bluuebunny/crossref_metadata_2025_split huggingface dataset:
Internal friction in two longitudinal polymer liquid crystal esters
Authors: Brostow Witold , Samatowicz Danuta 
Published: December 2004

AbstractInternal friction (IF) was measured for two polymer liquid crystal (PLC) esters, PET/xPHB, where PET is poly(ethylene terephthalate), PHB is p‐hydroxybenzoic acid, with the mole fractions x of the PHB in the copolymers 0.5 and 0.6. Pure PET was also studied for comparison. The internal friction parameter Q−1 and the square of the output vibration frequency ƒ2 were determined as a function of temperature between −150°C and +400°C for a fixed input frequency. Values of the latter were varied between 0.5 and 30 Hz; all spectra were recorded under vacuum of 0.10 Torr. The IF results are virtually independent of the substrate used, namely silica glass or platinum. Multiple transitions found in each sample agree fairly well with those determined by other methods, including thermally stimulated depolarization. In contrast to other dynamic mechanical methods, a single internal friction vs. temperature run can be used to locate transitions in solid as well as in melt phases.
Modeling of the conveying of solid polymer in the feeding zone of intermeshing co‐rotating twin screw extruders
Authors: Carrot C. , Guillet J. , May J. F. , Puaux J. P. 
Published: December 2004

AbstractIn this paper, a model for the conveying of solid polymer in the feeding zone of intermeshing co‐rotating twin screw extruders is proposed. The theoretical model uses an approach that is similar to that commonly used in single screw extruders; however, it takes into account the particular geometry of the screw channel, the partially filled channel, and the special configuration of the two self‐wiping screws. The model thus considers two conveying mechanisms: the first one in the channel, which is analyzed in terms of polymer‐metal friction, and the second one, which is mainly an axial transport in the intermeshing zone. The theoretical predictions of the model are compared with the experimental results obtained on a laboratory extruder with a polymer in powder form, and satisfactory agreement is observed. The model enables the prediction of the evolution of the filling of the screws towards the geometry and the operating conditions. This is an important key to analyzing the thermal aspects in this zone, which can lead to a prediction of the melting capacity of the extruder. Indeed, the filling of the feeding zone defines the heat transport that occurs between the hot barrel and the solid polymer.
Modeling fountain flow and filling front shape in reaction injection molding
Authors: Perrett F. J. , Reible D. D. , McIlhenny R. C. 
Published: December 2004

AbstractA numerical model of the reaction injection molding process was developed to test front shape and flow approximations employed in previous models. The model was two‐dimensional and simulated the flow, reaction, and heat transfer in the typically long axial dimension and the typically small thickness dimension of a mold. The filling front shape and the velocity profiles in the filling fluid were determined by numerical solution of the momentum equation with the appropriate stress boundary conditions using the method of Patankar (1980). The predicted temperature and conversion results agreed with calculations assuming that the front was flat perpendicular to the flow and that a parabolic velocity profile existed behind the fountain flow region at the front. Thus, simple assumptions about front shape and velocity in the thin dimension of a reaction injection mold can be employed without significant loss of accuracy in modeling reaction injection molding.
Structure and properties of nylon 6 modified by γ‐irradiated linear low density polyethylene
Authors: Valenza A. , Spadaro G. , Calderaro E. , Acierno D. 
Published: December 2004

AbstractIn this work, structure and properties of blends of nylon 6 with 10% linear low density polyethylene γ‐irradiated in air at different integrated doses are presented. More particularly, Molau tests, DSC, SEM, and mechanical tests have been performed. Results show that positive morphological changes with respect to the blend with unirradiated linear low density polyethylene are well evident, especially in the blend with polyethylene irradiated at 50 KGy. This blend also shows an enhancement of the elongation at break and of the impact properties.
Fatigue behavior of medium‐density polyethylene pipes for gas distribution
Authors: Nishimura Hiroyuki , Nakashiba Akio , Nakakura Masahiro , Sasai Kunihiro 
Published: December 2004

AbstractThis paper illustrates the factors that control brittle failure under fatigue loading for test specimens cut from medium‐density polyethylene pipes for gas distribution. A square bar specimen cut from a pipe with a notch was made and a fatigue test was conducted to cause a brittle failure. To obtain the correlation among stress range, frequency, temperature, and cycles to failure in this fatigue test, Coffin‐Manson's frequency‐modified fatigue life equation was adopted and the material constants were determined. By gradually lowering the frequency, the resistance to creep can be estimated because cycles to failure—indicating the fatigue damage—decreased, and the actual loading time—indicating the creep damage—increased.
The role of the fibrillar structures in the compressive behavior of rigid‐rod polymeric fibers
Authors: Lee Charles Y.‐C. , Santhosh U. 
Published: December 2004

AbstractThe buckling of a fiber with a fibrillar microstructure is examined in light of all possible buckling modes. Parametric studies are done at variously assumed morphological levels, from a fibril down to a molecular chain, and it is shown that the buckling mode could, be different depending on the dimensional level of the individual buckling unit and the degree of interaction between the buckling elements. It is argued that fibrillar, instability is the principal reason for the low compressive strength of rigid‐rod polymeric fibers, and alternative approaches to improve the degree of interaction between the fibrils are considered.
Compatibilizing agents in polymer blends: Interfacial tension, phase morphology, and mechanical properties
Authors: Chen Cheng Chung , White James L. 
Published: December 2004

AbstractThe interfacial tension, phase morphology, and phase growth was determined for four polymer blend systems: polyethylene/polystyrene, polyethylene/polyamide‐6, polystyrene/polyamide‐6, and polystyrene/poly(ethylene terephthalate). Generally, high interfacial tension correlates with coarse phase morphology and rapid phase coalescence. The addition of various potential compatibilizing agents to these binary blend systems results in lowered interfacial tension, finer and stabilized phase morphologies. The characteristics of different compatibilizing agents were compared for several of the blend systems. We also look at the influences of compatibilizing agents on mechanical properties of the blend systems. Some compatibilizing agents are able to produce substantial improvements in ultimate properties.
Rheological behavior of a semirigid liquid crystal polymer
Authors: La Mantia F. P. , Valenza A. , Paci M. , Magagnini P. L. , Pedretti U. , Roggero A. 
Published: December 2004

AbstractThe rheological behavior of liquid crystal polymers is still far from completely clarified from both experimental and theoretical points of view. In this paper, the shear flow and the non‐isothermal elongation flow behavior of a semirigid liquid crystal copolyester is discussed. The viscosity strongly decreases when the test temperature is increased above the crystal‐nematic transition temperature; below this temperature the viscosity is very high. The thermal history strongly affects the shear viscosity. The elongational flow behavior depends also on temperature. Above the crystal‐nematic transition temperature and the mesophase is easily spinnable, whereas below this temperature, the spinnability is very poor.
The dielectric behavior of glassy amorphous polymers at 2.45 GHz
Authors: Chen M. , Siochi E. J. , Ward T. C. , McGrath J. E. 
Published: December 2004

AbstractThe dielectric behavior of glassy thermoplastic polymer in the microwave frequency range was investigated. Specifically, the relationship between energy absorption and temperature for several thermoplastic systems was examined to test the theoretical basis for heating under microwave irradiation. Irradiation under traveling and standing wave conditions were explored. The heating rate versus temperature data at a frequency of 2.45 GHz yielded a microwave calorimetry procedure for examination of the dielectric and relaxation behaviors. Correlations were drawn between (a) the apparent activation energy and the critical temperature, and (b) the shape of the dielectric spectra at 2.45 GHz and its shape in the kHz region. WLF relationships were examined for glassy thermoplastics to show the difference in changing activation energy with temperature.
Viscoelastic properties of a styrene‐isoprene‐styrene triblock copolymer and its blends with polyisoprene homopolymer and styrene‐isoprene diblock copolymer
Authors: Berglund Charles A. , McKay Kevin W. 
Published: December 2004

AbstractThe effects of added polyisoprene homopolymer (PI) and polyisoprene‐blockstyrene diblock copolymer (SI) on the viscoelastic properties of a polystyrene‐block‐polyisoprene‐block‐polystyrene triblock copolymer (SIS) having a spherical domain morphology have been examined. The former two species are used to model the effects of imperfections in structures that result from triblock copolymers missing, respectively, two or one polystyrene end blocks. The results indicate that the loss modulus and tangent delta in the plateau region can be dominated by imperfections in the copolymer structure. The interpretation of viscoelastic data in the rubbery plateau region as an indication of interface structure in block copolymers is therefore greatly complicated. Small angle X‐ray scattering (SAXS) and rheological tests were also used to determine the order‐disorder transition temperature for an SIS triblock copolymer and its blend with an SI diblock. The SAXS data are consistent with Han's rheological criteria for determining the order‐disorder transition temperature. However, the complex viscosity does exhibit Newtonian behavior for low rates at the highest temperatures, even though the domain morphology persists. Stress relaxation and dynamic modulus data at high temperatures clearly show a secondary “rubbery” plateau at long times, and we offer a qualitative explanation for this feature based on a proposed relaxation mechanism.
Process of unsaturated polyester resin synthesis on a laboratory and industrial scale
Authors: Korbar J. , Golob J. , Šebenik A. 
Published: December 2004

AbstractA study of the progress of the synthesis of unsaturated polyesters, based on anhydrides of phthalic and maleic acid and propylene glycol without added catalysts was done. The reaction was carried out on a laboratory and industrial scale. The acid number and molecular weight distribution were determined. In the laboratory synthesis the, amount of water produced during the reaction was also measured. Two steps in the reactions were observed. The first is the reaction of anhydrides with glycol producing monoester which is followed by step‐growth polymerization reaction producing polymer. The kinetics of step‐growth polymerization reaction was found to be third order with an activation energy of Ea = 54.3 kJ mol−1 and ko = 15.2 kg2mol−2s−1. The kinetic model was prepared and compared with results obtained from reactions carried out on an industrial scale. A method is presented for determining a heating program based on a limited reaction rate and a maximal reaction temperature for a particular system. The MWD of polyester resin was determined and disagreement was found compared to the “most probable” MWD.
Boundary element study on particle orientation caused by the fountain flow in injection molding
Authors: Jin Xiaoshi 
Published: December 2004

AbstractA boundary element model is used for simulating the fountain flow in injection molding. The particle orientation caused by the fountain effect is illustrated with a tracer‐in‐domain technique which is similar to the Marker‐And‐Cell technique. The efficiency and accuracy of the boundary element model are shown through this simulation, in determination of the free surface shape, and the particle orientation patterns. Clear and correct information is obtained to interpret the complicated effects upon formation of the orientation, especially regarding the “V” shape pattern in the skin areas. The simulation is in agreement with both Schmidt's experiment and some finite element analysis.
Design and processing optimization of extruder screws
Authors: Potente H. , Hanhart W. , Reski T. 
Published: December 2004

AbstractOnly recently has increasing use been made of computer simulation in the field of extruder engineering. This simulation is based on physico‐mathematical process models. In order to achieve a closed, process engineering‐based extruder layout and operating behavior simulation it is necessary to have models describing the throughput behavior, the melting process, the temperature development, the pressure profile over the screw length, the residence time distribution, the mixing and dispersion processes, and also the torque and power requirements. In the Plastics Technology Section of the University of Paderborn (KTP) a program for the computer‐aided design of extruders (REX), financed by 17 companies, was developed which will permit rapid application of the models developed there and will fulfill the requirements set out above. Since no computation‐intensive numerical methods like Finite Element or Finite Difference Methods (FEM, FDM) are required, the algorithms are very rapid, which means that short computing times are achieved (just a few seconds on an IBM AT).
Crosslinking in halogen containing novolac electron beam negative resists
Authors: Lampe I. V. , Reinhardt M. 
Published: December 2004

AbstractHalogenophenol novolac (HPN)‐based negative resists exhibit excellent sensitivity and pattern resolution properties. The HPNs act as synergists for crosslinking with other irradiation labile compounds such as naphthoquinone diazide and bisazide vs. hydrogen halide (HX) elimination reaction, resulting in additional crosslinking, probably by aryl radical recombination and/or addition. We describe a new resist formulation based on HPN binder and melamine crosslinker (Cymel 303). In this case the irradiation induced HX elimination additionally catalyzes the melamine crosslinking.
Rheology of thermoplastic starch: Effects of temperature, moisture content, and additives on melt viscosity
Authors: Willett J. L. , Jasberg B. K. , Swanson C. L. 
Published: December 2004

AbstractThe melt viscosity of thermoplastic starch has been investigated as a function of temperature, moisture content, and processing conditions. The effects of various low molecular weight additives have also been studied. Starch melts exhibit power law behavior over the range of shear rates studied. Melt viscosity decreased with increasing temperature and moisture content (MC). The power law index m increased with increasing temperature. The consistency K decreased with increasing temperature and increasing moisture content. Moisture content during the pelletizing step influenced melt viscosities measured after equilibration to different MCs. All additives studied except glycerol monostearate (GMS) significantly lowered the melt viscosity of starch, some more effectively than water relative to starch with 15% MC. Starch with GMS had viscosities essentially the same as, or slightly higher than, starch/water. This behavior may be due to the presence of unmelted helical inclusion complexes of starch and GMS. Starch formulations at 160°C exhibited melt visocosities similar to an LDPE of melt index 1.8.
On the phenomenology of yield in bisphenol‐a polycarbonate
Authors: Stokes Vijay K. , Bushko Wit C. 
Published: December 2004

AbstractThe phenomenology of yield in bisphenol‐A polycarbonate is explored through tensile tests on thin rectangular specimens and through pressure‐induced bulging of thin, clamped circular disks. In a tensile test, while the nominal critical stress at which yield initiates and the nominal draw stress at which a stable neck propagates along a specimen depend on the temperature and the strain rate, the ratio of the draw stress to the critical stress is shown to be approximately 0.75 over a temperature range of 22 to 65°C and strain‐rates in the range of 10−4 to 100 s−1. Specimens subjected to constant tensile loads between the draw and critical stresses are shown first to creep till stretches on the order of 1.06 are attained and then are shown to undergo stable necking. Tensile tests on thin, wide rectangular specimens show that yielding initiates through shear bands that broaden and intersect to generate necks, which subsequently propagate along the specimen. In pressure‐induced bulging of clamped disks, biaxial stretching progresses monotonically under increasing pressures; strain localization does occur near the outer edges of the specimens, however. Heating of a specimen with a substantial stably necked region shows that the temperature‐induced recovery of the specimen from its deformed state begins well below the transition temperature Tg of the material, although most of the recovery occurs at Tg.
Extrusion die design for multiple stripes
Authors: Wen Shu‐Heng , Liu Ta‐Jo 
Published: December 2004

AbstractTwo numerical approaches have been applied to examine the possibility of adding shims to conventional extrusion dies such as T‐dies and coat‐hanger dies to produce multiple stripes. The first numerical approach is based on a one or two‐dimensional lubrication approximation and the second one is the three‐dimensional finite element simulation. Both approaches are applicable, but the lubrication approximation is accurate and much simpler to use. The extruded stripes are assumed to obey a non‐Newtonian power‐law model. It has been found that the T‐die with a shim can produce multiple stripes of acceptable uniformity, irrespective of the strip numbers and widths and the power‐law index. The coat‐hanger die with a shim did not deliver multiple stripes with good uniformity. Adding an outer manifold to the coat‐hanger die can serve as an effective means to reduce flow nonuniformities.
A cure study on alumina trihydrate reinforced allylester resins by differential scanning calorimetry
Authors: Jang Jyongsik , Yi Jieun 
Published: December 2004

AbstractAllylester prepolymers were synthesized by transesterification, and curing kinetics of alumina tihydrate reinforced allylester resins was studied by means of a differential scanning calorimetry dynamic experiment. The activation energies and the frequency factors of the reinforced allylester prepolymers were estimated by means of Ozawa's and Kissinger's methods. The values determined from the Ozawa method are higher than those from the Kissinger method. The peak exotherm temperature of reinforced allylester resin was shifted to a lower temperature as the concentration of curing agent increased. The peak exotherm temperature as the concentration of curing agent increased. The peak exotherm temperature of reinforced allylester resin was, however, shifted to a higher temperature as the content of alumina trihydrate increased. In the case of the dynamic experiment, both the activation energy and the frequency factor decreased as the concentration of curing agent was increased. Meanwhile, there exist minimum values of both the activation energy and th frequency factor with varying contents of alumina trihydrate.
Rheological study on poly‐D(‐)(3‐hydroxybutyrate) and its blends with poly(ethylene oxide)
Authors: Choi H. J. , Park S. H. , Yoon J. S. , Lee H‐S. , Choi S. J. 
Published: December 2004

AbstractAspects of thermal, morphological, and rheological properties of biodegradable poly‐D(‐)(3‐hydeoxybutyrate) (PHB) blended with poly(ethylene oxide) (PEO) have been studied. Thermal properties and morphology of the blends were examined by scanning electron microscopy and differential scanning calorimetry, respectively. A rotational theometer with parallel plate geometry was also adopted to investigate the rheological properties of these blends. In addition, dynamic ciscoelasticity was measured by a Rheovibron as functions of time and temperature. From these measurements, PHB and PEO were observed to be miscible in the melt state. In the case of the blend systen 80/20 PHB/PEO by weight, the vacant domains of the PHB were filled with PEO particles, and this morphological state enhanced the rheological properties. Furthermore, PHB and its blends were found to have high crystallinities, but to have unstable thermal behavior about Tm.
Low shear viscosity and crystallization in dilute solutions of polymers at high pressures: Falling body viscometry of high molecular weight polyethylene solutions
Authors: Akki Rashi , Bair Scott , Abhiraman A. S. 
Published: December 2004

AbstractA specially designed falling body viscometer has been used to obtain low shear viscosities of dilute solutions of high molecular weight polyethylene in decalin and for detecting phase transitions at high pressures. The method provides valuable rheological data at pressures that correspond to those I lubrication and some extrusion processes. In addition, the method enables detection of phase transitions, such as crystallization, that result in detectable changes in rheology. The influence of pressure as high as 0.6 GPa ( ∼ 80.000 psi) is illustrated here through a study of crystallization, with verification from light scattering and calorimetry.
Modeling the mechanical properties in polypropylene/polyamide‐6 blends with core shell morphology
Authors: Rösch Jocachim 
Published: December 2004

AbstractPolypropylene/Polyamide‐6 (PP.PA) blends containing maleic anhydride grafted elastomers were prepared by reactive blending. Three different types of core shell morphologies were obtained and characterized by transmission electron microscopy (TEM). The midulus of these elastomer midified PP/PA (70/30) blends with core shell type morphology is compared to predictions derived from the Kerner model. The multiphase morphology of these blends could be modeled by sequential application of the Kerner equation to two‐phase subinclusions. Using morphological data ontained by TEM, good agreement between experimental and calculated values was ontained. The results are used to tailor PP/Pa‐6 blends combining stiffness and toughness.
The Quantity/Distance Category of Gun and Rocket Propellants
Authors: Bascombe K. N. , Wyatt R. M. H. 
Published: December 2004

AbstractThe quantity/distance categorisation of explosive materials is discussed. The procedure for the standard UK laboratory‐type test (large sealed vessel test) is described. The borderline, in terms of the test, between fire and explosive risks has been established by testing materials for which the nature of the hazard is previously known. Trials have established that boxed UK plastic (composite) propellants are fire risks only.
The Influence of Additives on Pressure and Momentum of the Air Shock from detonating charges
Authors: Licht H. H. , Froböse M. 
Published: December 2004

AbstractThe air blast effect produced by high explosives with additives of various types and quantities was studied. To this end, air shock intensities and pressure profiles were recorded at certain distances from an unconfined charge. Among those additives which by their reaction with the gaseous products of the detonated explosive theoretically should increase the energy potential, aluminum and zirconium exhibit a positive effect while other substances such as boron react too slowly for strengthening the blast effect. An addition of aluminum (32 weight%) causes the shock wave pressure to increase by about 15% and the momentum by 30% as compared with the pure explosive.