bluuebunny/crossref_metadata_2025_split huggingface dataset:
Theoretical and experimental study of non‐isothermal deformation of a blow molding parison
Authors: Basu Santanu , Fernandez Franco 
Published: April 2003

AbstractThe thickness distribution in a blow molded product depends on swelling and sagging of the extruded parison. In this paper, the extensional deformation during parison formation process has been described theoretically, using a swelling function and Jeffrey's equation for material viscoelasticity. The heat balance equation has been solved simultaneously to treat the more general case of parison being exposed to ambient conditions. Experiments were carried out on a commercial blow molding machine with three polymers and, in each case, parison deformation was recorded on a videotape. The experimental results of parison sagging and the theoretical results have shown good agreement.
Energy utilization in extrusion
Authors: McKelvey James M. 
Published: April 2003

AbstractThe mechanics of energy conversion in an extruder is extremely complex. Generally speaking, the extrusion process utilizes two sources of energy: (1) mechanical energy which is imparted to the polymer by the rotational motion of the screw, and (2) thermal energy (heat) which flows between the polymer and surfaces of the barrel by conduction and convection.Modern extrusion processes are relatively wasteful of energy because, operating at high speeds, they often dissipate an excess of mechanical energy as heat that has to be transferred (by barrel cooling) from the polymer and discharged into the surroundings as waste energy.Until recently, little attention was paid to this wasted energy. Energy was relatively cheap and the process economics favored was high speed operation despite its associated energy wastage. With the recent introduction of gear pumps for extruders, low pressure extruder operation becomes a possibility. It appears that this type of operation may result in a significant improvement in energy efficiency.This paper attempts to analyze the energy economy of extrusion processes and to understand where and how energy savings can result from the use of gear pumps. It shows that if substantial energy savings are to result from the use of gear pumps, these savings will come about not because of increased pumping efficiencies, but because low pressure operation has made a fundamental change in the energy conversion processes occurring in the screw.
A nonlinear viscoelastic characterization of creep rupture in a reinforced plastic
Authors: Brockway G. S. , Martin R. E. 
Published: April 2003

AbstractThe long‐term behavior of a glass mat‐reinforced polypropylene has been characterized by accelerated flexural creep tests on samples of the laminate. Considerable data were collected for stress levels ranging from 200 to 7500 psi at six temperatures from room temperature to 140 °C. The material was found to behave in accordance with the linear theory of viscoelasticity except at the longer times where the creep rate increases dramatically and the specimen ruptures. The stress and temperature dependence of this “terminal creep” zone was treated by means of a slightly modified version of Schapery's thermodynamic theory of nonlinear viscoelasticity, which involves the superposition of double logarithmic plots of creep compliance versus time. The stress and temperature dependence of both the free energy function and the entropy production emerge from this treatment. A comparison of nonisothermal creep data with a prediction from the isothermal master curve is marginally acceptable. A statistical synthesis of the data discloses that the incidence of terminal creep is log‐normally distributed. Moreover, the standard deviation associated with the distribution is independent of temperature. It is therefore possible to assess the probability of failure for any constant stress at any constant temperature.
Linear low density polyethylene: An overview
Authors: Pickover Bruce H. 
Published: April 2003

AbstractLinear low density polyethylene (LLDPE) has been produced for about 20 years; however, the commerical potential of the product was not fully appreciated until Union Carbide developed its vapor phase process. Now many companies throughout the world are producing LLDPE. The following paper reviews some of the different processes to produce LLDPE.
The outlook for rubber processing equipment
Authors: Rapetski Walter A. 
Published: April 2003

AbstractThe outlook for rubber processing equipment in the 1980s is good, as is the future for rubber compounding processing. A significant number of changes have occurred in the rubber industry and, subsequently, in rubber processing equipment. Compound processing machinery reflects the awareness of energy costs and the need for conservation. There is a slow but growing trend toward continuous processing. The elastomers are more readily available in particle form. The machinery reflects a far greater understanding of the nature of the material to be processed, and the need for the processing equipment to be able to operate with this in mind. The processing machinery of the 1980s is not necessarily bigger, but it is better because it is smarter. The old magic and mysterious art of rubber compounding and compound processing is being completely replaced by machinery systems that scientifically process rubber compounds.
Characterization of thermoplastics using selected material data
Authors: Kemper Wolfgang 
Published: April 2003

AbstractWith the increasing demands for quality in plastic products, the characterization of materials becomes more and more important in the evaluation of properties of structural parts and processing conditions, and in performing quality control.An attempt shall be made to introduce basic principles for the sizing and manufacture of molded parts by means of the fewest possible material data. This characterization is to be made using the p‐v‐T diagram, the shear modulus curve, and the viscosity curve. These material data are then used for quality control of the raw material and the finished product.
The finite element method for flow and heat transfer analysis
Authors: Mitsoulis Evan , Vlachopoulos John 
Published: April 2003

AbstractThe finite element method (FEM) is discussed and a specific formulation for flow problems is outlined that can encompass non‐Newtonian inelastic and viscoelastic fluids. A temperature formulation is also considered that can be applied for nonisothermal analyses of fluid flow. Some illustrative examples of the application of the method in polymer processing are also presented.
Design of thermoform molds
Authors: Throne J. L. 
Published: April 2003

AbstractMolds used for low pressure forming of rubbery polymeric sheet have certain design constraints. The choice of mold material depends upon the severity of service and the number of parts required. Specifications for wood, plaster, aluminum, thermosetting resins, sprayed metal, and steel are discussed. Design criteria for vent hole diameter and number of vent holes are presented. Frictional aspects of mold surfaces and ancillary aspects of mold design, such as clamping mechanisms and sheet supports, are discussed.
From polymerization to product: The effect of molecular structure on the properties of butadiene‐acrylonitrile copolymer elastomer
Authors: Nakajima N. , Harrell E. R. , Kumler P. R. , Seil D. A. , Jorgensen A. H. 
Published: April 2003

AbstractButadiene–acrylonitrile copolymers were prepared with such variations in molecular structure as molecular weight, degree of long branching, and gel. The acrylonitrile content was varied from 28% to 44%. Viscoelastic behavior of gum elastomers, uncured compounds, and vulcanizates were characterized. Thus, the effects of molecular architecture on the properties were followed through the processing steps of compounding and vulcanization. Also, the effects of molecular parameters on the large deformation of vulcanizates were examined by the tensile stress–strain behaviour. The fracture toughness was examined with the tensile failure characteristics and De Mattia Flex Test
Profile extrusion of PVC through rectangular dies
Authors: Kumar Rakesh , O'Brien Keith 
Published: April 2003

AbstractThe design of profile dies for extrusion has always been by trial and error since the extrudate swells in an unpredictable manner. Most of the studies conducted have involved flow through capillary dies, and indeed only a few investigators report studies on cross sections other than circular. It is the purpose of this study to present a fundamental experimental investigation and theoretical interpretation of the phenomenon of die swell for a rectangular die. In the present study the effects of die entrance geometry, aspect ratio, and die land lengths have been investigated in terms of swelling characteristics of PVC. It is observed that die swell increases for increasing entrance angles up to 60° and then decreases for angles up to 120°. Dependence of die swell on aspect ratio and shear rate has also been reported. Each of the observed phenomenon has been comprehensibly explained and plots have been provided which could aid preliminary die design.
Reactive polymer processing: Techniques and trends
Authors: Kamal Musa R. , Ryan Michael E. 
Published: April 2003

AbstractThermosetting materials are expanding their market penetration owing to their excellent heat resistance and performance characteristics. Energy conservation considerations have also resulted in the development of processing techniques involving the simultaneous polymerization and shaping of the part. The processability of a reactive system is dependent on the thermal and deformation history which is experienced by the material. Despite this processing sensitivity, significant new developments have occurred in recent years including improvements in machinery design, process automation and control, novel processing technology such as RIM and pultrusion, and advances in material formulations. The processing of reactive systems will be considered with emphasis given to the recent developments concerning mathematical analysis and simulation of the process dynamics and the relationship between processing history and part properties.
Effect of mold‐filling conditions on fiber distribution in injection‐molded disks and on the mechanical properties of such disks
Authors: Delpy U. , Fischer G. 
Published: April 2003

AbstractThe mechanical properties of test specimens from centrally injection‐molded disks made of short glass fiber‐reinforced polyamide 6,6 were tested under conditions of monaxial and biaxial constant strain rate and impact stress. In addition, the disposition of the glass fibers in the molded parts was established by optical microscopy and roentgenographic methods. Image analysis was used to measure the reduction of mean fiber length caused by processing and to determine quantitatively the fiber orientation. The possible existence of a correlation between fiber orientation data, as obtained from photomicrographs of polished sections, mechanical properties, and fracture characteristics is discussed.
Glass transition temperature in polymer blends
Authors: Utracki L. A. 
Published: April 2003

AbstractThe Couchman equation for miscible blends has been extended. The new semiempirical equation, w1ln(Tg/Tg1) + kw2ln(Tg/Tg2) = 0, is simple to use and flexible enough to provide an adequate description of Tg variation with composition for miscible, semimiscible, and immiscible blends. The equation parameter k indicates the blend miscibility.
Study of bubble growth in foam injection molding
Authors: Upadhyay R. K. 
Published: April 2003

AbstractThe bubble growth in polymeric fluids under nonisothermal conditions has been molded using the viscoelastic constitutive equation of Leonov incorporating the diffusion of gas from the melt to the bubbles. The gas diffusion seems to be the primary mechanism of bubble growth. The theoretical predictions for Han and Yoo's isothermal experiment compare well with the experimental data. The bubble size distribution in a foam molded specimen of NORYLRegistered trademark of the General Electric Company.
resin has also been determined by measuring the bubble size from micrographs. Theoretical predictions for this specimen are in reasonable agreement with the data. A parametric study indicates that the blowing agent concentration has the strongest influence on the final bubble size, followed by melt and the mold temperature.
Melt finishing operations in CdF chimie LLDPE process
Authors: Gloriod Pierre 
Published: April 2003

AbstractThe CdF Chimie LLDPE process uses retrofitted high pressure autoclave LDPE units to make a broad range of ethylene–α‐olefin copolymers covering melt indices from 0.5 to 50 and densities as low as 0.88. The melt pelletizing extruder may be used to improve polymer properties by mixing with selected additives, other polymers like LDPE, and miscellaneous reagents.
Deformational history of LLDPE/LDPE blends on blown film equipment
Authors: Huang T. A. , Campbell G. A. 
Published: April 2003

AbstractA video camera tracer technique (T. A. Huang and G. A. Campbell, paper to be presented at ANTEC '85, Washington, D. C.) was used to obtain MD velocity profile and bubble shape above the air ring under industrial film blowing conditions. Subsequently, the velocity profile and bubble shape were utilized to calculate strain and strain rate histories for a fluid element before it solidified. The deformational history of a fluid element was compared between LDPE and LLDPE of similar melt index and density. Also, the study was extended to two groups of LLDPE/LDPE blends: blends rich in LLDPE and blends rich in LDPE. We used a 100‐mil die gap for extruding resins rich in LLDPE to avoid melt fracture. A 30‐mil die gap was used to process blends that were rich in LDPE. Under the same film blowing conditions and frost line height, LDPE exhibits higher peak strain rates than LLDPE and the peak strain rates for LDPE occur closer to the air ring. Moreover, the MD strain of LLDPE continues to increase above the frost line. Conversely, the MD strain profile of LDPE levels off quickly before the frost line. The observed differences in fluid element deformation between LLDPE and LDPE on the blown film line are attributed to the higher melt tension of LDPE. For LLDPE, a 10 wt % LDPE addition causes a significant increase in strain and strain rate at lower positions. Interestingly, a further addition up to 25 wt % LDPE causes little or no further change in deformational history. The increased strain rates associated with an increased strain results in a stabilized LLDPE bubble. For LDPE, only slight differences in strain and strain histories were observed with the addition of LLDPE up to 25%.
Electrical and thermal properties of polypropylene filled with steel fibers
Authors: Katsura T. , Kamal M. R. , Utracki L. A. 
Published: April 2003

AbstractPolypropylene (PP) compositions containing 0–20 vol % of steel fibers (SF) [neat or with 5 wt % of maleated propylene wax (MPP)] were prepared and tested for electrical and thermal conductivities. It was found that, at room temperature, the volume resistivity Ωv fell below 10 ohm cm at SF loading of about 10 vol %. However, as the test temperature increased to 120°C, higher loadings were required to secure the same resistivity, i.e., 12 and 14 vol % of SF for composites without and with MPP, respectively. By contrast with a sharp decrease of Ωv (by 16 orders of magnitude upon addition of a few percent of SF), the increase of thermal conductivity was much less dramatic. The thermal conductivity k of the composites was found to be proportional to volume loading, increasing by a factor of 1.8 on addition of 20 vol % of SF, independently of temperature and MPP presence. Annealing had a small positive effect on k.
Effect of die design on the analysis of wire coating
Authors: Wagner Roy , Mitsoulis Evan 
Published: April 2003

AbstractA general‐purpose finite element program has been used to analyze the flow of LDPE and plasticized PVC inside wire‐coating dies under typical operating conditions. The analysis is fully two‐dimensional and nonisothermal. It is shown that die design has a strong effect on the flow and temperature patterns, especially for the more sensitive PVC compound. The analysis can be used as a guide for optimum operating conditions and for better die design that allows for faster wire speeds without occurence of melt fracture and rough coating surface.
Compounding of thermosets in continuous kneaders
Authors: Kalyon Dilhan M. , Hallouch Madani 
Published: April 2003

AbstractVarious rheological and ultimate properties of thermosetting resins are strongly dependent upon the thermomechanical history that the resin is subjected to during the compounding step. Besides the considerations of the dispersion and homogeneity of various ingredients in the compound, thermosetting resins can easily crosslink to some extent during compounding. In this study, a Buss Continuous kneader, Model PR 200 was employed to compound a phenol–formaldehyde molding powder. The operating conditions in the continuous kneader were varied systematically, and samples were collected. The processability behavior of the resin samples were characterized employing the eccentric rotating disc (ERD) flow in conjunction with a Rheometrics Mechanical Spectrometer, squeezing flow under constant pressure, and torque rheometry, utilizing a Brabender Plasticorder. The extent of curing of resin samples were further determined by acetone extraction. It is shown that the stability of the thermoset compounding rate, temperatures, and power consumption, strongly depends on the operating conditions selected. Furthermore, unstable operation invariably leads to the premature curing of the thermosetting compounds during the compounding operation. The premature curing of the compound adversely affects its flow, curing, and processability behavior.
Microscopic foundation of tribological failure for fibrous composites
Authors: Lhymn Chang 
Published: April 2003

AbstractSome thoughts were given to wear rate and frictional force to derive a possible expression in terms of material parameters. Derived equations are based on the concepts of fracture mechanics, delamination physics, molecular kinetics, and thermally activated process. Theories have been tested against friction/wear data of fiber‐reinforced thermoplastics.
Physical and chemical changes during the extrusion process
Authors: Bartilla T. , Kirch D. , Nordmeier J. , Prömper E. , Strauch Th. 
Published: April 2003

AbstractChemical and physical processes are attracting increasing attention from plastics processors. The reasons for this are basically twofold. On the one hand, more and more processors are recognizing that the quality of their products is highly dependent upon physical processes (cooling, temperature control, blending, etc.) and, on the other hand, new methods of physical and chemical treatment are being developed which are bringing improvements in quality and hence, virtually inevitably, greater profitability in production. This technology has made its impact both on discontinuous processing (reaction injection molding), on cable and pipe extrusion, and on the direct polymerization of tapes and films. The formulations that can be applied here are monomer casting systems. A prerequisite for the industrial utilization of this system is a process analysis of the reaction molding compound processing in a parallel‐running twin screw extruder to allow the influence of the process parameters on product quality (e.g., molecular weight) to be clarified and the polymerization to be integrated into other processing sequences, such as panel extrusion. The modification of tried and tested plastics through blending with other polymers, however, can also change the properties of the material in such a way that cost‐intensive plastics can be replaced or even new fields of application can be opened up. The attainable properties are just as much a function of the individual components and their percentage content as they are of the blending technique, as investigalions on a corotating twin‐screw extruder have shown. The melting zone takes on primary significance, since it is here that both the homogenization and desired or undesired high shearing takes place. The crystallization of semicrystalline plastics also has a considerable influence on product quality. To date this has been influenced by the selective addition of nucleiproducing foreign substances. A new process substitutes electron‐irradiated granules for these nucleating agents, such that the drawbacks of the foreign particles (toxicity, notch effect, and optical impairment) are eliminated. The effectiveness of this measure is reflected in better mechanical characteristic values. These both allow a higher product quality and a shortening of cooling time and hence higher productivity. Modijication of material properties through subsequent crosslinking represents the state of the art in rubber and polyethylene extrusion for cables and pipes. Special peroxides and the application of microwave energy make it possible to crosslink extrudates (pipes, profiles) made of HDPE and EPDM. The kinetics of crosslinking are explained, taking the example of crosslinking with peroxides. It is seen that the process technologv has to be adapted to the compound in terms of residence time and temperature. Under these conditions the microwave energy crosslinking plant operates with considerably shorter plant lengths and hence with lower energy losses.
Die flow computations: A method to solve industrial problems in polymer processing
Authors: Vergnes B. , Agassant J. F. 
Published: April 2003

AbstractThe flow of molten polymers through extrusion dies sets specific problems, usually connected to homogeneous distributions of flow rate and temperature. To overcome these problems, the computation of the flow by numerical techniques may be very useful. In this paper, approximation methods are developed, in order to treat industrial die geometries, without too complex and time‐consuming computation programs. Different examples of results, for the main types of industrial dies, are presented.
LLDPE rheology and blown film fabrication
Authors: Ramamurthy A. V. 
Published: April 2003

AbstractExtrudate irregularities, or “melt fracture,” with narrow MWD LLDPE resins occur at low deformation rates, and represent a severe rate limiting factor in commercial blown film fabrication with narrow die gaps. Extensive capillary rheometer measurements for several polymers, and blown film fabrication studies for LLDPE, seem to support an earlier finding that slip in the die land region invariably accompanies the observed extrudate irregularities. Lack of strong chemical forces for adequate adhesion at the polymer/metal interface in the die land region appears to be primarily responsible for the initiation of slip. Improvements in adhesion, by proper choice of the materials of construction and/or adhesion promoters in the resin, virtually eliminate the rate limiting effects of melt fracture in commercial blown film processing, and provide substantial improvements in critical end‐use properties, with LLDPE.
A finite element simulation of polymer melt flows
Authors: Tanguy Philippe A. , Fortin André 
Published: April 2003

AbstractAn augmented Lagrangian formulation is used to model the nonisothermal, bidimensional flow of a shear‐thinning fluid in a sudden planar contraction by the finite element method. An efficient solution strategy is proposed which enables computations at large Peclet number and for highly nonlinear rheological behavior at a reasonable cost.