawing of the polymer was conducted at 60, 80, and 100°C. The additives were an antioxidant, light stabilizer, and carbon black, used in various combinations, Oxidative degradation was followed from carbonyl formation by IR spectroscopy. It is found that at a given draw ratio, the oxidative degradation is retarded when the drawing temperature is increased, irrespective of whether or not the polymer contains any additives in any combination. This is due to the decrease of the surface and/or bulk microcracks formed during the drawing process at high temperature. Carbon black/antioxidant mixtures were shown to be antagonistic, while a carbon black/light stabilizer mixture resulted in a synergetic effect in drawn or undrawn materials.
Steady state multiobjective optimization of continuous copolymerization reactors
Authors: Farber Jorge N.
Published: December 2004

The multiobjective nature of optimization problems related to homopolymerizaton and copolymerization processes implies a vector objective formulation for a correct approach. Two copolymerization systems, methyl methacrylate‐vinyl acetate (MMA‐VA) and styrene‐acrylonitrile (ST‐AN) are simulated, and some aspects of the steady state optimality of continuous operation are analyzed. The determination of non‐inferior sets through the concept of Pareto optimality permits a clear decision on trade‐offs related to operating conditions and product specifications.
Qualitative and quantitative analysis of multilayer coextruded and laminated films
Authors: Mirabella Francis M.
Published: December 2004

The packaging industry is undergoing a period of rapid expansion in the use of multilayer and coextruded containers. This presents a challenge to the analytical chemist, who must characterize these extremely complex structures. The state of the art for the production of the new generation of containers, including methods, materials and structures, will be briefly reviewed. The applications of such containers and the motivations for the analysis of the structures involved will also be reviewed. The methods for the analysis of these multilayer and coextruded structures will then be considered in detail. The characterization of the surfaces involved will be emphasized. Techniques to identify, quantify, and determine the orientation of the structures will be discussed. The use of infrared spectroscopy (with emphasis on internal reflection spectroscopy) for the identification of the materials in these structures will be discussed. Also, the use of infrared spectroscopy in quantitatively determining the composition and orientation of the structures will be presented. The use of optical microscopy and combined microscopy/infrared spectroscopy for the quantification of the layer structures will be discussed. The use of auxiliary techniques for the completion of the analysis of the complex layer structures will be presented.
A mass transfer model for a twin‐screw extruder
Authors: Secor R. M.
Published: December 2004

A mass transfer model was developed to represent the desorption of a volatile species from a molten polymer in an extruder consisting of co‐rotating twin screws in a figure‐eight bore. The melt undergoes a series of alternating exposure and mixing processes while being transported axially through the device. The model relates the ratio of entrance to exit concentrations of the volatile species to the dimensions of the screws, the rate of their rotation, the rate of polymer flow, and the diffusion coefficient of the volatile species in the polymer. Experimental data, obtained with a halocarbon‐polybutene system in a twin‐screw extruder, were compared with predictions of the model. For the observed performance, the model predicts a process screw length about 14 percent below the actual screw length in the experimental extruder.
Processing of polyurethane/polyester interpenetrating polymer networks by reaction injection molding (RIM). Part I: Design of a high pressure RIM system
Authors: Nguyen Luu T. , Suh Nam P.
Published: December 2004

This is the first of a three‐part paper investigating the feasibility of processing polyurethane/polyester Interpenetrating Polymer Networks (IPN) by Reaction Injection Molding (RIM). The fundamental mixing process is discussed. Various approaches reported to analyze mixing are also critically reviewed. Good part quality in RIM mixing activated systems suggests the need for the creation of a rapid and intense turbulent state within the small impingement chamber. In order to generate the conditions of reactive components intermingling down to submicron dimensions, a high pressure RIM unit was built and tested. The device can inject reactants at high stream Reynolds numbers (around 10,000) and impingement pressures (up to 100,000 psi, 6,895 bar.).
Processing of polyurethane/polyester interpenetrating polymer networks by reaction injection molding. Part II: Mixing at high reynolds numbers and impingement pressures
Authors: Nguyen Luu T. , Suh Nam P.
Published: December 2004

The impingement mixing process is analyzed considering the characteristic times of all the mechanisms involved. Two models of the mixing phenomenon are postulated; one takes into consideration the energetic nature of the shearing and stretching mechanisms during impingement while the other calls for the statistical variations in the kinetic energy dissipation process. Experimental data are presented to document the mixing scale obtained at high stream Reynolds numbers and impingement pressure. Model fluids are used on several occasions to characterize this scale. The best technique, however, involves mixing polyurethane with an inert component, dissolving the latter after gelation of the polyurethane network, and observing stereologically the ensuing morphology. Results indicate that high Reynolds numbers and impingeme it pressures reduce the scale of mixing to submicron dimensions. Autocorrelation coefficients are derived from the morphologies obtained after gelation. The initial slopes and oscillations in the correlograms are found to be good descriptive features of the degree of mixing in reaction injection molding (RIM).
Analysis of adhesive tensile test methods
Authors: Devries K. L. , Gramoll K. C. , Andersen G. P.
Published: December 2004

A common bond strength evaluation method is the tensile butt test. However, it is the opinion of the authors that the interpretation of the experimental results obtained from such a test often leaves much to be desired. The results of finite element analyses of butt tensile tests are presented, The stresses in the joints are not uniform as P/A would suggest. It can be argued that failure is more closely related to local extremes in stress than it is to the average stress generally reported. As added support for adhesive fracture mechanics, the analysis of butt tensile joints indicates that the maximum stress occurs at the edge of the joint. The location of the maximum energy release rate,G, varies with the ratio of thickness to diameter (h/D) of the adhesive. For a given “inherent flaw” size,Ghas a maximum value in the interior of the joint for smallh/dand at the bond edge for largeh/D.Studies of a transparent adhesive‐adherent system demonstrated that failure initiated at the points of maximum, energy release rate. The value of the failure load was also consistent with the trend predicted by fracture mechanics.
Photochemistry of azide‐phenolic resin photoresists
Authors: Hashimoto Michiaki , Iwayanagi Takao , Shiraishi Hiroshi , Nonogaki Saburo
Published: December 2004

The photochemistry of a negative working photoresist, MRL, composed of poly(4‐hydroxystyrene) and an aromatic monoazide compound, 4‐azido‐4′‐methoxychalcone, has been examined, The major products of photolysis of MRL films are primary amine, secondary amine, and poly(4‐hydroxystyrene) with increased molecular weight. The polymeric secondary amines are generated from the nitrene insertion into the backbone carbon‐hydrogen bonds of the polymer. Hydrogen abstraction from the polymer by the nitrene with subsequent polymer radical recombination results in the increase in the molecular weight of the poly(4‐hydroxystyrene), rendering the exposed areas insoluble in both aqueous alkaline and organic developers. Rapid decrease in the dissolution rate of the poly(4‐hy‐droxystyrene) with increasing molecular weight is separately ascertained.
Soluble polysilanes: An interesting new class of radiation sensitive materials
Authors: Miller R. D. , Hofer D. , Fickes G. N. , Willson C. G. , Marinero E. , Trefonas P. , West R.
Published: December 2004

All high molecular weight polysilane derivatives are characterized by a very strong electronic absorption in the‐UV spectral region. The position of this absorption and the molar extinction coefficients are functions of both the nature of the substituent and the molecular weight. In this regard, both the λmax and the ϵsi‐si increase rapidly at first with increased catenation and approach limiting values al around 100 to 150 monomer units. Irradiation of these polysilane derivatives leads predominantly to chain scission and molecular weight reduction although the scission ing/crosslinking ratio is dependent on the nature of the substituents. The mechanism of the photodegradation involves both the extrusion of substituted silylene fragments and the formation of silyl radicals. Lithographically, we have exercised the polysilanes in two configurations: (1) O2‐RlE etch resistant barriers in multilayer structures and, (2) thin imaginable layers for O2‐RIE image transfer. In each case, the stability of the silicon polymers to O2‐RIE conditions is due to the formation of a thin skin of oxide. In the case of the bilayer configurations, the images have been developed both by conventional wet development and by excimer laser ablation at either 308 or 248 nm prior to image transfer. Using either mode, we have been able to generate and transfer submicron images without difficulty. Finally, the strong optical absorption of the polysilanes, coupled with the observed bleaching upon irradiation, suggests potential as contrast enhancing materials. The contrast enhancement gained by the use of a polysilane layer has been modeled by computer simulation and demonstrated experimentally.
Submicron lithography in Japan
Authors: Shibayama Kyoichi , Kato Tadao
Published: December 2004

1Mbit D‐RAM. the most advanced VLSI device, is realized by a high performance stepper with the conventional optical techniques. However, as the optical lithography has an inherent limit of resolution, new technologies are being developed rapidly for the development of new generation VLSI devices (4M‐16Mbit D‐RAM) using shorter wavelength photons of i‐line. Electron beam (EB) lithography is already in practical mask making products, but the resolution limit is about 0.5 μm because of proximity effects. In order to make higher resolution and higher precision masks, high voltage EB technique is being developed to minimize the proximity effect, and fabricated 0.25 μm line and space by a single scan at 50kV. X‐ray technology 1; becoming practical after a long laboratory‐level study, using high performance X‐ray resists (CPMS: chlorinated polymetylstylene). Focused Ion Beam (FIB) technology has been anticipated for its capability of submicron lithography due to a reduced proximity effect. High speed submicron Si MOSFET and GaAs MESFET with 0.25 μm gate have been fabricated using FIB technology. Activities of submicron lithography technology in Japan (optical stepper, EB, X‐ray, and FIB) are described.
The reduction of reflective notches using “dyed” resist
Authors: Watts Michael P. C. , Debruin David , Arnold William H.
Published: December 2004

Variation in line width caused by light scattered from the substrate (reflective notching) is a major problem in VLSI lithography. This paper demonstrates the reduction of reflective notches using a resist with increased absorptivity (a dyed resist). The optimal set of process conditions which minimize line width variations is explored.
Performance prediction of weldline structure in amorphous polymers
Authors: Kim Sang‐Gook , Suh Nam P.
Published: December 2004

The presence of a weldline generally reduces the mechanical strength of injection molded parts. A typical remedy to eliminate the problem of weak weldline structure has been to increase the melt temperature. This, however, is not an acceptable solution in some situations. A general solution to the weak weldline problem requires an in‐depth understanding of the thermomechanical history of the injection molding process. A theoretical model for the strength of weldlines is presented that provides a comprehensive physical insight of the bonding process at the weldline interface. The model is based on the self‐diffusion of molecular chains across the polymer‐polymer interface and the frozen‐in orientation that remains parallel to the interface. Both factors are analyzed separately and then superimposed to predict the strength of weldlines from known processing conditions and geometry. Experimental results show good correlation with predictions.
Stress development in supported polymer films during thermal cycling
Authors: Tong H. M. , Hu C.‐K. , Feger C. , Ho P. S.
Published: December 2004

A simple and in‐situ bending‐beam technique has been used to investigate the stress‐temperature relationships for three different polymer coatings (viz, poly(methyl methacrylate), FR‐4 epoxy resin, and an amide‐imide polymer) during thermal cycling. With this technique, we were able to detect stress relaxation near the polymer's glass transition or caused by cracking of the polymer. Knowing the Poisson's ratio and Young's modulus for the polymer, this technique also allows calculation of the polymer's thermal expansion coefficient from measured thermal stress data. The calculated thermal expansion coefficient of poly(methyl methacrylate) (7 × 10−5/°C) is in good agreement with literature values (5 to 9 × 10−5/°C).
A study on polymer blending microrheology part 3: Deformation of newtonian drops submerged in another newtonian fluid flowing through a converging cone
Authors: van der Reijden‐Stolk C. , Sára A.
Published: December 2004

The theory of drop deformation in steady elongational flow is extended to the non‐steady elongational flow in a converging cone, Experiments with different fluid viscosities were carried out and compared with the theory, which is valid only for low deformations. The theory describes the drop deformation satisfactorily and under certain conditions even for higher deformations than expected.
Throughput‐pressure relationships for power law fluids in single screw extruders
Authors: Rauwendaal Chris
Published: December 2004

A simple expression is presented describing the volumetric throughput in a single screw extruder as a function of the pressure gradient with the dependence on the power law index included. Analytical expressions have also been developed for the optimum channel depth and helix angle for power law fluids.
Effect of intramolecular reactions in multifunctional step growth polymerizations in cascades of continuous‐flow, stirred‐tank reactors
Authors: Gupta Santosh K.
Published: December 2004

A simple kinetic model describing intramolecular reactions in multifunctional step growth polymerizations of RAj monomers is presented. The model is far simpler than more detailed kinetic or Monte Carlo models which pose severe numerical difficulties close to gelation. The formulation presented is quite general, but it requires a relationship for the ensemble‐cum‐time average number of rings, rn, per molecule having n RAj units. A very simple yet intuitively correct equation has been chosen for rn, which involves an empirical parameter 𝒜 Results on cascades of homogeneous continuous‐flow stirred‐tank reactors (HCSTRs) show trends which are physically expected. The present formulation could possibly be used for scale‐up of HCSTRs, with 𝒜 obtained experimentally. It is hoped that future studies using rigorous models would lead to more fundamental and improved relationships for rn.
Structural studies on ethylene‐tetrafluoroethylene copolymer: III. Deformation mechanism of row‐crystallized film
Authors: Tanigami Tetsuya , Yamaura Kazuo , Matsuzawa Shuji , Ishikawa Masazumi , Miyasaka Keizo
Published: December 2004

Wide‐angle X‐ray diffraction, small‐angle X‐ray scattering, density, stress‐strain, and dynamic viscoelastic measurements have been applied to a row‐crystallized ethylene‐tetrafluoroethylene copolymer film prepared by extrusion from the melt under extension to investigate the deformation mechanism upon stretching. It is shown that the deformation below the temperature of the phase transition (the order‐disorder transition from the crystal phase to the mesophase) (Th) is somewhat like that of “hard” elastic materials which is associated with micro‐void formation, and that the deformation above Th is rubber‐like, associated with bending of the lamellae. Gas permeability measurements have also been used for the stretched films to investigate the supermolecular structure, and the results support the above description.
Molecular weight and molecular weight distribution from dynamic measurements of polymer melts
Authors: Tuminello W. H.
Published: December 2004

A method for determining the molecular weight distribution (MWD) of a polymer melt has been developed using the dynamic elastic modulus (G'), plateau modulus (G), and zero shear complex viscosity (η). The cumulative MWD was found to be proportional to a plot of (G'/G)0.5 vs. measurement frequency (ω). Frequency (ω) was found to be inversely proportional to (MW)3.4, as expected. Results were scaled to absolute values using the empirical relationship η ∝ (M̄w)3.4, where M̄w is the weight‐average MW. M̄w, M̄n (number‐average MW) and M̄w/M̄n calculated from melt measurements were found to agree with size exclusion chromatography usually well within 10 percent for broad and bimodal distribution samples. M̄w/M̄n tended to be approximately 20 percent higher for narrow distribution samples (M̄w/M̄n < 1.2) because we did not account for a finite distribution of relaxation times from a collection of monodisperse polymer chains. We also did not account for the plasticizing effect of short chains mixed with long ones which caused peak positions to be closer together for Theological vs, size exclusive chromatography (SEC) determinations of MW for bimodal distribution blends.
The application of melt elasticity measurements to polymer processing
Authors: Maxwell Bryce
Published: December 2004

In recent years there has been increasing recognition of the importance of melt elasticity in polymer processing. A new instrument has been developed that determines the elastic properties of polymers in the melt state by measuring both the stress relaxation and strain recovery characteristics as a function of applied rate of strain, temperature, and magnitude of applied strain. Data on several different polymers will be presented together with examples of the significance of melt elasticity in such processing operations as thermoforming, blow molding, and film forming. A material parameter that is very important in the processing of polymers such as polystyrene and poly(methylmethacrylate) is the transition above the glass transition, Tg, referred to as the liquid‐liquid transition, TII. At this transition there is an abrupt change in the elasticity of the melt. Processing above or below this transition produces products with very different end use properties.
The determination of polymer interfacial tension by drop image processing: Comparison of theory and experiment for the pair, poly(dimethyl siloxane)/polybutndiene
Authors: Anastasiadis S. H. , Chen J. K. , Koberstein J. T. , Sohn J. E. , Emerson J. A.
Published: December 2004

The interfacial tensions of immiscible binary blends of poly(dimethyl siloxane) (PDMS) and polybutadiene (PBD) have been determined as a function of molecular weight and temperature. The technique employed for these measurements takes advantage of recent advances in the determination and analysis of pendant fluid drop profiles. The experimental data are compared to the predictions of square gradient theories and theories based on the diffusion equation approach as developed by Helfand and co‐workers. Qualitative agreement is obtained with both types of theory when the Flory‐Huggins interaction parameter is taken to be comprised of two terms: a temperature independent term of entropic origin; and an enthalpic term that is inversely dependent upon the temperature.
Formation and properties of thermosetting and high Tg polymeric materials
Authors: Gillham John K.
Published: December 2004

Interrelationships between reaction conditions and material properties of thermosetting and high Tg polymers are discussed from the point of view of a generalized time‐temperature‐transformation (TTT) diagram.
Synthesis and characterization of radiation curable polyurethanes containing pendant acrylate groups
Authors: Li C. , Nagarajan R. M. , Chiang C. C. , Cooper S. L.
Published: December 2004

A series of radiation sensitive and relatively high molecular weight poly(tetramethylene adipate) polyurethanes containing pendant acryfate functionality was synthesized. These radiation curable materials possess good mechanical properties and behave like common thermoplastic elastomers prior to chemical crosslinking which further enhances their strength and insolublizes them. Both the precursor and the cured materials were characterized by stress‐strain, differential scanning calorimetry. and dynamic mechanical testing. It was found that the poly‐(tetramethylene adipate) soft segments with molecular weight of 2000 or higher were crystallizable in the cross‐linked network. The soft segment molecular weight and the diisocyanate type were found to be important in determining the tensile and thermal properties of these male‐rials. The crosslinking process was found to depress crystallization of the soft segments and to improve tensile properties. Increasing the soft segment molecular weight resulted in an Increased elongation al break bill a decreased ultimate stress for both the precursor linear polymers and the crosslinked materials.
Nonlinear viscoelasticity and yield: Application of a coupling model
Authors: Rendell R. W. , Ngai K. L. , Fong G. R. , Yee A. F. , Bankert R. J.
Published: December 2004

An approach to nonlinear viscoelasticity is described which is based on the “coupling model” of relaxation. A brief review of nonlinear viscoelasticity models is given to put the present approach into historical perspective. The physical basis of the coupling model is then described, and the quantitative predictions that the model has made in linear viscoelasticity and other areas of relaxation are discussed. The relaxation function predicted by the coupling model is used as a time‐dependent kernal in a constitutive equation for a description of nonlinear viscoelasticity. The model incorporates the strain history dependence and allows for the evolution of material structure. Simulations are presented showing how the model reproduces the essential features of constant strain‐rate, strain‐rate change, and strain‐step experiments. Experiments are described that can partially characterize the coupling model parameters and lead to quantitative tests of the model.
A comparison of the crack tip damage zone for fracture of Hexcel F185 neat resin and T6T145/F185 composite
Authors: Chakachery E. A. , Bradley W. L.
Published: December 2004

Hexcel F185 neat resin and T6T145/F185 graphite fiber‐reinforced composite were subjected to Mode I loading in the compact tension (CT) geometry (fibers parallel to the crack) and the energy per unit area of crack extension, JIC, determined to be 8100 and 1600 J/m2 respectively. In‐situ fracture studies using scanning electron microscopy on a CT‐type specimen of F185 showed extensive microcracking in a damage zone ahead of the crack tip, which was similar to the microcracking observed in the whitened area ahead of the crack tip in the macroscopic CT specimens. A simple calculation using a rule of mixtures approach suggests that the diminished size of the damage zone and the presence of rigid fibers in the damage zone in the composite are not a sufficient explanation for the significantly lower delamination toughness of the composite compared to the neat resin. From this it may be inferred that the strain to failure locally in the damage zone ahead of the crack in the composite may also be lower than that which can be tolerated in the neat resin. Evidence for this idea comes from the observation that microcrack coalescence seems to occur preferentially at the fiber/resin interface.
Stress‐Cracking of high density polyethylene in detergents
Authors: Tonyali Koksal , Rogers Charles E. , Brown Hugh R.
Published: December 2004

Correlations of the stress intensity factor, KI, with crack speed, ċ, have been obtained in a number of detergent solutions each having different detergent concentration. A constant crack speed region was observed in high density polyethylene. The KI independent constant crack speed was found to vary linearly with detergent concentration. The viscosity of the detergent solution increases with concentration and hence this region is not controlled by the hydrodynamic properties of the environment in contrast with Williams' model. The KI‐ċ data were compared with existing models of crack propagation.
Effects of loading history on fatigue crack growth in high density polyethylene and toughened poly(methyl methacrylate)
Authors: Bucknall C. B. , Dumpleton P.
Published: December 2004

Fatigue crack growth measurements are made on two grades of high density polyethylene (HDPE), of density 940 and 958 kg/m3, and on one transparent grade of toughened poly(methyl methacrylate) (PMMA). In both grades of HDPE, prolonged cycling is necessary to initiate a crack from a razor notch. Relationships between crack growth and stress intensity factorKare studied in all three materials. The results show that Paris plots of log (da/dn) against log ΔKare linear provided that: (a) the loading pattern applied to the specimen remains constant; and (b) growth has taken place for a sufficient period to eliminate the effects of previous loading history. However,da/dnis strongly dependent upon the ratio of minimum to maximum stress and upon the stress amplitude during previous cycles. Overloads cause accelerated growth which is followed by crack arrest when the stress amplitude is restored to its original level. The use of a transparent polymer enables a more detailed study of crack growth phenomena to be made during fatigue testing.
On the nonlinear characterization of the long term behavior of polymeric materials
Authors: Brueller O. S.
Published: December 2004

In the linear viscoelastic range the long term behavior of viscoelastic materials—such as polymers—can be described by using exponential series with a limited number of terms for the approximation of the relaxation modulus or of the creep compliance. This procedure can be extended to the nonlinear viscoelastic range by multiplying the linear parameters of the material by certain nonlinearity factors, which depend upon the level of the applied loading. Application of this method to stress relaxation data of several polymers has shown that nonlinearity factors can be approximated as linear functions of the applied constant strain. From creep tests, on the other hand, one can observe that the immediate strain response to the suddenly applied stress is linear elastic even in the nonlinear viscoelastic range of the investigated polymer. The computation of the linear viscoelastic material parameters as well as of the nonlinearity factors is conducted numerically by using least squares techniques. Good agreement between computed results and experimental data can be observed in the presented examples.