bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Mold Temperature on Structure and Property Variations of PBT Injection Moldings in the Thickness Direction
Authors: Shibaya M. , Ishihara H. , Yamashita K. , Yoshihara N. , Nonomura C. 
Published: December 2013

Abstract
During injection molding process, the surface of flowing resin in contact with the mold surface is cooled first followed by the cooling of inner part. This results in the variation of microstructure in moldings through the thickness direction. It has been reported that these phenomena result in the layered structure of injection moldings. Particularly, because of the rapid rate of crystallization, PBT injection moldings have well-defined skin and core layers. The purpose of this study is to investigate the effect of mold temperature on the development of structure and property variations of PBT injection moldings in the thickness direction. Tensile tests were performed using dumbbell specimens that were stamped out from the sliced specimens of moldings. Neck phenomenon occurred irrespective of mold temperature and distance from the surface of moldings. The start point of neck propagation shifted to higher strain with increasing distance from the surface. Tensile modulus increased with increasing distance from the surface. In order to discuss these results from a structural viewpoint, the microstructure of each layer was evaluated by density, wide-angle X-ray diffraction and Fourier transform infrared absorption measurements. The delay in necking start points with increasing distance from the surface is due to the higher crystallinity of the inner layer compared to that of the layer near the surface. Two crystal forms of PBT (α- and β-forms) were developed in injection moldings. The region near the surface, where content of α-form is larger than that of β-form, becomes thinner with increasing mold temperature. It is known that the crystal modulus of α-form is lower than that of β-form. Therefore the portion of moldings with lower tensile modulus and yield strength becomes smaller. It is suggested that the border between the skin and core layers, where tensile property changes, shifts to the surface of PBT injection moldings as mold temperature increases.
Study on Viscoelastic Behavior and Extrusion Blow Molding Processability of PP/PE Blends
Authors: Shiromoto S. , Koyama K. 
Published: December 2013

Abstract
In this study, extrusion blow molding processability of polypropylene/polyethylene (PP/PE) blends was related to their viscoelastic behavior and morphology under shear flow. The propylene block-copolymer (PP-B) and blends comprising the PP-B and the linear low-density polyethylene (PE), weight fraction of the PE (ϕPE) was up to 20 wt.%, were mainly used for this study. Viscoelastic behavior under shear flow and swelling ratio of the extruded strands were measured by using a capillary type rheometer. Morphology of the strands was observed by TEM. In case of the PP-B, swelling ratio highly depended on shear rate. Coarse aggregated droplets were observed irrespective of shear rate under the measurement. The droplets were ethylene-propylene copolymers (EP) included in the PP-B aggregated at conversing section of the capillary. However, in case of the PP-B/PE blends, swelling ratio showed lower dependence on shear rate as the ϕPE was higher. When the shear rate was low, large droplets were observed and they were highly deformed in the flow direction. On the other hand, when shear rate was high, the droplets were smaller and showed no deformation in the flow direction because the droplets were broken up due to occurrence of high shear stress. Wall thickness of blow molded bottles produced from the PP-B/PE blends was not affected by the throughput rate. It was proportional to the die-core gap. On the other hand, wall thickness of bottles of the PP-B depended on the throughput rate and it was not proportional to the die-core gap. These results suggest that extrusion blow molding processability of polymer blends is good when the dependence of swelling ratio on shear rate is low.
Experiments on Characteristic Deformation and Breakup Behaviors of an Immiscible Drop in a Screw Channel Flow
Authors: Jun H. S. , Hwang W. R. , Kwon T. H. 
Published: December 2013

Abstract
Deformation and breakup mechanisms of an immiscible drop were investigated experimentally in a screw channel flow, which mimics the flow in the metering section of the single screw extruder. It was observed that the deformation/breakup mechanisms are far distinct from the well-known routes for the linear flow, mainly because of the complex flow history that can be characterized by the repetition of strong/weak shear, the continuously varying shear direction and the acceleration/deceleration. The experimental observations include: comet-like thread formation with the large bulbous head and the long narrow tail; the initiation of the breakup at the entrance of the low-shear zone; breakup by asymmetric end pinching; breakup by the growth of the capillary wave, propagating from the tail toward the head; monotonically decreasing droplet size distribution from the head to tail. The mechanism for the comet-like thread formation has been investigated by using the numerically obtained flow field.
Tensile and Flexural Properties of β-Nucleated Polypropylenes
Authors: Obadal M. , Cermák R. , Habrová V. , Stoklasa K. , Šimoník J. 
Published: December 2013

Abstract
Resuming our previous work on β-nucleated polypropylenes, namely on their impact strength, our present work directs attention towards a flexural and tensile behavior of β-nucleated polypropylenes (β-iPP). For the purposes of this work, commercially available isotactic polypropylene was modified using various amounts of a specific nucleating agent based on N, N′-dicyclohexylnaphtalene-2,6-dicarboxamide (NU100). From the prepared blends test specimens were prepared by injection molding. Structural characterization (crystallinity and the content of β-phase) was carried out by X-ray diffractometry. A multipurpose mechanical property tester was used for determination of tensile and flexural properties. It was found that β-phase content decreased both tensile and flexural strength; on the other hand, the presence of β-phase dramatically raised cold drawability of the injection-molded specimens; addition of 0.03 wt.% of NU100 in the injection-molded parts led to a more than 800 % increase of the draw ratio of specimens tested at the testing speed of 100 mm/min. Furthermore, tensile testing carried out using various strain speeds (10 and 100 mm/min) revealed that higher ductility of the material containing β-phase is particularly pronounced by faster deformation processes, such as fast drawing or impact load.
Non-linear Crystalline Spherulitic Growth Behavior for LLDPE
Authors: Kamal M. R. , Feng L. 
Published: December 2013

Abstract
Nonlinear growth behavior was observed in two crystallization regimes, depending on the temperature. Non-linearity may be explained by the reduction of the concentration of crystallizable ethylene sequences (CES) in the melt phase. In the two regimes, the concentration of uncrystallizable ethylene sequences (UCES) increases, as the crystallization time increases, because UCES are continuously excluded from the crystal lattice into the melt phase. An empirical equation is proposed to describe the melting temperature of the crystal stem with the maximum possible length, T

C, n
*

m
, in nonlinear growth processes, assuming that the diffusion layer is negligible. A modified form of the Hoffman-Lauritzen equation (MHL) describes well the crystallization growth kinetics of LLDPE spherulites in the non-linear growth region.
Studies on NBR-ZDMA-OMMT Nanocomposites Prepared by Reactive Mixing Intercalation Method
Authors: Liu L. , Luo Y. , Jia D. , Guo B. 
Published: December 2013

Abstract
Two kinds of nanocomposites of nitrile-butadiene rubber (NBR), zinc methacrylate (ZDMA) and organomontmorillonite (OMMT), NBR-ZDMA-HMMTand NBR-ZDMA-USMMT, were prepared by the reactive mixing intercalation method with ZDMA and two kinds of organomontmorillonite, hexadecyltrimethylammonium bromide modified montmorillonite (HMMT) and unsaturated chemical modified montmorillonite (USMMT). The structure and properties of the nanocomposites were investigated by X-ray diffraction, transmission electron microscopy, differential scanning calorimetry and determination of crosslinking density and mechanical properties. The results showed that the interlayer galleries of HMMT and USMMT were enlarged as ZDMA polymerized in situ in rubber matrix and between the interlayer of the silicates. The layered silicates were dispersed disorderly in rubber matrix at a nanometer level. The crosslinking density of the NBR vulcanizates was increased by the addition of ZDMA and HMMT or USMMT. The glass transition temperatures of the NBR-ZDMA-OMMT nanocomposites were higher than that of the neat NBR. The mechanical properties of the NBR-ZDMA-HMMTand NBR-ZDMA-USMMT nanocomposites are remarkably superior to those of the neat NBR vulcanizate.
Investigation of the Cooling Jets Used in the Blown Film Process
Authors: Gao N. , Li S. , Ewing D. 
Published: December 2013

Abstract
Measurements were performed to characterize the development of the cooling jets produced by a typical dual-lip air ring used in the blown film manufacturing process. The distribution of the pressure on the bubble surface and the velocity field in the region above the forming cone were measured for a rigid model bubble with a blow-up ratio of 2.5. The measurements indicated that the development of the flow below the top of the forming cone in the air ring could be divided into two regions separated by local maxima in the static and fluctuating pressure. These maxima seemed to be associated with the location where the lower jet attached to the bubble surface. There was a region of negative gauge pressure on the bubble surface below the forming cone that should act to stabilize the bubble against the forming cone in practical applications. Above the forming cone, the lower jet was initially decelerated and then entrained into the upper jet. The upper jet then attached to the bubble surface and finally the flow recovered to a wall jet along the bubble surface. The profiles of the static and fluctuating pressure in the first and third regions above the forming cone collapsed reasonably well when they were scaled using the velocity of the lower jet and the velocity of the upper jet, respectively. The magnitude of the local maxima in the static and fluctuating pressure where the upper jet attached to the bubble depended on the upper jet velocity and the ratio of the upper and lower jet velocities.
Processing-induced Properties in Glassy Polymers
Authors: Govaert L. E. , Engels T. A. P. , Klompen E. T. J. , Peters G. W. M. , Meijer H. E. H. 
Published: December 2013

AbstractA new method is employed to directly predict the development of yield stress distributions in injection molded products of glassy polymers. The approach is based on the results of a study on the temperature dependence of the evolution of yield stress during annealing of polycarbonate below Tg. In combination with the process-related thermal history, derived from numerical simulations of the injection molding process, an estimate of the yield stress distribution throughout a product can be obtained. Computed yield stresses of injection molded plates prove to be in excellent agreement with the experimental values, including their dependence on mold temperature and plate thickness.
Cast Film Extrusion
Authors: Agassant J. F. , Demay Y. , Sollogoub C. , Silagy D. 
Published: December 2013

Abstract
Cast film extrusion is a widely used technique to produce polymer films for packaging or coating applications. The final width of the film may be smaller than the initial die width (necking phenomenon) and therefore is the final film thickness larger than what one could expect. Moreover it is heterogeneous (in terms of showing a larger thickness along the borders, also called dog bone defect). Above a critical draw ratio between the chill roll and the die both width and thickness fluctuations are observed (Draw Resonance Instability). All these phenomena limit the productivity of the process.
This paper provides an overview of the processing and material parameters governing the development of these geometrical defects and instabilities. Numerical models capturing the main experimental features are proposed, allowing to investigate process modifications in order to limit the development of these defects.
Numerical Analysis of Rubber Moulding Using Finite Element Modelling
Authors: Hanspal N. S. , Nassehi V. , Ghoreishy M. H. R. 
Published: December 2013

Abstract
Finite element technique is used to model the free surface flow regime representing injection mould filling of elastomeric material such as rubber compounds. The most distinct feature of the constitutive behaviour of elastomers, is the influence of material elasticity on the elongation and shear deformation suffered by the fluid during flow. In the present study this feature has been tackled through the use of Criminale-Erickson-Fibley (CEF) model. A scheme based on the Volume of Fluid technique is developed for free surface tracking. The results represented in this paper have also been compared against the Phan-Thien/Tanner model and are shown to be in closer agreement with the theoretical expectations than those obtained by the P-T/T equation. The results prove the applicability of the developed model to industrially relevant situations.
Assessment of the Degree of Mixedness of Filled Polymers
Authors: Erol M. , Kalyon D. M. 
Published: December 2013

Abstract
For a given compounding application the selection of the type of processing equipment, the geometry and the operating conditions is always an important challenge. The outcome of this selection process significantly affects the economics of the process, as well as the microstructural distributions and hence the ultimate properties of the compound. Here mixing indices, defined on the basis of the statistics of the distributions of the concentrations of a plasticized elastomeric binder and graphite filler, were used to quantitatively characterize and compare the degree of mixedness of products of batch mixing, co-rotating and counter-rotating fully-intermeshing twin screw extrusion processes. Two separate experimental methods, involving the wide-angle x-ray diffraction and thermo gravimetric analyses, were used for the characterization of the mixing indices at two different scales of examination. The mixing indices were sensitive to changes in geometry and operating conditions. The resulting electrical properties of the conductive composite samples, mixed with either the batch or continuous, i. e., using either co-rotating or counter-rotating twin screw extrusion, correlated with their degree of mixedness. The presented methodologies should facilitate more accurate comparisons of the performances of different types of processors and better tailoring of the structure and ultimate properties of filled polymers.
Microcellular Injection Molding
Authors: Gong S. , Yuan M. , Chandra A. , Kharbas H. , Osorio A. , Turng L. S. 
Published: December 2013

Abstract
This paper reviews some of the recent developments of microcellular injection molding, which is capable of producing parts with excellent dimensional stability using lower injection pressure, shorter cycle time, and less material. Process conditions as well as nano/micro-fillers such as nanoclay and core–shell rubber have a strong influence on cell density and cell size, hence, the final material properties of the molded parts. The addition of nano/micro-fillers at optimum loading levels can generally facilitate the formation of microcellular plastics with higher cell density and smaller cell size leading to superior mechanical properties. The novel integration of a solid plastic surface with a microcellular plastic core via the co-injection molding technique has been investigated to achieve Class “A” surfaces and improved material performance. An improved mathematical model has been developed to simulate the cell growth behavior in the microcellular injection molding process.
Injection Moulding and Mechanical Properties of Recovered Polypropylene
Authors: Pisciotti F. , Boldizar A. , Rigdahl M. 
Published: December 2013

Abstract
This work is a part of a study aiming at assessing the processability of recovered polypropylene in relation to the mechanical and aesthetic performance of as-manufactured and heat aged mouldings. The effects of processing and heat ageing on the mechanical properties of injection-moulded recovered polypropylene were studied here. A similar grade of virgin polypropylene was used as a reference. Multipurpose test specimens were manufactured with a two-cavity mould, according to decoupled moulding procedures. The mouldings were aged at 100°C for 170 h and 340 h. The stiffness, the strength, the elongation at break and the Charpy impact resistance of as-moulded and heat-treated materials were investigated. The results show that the recovered polypropylene could be processed as the analogous virgin grade. Insignificant changes in the measured properties due to the different filling conditions were observed for each polypropylene used. The stiffness and strength of the recycled polypropylene was systematically 20% lower than that of the analogous virgin grade, whereas the impact resistance of the recycled grade was on average 40% higher than that for the virgin grade. There was no significant difference in the elongation at break of the two materials. After the short ageing period, an increase in stiffness and strength of the materials was observed, together with a sharp decrease in the elongation at break and a modest increase in the impact resistance. This was related to re-crystallisation. The long ageing period reduced the stiffness and strength of the materials but there was no significant change in the elongation at break or in the impact resistance.
Two Component Injection Molding of Phase Separating Blends
Authors: Keestra B. J. , Anderson P. D. , Meijer H. E. H. 
Published: December 2013

Abstract
A partially miscible polymer PMMA/SAN blend is used in two component injection molding to produce a sandwich structure with a heterogeneous skin layer. Two different strategies are explored to obtain the desired structure either via sequential injection molding or via the use of the fountain flow. Both cases are studied with scanning electron microscopy to visualize the structure in the skin layer. In addition, numerical modelling examples are presented to improve understanding of the morphologies that have been created with injection molding.
Inkjet Printing of Conductive and Resistive Coatings
Authors: López F. Varela , Diez A. , Odriozola A. 
Published: December 2013

Abstract
Coating of functional materials is the basis of many electronic device manufacturing processes. Screen printing, roll coating and other methods have been used for decades, permitting low cost, high production rates of Printed Circuit Boards (PCBs), where conductive pathways are printed before components are integrated. Nowadays, the PCB industry in developed countries is suffering a revision of all manufacturing processes, to cope with severe market constraints: short runs and fast time-to-market. Inkjet technology has arrived to complement the traditional, analogical production, with new tools that makes possible to produce goods with great versatility.
In this work we will state the problem of inkjet printing functional materials in the frame of PCB manufacturing. The use of numerical methods to asset the formation of conductive pathlines using digital techniques will be presented. Also, the use of resistive and dielectric inks will be discussed.
The Characteristic Behaviour of the Stretch-Orientation Zone during High-Speed PET Spinning**
Authors: Wu Jialin , Guan Diaosheng , Quian Baojun 
Published: December 2013

Abstract
A theory is proposed to separate the on-line stress in the stretch-orientation zone during high speed PET spinning into two parts: the thermodynamically equilibrium or quasi-equilibrium stress associated with rubber elasticity and the non-equilibrium driving stress, which leads to coordinated orientation of the macromolecular chains. Precise and simultaneous measurements of the online spinning parameters at five spinning speeds, ranging from 2200 to 4200 m/min, were conducted. A physical model consisting of a dashpot placed in parallel with a Gaussian network was found to describe well the behaviour of the stretch-orientation zone of high speed PET spinning.
Present and Future Trends in Polymer Blends Technology**
Authors: Utracki L.A. 
Published: December 2013

Abstract
The plastics industry shows the highest growth rate of all industrial materials. Within this group the engineering resins (ER) are developing fastest. The review focuses on polymer alloys and blends (FAB) of ER. After the discussion of the economic aspect of PAB the patent literature is briefly reviewed and illustrated by a summary of selected, recent patents on polyphenylene ether blends. There is little doubt that the future trend in PAB technology will require control of morphology, especially in most common multiphase systems. For this reason the last part of the article summarizes the available information of criteria for rheological and thermodynamic control of morphology. The review ends with a brief description of the methods and equipment used by industry to compound and form the PAB.
Simulation of Balancing Multi-Cavity Molds
Authors: Ghoneim H. 
Published: December 2013

Abstract
A finite element program is developed for simulating the non-isothermal flow of non-Newtonian liquids in a multi-cavity mold with convergent runners and gates of any arbitrary cross-sectional shape. The program is used to investigate the problem of balancing multi-cavity molds. Results of simulating an actual mold filling show that balancing can be achieved by using a straight runner together with convergent gates having successively increasing angles of convergence. In addition, a strategy for approximating those angles of convergence is suggested.
Wide Angle X-ray Line Profile Analysis of Post-neck Drawn Filaments of HDPE
Authors: Cakmak M. , Clark E. S. 
Published: December 2013

Abstract
Wide angle X-ray diffraction technique was used to characterize a series of post-neck drawn high density polyethylene filaments which were stretched by a two-stage drawing process. The first stage of this drawing process utilizes 100%/min draw rate until the natural draw ratio of 8–10 × ist attained. In the second stage, the fully necked filament is re-clamped and further stretched at lower stretch rate (1%/min) upto the desired stretch ratio. Wide angle X-ray diffraction data were analyzed using the Warren-Averbach fourier technique. This analysis showed that number average crystallite size increase with increasing draw ratio. In addition, the root mean square strains (∊2)½ in the crystals decreased with increasing draw ratio upto the draw ratio of 25 then showed an increase with further increase of draw ratio.