bluuebunny/crossref_metadata_2025_split huggingface dataset:
Biaxial orientation of poly (ethylene terephthalate). Part II: The strain–hardening parameter
Authors: Chandran Prashant , Jabarin Saleh 
Published: April 2003

AbstractResults of a study of the orientation characteristics of extruded poly(ethylene terephthalate) (PET) (Homopolymer) sheets are discussed with respect to stretching condition. PET exhibits strain‐induced crystallization upon being stretched to large extension ratios. This may lead to strain‐hardening, which is accompanied by an upswing in the stress–strain curve recorded during the process of extension. A parameter pertaining to the extension ratio, at which the onset of strain‐hardening occurs during stretching of the specimen, is defined. This is called the strain‐hardening parameter (SHP). The dependence of the SHP on the mode of stretching, the temperature of stretching, the strain rate, and the limiting extension ratio in the first stretch direction, are studied. It is seen that the SHP in both simultaneous and sequential modes decreases with increasing strain rate and the limiting extension ratio in the first stretch direction, while it increases with increasing temperature of stretching. For specimens stretched in the simultaneous mode at 90°C, SHP versus extension rate shows a minimum. This could be due to viscous dissipation at high rates of extension. Also studied is the relationship of strain‐hardening and the SHP with strain‐induced crystallization. It is seen that for specimens stretched in the uniaxial constrained mode, the rapid increase in properties with extension occurs much before the upswing in the stress–strain curve. The upswing occurs at the extension ratio at which the increase in properties once again becomes gradual. This means that the upswing in the stress–strain curve indicates significant completion of strain‐induced crystallization and the establishment of structural order within the specimen. © 1993 John Wiley & Sons, Inc.
Current trends in cae: Simulations of latest innovations in injection molding
Authors: Himasekhar K. , Turng L. S. , Wang V. W. , Chiang H. H. , Wang K. K. 
Published: April 2003

AbstractThe advent of CAE (computer‐aided engineering) technology for injection molding and related processes is having a rapidly growing impact on the molding industry. Proper use of this technology has enhanced engineers' capability in handling all aspects of the molding process and has been proven to benefit both productivity and product quality. However, while CAE can serve as a powerful tool to help engineers make rational engineering decisions, it is by no means a panacea for solving all molding problems. The viability of CAE packages depends heavily not only on the scientific principles and numerical methods used for developing the software, but also on the reliability of the input data such as material properties and process conditions. This article discusses the state‐of‐the‐art of the technology with an emphasis on simulations of latest innovations in injection molding. A three‐layer approach that systematically integrates and efficiently utilizes various CAE tools to solve design problems at different levels of sophistication is also presented. © 1993 by John Wiley & Sons, Inc.
Failure prediction of fiber reinforced laminates under hygrothermal and mechanical in‐plane loads
Authors: Philippidis T. P. , Theocaris Pericles S. 
Published: April 2003

AbstractA theoretical investigation using the failure tensor polynomial criterion was carried out to study the effect of off‐diagonal failure tensor components on the limit behavior of symmetric fiber reinforced laminates under both mechanical and hygrothermal loading. In spite of obvious similarities in the mathematical expression of numerous failure criteria based on the tensor polynomial theory, their predictions may be substantially different depending on loading conditions and on the choice of stress‐interaction terms. Although these predictions for unidirectional fiber reinforced laminae under biaxial loading do not exhibit remarkable differences, this is not the case for multidirectional laminates. Comparison of theoretical predictions with experimental data from in‐plane loaded cross‐ply Graphite/Epoxy laminates proved the reliability of the so‐called generalized elliptic paraboloid failure surface criterion, assuming the existence of a safe triaxial loading path which may depend on the anisotropy of the medium and its suitability for use in structural design applications. © 1993 John Wiley & Sons, Inc.
Numerical analysis of the resin transfer molding process by the finite element method
Authors: Trochu F. , Gauvin R. , Gao D.‐M. 
Published: April 2003

AbstractAs large components of fiber reinforced composite materials are being more frequently produced by Resin Transfer Molding (RTM), a computer simulation of the injection process can help the mold designer to accomplish three important tasks: (1) to ensure a complete filling of the mold through adequate positioning of the injection ports and of the air vents; (2) to verify the integrity of the mold during the filling process through knowledge of the pressure distribution; and (3) to optimize the production cycle using information about the filling time. The resin impregnation is usually modeled as a flow through a porous medium. It is governed by Darcy's law, which states that the flow rate is proportional to the pressure gradient. In our model, Darcy equation is solved at each time step inside the saturated part of the mold using nonconforming finite elements. This method was chosen because the approximated flow rates, contrary to conforming finite elements, satisfy locally the important physical condition of resin conservation across inter‐element boundaries. This permits simplification of the numerical procedure. It is no longer necessary to resort to a control volume approach to move the flow front forward. The resin pressure distribution and the resin front positions are obtained by the computer simulation and calculated results for selected mold geometries are compared with experimental observations. Molds with inserts, multiple injection ports, and the case of anisotropic preforms can be analyzed by the computer program. © 1993 by John Wiley & Sons, Inc.
Theoretical modeling of dispersive melting mechanism of polymers in an extruder
Authors: Huang Han‐Xiong , Peng Yu‐Cheng 
Published: April 2003

AbstractStudies on the melting in a single‐screw extruder have mainly concentrated on the Maddock melting mechanism. The dispersive melting mechanism, named by us, is of great practical utility. A six‐block physical model is first proposed for the dispersive melting mechanism in the present study. Then nonisothermal non‐Newtonian mathematical models for the dispersive and Maddock melting mechanisms are developed. It has been demonstrated that the dispersive melting model has a number of advantages over the Maddock melting model: the mechanical power consumption can be decreased; the polymer temperature profile is more uniform and its average temperature is lower. Furthermore, melting can be accelerated and hence the total melting length shortened. © 1993 by John Wiley & Sons, Inc.
Development of an expert system for injection molding operations
Authors: Kameoka Seiji , Haramoto Nobuhiro , Sakai Tadamoto 
Published: April 2003

AbstractTo provide a computer assisted system in finding optimum conditions for injection molding operations, an Expert System based on Artificial Intelligence (AI) technique and knowledge or “know‐how” from many skilled injection molding operators has been developed. For the construction of this Expert System, we have originally applied a new method of “Multi‐dimensional Matrix” that represents the relationship between the parameters of each molding condition and expert's knowledge. In this article we describe an outline of the system and the process of converting expert knowledge into AI rules, and demonstrate some molded samples obtained using this Expert System. © 1993 by John Wiley & Sons, Inc.
Plassex: An expert system for plastics selection
Authors: Agrawal Deepak , Vasudevan P. T. 
Published: April 2003

AbstractPLASSEX is a forward‐chaining rule‐based expert system for plastic selection written in CParaOPS5. This system prompts the user for desired properties, and lists all plastics suitable for a particular application. At present, PLASSEX has 393 plastics in the data base and considers up to 39 polymer properties in order to select the right plastic. More properties can be added to the system with some understanding of the code. This system also provides the user with a help facility. PLASSEX has a number of other features; for instance it gives the user an opportunity to modify any property in case the system fails to come up with a suitable plastic the first time. © 1993 by John Wiley & Sons, Inc.
Graft copolymers and ionomeric associations from mixtures of phenoxy with acid functionalized polyolefins—Part I: Reactants, compositions, and morphology
Authors: Mascia L. , Bellahdeb F. 
Published: April 2003

AbstractMixtures of phenoxy, (a polyhydroxyether of bisphenol A) with respectively ethylene–propylene copolymer containing grafted anhydride groups along the chains (EP‐g‐MA), terpolymers of ethylene, t‐butyl acrylate and acrylic acid (EAA), and the sodium ionomer of a terpolymer of ethylene alkyl acrylate and methacrylic acid (I), were produced on a 25 cc torque rheometer. Small amounts of different organic sodium compounds, exhibiting varying levels of base strength, were also used to catalyze the reaction between the functional groups of the two polymers in the mixture. It was found that whereas EP‐g‐MA reacted with phenoxy to produce both graft copolymers and cross‐linked products in varying amounts, the terpolymers containing carboxylic acid groups in the backbone of the polymer chains would never give rise to the formation of cross‐linked products even when large amount of a strong base, such as sodium ethoxide, was used to catalyze the reactions. The latter mixtures exhibited the characteristics of ionomers, involving also alkoxide anions from the phenoxy component to an extent which depended on the base strength of the sodium compound used. The ionomeric mixtures displayed morphological features varying from finely dispersed particles to cocontinuous phases. © 1994 John Wiley & Sons, Inc.
Melt viscosity of polycarbonate–polyolefin blends
Authors: Huang Jan‐Chan , Shen Hsiao‐Fu , Chu Ying‐Ti 
Published: April 2003

AbstractThe flow behavior of polycarbonate (PC) blended with three kinds of polyolefins (LDPE, HDPE, PP) was studied at 260°C using an Instron Capillary Rheometer. Flow behavior of the blends was found to be very different from that of the individual components, and significant viscosity reductions were observed for blends consisting of 5% and 15% polyolefins. In particular, the viscosity of PC/HDPE was found to be much lower than that of the parent viscosity at a shear rate below 100 1/s. For pure components, a crossover of PC viscosity was observed at high shear rate for HDPE and PP. Interfacial slippage in the blends has been suggested as the flow mechanism by which a substantial reduction in the melt viscosities of either component takes place upon the addition of a small amount of the other. A new method was proposed to evaluate the relationship between the characteristic slip factor of the blend and the viscosity of the mixture. A single master curve was obtained, i.e., σm/αAB = a · p±b, where σm is the shear stress at the matrix, αAB the slip factor, p the viscosity ratio, and a, b the constants. © 1994 John Wiley & Sons, Inc.
Blends of thermotropic liquid crystalline and thermoplastic polymers: A short review
Authors: Roetting Oliver , Hinrichsen Georg 
Published: April 2003

AbstractIn this short review, some important phenomena often observed in blends of thermotropic liquid crystalline and thermoplastic polymers are described. Their outstanding physical properties will probably lead to applications as in situ composites. LCP of low concentration in the thermoplastic matrix can be used as a processing agent. The relations between rheology, morphology, and mechanical properties of the blends are explained. Flexible elements in the LCP‐molecules can lead to partial miscibility and improved adhesion between the components. A review of recent literature is given. © 1994 John Wiley & Sons, Inc.
Polystyrene–polyethylene interpenetrating‐like networks: Influence of the vinyl network cross‐linking agent on IPN properties
Authors: Greco Roberto , Astarita Maria Francesca , Fiedlerovà Agnesa , Borsig Eberhard 
Published: April 2003

AbstractThe influence of a cross‐linking agent (divinyl benzene) on new polystyrene–polyethylene, IPN‐like networks was investigated by means of thermal, mechanical tests and a few microscopy observations. It was found that with increased concentration of cross‐linking agent, i.e., with PS cross‐linking density, Young's and storage moduli, measured in the molten rubbery state, increased linearly. Also the elongation and the stress at break were very sensitive to the content of cross‐linking agent, mainly in the low concentration region (0 to 2%). PE and PS domains of about 1 μm circular cross sections were observed on a smoothed surface of a PE/PS blend. Smaller and uniformly dispersed domains were observed for all the IPN‐like systems. The crystallinity, measured by DSC and WAXS, and the IPN morphological features, appeared to be independent of the styrene cross‐linking content, viz., the content of DVB. The overall behavior seemed to resemble that of classical simultaneous IPNs. © 1994 John Wiley & Sons, Inc.
On the measurements of the radial temperature distribution in an extruder channel
Authors: Esseghir Mohamed , Sernas Valentinas 
Published: April 2003

AbstractIn single‐screw extrusion it is not unusual to encounter large temperature variations within the screw channel, especially at high pumping rates. These temperature variations result in nonhomogeneities that affect the quality of the final product. Although there have been numerous efforts aiming at the simulation of the flow in the channel of a single‐screw extruder, and the prediction of important flow quantities, there is hardly any published work in which the temperature distribution in the screw channel was actually measured. Such measurements, if available, would provide data by which computer simulations could be validated. In the present study, a fast‐response, cam‐driven thermocouple system was developed and used to measure the radial temperature distribution in the screw channel. The measurements are carried out on a well‐controlled, custom‐built, single‐screw extruder. Temperature profiles in the centerline of the screw channel were obtained for various operating conditions of the machine. The data obtained revealed interesting features of the flow as well as the dominant heat transfer mechanisms. The system as developed here can be improved to accommodate larger industrial applications. © 1994 John Wiley & Sons, Inc.
Recovery of poly(methyl methacrylate) by the dissolution/reprecipitation process: A model study
Authors: Papaspyrides C. D. , Gouli S. , Poulakis J. G. 
Published: April 2003

AbstractApproaches to plastics recycling mainly include direct recovery keeping the polymer structure intact, depolymerization and then reuse of monomers, and methods involving reduction of polymer to gases and low molecular weight oils. The model process presented here belongs to the first category: It is proposed dissolution of the starting material, reprecipitation, thorough washing of the polymer obtained, and drying. With regard to the solvent mixtures involved, these are separated by distillation for further reuse. The technique is applied to poly(methyl methacrylate) (PMMA) molding compound, recycled as model starting material. The following criteria are considered: (a) precipitation of the polymer in an acceptable form; (b) maximum “waste” concentration; (c) maximum solution/nonsolvent volume ratio; and (d) maximum extent of poly(methyl methacrylate), solvent, and nonsolvent recovery. On the basis of these criteria, toluene/n‐hexane proved to be the most satisfactory solvent/nonsolvent system. © 1994 John Wiley & Sons, Inc.
Polycarbonate/ABS blends: Processability, thermal properties, and mechanical and impact behavior
Authors: Greco Roberto , Astarita Maria Francesca , Dong Lisong , Sorrentino A. 
Published: April 2003

AbstractPC/ABS blends, encompassing the whole composition range between PC and ABS, were prepared by a Brabender‐like apparatus and compression molded in sheets. The analysis of processability, confirming the improved PC processability by ABS additions, was accomplished by the same apparatus used for the blend preparation. A DSC investigation confirmed the inward Tg shift found by other authors. Two very different mechanical tests were performed: (a) tensile stress–strain on unnotched specimens at a very low deformation rate, showing a decreased PC ductility in blends with ABS additions; and (b) flexural impact tests (Charpy mode) on sharply notched specimens at a very high deformation rate, where a strong synergistic effect was detected in a restricted composition range (20–30% ABS). A comparison of the experimental data of the Young's modulus versus blend composition with the Kerner's model predictions confirmed the good adhesion existing between PC and ABS domains. The results were interpreted on the hypothesis of interlayer zones existing at the PC/ABS boundary. © 1994 John Wiley & Sons, Inc.
Injection molding of medical plastics: A review
Authors: Amellal Karim , Tzoganakis Costas , Penlidis Alexander , Rempel Garry L. 
Published: April 2003

AbstractGiven the tight competition in the area of plastics for medical applications, the requirements for consistent quality, standardized, safe, and low‐cost medical components have become a big challenge for molders. The survival of injection molding companies for medical applications depends strongly on the success of design, manufacturing, and marketing strategies that different companies have established to meet these requirements. Very often, the design and manufacturing operations to produce medical plastics for the health‐care market have to be adjusted on a daily basis in order to satisfy increasingly strict, government‐regulated, biomedical requirements in addition to all the other pressures expected in this market. As a result, molders of medical plastics are always seeking more systematic ways to improve product quality and produce more at a minimum cost. This brings an advantage to those processors that can combine high‐tech molding with low‐cost production. In this article, based on the open literature, we present a review of the latest activities (last decade) in the field of injection molding of medical plastics together with some comments on modern injection molding processes that can be used. © 1994 John Wiley & Sons, Inc.
Development and application of CAE technology for the gas‐assisted injection molding process
Authors: Turng L. S. 
Published: April 2003

AbstractGas‐assisted injection molding is an innovative process that can provide tremendous flexibility in design and manufacturing of plastics parts once it is fully understood and matured. The research effort presented in this article is aimed at development of Computer‐Aided Engineering (CAE) technology for gas‐assisted injection molding. To achieve the goal, efforts have been made in developing a numerical analysis for predicting the filling and post‐filling behavior and verifying the predictions through collaboration with the industry and universities. This article firstly describes the physics of this process, which leads to the various advantages and the inherent difficulties associated with the design and processing. Secondly, it discusses the methodology of numerically modeling and simulating gas‐assisted injection molding filling dynamics together with experimental comparison. At the end of this article, it presents the various advantages of applying the CAE technology for the gas‐assisted injection molding process, such as evaluating the various gas‐assisted injection molding processes and establishing preliminary design guidelines. © 1995 John Wiley & Sons, Inc.
Experimental study on the effects of adding compression to injection molding process
Authors: Yang S. Y. , Ke M. Z. 
Published: April 2003

AbstractThe quality of thermoplastic injection molded parts is mainly determined during the post‐filling process. To enhance the control capacity over the post‐filling process, adding compression to the conventional injection molding process opens a flexible channel for pressure control. This study experimentally investigated the effects of adding compression on the thermal‐mechanical history and on the quality of molded parts. An instrumented molding machine with a compression mechanism was used. Molds for rectangular plate and circular disk were equipped with a movable cavity wall and shut‐off mechanism. The thermomechanical history during the injection compression molding was identified with the aid of a PC‐based data acquisition system. The quality of parts was evaluated by flatness, deviation from mold dimensions, and birefringence. It has been found that the thermomechanical history of the melt under injection compression molding follows a quadrilateral‐shaped path over the p‐v‐T diagram. The control capacity over post‐filling is enhanced. It thus can produce parts with better dimensional control with less frozen‐in orientation than those from conventional injection molding. © 1995 John Wiley & Sons, Inc.
Improvement of weldline strength of fiber reinforced polycarbonate injection molded articles using simultaneous composite injection molding
Authors: Tomari Kiyotaka , Takashima Hiroki , Hamada Hiroyuki 
Published: April 2003

AbstractFiber reinforced thermoplastics (FRTP) injection molded articles have many advantages. However, moldings with a complex geometry often encounter weldline problems. Mechanical properties of the injection moldings are often reduced by weldlines, because the fibers at weldline regions orient perpendicularly to the flow directions. We have reported that weldline strength is improved by “back‐flow” during the holding stage. In this article, we have attempted to adapt the SCI (Simultaneous Composite Injection) molding method to improve weld strength of FRTP injection moldings. The back‐flow is expected to occur when there is a difference of holding pressure between two cylinders of the SCI molding machine. The effect of pressure difference between two injection cylinders on the back‐flow phenomena is discussed for fiber reinforced polycarbonate. It is clear that the strength reduction by the weldline can be suppressed down to negligibly small levels in SCI molding. © 1995 John Wiley & Sons, Inc.
Volatile emissions during thermoplastics processing—a review
Authors: Patel S. H. , Xanthos M. 
Published: April 2003

AbstractTypes and amounts of volatiles emitted during thermoplastics processing depend upon the chemical structure of the material and the choice of processing conditions. The identification of volatiles and the development of analytical techniques for measuring their concentration in the workplace are of paramount importance to establish or revise threshold limit values that would minimize exposure to hazardous chemical substances and lead to corrective action. In this review, information related to the types of volatiles emanating from injection molding machines and extruders as well as analytical methods for their measurement was collected, analyzed, and tabulated. Emphasis was placed on the four major commodity plastics, viz., polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), and polystyrene (PS). Although the main emphasis is on emissions during processing, related literature under simulated conditions is also mentioned. © 1995 John Wiley & Sons, Inc.