bluuebunny/crossref_metadata_2025_split huggingface dataset:
35 Years of Studies of Mixing of Rubber and Viscoelasticity
Authors: Nakajima N. 
Published: December 2013

Abstract
This paper provides a scientific treatment for mixing of rubber with reinforcing fillers. The primary attention is given to the viscoelastic nature of rubber. It is addressed to the practitioners of rubber processing, who have hands-on experience but lack familiarity with viscoelasticity. In the first part we provide a sketch of the major events: (1) polymerization, (2) resulting molecular architecture, (3) mechanical property of gum rubber, (4) mill processability, (5) processing with the internal mixer, and (6) compounding rubber with carbon black. The focal point of this paper is to relate the mill processability to the elongation and failure behavior of gum rubber. Viscous and elastic contributions to this relation are described. This relation provides the starting point for introducing scientific treatment for rubber mixing. Mechanisms of incorporation and dispersion of carbon black are also discussed. The presentation follows in an order of description on the behavior of gum rubber, that of carbon black, the interaction between rubber and carbon black, and the interaction between the material and the internal mixer.
In the second part a method of constructing viscoelastic master-curves from the tensile stress-strain data is presented. Such a master curve serves as a useful means of characterizing gum rubber in relating polymerization, resulting molecular architecture and processability. The milling and mixing of rubber with filler are achieved with fracture; the consequence of fracture is a generation of supermolecular flow units. The mechanism of fracture involves the pull out of chain ends through entanglements. The high concentration of the chain ends on the surface gives a tacky appearance to mixed compounds.
Morphology and Oxygen Barrier Properties of LDPE/EVOH Blends
Authors: Lee S.-Y. , Kim S.-C. 
Published: December 2013

Abstract
The morphology of the dispersed phase in immiscible polymer blends can have a significant effect on the final may be omitted physical properties. Laminar dispersion of an ethylene vinyl alcohol copolymer (EVOH) with high oxygen barrier properties was obtained in the matrix of low density polyethylene (LDPE) when extruded through an annular blown film die. A large range of morphology was observed and indicated that the main factors determining the morphology of the blends were the composition, the viscosity ratio of the components, the processing conditions, and the elongational fields at the exit of the die. Increasing amount of EVOH (from 5 to 20 vol %) resulted in increasing number of stacked layers. Highly elongated laminar structure was formed when the viscosity ratio (ηd(EVOH)/ηm
(LDPE)) was close to one and slightly lower. Large predeformed domains in the extruder outlet (before drawing and blowing) with short residence time under high screw rpm and lower viscosity ratio in the die temperature favored the formation of well-developed laminar structure. Oxygen permeation tests have shown high barrier effects due to the formation of the laminar dispersion which acted as barriers to the permeant molecules by providing a long tortuous path.
Viscous-Elastic Effects in a PA 6 Melt – Cause of Unevennesses in Melt-Spun Yarns**
Authors: Beyreuther R. 
Published: December 2013

Abstract
The paper deals with dynamic investigations for qualitative and quantitative estimation of the transition behaviour of a PA 6 melt spin equipment in the velocity range of 2 500 to 4 000 m/min. On-line measured time functions of yarn tensile force, yarn fineness and yarn tension, which are caused by determined spinning pump revolution number changes, have been evaluated to estimate the length of disturbed yarn with changed properties. Between spinning pump disturbances and the resulting yarn quality disturbances the delay time constant could be estimated with a typical size of about 1 s. Some hundred meter of yarn are disturbed in their properties during such a transition process. The main cause for the delayed cause-effect-transition could be found in the compression modulus of the melt between the spinning pump and the spinneret. The described dynamic step investigations permit to use a spinning equipment as a measuring system to estimate the compression modulus of melt spinnable polymers.
The Crystallinity of PVC and its Effect on Physical Properties**
Authors: Bao Y. , Weng Z. , Huang Z. , Pan Z. 
Published: December 2013

Abstract
Differential scanning calorimetry (DSC) was used to investigate the crystallinity of crude PVC powders and annealed PVC compounds. Crude PVC powder exhibited a broad crystallite fusion endotherm ranged from 110°C to 220°C. High degree of polymerization of PVC showed high degree of crystallinity both for powder and annealed sample under the same annealing conditions. Annealing conditions (time and temperature) had large effects on recrystallization behavior of PVC. The crystallinity of PVC decreased with increasing of DOP plasticizer content in PVC compounds, and lead to decrease of modulus and increase of average molecular weight between physical crosslinks.
Blend Morphology of Linear Low Density Polyethylene and Polystyrene in a Non-Intermeshing Twin Screw Extruder
Authors: Yang L.-Y. , Smith T. G. , Bigio D. 
Published: December 2013

Abstract
Morphology development was investigated during blending of linear low density polyethylene (LLDPE) and polystyrene (PS) (the minor phase) in a tangential counter-rotating twin screw extruder, with and without the use of 5 wt.-% Kraton styrene-ethylene/butylene-styrene (SEBS) triblock copolymers as compatibilizing agents. Dispersive mixing in the Non-Intermeshing Twin Screw Extruder (NITSE) is improved with an increase of percent drag flow up to 50 %; the screws configuration includes reverse flight elements and/or cylinders. Experiments have indicated that the combined effect of the reverse flight elements and cylinders increases the reduction rate of droplets due to a longer time in the feed screw where the most significant changes of phase morphology occur. Screw stagger has been shown to have a minor effect on the phase scale of the final dispersion. The more significant reduction of the phase scale is achieved by increasing screw speed under constant flow conditions.
Numerical Analysis of Cooling Air Systems in Film Blowing
Authors: Wolf D. , Feron B. , Wortberg J. 
Published: December 2013

Abstract
Air rings, used today in film blowing systems, have been developed down the years through trial and error experiments. They represent the limiting factor concerning the efficiency of film blowing lines with respect to throughput and take-off speed. Numerical simulation of the cooling process in film blowing provides a tool for the design and optimization of future cooling systems. Individual process and geometric parameters can be changed interactively with the effects on flow and heat transfer processes being analysed and applied to similar situations. The knowledge acquired regarding the physical interactions in the cooling of blown film makes a targeted optimization possible. The purpose of this paper is to present the foundamentals for calculating turbulent air flows in blown film extrusion and, additionally, a model for complete FE-simulation of the flow and heat transfer processes. Furthermore, the achieved simulation results will be discussed.
Effect of Compounding Conditions on Mechanical Properties of Glass Fiber-Reinforced Polyamide-6
Authors: Nagae S. , Nagura K. , Yamagiwa N. , Yamane Y. , Miyake K. , Inoue K. 
Published: December 2013

Abstract
Glass fiber-reinforced polyamide-6 (GFPA-6) was compounded using a HYPERKTX46 twin screw extruder with three different types of screw segments (rotor segments, kneading disc segments and turbine segments). Based on the ‘neural network’ regression analysis, we investigated the effects of compounding conditions, such as screw configurations, screw rotation speed, and production rate on mechanical properties, such as tensile, flexural and impact strength of GFPA-6. It was found that the mechanical properties of GFPA-6 changed in different ways with compounding conditions (screw rotation speed and production rate), depending on the type of screw segments. It was also found that the rotor segment exhibited good mechanical properties in wider ranges of compounding conditions than the kneading disc segment and the turbine segment, probably due to its mild and uniform mixing capability.
Injection Molding of LDPE/BaSO4 Blends
Authors: Shearer G. , Tzoganakis C. , Penlidis A. , Rempel G. L. 
Published: December 2013

Abstract
The injection mold filling behavior of a blend of low density polyethylene (LDPE) and barium sulphate (BaSO4) was studied experimentally and compared with that of pure LDPE. The method of short shots was used to analyze the mold filling behavior. An experimental study using a full factorial design was implemented with the following factors: mold temperature, injection speed and injection time. Experimental results and computer simulation predictions of the mold filling stage were found to be in acceptable agreement. The produced short shots with the LDPE/BaSO4 blend have significantly lower percentages of volume filled than those of the corresponding short shots with the pure LDPE. The increase in the melt viscosity and density of the polymer resin with the addition of BaSO4 cannot be neglected when producing injection molded articles with LDPE/BaSO4 blends. To study the deviations between the experimental results and the computer simulation predictions, a factorial numerical study was completed. The results show that the simulation predictions are significantly affected by the accuracy of the polymer material properties.
Towards a 3-D Finite Element Model for the Gas-Assisted Injection Moulding Process
Authors: Haagh G. A. A. V. , Zuidema H. , van de Vosse F. N. , Peters G. W. M. , Meijer H. E. H. 
Published: December 2013

Abstract
The Gas-Assisted Injection Moulding process (GAIM) offers a number of advantages, which are almost without exception related to the negligible pressure drop in the gas core of the moulded product. Accurate prediction of the gas distribution inside GAIM products is, however, still a major problem to be solved. As gas penetration is governed by three-dimensional phenomena, one has to resort to numerical simulations to analyse the process. Therefore, a numerical model for GAIM simulations has been developed, based on a physical, rather than on an empirical approach. The model employs a pseudo-concentration method in order to avoid elaborate three-dimensional remeshing, and has been implemented in a finite element program.
Simulation results for two-dimensional test cases representing typical GAIM situations prove that the model covers most of the important aspects of gas injection. A pilot simulation for a simple three-dimensional mould demonstrates that the model is able to deal with three-dimensional GAIM. Further refinement of the model will mainly concern the implementation of faster and less memory-consuming solution methods.
Melt Temperatures and Residence Times in an Extruder by Infrared Spectroscopy
Authors: Nietsch T. , Cassagnau P. , Michel A. 
Published: December 2013

Abstract
This article presents melt temperature measurements with an infrared thermometer during extrusion and investigates the influence by the surface emissivity and the rotating screw. This influence can be used for on line residence time measurements in the extruder line, to measure the number of revolutions of the screw, and to measure both the surface temperature and the bulk's temperature.
The results show that colouring the PE with a high emisffisivity tracer allows us to measure the melt's surface temperature and minimise the influence of the rotating screw. Its influence is weaker in complete filled section as in partial filled sections of the extruder and the mean bulk's temperature is measured when the emissivity is lower than one.
Furthermore it is shown that it is possible to measure the residence time distribution on line with an infrared thermometer, by taking advantage of its sensibility on a changing surface emissivity. Measurements with classical methods shows the same residence time distribution as obtained with the infrared spectroscopy. The advantage of this method is its wide range of applications, such like as the use in pressure zones, for a wide range of temperature and to measure on line the local residence time distribution all along the screw.
Distributed Crystallinity Control during Cast Film Extrusion
Authors: Leephakpreeda T. , Batur C. 
Published: December 2013

Abstract
The properties of polymer material can be shaped by crystallinity distribution during the film extrusion process. This paper addresses the implementation of design sensitivity analysis to determine the process inputs which can generate the desired crystallinity distribution. To achieve such a goal, the performance index is defined in terms of the difference between the desired and the actual crystallinity distributions. The sensitivity of the performance index to process inputs is determined in order to update these process inputs in every iteration of optimization. The design sensitivity analysis presented here allows a systematic movement through the search space to reach a sub-optimal set of process inputs. The simulation results show that the proposed methodology can determine the process inputs in order to generate the crystallinity distribution close to the desired one.
The Occurrence of Flow Marks during Injection Molding of Linear Polyethylene
Authors: Heuzey M. C. , Dealy J. M. , Gao D. M. , Garcia-Rejon A. 
Published: December 2013

Abstract
Injection molded parts often show several types of surface defect. It has been hypothesized that wall slip is associated with some of these defects. Wall slip of molten plastics has been observed above a certain critical shear stress in rheological measurements. The objectives of the proposed research were to analyze the occurrence of flow marks during the injection molding of linear polyethylene and evaluate its possible relation to wall slip. Various variables were studied in terms of their influence on flow mark formation: mold thickness, mold temperature, melt temperature, gate, injection speed and TeflonTM and silicone oil coatings. It was found that injection speed is the controlling factor for the generation of flow marks during injection molding of the linear polyethylenes studied. Since one of the resin studied had shown no tendency to slip in capillary flow experiments, and since a Teflon TM coating on the mold walls did not affect the occurrence of flow marks, we conclude that there is no relationship between wall slip and the generation of flow marks. Microscopic observation of molded surfaces suggests instead that flow marks result from the filamentaton and stretching of semi-solidified material in the neighborhood of the three-phase contact line.
Modeling Solids Conveying in Polymer Extruders
Authors: Yamamuro J. A. , Penumadu D. , Campbell A. 
Published: December 2013

Abstract
Modeling solids conveyance in a polymer extruder is difficult because it is a highly complex process. The solids are subjected to pressure and temperature gradients from the hopper through a heated section, where it is melted into a liquid over a finite distance. The polymer material possesses shear strength, which causes an anisotropic stress distribution to exist between the down channel pressure and the normal stresses on the flights, barrel and core. A new formulation incorporating anisotropic stress states into an isotropic model is presented. Assumptions regarding the direction of the driving force applied by the screw have been examined in addition to coupling its direction with the orientation of the barrel friction force. These assumptions allow the new model to provide increased nonlinearity and flexibility to accurately predict extruder output over wide variations with discharge pressure. A new parameter, the skew angle, is introduced in the proposed model. Predictions of extruder output for varying discharge pressures and barrel temperatures show excellent agreement with experimental data.
Pumping Characteristics of an Intermeshing Co-rotating Twin Screw Extruder
Authors: Wang N. H. , Sakai T. , Hashimoto N. 
Published: December 2013

Abstract
The pumping characteristics of several types of screw elements for an intermeshing co-rotating twin screw extruder (ICoTSE) were experimentally studied using molten polystyrene (PS) as a typical non-Newtonian fluid in “LABOTEX30α”. Here, the throughput was regarded as the remainder of drag flow minus pressure flow, based on the previous theoretical and experimental studies with regard to either single or twin-screw extruders. Therefore, the relationship between the throughput and the pressure gradient for a given screw geometry was approximately expressed as a linear dimensionless relation containing two so-called pumping-characteristic parameters which depend on the element geometry and degree of departure of the used fluid from the Newtonian fluid.
The pumping-characteristic parameters for two right-hand flighted screw elements (RF) with leads of 0.938D and 0.703D, a neutral kneading disk (NK) and a blister ring (BR) were experimentally determined, and the RF with a lead of 0.938D was taken as an example to observe the effect of the clearance between it and the barrel wall on its pumping-characteristic. The results show that the linear relationship between the dimensionless throughput and the dimensionless pressure gradient for each type of the screw elements used here is a good approximation, and the clearance in the range used here greatly affects the pumping characteristic of the RF.
Moreover, the degree of filling and the pressure profile in two kinds of screw configurations used for water-injection foaming devolatilization, which consist of elements with different diameters but with the same dimensionless geometry as those used in this work, were predicted and discussed by using the determined pumping-characteristic parameters under the conditions of given throughput of molten PS and screw speed.
Sintering Rheology of Semi-Crystalline Polymers
Authors: Liu S.-J. 
Published: December 2013

Abstract
The focus of this study is to investigate the sintering mechanism of polyethylene. Experiments were conducted to observe the high temperature sintering behaviors of low density polyethylene (LDPE) and linear low density polyethylene (LLDPE). It was found that the sintering of polyethylene follows Frenke's model and is basically a Newtonian viscous flow. The sintering rate decreases as the viscosity of the resin increases. By increasing the temperature, one can shorten the time needed to complete the coalescence process. Experimental investigation will provide an improved understanding of the sintering of semi-crystalline polymers.
Interactions in Binary and Ternary Polyolefin Blends
Authors: Hénaut I. , Vergnes B. , Agassant J. F. , Haudin J. M. 
Published: December 2013

Abstract
A way for the recovery of plastic waste is the reprocessing. As they cannot be easily separated, the reprocessing of polyolefins appears as a special case of the processing of polymer blends. In order to understand the basic phenomena involved in these systems, binary and ternary blends are prepared from a high density polyethylene, a linear low density polyethylene, and a random ethylene-propylene copolymer. In a first step, the interactions between the different polyolefins are characterized in laboratory experiments (differential scanning calorimetry, optical microscopy, small-angle light scattering, wide-angle X-ray diffraction, mechanical properties). Then, it is shown that the original poor mechanical properties of the blends can be largely improved by optimizing the processing conditions. Finally, an extrapolation of these results to real plastic waste is presented.
Crystal Orientation in Injection Moldings of Talc-filled Polyolefins
Authors: Fujiyama M. 
Published: December 2013

Abstract
Crystal orientation states in injection moldings of talc-filled polyolefins have been studied. Talc-filled polypropylene injection moldings show an unusual crystal orientation, in which the plate planes of talc particles are aligned parallel to the molding surface, the c- and a*-axes of polypropylene crystals are bimodally oriented to the flow direction, and the b-axes are oriented to the thickness direction. In injection moldings of talc-filled high density polyethylene and polybutene-1, although talc particles are aligned parallel to the molding surface, polymer crystals do not show any unusual orientation. Only talc-filled polypropylene injection moldings show the unusual crystal orientation.
Stress-Strain and Volume Change Characteristics of an Assemblage of Polymer Pellets
Authors: Penumadu D. , Yamamuro J. A. , Abrantes A. E. , Campbell G. A. 
Published: December 2013

Abstract
A series of experiments were performed on an assembly of four commercially available polymer pellets at room temperature. An automated deformation controlled triaxial testing system was used for the entire testing program. Lubricated end platens were used to assure uniform strain conditions during the application of compressive loading on the confined cylindrical specimen of a given polymer pellet type at a target bulk density. The test results in terms of the deviator stress-strain and volume change characteristics of polymer pellets were obtained for use in the modeling and analysis of solids conveying in plasticating screw extruders. Testing procedures are described that can be used routinely to obtain the strength and deformation behavior of an assemblage polymer pellets. The deviator stress-axial strain and volumetric strain-axial strain curves are presented for four confining stress levels (l00, 200, 300 and 400 k Pa) for these materials using both dry and saturated specimens. The water saturated specimens were used in parallel for obtaining reliable measurements of the volumetric strain variation during the application of deviator stress. The effect of using water as the pore fluid on the mechanical behavior was also discussed. The angles of internal friction of these four polymeric materials were determined and the use of Mohr-Coulomb failure criteria was evaluated. These confining pressure dependent friction angles are compared with the angle of repose measurements. The stress transfer coefficients as a function of wall friction for the potential states of confinement of these polymer pellets in the solids conveying portion of an extruder are also summarized.
Consistency and Flexibility of Multi Cavity Melt Control
Authors: Kapoor D. , Kazmer D. 
Published: December 2013

Abstract
The quality of injection moulded products is determined by a complex coupling between polymer properties, mould geometry, and process dynamics. To increase the flexibility and consistency of the injection moulding process, a method was devised to simultaneously control cavity pressure at multiple locations in a mould. This control was achieved by installing multiple dynamic valve stems into the feed system of a hot runner manifold, each of which can control polymer flow. This system was used in a commercial application with four gates to deliver consistent product quality and provide manufacturing-stage flexibility. Across all eleven measured dimensions, the process capability index Cp increased between 50 and 400%. Also, multiple dimensions could be independently and simultaneously adjusted by locally controlling material shrinkage.
Commentary on "Graphite and its hidden superconductivity"
Authors: Forgan E. M. 
Published: December 2013

A Commentary on the paper by P. Esquinazi [Pap. Phys. 5, 050007 (2013)]. The author of the paper offers a Reply.Received: 10 October 2013,, Accepted: 4 November 2013; Edited by: S. A. Grigera; DOI: http://dx.doi.org/10.4279/PIP.050008