bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effect of tension during drying on the structure and mechanics of poly(p‐phenylene benzobisthiazole) fibers
Authors: Pottick L. A. , Farris R. J. 
Published: May 2005

AbstractThe effect of tension during drying on the structure and mechanics of poly(p‐phenylene benzobisthiazole) (PBT) fibers has been investigated. The application of tension during drying on PBT fibers spun from anisotropic solutions of PBT/Polyphosphoric acid (PPA) results in an enhancement of tensile modulus and yield strength with a reduction in strain to break. The alterations in the tensile properties can be attributed to the straightening of the wet fibrillar network and the reduction in the axial compressive stresses which develop during drying. Modifications in the mechanical behavior of PBT fibers through tension drying can be achieved regardless of the initial spin draw ratio of the fiber. Additionally, tension drying provides a means to maximize the potential stiffness of PBT fibers which have a low spin draw ratio. Lastly, these investigations show that in the processing of PBT fibers, preventing the onset of buckling and aligning the wet fibrillar network with tension during drying is more effective in enhancing the tensile properties than straightening the dried buckled fibers.
Smoothing the electromagnetic heating pattern in polymers
Authors: Inkpen S. L. , Melcher J. R. 
Published: May 2005

AbstractIn the production of polymers, particles and fibers are often added for coloring and/or improvement of mechanical, electrical, and thermal properties. Carefully choosing the electrical properties and size of these additives can allow manipulation of the electrical properties of the composite so that the material can then be heated in both the electric and magnetic fields. Heating can be induced by fields at microwave frequences, where the electric and magnetic fields tend to be concentrated in different regions, or by fields that are quasistatic. These features add a degree of freedom in smoothing the total heating pattern. Models for predicting the electrical properties with the addition of particles or fibers are developed and verified experimentally. Engineering guidelines are established in choosing the electrical properties and size of the additives. Experimentally, a rectangular cavity at 2.45 GHz is used to heat a casting resin with a 5.7 micrometer aluminum powder additive, demonstrating the dramatic smoothing in the heating, pattern made possible by using these additives. Some examples are also suggested to indicate the use of this technique in quasistatic heating configurations.
Experimental and theoretical evaluation of a spiral disc extruder
Authors: Krein H. L. , Plumtree A. , Rudin A. 
Published: May 2005

AbstractA 5‐inch diameter disc extruder was operated with a commercial polypropylene polymer to provide comparison data and the model predictions were compared to machine performance as a function of extrusion conditions and polymer characteristics. The mathematical model used for comparison has been described previously by the authors.
Solid‐phase flow behavior of polymers
Authors: Halldin G. W. , Lo Y. C. 
Published: May 2005

AbstractThe solid‐phase flow behavior of polymers is very important in the mechanical performance and testing of solid polymers and in solid‐phase forming. This paper includes an extensive characterization of the solid‐phase flow curve for a wide range of commercially important polymers. Rigid semicrystalline, ductile semicrystalline, tough ductile amorphous, and two‐phase ductile amorphous resins were studied in both tension and compression. It is clearly shown that semicrystalline polymers normally exhibit a load drop upon yielding due only to geometrical strain softening while the amorphous polymers exhibit yield drops due to material strain softening. New flow equations are given that closely model the observed behavior for all types of materials, over the entire range of strain.
Polymerization and crystallization behavior of anionic nylon 6
Authors: Iobst Stanley A. 
Published: May 2005

AbstractThe kinetics of the activated anionic polymerization of caprolactam to nylon 6 was studied by the adiabatic temperature rise technique. This allowed very rapid reaction conditions to be studied. The polymerization was activated by diisocyanate and catalyzed by sodium caprolactamate, produced in situ by the addition of sodium hydride. The temperature rise measurements were used to generate Arrhenius curves of the rate data. Several isocyanates were investigated, all giving similar rate curves. The reaction rate was reduced, however, when the activator concentration exceeded the catalyst concentration. To model the actual rapid molding conditions, time vs. temperature reaction profiles were measured for thin plaque castings. In these reaction profiles, two successive exotherms were observed. The first was the polymerization exotherm, and the second was determined to be the crystallization peak. This second exotherm allowed the direct observation of crystallization times within the closed molds. The crystallization times were found to depend strongly on the mold temperature and to a lesser extent on the monomer temperature. The crystallization times were minimized at a 150°C mold temperature. At higher temperatures, the crystallization rate was significantly slower, while at lower temperatures, the slow rate of polymer formation delayed the onset of crystallization. This study has demonstrated the value of using temperature monitoring as a means of studying the polymerization and crystallization behavior of nylon.
Rheological properties of a liquid crystalline copolyester
Authors: Bhattarcharya S. K. , Misra A. 
Published: May 2005

AbstractRheological studies of an experimental liquid crystalline (LC) copolyester were carried out using a capillary rheometer and a cone and plate rheometer. Rheological characteristics of the polymer in the nematic state were observed. The nematic melt was found to be pseudoplastic and the degree of pseudoplasticity varied with shear rate. Melt viscosity was found to decrease with shear rate. Negative die swelling was observed at the exit of the capillary rheometer at temperatures marginally above the solid‐nematic transition temperature of the polymer and was also found to be a function of shear rate. The dynamic mechanical properties of the polymer were studied as a function of temperature. The activation energies of flow and of dynamic mechanical deformation were calculated.
Ultrasonic processing of thermoplastic foam
Authors: Byon Sung K. , Youn Jae R. 
Published: May 2005

AbstractUltrasonically induced bubble formation for the production of thermoplastic foam was investigated experimentally and theoretically as a basic study. A general purpose polystyrene and blends of low density polyethylene and polyethylene wax were saturated with nitrogen gas under various pressures and the ultrasonic excitation was applied to the polymer system upon release of gas pressure. The ultrasonic nucleation of bubbles in the polymer matrix was modeled by utilizing the classical nucleation theory. The negative pressure generated by the ultrasonic excitation was considered as the environmental pressure at the moment of nucleation. The experimental results showed that the heterogeneous nucleation must be used for ultrasonic foaming of the viscous fluid and the homogeneous nucleation for the low viscosity fluid. The theoretical analysis also indicated that the ultrasonic nucleation can be applied to the production of thermoplastic foam if the ultrasonic excitation generates large enough negative pressure.
Measures of mixing in laminar flow
Authors: Bigio David , Stry William 
Published: May 2005

AbstractThe general domain in which this work resides is that of mixing in creeping flows. Mixing, in this context, refers to the stretch of an interfacial line, or area in a strain field. The advancement of mixing technology is applied to the design of continuous mixers used in polymer processing. The geometric designs included single screw extruders, static motionless mixers, and co‐ and counter‐rotating twin screw extruders. The co‐rotating twin screw extruder was chosen to be studied in detail since it enjoys wide applications and, for which, little understanding of the contribution to mixing in the different screw geometries is known. In order to evaluate the rate of mixing for the non‐uniform strain history flows, the method for measuring mixing had to be reexamined and broadened. An automated method has been developed which incorporates a digital camera and a computer to analyze the cross‐sections of interest. Two measures of mixing—the correlation function and the distribution function—are developed to describe mixing in these regimes. These measures are applied successfully to the mixer geometries revealing subtle differences as to the nature of mixing in each.
Dynamic‐mechanical and dielectric characterization of PEEK crystallization
Authors: D'Amore A. , Kenny J. M. , Nicolais L. , Tucci V. 
Published: May 2005

AbstractDynamic‐mechanical and dielectric characterization of the cold crystallization of PEEK has been performed in order to develop a non‐destructive evaluation method of crystallinity in thermoplastic matrices. The Avrami approach is applied here to describe the Poly(ether ether ketone) (PEEK) crystallization kinetics after an appropriate reduction of dynamic‐mechanical and dielectric parameters. Avrami exponents obtained from dielectric characterization are comparable with those obtained with DSC measurements reported in literature, while the exponents obtained from the dynamic‐mechanical characterization are higher, reflecting also changes in the aspect ratio of the growing crystals. Variations in the glass transition temperature detected during cold crystallization are analyzed and analogies between PEEK and PET are discussed.
Polymer blends containing liquid crystals: A Review
Authors: Dutta D. , Fruitwala H. , Kohli A. , Weiss R. A. 
Published: May 2005

AbstractThis paper reviews the literature of polymer blends containing low and high molar mass liquid crystals. Low molar mass liquid crystals have been used as plasticizers for thermoplastic polymers and in applications such as electrooptics, optical recording media, and membranes. High molar mass liquid crystalline polymers have been primarily used in polymer blends as processing aids and as an incipient reinforcing phase for “self‐reinforced” materials. This review discusses the phase behavior, rheology, and mechanical properties of these blends.
On the uniaxial extensional flow of polystyrene/polyethylene blends
Authors: Utracki L. A. , Sammut P. 
Published: May 2005

AbstractThe uniaxial extensional flow behavior of polystyrene/low density polyethylene blends (PS/LDPE) was studied using a Rheometrics Extensional Rheometer, Model RER‐9000, at 150°C within the range of the extension rates \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon $\end{document} = 0.0005 to 1.0 (s−1). The measurements were repeated several times at each deformation rate to ascertain reliability. The effect of the suspending silicone oil was found to be negligible.
Reactive processing of polystyrene‐co‐maleic anhydride/elastomer blends: Processing‐morphology‐property relationships
Authors: Willis J. M. , Favis B. D. , Lunt J. 
Published: May 2005

AbstractThe morphology and impact properties of polystyrene‐maleic anhydride/bromobutyl rubber blends have been studied as a function of interfacial modification and melt processing conditions. It is found that dimethylaminoethanol (DMAE) serves as a reactive compatibilizing agent for these blends and that the addition of DMAE results in a five‐fold reduction In the size of the dispersed phase. Evidence for covalent bond formation between the DMAE and the elastomer and reactive polystyrene phases is presented. The volume average diameter of the minor phase increases significantly as the screw rotation speed and the material throughput increase. In fact, control of various material and processing parameters can be used to effectively control the particle size distribution during compounding. Impact strength measurements are shown to be clearly dependent on the quantity of DMAE in the system as well as the concentration of elastomer. Saturation of the interface with DMAE is shown to be an important consideration.
Reflection methods for the study of polymer interfaces
Authors: Walsh David J. , Sauer Bryan B. , Higgins Julia S. , Fernandez Marisa L. 
Published: May 2005

AbstractThe direct study of polymer Interfaces is very difficult. Small angle scattering methods have been most successfully applied to block copolymer Interfaces where the morphology is well known. Other techniques such as electron microscopy, Rutherford back scattering, and forward recoil spectroscopy generally only give resolution of the order of 10 nm. Here we describe two techniques which have only recently been applied to polymer interfaces, neutron reflection, and spectro‐scopic ellipsometry. Both reflection techniques examine planar samples and give compositional information in the depth direction. Neutron reflection gives a resolution of 0.5 nm and spectroscopic ellipsometry may give better than 5 nm. We will describe experiments using neutron reflection which measure the inter‐facial thickness between two immiscible polymers and experiments using both techniques which measure the interdiffusion of miscible polymers. Other applications and limitations of the techniques will also be discussed.
Poly(ethylene terephthalate) crystallization as a method for microlithography
Authors: Sonnenschein M. F. , Kotliar A. M. , Roland C. M. 
Published: May 2005

AbstractThermal lithography on poly(ethylene terephthalate) (PET) is carried out by inducing crystallization through selective exposure of amorphous films to Infrared radiation. The obtained images can be smaller than the wavelength of the CO2 laser light. This circumvention of the diffraction limit is accomplished by taking advantage of the non‐linear temperature dependence of the crystallization rate. The optical marking process is reversible through simple melting of the crystalline images. The complementary process, selective melting of an initially crystalline film, can also be accomplished. The use as a heat sink of a mask which forms the image pattern is demonstrated.
Accelerated test for evaluating slow crack growth of polyethylene copolymers in igepal and air
Authors: Ward Andrew L. , Lu Xici , Brown Norman 
Published: May 2005

AbstractThe time for brittle failure by slow crack growth for 22 polyethylene copolymers was measured in Igepal and air. The notched tensile tests were conducted in Igepal and air at 50°C and 4.2 MPa and in air at 80°C and 2.4 MPa. For failure times less than 103 min, the difference between the Igepal and air environments was not measurable. As the failure time increased beyond 103 min, the ratio of failure in air compared to that in Igepal increased so that for the very highest failure times of 5 × 105 to 108 min in air, the failure time in Igepal was reduced by 25—50 times. The correlation between the Igepal and air tests was generally good with respect to all types of polyethylene. However, a separation of the polyethylenes with respect to their comonomer, butene, hexene, or octene improved the correlation. The resistance to slow crack growth of all the current commercial polyethylene copolymers can be assessed by a notched tensile test in Igepal in about a week or less.
The manufacture of continuous polymeric filaments by the melt‐blowing process
Authors: Kayser John C. , Shambaugh Robert L. 
Published: May 2005

AbstractThis paper presents an experimentally‐based analysis of the continuous filament regime of the melt‐blowing process. The experiments were performed with a versatile air‐polymer die, several die operating temperatures, and three different polymer feed resins. The measurements discern the effects upon the final fiber diameter of the following input parameters: die dimensions, die temperature, polymer feed resin, and both the air and polymer mass flow rates. An empirical model equation is developed which relates these input parameters to the final fiber diameter. In addition, the conditions which result in a transition of the filament from continuous (or stable) to discontinuous (or unstable) are quantified. The model equation and the transition or stability information are then used to predict the behavior of the melt‐blowing process for a wide range of case studies involving the input parameters noted above. The data and empirical model are of considerable utility for developing new die designs, for comparison with theoretical models, for predicting fiber stability, and for explaining the behavior of current industrial melt‐blowing processes.
Mathematical model and experimental investigation of polycarbonate pellet drying
Authors: Munjal Sarat , Kao Che‐I 
Published: May 2005

AbstractAn easy to use, spreadsheet based, mathematical model for drying of strand cut polymer pellets has been developed and experimentally verified. This particle‐scale model is based on internal mass‐transfer controlled diffusion in the pellet. Examples of its usage in correlation and prediction of the effects of the drying‐gas temperature, humidity, and pellet dimensions are presented. Application of the particle‐scale model to the design of a countercurrent hopper drier is discussed. Even though examples are limited to water removal from poly(bisphenol‐A)carbonate pellets, the model is general and may be used for the removal of other non‐solvating low‐concentration molecules from polymers with isotropic morphology.
Impact modification of styrene‐acrylonitrile copolymers by methyl methacrylate grafted rubbers
Authors: Keskkula H. , Kim H. , Paul D. R. 
Published: May 2005

AbstractMonodisperse methyl methacrylate grafted latex rubber (MMA‐g) particles (0.12‐0.13 µm) have been used for the impact toughening of a series of styrene‐acrylonitrile (SAN) copolymers of varied AN content. It was found that the MMA‐g particles are most effective in toughening SANs containing about 25 to 34% AN. Mechanical properties, interphase adhesion, mechanical dilatometry, and phase morphology by transmission electron microscopy were determined on blends containing 20‐30% rubber. Also, the miscibility range of SANs and poly(methyl methacrylate) (PMMA) graft was considered in attempting to analyze the relationships between the mechanical properties and the characteristic features of the blends. Issues relating the impact strength and deformation mechanisms, interphase adhesion, and particle morphology are discussed. It appears that the high impact strength of some of the blends may be caused primarily by certain morphological features such as particle clustering or small interparticle distances. Thus, craze initiation, shear yielding, and significant matrix deformation may all contribute to the overall ductility of the blend.
Fluidity and optimum packing in suspensions of mixed dissimilar particles
Authors: Tsenoglou Christos , Yang Soohyeon 
Published: May 2005

AbstractThis is a study on the rheological properties and packing efficiency of a fluid suspension, composed of a mixture of two dissimilar particulate species. A generalized analytic expression for the viscosity of the blend is first developed, and then utilized to derive quantitative ways of maximizing the fluidity and optimizing the filling capacity of the composite system. These, results are compared with earlier experimental and theoretical findings, and with the rheological measurements performed in the course of this work on a series of calcium carbonate‐carbon black suspensions in poly‐dimethylsiloxane.
Structure and filtration properties of melt blown polypropylene webs
Authors: Lee Youngchul , Wadsworth Larry C. 
Published: May 2005

AbstractPolypropylene melt blown webs have been studied in terms of the relationships among the processing conditions, structure, and filtration efficiency. The effects of the processing conditions on filtration efficiency to aerosolized latex particles, pore size, fiber diameter, and air permeability have been investigated. The melt blowing process conditions investigated in this study were die and air temperatures, die‐to‐collector distance, and attenuation air flow rate at the die. The filtration efficiency has been found to increase linearly as mean pore size decreased. The degree of fiber‐entanglement increased, therefore, the pore size and air permeability decreased with increasing processing temperature, increasing air flow rate at the die, or decreasing die‐to‐collector distance. Average fiber diameter appeared to change little with die‐to‐collector distance, but decreased with increasing die temperature or with increasing air flow rate.
A direct injection gas‐liquid chromatographic method to monitor polymer melt devolatilization: Methyl methacrylate in poly(methyl methacrylate)
Authors: Edkins T. J. , Notorgiacomo V. J. , Biesenberger J. A. 
Published: May 2005

AbstractA new capillary gas chromatography method to monitor a residual monomer in a polymer is described. A short (5 m) crosslinked methyl silicone fused silica capillary column with flame ionization detection gave good separation efficiency and parts‐per‐million detection limits. Capillary gas‐liquid chromatography was superior to packed column analysis (SP 1000) in terms of both analytical utility and ease of use. This technique may prove useful for monitoring other monomer/polymer systems.
Migration of polymer blend components during melt compounding
Authors: Dekkers M. E. J. , Hobbs S. Y. , Bruker I. , Watkins V. H. 
Published: May 2005

AbstractIn this paper it is shown that a core‐shell impact modifier which is predispersed in one phase of a complex blend may migrate to another phase during melt compounding. The migration process appears to be driven by differences in the spreading behavior of the individual blend components. The details of the migration are analyzed by electron microscopy studies of partially compounded samples which were quenched, extracted, and separated from the extruder screw.
Environmental effects on the water absorption and mechanical properties of carbon fiber reinforced PPS and PEEK composites. Part II
Authors: Ma Chen‐Chi M. , Yur Shih‐Wen 
Published: May 2005

AbstractResearch has been conducted to investigate the water absorption in carbon fiber reinforced poly(ether ether ketone) (PEEK/CF) and poly(phenylene sulfide) composites (PPS/CF). Effect of humidity and temperature on tensile, flexural, and impact strength of these composites were also studied. Results indicated that the water absorbed in PPS/CF and PEEK/CF are 0.059 %wt, 0.130 %wt, 0.138 %wt, and 0.153 %wt at 80°C. 75 %RH and 85 %RH, respectively. The diffusion process is a classical Fickian diffusion in the temperature range investigated. The activation energies of diffusion are 667 cal/g‐mole (for PPS/CF) and 8934 cal/g‐mole (for PEEK/CF) at 80°C and 75 %RH. The retention of mechanical properties of these composites is very good under hot‐wet conditions. These composite materials can be served as high performance materials even in the hostile environment. PEEK/CF composites shows excellent mechanical properties retention even at 80°C, 75 %RH, and 85 %RH.
Mechanical properties in multidimensional composites
Authors: Jang B. Z. , Cholakara M. , Jang B. P. , Shih W. K. 
Published: May 2005

AbstractThe mechanical properties of three dimensional stitched composites were compared against those of the traditional two dimensional laminates. An attempt was made to correlate the change in properties to the change in the third directional fiber density. Tests conducted were the impact, three‐point bending, damage tolerance, end notched flexure, and bending fatigue test. The results of these tests show that the third directional fibers can effectively inhibit delamination by increasing the interlaminar shear strength. Three dimensional composites also possess better damage tolerance, fracture toughness, and fatigue life. However, a high stitching density can degrade the in‐plane properties of the composites.