bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rheology and processing of linear low density polyethylene resins as affected by alpha‐olefin comonomers
Authors: Kalyon Dilhan M. , Yu Dong‐Woo , Moy Francis H. 
Published: December 2004

AbstractThe effects of the higher alpha‐olefin comonomers on the rheology and processing behavior of linear low density polyethylenes were investigated. Four linear low density polyethylene resins polymerized with butene, hexene and octene comonomers and a low density polyethylene were characterized in terms of their shear viscosity, first normal stress difference, storage and loss moduli, shear stress growth, stress relaxation upon step strain, stress relaxation upon the cessation of steady shear, and uniaxial extensional stress growth material functions. Differences in first normal stress difference, relaxation moduli, damping function parameters, and uniaxial extensional stress growth behavior were noted. The observations were elucidated in terms of the processability considerations in blown film extrusion process.
Ultimate properties of blown films of linear low density polyethylene resins as affected by alpha‐olefin comonomers
Authors: Kalyon Dilhan M. , Moy Francis H. 
Published: December 2004

AbstractBlown film samples of linear low density polyethylene resins copolymerized with butene, hexene, and octene were characterized in terms of various mechanical and optical properties which included tensile, impact, tear, puncture, haze, and gloss. The microstructure development aspects were also investigated employing crystallinity and density, infrared dichroic ratio, and birefringence, and focusing on various positions along the circumference of the bubble. The ultimate properties, and the microstructure of the blown film samples, were found to depend strongly on the extent of short chain branching and on the comonomer employed.
Temperature measurements of polymer melts in the heating barrel during injection molding. Part I. Temperature distribution along the screw axis in the reservoir
Authors: Amano Osamu , Utsugi Shirou 
Published: December 2004

AbstractA new procedure has been developed to measure the temperature distribution of the polymer melts along the screw axis during injection by using a small sheath thermocouple. At the same time, the effects of molding conditions on temperature distribution has been studied. The temperature distribution of the polymer melt along the screw axis during injection can be obtained from the difference between the standard temperature profile and the temperature profile of the polymer melt with unknown and non‐uniform temperature measured under the same rate of injection. The temperature of a polymer melt within a shot is not uniform. The difference between the maximum and the minimum temperature within a shot may exceed 10°C in some cases. There are two major factors which govern the effects of molding conditions on the temperature distribution of the polymer melts during injection. The first is the amount of shear heating in the metering zone. The second is the amount of heat absorbed into the polymer in the compression and feed zones.
Modeling the packing stage in injection molding of thermoplastics
Authors: Huilier D. , Lenfant C. , Terrisse J. , Deterre R. 
Published: December 2004

AbstractA model, for the packing stage In injection molding of thermoplastics is proposed. It allows one to calculate the time evolution of pressure and temperature fields and mass variations in simple geometries. The model holds for amorphous as well as for crystalline polymers if the kinetics of crystallization are known for temperatures far from the melting point, It applies after filling stage; initial temperature and pressure conditions are available from filling‐simulating software. The principles rest on finite difference schemes computing simultaneously temperature and velocity of compressible non‐Newtonian fluid in a filled cavity. The pressure field is determined from an equation of state at any time, owing to a mass balance in each gridmesh. The meaningful results of the simulation are local shrinkage and a good approximation of final weights of finished products. The algorithm is essentially checked for the influence of physical, thermal, and processing parameters on the cavity pressure for the injection of a polystyrene (Gedex 1541) into a rectangular mold cavity.
A kinetic study of the thermal decomposition of poly(aryl‐ether‐ether‐ketone) (PEEK) in nitrogen
Authors: Day M. , Cooney J. D. , Wiles D. M. 
Published: December 2004

AbstractThe kinetic parameters of the thermal decomposition of poly(aryl‐ether‐ether‐ketone) (PEEK) in a nitrogen atmosphere have been obtained using an isothermal weight‐loss method. Several mathematical approaches have been used to obtain the Arrhenius parameters based upon the use of different reaction models. The values obtained for the activation energy (E = 198.4 to 219.7 kJ/mol) and preexponential factor (log A = 11.1 to 12.3 min−1) fall within a narrow range, irrespective of the method of calculation. Although the kinetic data most closely fits an Avrami two‐dimensional nucleating model, the data can be just as easily described by a first‐order rate law.
Effect of physical aging on tensile stress relaxation and tensile creep of cured EPON 828/epoxy adhesives in the linear viscoelastic region
Authors: Vleeshouwers S. , Jamieson A. M. , Simha R. 
Published: December 2004

AbstractThe effect of physical aging on viscoelastic properties was studied for several cross‐linked epoxies in the glassy state. Tensile creep and tensile stress relaxation were measured during isothermal physical aging, following rapid quenching of samples annealed above the glass‐transition temperature (Tg). The momentary creep curves measured at 21°C, 45°C, and 61°C below Tg for different epoxies could be fitted to an empirical equation for the creep compliance D(t):

Values for β and to were obtained, and the dependence of to on the aging time was determined. Shift factors were calculated to investigate changes in molecular mobility during physical aging. The momentary stress relaxation was measured on the same epoxy materials as used for the creep studies. The stress relaxation curves were fitted to the following equation for the tensile modulus E(t):

Values for α and to were obtained. The influence of physical aging on‐to was again studied by calculating shift factors as a function of the aging time. The results are compared with the results of the creep tests and discussed in the context of current molecular theories of physical aging of glassy polymers.
Effect of die wall cooling or heating on extrudate swell
Authors: Vlcek J. , Vlachopoulos J. 
Published: December 2004

AbstractA general purpose finite element program was used to study polymer extrudate swelling. It is shown that viscosity variations due to externally applied cooling or heating have a significant influence on the swelling ratios of axisymmetric and planar extrudates. The effect is more pronounced at high Peclet and Weissenberg numbers. Swelling due to thermal effects and swelling due to viscoelasticity are not additive because of interrelations between the various mechanisms.
3‐D structure‐property relationships in rolltruded polymers. Part I: Mechanical property enhancement in three directions
Authors: Berg E. M. , Sun D. C. , MaGill J. H. 
Published: December 2004

AbstractThe effect of rolltrusion, a solid state deformation process, on the three dimensional mechanical properties of several polymers has been measured. Polymers studied included isotactic polypropylene (iPP), polyvinylidene fluoride (PVDF), and propylene/ethylene block copolymers. It was found that mechanical strength is enhanced triaxially for all these specimens upon rolltrusion. Material stiffness also exhibits 3‐D improvement, depending on the polymer type and processing conditions. These new results are discussed in regard to some structural models in the literature.
Rheology‐morphology relationships in nylon 6/liquid‐crystalline polymer blends
Authors: La Mantia F. P. , Valenza A. , Paci M. , Magagnini P. L. 
Published: December 2004

AbstractExtrusion measurements have been carried out on blends of nylon 6 and a liquid‐crystalline copolyesteramide (LCP). The flow curves at low temperature show a behavior similar to that of pure LCP with a rapid rise of the viscosity at low shear rates. At high shear rates the viscosity is lower than that for each of the two components. This minimum has been attributed to the lack of interactions between the two phases and to the formation of fibrils of the LCP phase. The SEM analysis shows, indeed, that fibrils of the LCP phase are produced in the convergent flow at the inlet of the capillary at high shear rates. These fibrils are lost during the flow in the long capillary.
The interface in binary mixtures of polymers containing a corresponding block copolymer: Effects of industrial mixing processes and of coalescence
Authors: Plochocki A. P. , Dagli S. S. , Andrews R. D. 
Published: December 2004

AbstractIn theories of the minor phase (domain) formation in polyblends rendered as emulsions it is usually assumed that the size and shape of the domains are the result of melt viscosity effects (Taylor, Wu) or viscoelasticity effects (VanOene, Elmendorp) being balanced by interfacial tension. This assumption would predict a monotonic decrease of the domain size to a final limiting size with increasing energy of mixing. However, a systematic study of the dependence of domain morphology on industrial mixing processes which was carried out on a “model” LDPE/PS (2/1) mixture and the related polyalloy (i.e., the same mixture with a corresponding block copolymer as compatibilizer) does not support this expectation. Doirain size was found to go through a minimum as mixing energy was increased. A similar minimum was seen in data on specific volume of the melt vs. mixing energy, which indicates a correlation between melt specific volume and domain size. Calculation of the approximate surface area of the domains using a simple model of domain shape indicated that total interfacial energy in the polyblend and/or polyalloy is a trivial part of the mixing energy introduced. These calculations also indicated that if compatibilizer was located entirely at the interface, the surface layer would have a thickness of about 90 nm. Some micrographs seem to show such a surface layer. We propose that an abrasion mechanism is responsible for the early stage of the dispersion process, and that the final domain size may be controlled by a dispersion‐coalescence equilibrium. This is compared with the theories of final particle size proposed by VanOene and Wu.
Development of an in‐line rheometer suitable for reactive extrusion processes
Authors: Pabedinskas A. , Cluett W. R. , Balke S. T. 
Published: December 2004

AbstractThis paper presents the development of a novel in‐line extrusion rheometer based on the flow of polymer through a wedge (vertically tapered slit). This rheometer is suitable for measuring changes in rheological properties on‐line during reactive extrusion, because it can be used to estimate the viscosity for a range of shear rates without the need to change the polymer flow rate (i.e., extruder throughput). Equations have been developed to estimate the parameters of the power‐law equation, used to describe the viscosity‐shear rate relationship, from measurements of pressure drops along the wedge. An experimental in‐line wedge rheometer has been built and used to measure the viscosity for a series of polypropylenes prepared via reactive extrusion. Viscosity measurements from the experimental in‐line wedge rheometer are compared with measurements from a capillary rheometer. Good agreement is found between the capillary and wedge rheometer measurements.
Resin flow through fiber beds during composite manufacturing processes. Part I: Review of newtonian flow through fiber beds
Authors: Skartsis L. , Kardos J. L. , Khomami B. 
Published: December 2004

AbstractA critical part of any master model used to simulate or control a composite material manufacturing process is the description of resin flow through the fiber bed. We present here a review of both theoretical and experimental studies of fluid flow through porous media, including fiber beds. For the practical porosity range of interest in continuous fiber composites processing (0.3< ϵ < 0.6), the permeability cannot be accurately described using the Blake‐Kozeny‐Carman equation, even though the flow is Newtonian at very low Reynold's number. For aligned fiber situations, the Kozeny constant,k, deviates radically from theory, depends on bed nonuniformities, and is only constant over very narrow porosity ranges. Thus, one cannot experimentally determinekat high porosities and use this value to describe low porosity situations. Theoretical attempts, based on perfectly spaced and aligned arrays of cylinders, adequately describe the transverse permeability of ideal fiber beds in the high porosity range, but do not succeed at porosities below 0.6. For axial flow through aligned fiber beds, the theory yields permeabilities much lower than are experimentally observed throughout the entire porosity range. For randomly arranged fibers, random cylinder theory also predicts permeabilities that are significantly lower than are measured.
Resin flow through fiber beds during composite manufacturing processes. Part II: Numerical and experimental studies of newtonian flow through ideal and actual fiber beds
Authors: Skartsis L. , Khomami B. , Kardos J. L. 
Published: December 2004

AbstractProper description of the resin flow through fibrous media is an important input to the modeling of composite manufacturing processes. Based on our conclusions in a recent review of pertinent literature (see Part I, this issue), Newtonian flow through ideal cylinder arrangements has been analyzed and measured. The analytical and numerical solutions agreed well with both our own experimental observation and those of others. Experiments with actual carbon fiber beds revealed significant deviations from ideal bed behavior. These deviations include dependence of the permeability on the nature of the permeant and the applied pressure difference, both of which make questionable the use of the Blake‐Kozeny‐Carman (BKC) equation to describe flow in real carbon fiber beds. Experiments that simulate the autoclave process by featuring combined permeation and consolidation of fiber beds have yielded additional dependencies of the permeability on process characteristics, such as the consolidation load and the original resin‐rich areas within the fiber beds.
The effects of transcrystalline interphase in advanced polymer composites
Authors: Chen Eric J. H. , Hsiao Benjamin S. 
Published: December 2004

AbstractSurface‐induced transcrystallization in fibers has been reported in some advanced polymer composites. It is believed that transcrystalline interphase may affect stress transfer efficiency between the reinforcing fiber and the matrix. In this study, attempts were made to examine the effects of transcrystallinity on composite performance, particularly on fiber‐matrix interfacial bond strength, and to investigate possible attributes of transcrystallization. Three polymer resins, poly(etherketoneketone) (PEKK), poly(etheretherketone) (PEEK), and poly(phenylenesulfide) (PPS), and four types of fiber, polyacrylonitrile (PAN)‐based AU‐4 (untreated AS‐4) carbon, pitch‐based carbon, poly (p‐phenylene terephthalamide) (PPDT) aramid, and E‐glass were used. It was found that PPDT aramid and pitch‐based carbon fibers induce a transcrystalline interphase in all three polymers because of an epitaxial effect. Under certain conditions, transcrystallization was also observed in PAN‐based carbon and E‐glass fibers, which may be partially attributed to the thermal conductivity mismatch between the fiber and the matrix. Plasma treatment on fiber surface showed a negligible effect on inducing transcrystallization, whereas solution‐coating of PPDT on the fiber surface showed a positive effect. The Microdebonding test, which measures the interfacial bond strength between the fiber and the matrix, consistently showed more than 40% increments for various single filament systems with transcrystalline interphase versus without. However, the effects of transcrystallinity on the interfacial bond strength appeared to decrease as the fiber content increased in composites.
Interpretation of fiber fragmentation in carbon/epoxy single fiber composites: Possible fiber pre‐tension effects
Authors: Scherf J. , Wagner H. D. 
Published: December 2004

AbstractThe fiber straightening pre‐tension applied during the sample preparation of single fiber composites is suggested here to significantly affect the number of fragments as well as the value of the Kelly‐Tyson interface shear strength obtained from single filament composite tests. This implies that fragmentation tests performed under seemingly identical conditions, but in which the fiber pre‐tension is not accurately controlled during sample preparation, might yield widely differing experimental results. We present and discuss a new set of experimental results dealing with fiber pre‐tension effects in carbon/epoxy single fiber composites.
Environmental stress cracking resistance of blow moded poly(ethylene terephthalate) containers
Authors: Tekkanat Bora , McKinney Bryan L. , Behm Dale 
Published: December 2004

AbstractA method is developed for determining the environmental stress cracking resistance (ESCR) of blow molded poly(ethylene terephthalate) (PET) containers. By this method, the internal chamber of a container is presurized in 68.9 kPa (10 psi) increments while the outside of the base is being exposed to an environmental stress cracking (ESC) agent. The base of the container is examined after each 68.9 kPa of pressurization if crazing has occurred. The process is continued until a threshold value of craze initiation pressure (CIP) can be determined. Low CIP for the type of containers tested generally corresponds to a high rate of field failures. The method does not only gage the susceptibility of different types of one‐piece PET containers to ESC but also provides helpful information to improve the container designs.
A pulse rheometer for reacting foams
Authors: Carriere Craig J. , Bank David H. , Christenson Christopher P. 
Published: December 2004

AbstractA foam rheometer has been developed based on the impulse theory of linear viscoelasticity. The rheometer is a large‐volume parallel‐plate device which operates under gap‐loaded conditions, and is designed as an add‐on fixture for the Materials Testing System Model 312. The rheometer provides characterization data of the pre‐gel (via the zero‐shear viscosity) or the post‐gel (via the equilibrium modulus) properties of a foaming cellular polymer with a precision of better than ± 15%.
DSC and FTIR characterization of biodegradation of polyethylene
Authors: Raghavan D. , Torma A. E. 
Published: December 2004

AbstractAspergillus niger, a fungus, was used in the degradation of commercially available thermoplastic polyethylene films. Quantitative calorimetric measurements performed on as‐received, abiotic, and biotic treated polyethylene samples, revealed that the amorphocity of the sample decreases during biodegradation. In addition, it was found that the external substrates (sucrose) in the growth medium influenced the biodegradation process of polyethylene. Furthermore, the crystallinity data on different biotreated samples indicated that the adapted microorganisms were able to metabolize a small portion of polyethylene. The significance of the Fourier transform infrared (FTIR) results of polyethylene samples have been discussed.
Influence of a core/shell rubber phase on the morphology and the impact resistance of a PC/SAN blend (75/25)
Authors: Debier D. , Devaux J. , Legras R. , Leblanc D. 
Published: December 2004

AbstractAt 75/25 concentration ratio, bisphenol a polycarbonate (PC)/styreneacry‐lonitrile copolymer (SAN) blend has poor impact resistance compared to PC/ABS. A rubber phase methacrylate‐butadiene‐styrene (MBS) of core/shell type was dispersed in PC/SAN blend. The morphology of the unmodified and modified blend was investigated. The influence of the acrylonitrile ratio in the SAN on the microstructure was studied. It clearly shows that core/shell resides at the interface between PC and SAN. It seems that core/shell particles enhance the adhesion between the different phases. Their presence influences the interface mobility; i.e., the coalescence of the dispersed phase observed in pure PC/SAN is considerably reduced when the MBS particles are added. The impact resistance of the samples was correlated with the morphology.
Rubber modified epoxy resin. I: Cure kinetics and chemorheology
Authors: Kim Dae Su , Kim Sung Chul 
Published: December 2004

AbstractThe curing and vitrification effect during the reaction of ATBN modified epoxy resin was studied through the dynamic differential scanning calorimetry method and a new reaction kinetic equation containing generalized WLF equation was developed to describe the reaction rate at both glassy and rubbery state. An autocatalytic mechanism was found to describe adequately the cure kinetics of the rubber modified epoxy resin and the overall order of reaction was assumed to be 2. The kinetic parameters were determined from the DSC data through the Marquardt's multivariable nonlinear regression method and Runge–Kutta integration technique. The presence of rubber indicated minor effect on the cure kinetics of epoxy resin. The Arrhenius type viscosity function was employed to establish a relationship between viscosity data measured by RMS and chemical conversion calculated from the reaction kinetic equation.
The use of flexural tests in the study of environmental stress cracking of polymers
Authors: Arnold J. C. 
Published: December 2004

AbstractThe use of bend testers for the determination of critical strains in the study of environmental stress cracking has been assessed. Using the combination of polystyrene in ethanol, various factors affecting the measurement of critical strains were investigated, including the strain applied during the bend testing, the time of immersion in the liquid prior to straining, the surface finish, and the extent of physical aging. It was concluded that the best determination of critical strain is the strain at which a sample just shows signs of crazing, rather than the strain at the outer edge of a band of crazes. The measured value of critical strain increases with increased prior immersion time, decreased surface roughness, and decreased physical aging time. Reasons for these variations are discussed. It is concluded that although the use of bend testers is valuable for qualitative testing, careful testing methodologies need to be adopted for it to be a useful quantitative test.
History of commercial polymer alloys and blends (from a perspective of the patent literature)
Authors: Utracki L. A. 
Published: December 2004

AbstractPolymer blends are defined as mixtures of at least two polymeric species. Thus, the first patent polymer blend was a mixture of natural rubber, NR, with gutta percha patented by Alexander Parkes, an artist of Birmingham, in 1846. The first man‐made polymer, nitrocellulose, NC was prepared by Braconnot in 1833. The resin was commercialized in 1868, but its first blends (with NR) were patented three years earlier. The first patent on blends of two synthetic polymers was granted in 1928 for poly(vinylchloride)/poly(vinylacetate), PVC/PVAc (latex blending). During the intervening 65 years, the polymer blend patent literature grew at an exponential rate; since 1983 the annual output has doubled, to exceed 3000 patents/year in 1993.