bluuebunny/crossref_metadata_2025_split huggingface dataset:
Temperature dependence of the melt viscosity of epoxy resins
Authors: Utracki L. A. , Ghijsels A. 
Published: April 2003

AbstractThe zero‐shear viscosity η0 of five epoxy resins were analyzed on the basis of the free volume concept. The experimental data, spanning at least six decades in viscosity, were linearized by means of a viscosity–temperature relation η0 = η0(T), derived by Utracki a few years earlier. The linearization enables the following conclusions to be drawn: (1) There is no liquid–liquid transition within the investigated temperature range: T/Tg = 1.05–1.38 (Tg is the glass transition temperature); (2) the derived equation can be used to calculate η0 vs. T dependence; and (3) the equation can be generalized to permit prediction of the η0 = η0(T) dependence of any epoxy resins (of the type studied here) on the basis of a single point determination of viscosity and Tg of the sample.
Infrared radiation in the processing of plastics: Precise adjustment–the key to productivity
Authors: Esser K. , Haberstroh E. , Hüsgen U. , Weinand D. 
Published: April 2003

AbstractInfrared radiation plays a large role in many areas of plastics processing, whether in the heating of thermoplastics for purposes of subsequent forming or in noncontact temperature measurement. This paper sets out to deepen our understanding of the plastics‐specific problem associated with infrared radiation. First of all, a brief outline is given of the necessary fundamental physical principles, before going to to discuss measurement results in terms of the radiation‐related properties of plastics. The influence of pigmentation and crystalline structures is investigated, together with the temperature dependence of absorption behavior. Linking up the radiator characteristics and absorption properties of plastics, a physical model is then presented which can be used to calculate energy efficiency and temperature homogeneity in the heating of plates. The results are presented in diagrams. In addition, the special problems of infrared heating in stretch blow molding are examined. Here, we attempt to attain a high level of penetration into the thick‐walled parisons by means of short‐wave radiation and thereby guarantee uniform and rapid heating. A program for establishing the intensity distribution of radiation on a semifinished product has been developed for geometerical configurations generally found in thermoforming machines and this will run on a personal computer. It will allow the optimization of uniform or deliberately nonuniform temperature distributions over the surface. If the stretching process is to be selectively influenced, it is essential to have knowledge not only of the temperature distribution in the semifinished part but also of the stretching behavior of the material. A highly informative testing procedure was developed to this end, which reveals the suitability of the material in question for a stretching process. A further section covers the infrared temperature measurement frequently applied in plastics processing for process analysis, monitoring, and control. The different types of measuring devices and their advantuges and drawbacks are discussed here. An analysis is also conducted of disturbance variables and possible means of correction are indicated.
Damage accumulation and friction of fibrous composites
Authors: Lhymn C. , Park I. K. 
Published: April 2003

AbstractA theory of friction has been constructed from the bond reputed concept incorporating the physics of damage accumulation and adhesion. The theory specifically emphasizes the role of crack propagation as a mechanism of energy dissipation. The model thus constructed can explain the effect of roughness, fiber orientation on friction. The model has been further extended to consider the effect of normal load on friction as well as the sliding velocity on friction. The experimental data appear to support the proposed equations.
An improved theory of metering in an intermeshing corotating twin‐screw extruder
Authors: Szydlowski Witold , White James L. 
Published: April 2003

AbstractAn improved analysis of flow in the screw elements of an intermeshing corotating twin screw extruder is presented. The new theory based on an isothermal Newtonian fluid model allows explicit consideration of the geometry of the intermeshing region. Flow rates are computed as a function of the pressure gradients and screw speeds. Both left‐handed and right‐handed screws are considered.
Nonisothermal pressurization of variable viscosity newtonian fluids between two parallel plates
Authors: Sun Tzu‐Hsiung 
Published: April 2003

AbstractNonisothermal flow of a variable‐viscosity Newtonian fluid between parallel plates is analyzed to study the effect of heat transfer and viscosity effect on the pumping capacity of the device. Results indicate that the pumping capacity is greatly reduced in the entrance regions of a pumping device such as a single screw extruder or calender. This reduction in pumping capacity can cause sever surging effects in the device, for the pumping capacity is enhanced by the thermal effect in the exit region.
Twin screw extruders; development of technology and analysis of flow
Authors: White James L. , Szydlowski Witold , Min Kyonsuku , Kim Myung‐Hwan 
Published: April 2003

AbstractA critical evaluation of the technological development and studies of mechanisms of flow in twin screw extruders is presented. We include (i) intermeshing counter‐rotating twin screw machines, (ii) tangential counter‐rotating twin screw extruders, and (iii) intermeshing corotating twin screw machines.
Effect of recycle on properties and profits: Algorithms
Authors: Throne James L. 
Published: April 2003

AbstractIn many plastics processes, nonvirgin materials make up relatively small percentages of materials added to the main processing stream. In thermoforming, however, as much as half the material that passes through the extrusion and thermoforming process chain is “nonproduct” web. Economics usually dictate that this material must be reprocessed. Materials that experience high levels of shear and/or temperature usually exhibit measurable and significant property loss. This means that the mixture of materials fed to the process has properties some‐what less than those of the virgin resin. This paper presents algorithms for determining final product properties, given single‐pass property loss and fraction of recycle in the resin mixture going to the process. The following cases are considered:

Linear, where the single‐pass property loss is directly proportional to the mixture property prior to processing. This was first worked out by Smoluk for tensile strengths
Power‐law, where the single‐pass property loss is proportional to the mixture property to a power. Impact strength is an example
Offset, where the single‐pass property is equal to the mixture property minus a fixed amount. Fire retardancy seems to be an example of this
Logarithmic, where the law of mixtures is logarithmic. Viscosity and intrinsic viscosity (molecular weight) are examples here

For cases 1, 2, and 4, the algorithm yields a closed solution for steady‐state processes. The offset case yields a nested series that converges in about 20 steps. In addition, if a value can be placed on material property loss (either through higher product reject rates or higher virgin material costs), a “profit” algorithm can be created to determine the actual processing costs. From this, scenarios for reuse of regrind and/or off‐spec materials can be created. An example of such an algorithm is given.
Variable‐viscosity flow in heated and cooled channels with internal viscous dissipation
Authors: Sun Tzu‐Hsiung 
Published: April 2003

AbstractA similarity solution is given to a very viscous Newtonian fluidflowing in a channel which is suddenly heated or cooled. The viscosity is assumed purely an exponential function of temperature and heat generation is very large. The asymtoptic approximation is that the downstream viscosity at the channel wall differs by an order of magnitude from that in the upstream flow. This solution can be used to check results of numerical simulation in the injection of either a thermoplastic or a thermoset resin into a cooled or heated mold, respectively.
Pressure buildup in the feed zone of a single screw extruder—the effect of density compressibility
Authors: Sun Tzu‐Hsiung 
Published: April 2003

AbstractThe effect of density compressibility of granular polymeric solids on the pressure development inside the feed zone of a single screw extruder was calculated. Results indicate that, for a given flow rate, density compressibility enhances pressure rise inside the extruder, remedying the under estimation of previous theory. A substantial rise in pressure buildup may result for compressibility above a certain level. This may explain observed surging during the processing of low bulk density materials.
Production, properties, and application of polyurethane RRIM
Authors: Braun H.‐J. , Eyerer P. , Frank U. , Hüttner M. , Ludwig H.‐J. , Wurster T. 
Published: April 2003

AbstractThe production of automotive exterior body panels in the PUR–RRIM process is a comparatively new technology that provides a great potential for further improvements and makes it possible to produce plastic components for the automotive industry that, at relatively thin wall thicknesses, meet maximum requirements in regard to

part geometry
dimensional stability
the high industrial standards valid in the automotive industry
surface quality (avoidance of sink marks, pores, etc.)
durable fastening

For a better acceptance of RRIM moldings, cost reductions in the production process are necessary which, in turn, require noticeable progress in the material and process development. Due to the improvements made in the field of both raw materials and production units, the PUR–RRIM process has, in the last few years, become interesting also for high‐volume production. A handicap in this connection is that the development of the RRIM process is, to a large extent, based on the practical experience of a few experts. For its use in high‐volume production it is, however, inevitable to have at hand through scientific data on material, design, process and resulting correlations. It is the objective of the Institute for Polymer Testing and Polymer Science in Stuttgart to help establish these data and, through close contacts to the industry, make them usable in practice.
A 3‐D finite eiement model for polymer melt flow
Authors: Tanguy Philippe A. , Fortin André , Bertrand François 
Published: April 2003

AbstractA finite element investigation of 3‐dimensional polymer melt flows in a sudden contraction is presented. In continuity with the 2‐dimensional work of the authors,2 the present study uses the augmented Lagrangian method to cope with the nonlinear rheological behavior of melts. Two kinds of situation are considered: the flow of a nonisothermal melt obeying the Carreau A model of viscosity; the isothermal flow of a Bingham fluid. In the first situation, our interest is focused on the influence of the shear‐thinning nature of the melt onto the 3‐dimensional temperature pattern inside the contraction. In particular, the mechanism of creation of hot spots is shown in the small channel. In the second situation, the influence of the yield stress on the flow pattern is studied. It is shown in particular that a slow motion secondary flow (quasistagnant region) is created before the contraction for large values of the yield stress.
Polystyrene and styrene copolymers. I. Their manufacture and application
Authors: Ku Ping L. 
Published: April 2003

AbstractThe manufacturing processes for polystyrene (PS) and its copolymers, including styrene–acrylonitrile (SAN), high impact polystyrene (HIPS), acrylonitrile–butadiene–styrene (ABS), styrene–butadiene latex (SBR for coating), styrene–butadiene block copolymers (SBS), and styrene–acrylate copolymers (SMMA), are discussed and illustrated. The synthetic methods for such products are bulk, emulsion, suspension, and free radical polymerization techniques, all either in batch or in continuous operations. By comparison, it was found that continuous bulk is the most economical process among the above‐mentioned polymerization methods. However, the suspension method is still the only way to make expandable polystyrene beads (EPS). Some ionic polymerization techniques for making homo‐ and copolymers are also discussed. Types of styrene‐containing polymers, like all other resins, are classified according to their property distribution. Some are uniquely outstanding and others have a balance of properties, which, in turn, are functions of the molecular weight and molecular weight distribution (MWD), the nature of the components, and the methods and conditions of polymerization. Therefore, each product can be produced in many grades, for a variety of applications.
Multilayer sheet coextrusion: Analysis and design
Authors: Mitsoulis Evan 
Published: April 2003

AbstractA numerical simulation of multilayer coextrusion flows has been undertaken for polymer melts used in producing multilayered plastic sheets. Viscosity data and other material properties are used for typical melts and adhesives applied in coextrusion. Industrial designs have been employed for feedblock geometry and multimanifold vane flat dies. The analysis is based on the lubrication approximation theory (LAT), which treats the flow locally as fully developed. A Newton‐Raphson iterative scheme is employed to solve the equations for a pressure‐driven flow of N number of layers (N ⩽ 11). For a given total flow rate and flow rate ratios (or correspondingly total sheet thickness and individual layer thicknesses), the solution provides the interface locations and individual pressure drops that each extruder has to supply. The shear stresses at the channel walls are checked as a criterion for proper design. The die design or melt combinations are altered to produce smooth shear stresses with no humps or discontinuities at the points of confluence. A Adiabatic temperature rises are also computed based on the pressure drops in the system. Such an analysis provides a quick qualitative as well as quantitative insight into the proper design and melt combinations for multilayer sheet coextrusion.
Tribological properties of silicone‐impregnated polymer composites—two‐body abrasion
Authors: Lhymn Yoon , Lhymn C. 
Published: April 2003

AbstractThe friction and wear behavior of silicone‐impregnated fiber‐reinforced thermoplastics has been investigated as a function of normal load in air, water, and oil lubricants using a two‐body abrasion tester. The measured tribological data have been phenomenologically explained by a wear/friction equation derived from the concepts of crack propagation and wear failure mode.
Viscoelastic properties of structural silicone rubber sealants
Authors: Tock Richard W. , Dinivahi M. V. R. N. , Chew Choon Hoi 
Published: April 2003

AbstractThe behavior of silicone rubber materials subjected to uniaxial stress fields cannot be predicted by classical mechanical theory which is based on linear stress–strain relationships. Nor do theories based on “ideal elastomer” concepts work well when extensions exceed 30%. For these reasons, there are few design specifications related to the use of silicone rubber sealants for structural applications. This paper presents a theoretical approach used to predict the behavior of silicone rubber under uniaxial stress fields. The model is based on the concept of the classical Maxwell treatment of viscoelasticity and stress relaxation behavior. However, the Hookean spring component of the Maxwell element is replaced with an ideal elastomer component. With this substitution, the new model permits the crosslink density of the silicone elastomer to be estimated from test data and allows a stress level to be predicted as a complex function of extension, crosslink density, absolute temperature, and relaxation time. Simple uniaxial tensile tests were performed on two commercial silicone rubber sealants. Their experimental behavior was compared to the predicted performance based on the new viscoelastic model. Agreement was found to be quite good. It is hoped that the model, therefore, will help in the basic understanding of structural sealant behavior and perhaps lead to better design specifications for structural glazing.
Wide angle X‐ray diffraction investigations of orientation of chopped fibers in fabricated thermoplastic parts
Authors: Lim Soonho , Kikutani Takeshi , White James L. , Kyu Thein 
Published: April 2003

AbstractA method of determining fiber orientation in composites using wide angle X‐ray diffraction (WAXD) is described. This approach is based upon examining the alignment of the highly oriented crystalline fibers. X‐ray studies were carried out using Kevlar [poly(p‐phenylene terephthalamide) (PPTA)] fibers suspended at a 0.31 volume fraction loading in a polycarbonate matrix. A pole figure device was used to determine the orientation distribution and average orientation factor of the PPTA crystallographic chain axes relative to reference axes located in the test specimen. We prepared ideally oriented uniaxial and bioaxial composites as reference specimens using a compression molding machine. The fiber orientations in capillary extrudates, slit die extrudates, cold rolled sheets, and injection‐molded specimens were examined by WAXD. The capillary extrudates showed uniaxial orientation but the slit die extrudates and cold rolled sheets exhibited biaxial orientation. Injection‐molded specimens contained complex states of fiber orientation.
Dynamic and steady shear rheological properties of a polydisperse polystyrene
Authors: Huang Jan‐Chan , Dharia Amitkumar N. 
Published: April 2003

AbstractNon‐Newtonian viscosity, storage, and loss moduli of a polydisperse polystyrene are measured. Molecular weight distribution of the polystyrene is measured by gel permeation chromatography. The rheological model of Carreau is modified with molecular‐weight‐dependent relaxation times to obtain rheological functions of the polydisperse polystyrene. It is found that five parameters in the model can satisfactorily describe the rheological functions measured.
Unsteady flow of rubber compounds at injection molding conditions
Authors: Isayev A. I. , Huang Yeong‐Hua 
Published: April 2003

AbstractAn automated rheometer is developed for an evaluation of the processability of rubber compounds at injection molding conditions. The rheometer utilizes a screw injection molding machine in order to push rubber compounds through a thermostated slit die at controlled flow rates. Three pressure transducers are flush‐mounted along the die length and a displacement transducer is installed to measure the screw motion. Signals generated by the pressure and displacement transducers and thermocouple are supplied to an A/D converted and the IBM PC/AT computer. Unsteady character of flow of rubber compounds is observed. The obtained data are compared with predictions from modeling of flow, using the viscoelastic plastic constitutive equation.
Characterization of rotational molding grade polyethylene powders
Authors: Throne J. L. , Sohn M.‐S. 
Published: April 2003

AbstractRotational molding grade polyethylene powders are classified according to sieve size, to typically–35 mesh, and by flowability, usually determined by pouring freeflowing powder from a funnel onto a fixed base cone. In the latter case, the static angle of repose is then measured. This study concentrates on general methods of characterizing powders and relating these methods of flowability of five selected commercial rotational molding grade polyethylene powders. The techniques described in this study include methods for measuring particle size distribution, particle shape characteristics, static and dynamic angles of repose, powder shear strength, and angle of internal friction. All powders examined had similar particle size distribution profiles, with distributions skewed to the coarser, −35 mesh size particles. The static and dynamic angles of repose were quite similar and the latter were essentially independent of the volume fraction of powder in the rotating cylinder and of the speed of rotation of the cylinder. All powders had shape parameters–elongational ratio, chunkiness, circularity, and roundness–that were essentially similar and independent of particle size, and the compressibilities of the bulk powders were not strongly dependent on powder bed height.
Structure–property considerations for rotationally molded polyethylenes
Authors: Throne J. L. , Sohn M.‐S. 
Published: April 2003

AbstractIn a companion study,1 it was found that five commercially available rotational molding grade polyethylenes had similar particle size distribution profiles and dynamic angles of repose. There were measurable differences in their general particle shapes. These powders were rotationally molded in an axisymmetric cylinder mold using time–temperature molding cycles recommended for these materials. Wall sections were then cut from the molded cylinders and tensile strengths, Young's moduli, elongations at break, and Izod impact strengths were measured. The resins were then injection molded and similar mechanical tests were performed. The rotationally molded samples exhibited porosity, the level of which depended strongly on the residence time in the isothermal oven. The rotationally molded samples showed greater strengths and moduli, but lower elongations at break and impact strengths. The rotationally molded samples also showed higher crystallinity levels and substantially larger spherulite dimensions. These observations support the mechanical property data.
Peroxide crosslinking of LLDPE during reactive extrusion
Authors: Tang Y. , Tzoganakis C. , Hamielec A. E. , Vlachopoulos J. 
Published: April 2003

AbstractAn experimental study of the free‐radical‐induced crosslinking of linear‐low‐density polyethylene (LLDPE) in the melt phase has been carried out. Experiments have been performed both in a single‐screw plasticating extruder and in an extrusion plastometer using a peroxide as the free‐radical source. Concentration of the peroxide was in the range of 0.005–0.08 wt % for rheological investigation and was extended to 5 wt % for gel content examination. Results in the form of melt flow index (MFI) values, viscosity curves, extrudate swell, and gel content of the produced resins are presented here.