bluuebunny/crossref_metadata_2025 huggingface dataset:
Energy utilization in extrusion
Authors: McKelvey James M.
Published: April 2003

The 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

The 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

Linear 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

The 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

With 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.
Compounding options for heat sensitive products
Authors: Mack Martin
Published: April 2003

The process and equipment requirements for compounding of heat‐sensitive polymers are evaluated. The advantages and disadvantages of various compounding equipment is discussed, which includes single and twin screw extruders, planetary gear extruders, and pin barrel mixing extruders.
The finite element method for flow and heat transfer analysis
Authors: Mitsoulis Evan , Vlachopoulos John
Published: April 2003

The 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

Molds 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

Butadiene–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

The 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

Thermosetting 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

The 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

The 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

The 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 NORYL

Registered 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

The 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

A 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

Polypropylene (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

A 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.
Tribological properties of fibrous peek matrix composites
Authors: Lhymn Chang
Published: April 2003

The wear rates and friction coefficient of (PEEK/fiber) composites have been measured under various tribological conditions of sliding velocity, fiber fraction, and kinds of fiber (carbon or glass). The measured tribological data were explained by means of wear and friction equation and also correlated with the observed microstructure.
Compounding of thermosets in continuous kneaders
Authors: Kalyon Dilhan M. , Hallouch Madani
Published: April 2003

Various 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

Some 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

Chemical 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

The 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

Extrudate 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

An 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.
Some comments on the wear and friction behavior of fiber‐reinforced thermoplastics
Authors: Lhymn C. , Pulsifer A. H.
Published: April 2003

The frictional and wear behavior of fiber‐reinforced thermoplastic matrix have been investigated by means of tribological data and microscopy. Particularly the effect of sliding velocity, fiber content, and wear mechanism on the wear rate and friction coefficient has been studied. The observed data have been correlated with the wear and friction equation to test the validity of recent models qualitatively. The microstructural sequence of adhesive wear has also been investigated by means of the scanning electron microscopy. The effect of sliding velocity on wear rate is considered theoretically.
The effect of solids conveyance on the stability of the single screw extrusion process
Authors: Bigg D. M.
Published: April 2003

The flow of a polymer powder in the feed section of a single screw extruder has been experimentally investigated for its relationship to extruder stability. It is shown that the feeding and compaction process is inherently random, leading to random fluctuations in the position along the screw where melting begins. Such fluctuations are not considered serious under most circumstances, however. More severe fluctuations are generated when the taper of the compression zone causes the solid bed to re‐form across the screw channel. This disrupts the melting process, and prevents the extrusion process from proceeding in a steady state manner. Such a phenomena, is by its nature periodic, leading to long‐term fluctuations in the output of the extruder.
Study of extraction method on measuring insoluble constituents of ultrahigh molecular weight polyethylene
Authors: Eyerer P. , Kurth M. , Cui D.
Published: April 2003

Ultra‐high molecular weight polyethylene (UHMWPE) has exceptional physical properties and outstanding abrasion resistance. Examinations1,2 show property changes of explanted joint prostheses during different implantation times. Because of the in vivo aging, the molecular weight decreases while the amount of soluble parts increases. By irradiation sterilization, the UHMWPE is crosslinked and degraded. To measure insoluble constituents of UGMWPE, a new improved extraction method is given. The extraction coefficient depended on the kind of extractor and solvent but had no dependence on the height of sample placed in the glass filter crucible. Using this method to determine insoluble constituents had significant advantages.
Processability of organometallic polymer precursors for nonoxide ceramic applications
Authors: Kalyon Dilhan M. , Kovenklioglu Suphan
Published: April 2003

Nonoxide ceramics can be obtained from the high temperature pyrolysis of organometallic polymer precursors. This study has focused on the processing behavior was investigated employing a Rheometrics mechanical spectrometer, RMS 800, and a PerkinElmer Model 4 differential scanning calorimeter. The effect of various environments including nitrogen and oxygen were also studied. The melt processing capability of polycarbosilane was found to be rather limited. Finally, a model which describes the pore formation process during pyrolysis has been proposed.
Membranes, an important polymer product for industrial process technology—new developments concerning their manufacture and uses
Authors: Rautenbach R. , Janisch I. , Ing. Dipl.
Published: April 2003

The principles common to three membrane processes, i.e., reverse osmosis, and gas permeation, and pervaporation, involving separating by means of “dense,” i.e., pore‐free, synthetic polymer membranes are presented. On the basis of these principles, it is then shown how the requirements placed on the membrane and the modules by the transport mechanism (solution and diffusion) are satisfied. A few examples characteristic of the current state of technology are discussed.
Flow visualization of blending of elastomers and thermoplastics in an internal mixer
Authors: Min Kyonsuku
Published: April 2003

Flow visualization of blending elastomers and plastics in an internal mixer is described. This is based on observations from front and transverse glass windows placed on the mixer. This enabled us to investigate the flow behavior of pure polymers during the blending operation. The flow behavior was categorized into four regimes which depend on temperature and the polymer. The flow regimes dominate the phase morphology of blends of ethylene–propylene terpolymer and polystyrene. Various rotor designs used in this study creates different two phase morphology due to various flow fields.
Effects of compounding techniques on the properties of mica‐reinforced engineering thermoplastics
Authors: Wright A. N. , Hawley G. C.
Published: April 2003

Physical properties of injection molded, mass‐granulated composites of poly(buteneterephthalate), modified PPO, and poly carbonate/PBT blends, reinforced with 30% by weight of Suzorite mica 60S were evaluated after compounding in the K‐mixer and in a single‐screw Killion extruder under a range of processing conditions. The properties varied considerably with the specific mixing conditions in both compounding systems. The K‐mixer gave higher un‐notched impact strengths for all conditions of processing for all three composites. The Killion extruder tended to give higher notched impact strengths. Tensile and flexural property development was more dependent on the plastic matrix. A wide spectra of property profiles could be developed in the K‐mixer simply by varying tip speed and discharge temperature whereas the exauder requhd changes in screw design. Current failure to produce suitable test bars from bisphenol A polycarbonate may be due to a requirement to predry the mica before mixing.
Damage accumulation and wear of fibrous composites
Authors: Lhymn C.
Published: April 2003

A microscopic equation of wear rate has been constructed based on the physics of damage accumulation during sliding wear. The equation incorporates the effect of roughness as well as other structural and tribological parameters. Various factors affecting the wear rate have been identified. The experimental data of roughness vs. wear rate have been shown to support the proposed analysis under certain assumptions.
Polymer flow through spiral mandrel dies: A comparison of models
Authors: Perdikoulias J. , Vlcek J. , Vlachopoulos J.
Published: April 2003

Three existing models used to simulate the flow of polymer melts through spiral mandrel dies are compared. Each model was of different complexity and provided different results when used to simulate the flow through two dies. All three models indicated an improvement in flow distribution when the power‐law index was increased. Experimental verification of the predictions is required before their validity is proven.
Effect of strength degradation on wear and friction
Authors: Lhymn C.
Published: April 2003

A theoretical expression for wear rate as a function of sliding velocity has been formulated from the concepts of crack propagation, thermal activation, and strength degradation and the analytic results have been tested against the experimental data to provide a comprehensive understanding of this complex behavior. A similar equation describing the relationship between the wear rate and normal load has also been provided. The coefficient of friction has been analyzed theoretically as a function of normal load and sliding velocity and compared with the experimental results. The coefficient of adhesion has given an expression by employing two approaches: average crack propagation velocity and atomic residence time concepts. Consideration of strength degradation has led to a wear rate equation which does explain the experimental result satisfactorily for polymer composites. Some thoughts has been given to the atomic chain orientation effect on wear and friction, and also the boundary lubrication phenomena have been described briefly.
Friction and wear of fiber reinforced pps composites
Authors: Lhymn C. , Bozolla J.
Published: April 2003

The friction and wear properties of fiber‐reinforced polyphenylene sulfide composites were investigated under abrasive and adhesive wear conditions, and an attempt was made to explain the observed data with the friction and wear equations. The measured tribological data were also correlated with the observed microstructures.
The melting of granular polymeric solids on a hot moving surface—the effect of convection
Authors: Sun Tzu‐Hsiung
Published: April 2003

The effect of convection on the melting rate of granular polymeric solids pushed against a hot moving surface was analyzed by including in the energy equation the convection term to compute the melting film thickness. The results of this analysis indicate that the melting film thickness is reduced by the effect of convection, providing a theoretical basis for Tadmor's suggestion to reduce melting film thickness to account for the effect of convection in calculating the melting rate.
Instrumentation development for sensing modes of bubble motion of a blown‐film process
Authors: Huang T. A.
Published: April 2003

We have developed instrumentation using an internal‐bubble pressure transducer with a data acquisition system to sense LLDPE bubble stability on a commercial blown‐film line. Real‐time bubble instability was also recorded using a video camera at a speed of 30 frames/s. The pressure signal was analyzed using a fast‐Fourier‐transform (FFT) computer program to determine the frequency of bubble oscillation. Since bubble instability often consists of large‐scale oscillation and bubble flutter, and both motions affect gauge and layflat uniformity, the pressure signal was decomposed to determine the frequency of each oscillation mode. To obtain a stable bubble, the amplitudes of both oscillation modes must be reduced to a minimum. Under a single mode oscillation, the period of bubble‐diameter variation analyzed using videotape matches that of the pressure trace. The initial results indicated that the trace of the pressure can provide a warning to the stability of a blown‐film process.
Thermoforming crystallizing poly(ethylene terephthalate) (CPET)
Authors: Throne James L.
Published: April 2003

Nonisothermal crystallizing kinetics for nucleated polyethylene terephthalate (PET) are combined with transient heat transfer models to predict crystalline levels throughout the process of extruding and thermoforming crystallizing PET (CPET). The analysis includes:

PET molecular weight effect (through IV)

Nucleant level effect

Cooling of extruded sheet on chill rolls

Convection in the thermoforming oven

Oven radiant heater temperature

Radiation interchange efficiency in the heating oven

Equilibration

Mold surface temperature and atmosphere

Cooling time

The analysis compares distributed parameter finite difference analysis with a lumped parameter method. Material‐environmental parametric studies are conducted using the lumped parameter method. The patent literature data are confirmed using an expanded version of the lumped parameter method.
Development of experimental techniques and simulation methods to analyze mixing in co‐rotating twin screw extrusion
Authors: Kalyon Dilhan M. , Gotsis Alexandros D. , Yilmazer Ulku , Gogos Costas G. , Sangani Harish , Aral Birnur , Tsenoglou Christos
Published: April 2003

Currently, the selection of elements and operating conditions in the mixing of various materials in a corotating twin screw extruder is an art which requires previous experimental studies. In this report, we outline various experimental and theoretical tools developed to investigate the mixing process in a fully intermeshing corotating twin screw extruder. The thermomechanical history of mixing is simulated employing the finite element method. To verify the numerical findings, experimental techniques were developed to investigate the goodness of mixing of samples collected from a 50.8 mm, “clam shell” design, Baker‐Perkins twin screw extruder.
Computer‐aided plastic parts design for injection molding
Authors: Menges G. , Michaeli W. , Baur E. , Lessenich V. , Schwenzer C.
Published: April 2003

A new software concept for an integrated computer‐aided design procedure for injection‐molded parts is presented. This software has been developed in close cooperation with the plastics industry and therefore takes into consideration, to a very high degree, requirements arising from practical use. The resulting program, named CADFORM, links commercial and newly developed plastics‐specific software and thus enables all the steps involved in designing a new molding and the corresponding mold to be carried out within one program system.
A computerized system for measurement of transient and equilibrium extrudate swell
Authors: Kamal M. R. , Samara M.
Published: April 2003

A computerized automatic die swell apparatus has been designed and constructed. The apparatus provides both digital and analog outputs regarding the diameter of the molten extrudate and its variation with time. Precautions are made to reduce the effects of gravitational sag and temperature changes. The apparatus was used in conjunction with an Instron capillary rheometer to measure the transient and equilibrium extrudate swell behaviour of five low density polyethylene resins, a short fiber glass filled polypropylene melt, and a thermotropic liquid crystal polymer.
Flow visualization of internal mixer factory cycles for rubber compounding
Authors: Morikawa Akihiko , Min Kyonsuku , White James L.
Published: April 2003

Flow visualization of a scaled down rubber compounding process in an internal mixer is described. The mastication of scaled down rubber bales, and the addition of carbon black and oil were studied. The times required for rubber bale ‘pickup’ by the rotors as well as bale homogenization time were determined for various elastomers. The times required to incorporate black and oil were measured.
Mixing characteristics of PC/PET polyblends in processing equipment
Authors: Awojulu Emmawuel A. , Deanin Rudolph D. , Huang Jan‐Chan
Published: April 2003

Using the melt blending procedure, various compositions of polycarbonate and poly(ethylene terephthalate) were compounded. Some of the blends were extruded and then injection‐molded, while others were directly injection‐molded into ASTM bars for physical testing. When the properties of these blends were compared, variations in values were obtained for blends of the same composition. Variations in properties were higher in blends containing less than 70% PET content. At 70% PET and above, there were negligible differences between blends of the same composition processed by different methods. Since it has been established that blends with more than 70% PET are miscible, it can be concluded that injection molding can be applied to mix miscible blends into final parts directly without a preliminary extrusion blending process.
Wear behaviour of silicone‐impregnated poly(ether etherketone)(PEEK) composites
Authors: Lhymn C. , Lhymn Y. O.
Published: April 2003

The wear and frictional behaviour of self‐lubricating polymer composites was investigates by means of tribological testing and microstructural examination. The tribological testing consists of wear rate measurement and frictional coefficient determination as a function of sliding velocity and normal load for two‐body abrasion and adhesive sliding tests. A new insight has been provided for the concept of “contact strenght” and related to the wear data using the appropriate wear equation developed from the crack propagation and damage accumulation physics.
Rheological properties, extrudate swell, and die entry extrusion flow marker experiments for rubber–carbon black compounds
Authors: Song Han Jong , White James L. , Min Kyonsuku , Nakajima Nobuyuki , Weissert Frederic C.
Published: April 2003

Rheological characterization, extrudate swell measurements, and a flow marker extrusion study for several elastomers and their compounds is reported. The materials included natural rubber (NR), styrene–butadiene rubber (SBR), ethylene–propylene terpolymer (EPDM), and polychloroprene (CR) and their carbon black compounds. The shear viscosity was measured with a sandwich rheometer, a shearing disk viscometer, and a capillary rheometer over a wide range of shear rates. Evidence for yield values is found in compounds with 0.20 and 0.30 levels of carbon black. Empirical equations were fit to the data. Extrudate swell measurements were carried out for slit and capillary dies. Increasing the level of carbon black reduces the level of swell. Flow marker experiments were carried out in the barrel of a capillary rheometer using a wide range of die designs. These indicated roughly radial streamline flows into the capillary or slit land. Recessed parts of a die could accumulate stagnant material. Evidence for wall slippage in the rheometer barrel for compounds with 0.20 and 0.30 volume fractions of carbon black is discussed.
On the wear of short carbon fiber reinforced carbon matrix composite
Authors: Lhymn C. , Lhymn Y.
Published: April 2003

The wear rate and friction coefficient of carbon–carbon composites have been investigated as a function of sliding velocity. Wear and friction models derived for fibrous polymer composites appear to be applicable for this carbon–carbon composite system. The microstructure of worn surfaces has been examined and correlated with the wear mechanism.
On the specific wear rate of polymer composites
Authors: Lhymn C. , Pepper S. V.
Published: April 2003

A numerical calculation of specific wear rate has been attempted for two kinds of sliding wear (abrasive and adhesive) using a phenomenological equation derived from the concepts of crack propagation, delamination physics, and bond rupture. An approximate estimation of several parameters in the wear equation has been performed, and there appears to be and agreement between the theoretical and experimental wear rate within the order of magnitude.
Energy balance approach to friction
Authors: Lhymn C. , Pepper S. V.
Published: April 2003

The energy balance concept has led to a new friction equation that can explain both the adhesional and plowing aspects of friction. A preliminary calculation of the frictional force has been attempted to test the validity of the proposed expression for frictional force.
A new model of flow in a tangential counter‐rotating twin screw extruder
Authors: Kim Myung H. , Szydlowski Witold , White James L. , Min Kyonsuku
Published: April 2003

The flow of Newtonian fluids in a tangential counter‐rotating twin screw extruder with matched and staggered screw flights is analyzed using hydrodynamic lubrication theory. The flow analysis network (FAN) method of Tadmor et al. as modified by Szydlowski et al. [Int. Polym. Proc., 1, 207 (1987)] has been applied to determine pressure fields and velocity fields. The results show lower pressure development and greater back flows for staggered flight as opposed to matched flight tangential counter‐rotating twin screw extruders. The predictions agree well with experimental studies. Earlier theories of Kaplan and Tadmor, and Nichols overpredict the performance of matched flight twin screw machines.
Three‐body abrasion of fibrous polymer composites
Authors: Lhymn C. , Sliney H. , Dellacorte C.
Published: April 2003

The three‐body abrasive wear behavior of Acetal/20 wt % carbon or glass fiber composites has been investigated as a function of sliding velocity and normal load. The observed data have been explained analytically by a new abrasion model developed from the concepts of crack propagation, energy balance, and Newtonian mechanics.
Dry erosion of epoxy/rubber composites
Authors: Lhymn C. , Lhymn Y. , Richardson D. E.
Published: April 2003

The dry erosion behavior of epoxy/waste rubber composites has been investigated as a function of rubber content, air pressure (particle velocity), and impact angle. Morphological aspects have also been examined. The experimental data have been explained by means of an analytic equation derived from the crack propagation physics.
Effects of moisture on thermal and mechanical properties of nylon‐6,6
Authors: Pai Chih‐Chiang , Jeng Ru‐Jong , Grossman Steven J. , Huang Jan‐Chan
Published: April 2003

This study examined the moisture absorption and other properties of nylon‐6,6 as a function of mold temperature and annealing effects. Moisture absorption was seen to decrease as the temperature of molding and annealing increased with a predictable effect on mechanical and thermal properties: namely, increased moisture absorption indicated lower strength, stiffness, but higher ductility and impact resistance. Thermal analysis by differential scanning calorimetry indicated that with an increase in moisture absorption in the nylon‐6,6 a broadening of the melting endotherm is observed, suggesting a typical plasticizing effect of water on the nylon‐6,6. This study suggests that molding conditions of a nylon‐6,6 material may ultimately effect the levels of crystallinity in the final part and establish a relationship between the amount of absorbed water for a given nylon product and its processing variables.
Pressure effect in capillary rheometer
Authors: Huang Jan‐Chan , Shen Hsiao‐Fu
Published: April 2003

Steady shear viscosity data of a polypropylene resin were obtained at two elevated temperatures using an Instron capillary rheometer. When the pressure drop across the capillary is small, the hydrostatic pressure in the barrel is low, and the data from the capillary rheometer follow a linear Bagley plot. For long capillary and under a high hydrostatic pressure, the pressure drop increases at a faster rate than the length. A. pressure‐dependent viscosity function is proposed to explain the deviation and a new method to evaluate the pressure coefficient is introduced in this study. The results indicate that there is a significant increase in viscosity at a typical injection molding pressure, e.g., above 108 Pa.
Study of the compaction and sintering of two high‐performance thermoplastic polyimides
Authors: Throne James L.
Published: April 2003

Compression and sintering studies on powders of two thermoplastic high‐performance polyimides—Amoco Torlon polyamide‐imide and Mitsui Toatsu LaRC TPI polyimide—show that the partially crystalline polyimide, LaRC TPI, exhibits substantial pressure‐dependent cold flow, below its traditional melting point. Torlon PAI, a completely amorphous polymer, exhibits a more traditional pressure‐dependent compaction density.
Recent advances in ABS/PC blends
Authors: Huang Jan‐Chan , Wang Ming‐Song
Published: April 2003

ABS/PC blending systems are triple phase mixtures of SAN copolymer, polycarbonate and polybutadiene rubber. In this paper, the solubility parameter approach is used to calculate the optimum volume fractions of acrylonitrile component in the continuous phase of ABS, at which the best solubility parameters of the blends of ABS with other polymers were obtained. To obtain the best result, one needs to separate solubility parameter into three components: dispersive δd, dipolar δp, and hydrogen bonding δh. The thermal, mechanical, and rheological, morphological characteristics and weathering as well as miscellaneous properties are reviewed.