bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bubble growth controlled devolatilization in twin‐screw extruders
Authors: Foster R. W. , Lindt J. T. 
Published: December 2004

AbstractAn experimental study of polymer soluticn devolatilization in a counterrotating twin‐screw extruder has been undertaken. In an effort to ultimately predict mass transfer rates in such a process, this work analyzes the experimental results to determine the controlling mechanisms in the separation of volatile components from the polymer. The devolatilization process at hand encompasses the heavily foaming and nonfoaming regimes. Historically, the literature has centered primarily around the highly concentrated, bubble‐free diffusion‐controlled devolatilization regime. The analysis presented in this paper centers on the performance of the heavily foaming stages of the process. Recent and previously reported (1) data on the polystyrene/ethylbenzene (PS/EB) system, as well as newly collected data on the poly(methyl methacrylate)/methyl methacrylate (PMMA/MMA) system, are analyzed. In the foaming stages of the process, two regimes have been found. These regimes are differentiated by the availability of volume into which the foam can grow. Deformation and mixing effects appear to be secondary. Furthermore, temperature changes across the range of realistic operating conditions appear to affect mainly the thermodynamic driving force. It is only at extremely high temperatures that these effects are truly controlling.
Properties of elongational flow injection‐molded polyethylene part 2: Influence of processing parameters
Authors: Cabarcos E. López , Bayer R. K. , Zachmann H. G. , Calleja F. J. Baltá , Meins W. 
Published: December 2004

AbstractIn the first part of this series, the influence of mold geometry was examined with reference to the improvement of the mechanical properties of elongational flow injection‐molded polyethylene. In the present study (Part 2), processing parameters have been investigated and the physical properties of the moldings examined. It is confirmed that mainly two parameters, the temperature of the melt and the pressure on the solidifying mold, govern the injection process. Results are discussed in terms of the molecular orientation that is developed during the filling process and depends on the temperature of the melt. The application of high pressures leads to a pressure‐induced crystallization effect that freezes in the molecular orientation within the mold.
Microstructural diagnosis of block copolymer nonlinear mechanical properties. II: Free recovery from large tensile deformations
Authors: Diamant Joram , Williams Michael C. 
Published: December 2004

AbstractThree styrene‐butadiene‐styrene (SBS) block copolymers were cast into sheet form, and the resulting microphase‐separated specimens were tested in tensile free recovery. After an initial strain of 300%, specimens were released and their lengths measured for about a week. For one polymer, the recovery curves are presented for seven temperatures in the range −40 to +80°C; other data are given at 22°C. Analysis of the recovery curves, using as the model a series assembly of Kelvin elements, obtains time constants for microstructural repair and explains the temperature dependence in terms of the microstructural interphase and its partial vitrification. Differences among the three polymers can be interpreted by recognition of styrene‐block molecular weights, as well as by the volume fractions of the domain styrene cores and interphases. Additional structural information arises from torsion pendulum experiments over −120 to 100°C for unstretched, stretched (300%), and partially recovered samples.
Physical properties of blends of polycarbonate and a liquid crystalline copolyester
Authors: Nobile M. R. , Amendola E. , Nicolais L. , Acierno D. , Carfagna C. 
Published: December 2004

AbstractBlends of polycarbonate (PC) and poly(ethylene terephthalate‐co‐p‐oxybenzoate) (PET/PHB60) were prepared by melt‐blending. Physical and/or chemical interactions between the two phases of the system were studied by thermal analysis and infrared spectroscopy. Rheological measurements in shear flow were carried out both in the low and high shear rate regions in the temperature range of the existence of the mesophase. At low liquid crystalline polymer (LCP) content, the blends showed flow curves similar to those of the unfilled PC, while at higher LCP percentages the rheological behavior of the pure LCP was resembled. Moreover, in the whole shear range, the viscosity values of such blends were in between those of the pure polymers. The influence of the addition of 10% LCP on the mechanical properties of the PC was investigated. Fiber‐spinning was performed under different experimental conditions, and it was found that opportune drawing conditions are necessary to improve the modulus of the matrix. Morphological analyses of the pure LCP and of the blends were related to the rheological and mechanical behavior of these systems. While the LCP exhibited an elevated dimensional stability, the inclusion of the LCP in PC matrix did not improve the dimensional stability of the blends.
Cold compaction and sintering of ultrahigh‐molecular‐weight polyethylene containing a segregated iron network
Authors: Krishnamurthy V. , Kamel I. L. 
Published: December 2004

AbstractTo improve the powder processing behavior of ultrahigh‐molecular‐weight polyethylene, a conductive iron filler was distributed within the polymer in a segregated network. The filler level was kept at a minimum of 10 volume percent, which was sufficient to coat completely all the polymer particle surfaces. This filler level was low enough to avoid modifying the resin properties to a significant extent. Compaction of these filled samples showed a slower densification, under pressure, similar level of final densification at 80% densification parameter, and a doubling of plateau pressure value to 200 MPa in comparison with the unfilled polymer. The filler was found to reduce drastically the postcompaction relaxation time from 24 h to 6 h. The magnitude of the axial (compaction direction) relaxation was unchanged, but the radial relaxation was one quarter of that for the unfilled polymer. Sintering behavior showed improved densification because of lower dimensional changes during sintering resulting in 80% relative sintered density, higher than the 75% percent value for the unfilled polymer, but yielded a 20% lower sintered strength, An alternative process of rapid sintering by induction heating was explored, its feasibility demonstrated, and a recommendation is made to make powder processing of this polymer commercially attractive.
Intermolecular interactions and phase transition behavior of miscible polymer blends
Authors: Chee K. K. 
Published: December 2004

AbstractA linear equation is proposed to quantify the glass transition behavior of miscible polymer blends in terms of the polymer‐polymer interaction density parameter whose values are obtainable from the melting point depression method. This practical model is successfully applied to four series of binary polyblends containing poly(hydroxy ether) of biphenol A, poly(vinyl chloride), poly(vinylidene fluoride), and poly(2,4‐dimethyl‐1,4‐phenylene oxide) as the common components. Each of these groups of polymer systems exhibits a distinct type of intermolecular interaction that can be characterized by the two coefficients of the model equation. In connection with the present analysis, three novel expressions are introduced for describing the glass transition temperature—composition relations of the polymer systems of interest.
Structure of PPTA fibers derived directly from a liquid crystalline prepolymer dope in an organic solvent
Authors: Jin Jung‐Il , Park Ho‐Jin , Rhim Moo‐San , Kim Si‐Min 
Published: December 2004

AbstractThe structure and properties of the pulp‐like aromatic polyamide PPTA fibers prepared directly from a polymerization medium were studied by scanning electron microscopy (SEM), X‐ray diffractometry, and polarizing light microscopy. The morphology of the fiber appears significantly different from that of Kevlar and does not reveal a skin‐core structure. Regular defect bands and, thus, the regular clustering of the chain ends also could not be observed.
Novolac‐Based photoresists combining chemical amplification and dissolution inhibition
Authors: O'brien Michael J. 
Published: December 2004

AbstractThis paper concerns a more in‐depth examination of the different components which make up positive photoresists based on the combined principles of chemical amplification and dissolution inhibition. Included is a discussion of the requirements for materials to be used as dissolution inhibitors in this scheme as well as an example of an optimum compound‐t‐butyl‐cholate. Also considered are the effects of onium salt counteranions on resist performance including gel permeation chromatographic (GPC) analyses of the changes in novolac molecular weight distribution which can occur during irradiation and postbake.
A negative resist for KrF excimer laser lithography
Authors: Toriumi M. , Hayashi N. , Hashimoto M. , Nonogaki S. , Ueno T. , Iwayanagi T. 
Published: December 2004

AbstractThe design and preparation of a series of negative resists for KrF excimer laser lithography are described. Each resist is composed of poly(hydroxystyrene) and an aromatic azide. The base resin shows high transmittance of 62%/μm at 248 nm, when p‐ethylphenyl p‐azidophenylsulfonate. 4‐azido‐4α‐methoxy‐chalcone, 1‐(4 azidobenzylidene)‐3‐(α‐hydroxy‐4‐azidobenzyl)‐indene, 4,4α‐diazido‐3,3α‐dimethoxybiphenyl, or 1‐(4‐azidostyryl)‐5, 5‐dimethyl‐2‐cyclohexen‐1‐one is employed as a sensitizer. These azides are obtained by red‐shifting the absorption maxima to lower energy regions than the exposing wavelength of 248 nm. Transmittance of resists can be controlled from 10 to 30%. The resist is exposed with a KrF excimer laser stepper and developed in an alkaline solution. Sensitivities of about 15 mJ/cm2 are observed. A good, subhalf‐micron resist profile is achieved.The photochemical reaction mechanisms of poly(hydroxystyrene) and 4,4α‐diazido‐3,3α‐dimethoxybiphenyl were studied at 248 nm and 313 nm exposure. Quantum yield for photodecomposition at 248 nm is seven times larger than that at 313 nm, but dissolution‐inhibition effects are larger at 313 nm exposure. Consequently, the resist shows higher sensitivity at 313 nm than at 248 nm.
Epoxy resins for deep UV lithography
Authors: Stewart K. J. , Hatzakis M. , Shaw J. M. 
Published: December 2004

AbstractA negative resist based upon photo‐acid initiated cationic polymerization of an epoxy resin (1, 2) was reported in the early eighties with the advent of onium salts (3–5). An efficient acid generating onium salt, triphenylsulfonium hexafluoroantimonate (6), absorbs light in the deep UV producing acid upon direct photolysis in this region of the spectrum. The resin component of such a negative resist system must be optically transparent over the exposure wavelengths to obtain vertical image profiles. Another difficulty often encountered with crosslinking negative resists is swelling of the crosslinked matrix during development with organic solvents. This swelling manifests itself in distorted images and/or complete adhesion loss, especially when submicron features are involved. Our goal has been to address these problems and develop an organic developable deep UV resist capable of providing submicron images. Optically transparent commercial resins, styrene‐allyl alcohol copolymers, have been converted to glycidyl ethers, thereby providing cationically polymerizable functionalities. Careful choice of the resin was made to obtain reactive ion etch resistance, thermal stability, good adhesion, and coating properties. The synthetic procedure and characterization of the epoxy resin will be presented. The effect of the molecular weight distribution upon swelling during development and general solubility properties also will be discussed. Resist formulations exhibited sensitivities of 19 to 30 mJ/cm2 on a Perkin Elmer 500 in the deep UV (UV2) mode. The electron beam sensitivity is 3 to 5 μC/cm2 at 20 KeV. Submicron images have been generated in both optical and electron beam lithography.
Poly(Aryline imides) as E‐beam resist: Sensitivity and resolution
Authors: Chien James C. W. , Gong B. M. 
Published: December 2004

AbstractPolyamic acids synthesized from di‐trifluoromethyl methane bis(phthalic anhydride) and 4,4'‐diaminophyenyl sulfone (F‐1) and 4,4'‐diaminophenyl ether (F‐4) were found to have excellent negative E‐beam resist properties. The best materials contain about 90 percent imidized structural units having sensitivities of 1.5 to 2.5 μC cm−2 and contrast of 1.0 to 1.3. Polyamic acid of pyromellitic dianhydride and 4,4'‐diaminophenyl sulfone (P‐1) imidized to 97 percent exhibits useful positive E‐beam resist properties. Radiation induces imidization and chain scission to alter the solubility of the resist polymers resulting in the formation of latent images.
New high temperature stable positive photoresists based on hydroxy polyimides and polyamides containing the hexafluoroisopropylidene (6‐f) linking group
Authors: Khanna D. N. , Mueller W. H. 
Published: December 2004

AbstractIn this paper we describe the synthesis, characterization, and lithographic evaluations of novel positive photoresists based on hydroxy polyimides and polyamides containing 6‐F linking groups. The polymers were synthesized using solution condensation techniques and characterized using solution viscosity, GPC, FTIR, NMR, UV, TGA, and DSC. Tg's of these polymers range from 250 to 300°C. Both polyimides and polyamides are soluble in a variety of solvents commonly utilized for photoresist applications. When formulated with diazonaphthoquinone sensitizers, these polymers provide an improved high‐temperature resistant, aqueous base developable positive photoresist system with good photospeed, contrast, and resolution characteristics. High resolution relief images were obtained which are comparable to 1300 Series AZ type photoresists. No thermal deformation, loss in resolution or defects were noticed when relief patterns were annealed to 250°C. Additionally, the hydroxy polyamide based resists, when thermally annealed to 300°C, provide a photoresist system with even higher thermal stability (400 to 450°C) and excellent resistance to solvents. Also, the photoresist formulations have excellent storage stability at room temperature and can be processed like conventional positive photoresists using broad band UV radiation sources.
Design and analysis of a dual‐cavity coat‐hanger die
Authors: Lee Kwong‐Yang , Liu Ta‐Jo 
Published: December 2004

AbstractA method for the design and analysis of a dual‐cavity coat‐hanger die is presented in this paper. A macroscopic material balance and a microscopic flow analysis using the finite element method are combined to simulate polymeric fluid flow inside the die. Leonard's macroscopic procedure was adopted to include inertial, gravitational, and viscous effects, and the finite element method was then applied to estimate the contributions of inertial and viscous terms. In addition, the flow patterns in the outer cavity were computed by the finite element method so that the appearance of an undesirable vortex could be predicted. The residence time distributions for flow in the die were approximated by a simple, statistical approach. It was found through a case study that a dual‐cavity coathanger die can effectively reduce the flow non‐uniformities caused by fluid inertia and viscosity variations.
Time temperature dependence of dual coated lightguide pullout measurements
Authors: Overton B. J. , Taylor C. R. 
Published: December 2004

AbstractThe strength of the bond between primary coating and glass for a dual coated lightguide may be judged by fixing the coating to a substrate and pulling the glass out. The values obtained from such measurements are shown to exhibit a temperature and rate dependence similar to the mechanical properties of the primary coating for a given coating system. Here we combined temperature and rate data for a universal description of the coating to glass adhesion for a dual coating system.
Microstructure and ultimate properties of injection molded amorphous engineering plastics: Poly(ether imide) and poly(2,6‐dimethyl‐1,4‐phenylene ether)
Authors: Wagner Alan H. , Yu Jeong S. , Kalyon Dilhan M. 
Published: December 2004

AbstractSpecimens of two engineerig plastics i.e., poly(ether imide), PEI, and poly(2,6‐dimethyl‐ 1,4‐phenylene ether), PPE, were injection molded employing a 40t Van Dorn injection molding machine and industrial practices. The mold and melt temperatures and the injection speed were varied in a limited range which furnished acceptable samples. The density, birefringence, residual stress distributions, flexure and tensile properties, and crack development of the injection molded specimens were studied. Vacuum compression molded samples were also prepared to investigate the role played by the cooling rate in shaping microstructural distributions. The results revealed significant differences in the development of microstructure of the molded specimens of the two resins, which was related to rheology and molding conditions on one hand and to development of cracks and ultimate properties on the other hand.
Joining methods for plastics and plastic composites: An overview
Authors: Stokes Vijay K. 
Published: December 2004

AbstractJoining of plastics and plastic composites is becoming important because of the emerging structural applications of these materials. While providing an overview of all joining methods, this paper emphasizes the welding of thermoplastic materials. Different welding techniques, together with their main advantages and disadvantages, are briefly described. A selective bibliography, in which the 259 references have been arranged chronologically for each technology type, provides a guide to the literature.
Morphological and mechanical property studies of polymer extrudates obtained by the rotational extrusion process
Authors: Chung B. , Zachariades A. E. 
Published: December 2004

AbstractThe orientation of the reinforcing fibers in glass fiber filled polypropylene tubular extrudates has been controlled effectively by the superposition of the linear flow in a melt extruder with torsional flow generated by rotating the capillary portion of the extrusion die of the extruder. The so produced extrudates have mechanical properties which can be balanced along the hoop and extrusion direction by adjusting the extrusion rate and the rotational speed of the die for example, the breaking load of 75N along the hoop direction increases by ∼40% when the capillary of the die was rotated at 80 rpm. At the same time the Young's modulus in the extrusion direction decreased from 1100 MPa under conventional extrusion conditions to 800 MPa.
Orientation and mechanical properties of polycarbonate‐ linear low density polyethylene blends
Authors: Ajji Abdellah 
Published: December 2004

AbstractFive blends of polycarbonate (PC) with linear low density polyethylene (LLDPE) were studied. Characterization of the blends was made by means of rheological measurements and domain morphology determined by SEM microscopy. A fine dispersion was obtained for the 25/75 PC/LLDPE. The blends were then oriented, LLDPE and 25/75 PC/LLDPE at room temperature, and the others at 165°C. For the hot drawn blends (50/50 and 75/25 PC/LLDPE), a significant increase in tensile strength and elongation at break is observed. For the room temperature drawn samples, modulus and tensile strength values increase whereas elongation at break decreases. This is explained in terms of morphological and molecular orientation effects. Comparison of the experiments to the predictions of different models for the modulus shows a good agreement for unoriented blends. However, for oriented samples, important discrepancies are observed, suggesting that the morphology and orientation are important factors in predicting the modulus of these blends. A model which takes into account these factors is proposed and a good fit of the modulus is obtained.
Scale‐up laws in heated tool butt welding of HDPE and PP
Authors: Potente H. , Tappe P. 
Published: December 2004

AbstractIn order to achieve high fatigue strengths in heated‐tool butt welds in plastic pipes used in gas and water supply lines, it is essential that optimum welding parameters be selected. In this paper, the different process phases are described by means of dimensionless characteristic parameters that have been obtained by applying similarity principles to heated‐tool butt welding. On the basis of strength studies conducted on welded Joints, it is shown that the best weld quality is attained when the welding parameters are selected such that identical sheaf deformations result in the joint zones of small and large pipes. Laws for scaling data from small‐pipe to large‐pipe welds are then based on the values of these nondimensional numbers.
Process data acquisition in vibration welding of thermoplastics
Authors: Potente Helmut , Kaiser Harald 
Published: December 2004

AbstractA measuring method is presented for process monitoring and process analysis of linear vibration welding of thermoplastics. The method works by recording and evaluating time‐dependent signals that describe the process—such as the frequency‐dependent signals of the displacement of the two parts being joined, the tangential force in the welding plane—and the nonperiodic signals of the welding process, i.e. the normal force in the welding plane and the melting or joining displacement of the parts being joined. It is possible to determine the energy input into the welding zone as a function of the selected machine parameters and the process sequence over time.
Ultrasonic welding of thermoplastics in the near‐field
Authors: Benatar Avraham , Eswaran Raman V. , Nayar Satinder K. 
Published: December 2004

AbstractUltrasonic welding is one of the most popular techniques for joining thermoplastics because it is fast, economical, and easily automated. In near‐field ultrasonic welding, the distance between the horn and the joint interface is 6 mm or less. This study investigated the near‐field ultrasonic welding of amorphous (acrylonitrile‐butadiene‐styrene and polystyrene) and semicrystalline (polyethylene and polypropylene) polymers. High frequency ultrasonic wave propagation and attenuation measurements were made in order to estimate the dynamic mechanical moduli of the polymers. The estimated moduli were entered into a lumped parameter model in order to predict heating rates and energy dissipation. Experimental results showed that variations in the welding pressure had little effect on energy dissipation or joint strength; Increasing the amplitude of vibration increased the energy dissipation and the weld strength. For the semicrystalline polymers, increasing the weld time improved strength up to weld times greater than 1.5 s, where strength leveled off. For the amorphous polymers, the weld strength increased with Increasing weld time up to times of 0.8 s; for longer weld times, the power required was too high, causing overloading of the welder. Monitoring of the energy dissipation and static displacement or collapse provided valuable information on weld quality.
Interrelationships between selected mechanical properties of individually‐tested polymeric fibers
Authors: Ellison M. S. , Zeronian S. H. , Alger K. W. , Aboul‐Fadl S. M. , Soler T. M. 
Published: December 2004

AbstractAlthough fibers are subject to complex deformations during processing and end use, most research has concentrated on tensile properties. We have extended our studies to include the ultimate torsional properties, i.e., the breaking twist angle (BTA), and the flexural fatigue life of single fibers. We now have sufficient data on diverse fiber types that we may compare their mechanical properties. Thus, in this paper we report the mechanical properties of the different starting, untreated, fibers, tested under fiducial conditions. We then develop and consider some interrelationships between these selected single fiber physical properties.