bluuebunny/crossref_metadata_2025_split huggingface dataset:
The curing of a bisphenol A‐type epoxy resin with 1,8 diamino‐p‐menthane
Authors: Donnellan Thomas , Roylance David 
Published: December 2004

AbstractDifferential 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

AbstractPolymer 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

AbstractIn 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

AbstractFickian 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

AbstractThe 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

AbstractIn 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

AbstractThe 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

AbstractThe 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

AbstractGamma 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

AbstractThere 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

AbstractThe 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

AbstractDynamic 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

AbstractDielectric 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractA 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

AbstractThis 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

AbstractThe 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

AbstractA 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

AbstractThe 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

AbstractAll 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.