bluuebunny/crossref_metadata_2025_split huggingface dataset:
Highly elastic‐constant vicosity fluids
Authors: Choplin L. , Carreau P. J. , Kadi A. Ait 
Published: December 2004

AbstractThe rheological properties of three types of fluids that exhibit large normal stresses are examined and compared. These fluids have a constant or nearly constant viscosity and can be used as model viscoelastic fluids, covering a range of viscosity from 0.1 to 124 Pa.s. One lubricant, Emkarox FC 31‐45000, is shown to have the characteristics of a second‐order fluid. Series difficulties encountered in measuring the rheological properties of the Separan—corn syrup solutions (Boger fluids) are reported. The Emkarox and solutions of polyacrylamide (Pusher 700) in mixtures of glycerine and water are proposed as better model fluids.
Effect of the addition of EPM copolymers on the properties of high density polyethylene/isotactic polypropylene blends: II. Morphology and mechanical properties of extruded samples
Authors: D'Orazio L. , Greco R. , Martuscelli E. , Ragosta G. 
Published: December 2004

AbstractThe influence of the addition of two ethylene‐propylene random copolymers (EPM) with different composition on the mechanical properties, thermal behavior and overall morphology of high density polyethylene (HDPE)/isotactic polypropylene (iPP) blends, was investigated on extruded samples. The experimental data showed that the morphology of binary HDPE/iPP blends is drastically modified by these additives and that the ultimate mechanical properties of these mixtures are greatly improved. A reasonable explanation of these results can be ascribed to the fact that these copolymers can act as “compatibilizing agents” in the amorphous regions of the two semicrystalline homopolymers. The extent of such effects is dependent on the chemical structure and/or on the molecular mass of the added copolymer as well as on the HDPE/iPP blend compositions.
Characterization of electron beam crosslinked poly(styrene‐block‐ethylene‐co‐butylene‐block‐styrene)
Authors: Zurawski D. E. , Sperling L. H. 
Published: December 2004

AbstractA saturated triblock copolymer, poly(styrene‐block‐ethylene‐co‐butylene‐block‐styrene) was chemically crosslinked using trimethylol propane trimethacrylate, TMPTM, and subjected to electron beam radiation. The gel percent, Gehman ten second modulus, and stress relaxation were measured to characterize the materials as a function of crosslinker concentration and radiation level. A time‐temperature super‐position master curve was generated at 63°C for 3 percent TMPTM and 5 Mrads of radiation, which indicated rubbery plateau behavior at long times of measurement, as opposed to the uncrosslinked material, which continued to creep and flow. The main locus of crosslinking was within the polystyrene phase, which explains reduced creep and stress relaxation only for long times of measurement and/or high temperatures. Based on shifts of the glass transition temperatures, it was estimated that 11 to 16 percent poly(ethylene‐co‐butylene) was dissolved in the polystyrene phase.
The stability of blends of incompatible thermoplastics
Authors: Maxwell Bryce , Jasso Guillermo L. 
Published: December 2004

AbstractConventional thermodynamic reasoning would predict that it would be very difficult to melt blend incompatible polymers and that if such blends were made they would be highly unstable and would phase separate upon heating. A method has been developed to melt blend incompatible polymers (such as poly(methylmethacrylate) and polyethylene) to form two continuous interpenetrating phases and that upon prolonged heating the stability of the structure is increased rather than decreased.
Mechanical properties of injection molded blends of poly(ethylene‐terephthalate) and poly(amide‐6,6)
Authors: Kamal M. R. , Sahto M. A. , Utracki L. A. 
Published: December 2004

AbstractData have been obtained regarding the tensile and impact behavior of pure poly(ethylene terephthalate) (PET) and polyamide 6,6 (PA) and blends of PA in PET in concentrations of 5, 10, 25, 30 and 35 percent by weight of PA. The measurements were carried out at −40, 23 and 70°C. Dispersion and sample preparation were carried out in a reciprocating screw injection‐molding machine. All blends exhibited brittle behavior and low strength, when compared to pure components. Although some enhancement of mechanical properties might be realized by orientation, it is suggested that the observed behavior might be attributed to the low quality of dispersion achievable in injection molding process. This conclusion is supported by microscopic evidence.
Hydrogen bonding in polymer systems
Authors: Cangelosi F. , Shaw M. T. 
Published: December 2004

AbstractThe importance of hydrogen bonding interactions in promoting polymer miscibility has been the subject of much recent investigation. In this study, we address the question of the effect of molecular size and geometry on the intensity of the hydrogen bonding interaction. To this end, the interaction of the functional group in various molecules with a variety of acid and base polymer matrices has been monitored using infrared spectroscopy. The “probes” used in this study each contained only one functional group per molecule to prevent intra‐molecular association. The probes were acetone, di‐n‐hexyl ketone, 10‐nonadecanone, cyclohexanone, cyclododecanone, isopropanol, 4‐decanol, 10‐nonadecanol, cyclohexanol, and cyclododecanol. The interactions of the base probes with poly‐(vinyl chloride), poly(vinylidine fluoride), phenoxy, poly(styrene‐co‐allyl alcohol), and a variety of cellulosic polymers were studied. Acid probe interactions were measured in poly(pivalolactone), poly(butanediol‐1,4‐terephthalate), poly‐(acetal), poly(ϵ‐caprolactone), poly(vinyl methyl ether), poly(4‐methoxy styrene) and poly(ethylene oxide). The effect of the presumably inert poly(styrene) and ethylene‐propylene rubber matrices on the probe's functional group was studied for comparison.
A comparison of miscible binary blend interaction parameters measured by different methods
Authors: Harris J. E. , Paul D. R. , Barlow J. W. 
Published: December 2004

AbstractMiscible blends of the polyhydroxy ether of bisphenol‐A, Phenoxy, with a series of aliphatic polyesters were studied using melting point depression analysis and sorption to obtain the Flory‐Huggins polymer‐polymer interaction parameter, B. The B values obtained from these measurements were found to agree well in sign, magnitude, and variation with ester repeat structure and to also agree well with B values measured calorimetrically for mixtures of low molecular weight compounds with structures which are analogous to those of the polymers. These comparisons suggest that the same mechanisms are responsible for the exothermic heats of mixing measured directly for the analog compounds and indirectly for the miscible polymer blends. For this general system, evidence is provided which suggests that hydrogen bond formation between the hydroxyl group on Phenoxy and the ester moiety is probably responsible for the exothermic interactions and polymer blend miscibility observed.
Review on processing ultra high tenacity fibers from flexible polymer
Authors: Ohta T. 
Published: December 2004

AbstractThe various efforts up to date on the processing of ultra high tenacity fibers from flexible polymer have been summarized in this report. Some significant parameters correlating well with ultra high tenacity have been found through consideration of experimental results of polyethylene, despite the wide diversity in the processing techniques, degrees of drawing, thermal conditions, and molecular weight characteristics. It has been concluded from those parameters that ultra high tenacity fibers can be only attained by processing techniques satisfying the following structural principles simultaneously:ultra drawing with draw ratio above 20 for increasing the number of tie molecules and the degree of molecular orientation.reduction of the small angle x‐ray scattering intensity, correlating to an increase in the number of tie molecules.increase in molecular chain length for reducing the intermolecular chain slip at polymer chain ends.increase the slope of the Griffith plot, a manifestation of reducing defeets and flaws in microfibrils.
Post‐curing of dental restorative resin
Authors: Wu W. , Fanconi B. M. 
Published: December 2004

AbstractThe post‐curing of a bisphenol A‐glycidyl‐methacrylate based copolymer system at 37°C and 100 percent relative humidity was monitored using Fourier Transform IR (FT‐IR). The dependence of degree of post‐curing on the monomer and initiator components was investigated. The further polymerization achieved by elevating the temperature was measured using differential scanning calorimetry (DSC). The results clearly demonstrated that this free radical curing process was severely quenched by vitrification. Furthermore, a rapid loss in the reactivity to further curing was observed for the material in the quenched state, and this loss in reactivity was attributed to the decay of free radicals.
Properties of phenolic fiber‐reinforced polymers
Authors: Broutman L. J. 
Published: December 2004

AbstractFibers made of phenol formaldehyde are relatively new to the market place and are currently manufactured in Japan. They have certain characteristics which make them attractive as a reinforcement for rubber, thermoplastics, and thermosets. This paper will discuss the properties of molded polypropylene thermoplastics as a function of fiber weight percent and surface treatment. It is shown that the elevated temperature properties are improved without sacrifice of low‐temperature brittleness.
Injection molding of thermotropic liquid crystal polymers
Authors: Ophir Zohar , Ide Yoshiaki 
Published: December 2004

AbstractThermotropic liquid crystal polymers consist of rod‐like molecules and are often called “self reinforcing thermoplastics.” Their rheological behaviors as well as orientation development during processing are often very similar to those of short fiber‐filled composites. Without reinforcement, the polymer shows superior mechanical properties to conventional glass fiber‐reinforced engineering resins. The orientation distribution in the crosssection as well as flow patterns in the molded thermotropic polymers are clearly visible to the naked eye due to color differences. This makes it particularly convenient to study the orientation distribution as well as the flow patterns of packing, back flow, jetting, flow instabilities, and weld line formation in injection molding. This paper discusses physical properties of a typical ther motropic polymer and their relationship to mold filling process in the injection molding.
The rheology and spin coating of polyimide solutions
Authors: Jenekhe Samson A. 
Published: December 2004

AbstractThe rheological properties of five types of concentrated polyamic acid and polyimide solutions are characterized by non‐Newtonian shear viscosity η(\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \dot \gamma} $\end{document}) and primary normal stress coefficient Ψ1(\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \dot \gamma} $\end{document}) measurements over a wide range of shear rates. Onset of non‐Newtonian flow of the polyamic acid solutions was observed in the shear rate range 30 to 400s−1 and of the fully imidized polyimide solution at below 3 × 10−2s−1. Significant viscoelastic properties exemplified by normal stresses were observed in all the solutions. The solution rheology results are discussed in the context of spin coating for the deposition of thin films. The relative magnitude of effects of non‐Newtonian flow on the dynamics of spin coating is assessed with a Deborah number characteristic of the flow.
Viscoelastic behavior of amorphous polymers in the glass‐rubber transition region: Birefringence studies
Authors: Read B. E. 
Published: December 2004

AbstractViscoelastic processes associated with the glass‐rubber transition of an amorphous polymer are considered to involve hindered rotations around main‐chain bonds, which give rise to a decrease in molecular distortion in the stressed material and to an orientation or disorientation of chain segments. The local distortional changes are associated with variations in energy‐elastic stress. The orientational rearrangements yield changes in conformational entropy and energy and may be described in the long‐time region by the normal mode motions of Gaussian submolecules. Assuming that the net time‐dependent stress and birefringence may each be expressed as the sum of distortional and orientational contributions, methods are proposed on the basis of stress‐optical data for resolving the distortional and orientational stresses or moduli during stress‐relaxation, creep, and dynamic mechanical tests. An analysis of dynamic birefringence data for different amorphous polymers indicates that the orientational processes become important in the long relaxation‐time region and are consistent with predictions of the submolecular theory. The distortional changes dominate the shorter relaxation‐time behavior and are characterized by somewhat narrower distributions of relaxation times than are apparent from the unresolved data.
Block polymers. Characterization and use in polymer blends
Authors: Bywater S. 
Published: December 2004

AbstractPolymer blends, because of the well‐known immiscibility of polymers, generally show phase separation. Block polymers can be considered as simple models of two‐phase systems. Because unlike segments are connected by covalent bonds, the phase separation is on a smaller scale and takes rather unusual forms. The types of block polymers of commercial importance are described with a consideration of the morphologies which result from particular compositions. Their use as solubilizing agents to increase the compatibility of the corresponding homopolymers is also discussed.
Some observations on kinetic and steric limitations to specific interactions in miscible polymer blends
Authors: Garton Andrew 
Published: December 2004

AbstractThis note describes the application of infrared spectroscopy to determine the proportion of ester groups of poly(ϵ‐caprolac‐tone) which are involved in specific interactions with the hydroxyl groups of the poly(2‐hydroxypropyl ether of bisphenol A) (Phenoxy, Union Carbide) in a series of miscible blends of the two polymers, Even with a fifteen‐fold excess of hydroxyl groups, only about 50 percent of the ester groups of poly(ϵ‐caprolactone) are hydrogen‐bonded, presumably reflecting steric restrictions to the ester‐hydroxyl interactions. Partially miscible blends of these two polymers may also be prepared by a suitable choice of casting solvent, and infrared spectroscopy may then be used to follow the kinetics of miscibility when the partially miscible blend is heated.
The composition‐dependent glass transition: Relations between temperature pressure, and composition
Authors: Couchman P. R. 
Published: December 2004

AbstractA new predictive relation between pressure and temperature changes on the glass‐transition boundary is derived for random solutions. The isobaric version of this relation is integrated to recover a previous theory for the compositional variation of glass‐transition temperatures. The isothermal form of the differential equation gives an equation for the compositional variation of glass‐transition pressures. An enthalpic definition of the transition boundary provides a relation between excess enthalpies of mixing for the glassy and liquid states for the isobaric and isothermal transitions. Similarly, a definition of the boundary in terms of the solution volume provides a relation between excess volumes of mixing for these two states for the isobaric and isothermal transitions. The primary entropic equation for the composition‐dependent isobaric transition gives two hierarchies of approximation, one of which is shown to be preferred for physical reasons. A parallel situation arises for the isothermal transition.
Dielectric properties of poly(α‐methyl α‐n‐propyl‐β‐propiolactone)/poly(vinyl chloride) blends
Authors: Malik Tariq M. , Prud'Homme Robert E. 
Published: December 2004

AbstractThe dielectric properties of miscible blends of poly(vinyl chloride) (PVC) and poly(α‐methyl‐α‐n‐propy‐β‐propiolae‐tone) (PMPPL) have been investigated at different temperatures above and below Tg. The results were analyzed using the Cole‐Cole representation and lead to the conclusion that this mixture does not exhibit micro‐scale heterogeneities. Dielectric constant and dielectric loss master curves were constructed using the stress relaxation shift factors determined previously; the same shift factors could be used for the homopolymers and their blends. Similarities between the dielectric master curves and the stress relaxation master curves of PVC, PMPPL, and their blends, are also discussed.
The properties of mica‐filled polypropylenes
Authors: Busigin C. , Lahtinen R. , Martinez G. M. , Thomas G. , Woodhams R. T. 
Published: December 2004

AbstractWater‐ground Phlogopite micas were classified into narrow particle‐size distributions containing flakes with well‐defined diameters and thicknesses in order to evaluate the influence of particle size and flake aspect ratio on the mechanical properties of mica‐filled polypropylenes, For the purposes of comparison, most of the injection‐molded specimens contained 40 percent (by weight) mica. As expected, the flexural and tensile modulus values increased in proportion to the aspect ratio over the range from 30 to 60 to a maximum of 8 GPa. The measured tensile strengths of the mica‐filled polypropylenes increased substantially as the flake diameter became smaller, but did not correlate with the flake aspect ratio. The attainable properties were frequently dependent upon the method of mixing, and considerable care was necessary to ensure proper dispersion and adequate coupling. Intensive mixing, as in a Gelimat Mixer, may cause in situ delamination and particle‐size reduction of the mica filler particles, leading to a marked increase in tensile strength of the resulting composite. The mica‐filled compounds could be reprocessed many times without significant loss of properties, particularly compounds having mica particles less than 40 μm in diameter. The fracture energies (notched Izod) and the heat‐distortion temperatures were not appreciably influenced by the size or aspect ratios of the mica within this range. Increased fracture toughness could be achieved by reducing the mica concentration or employing a polypropylene copolymer. Guidelines are presented to indicate the preferred characteristics of mica fillers and the influence of mixing conditions on performance.
Optimization of the transesterification stage of polyethylene terephthalate reactors
Authors: Kumar Anil , Sukthankar V. K. , Vaz C. P. , Gupta Santosh K. 
Published: December 2004

AbstractThe tranesterification step of the polyethylene terephthalate (PET) formation consists of several side reactions in addition to the main ester interchange, transesterification, and polycondensation reactions. The side reactions considered in this work are acid end group, acetaldehyde, diethylene glycol, water, and vinyl end group formations. The objective function of the batch esterinterchange reactor is assumed to consist of maximizing the conversion and simultaneously minimizing the formation of side products. The control vector iteration procedure has been used to optimize the esterinterchange reactor and the temperature‐time profile that gives the best performance has been found. It is found that the reactor should be operated at a high temperature initially to obtain high conversion of dimethyl terephthalate (DMT) first, but then it should be lowered to reduce the formation of side products.
Solution of final stages of polyethylene terephthalate reactors using orthogonal collocation technique
Authors: Kumar Anil , Gupta Sushil K. , Madan Sanjiv , Shah Nirmal G. , Gupta Santosh K. 
Published: December 2004

AbstractThe formation of polyethylene terephthalate (PET) has been modeled to have reactions with monofunctional compounds, redistribution, and cyclization reactions in addition to the usual polycondensation step. In the final stages, the overall polymerization is mass‐transfer controlled and solution of the reactor performance equations have been determined through the orthogonal collocation technique. This technique is found to be considerably more efficient for PET reactors compared to the finite difference method; the use of ten collocation points gives results which are close to the exact solution.
The effect of a temperature gradient on residual stresses and distortion in injection moldings
Authors: Thompson M. , White J. R. 
Published: December 2004

AbstractDistortion of bars injection‐molded from polystyrene, polypropylene, and glass‐fiber‐filled polypropylene and subsequently placed in a temperature gradient has been examined. Residual stress distributions have been measured both for the as‐molded state and after annealing in a temperature gradient. In the as‐molded state all moldings showed the usual residual stress distribution with compressive stresses near the surface and tensile stresses in the interior. In all three materials it was found that tensile stresses could be developed near to the warmer surface on gradient annealing and that tensile stresses still remained at this surface when the bar was cooled and permitted to bend to restore internal equilibrium. It is shown therefore that in addition to the dimensional changes which occur and which may render the molding unserviceable after temperature gradient annealing, another undesirable change takes place, leaving the molding much more susceptible to fracture from a surface flaw. Uniform annealing is found to be much less likely to cause stress reversal and the stresses remain balanced so that distortion is minimal.
Necking behavior of low‐density polyethylene‐isotactic polypropylene blends: A morphological investigation
Authors: Rizzo Giovanni , Spadaro Giuseppe 
Published: December 2004

AbstractThe tensile behavior of low‐density polyethylene‐isotactic polypropylene blends was investigated at room temperature. Neck formation and propagation along the whole length of the samples were observed for the whole range of composition. This behavior, which is not indicated by most data available in the literature, was examined in relation to sample morphology by scanning electron microscopy. The results of this investigation indicated some differences between the morphology of these materials and the morphology of blends which do not undergo necking propagation.