bluuebunny/crossref_metadata_2025_split huggingface dataset:
The development of surface texture in injection stretch‐blow molded polypropylene
Authors: White S. A. , Doun S. K. 
Published: December 2004

AbstractThe development of surface texture in biaxially deformed polypropylene is examined. Two polypropylenes formed into bottles under similar conditions by the injection stretch‐blow molding process exhibit different levels of clarity. Vertical cracks of light scattering dimensions are found by optical microscopy to be the source of haze. Rheological measurements indicate the resin that develops surface cracking has a much higher extensional viscosity and exhibits a significant increase above the linear case of its extensional stress growth function. Possible mechanisms for the formation of surface texture are discussed.
Thermal and viscoelastic behavior of polyurethane/polyvinylchloride blends
Authors: Lavallée C. , Carmel M. , Utracki L. A. , Szabo J. P. , Keough I. A. , Favis B. D. 
Published: December 2004

AbstractThe potential of melt processing polymer blends to prepare damping materials was investigated. Binary and ternary blends of polyvinylchloride (PVC) with thermoplastic polyurethane elastomers (TPU) were studied. The soft segments of the polyurethanes for the first series were of the ether type and of the ester type for the second series of blends. A series of polymer blends were prepared by mechanical melt mixing and the apparent miscibility was evaluated from the thermal, dielectric, and dynamic mechanical behavior as well as from transmission electron microscopy. Some samples exhibited a single damping peak at low PVC content, indicating miscibility of the blends at the detection scale of the test method. The relationship between the properties and the morphology of the blends was studied.
Extrudate swell of high density polyethylene. Part III: Extrusion blow molding die geometry effects
Authors: Koopmans R. J. 
Published: December 2004

AbstractTwo high density polyethylene resins—801 and 802— are examined with regard to their isothermal, time‐dependent, and nonisothermal swelling properties when emerging from two annular and three diverging dies. The short time swelling characteristics of samples 801 and 802 are very important for these dies, resulting in a lower diameter swell for the latter, independent of the die geometry or flow rate. Output variations have much less impact on the swelling behavior than small changes in the geometry of the die mandrel. Accordingly, shear stress and shear rate parameters alone cannot be used to explain the swelling properties of a HDPE resin in the different die geometries. Straight annular dies induce higher diameter swelling than diverging dies.
Temperature dependence of polyolefin melt rheology
Authors: Mavridis H. , Shroff R. N. 
Published: December 2004

AbstractThe rheology of polymer melts depends strongly on temperature. Quantifying this temperature dependence is very important for fundamental, as well as practical, reasons. The purpose of this paper is to present a unified framework for handling the temperature dependence of rheological data. We considered the case (by far the most common in polymer melts) where all relaxation times (in the context of linear viscoelasticity) have the same temperature dependence (characterized by a “horizontal shift activation energy”) and all relaxation moduli have the same temperature dependence (characterized by a “vertical shift activation energy”). The horizontal and vertical activation energies were extracted from loss tangent vs. frequency and loss tangent vs. complex modulus data, respectively. This is the recommended method of calculation, as it allows independent estimation of the two activation energies (statistically uncorrelated). It was shown theoretically, and demonstrated experimentally, that neglect of the vertical shift leads to a stress (or modulus) dependent activation energy and necessitates different activation energies for the superposition of loss and storage modulus data. The long standing problem of a stress‐dependent activation energy in long chain branched LDPE was identified as originating from the neglect of the vertical shift. The theory was applied successfully to many polyolefin melts, including HDPE, LLDPE, PP, EVOH, LDPE, and EVA. Linear polymers (HDPE, LLDPE, PP) and EVOH do not require a vertical shift, but long chain branched polymers do (LDPE, EVA). Steady‐shear viscosity data can be superimposed using activation energies extracted from dynamic data.
Analysis of stresses arising during the processing of polymeric films on tentering frames
Authors: Jennings Robert M. , Farris Richard J. 
Published: December 2004

AbstractA model based on linear elasticity is presented describing the stresses arising during the processing of polymeric films on tenter frames. The model demonstrates that large in‐plane shear stresses, resulting from gradients in the line, produce anisotropic stresses in the film. The magnitude of the anisotropy is found to vary transversely across the line, becoming isotropic in the center and achieving maximum values at the edges of the line. The principal directions of the stress tend to lie at ±45° to the machine direction but may be altered by machine and transverse drawing by the frame. These results agree with orientation measurements reported in the literature on polyimide films produced on tentering frames.
Development of polymer blend morphology during compounding in a twin‐screw extruder. Part I: Droplet dispersion and coalescence—a review
Authors: Utracki L. A. , Shi Z. H. 
Published: December 2004

AbstractThe theoretical and experimental data on the breakup of droplets are reviewed. Several factors influence development of droplets: flow type and its intensity, viscosity ratio, elasticity of polymers, composition, thermodynamic interactions, time, etc. For Newtonian systems undergoing small, linear deformation, both the viscosity ratio and the capillary number control deformability of drops. On the other hand, the breakup process can be described by the dimensionless breakup time and the critical capillary number. Drops are more efficiently broken in elongational flow than in shear, especially when the viscosity ratio λ ⩾ 3. The drop deformation and breakup seems to be more difficult in viscoelastic systems than in Newtonian ones. There is no theory able to describe the deformability of viscoelastic droplet suspended in a viscoelastic or even Newtonian medium. The effect of droplets coalescence on the final morphology ought to be considered, even at low concentration of the dispersed phase, ϕd ⩾ 0.005. Several drop breakup and coalescence theories were briefly reviewed. However, they are of little direct use for quantitative prediction of the polymer blend morphology during compounding in a twin‐screw extruder. Their value is limited to serving as general guides to the process modeling.
Development of polymer blend morphology during compounding in a twin‐screw extruder. Part II: Theoretical derivations
Authors: Shi Z. H. , Utracki L. A. 
Published: December 2004

AbstractIn Part II of the work, the intermeshing twin‐screw extruder is briefly described and the theoretical procedures used to model its operation are summarized. Based on the microrheological considerations discussed in Part I, a predictive procedure of the morphology evolution during compounding of two immiscible polymers is proposed. In this first generation model, only the shear flow effects are considered. Furthermore, to avoid complications due to coalescence a low concentration of the dispersed phase was assumed. In the procedure, two drop breakup mechanisms are discussed. The first assumes that the drops do not break under flow while the second postulates that breakup occurs under flow. Two dispersion mechanisms are considered, the first postulating continuously increasing polydispersity of drop size and the second postulating that drop polydispersity is inversely proportional to deformation strain. The influence of the screw configuration and operating conditions on blend morphology evolution is studied. It is expected that the computed drop size distribution provides limiting values for the experimental data. Dependency of predicted morphology on operating conditions is also investigated. Increasing screw rotating speed (resulting in increasing energy consumption) and decreasing throughput (resulting in decreasing productivity) lead to prediction of finer drop size. In practice, therefore, a compromise would be required. The proposed procedure is limited to melt flow (excluding the die region) within the region of large capillary parameter values, k > 4kcrit.
Damage and the nonlinear viscoelastic response of glassy polycarbonate and LaRC‐TPI
Authors: Crook R. A. 
Published: December 2004

AbstractIn the bulk, the nonlinear viscoelastic response of glassy polymers is due to the irreversible work done on the body by the surroundings. The source of the irreversibility is plastic flow of material near distributed shear bands or microcracks in the polymer. Shear bands and microcracks also form new traction free boundaries in the body. The presence of these new boundaries diminish the load bearing capacity of the polymer. These changes in polymer lattice structure are a mechanism that promotes the release of stored strain energy. If the release of stored strain energy is stress controlled, then at sufficiently high levels of stress to cause a permanent structural arrangement of the polymer chains, polycarbonate and LaRC‐TPI behave as nonlinear viscoelastic materials. If the current stress is less than the maximum stress the polymer has experienced, then the current energy release rate for the propagation of shear bands, crazes, etc., is less than the critical energy release rate. In this instance, damage production is a constant and the material can be modeled using linear viscoelasticity. It will be shown that the stress‐induced nonlinear shift factors are a measure of the rate of damage production in glassy polycarbonate.
On‐line prediction of final part dimensions in blow molding: A neural network computing approach
Authors: Diraddo R. W. , Garcia‐Rejon A. 
Published: December 2004

AbstractControl over final part thickness distributions in extrusion blow molding would be very useful in resin optimization. An on‐line measurement is essential for process monitoring and control of the part dimensions. Excessive resin usage results in material waste and increased cycle times because of increased cooling requirements. An inadequate thickness results in decreased mechanical strength, especially in regions along the part where large blow ratios or complex geometries exist. Neural networks are investigated as a method for the on‐line prediction of the final part distribution from the parison dimensions. The purpose of this work is to demonstrate the feasibility, for preliminary use, of neural networks for this application. The network inputs include the initial parison thickness and tempera‐ture profiles, the bottle mold geometry and a rheological parameter representative of the material. Varying blow‐up ratios are obtained from the bottle mold geome‐try. The network accesses data from a pool of eighty data sets for the training sequence. The data sets are broadly distributed with regard to the operating conditions, so as to give the network a wide range of applicability. The simulations are performed on data sets not present in the access pool used for training.
The effect of surface roughness and crystallinity on the light scattering of polyethylene tubular blown films
Authors: Larena Alicia , Pinto Gabriel 
Published: December 2004

AbstractAn experimental study of the effect of surface roughness and crystallinity on the light scattering of polyethylene tubular blown films is reported. Several films were prepared by varying the raw polyethylenes and the extrusion temperature. Other processing variables were maintained constant. We have made a statistical analysis of data and we have obtained multiple regressions between light scattering for a given wavelength of incident light and a given film thickness (30 μm, 50 μm, and 70 μm) and the independent variables average surface roughness and degree of crystallinity. It was demonstrated that, for the polymeric films studied, the surface texture evaluates better than crystallinity the variation of light scattering, but crystallinity has also some importance.
Effect of drawing on structure and properties of a liquid crystalline polymer and polycarbonate in‐situ composite
Authors: Lin Qinghuang , Jho Jaeyoung , Yee Albert F. 
Published: December 2004

AbstractFibers (strands) with various draw ratios were spun from the liquid crystalline state of a pure aromatic liquid crystalline copoly(ester amide) and the melts of its blend with polycarbonate. Scanning electron microscopy (SEM), wide angle X‐ray scattering (WAXS), and differential scanning calorimetry (DSC) were employed to investigate the structure and properties of the resulting fibers. Mechanical properties of the fibers were also evaluated. It was found that both the crystallite size and heat of fusion of the liquid crystalline polymer (LCP) increase steadily with draw ratio. However, the crystal‐nematic transition temperature of the LCP is virtually unaffected by drawing. Moreover, heat of fusion of LCP is much smaller than that of isotropic condensation polymers despite the presence of very sharp diffraction peaks in WAXS measurements. These results are ascribed to the (semi)rigid rod nature of the LCP chains and the persistence of an ordered structure in the LCP melt, i.e., entropy effect. It was further observed that tensile modulus and tensile strength along fiber axis rise with draw ratio for the composite fibers. The elastic modulus of the composite fibers were found to be as high as 19 GPa and tensile strength reached 146 MPa with draw ratios below 40 and an LCP content of 30 wt%. Compared with the thermoplastic matrix, the elastic modulus and tensile strength of the in‐situ composite have increased by 7.3 times and 1.4 times, respectively, with the addition of only 30 wt% LCP. This improvement in mechanical properties is attributed to fibrillation of the LCP phase in the blend and the increasing orientation of the LCP chains along the fiber axis during drawing.
Modification and compatibilization of nylon 6 with functionalized styrenic block copolymers
Authors: Modic M. J. , Pottick L. A. 
Published: December 2004

AbstractMuch work in recent years had focused on the improvements of the impact properties of engineering thermoplastics by the addition of a low modulus modifier that contains polar moieties as a result of polymerization or that has been modified to contain polar moieties as a result of various grafting techniques. Styrenic block copolymers (styrene‐ethylene/butylene‐styrene) functionalized with maleic anhydride have proved useful as impact modifiers and compatibilizers in blends with engineering thermoplastics. This paper focuses on the use of these functionalized elastomers to modify nylon 6. In such compositions, a nylon material with unique mechanical performance may be achieved using the functionalized elastomer either alone or in combination with an unfunctionalized styrenic block copolymer. The optimization of performance in these rubber toughened polyamide blends using various types of styrenic block copolymers is discussed. The morphology as it pertains to performance is also reviewed. The information contained herein may prove useful in obtaining a better understanding of the mechanisms of compatibilization and modification of nylon 6 systems.
Suspension, dispersion, and interfacial polycondensation: A methodological survey
Authors: Arshady Reza , George Maurice H. 
Published: December 2004

AbstractThis review presents a general picture of suspension, dispersion, and interfacial polycondensation processes employed for the preparation of beaded resins, dry powders, and high solid dispersions. The polymer systems covered include polyamides, polyesters, polycarbonates, polyurethanes, and phenol‐formaldehyde and urea‐formaldehyde resins. Basic features of heterogeneous polycondensation processes are outlined, and different mechanisms of particle formation in suspension, dispersion, and interfacial polycondensation are discussed. Effects of manufacturing parameters such as feed ratio, droplet/particle stabilizer, and stirrer speed on product characteristics are also briefly covered.
Semi‐interpenetrating polymer networks composed of poly(ethylene terephthalate) and castor oil: Synthesis, structure, and properties
Authors: Barrett L. W. , Sperling L. H. 
Published: December 2004

AbstractSemi‐interpenetrating networks have been produced from castor oil and poly(ethylene terephthalate) (PET). Bond interchange between PET and castor oil plays a major role in the development of initial miscibility, also affecting morphology and chemical structure. Microheterogeneous morphology is developed for materials of intermediate composition, which have much greater toughness than the polymers from which they were made.
Numerical simulation of profile extrusion dies without flow separation
Authors: Hurez P. , Tanguy P. A. , Blouin D. 
Published: December 2004

AbstractLubrication theory has been applied to solve flow problems in profile extrusion dies without flow separations, for Newtonian and power law type fluids. The method is based on velocity calculation within cross sections perpendicular to the flow. Pressure drop can also be obtained from a macroscopic balance, if the flow rate is known. Comparison of pressure drops in 2‐D and 3‐D geometries has been made with numerical simulation obtained by a finite element method. Results show a good accuracy of the proposed method.
The application of reactive processing to stampable sheet of toughness improved unsaturated polyester
Authors: Sakai Tadamoto , Nakamura Kazuyuki , Inoue Shigeki 
Published: December 2004

AbstractUsing twin screw extrusion and stampable sheeting processes, we have investigated the application of reactive processing technology to fiber‐reinforced stampable sheet made of an unsaturated polyester (UP) alloy with high toughness. As a result, we obtained a stampable sheet composed of a UP/nitrile butadiene rubber (NBR) polymer alloy matrix and glass fiber mats with physical properties equivalent to those of polypropylene (PP) stampable sheet, and moreover, with higher heat resistance than PP.
The laminate‐bending process for long fiber‐reinforced plastics
Authors: Machida Terufumi , Schott Nick R. 
Published: December 2004

AbstractIn order to form long fiber‐reinforced plastic sheets into angled parts, a new process called the Laminate‐Bending Process was recently developed. The process consists of preforming a prepreg into semi‐cured stable shapes having various sharp bending radii, followed by laminating the preforms into a fully cured thick angle product having high strength and rigidity. A sharp 90°V‐angled product of five lay‐ups of preform was test fabricated under various preforming and laminating conditions by using a continuous glass fiber reinforced epoxy resin, and it was confirmed to be excellent in delamination resistance and specific strength. Also, the process is quite practical in productivity, handling, and applicability to other advanced composite materials, and it can expand the use of such brittle materials for wider applications.
Fusion simulation of electrofusion polyethylene joints for gas distribution
Authors: Nakashiba Akio , Nishimura Hiroyuki , Inoue Fumio , Nakagawa Tomokazu , Homma Katsuhiko , Nakazato Hideo 
Published: December 2004

AbstractFusion simulation is one of the key techniques used in designing and producing electrofusion joints for gas distribution and in evaluating fusion joint integrity. This paper describes the results of numerical simulation of the thermal fusion process, using the finite element method. A nonlinear heat transfer computer program was used to obtain the temperature profile of an electrofusion joint at fusion. It was found that the temperature experimentally measured at the fusion interface by insertion of a thermocouple agreed with the temperature computed by fusion simulation. In addition, as both the temperature at the fusion interface and the resin temperature close to the wire corresponding to the mechanical strength of the fusion part were measured, it was confirmed that the proper heating conditions for each joint could be determined based on the results of the fusion simulation.
Effect of molecular weight on spherulite growth rate of poly(ethylene terephthalate) via real‐time small angle light scattering
Authors: Tant Martin R. , Culberson Wayne T. 
Published: December 2004

AbstractThe effect of molecular weight on the spherulite growth rate of poly(ethylene terephthalate) (PET) has been determined using a real‐time small angle light scattering (RTSALS) device equipped with a two‐dimensional position‐sensitive detector. This detector, the design of which was previously reported, incorporates a CCD camera, a personal computer, and an imaging board as the major hardware components. The device performs real‐time analysis of the light scattering pattern and calculates the average spherulite radius as a function of time during the crystallization experiment. Growth rate data were obtained for PET having number‐average molecular weights of 18,000, 24,700, and 33,100. Samples were crystallized isothermally following a temperature jump from the glass at room temperature to the desired crystallization temperature, which ranged from 130 to 200°C. Both the temperature and molecular weight dependence were found to be well described by the Hoffman equation. The temperature dependence agrees well with that found by previous workers, but the molecular weight dependence is somewhat different.
Prepreg processing science and engineering
Authors: Ahn K. J. , Seferis James C. 
Published: December 2004

AbstractResin flow and fiber spreading during the prepregging process were investigated experimentally using a scale‐down version of a commercial hot‐melt prepregger with bismaleimides and carbon fibers as model systems. Specifically, several dimensionless parameters such as the Prepreg Flow Number, fractional resin uptake, resin distribution function, fractional width change, and prepregging efficiency were defined to characterize the prepregging process as well as the quality of the prepreg. Fiber spreading during the prepregging process was observed to be a viscoelastic phenomenon depending on the impregnation temperature. For resin impregnation into collimated fiber tows, all the experimental data points obtained at different operating conditions were superimposed onto a single line showing a temperature‐pressure‐velocity superposition for the prepregging process as predicted by the definition of the Prepreg Flow Number (PFN). Finally, three fundamental steps of the prepregging process were identified and confirmed with cross‐sectional micrographs of unaged prepregs produced at different temperatures.
Friction and its effect on the mechanical‐ to‐thermal energy conversion during extrusion of poly(vinylidene chloride)
Authors: Kirkpatrick Donald E. , Hyun Kun S. , Chung Chan I. 
Published: December 2004

AbstractSolid state friction reduction has been found to be an effective method for extrusion stabilization of a high coefficient of friction (COF) thermally sensitive polymer. A poly(vinylidenechloride) copolymer (PVDC) was studied alone and blended with various polyolefins to change its frictional behavior. COF of the polymer rubbing on a metal surface was measured under conditions typical of an extrusion process. These results correlated well with the measured mechanical energy consumed during extrusion. Of the polyolefins studied, high and low density polyethylene were found to be very effective for lowering friction and improving extrusion performance of the PVDC. Polypropylene was found to be much less effective. Interface temperature where melting occurs due to frictionally generated heat has been experimentally shown to be a function of COF and the bulk metal temperature.